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Papers by Victor Torres

International …, 2007

Stable coatings of spherical poly(vinyl)-N-pyrrolidone (PVP)-coated silver nanoparticle layers we... more Stable coatings of spherical poly(vinyl)-N-pyrrolidone (PVP)-coated silver nanoparticle layers were obtained using spin coating and rapid thermal processing of PVP/Ag nanoparticle composite thin films on optical glass substrates and this simple method extended to the deposition on optical substrates of solid spheres encapsulating silver nanoshapes, by slow heating of the solution of Ag-encapsulating nanospheres to temperatures above 120 ºC.

Quick Search: All GSW Journals, GSW + GeoRef. advanced search. ...

VacA is a secreted toxin that plays a role in Helicobacter pylori colonization of the stomach and... more VacA is a secreted toxin that plays a role in Helicobacter pylori colonization of the stomach and may contribute to the pathogenesis of peptic ulcer disease and gastric cancer. In this study, we analyzed a library of plasmids expressing randomly mutated forms of recombinant VacA and identified 10 mutant VacA proteins that lacked vacuolating cytotoxic activity when added to HeLa cells. The mutations included six single amino acid substitutions within an amino-terminal hydrophobic region and four substitutions outside the aminoterminal hydrophobic region. All 10 mutations mapped within the p33 domain of VacA. By introducing mutations into the H. pylori chromosomal vacA gene, we showed that secreted mutant toxins containing V21L, S25L, G121R, or S246L mutations bound to cells and were internalized but had defects in vacuolating activity. In planar lipid bilayer and membrane depolarization assays, VacA proteins containing V21L and S25L mutations were defective in formation of anion-selective membrane channels, whereas proteins containing G121R or S246L mutations retained channel-forming capacity. These are the first point mutations outside the amino-terminal hydrophobic region that are known to abrogate vacuolating toxin activity. In addition, these are the first examples of mutant VacA proteins that have defects in vacuolating activity despite exhibiting channel activities similar to those of wild-type VacA.

Waddell, JE and AM …, 2008

Guam GROUP NUMBER OF SPECIES SOURCES Seagrasses 3 Lobban and Tsuda, 2003 Benthic Macroalgae 237 *... more Guam GROUP NUMBER OF SPECIES SOURCES Seagrasses 3 Lobban and Tsuda, 2003 Benthic Macroalgae 237 * Number of species is for the entire Mariana Archipelago. The actual number for Guam may be lower. molluscs, and marine algae are also eaten locally. In addition to the cash and subsistence value of edible fish and invertebrates, reef-related fisheries are culturally important as family and group fishing is a common activity in Guam's coastal waters. Over 10% of Guam's coastline has been set aside in five marine preserves: Tumon Bay, Piti Bomb Holes, Sasa Bay, Achang Reef Flat, and Pati Point. The preserves were established in 1997 as a response to decreasing reef fish stocks, but were not fully enforced until 2001. Fishing activity is restricted in the preserves with limited cultural take permitted in three of the five areas. The preserves are complemented by the War in the Pacific National Historical Park, Ritidian National Wildlife Refuge, Guam Territorial Seashore Park, Orote Penisula Ecological Reserve Area (ERA), and Haputo ERA. While management practices are enforced in the five marine preserves, there is currently limited management and enforcement in the other areas. The health of Guam's coral reefs varies considerably, depending on a variety of factors including geology, human population density, level of coastal development, level and types of uses of marine resources, oceanic circulation patterns, and frequency of natural disturbances, such as typhoons and earthquakes. Many of Guam's reefs have declined in health over the past 40 years. The average live coral cover on forereef slopes was approximately 50% in the 1960s (Randall, 1971), but dwindled to less than 25% live coral cover by the 1990s with only a few having over 50% live cover (Birkeland, 1997). In the past, however, Guam's reefs have recovered after drastic declines. For example, an outbreak of the crown-of-thorns starfish (COTS) in the early 1970s reduced coral cover in some areas from 50-60% to less than 1%. Twelve years later, greater than 60% live coral cover was recorded in these areas (Colgan, 1987). A more distressing indicator of the health of Guam's coral reefs is the marked decrease in rates of coral recruitment. In 1979, Birkeland et al. (1982) obtained 0.53 coral recruits per plexiglass fouling panel. The use of similar materials and experimental design in 1989 and 1992 resulted in just 0.004 and 0.009 coral recruits per plexiglass fouling plates, respectively (Birkeland, 1997). Sidebar The State of Coral Reef Ecosystems of Guam ENVIRONMENTAL AND ANTHROPOGENIC STRESSORS Climate Change and Coral Bleaching Large-scale coral bleaching events and associated coral mortality are not common on Guam. Since the establishment of the University of Guam Marine Laboratory (UOGML) in 1970, there have been only two recorded large-scale bleaching events. In 1994, 68% of surveyed taxa bleached on Guam (Paulay and Benayahu, 1999). The event was characterized by considerable inter-species variation in bleaching response and little mortality, and did not appear to be associated with above-average SSTs. In 1996, about half of Acropora species showed moderate to heavy bleaching, similar to the response of Acropora species to the 1994 bleaching event (G. Paulay, pers. comm.). There was also little mortality, except for a localized die-off on Piti Reef Flat due to extreme tidal conditions (G. Davis, pers. comm.). A recent bleaching event in Pago Bay appears to be linked to freshwater influx from the record rainfall associated with Tropical Storm Tingting in June 2004 (P. Schupp, pers. comm.). Bonito and Richmond (submitted) reported that a UOGML scientist observed cases of coral bleaching on Guam every year for at least the past seven years, but again, they were not accompanied by mass mortality. However, as SSTs continue to rise, coral bleaching events may become more frequent and more deleterious on Guam. Diseases Although many common coral diseases have been identified on Guam's reefs, no systematic survey specifically addressing disease has been undertaken. In general, coral disease appears to be much more problematic in the Caribbean and Atlantic than in the Pacific Ocean to date.

In this paper, we present an innovative architecture that enables the digital representation of o... more In this paper, we present an innovative architecture that enables the digital representation of original works and derivatives while implementing Digital Rights Management (DRM) with the aim of focusing on promoting trust within the multimedia content value networks rather than solely on content access and protection control. The system combines different features common in DRM systems such as licensing, content protection, authorisation and reporting together with innovative concepts, such as the linkage of original and derived content and the definition of potential rights. The transmission of reporting requests across the content value network combined with the possibility for authors to exercise rights over derivative works enables the system to determine automatically the percentage of income corresponding to each of the actors involved in different steps of the creation and distribution chain. The implementation consists of a web application which interacts with different external services plus a user application used to render protected content. It is currently publicly accessible for evaluation.

Academic Emergency Medicine, 2007

Bacterial infection often results in the formation of tissue abscesses, which represent the prima... more Bacterial infection often results in the formation of tissue abscesses, which represent the primary site of interaction between invading bacteria and the innate immune system. We identify the host protein calprotectin as a neutrophil-dependent factor expressed inside Staphylococcus aureus abscesses. Neutrophil-derived calprotectin inhibited S. aureus growth through chelation of nutrient Mn 2+ and Zn 2+ : an activity that results in reprogramming of the bacterial transcriptome. The abscesses of mice lacking calprotectin were enriched in metal, and staphylococcal proliferation was enhanced in these metal-rich abscesses. These results demonstrate that calprotectin is a critical factor in the innate immune response to infection and define metal chelation as a strategy for inhibiting microbial growth inside abscessed tissue.

Journal of the Air & …, 2001

The main goal of this study was to evaluate the magnitude of outdoor exposure to fine particulate... more The main goal of this study was to evaluate the magnitude of outdoor exposure to fine particulate matter (PM 10 ) potentially experienced by the population of metropolitan Mexico City. With the use of a geographic information system (GIS), spatially resolved PM 10 distributions were ...

Environmental …, 2009

Exposure to particulate matter (PM) induces inflammatory cytokines. In the present study, we eval... more Exposure to particulate matter (PM) induces inflammatory cytokines. In the present study, we evaluated the secretion of IL-6 and IL-8 by an airway cell line exposed to PM with a mean aerodynamic size equal to or less than 10 or 2.5 μm (PM 10 and PM 2.5 , respectively) collected in ...

Molecular microbiology, Feb 1, 2011

Summary Staphylococcus aureus is an important pathogen that continues to be a significant global ... more Summary Staphylococcus aureus is an important pathogen that continues to be a significant global health threat because of the prevalence of methicillin-resistant S. aureus strains (MRSA). The pathogenesis of this organism is partly attributed to the production of a large repertoire of cytotoxins that target and kill innate immune cells, which provide the first line of defence against S. aureus infection. Here we demonstrate that leukocidin A/B (LukAB) is required and sufficient for the ability of S.

Journal of virology, Dec 1, 2006

Human CD4+ T cells are major targets for human immunodeficiency virus (HIV) infection. Resting T ... more Human CD4+ T cells are major targets for human immunodeficiency virus (HIV) infection. Resting T cells are resistant to HIV infection unless activated through the T-cell receptor (TCR) or by cytokine signals. How T-cell signaling promotes susceptibility of T cells to HIV infection remains poorly understood. Here we demonstrate that the VacA toxin produced by Helicobacter pylori can inhibit HIV infection of primary T cells, stimulated through the TCR or by cytokines alone.

Nature, Dec 12, 2012

Pore-forming toxins are critical virulence factors for many bacterial pathogens and are central t... more Pore-forming toxins are critical virulence factors for many bacterial pathogens and are central to Staphylococcus aureus-mediated killing of host cells. S. aureus encodes pore-forming bi-component leukotoxins that are toxic towards neutrophils, but also specifically target other immune cells. Despite decades since the first description of staphylococcal leukocidal activity, the host factors responsible for the selectivity of leukotoxins towards different immune cells remain unknown.

American Journal of Health Education, 2005

Cervical cancer is a major health concern for Latinas, who are also less likely to undergo a Pap ... more Cervical cancer is a major health concern for Latinas, who are also less likely to undergo a Pap smear exam than the general population. This study identifies alterable determinants of Pap smear screening for Latino women living in a rural area of California. It involved the design and pilot testing of a culturally appropriate instrument and the development of semi-structured interviews with 51 Latinas. Qualitative data were analyzed using NUD*IST. Results from this study indicate that the main factors identified by participants as hindering their decision to seek Pap smear exams were long waiting periods, a lack of continuity of care, a perceived lack of quality of care, language differences, and a lack of knowledge regarding how to access the health system. This article provides health educators working in health care settings with an analysis of the cultural and logistic factors influencing health-related decisions in immigrant and rural Latino populations. It also presents some of the lessons that health educators can learn to enhance their professional practice when working with disadvantaged populations.

Trustworthy Internet, 2011

Computación y Sistemas, 2007

This paper focuses on the asymptotic stability of proportional-integral AQM controllers supportin... more This paper focuses on the asymptotic stability of proportional-integral AQM controllers supporting TCP flows. Necessary and sufficient conditions for the asymptotic stability of the closed-loop linearization are provided. As a result, the complete set of proportional-integral controllers that locally stabilizes the equilibrium point is obtained. The robustness of the controllers to uncertainties in the network parameters (number of TCP flows, round-trip time and link capacity) is also addressed. It is shown that designing the controller with respect to the largest expected values of delay and link capacity, and the smallest expected value of TCP loads leads to the complete set of robust stabilizing controllers.

Palynology, 2007

A palynological study of the Cerrejon Formation was conducted in order to date the formation and ... more A palynological study of the Cerrejon Formation was conducted in order to date the formation and understand the floristic composition and diversity of a Paleocene tropical site. The Cerrejon Formation outcrops in the Cerrejon Coal Mine, the largest open cast coal mine in the ...

Earth and Planetary …, 2003

We report paleomagnetic data from 28 sites of Upper Permian to Lower Jurassic strata from norther... more We report paleomagnetic data from 28 sites of Upper Permian to Lower Jurassic strata from northern and southern Peru. In northern Peru (6 ‡S), a stable magnetic component from six Permo-Triassic sites passes fold and reversal tests. The overall mean pole agrees well with Late Permian to Triassic poles from cratonal South America, suggesting this part of Peru has experienced neither significant rotation nor latitudinal transport since the Permo-Triassic. In southern Peru (13 to 16 ‡S), thermal demagnetization isolates stable magnetic components in 16 of 22 Upper Permian to Lower Jurassic sites collected along the transition between the Altiplano and the Eastern Cordillera. These 16 sites are rotated 14 to 147 ‡ counterclockwise and pass an inclinations-only fold test. Within the same structural zone, three other Permo-Triassic sites as well as 10 Paleocene sites also show important counterclockwise rotations [Roperch and Carlier, J. Geophys. Res. 97 (1992) 17233^17249; Butler et al., Geology 23 (1995) 799^802]. The large magnitude and exclusively counterclockwise sense of rotation suggest that the tectonic regime included an important sinistral shear component. No correlation exists between rotation amount and rock age, suggesting the rotations are post-Paleocene in age. Because the rotations occur along the fringe of the Eastern Cordillera, they were likely produced during its structural formation, hence from the Late Oligocene to Present. Sinistral shear acting in the northern part of the Bolivian Orocline appears much more pronounced than that north of the Abancay Deflection, which likely arises from differences in convergence obliquity.

International …, 2007

Stable coatings of spherical poly(vinyl)-N-pyrrolidone (PVP)-coated silver nanoparticle layers we... more Stable coatings of spherical poly(vinyl)-N-pyrrolidone (PVP)-coated silver nanoparticle layers were obtained using spin coating and rapid thermal processing of PVP/Ag nanoparticle composite thin films on optical glass substrates and this simple method extended to the deposition on optical substrates of solid spheres encapsulating silver nanoshapes, by slow heating of the solution of Ag-encapsulating nanospheres to temperatures above 120 ºC.

Quick Search: All GSW Journals, GSW + GeoRef. advanced search. ...

VacA is a secreted toxin that plays a role in Helicobacter pylori colonization of the stomach and... more VacA is a secreted toxin that plays a role in Helicobacter pylori colonization of the stomach and may contribute to the pathogenesis of peptic ulcer disease and gastric cancer. In this study, we analyzed a library of plasmids expressing randomly mutated forms of recombinant VacA and identified 10 mutant VacA proteins that lacked vacuolating cytotoxic activity when added to HeLa cells. The mutations included six single amino acid substitutions within an amino-terminal hydrophobic region and four substitutions outside the aminoterminal hydrophobic region. All 10 mutations mapped within the p33 domain of VacA. By introducing mutations into the H. pylori chromosomal vacA gene, we showed that secreted mutant toxins containing V21L, S25L, G121R, or S246L mutations bound to cells and were internalized but had defects in vacuolating activity. In planar lipid bilayer and membrane depolarization assays, VacA proteins containing V21L and S25L mutations were defective in formation of anion-selective membrane channels, whereas proteins containing G121R or S246L mutations retained channel-forming capacity. These are the first point mutations outside the amino-terminal hydrophobic region that are known to abrogate vacuolating toxin activity. In addition, these are the first examples of mutant VacA proteins that have defects in vacuolating activity despite exhibiting channel activities similar to those of wild-type VacA.

Waddell, JE and AM …, 2008

Guam GROUP NUMBER OF SPECIES SOURCES Seagrasses 3 Lobban and Tsuda, 2003 Benthic Macroalgae 237 *... more Guam GROUP NUMBER OF SPECIES SOURCES Seagrasses 3 Lobban and Tsuda, 2003 Benthic Macroalgae 237 * Number of species is for the entire Mariana Archipelago. The actual number for Guam may be lower. molluscs, and marine algae are also eaten locally. In addition to the cash and subsistence value of edible fish and invertebrates, reef-related fisheries are culturally important as family and group fishing is a common activity in Guam's coastal waters. Over 10% of Guam's coastline has been set aside in five marine preserves: Tumon Bay, Piti Bomb Holes, Sasa Bay, Achang Reef Flat, and Pati Point. The preserves were established in 1997 as a response to decreasing reef fish stocks, but were not fully enforced until 2001. Fishing activity is restricted in the preserves with limited cultural take permitted in three of the five areas. The preserves are complemented by the War in the Pacific National Historical Park, Ritidian National Wildlife Refuge, Guam Territorial Seashore Park, Orote Penisula Ecological Reserve Area (ERA), and Haputo ERA. While management practices are enforced in the five marine preserves, there is currently limited management and enforcement in the other areas. The health of Guam's coral reefs varies considerably, depending on a variety of factors including geology, human population density, level of coastal development, level and types of uses of marine resources, oceanic circulation patterns, and frequency of natural disturbances, such as typhoons and earthquakes. Many of Guam's reefs have declined in health over the past 40 years. The average live coral cover on forereef slopes was approximately 50% in the 1960s (Randall, 1971), but dwindled to less than 25% live coral cover by the 1990s with only a few having over 50% live cover (Birkeland, 1997). In the past, however, Guam's reefs have recovered after drastic declines. For example, an outbreak of the crown-of-thorns starfish (COTS) in the early 1970s reduced coral cover in some areas from 50-60% to less than 1%. Twelve years later, greater than 60% live coral cover was recorded in these areas (Colgan, 1987). A more distressing indicator of the health of Guam's coral reefs is the marked decrease in rates of coral recruitment. In 1979, Birkeland et al. (1982) obtained 0.53 coral recruits per plexiglass fouling panel. The use of similar materials and experimental design in 1989 and 1992 resulted in just 0.004 and 0.009 coral recruits per plexiglass fouling plates, respectively (Birkeland, 1997). Sidebar The State of Coral Reef Ecosystems of Guam ENVIRONMENTAL AND ANTHROPOGENIC STRESSORS Climate Change and Coral Bleaching Large-scale coral bleaching events and associated coral mortality are not common on Guam. Since the establishment of the University of Guam Marine Laboratory (UOGML) in 1970, there have been only two recorded large-scale bleaching events. In 1994, 68% of surveyed taxa bleached on Guam (Paulay and Benayahu, 1999). The event was characterized by considerable inter-species variation in bleaching response and little mortality, and did not appear to be associated with above-average SSTs. In 1996, about half of Acropora species showed moderate to heavy bleaching, similar to the response of Acropora species to the 1994 bleaching event (G. Paulay, pers. comm.). There was also little mortality, except for a localized die-off on Piti Reef Flat due to extreme tidal conditions (G. Davis, pers. comm.). A recent bleaching event in Pago Bay appears to be linked to freshwater influx from the record rainfall associated with Tropical Storm Tingting in June 2004 (P. Schupp, pers. comm.). Bonito and Richmond (submitted) reported that a UOGML scientist observed cases of coral bleaching on Guam every year for at least the past seven years, but again, they were not accompanied by mass mortality. However, as SSTs continue to rise, coral bleaching events may become more frequent and more deleterious on Guam. Diseases Although many common coral diseases have been identified on Guam's reefs, no systematic survey specifically addressing disease has been undertaken. In general, coral disease appears to be much more problematic in the Caribbean and Atlantic than in the Pacific Ocean to date.

In this paper, we present an innovative architecture that enables the digital representation of o... more In this paper, we present an innovative architecture that enables the digital representation of original works and derivatives while implementing Digital Rights Management (DRM) with the aim of focusing on promoting trust within the multimedia content value networks rather than solely on content access and protection control. The system combines different features common in DRM systems such as licensing, content protection, authorisation and reporting together with innovative concepts, such as the linkage of original and derived content and the definition of potential rights. The transmission of reporting requests across the content value network combined with the possibility for authors to exercise rights over derivative works enables the system to determine automatically the percentage of income corresponding to each of the actors involved in different steps of the creation and distribution chain. The implementation consists of a web application which interacts with different external services plus a user application used to render protected content. It is currently publicly accessible for evaluation.

Academic Emergency Medicine, 2007

Bacterial infection often results in the formation of tissue abscesses, which represent the prima... more Bacterial infection often results in the formation of tissue abscesses, which represent the primary site of interaction between invading bacteria and the innate immune system. We identify the host protein calprotectin as a neutrophil-dependent factor expressed inside Staphylococcus aureus abscesses. Neutrophil-derived calprotectin inhibited S. aureus growth through chelation of nutrient Mn 2+ and Zn 2+ : an activity that results in reprogramming of the bacterial transcriptome. The abscesses of mice lacking calprotectin were enriched in metal, and staphylococcal proliferation was enhanced in these metal-rich abscesses. These results demonstrate that calprotectin is a critical factor in the innate immune response to infection and define metal chelation as a strategy for inhibiting microbial growth inside abscessed tissue.

Journal of the Air & …, 2001

The main goal of this study was to evaluate the magnitude of outdoor exposure to fine particulate... more The main goal of this study was to evaluate the magnitude of outdoor exposure to fine particulate matter (PM 10 ) potentially experienced by the population of metropolitan Mexico City. With the use of a geographic information system (GIS), spatially resolved PM 10 distributions were ...

Environmental …, 2009

Exposure to particulate matter (PM) induces inflammatory cytokines. In the present study, we eval... more Exposure to particulate matter (PM) induces inflammatory cytokines. In the present study, we evaluated the secretion of IL-6 and IL-8 by an airway cell line exposed to PM with a mean aerodynamic size equal to or less than 10 or 2.5 μm (PM 10 and PM 2.5 , respectively) collected in ...

Molecular microbiology, Feb 1, 2011

Summary Staphylococcus aureus is an important pathogen that continues to be a significant global ... more Summary Staphylococcus aureus is an important pathogen that continues to be a significant global health threat because of the prevalence of methicillin-resistant S. aureus strains (MRSA). The pathogenesis of this organism is partly attributed to the production of a large repertoire of cytotoxins that target and kill innate immune cells, which provide the first line of defence against S. aureus infection. Here we demonstrate that leukocidin A/B (LukAB) is required and sufficient for the ability of S.

Journal of virology, Dec 1, 2006

Human CD4+ T cells are major targets for human immunodeficiency virus (HIV) infection. Resting T ... more Human CD4+ T cells are major targets for human immunodeficiency virus (HIV) infection. Resting T cells are resistant to HIV infection unless activated through the T-cell receptor (TCR) or by cytokine signals. How T-cell signaling promotes susceptibility of T cells to HIV infection remains poorly understood. Here we demonstrate that the VacA toxin produced by Helicobacter pylori can inhibit HIV infection of primary T cells, stimulated through the TCR or by cytokines alone.

Nature, Dec 12, 2012

Pore-forming toxins are critical virulence factors for many bacterial pathogens and are central t... more Pore-forming toxins are critical virulence factors for many bacterial pathogens and are central to Staphylococcus aureus-mediated killing of host cells. S. aureus encodes pore-forming bi-component leukotoxins that are toxic towards neutrophils, but also specifically target other immune cells. Despite decades since the first description of staphylococcal leukocidal activity, the host factors responsible for the selectivity of leukotoxins towards different immune cells remain unknown.

American Journal of Health Education, 2005

Cervical cancer is a major health concern for Latinas, who are also less likely to undergo a Pap ... more Cervical cancer is a major health concern for Latinas, who are also less likely to undergo a Pap smear exam than the general population. This study identifies alterable determinants of Pap smear screening for Latino women living in a rural area of California. It involved the design and pilot testing of a culturally appropriate instrument and the development of semi-structured interviews with 51 Latinas. Qualitative data were analyzed using NUD*IST. Results from this study indicate that the main factors identified by participants as hindering their decision to seek Pap smear exams were long waiting periods, a lack of continuity of care, a perceived lack of quality of care, language differences, and a lack of knowledge regarding how to access the health system. This article provides health educators working in health care settings with an analysis of the cultural and logistic factors influencing health-related decisions in immigrant and rural Latino populations. It also presents some of the lessons that health educators can learn to enhance their professional practice when working with disadvantaged populations.

Trustworthy Internet, 2011

Computación y Sistemas, 2007

This paper focuses on the asymptotic stability of proportional-integral AQM controllers supportin... more This paper focuses on the asymptotic stability of proportional-integral AQM controllers supporting TCP flows. Necessary and sufficient conditions for the asymptotic stability of the closed-loop linearization are provided. As a result, the complete set of proportional-integral controllers that locally stabilizes the equilibrium point is obtained. The robustness of the controllers to uncertainties in the network parameters (number of TCP flows, round-trip time and link capacity) is also addressed. It is shown that designing the controller with respect to the largest expected values of delay and link capacity, and the smallest expected value of TCP loads leads to the complete set of robust stabilizing controllers.

Palynology, 2007

A palynological study of the Cerrejon Formation was conducted in order to date the formation and ... more A palynological study of the Cerrejon Formation was conducted in order to date the formation and understand the floristic composition and diversity of a Paleocene tropical site. The Cerrejon Formation outcrops in the Cerrejon Coal Mine, the largest open cast coal mine in the ...

Earth and Planetary …, 2003

We report paleomagnetic data from 28 sites of Upper Permian to Lower Jurassic strata from norther... more We report paleomagnetic data from 28 sites of Upper Permian to Lower Jurassic strata from northern and southern Peru. In northern Peru (6 ‡S), a stable magnetic component from six Permo-Triassic sites passes fold and reversal tests. The overall mean pole agrees well with Late Permian to Triassic poles from cratonal South America, suggesting this part of Peru has experienced neither significant rotation nor latitudinal transport since the Permo-Triassic. In southern Peru (13 to 16 ‡S), thermal demagnetization isolates stable magnetic components in 16 of 22 Upper Permian to Lower Jurassic sites collected along the transition between the Altiplano and the Eastern Cordillera. These 16 sites are rotated 14 to 147 ‡ counterclockwise and pass an inclinations-only fold test. Within the same structural zone, three other Permo-Triassic sites as well as 10 Paleocene sites also show important counterclockwise rotations [Roperch and Carlier, J. Geophys. Res. 97 (1992) 17233^17249; Butler et al., Geology 23 (1995) 799^802]. The large magnitude and exclusively counterclockwise sense of rotation suggest that the tectonic regime included an important sinistral shear component. No correlation exists between rotation amount and rock age, suggesting the rotations are post-Paleocene in age. Because the rotations occur along the fringe of the Eastern Cordillera, they were likely produced during its structural formation, hence from the Late Oligocene to Present. Sinistral shear acting in the northern part of the Bolivian Orocline appears much more pronounced than that north of the Abancay Deflection, which likely arises from differences in convergence obliquity.