Guillermo Couto - Academia.edu (original) (raw)
Papers by Guillermo Couto
Journal of Clinical Microbiology, 1997
A partial 16S rRNA gene was amplified in Ehrlichia canis-infected cells by nested PCR. The assay ... more A partial 16S rRNA gene was amplified in Ehrlichia canis-infected cells by nested PCR. The assay was specific and did not amplify the closely related Ehrlichia chaffeensis, Ehrlichia muris, Neorickettsia helminthoeca, and SF agent 16S rRNA genes. The assay was as sensitive as Southern hybridization, detecting as little as 0.2 pg of E. canis DNA. By this method, all blood samples from four dogs experimentally infected with E. canis were positive as early as day 4 postinoculation, which was before or at the time of seroconversion. One hundred five blood samples from dogs from Arizona and Texas (areas of E. canis endemicity) and 30 blood samples from dogs from Ohio (area of E. canis nonendemicity) were examined by nested PCR and immunofluorescent-antibody (IFA) test. Approximately 84% of dogs from Arizona and Texas had been treated with doxycycline before submission of blood specimens. Among Arizona and Texas specimens, 46 samples were PCR positive (44%) and 80 were IFA positive (76%)....
Journal of Herpetological Medicine and Surgery, 2007
Veterinary Clinics of North America: Small Animal Practice, 1990
The use of adjuvant chemotherapy appears to offer many advantages to the patient with cancer. How... more The use of adjuvant chemotherapy appears to offer many advantages to the patient with cancer. However, objective information is difficult to compile. Clinical trials all too often have only a small number of patients. In order to best demonstrate the usefulness of adjuvant chemotherapy, many of the cases discussed here had bulky disease. Based on the known principles of chemotherapy, animals with minimal residual disease following surgery would most likely benefit from adjuvant chemotherapy. By using the principles discussed at the beginning of this article and information from clinical trials, veterinarians will better be able to inform clients of possible benefits and risks in treating their pets with chemotherapy.
Journal of Veterinary Emergency and Critical Care, 1993
Journal of Veterinary Diagnostic Investigation, 2000
Case information and histologic slides for 688 admissions of feline tissues from 12 veterinary in... more Case information and histologic slides for 688 admissions of feline tissues from 12 veterinary institutions were assembled and reviewed to determine tissues obtained by biopsy or necropsy, age and sex of cat, tumor topography, feline leukemia viral antigen status, histologic frequency of mitoses, diagnosis, presence of necrosis, and presence and degree of sclerosis. Histologic sections were examined to place the lesions in one of the diagnostic categories of the National Cancer Institute working formulation (NCI WF) for lymphomas or lymphoid leukemia. Correlations between the various factors determined were tested using contingency tables and chi-square analysis to provide a statistical comparison between the levels of observations determined by case examination with the numbers expected from chance alone. Significant correlations ( P ≤ 0.05) were found between diagnosis and tumor topography, the frequency of mitoses, necrosis, sclerosis, and age, between mitoses and necrosis, topog...
Journal of Feline Medicine and Surgery, 2000
Etiology and epidemiology Previous reports document that approximately 70% of cats with lymphoma ... more Etiology and epidemiology Previous reports document that approximately 70% of cats with lymphoma are feline leukaemia virus (FeLV)-positive. The prevalence of viraemia in cats with lymphoma varies with the anatomical form of presentation but, in general, young cats with lymphoma are FeLV-positive, whereas older cats are FeLV-negative. Over the past few years, the prevalence of FeLV infection in cats with lymphoma in our clinic is decreasing. Feline immunodeficiency virus (FIV) infection significantly increases the risk of developing lymphoma. The age of presentation in cats with lymphoma is bimodal; the first peak occurs at approximately 2 years of age and the second one at approximately 10–12 years of age. The first peak is composed mainly of FeLV-positive cats, whereas the second one includes predominantly FeLVnegative cats. The mean age of presentation of lymphoma in FeLV-positive cats is 3 years, whereas in FeLV-negative cats it is 7–8 years.
Acta Crystallographica Section D Biological Crystallography, 2011
This study presents the crystal structure of Greyhound hemoglobin (GrHb) determined to 1.9 Å reso... more This study presents the crystal structure of Greyhound hemoglobin (GrHb) determined to 1.9 Å resolution. GrHb was found to crystallize with an α₁β₁ dimer in the asymmetric unit and belongs to the R2 state. Oxygen-affinity measurements combined with the fact that GrHb crystallizes in the R2 state despite the high-salt conditions used for crystallization strongly indicate that GrHb can serve as a model high-oxygen-affinity hemoglobin (Hb) for higher mammals, especially humans. Structural analysis of GrHb and its comparison with the R2-state of human Hb revealed several regions that can potentially contribute to the high oxygen affinity of GrHb and serve to rationalize the additional stability of the R2-state of GrHb. A previously well studied hydrophobic cluster of bar-headed goose Hb near α119 was also incorporated in the comparison between GrHb and human Hb. Finally, a structural comparison with generic dog Hb and maned wolf Hb was conducted, revealing that in contrast to GrHb these structures belong to the R state of Hb and raising the intriguing possibility of an additional allosteric factor co-purifying with GrHb that can modulate its quaternary structure.
The purpose of this article is to provide a brief overview of the components of the blood work in... more The purpose of this article is to provide a brief overview of the components of the blood work in dogs, and to illustrate how values in Greyhounds frequently differ from those in dogs of other breeds. Blood work is a general term referring to diagnostic laboratory tests done on blood samples, and include everything from heartworm tests to thyroid hormone assays. Some of the indications for performing blood work include illness, annual health checks, and pre-anesthesia. The most commonly performed tests when a veterinarian refers to "running blood work" are the complete blood cell count (CBC) and the serum biochemical profile.
Veterinary Pathology, 1996
Alterations in the p53 tumor suppressor gene have been implicated in the genesis and/or progressi... more Alterations in the p53 tumor suppressor gene have been implicated in the genesis and/or progression of the majority of human cancers, including osteosarcoma. Stabilization of the protein by mutation or interaction with other proteins prolongs its half-life, rendering it detectable by immunohistochemistry. Osteosarcoma is the most common primary canine bone tumor and is characterized by frequent early metastases. Multilobular tumors of bone involve primarily flat bones of the head and are low-grade malignancies with lower metastatic potential. The objectives of this study were to determine the prevalence of p53 protein overexpression in 106 osteogenic tumors of dogs using an indirect immunohistochemical method and to compare p53 overexpression between tumors with different clinical behavior. A polyclonal p53 antibody (CM-1) served as the primary antibody. Tumors were scored based upon an estimate of the percentage of tumor cells stained. Significant differences in the prevalence of o...
American journal of veterinary research, 1995
A 55-kd protein with mRNA transport activity found in fetal rat liver cells and plasma from mice,... more A 55-kd protein with mRNA transport activity found in fetal rat liver cells and plasma from mice, rats, and human beings with malignant neoplasms has been designated oncofetal protein 55 (OFP55). Monoclonal antibody produced to rat OFP55 cross-reacts with human OFP55. Using this monoclonal antibody in a bioassay measuring mRNA transport stimulated by OFP55, we tested the plasma from 19 dogs with a variety of malignant neoplasms, including carcinomas, sarcomas, lymphomas, and melanomas, and compared the results with plasma from 20 clinically normal dogs without evidence of neoplasia. The mean mRNA transport activity from the group of dogs with malignant neoplasms was 0.43 +/- 0.28%/mg of protein. Mean transport activity from the group of control dogs was 0.04 +/- 0.02%/mg of protein. These means were significantly different (P < 0.0001). The degree of overlap between these 2 groups in their OFP55-related mRNA transport activity was minimal, and measurement of this protein appears ...
American journal of veterinary research, 1995
Twenty-four horses were randomly allocated to 3 groups. All horses underwent a ventral midline ce... more Twenty-four horses were randomly allocated to 3 groups. All horses underwent a ventral midline celiotomy, and the large colon was exteriorized and instrumented. Group-1 horses served as sham-operated controls, group-2 horses underwent 6 hours of colonic ischemia, and group-3 horses were subjected to 3 hours of ischemia and 3 hours of reperfusion. Baseline blood samples were collected, then low-flow colonic ischemia was induced in horses of groups 2 and 3 by reducing colonic arterial blood flow to 20% of baseline. All horses were monitored for 6 hours. Citrated systemic venous (SV) blood samples were collected from the main pulmonary artery, and colonic venous (CV) samples were collected from the colonic vein draining the ventral colon. Samples were collected at 0, and 2, 3, 3.25, 4, and 6 hours for determination of one-stage prothrombin time, activated partial thromboplastin time, antithrombin III activity, and fibrinogen concentration. Data were analyzed statistically, using two-wa...
Journal of the American Veterinary Medical Association, 1984
Journal of the American Veterinary Medical Association, 1985
Nineteen cases of canine acute leukemia were diagnosed during a 4-year period. Two main categorie... more Nineteen cases of canine acute leukemia were diagnosed during a 4-year period. Two main categories were identified on the basis of cytologic, hematologic, and clinical features: acute lymphoid leukemia and acute myelogenous leukemia. Clinical features included history of weight loss, anorexia, shifting limb lameness, and incoordination. Physical findings were characterized by hepatomegaly, splenomegaly, mild generalized lymphadenopathy, and pallor. Ocular lesions were found in 29% of dogs with acute myelogenous leukemia. Hematologic abnormalities included anemia, thrombocytopenia, pancytopenia, leukemia, and leukoerythroblastic reactions. Results of therapy were discouraging.
Journal of the American Veterinary Medical Association, Jan 15, 1988
Thirteen dogs with tumors were treated with monthly infusions of cisplatin. Complete responses we... more Thirteen dogs with tumors were treated with monthly infusions of cisplatin. Complete responses were not observed. Of 8 dogs with urinary tract transitional cell carcinomas, 1 (12.5%) had a partial response of 31 weeks' duration, and 4 (50%) had stable disease for 12, 30, 32, and 34 weeks. Three (60%) of 5 dogs with head and neck squamous cell carcinomas had partial responses for 2, 10, and 15 weeks. All 13 dogs were evaluated for signs of toxicosis. Transient episodes of vomiting were recorded for 7 dogs (54%), and 2 dogs (15%) had mild thrombocytopenia. Although renal function gradually decreased in 2 dogs (15%), none of the dogs had an episode of acute renal failure attributable to cisplatin. These findings suggest that cisplatin may be a safe and potentially effective agent for treatment of transitional cell and squamous cell carcinomas in dogs.
Journal of the American Animal Hospital Association, 2014
To evaluate the clinical toxicity and activity of orally administered artemisinin in dogs with sp... more To evaluate the clinical toxicity and activity of orally administered artemisinin in dogs with spontaneous tumors, 24 client-owned dogs were randomly divided into two groups and received either low-continuous dose (3 mg/kg q 24 hr) or high-dose intermittent (three doses of 45 mg/kg q 6 hr repeated q 1 wk) of artemisinin per os. Treatment was continued for 21 days. Dogs were evaluated weekly for clinical effect and at the end of the treatment for hematologic and biochemical adverse events. Whole blood concentrations of artemisinin and dihydroartemisinin were measured by liquid chromatography/tandem mass spectrometry after the first dose of artemisinin in three dogs in each group. Blood concentrations of artemisinin and dihydroartemisinin were <0.1 μM at all time points, and there was no difference in blood concentration between the two dosing groups. The most frequent adverse event was anorexia, which was observed in 11% of the low-dose group and 29% of the high-dose group. Oral a...
Veterinary Pathology, 1992
Mithramycin (0.1 mg/kg) was administered intravenously to eight Beagle dogs on days 0 and 7 to de... more Mithramycin (0.1 mg/kg) was administered intravenously to eight Beagle dogs on days 0 and 7 to determine its effects on calcium and phosphorus metabolism, serum parathyroid hormone concentration, osteoclastic bone resorption, and serum biochemical and hematologic parameters. Ionized calcium concentration was paradoxically increased on day 1 and decreased on day 8 in association with an increased serum parathyroid hormone concentration. Serum phosphorus concentration was decreased on days 1 and 2. Osteoclastic bone resorption in iliac cancellous bone was significantly decreased on day 8. There were mild increases in serum alkaline phosphatase (days 1, 2, 4, 8, 9), aspartate aminotransferase (day 9), and gammaglutamyl transpeptidase (days 7, 9) activities. Platelet numbers were increased on days 7 through 13, and packed red blood cell volumes were mildly decreased. This investigation demonstrates that two doses of mithramycin can be administered safely to dogs and may inhibit bone res...
Veterinary Clinical Pathology, 2014
Journal of Clinical Microbiology, 1997
A partial 16S rRNA gene was amplified in Ehrlichia canis-infected cells by nested PCR. The assay ... more A partial 16S rRNA gene was amplified in Ehrlichia canis-infected cells by nested PCR. The assay was specific and did not amplify the closely related Ehrlichia chaffeensis, Ehrlichia muris, Neorickettsia helminthoeca, and SF agent 16S rRNA genes. The assay was as sensitive as Southern hybridization, detecting as little as 0.2 pg of E. canis DNA. By this method, all blood samples from four dogs experimentally infected with E. canis were positive as early as day 4 postinoculation, which was before or at the time of seroconversion. One hundred five blood samples from dogs from Arizona and Texas (areas of E. canis endemicity) and 30 blood samples from dogs from Ohio (area of E. canis nonendemicity) were examined by nested PCR and immunofluorescent-antibody (IFA) test. Approximately 84% of dogs from Arizona and Texas had been treated with doxycycline before submission of blood specimens. Among Arizona and Texas specimens, 46 samples were PCR positive (44%) and 80 were IFA positive (76%)....
Journal of Herpetological Medicine and Surgery, 2007
Veterinary Clinics of North America: Small Animal Practice, 1990
The use of adjuvant chemotherapy appears to offer many advantages to the patient with cancer. How... more The use of adjuvant chemotherapy appears to offer many advantages to the patient with cancer. However, objective information is difficult to compile. Clinical trials all too often have only a small number of patients. In order to best demonstrate the usefulness of adjuvant chemotherapy, many of the cases discussed here had bulky disease. Based on the known principles of chemotherapy, animals with minimal residual disease following surgery would most likely benefit from adjuvant chemotherapy. By using the principles discussed at the beginning of this article and information from clinical trials, veterinarians will better be able to inform clients of possible benefits and risks in treating their pets with chemotherapy.
Journal of Veterinary Emergency and Critical Care, 1993
Journal of Veterinary Diagnostic Investigation, 2000
Case information and histologic slides for 688 admissions of feline tissues from 12 veterinary in... more Case information and histologic slides for 688 admissions of feline tissues from 12 veterinary institutions were assembled and reviewed to determine tissues obtained by biopsy or necropsy, age and sex of cat, tumor topography, feline leukemia viral antigen status, histologic frequency of mitoses, diagnosis, presence of necrosis, and presence and degree of sclerosis. Histologic sections were examined to place the lesions in one of the diagnostic categories of the National Cancer Institute working formulation (NCI WF) for lymphomas or lymphoid leukemia. Correlations between the various factors determined were tested using contingency tables and chi-square analysis to provide a statistical comparison between the levels of observations determined by case examination with the numbers expected from chance alone. Significant correlations ( P ≤ 0.05) were found between diagnosis and tumor topography, the frequency of mitoses, necrosis, sclerosis, and age, between mitoses and necrosis, topog...
Journal of Feline Medicine and Surgery, 2000
Etiology and epidemiology Previous reports document that approximately 70% of cats with lymphoma ... more Etiology and epidemiology Previous reports document that approximately 70% of cats with lymphoma are feline leukaemia virus (FeLV)-positive. The prevalence of viraemia in cats with lymphoma varies with the anatomical form of presentation but, in general, young cats with lymphoma are FeLV-positive, whereas older cats are FeLV-negative. Over the past few years, the prevalence of FeLV infection in cats with lymphoma in our clinic is decreasing. Feline immunodeficiency virus (FIV) infection significantly increases the risk of developing lymphoma. The age of presentation in cats with lymphoma is bimodal; the first peak occurs at approximately 2 years of age and the second one at approximately 10–12 years of age. The first peak is composed mainly of FeLV-positive cats, whereas the second one includes predominantly FeLVnegative cats. The mean age of presentation of lymphoma in FeLV-positive cats is 3 years, whereas in FeLV-negative cats it is 7–8 years.
Acta Crystallographica Section D Biological Crystallography, 2011
This study presents the crystal structure of Greyhound hemoglobin (GrHb) determined to 1.9 Å reso... more This study presents the crystal structure of Greyhound hemoglobin (GrHb) determined to 1.9 Å resolution. GrHb was found to crystallize with an α₁β₁ dimer in the asymmetric unit and belongs to the R2 state. Oxygen-affinity measurements combined with the fact that GrHb crystallizes in the R2 state despite the high-salt conditions used for crystallization strongly indicate that GrHb can serve as a model high-oxygen-affinity hemoglobin (Hb) for higher mammals, especially humans. Structural analysis of GrHb and its comparison with the R2-state of human Hb revealed several regions that can potentially contribute to the high oxygen affinity of GrHb and serve to rationalize the additional stability of the R2-state of GrHb. A previously well studied hydrophobic cluster of bar-headed goose Hb near α119 was also incorporated in the comparison between GrHb and human Hb. Finally, a structural comparison with generic dog Hb and maned wolf Hb was conducted, revealing that in contrast to GrHb these structures belong to the R state of Hb and raising the intriguing possibility of an additional allosteric factor co-purifying with GrHb that can modulate its quaternary structure.
The purpose of this article is to provide a brief overview of the components of the blood work in... more The purpose of this article is to provide a brief overview of the components of the blood work in dogs, and to illustrate how values in Greyhounds frequently differ from those in dogs of other breeds. Blood work is a general term referring to diagnostic laboratory tests done on blood samples, and include everything from heartworm tests to thyroid hormone assays. Some of the indications for performing blood work include illness, annual health checks, and pre-anesthesia. The most commonly performed tests when a veterinarian refers to "running blood work" are the complete blood cell count (CBC) and the serum biochemical profile.
Veterinary Pathology, 1996
Alterations in the p53 tumor suppressor gene have been implicated in the genesis and/or progressi... more Alterations in the p53 tumor suppressor gene have been implicated in the genesis and/or progression of the majority of human cancers, including osteosarcoma. Stabilization of the protein by mutation or interaction with other proteins prolongs its half-life, rendering it detectable by immunohistochemistry. Osteosarcoma is the most common primary canine bone tumor and is characterized by frequent early metastases. Multilobular tumors of bone involve primarily flat bones of the head and are low-grade malignancies with lower metastatic potential. The objectives of this study were to determine the prevalence of p53 protein overexpression in 106 osteogenic tumors of dogs using an indirect immunohistochemical method and to compare p53 overexpression between tumors with different clinical behavior. A polyclonal p53 antibody (CM-1) served as the primary antibody. Tumors were scored based upon an estimate of the percentage of tumor cells stained. Significant differences in the prevalence of o...
American journal of veterinary research, 1995
A 55-kd protein with mRNA transport activity found in fetal rat liver cells and plasma from mice,... more A 55-kd protein with mRNA transport activity found in fetal rat liver cells and plasma from mice, rats, and human beings with malignant neoplasms has been designated oncofetal protein 55 (OFP55). Monoclonal antibody produced to rat OFP55 cross-reacts with human OFP55. Using this monoclonal antibody in a bioassay measuring mRNA transport stimulated by OFP55, we tested the plasma from 19 dogs with a variety of malignant neoplasms, including carcinomas, sarcomas, lymphomas, and melanomas, and compared the results with plasma from 20 clinically normal dogs without evidence of neoplasia. The mean mRNA transport activity from the group of dogs with malignant neoplasms was 0.43 +/- 0.28%/mg of protein. Mean transport activity from the group of control dogs was 0.04 +/- 0.02%/mg of protein. These means were significantly different (P < 0.0001). The degree of overlap between these 2 groups in their OFP55-related mRNA transport activity was minimal, and measurement of this protein appears ...
American journal of veterinary research, 1995
Twenty-four horses were randomly allocated to 3 groups. All horses underwent a ventral midline ce... more Twenty-four horses were randomly allocated to 3 groups. All horses underwent a ventral midline celiotomy, and the large colon was exteriorized and instrumented. Group-1 horses served as sham-operated controls, group-2 horses underwent 6 hours of colonic ischemia, and group-3 horses were subjected to 3 hours of ischemia and 3 hours of reperfusion. Baseline blood samples were collected, then low-flow colonic ischemia was induced in horses of groups 2 and 3 by reducing colonic arterial blood flow to 20% of baseline. All horses were monitored for 6 hours. Citrated systemic venous (SV) blood samples were collected from the main pulmonary artery, and colonic venous (CV) samples were collected from the colonic vein draining the ventral colon. Samples were collected at 0, and 2, 3, 3.25, 4, and 6 hours for determination of one-stage prothrombin time, activated partial thromboplastin time, antithrombin III activity, and fibrinogen concentration. Data were analyzed statistically, using two-wa...
Journal of the American Veterinary Medical Association, 1984
Journal of the American Veterinary Medical Association, 1985
Nineteen cases of canine acute leukemia were diagnosed during a 4-year period. Two main categorie... more Nineteen cases of canine acute leukemia were diagnosed during a 4-year period. Two main categories were identified on the basis of cytologic, hematologic, and clinical features: acute lymphoid leukemia and acute myelogenous leukemia. Clinical features included history of weight loss, anorexia, shifting limb lameness, and incoordination. Physical findings were characterized by hepatomegaly, splenomegaly, mild generalized lymphadenopathy, and pallor. Ocular lesions were found in 29% of dogs with acute myelogenous leukemia. Hematologic abnormalities included anemia, thrombocytopenia, pancytopenia, leukemia, and leukoerythroblastic reactions. Results of therapy were discouraging.
Journal of the American Veterinary Medical Association, Jan 15, 1988
Thirteen dogs with tumors were treated with monthly infusions of cisplatin. Complete responses we... more Thirteen dogs with tumors were treated with monthly infusions of cisplatin. Complete responses were not observed. Of 8 dogs with urinary tract transitional cell carcinomas, 1 (12.5%) had a partial response of 31 weeks' duration, and 4 (50%) had stable disease for 12, 30, 32, and 34 weeks. Three (60%) of 5 dogs with head and neck squamous cell carcinomas had partial responses for 2, 10, and 15 weeks. All 13 dogs were evaluated for signs of toxicosis. Transient episodes of vomiting were recorded for 7 dogs (54%), and 2 dogs (15%) had mild thrombocytopenia. Although renal function gradually decreased in 2 dogs (15%), none of the dogs had an episode of acute renal failure attributable to cisplatin. These findings suggest that cisplatin may be a safe and potentially effective agent for treatment of transitional cell and squamous cell carcinomas in dogs.
Journal of the American Animal Hospital Association, 2014
To evaluate the clinical toxicity and activity of orally administered artemisinin in dogs with sp... more To evaluate the clinical toxicity and activity of orally administered artemisinin in dogs with spontaneous tumors, 24 client-owned dogs were randomly divided into two groups and received either low-continuous dose (3 mg/kg q 24 hr) or high-dose intermittent (three doses of 45 mg/kg q 6 hr repeated q 1 wk) of artemisinin per os. Treatment was continued for 21 days. Dogs were evaluated weekly for clinical effect and at the end of the treatment for hematologic and biochemical adverse events. Whole blood concentrations of artemisinin and dihydroartemisinin were measured by liquid chromatography/tandem mass spectrometry after the first dose of artemisinin in three dogs in each group. Blood concentrations of artemisinin and dihydroartemisinin were <0.1 μM at all time points, and there was no difference in blood concentration between the two dosing groups. The most frequent adverse event was anorexia, which was observed in 11% of the low-dose group and 29% of the high-dose group. Oral a...
Veterinary Pathology, 1992
Mithramycin (0.1 mg/kg) was administered intravenously to eight Beagle dogs on days 0 and 7 to de... more Mithramycin (0.1 mg/kg) was administered intravenously to eight Beagle dogs on days 0 and 7 to determine its effects on calcium and phosphorus metabolism, serum parathyroid hormone concentration, osteoclastic bone resorption, and serum biochemical and hematologic parameters. Ionized calcium concentration was paradoxically increased on day 1 and decreased on day 8 in association with an increased serum parathyroid hormone concentration. Serum phosphorus concentration was decreased on days 1 and 2. Osteoclastic bone resorption in iliac cancellous bone was significantly decreased on day 8. There were mild increases in serum alkaline phosphatase (days 1, 2, 4, 8, 9), aspartate aminotransferase (day 9), and gammaglutamyl transpeptidase (days 7, 9) activities. Platelet numbers were increased on days 7 through 13, and packed red blood cell volumes were mildly decreased. This investigation demonstrates that two doses of mithramycin can be administered safely to dogs and may inhibit bone res...
Veterinary Clinical Pathology, 2014