Gwen Hirsch - Academia.edu (original) (raw)
Papers by Gwen Hirsch
HortScience, Jul 1, 2004
Temperate zone fruit crops undergo bud dormancy which can be described as a mechanism for avoidin... more Temperate zone fruit crops undergo bud dormancy which can be described as a mechanism for avoiding the exposure of tender fl owers and leaves to low winter temperatures. In Kenya, apple growing is mostly hampered by inadequate chilling that causes the plants to have prolonged dormancy leading to poor fl owering and consequently low yield. Although the chilling requirements are obligatory, under subtropical and especially tropical conditions avoidance is possible. To achieve this, it is necessary to select cultivars with low chilling requirements. This has proven effective in Zimbabwe with cultivar Matsu which is grown without a need for artifi cial breaking of dormancy. In Kenya like Zimbabwe, low chilling requiring cultivars such as Anna have been grown successfully. However, for cultivars with high chilling requirements, there is need to apply artifi cial techniques/methods to enhance bud break. Some of the cultural techniques used are: defoliation after harvesting and bending of the shoots holizontally. Defoliation after harvesting has particularly been used successfully in the island of Java in Indonesia and it enables two crops to be grown per year. Root chilling of rootstock has also been found to enhance bud break of the shoot. In addition, chemicals like KNO 3 , mineral oil and thiourea (TU) have been found to be effective in breaking bud dormancy in Kenya. This paper is reviewing the challenges encountered in growing apples in the tropics and Kenya in particular and the progress that has made in addressing them.
HortScience
The general doctrine of flowering in Hydrangea macrophylla (Thunb.) Ser. is that floral induction... more The general doctrine of flowering in Hydrangea macrophylla (Thunb.) Ser. is that floral induction occurs during the fall months with the flower appearing the following spring or summer. However, hydrangea cultivars differ widely in their relative abundance and duration of flower production. The objective of this study was to determine how developmental flowering patterns compared among different hydrangea genotypes. Flowering was characterized in 18 cultivars by assessing flower initiation in dormant buds of 1-year-old stems that received natural outdoor inductive conditions. Terminal and lateral buds were dissected and floral developmental stage categorized microscopically. In terminal buds, flower development was very consistent and occurred in 100% of buds for all cultivars except `Ayesha' (33%). In contrast, lateral buds showed a wide variation in flower induction among genotypes. `Ayesha', `Blushing Pink', `Freudenstein', and `Nigra' had 10% or fewer lateral...
Journal of Biological Chemistry
The purification and properties of vitamin D dependent calcium binding proteins were studied in r... more The purification and properties of vitamin D dependent calcium binding proteins were studied in rat intestinal mucosa. Two different vitamin D de pendent calcium binding proteins were fractionated by the DEAE-cellulose column chromatography. Their properties were analyzed with the polyacryl amide gel disc electrophoresis and the sucrose density gradient ultracentrifuga tion. One of them is having a molecular weight about 24,000 representing rapid migration on acrylamide gel electrophoresis and seems similar to the calcium binding protein obtained from chick intestinal mucosa in respect of its size and electrophoretic mobility. The other protein is a larger molecule (mol. wt. 145,000) which is eluted in first fraction from DEAE cellulose chromatogra phy. The smaller molecule of binding protein associates with one atom of calcium per one molecule of protein and the larger molecule would associate with more than 2 atoms of calcium.
Endocrinology
Epidermal growth factor (EGF) has been reported to increase intestinal calcium absorption in suck... more Epidermal growth factor (EGF) has been reported to increase intestinal calcium absorption in suckling rats. The mechanism of this effect is unknown, as are the roles of vitamin D-dependent and independent pathways. The present studies were undertaken to investigate the ability of EGF to accelerate the postnatal induction of the vitamin D-dependent intestinal calcium-binding protein, calbindin-D9k. Subcutaneous administration of EGF increased duodenal calbindin-D9k in suckling rats by more than 100% (P less than 0.001). The effect of EGF was not seen in older weaned animals or when EGF was given to suckling rats by gavage. Administration of EGF simulated the changes of normal development. 1) It increased calbindin-D9k, and the effect was greater in proximal than distal duodenum. 2) EGF increased alkaline phosphatase activity to the same extent in proximal and distal duodenum. 3) EGF increased sucrase more markedly in distal than in proximal epithelium. Maximal and half-maximal effects of EGF on each of these proteins were observed at twice daily doses of 0.1 and 0.04 microgram/g BW, respectively. 4) EGF at the maximally effective dose produced a small (30%) but statistically significant (P less than 0.005) increase in serum 1,25-dihydroxyvitamin D. 5) Most importantly, EGF treatment resulted in a 2-fold increase in intestinal 1,25-dihydroxyvitamin D receptors (VDR) in the proximal segments of the small intestine (P less than 0.001). EGF effects on calbindin-D9k and VDR were specific for the intestine, as EGF did not change kidney calbindin-D9k or kidney VDR. Thus, EGF was able to prematurely initiate a complex series of molecular changes that occur during normal development. The mechanism of EGF's action to stimulate calcium absorption appears to involve a maturation effect on the vitamin D-dependent pathway.
Journal of Biological Chemistry
We have recently demonstrated that O-linked glucosylation of thymine in trypanosome DNA (base J) ... more We have recently demonstrated that O-linked glucosylation of thymine in trypanosome DNA (base J) regulates polymerase II transcription initiation. In vivo analysis has indicated that base J synthesis is initiated by the hydroxylation of thymidine by proteins (JBP1 and JBP2) homologous to the Fe2+/2-oxoglutarate (2-OG)-dependent dioxygenase superfamily where hydroxylation is driven by the oxidative decarboxylation of 2-OG, forming succinate and CO2. However, no direct evidence for hydroxylase activity has been reported for the JBP proteins. We now demonstrate recombinant JBP1 hydroxylates thymine specifically in the context of dsDNA in a Fe2+-, 2-OG-, and O2-dependent manner. Under anaerobic conditions, the addition of Fe2+ to JBP1/2-OG results in the formation of a broad absorption spectrum centered at 530 nm attributed to metal chelation of 2-OG bound to JBP, a spectroscopic signature of Fe2+/2-OG-dependent dioxygenases. The N-terminal thymidine hydroxylase domain of JBP1 is suffic...
Journal of virology, 2005
Adult SJL/J mice are highly susceptible to mouse adenovirus type 1 (MAV-1) infections, whereas ot... more Adult SJL/J mice are highly susceptible to mouse adenovirus type 1 (MAV-1) infections, whereas other inbred strains, including BALB/cJ, are resistant (K. R. Spindler, L. Fang, M. L. Moore, C. C. Brown, G. N. Hirsch, and A. K. Kajon, J. Virol. 75:12039-12046, 2001). Using congenic mouse strains, we showed that the H-2(s) haplotype of SJL/J mice is not associated with susceptibility to MAV-1. Susceptibility of MAV-1-infected (BALB/cJ x SJL/J)F(1) mice was intermediate between that of SJL/J mice and that of BALB/cJ mice, indicating that susceptibility is a genetically controlled quantitative trait. We mapped genetic loci involved in mouse susceptibility to MAV-1 by analysis of 192 backcross progeny in a genome scan with 65 simple sequence length polymorphic markers. A major quantitative trait locus (QTL) was detected on chromosome 15 (Chr 15) with a highly significant logarithm of odds score of 21. The locus on Chr 15 alone accounts for 40% of the total trait variance between susceptib...
Virus Research - VIRUS RES, 1997
The DNA sequence of 9991 nt, corresponding to 18–51 map units of mouse adenovirus type 1 (MAV-1),... more The DNA sequence of 9991 nt, corresponding to 18–51 map units of mouse adenovirus type 1 (MAV-1), was determined, completing the sequence of the Larsen strain of MAV-1. The length of the complete MAV-1 genome is 30 946 nucleotides, consistent with previous experimental estimates. The 18–51 map unit region encodes early region 2B proteins necessary for adenoviral replication as well as late region L1 and L2 structural and packaging proteins. Sequence comparison in this region with human adenoviruses indicates broad similarities, including colinear preservation of all recognized open reading frames (ORFs), with highest amino acid identity occurring in the DNA polymerase and polypeptide III (penton base subunit) ORFs. Virus-assciated (VA) RNA is not encoded in the region where VA RNAs are found in the human adenoviruses, between E2B and L1, nor is it encoded anywhere in the entire MAV-1 genome. The MAV-1 polypeptide III lacks the arginin-glycine-aspartic acid (RGD) motif which is invol...
Journal of Virology, 2013
In recent years, many mumps outbreaks have occurred in vaccinated populations worldwide. The reas... more In recent years, many mumps outbreaks have occurred in vaccinated populations worldwide. The reasons for these outbreaks are not clear. Animal models are needed to investigate the causes of outbreaks and to understand the pathogenesis of mumps virus (MuV). In this study, we have examined the infection of three animal models with an isolate of mumps virus from a recent outbreak (MuV-IA). We have found that while both ferrets and mice generated humoral and cellular immune responses to MuV-IA infection, no obvious signs of illness were observed in these animals; rhesus macaques were the most susceptible to MuV-IA infection. Infection of rhesus macaques via both intranasal and intratracheal routes with MuV-IA led to the typical clinical signs of mumps 2 weeks to 4 weeks postinfection. However, none of the infected macaques showed any fever or neurologic signs during the experimental period. Mumps viral antigen was detected in parotid glands by immunohistochemistry (IHC). Rhesus macaques represent the best animal model for the study of mumps virus pathogenesis.
Journal of …, 2001
Mouse adenovirus type 1 (MAV-1) targets endothelial and monocyte/macrophage cells throughout the ... more Mouse adenovirus type 1 (MAV-1) targets endothelial and monocyte/macrophage cells throughout the mouse. Depending on the strain of mouse and dose or strain of virus, infected mice may survive, become persistently infected, or die. We surveyed inbred mouse strains and found that for the majority tested the 50% lethal doses (LD 50 s) were >10 4.4 PFU. However, SJL/J mice were highly susceptible to MAV-1, with a mean LD 50 of 10 ؊0.32 PFU. Infected C3H/HeJ (resistant) and SJL/J (susceptible) mice showed only modest differences in histopathology. Susceptible mice had significantly higher viral loads in the brain and spleen at 8 days postinfection than resistant mice. Infection of primary macrophages or mouse embryo fibroblasts from SJL/J and C3H/HeJ mice gave equivalent yields of virus, suggesting that a receptor difference between strains is not responsible for the susceptibility difference. When C3H/HeJ mice were subjected to sublethal doses of gamma irradiation, they became susceptible to MAV-1, with an LD 50 like that of SJL/J mice. Antiviral immunoglobulin G (IgG) levels were measured in susceptible and resistant mice infected by an early region 1A null mutant virus that is less virulent that wild-type virus. The antiviral IgG levels were high and similar in the two strains of mice. Taken together, these results suggest that immune response differences may in part account for differences in susceptibility to MAV-1 infection.
HortScience, Jul 1, 2004
Temperate zone fruit crops undergo bud dormancy which can be described as a mechanism for avoidin... more Temperate zone fruit crops undergo bud dormancy which can be described as a mechanism for avoiding the exposure of tender fl owers and leaves to low winter temperatures. In Kenya, apple growing is mostly hampered by inadequate chilling that causes the plants to have prolonged dormancy leading to poor fl owering and consequently low yield. Although the chilling requirements are obligatory, under subtropical and especially tropical conditions avoidance is possible. To achieve this, it is necessary to select cultivars with low chilling requirements. This has proven effective in Zimbabwe with cultivar Matsu which is grown without a need for artifi cial breaking of dormancy. In Kenya like Zimbabwe, low chilling requiring cultivars such as Anna have been grown successfully. However, for cultivars with high chilling requirements, there is need to apply artifi cial techniques/methods to enhance bud break. Some of the cultural techniques used are: defoliation after harvesting and bending of the shoots holizontally. Defoliation after harvesting has particularly been used successfully in the island of Java in Indonesia and it enables two crops to be grown per year. Root chilling of rootstock has also been found to enhance bud break of the shoot. In addition, chemicals like KNO 3 , mineral oil and thiourea (TU) have been found to be effective in breaking bud dormancy in Kenya. This paper is reviewing the challenges encountered in growing apples in the tropics and Kenya in particular and the progress that has made in addressing them.
HortScience
The general doctrine of flowering in Hydrangea macrophylla (Thunb.) Ser. is that floral induction... more The general doctrine of flowering in Hydrangea macrophylla (Thunb.) Ser. is that floral induction occurs during the fall months with the flower appearing the following spring or summer. However, hydrangea cultivars differ widely in their relative abundance and duration of flower production. The objective of this study was to determine how developmental flowering patterns compared among different hydrangea genotypes. Flowering was characterized in 18 cultivars by assessing flower initiation in dormant buds of 1-year-old stems that received natural outdoor inductive conditions. Terminal and lateral buds were dissected and floral developmental stage categorized microscopically. In terminal buds, flower development was very consistent and occurred in 100% of buds for all cultivars except `Ayesha' (33%). In contrast, lateral buds showed a wide variation in flower induction among genotypes. `Ayesha', `Blushing Pink', `Freudenstein', and `Nigra' had 10% or fewer lateral...
Journal of Biological Chemistry
The purification and properties of vitamin D dependent calcium binding proteins were studied in r... more The purification and properties of vitamin D dependent calcium binding proteins were studied in rat intestinal mucosa. Two different vitamin D de pendent calcium binding proteins were fractionated by the DEAE-cellulose column chromatography. Their properties were analyzed with the polyacryl amide gel disc electrophoresis and the sucrose density gradient ultracentrifuga tion. One of them is having a molecular weight about 24,000 representing rapid migration on acrylamide gel electrophoresis and seems similar to the calcium binding protein obtained from chick intestinal mucosa in respect of its size and electrophoretic mobility. The other protein is a larger molecule (mol. wt. 145,000) which is eluted in first fraction from DEAE cellulose chromatogra phy. The smaller molecule of binding protein associates with one atom of calcium per one molecule of protein and the larger molecule would associate with more than 2 atoms of calcium.
Endocrinology
Epidermal growth factor (EGF) has been reported to increase intestinal calcium absorption in suck... more Epidermal growth factor (EGF) has been reported to increase intestinal calcium absorption in suckling rats. The mechanism of this effect is unknown, as are the roles of vitamin D-dependent and independent pathways. The present studies were undertaken to investigate the ability of EGF to accelerate the postnatal induction of the vitamin D-dependent intestinal calcium-binding protein, calbindin-D9k. Subcutaneous administration of EGF increased duodenal calbindin-D9k in suckling rats by more than 100% (P less than 0.001). The effect of EGF was not seen in older weaned animals or when EGF was given to suckling rats by gavage. Administration of EGF simulated the changes of normal development. 1) It increased calbindin-D9k, and the effect was greater in proximal than distal duodenum. 2) EGF increased alkaline phosphatase activity to the same extent in proximal and distal duodenum. 3) EGF increased sucrase more markedly in distal than in proximal epithelium. Maximal and half-maximal effects of EGF on each of these proteins were observed at twice daily doses of 0.1 and 0.04 microgram/g BW, respectively. 4) EGF at the maximally effective dose produced a small (30%) but statistically significant (P less than 0.005) increase in serum 1,25-dihydroxyvitamin D. 5) Most importantly, EGF treatment resulted in a 2-fold increase in intestinal 1,25-dihydroxyvitamin D receptors (VDR) in the proximal segments of the small intestine (P less than 0.001). EGF effects on calbindin-D9k and VDR were specific for the intestine, as EGF did not change kidney calbindin-D9k or kidney VDR. Thus, EGF was able to prematurely initiate a complex series of molecular changes that occur during normal development. The mechanism of EGF's action to stimulate calcium absorption appears to involve a maturation effect on the vitamin D-dependent pathway.
Journal of Biological Chemistry
We have recently demonstrated that O-linked glucosylation of thymine in trypanosome DNA (base J) ... more We have recently demonstrated that O-linked glucosylation of thymine in trypanosome DNA (base J) regulates polymerase II transcription initiation. In vivo analysis has indicated that base J synthesis is initiated by the hydroxylation of thymidine by proteins (JBP1 and JBP2) homologous to the Fe2+/2-oxoglutarate (2-OG)-dependent dioxygenase superfamily where hydroxylation is driven by the oxidative decarboxylation of 2-OG, forming succinate and CO2. However, no direct evidence for hydroxylase activity has been reported for the JBP proteins. We now demonstrate recombinant JBP1 hydroxylates thymine specifically in the context of dsDNA in a Fe2+-, 2-OG-, and O2-dependent manner. Under anaerobic conditions, the addition of Fe2+ to JBP1/2-OG results in the formation of a broad absorption spectrum centered at 530 nm attributed to metal chelation of 2-OG bound to JBP, a spectroscopic signature of Fe2+/2-OG-dependent dioxygenases. The N-terminal thymidine hydroxylase domain of JBP1 is suffic...
Journal of virology, 2005
Adult SJL/J mice are highly susceptible to mouse adenovirus type 1 (MAV-1) infections, whereas ot... more Adult SJL/J mice are highly susceptible to mouse adenovirus type 1 (MAV-1) infections, whereas other inbred strains, including BALB/cJ, are resistant (K. R. Spindler, L. Fang, M. L. Moore, C. C. Brown, G. N. Hirsch, and A. K. Kajon, J. Virol. 75:12039-12046, 2001). Using congenic mouse strains, we showed that the H-2(s) haplotype of SJL/J mice is not associated with susceptibility to MAV-1. Susceptibility of MAV-1-infected (BALB/cJ x SJL/J)F(1) mice was intermediate between that of SJL/J mice and that of BALB/cJ mice, indicating that susceptibility is a genetically controlled quantitative trait. We mapped genetic loci involved in mouse susceptibility to MAV-1 by analysis of 192 backcross progeny in a genome scan with 65 simple sequence length polymorphic markers. A major quantitative trait locus (QTL) was detected on chromosome 15 (Chr 15) with a highly significant logarithm of odds score of 21. The locus on Chr 15 alone accounts for 40% of the total trait variance between susceptib...
Virus Research - VIRUS RES, 1997
The DNA sequence of 9991 nt, corresponding to 18–51 map units of mouse adenovirus type 1 (MAV-1),... more The DNA sequence of 9991 nt, corresponding to 18–51 map units of mouse adenovirus type 1 (MAV-1), was determined, completing the sequence of the Larsen strain of MAV-1. The length of the complete MAV-1 genome is 30 946 nucleotides, consistent with previous experimental estimates. The 18–51 map unit region encodes early region 2B proteins necessary for adenoviral replication as well as late region L1 and L2 structural and packaging proteins. Sequence comparison in this region with human adenoviruses indicates broad similarities, including colinear preservation of all recognized open reading frames (ORFs), with highest amino acid identity occurring in the DNA polymerase and polypeptide III (penton base subunit) ORFs. Virus-assciated (VA) RNA is not encoded in the region where VA RNAs are found in the human adenoviruses, between E2B and L1, nor is it encoded anywhere in the entire MAV-1 genome. The MAV-1 polypeptide III lacks the arginin-glycine-aspartic acid (RGD) motif which is invol...
Journal of Virology, 2013
In recent years, many mumps outbreaks have occurred in vaccinated populations worldwide. The reas... more In recent years, many mumps outbreaks have occurred in vaccinated populations worldwide. The reasons for these outbreaks are not clear. Animal models are needed to investigate the causes of outbreaks and to understand the pathogenesis of mumps virus (MuV). In this study, we have examined the infection of three animal models with an isolate of mumps virus from a recent outbreak (MuV-IA). We have found that while both ferrets and mice generated humoral and cellular immune responses to MuV-IA infection, no obvious signs of illness were observed in these animals; rhesus macaques were the most susceptible to MuV-IA infection. Infection of rhesus macaques via both intranasal and intratracheal routes with MuV-IA led to the typical clinical signs of mumps 2 weeks to 4 weeks postinfection. However, none of the infected macaques showed any fever or neurologic signs during the experimental period. Mumps viral antigen was detected in parotid glands by immunohistochemistry (IHC). Rhesus macaques represent the best animal model for the study of mumps virus pathogenesis.
Journal of …, 2001
Mouse adenovirus type 1 (MAV-1) targets endothelial and monocyte/macrophage cells throughout the ... more Mouse adenovirus type 1 (MAV-1) targets endothelial and monocyte/macrophage cells throughout the mouse. Depending on the strain of mouse and dose or strain of virus, infected mice may survive, become persistently infected, or die. We surveyed inbred mouse strains and found that for the majority tested the 50% lethal doses (LD 50 s) were >10 4.4 PFU. However, SJL/J mice were highly susceptible to MAV-1, with a mean LD 50 of 10 ؊0.32 PFU. Infected C3H/HeJ (resistant) and SJL/J (susceptible) mice showed only modest differences in histopathology. Susceptible mice had significantly higher viral loads in the brain and spleen at 8 days postinfection than resistant mice. Infection of primary macrophages or mouse embryo fibroblasts from SJL/J and C3H/HeJ mice gave equivalent yields of virus, suggesting that a receptor difference between strains is not responsible for the susceptibility difference. When C3H/HeJ mice were subjected to sublethal doses of gamma irradiation, they became susceptible to MAV-1, with an LD 50 like that of SJL/J mice. Antiviral immunoglobulin G (IgG) levels were measured in susceptible and resistant mice infected by an early region 1A null mutant virus that is less virulent that wild-type virus. The antiviral IgG levels were high and similar in the two strains of mice. Taken together, these results suggest that immune response differences may in part account for differences in susceptibility to MAV-1 infection.