Water Content, Raffinose, and Dehydrins in the Induction of Desiccation Tolerance in Immature Wheat Embryos

Desiccation tolerance is initiated in wheat (Triticum aestivum L.) embryos in planta at 22 to 24 d after anthesis, at the time that the embryo water content has decreased from about 73% fresh weight (2.7 g water/g dry weight) to about 65% fresh weight (1.8 g water/g dry weight). To determine if desiccation tolerance is fully induced by the loss of a relatively small amount of water, detached wheat grains were treated to reduce the embryo water content by just a small amount to approximately 69% (2.2 g water/g dry weight). After 24 h of such incipient water loss, subsequently excised embryos were able to withstand severe desiccation, whereas those embryos that had not previously lost water could not. Therefore, a relatively small decrease in water content for only 24 h acts as the signal for the development of desiccation tolerance. Embryos that were induced into tolerance by a 24-h water loss had no detectable raffinose. The oligosaccharide accumulated at later times even in embryos of detached grains that had not become desiccation tolerant, although tolerant embryos (i.e. those that previously had lost some water) contained larger amounts of the carbohydrate. It is concluded that desiccation tolerance and the occurrence of raffinose are not correlated. Immunodetected dehydrins accumulated in embryos in planta as desiccation tolerance developed. Detachment of grains induced the appearance of dehydrins at an earlier age, even in embryos that had not been made desiccation tolerant by incipient drying. It is concluded that a small reduction in water content induces desiccation tolerance by initiating changes in which dehydrins might participate but not by their interaction with raffinose.     

CnOtx, a member of the Otx gene family, has a role in cell movement in hydra.

Otx genes have been identified in a variety of organisms and are commonly associated with the patterning of anterior structures. In some vertebrates, Otx genes are also expressed in the prechordal mesoderm, where they may have a role in cell movement. Here we report the characterization of CnOtx, an Otx gene in hydra, thereby providing evidence that Otx genes appeared early in metazoan evolution. CnOtx is expressed at high levels in developing buds and aggregates, where it appears to have a role in the cell movements that are involved in the formation of new axes. Further, the gene is expressed at a low level throughout the body column of hydra. This latter pattern may reflect a role for CnOtx in specifying tissue as competent to be anterior, although the gene does not have a direct role in the formation of the head.     

Expression of CD134 (0X-40) on T cells during the first 100 days following allogeneic bone marrow transplantation as a marker for lymphocyte activation and therapy-resistant graft-versus-host disease.

CD134 (OX-40) is an activation-associated antigen which functions as a costimulatory receptor for CD4+ T cells. In order to determine the expression of CD134 during immune recovery following allogeneic bone marrow transplantation (BMT), we measured its expression on T cells and T cell subsets during the first 100 days following BMT in 26 patients. CD4+CD134+ T could be seen approximately 14 days following BMT cells in patients who did not develop GvHD which required therapy (n = 20). The percentage of CD4+CD134+ cells continued to increase up to the fourth week following BMT to a maximum of 40-50% of CD4+ T cells (normal = 1-8%). Two patients who developed Grade I-II GvHD and who responded to treatment with pulsed high-dose methylprednisolone (MPD) showed a decline of approximately 40% in CD4+CD134+ T cells was seen within 48 hours of treatment. Four patients who developed GvHD that was not responsive to MPD and who later developed high IV GvHD showed increasing CD4+CD134+ T cells up to 85% of the CD4+ T cells. Additionally, rapid increases in CD134+ T cells following antibody-based T cell therapy were associated with GvHD recurrence. In no cases was the percentage of CD134+ CD4+ T cells predictive of clinical GvHD. In this exploratory study, we have shown that CD134, although not predictive of the initial onset of GvHD, may be a useful tool for monitoring the response to early GvHD therapy and identification of patients at risk for reemergence of GvHD who may benefit from anti-T cell therapy. Cytometry (Comm. Clin. Cytometry) 38: 238-243, 1999.     

Androgen-metabolizing enzymes show region-specific changes across the breeding season in the brain of a wild songbird.

The Lapland longspur (Calcarius lapponicus) is an arctic-breeding songbird that shows rapid behavioral changes during a short breeding season. Changes in plasma testosterone (T) in the spring are correlated with singing but not territorial aggression in males. Also, T treatment increases song but not aggression in this species. In contrast, in temperate-zone breeders, song and aggression are highly correlated, and both increase after T treatment. We asked whether regional or temporal differences in androgen-metabolizing enzymes in the longspur brain explain hormone-behavior patterns in this species. We measured the activities of aromatase, 5alpha-reductase and 5beta-reductase in free-living longspur males. Aromatase and 5alpha-reductase convert T into the active steroids 17beta-estradiol (E(2)) and 5alpha-dihydrotestosterone (5alpha-DHT), respectively. 5beta-Reductase deactivates T via conversion to 5beta-DHT, an inactive steroid. We examined seven brain regions at three stages in the breeding season. Overall, aromatase activity was high in the hypothalamus, hippocampus, and ventromedial telencephalon (containing nucleus taeniae, the avian homologue to the amygdala). 5beta-Reductase activity was high throughout the telencephalon. Activities of all three enzymes changed over time in a region-specific manner. In particular, aromatase activity in the rostral hypothalamus was decreased late in the breeding season, which may explain why T treatment at this time does not increase aggression. Changes in 5beta-reductase do not explain the effects of plasma T on aggressive behavior.     

Differences in the dynamics of the tandem‐SH2 modules of the Syk and ZAP‐70 tyrosine kinases

The catalytic activity of Syk‐family tyrosine kinases is regulated by a tandem Src homology 2 module (tSH2 module). In the autoinhibited state, this module adopts a conformation that stabilizes an inactive conformation of the kinase domain. The binding of the tSH2 module to phosphorylated immunoreceptor tyrosine‐based activation motifs necessitates a conformational change, thereby relieving kinase inhibition and promoting activation. We determined the crystal structure of the isolated tSH2 module of Syk and find, in contrast to ZAP‐70, that its conformation more closely resembles that of the peptide‐bound state, rather than the autoinhibited state. Hydrogen–deuterium exchange by mass spectrometry, as well as molecular dynamics simulations, reveal that the dynamics of the tSH2 modules of Syk and ZAP‐70 differ, with most of these differences occurring in the C‐terminal SH2 domain. Our data suggest that the conformational landscapes of the tSH2 modules in Syk and ZAP‐70 have been tuned differently, such that the autoinhibited conformation of the Syk tSH2 module is less stable. This feature of Syk likely contributes to its ability to more readily escape autoinhibition when compared to ZAP‐70, consistent with tighter control of downstream signaling pathways in T cells.     

Food consumption and retention time in captive whooping cranes (Grus americana)

Food consumption, digesta retention time, and food preference were measured for captive whooping cranes fed pelleted diets. The basal commercial diet was compared to four mixtures containing 70% basal and 30% of one of four important winter foods for the whooping crane: blue crab (Callinectes sapidus), wolfberry fruit (Lycium carolinianum), live oak acorn (Quercus virginiana), or common Rangia clam (Rangia cuneata). Because captive birds would not eat whole foods, we were prevented from direct food preference tests. Food passed through the gut rapidly, with almost complete elimination within 7 hr. There was some indication that retention time was shorter for the low fiber and high ash and calcium clam diet. Cranes ate less wolfberry feed (g/day) than the other feeds, and all birds ate less wolfberry feed on the day it was first fed, compared to basal diet the previous day. Birds ate more low energy feed than high energy feed. Due to combined effects of low energy content, lower metabolizable energy coefficients, and reduced feed consumption, less energy was assimilated for study diets than basal diet. Apparent shorter retention times for some diets containing whooping crane foods may partly explain lower digestibilities and metabolizable energy of winter whooping crane foods compared to commercial crane diet. Zoo Biol 16:519–531, 1997. © 1997 Wiley-Liss, Inc.     

Molecular and immunogenetic analysis of major histocompatibility haplotypes in northern bobwhite enable direct identification of corresponding haplotypes in an endangered subspecies,the masked bobwhite

The major histocompatibility complex (MHC) is a group of genetic loci coding for haplotypes that have been associated with fitness traits in mammals and birds. Such associations suggest that MHC diversity may be an indicator of overall genetic fitness of endangered or threatened species. The MHC haplotypes of a captive population of 12 families of northern bobwhites (Colinus virginianus) were identified using a combination of immunogenetic and molecular techniques. Alloantisera were produced within families of northern bobwhites and were then tested for differential agglutination of erythrocytes of all members of each family. The pattern of reactions determined from testing these alloantisera identified a single genetic system of alloantigens in the northern bobwhites, resulting in the assignment of a tentative genotype to each individual within the quail families. Restriction fragment patterns of the DNA of each bird were determined using the chicken MHC B‐G cDNA probe bg11. The concordance between the restriction fragment patterns and the alloantisera reactions showed that the alloantisera had identified the MHC of the northern bobwhite and supported the tentative genotype assignments, identifying at least 12 northern bobwhite MHC haplotypes. Eighteen northern bobwhite alloantisera were then used to detect a minimum of 17 masked bobwhite MHC haplotypes. Subsequent restriction fragment pattern analyses using cDNA probes for chicken MHC genes were in agreement with agglutination patterns displayed by the antisera, showing that the immunogenetically identified alloantigen system constituted the MHC of the masked bobwhite. These data demonstrate that a non‐endangered species may be used to provide antisera for differentiating MHC haplotypes in a closely related endangered species, thus providing a practical basis for long‐range monitoring of MHC haplotypes of birds surviving in their native habitats. Zoo Biol 18:279–294, 1999. © 1999 Wiley‐Liss, Inc.     

Androgen‐metabolizing enzymes show region‐specific changes across the breeding season in the brain of a wild songbird

The Lapland longspur (Calcarius lapponicus) is an arctic‐breeding songbird that shows rapid behavioral changes during a short breeding season. Changes in plasma testosterone (T) in the spring are correlated with singing but not territorial aggression in males. Also, T treatment increases song but not aggression in this species. In contrast, in temperate‐zone breeders, song and aggression are highly correlated, and both increase after T treatment. We asked whether regional or temporal differences in androgen‐metabolizing enzymes in the longspur brain explain hormone‐behavior patterns in this species. We measured the activities of aromatase, 5α‐reductase and 5β‐reductase in free‐living longspur males. Aromatase and 5α‐reductase convert T into the active steroids 17β‐estradiol (E₂) and 5α‐dihydrotestosterone (5α‐DHT), respectively. 5β‐Reductase deactivates T via conversion to 5β‐DHT, an inactive steroid. We examined seven brain regions at three stages in the breeding season. Overall, aromatase activity was high in the hypothalamus, hippocampus, and ventromedial telencephalon (containing nucleus taeniae, the avian homologue to the amygdala). 5β‐Reductase activity was high throughout the telencephalon. Activities of all three enzymes changed over time in a region‐specific manner. In particular, aromatase activity in the rostral hypothalamus was decreased late in the breeding season, which may explain why T treatment at this time does not increase aggression. Changes in 5β‐reductase do not explain the effects of plasma T on aggressive behavior. © 1999 John Wiley & Sons, Inc. J Neurobiol 41: 176–188, 1999     

Cortical bone mapping: An application to hand and foot bones in hominoids

Bone form reflects both the genetic profile and behavioural history of an individual. As cortical bone is able to remodel in response to mechanical stimuli, interspecific differences in cortical bone thickness may relate to loading during locomotion or manual behaviours during object manipulation. Here, we test the application of a novel method of cortical bone mapping to the third metacarpal (Mc3) and talus of Pan, Pongo, and Homo. This method of analysis allows measurement of cortical thickness throughout the bone, and as such is applicable to elements with complex morphology. In addition, it allows for registration of each specimen to a canonical surface, and identifies regions where cortical thickness differs significantly between groups. Cortical bone mapping has potential for application to palaeoanthropological studies; however, due to the complexity of correctly registering homologous regions across varied morphology, further methodological development would be advantageous.     

Transient brain ischemia: NMDA receptor modulation and delayed neuronal death

Transient global ischemia induces delayed neuronal death in certain cell types and brain regions while sparing cells in other areas. A key process through which oxygen-glucose deprivation triggers cell death is the excessive accumulation of the neurotransmitter glutamate leading to over excitation of neurons. In certain neurons this increase in glutamate will potentiate the NMDA type of glutamate receptor, which can then initiate cell death. This review provides an update of the neurophysiological, cellular and molecular mechanisms inducing post-ischemic plasticity of NMDA receptors, focusing on the sensitive CA1 pyramidal neurons in the hippocampus as compared to the relatively resistant neighboring CA3 neurons. Both a change in the equilibrium between protein tyrosine kinases/phosphatases and an increased density of surface NMDA receptors in response to ischemia may explain the selective vulnerability of specific cell types. Implications for the treatment of stroke and reasons for the failures of human clinical trials utilizing NMDA receptor antagonists are also discussed.