The gross anatomy,cellular structure,and fatty acid composition of adipose tissue in captive polar bears (Ursus maritimus)

The gross anatomy, microscopic structure, and fatty acid composition of adipose tissue in four elderly polar bears (Ursus maritimus), that had each been in captivity for more than 24 years, were compared with that of young wild specimens. Total dissections were performed on two specimens. In both, the proportion of adipose tissue in the body was similar to that of younger wild bears, but the total adipocyte complement was smaller than that of the wild bears in one specimen, and within the normal range in the other. There was proportionately more intra-abdominal adipose tissue, particularly in the inner ventral wall of abdomen depot, in which the number of adipocytes was substantially greater than expected. The fatty acid composition of the triacylglycerols differed substantially from that of the wild bears, reflecting their diet of fish, domesticated herbivores, bread, and fruit, but there were also significant differences between cage-mates eating similar diets. © 1993 Wiley-Liss, Inc.     

Water relations parameters and tissue development in somatic and zygotic embryos of three pinaceous conifers

There is increasing interest in using somatic embryogenesis to meet the demand for high quality seedlings. However, in vitro production of propagules on a large scale depends on the optimization of the maturation and germination steps promoted by desiccation and subsequent imbibition of the embryo, respectively. It is therefore important to characterize zygotic and somatic embryos in terms of their water relations. Bound water, elastic modulus, osmotic potential at full turgor, and relative water content at turgor loss point were determined for somatic and zygotic embryos of western larch and loblolly pine and somatic embryos of white spruce at two developmental stages. These water relations parameters were derived from water-release curves obtained by suspending tissue samples in sealed vials over unsaturated NaCl solutions of known water potential. There was little difference in water relations parameters among species but marked stage dependency for bound water and elastic modulus. The amount of bound water was lowest in western larch somatic embryos (0.02-0.07) and highest in zygotic loblolly pine embryos (0.10-0.18). Elastic modulus ranged from 2.5 to 6.2 MPa in somatic embryos but varied between 1.4 and 1.8 MPa in zygotic embryos. The osmotic potential was lower in somatic embryos than in their zygotic counterparts. Our results show that water relations parameters are remarkably conservative across species but that, within a given species, these parameters are stage specific. It would seem, therefore, that desiccation protocols might be developed for a given developmental stage and applied across a range of species without the confounding effects of differences in water relations parameters.     

Stable-Carbon-Isotope Composition of Fatty Acids in Hydrothermal Vent Mussels Containing Methanotrophic and Thiotrophic Bacterial Endosymbionts

Fatty acid biomarker analysis coupled with gas chromatography-isotope ratio mass spectrometry was used to confirm the presence of methanotrophic and thiotrophic bacterial endosymbionts in the tissues of a hydrothermal vent mussel (Bathymodiolus sp.), collected from the Menez Gwen vent field on the mid-Atlantic ridge. Monounsaturated (n-8) fatty acids, which are diagnostic of methanotrophic bacteria, were detected in all three types of tissues examined (gill, posterior adductor, and mantle), although levels were highest in gill tissues where the bacteria were found. Stable-carbon-isotope compositions (δ-¹³C per mille relative to that of Peedee belemnite) of fatty acids for all three tissues ranged from −24.9 to −34.9‰, which encompasses the range predicted for both thiotroph- and methanotroph-based nutrition. The data suggest that these thio- and methanotrophic bacterial endosymbionts are equally important in the nutrition of the vent mussel at this particular vent site.     

Effect of dietary Ca and Cd level of pregnant rats on reproduction and on dam and progeny tissue mineral concentrations.

Pregnant Sprague-Dawley rats were used to determine the effects of the addition of 200 ppm of Cd (as CdCl2) to the diet factorially with two levels of dietary Ca (0.07% and 0.96%) on reproductive performance, concentrations of Cd, Cu, Fe, Zn, Ca and Mg in dam liver and kidney and in newborn progeny. High Cd significantly increased liver and kidney Cd, Zn and Ca and decreased liver Fe. High dietary Ca partially protected against accumulation of Cd in liver and kidney but had no effect on concentration of other elements. Number of live or stillborn pups per litter was not significantly affected by diet but high Cd significantly reduced pup birth weight. No grossly abnormal pups were noted. Concentration of Cd in bodies of newborn pups was increased approximately 8.6-fold by high Cd in the diet of dams fed the 0.07% Ca-diet and 3.8-fold by high-Cd in the diet of dams fed the 0.96% Ca diet. Pup, Zn, Cu and Fe contents were significantly decreased and Ca was significantly increased by high-Cd in the maternal diet whereas pup Mg content was unchanged. Maternal Ca intake had no effect on concentration of Zn, Cu, Fe or Ca in newborn pups. The biological importance of the alteration in maternal and fetal tissue concentration of Zn, Cu and Fe by high-Cd maternal diets is unknown.     

Sarcocystis in free-ranging herbivores on the National Bison Range.

Heart, esophagus, diaphragm and skeletal muscle obtained from various herbivores on the National Bison Range were examined grossly for Sarcocystis. Sarcocystis was found in 81, 50, 50, and 13% of the mule deer, (Odocoileus hemionus), white-tailed deer (O. virginianus), elk (Cervus elaphus), and bison (Bison bison), respectively.     

Assessment of the downstream portion of the mitochondrial pathway of caspase activation in patients with acute myeloid leukemia

Most chemotherapeutic agents used in the treatment of acute myeloid leukemia (AML) induce apoptosis by triggering the mitochondrial pathway of caspase activation. To investigate the downstream portion of the mitochondrial pathway of caspase activation in patients with AML, cytosolic lysates were stimulated with cytochrome c and dATP and hydrolysis of Ac-DEVD-AFC by effector caspases was measured. Defects in the distal mitochondrial pathway were more common in samples from patients with AML that relapsed rapidly after induction chemotherapy compared to samples from treatment naïve patients. The incidence of blocked pathways did not differ based on response to induction chemotherapy, as even nonresponders generally had an intact pathway. When the distal mitochondrial pathway was blocked, defects were usually at the level of the effector caspases. Thus, functional defects in the distal portion of the mitochondrial pathway of caspase activation may help explain the nature of response and relapse after treatment.     

Datamonkey: rapid detection of selective pressure on individual sites of codon alignments

Datamonkey is a web interface to a suite of cutting edge maximum likelihood-based tools for identification of sites subject to positive or negative selection. The methods range from very fast data exploration to the some of the most complex models available in public domain software, and are implemented to run in parallel on a cluster of computers. AVAILABILITY: http://www.datamonkey.org. In the future, we plan to expand the collection of available analytic tools, and provide a package for installation on other systems.     

Site-to-site variation of synonymous substitution rates

We develop a new model for studying the molecular evolution of protein-coding DNA sequences. In contrast to existing models, we incorporate the potential for site-to-site heterogeneity of both synonymous and nonsynonymous substitution rates. We demonstrate that within-gene heterogeneity of synonymous substitution rates appears to be common. Using the new family of models, we investigate the utility of a variety of new statistical inference procedures, and we pay particular attention to issues surrounding the detection of sites undergoing positive selection. We discuss how failure to model synonymous rate variation in the model can lead to misidentification of sites as positively selected.     

Genetic response ofAntirrhinum majus to acute and chronic plant irradiation

Summary Clonal lines ofAntirrhinum majus heterozygous for flower color have been used to study somatic mutations induced by irradiating plants with chronic gamma rays from cobalt-60 and acute X rays. Pink or white flecks and sectors of various sizes on the purple flowers are interpreted as resulting from mutational events at different times in flower development.Acute X-ray treatment of pre-flowering stages caused no visible change in flowers opening prior to the 15th day thereafter. On the 16th to 19th days there was dense mottling, and by the 20th or 21st day numerous eight-cell mutant spots could be counted. The number of spots induced by 1,000 r of X rays was used to obtain a preliminary estimate of an average mutation rate for the three genes studied of 6.33×10^–6 per cell per roentgen.Chronic irradiation in a gamma radiation field and greenhouse showed a linear response of mutation rate to daily dose rate, the actual rate being subject to seasonal variation. There were occasional indications of non-linearity but further tests have failed to show any significantly higher mutagenic efficiency of dose rates below 6 r/day.In plants removed from chronic gamma irradiation the frequency of mutation spots returns to the spontaneous level after about six weeks. The appearance, however, of mutant sectors on plants several months after exposure to both acute and chronic radiation indicates the induction of persistent genetic changes. Progeny tests of seeds and cuttings are planned to test the nature of these genetic events.With 6 Figures in the TextResearch carried out at the Brookhaven National Laboratory under the auspices of the U.S. Atomic Energy Commission.