Initiation of feeding by provisioned patas monkeys: Evidence for the protection hypothesis

The applicability of the baboon-based protection hypothesis was tested with data from a provisioned, free-ranging group of Erythrocebus patas.The age/sex class of the individual which first approached and fed from one of the food hoppers during early morning feeding sessions was noted for 114 mornings. The presence of an observer, and periodically, rhesus monkeys,near the hopper made these approaches analogous to progressions described for feral baboons. Adult patas of both sexes approached and ate first significantly more frequently than was expected based on their respective proportions in the group, and immature monkeys less often. For adult females,initiating feeding was not correlated with dominance rank, although females in the middle and lower thirds of the hierarchy (n = 6 in each third) initiated feeding more frequently than did the females in the top third. The protection hypothesis accounts for the observed behavioral pattern, while explanations based on competitive exclusion and dominance relationships do not adequately account for the results.     

The Bulk Isolation of Oligodendroglia from Whole Rat Forebrain: A New Procedure Using Physiologic Media

Abstract: A method for the isolation of oligodendroglia from undissected rat forebrain is described. The method has been applied to brains from 10-, 30- and 60-day-old rats. The procedure uses a balanced salt solution at pH 7.2 throughout. Tissue is briefly exposed to trypsin and DNase and dissociated and the cells are purified on a discontinuous sucrose gradient. The isolates were composed of 90% phase-bright rounded cells having diameters after fixation of 7-12 μm. The contamination was primarily by red blood cells and phase-dark nuclei. Neurons and astroglia were lysed by the procedure. The method is reproducible and should be applicable to other ages of rat or to other species. The cells have been examined by light and electron microscopy and analyzed for protein and nucleic acids. None of the cell parameters measured, including total protein (58 pg/cell), varied significantly with age. With this new method it should be possible to carry out studies on the development and metabolism of oligodendroglia in small laboratory animals.     

Induction of apoptosis in fibroblasts by c-myc protein.

Although Rat-1 fibroblasts expressing c-myc constitutively are unable to arrest growth in low serum, their numbers do not increase in culture because of substantial cell death. We show this cell death to be dependent upon expression of c-myc protein and to occur by apoptosis. Regions of the c-myc protein required for induction of apoptosis overlap with regions necessary for cotransformation, autoregulation, and inhibition of differentiation, suggesting that the apoptotic function of c-myc protein is related to its other functions. Moreover, cells with higher levels of c-myc protein are more prone to cell death upon serum deprivation. Finally, we demonstrate that deregulated c-myc expression induces apoptosis in cells growth arrested by a variety of means and at various points in the cell cycle.     

Down-regulation of cellular proto-oncogenes during inhibition of rat parotid acinar cell proliferation.

The role of cell surface galactosyltransferase in mediating isoproterenol-induced parotid gland hypertrophy and hyperplasia was examined in rat parotid gland acinar cells. Introduction of the transferase modifier, alpha-lactalbumin, or galactosyltransferase-associated kinase inhibitor trifluoperazine, into beta-agonist-treated rats prevented acinar cell proliferation as determined by [3H]thymidine incorporation after 96 h of treatment. However, [3H]thymidine incorporation into DNA after 24 h of treatment, with injection of a combination of isoproterenol/alpha-lactalbumin or isoproterenol/trifluoperazine, was similar to injections of isoproterenol alone; suggesting that acinar cells could be stimulated to undergo a single round of DNA synthesis. Northern blot analysis of myc and fos expression followed a similar pattern of down-regulation to control levels after 96 h but not after 24 h. Hybridization with erb B showed little change with proliferation, confirming previous observations on protein levels of the EGF-receptor in acinar cells. Western blot analysis of nuclear protein expression of myc revealed that isoproterenol caused an increase in a 62-kDa protein which was again down-regulated with inhibition of cell proliferation. Analysis of protein levels of Rb110 protein showed no change in protein level in the nucleus with cell proliferation, but did show an associated increase in protein phosphorylation in response to growth stimulation.     

Motherless mothers revisited: Rhesus maternal behavior and rearing history

Classic studies have demonstrated that isolation- and peer-rearing in infancy can result in overt deficits in maternal behavior in rhesus monkeys, although nonmother-reared monkeys may become adequate caretakers if allowed experience with infants. Maternal styles in normally-reared mothers have been reported to vary widely. In the present study, the range of maternal proficiency of nonabusive, nonrejecting nonmother-reared mothers was examined. The behavior of mother-reared, peer-reared, and isolate-reared multiparous mothers was observed and compared for the first six months following parturition. Both peer-reared and isolate-reared mothers exhibited differences in maternal behavior from mother-reared mothers. Inasmuch as variations in maternal behavior may impact on the infant, investigators should be aware of the rearing histories of females used as breeders in the laboratory.     

EFFECTS OF THALLIUM SALTS ON NEURONAL MITOCHONDRIA IN ORGANOTYPIC CORD-GANGLIA-MUSCLE COMBINATION CULTURES

A functionally coupled organotypic complex of cultured dorsal root ganglia, spinal cord peripheral nerve, and muscle has been employed in an experimental approach to the investigation of the neurotoxic effects of thallium. Selected cultures, grown for up to 12 wk in vitro, were exposed to thallous salts for periods ranging up to 4 days. Cytopathic effects were first detected after 2 h of exposure with the appearance of considerably enlarged mitochondria in axons of peripheral nerve fibers. With time, the matrix space of these mitochondria became progressively swollen, transforming the organelle into an axonal vacuole bounded by the original outer mitochondrial membrane. Coalescence of adjacent axonal vacuoles produced massive internal axon compartments, the membranes of which were shown by electron microprobe mass spectrometry to have an affinity for thallium. Other axoplasmic components were displaced within a distended but intact axolemma. The resultant fiber swelling caused myelin retraction from nodes of Ranvier but no degeneration. Impulses could still propagate along the nerve fibers throughout the time course of the experiment. Comparable, but less severe changes were seen in dorsal root ganglion neurons and in central nerve fibers. Other cell types showed no mitochondrial change. It is uncertain how these findings relate to the neurotoxic effects of thallium in vivo, but a sensitivity of the nerve cell and especially its axon to thallous salts is indicated.     

Metabolism of c-myc gene products: c-myc mRNA and protein expression in the cell cycle.

The presence and synthesis of c-myc protein and mRNA in the cell cycle has been studied. We find that c-myc mRNA is present, at equivalent levels, at all times in the cell cycle with the possible exception of mitosis. Furthermore, we demonstrate that this mRNA is transcribed in both G1 and G2 phases. An analysis of the c-myc protein in vivo shows that de novo synthesis occurs in G1 and G2 and the protein turns over with a half-life of approximately 20-30 min in both phases. Furthermore, the level of c-myc protein rapidly increases in cell populations when they re-initiate the cell cycle, thereafter decreasing as the culture reaches quiescence. The results therefore suggest that expression of c-myc can be rapidly modulated and that it is activated during the G0 to G1 transition, but is expressed thereafter in the cell cycle.     

Studies on the interaction of the human c-myc protein with cell nuclei: p62c-myc as a member of a discrete subset of nuclear proteins

We have analyzed the localization of the human c-myc product (p62c-myc) at steady state in cells by immunoprecipitation and immunoblotting. We show that p62c-myc is extracted from nuclei by mild salt concentrations (below 200 mM), without affecting gross nuclear structure or causing extraction of major chromatin components. We observe no association between p62c-myc and the nuclear matrix. We also demonstrate that p62c-myc is a member of a discrete subset of nuclear proteins that are all rendered irreversibly insoluble in situ by exposure of isolated nuclei to physiological temperatures (37 degrees C). p62c-myc is sequestered into a similar insoluble complex in cells that have been subjected to heat shock. Finally, we show that avian v-myc and v-myb proteins in isolated nuclei also become insoluble after exposure to temperatures above 37 degrees C. We discuss the possible implications of these results.     

Sexual resurgence and possible induction of reproductive synchrony in a captive group of orangutans

In April 1985, a 22-year-old group-living female orangutan gave birth to her second infant, marking an interbirth interval of 12 years, 2 months. The timing and patterning of sexual activity displayed by the group of two females and one male over a 3-year period were analyzed to identify variables that might account for this female's sexual resurgence. Variables considered were (1) movement to a new habitat, (2) opening of a vaginal stricture, (3) addition of a second female to the group, (4) male sexual resurgence, and (5) copulatory synchrony. None of these variables alone could account for the resurgence of fertility, although several of them account for the increase in copulatory frequency. This suggests that a combination of factors may be operating, including the induction of fertility via the presence of another cycling female. This induction effect has been described for rhesus macaques, and since this orangutan group meets the conditions necessary for such an induction effect, it is offered as another possible variable influencing fertility. Indices of pregnancy determination, as they relate to gestation lengths and prematurity of infants, also are evaluated and compared.