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Biomedical subjects

K R Brizzee

Publications and source records attributed to K R Brizzee.

At least 37 records · Page 2Linked to original sources
PubMed1979

Motion sickness-induced food aversions in the squirrel monkey.

Conditioned aversions to colored, flavored water were established in Squirrel monkeys (Saimiri sciureus) by following consumption with 90 min of simultaneous rotational and vertical stimulation. The experimental group (N = 13) drank significantly less of the green, almond-flavored test solution than did the control group (N = 14) during three post-treatment preference testing days. Individual differences were noted in that two experimental monkeys readily drank the test solution after rotational stimulation. Only two of the experimental monkeys showed emesis during rotation, yet 10 monkeys in this group developed an aversion. These results that (1) motion sickness can be readily induced in Squirrel monkeys with simultaneous rotational and vertical stimulation and (2) that conditioned food aversions are achieved in the absence of emesis in this species.

Animals↗
PubMed1979

Age pigments, cell loss and hippocampal function.

The specific aims of this study were to perform direct correlational analyses of age differences in learning, short-term memory and arousal in relation to cell loss and lipofuscin increase in the hippocampus CA1 zone and in visual area 17 of the Fisher 344 rat. The following tentative conclusions can be made from the results presented in this study: (1) significant age differences in 2 and 6 hour passive-avoidance retention or memory between mature and old rats were related to non-significant age differences in days to criterion learning, starting latencies, running distance and time in original approach learning, and (2) significant age differences in 2 and 6 hours retention of old, compared to mature rats were correlated significantly with loss of neurons, and very significantly with increases in intraneuronal lipofuscin in the hippocampus CA1 zone and in visual area 17.

Aggression↗
PubMed1979

Comparative normal levels of serum triiodothyronine and thyroxine in nonhuman primates.

Normative values were obtained for triiodothyronine and thyroxine from four species of Old World primate (chimpanzees, rhesus monkeys, African green monkeys and talopoin monkeys) and a single species of New World primate (squirrel monkeys) represented by two subspecies, Colombian and Bolivian. The Bolivian squirrel monkeys exhibited the lowest values for both triiodothyronine and thyroxine. Male talapoins had the highest levels of thyroxine. Significant differences were found in levels of triiodothyronine and thyroxine between males and females of the same species and between the two subspecies of squirrel monkeys. Triiodothyronine:thryroxine ratios were consistently lower in the males of all species examined.

Animals↗
PubMed1979

The growth and development of the squirrel monkey (Saimiri Sciureus).

Squirrel monkeys of 2 subspecies, Bolivian and Colombian, were removed from their mothers on the day of birth and nursery reared for up to 2 years of age. Infants were tested weekly for 12 weeks, then monthly for 1 year, and at 2 years of age. Tests included morphology (body weight, crown-rump length, and head measurements), behavior (reflexes, activity, reaction to the surrogate), and physiology (heart rate, respiratory rate, temperature and optokinetic nystagmus). Data show some likenesses and some differences between the 2 subspecies.

Animals↗
PubMed1978

Effects of systemic administration of 6-hydroxydopamine on the circumventricular organs in nonhuman primates. I. Area postrema.

6-Hydroxydopamine (6-OH-DA) has been shown to produce degenerative changes in noradrenergic nerve terminals and preterminals in the CNS following intracisternal, intraventricular or direct injection into the brain parenchyma. Systemic injection of 6-OH-DA is known to result in degenerative changes in noradrenergic terminals in the peripheral nervous system. However, only a few studies have been carried out on the effects of systemic injections of 6-OH-DA on noradrenergic terminals in the CNS. In the present study cynomolgus and squirrel monkeys were injected intravenously on two successive days with total doses of 350 mg/kg and 150 mg/kg of 6-OH-DA, respectively, and sacrificed at 2 and 24 h following the second injection. Degenerative changes in the area postrema (AP) neurons in all injected animals were characterized by a generalized increase in electron density of cytoplasmic elements in axonal terminals and preterminals. Multilamellar bodies, clusters of clear and dense core vesicles, increased numbers of secondary lysosomes, and an increase in the number of glycogen increased markedly in injected animals, but no other glial alterations were observed. The number of mast cells in the AP was greater in injected than in noninjected animals, both in the perivascular spaces (PVS) and in parenchymal locations. Cell processes in the PVS were occasionally observed to contain electron dense bodies, and degenerative changes were seen in supraependymal processes in some injected animals.

Animals↗
PubMed1978

Age differences in short-term memory and cell loss in the cortex of the rat.

Studies with human and animal subjects have indicated age declines in short-term memory and cell loss in the cortex. Cell loss has been estamated by descriptive nonautomated methods. Declines in short-term memory may be related to reduced learning, movtivation, motor capacity, or some combination of these factors. Passive-avoidance tests of memory minimize these factors. Direct correlational studies on learning and memory in relation to cell loss in the same subject are not feasible in man and they have not been reported previously in animals. The aims of this study were to examine age differences in learning and short-term passive-avoidance memory in relation to cell packing density in the visual cortex of the Fisher 344 rat. Cell counts were made with a computer-guided, automated, image-analyzing system (TAS, Leitz). The following observations were made: (1) significant age differences in 2- and 6-hour short-term passive-avoidance retention or memory between mature and senescent rats were related to nonsignificant age differences in original learning inferred from starting latencies, running time and running distance and (2) sd compared to mature rats were associated with significant differences in neuron but not glia-vascular cell density in area 17 in the presence of nonsignificant age differences in cortical depth and brain weight. Aims of further studies are to establish the role of cell loss from the hippocampus in loss of short-term spatial memory with age and to develop criteria for differential counting of small neurons, glia, endothelial cells and pericytes.

Aging↗
PubMed1977

Ultrastructure of the feline area postrema.

The morphology of the feline area posterma (AP), a circumventricular organ, has been studied by scanning (SEM) and transmission electron microscopy (TEM). In SEM preparations the boundary of the AP was sharply delineated by the absence of kinocilia. Microvilli were numerous and seemed to be concentrated at the junction between ependymal cells, imparting a polygonal surface pattern superimposed on cell boundaries. Some cell processes were present on the AP surface, but no supra-ependymal cell bodies could be seen over the AP proper. In TEM preparations the AP was characterized by blood vessels with distinct perivascular spaces. These spaces contained fibroblasts and collagen, and were limited by basal laminae. Capillary endothelial cells were typically fenestrated and contained numerous pinocytotic vesicles. Bulbous ending of attenuated cellular processes terminated on the external basal laminae of AP vasculture. Some of these endings could be traced to the cells covering the ventricular surface of the AP. These cells demonstrated several features co-mon to ependymal cells which have been identified as tanycytes. The presence of small neurons frequently seen in groups of three or four confirm previous light microscopic studies. Synapses predominantly of the axodendritic variety were observed, and both dense cored and clear cored vesicles were present on the same ending. Myelinated and unmyelinated axons were a consistent finding in the AP with the former being more abundant in the lateral margins of the AP and in the region of the area subpostrema. The chemoreceptive function of the AP has been widely accepted; however, studies indicate that it is not possible to distinguish species possessing an emetic reflex on the basis of ultrastructural morphology. The possibility that the AP serves functions in addition to emetic chemoreception is considered.

Animals↗
PubMed1975

The ultrastructural morphology of the squirrel monkey area postrema.

Examination of the squirrel monkey (Saimiri sciureus) area postrema (AP) revealed this circumventricular organ to be primarily composed of two types of glial cells and a single type of neuronal element. No pattern of neuronal arrangement could be discerned, however, this cell type was frequently observed in close relation to the perivascular spaces. The neuronal elements, although slightly larger than the glial cells, were characteristically less electron dense. The neurons routinely displayed an infolded nuclear membrane, a single nucleolus and the normal complement of subcellular organelles. Synaptic terminals were numerous, and both axo-somatic and axo-dendritic varieties were observed with the latter being more numerous. Both clear-cored and dense-cored vesicles could be observed in the same ending. Unmyelinated neuronal processes were the predominant type within the interior of the AP, although myelinated processes were also regularly present. Non-neuronal elements with the AP resembled CNS astrocytes and were as numerous as the neuronal elements. This cell type appeared to envelope completely the vasculature and separated the parenchyma from the perivascular spaces. The ventricular surface of the AP was covered by modified ependyma which lacked kinocilia but frequently demonstrated microvillar projections. Opposed ependymal cell membranes showed interdigitations, and zonula adherens-type cell junctions connected the ependymal cells near the ventricular lumen. Two types of bulbous projections were observed in the ventricular lumen close to the ependymal surface. The most characteristic feature of the AP, however, was its vascularity. Perivascular spaces surrounding fenestrated capillaries contained fibroblasts and collagen. The vascular endothelium routinely demonstrated pinocytotic activity, and the basal lamina was prominent.

Animals↗
PubMed1975

The effects of cosmic particle radiation on pocket mice aboard Apollo XVII: appendix I. Condition of flight animals on recovery; food intake; observations on hypothalamus, pituitary, and adrenal glands.

The rationale for studying certain hypothalamic nuclei and the pituitary and adrenal glands of the pocket mice that flew on Apollo XVII was the need to evaluate the effects of the potentially severe stress on these animals in the foreign environment of flight canister, weightlessness, increased G forces, and other unnatural conditions. Decrease in body weight and variability of food intake were significant among the four flight animals that were recovered alive. The mean nuclear diameter of neurons in the arcuate and ventromedial hypothalamic nuclei did not differ significantly from the values obtained in the control animals. On the other hand, the mean nuclear diameter of neurons in the supraoptic nucleus of the flight mice was significantly greater than in the control groups. Comparisons of the adeno- and neuropypophysis revealed no significant differences among the three groups. Insofar as they were studied, the adrenals were similar in all groups.

Adaptation, Physiological↗