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Biomedical subjects

D Houser

Publications and source records attributed to D Houser.

17 recordsLinked to original sources
PubMed2006

Effects of brief yoga exercises and motivational preparatory interventions in distance runners: results of a controlled trial.

OBJECTIVE: To examine the efficacy of two preparatory interventions on one mile run performance in 90 high school long distance runners. METHOD: After participants had completed a one mile baseline run, they were randomly assigned to participate in either one of two interventions (brief yoga exercises, motivational shouting exercises) or a no intervention control condition. Experimental conditions were implemented one week after the baseline run about 20 minutes before a second one mile trial. RESULTS: Participants assigned to the motivational intervention improved their running performance significantly more than those assigned to the other two conditions. Although the magnitude of the effect was small, participants assigned to yoga exercises showed significant improvements in running performance relative to control condition participants. Consumer satisfaction ratings indicated that participants who were assigned to the motivational and yoga exercise groups liked their interventions more than those assigned to the control group. CONCLUSION: Motivational and yoga interventions designed to improve long distance running performance were equally acceptable to the participants, but the former had a greater effect.

Adolescent↗
PubMed2001

A functional imaging study of cooperation in two-person reciprocal exchange.

Cooperation between individuals requires the ability to infer each other's mental states to form shared expectations over mutual gains and make cooperative choices that realize these gains. From evidence that the ability for mental state attribution involves the use of prefrontal cortex, we hypothesize that this area is involved in integrating theory-of-mind processing with cooperative actions. We report data from a functional MRI experiment designed to test this hypothesis. Subjects in a scanner played standard two-person "trust and reciprocity" games with both human and computer counterparts for cash rewards. Behavioral data shows that seven subjects consistently attempted cooperation with their human counterpart. Within this group prefrontal regions are more active when subjects are playing a human than when they are playing a computer following a fixed (and known) probabilistic strategy. Within the group of five noncooperators, there are no significant differences in prefrontal activation between computer and human conditions.

Adaptation, Physiological↗
PubMed1995

Enhancement of cardiac function by cyclocreatine in models of cardiopulmonary bypass.

This study tests the hypothesis that the administration of cyclocreatine prior to global ischemia enhances recovery of cardiac function during reperfusion. Two models were used. First, in a Langendorff-working heart model of normothermic cardioplegic arrest, rats (n = 6 per group) were injected intravenously with saline or cyclocreatine (600, 300, or 150 mg/kg). After 30 min or 2 h, hearts were excised and perfused in the Langendorff mode for 5 min and then in the working heart mode for 20 min. Normothermic arrest was induced by infusing warm St. Thomas solution once; then hearts were kept at 37 degrees C for 40 min. Following arrest, hearts were reperfused in the Langendorff mode for 15 min and then in the working mode for 30 min. Cyclocreatine consistently produced significantly better recovery of aortic flow and cardiac output compared to that of saline hearts. Second, in an intact canine model of cold cardioplegic arrest, adult mongrel dogs (n = 3 to 6 per group) underwent aortic cross-clamping for 1 h, followed by reperfusion on bypass for 45 min and off bypass for 4 h. Dogs were injected intravenously with saline or cyclocreatine (500 mg/kg) for 1 h before experiment. Post-bypass segmental contractility and cardiac output were significantly better in cyclocreatine hearts compared to that of controls. In a limited study, after a 3 h aortic cross-clamp time, cyclocreatine hearts achieved 91% baseline function while control hearts failed after 2 h. Results of this study suggest that cyclocreatine, without inotropic or chronotropic effect, protects the heart from global ischemic injury.

Animals↗
PubMed1994

Studies of copper transport in cultured bovine chondrocytes.

Copper serves as the cofactor for a number of important enzymes in cartilage, as well as in other tissues, including lysyl oxidase, superoxide dismutase, and cytochrome oxidase. Ceruloplasmin is responsible for the transport of approx. 95% of the copper in serum, but the mechanisms for intracellular copper transport are unknown. We have demonstrated recently that a high-molecular-weight cartilage glycoprotein, referred to as CMGP, has regions of sequence homology with ceruloplasmin. CMGP also binds copper and has at least some oxidase activity similar to that of ceruloplasmin. Other tissues synthesize intracellular ceruloplasmin-like proteins. The present report represents part of an effort to examine the hypothesis that CMGP is a copper transport protein in chondrocytes and to characterize the enzymatic activities of CMGP. These studies demonstrate that CMGP is the principal chondrocyte protein labeled by 67Cu in vitro and that the label is localized to the mitochondria, cytosol, and membrane fractions of sucrose gradients, suggesting copper transport through the cell. In parallel experiments, [3H]leucine was incorporated into proteins corresponding to the subunits and fragments of CMGP, as described previously, and in a similar distribution among the subcellular fractions as labeled copper. Additionally, CMGP has oxidase and ferroxidase activities similar to those of ceruloplasmin.

Animals↗
PubMed1994

Evaluation of 3-[18F]fluoro-alpha-fluoromethyl-p-tyrosine as a tracer for striatal tyrosine hydroxylase activity.

3-[18F]Fluoro-alpha-fluoromethyl-p-tyrosine (3-F-FMPT) was evaluated as a tracer for CNS tyrosine hydroxylase (TH) activity in rodents and in a rhesus monkey. Results of in vitro experiments using rat striatal homogenates showed that the introduction of fluorine into the 3-phenyl position did not significantly alter the ability of FMPT to act as a TH-activated L-aromatic amino acid decarboxylase (L-AAAD) inhibitor. These studies further showed that 3-F-FMPT-induced L-AAAD inhibition was dose-dependent. Furthermore, striatal homogenates prepared from rats pretreated with the potent TH inhibitor alpha-methyl-p-tyrosine was found to have diminished 3-F-FMPT-induced L-AAAD inhibition. However, despite these promising in vitro results, the biodistribution of this compound in mice showed low brain uptake and fast clearance through the kidneys. A PET study using a Rhesus monkey injected with 3-[18F]F-FMPT confirmed the results obtained in mice, i.e. negligible brain uptake but high localization in the bladder. We conclude that 3-[18F]F-FMPT would not be useful as a tracer for cerebral TH activity.

Animals↗
PubMed1992

Visualization of dopamine nerve terminals by positron tomography using [18F]fluoro-beta-fluoromethylene-m-tyrosine.

[18F]-6-Fluoro-beta-fluoromethylene-m-tyrosine ([18F]FFMMT) was evaluated as a potential imaging agent for dopamine nerve terminals using positron emission tomography (PET). Biodistribution and time course of this tracer in mice after i.p. injection was consistent with the distribution of dopamine. PET imaging studies involving rhesus macaques showed specific uptake in the dopamine-rich caudate-putamen region. This specific localization was blocked by inhibiting the enzyme L-aromatic amino acid decarboxylase and the transport of the tracer into brain was shown to be stereospecific. These results show the promise of L-[18F]FFMMT as a PET tracer in monitoring degeneration of the CNS dopamine system.

Animals↗
PubMed1990

A rhesus monkey model for sexual transmission of a papillomavirus isolated from a squamous cell carcinoma.

Recently we molecularly cloned and characterized a papillomavirus from a lymph node metastasis of a primary penile carcinoma found in a rhesus monkey; this virus species, rhesus papillomavirus type 1 (RhPV-1), is similar to oncogenic human papillomaviruses (HPVs), such as HPV-16 or HPV-18, in that the RhPV-1 DNA was found to be integrated in the tumor cell DNA. To compare the sexual transmission and oncogenic nature of RhPV-1 with these HPVs, we undertook an extensive retrospective study of a group of rhesus monkeys whose sexual mating and offspring histories were known. These animals had mated directly with the index male mentioned above or were secondarily exposed to this virus through intermediate sexual partners. This study combines cytological, histopathological, and several complementary hybridization and DNA amplification techniques on multiple tissue samples to demonstrate the sexually transmitted nature of RhPV-1. The oncogenic potential of RhPV-1 is suggested in several of the infected animals by the presence of various degrees of neoplasia including squamous cell cancer of the cervix.

Animals↗
PubMed1989

Alternatives to single caging of rhesus monkeys (Macaca mulatta) used in research.

Alternatives to single caging of laboratory rhesus monkeys were explored. 1. Surplus infants (12-18 months old) from breeding troops were paired with 48 adult females (6-28 years old) and 12 adult males (8-28 years old) that had lived alone for several years. Adults and infants were not related. The partners were compatible in 87% (42/48) and 83% (10/12) of cases, respectively, throughout follow-up periods of 16-25 months. The young companions reached 28-44 months of age during that time. 2. Forty-six unrelated adult female rhesus monkeys (7-23 years old) and 10 unrelated adult male rhesus monkeys (8-16 years old) that had lived alone for several years were familiarized in isosexual dyads and then paired in different cages. Paired companions were compatible in 83% (19/23) and 80% (4/5) of cases, respectively, throughout follow-up periods of 9-24 months. Of all animals tested, 2% (3/176) received a bleeding but not life-threatening wound by an incompatible partner. Pairing previously individually caged rhesus monkeys did not interfere with the following research protocols: tethering of one partner for remote collection; head-cap implantation on one or both partners; chair-restraining of one partner while the other is kept close by for psychological support; in-cage venipuncture of both partners (attempted with females only); temporary (1-7 d) partner separation for timed breeding or for experimental surgery. Pairing singly caged adult rhesus monkeys with infant or with other adult companions is recommended as an effective way to promote the animals' wellbeing by enabling them to express their inherent need for social contact.

Aggression↗
PubMed1987

Prompted progression order in a troop of captive rhesus monkeys.

It is a routine practice to subject captive groups of primates to single-file movement; yet no records on the sequences of such progressions have been published. The present study analyzes the progression sequence during prompted single-file movement for the purpose of routine weighing in a captive troop of rhesus monkeys (Macaca mulatta). The animals had to overcome fear before leaving their home pen; nonetheless, they left in a well-defined, stable sequence. An individual's position in this progression order as well as the consistency with which it retained its place were dependent on its age but not on its dominance status. It was suggested that the monkeys gradually learned with age to master their fear with the prospect of quickly returning to their home pen.

Animals↗
PubMed1986

Hair pulling and eating in captive rhesus monkey troops.

Hair pulling and eating has not yet received attention in the nonhuman primate literature. Hair pulling and eating was recorded 388 times in two heterogeneous troops of healthy rhesus monkeys that were kept according to modern management practices. The behavior in question consists of the following sequence: pulling with the fingers (1/3 of cases) or with the teeth (2/3 of cases) tufts of hair from one's own or from a partner's coat; chewing the hair and finally swallowing it; the undigested material is excreted in the feces. Hair pulling was almost exclusively (378/388) partner-directed. It was observed 364 times between animals whose dominance relationships were known; it was performed in 96% (349/364) of observations by a dominant but only in 4% (15/364) of observations by a subordinate monkey. The recipient of hair pulling showed typical fear and/or avoidance reactions. In both troops young animals (2-8 years of age) engaged in hair pulling and eating significantly more often than old animals (10-26 years of age). There was no evidence that nutritional, toxicological or climatic factors were responsible for the manifestation of this behavior. It was concluded that, similar to trichotillomania in man, wool pulling and eating in sheep and muskox, and feather picking in poultry, hair pulling and eating is an aggressive behavioral disorder in rhesus monkeys reflecting adjustment problems to a stressful environment.

Animals↗
PubMed1980

The eye in accelerated hypertension. I. Elschnig's spots in nonhuman primates.

The acute form of Elschnig's spots was produced in a rhesus monkey with experimentally induced accelerated hypertension. Clinically, Elschnig's spots appeared within 24 hours of hypertension as discrete, whitish, subretinal lesions located in the temporal posterior poles of both fundi. The lesions leaked fluorescein. Morphologically, they consisted of complete obstruction of terminal choroidal arterioles and choriocapillaris by fibrin thrombi, necrosis of the retinal pigment epithelium, and fibrinous exudation into Bruch's membrane and into the subpigment epithelial and subretinal spaces. Most of the neurosensory retina was spared from morphologic damage. The differential susceptibility between choroidal and retinal vessels is explained by differences in anatomy and in autonomic nervous control.

Animals↗