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Biomedical subjects

M Bird

Publications and source records attributed to M Bird.

At least 19 recordsLinked to original sources
PubMed1992

The aging mover: a preliminary report on constraints to action.

Locomotion by older adults is typically characterized by performance declines. Older individuals walk more slowly, take shorter steps, and spend a longer time in support than young individuals. Investigators assumed implicitly that declines are related to an inevitable aging process. The purpose of this investigation was to examine constraints that might result in the declines described, outside or in addition to, the general process of aging. We examined two types of terrain over which locomotion might occur, level ground and stairs, and two movement speeds, preferred and fast. Healthy, active females between twenty to eighty years were videotaped. Individuals over sixty years walked at significantly slower speeds, particularly climbing stairs. They used a smaller range of speeds than younger individuals. Despite this slowing, the pattern of coordination between limbs remained essentially the same across the ages tested. The small magnitude of declines observed was attributed to the good health and active lifestyles of these individuals.

Activities of Daily Living↗
PubMed1992

Gallbladder function in acromegalic patients taking long-term octreotide: evidence of rebound hypermotility on cessation of treatment.

Octreotide is increasingly being used in the treatment of acromegaly. It effectively suppresses growth hormone secretion but also has inhibitory effects on gastrointestinal regulatory peptides and induces gallbladder paresis, which may predispose to gallstone formation. In nine acromegalic patients receiving long-term octreotide treatment gallbladder emptying, assessed by 99Tc-EHIDA scintigraphy after a standard fatty meal, was significantly impaired (p less than 0.005) when compared with normal healthy control subjects. Asymptomatic gallstone formation occurred in one patient who had the most severely impaired gallbladder emptying. Between 24 and 96 h after cessation of octreotide, in six of seven patients studied, gallbladder emptying had not only recovered but demonstrated significant rebound hypermotility (p less than 0.005). This finding has important implications for the administration of long-term octreotide therapy and suggests that a drug-free period each week may enable evacuation of gallbladder contents and reduce the risk of gallstone formation.

Acromegaly↗
PubMed1991

The effects of short day exposure on seasonal and circadian reproductive rhythms in male golden hamsters.

Male golden hamsters were exposed to long (LD 14:10) or short (LD 10:14) photoperiods (Groups LP and SP, respectively) and tested 4 times over a 30-week period. At each test time, animals were tested twice, once in their subjective night and once in their subjective day. During each test animals were observed for approach and copulatory behaviors in response to hormonally primed receptive females. To determine gonadal condition, changes in testes size and sperm production over weeks in SP or LP condition were also measured. Results show that SP conditions induce gonadal regression (at 9 weeks) and recrudescence (at 17 weeks); gonadal function was fully restored by 21 weeks in SP. This pattern is mirrored by a decline in copulatory behaviors during regression, followed by a resumption of sexual behaviors during gonadal recrudescence. In contrast, approach measures showed an inverse pattern; males showed the highest level of approach behaviors at week 13, during gonadal quiescence. Short day conditions also induce changes in the circadian patterning of copulatory behaviors: whereas LP animals always showed more mounts, intromissions and ejaculations in the dark than in the light, between 1 to 13 weeks in short day conditions. SP animals show equal levels of copulatory behavior in the dark and in the light. At the time of gonadal recrudescence, SP animals start to show circadian patterns of sexual behaviors comparable to LP animals. These differences were not found for approach behaviors. The relationship between the different behavioral systems and physiological measures, and the effects on these of short day exposure are discussed.

Animals↗
PubMed1991

Encoding specificity, depth of processing, and cued recall in Alzheimer's disease.

Unlike normal aging, Alzheimer's disease (SDAT) subjects typically show no benefit in free recall from semantic depth of processing cues at acquisition, but their recall is enhanced by semantic cues at both acquisition and retrieval. However, this apparent encoding-specificity effect might result from cued recall alone. SDAT and control subjects studied pictures in a design comparing depth of processing, cued recall, and encoding specificity. Cued recall alone was ineffective for SDAT subjects but, consistent with other studies, the encoding specificity condition did enhance recall. Both control and SDAT subjects also showed a levels of processing effect in free recall, modified by recency of presentation. Conclusions were: (a) though impaired in the capacity spontaneously to do so, SDAT subjects can be assisted to exploit semantic aspects of material in memory; (b) for optimal remembering in SDAT, substantial cued support should be provided at both ends of the processing continuum.

Aged↗
PubMed1990

Dissociation of the attentional and motivational effects of pimozide on the threshold for rewarding brain stimulation.

The decreased sensitivity of animals to rewarding brain stimulation caused by pimozide has been interpreted as a selective pharmacologic blockade of central reward pathways rather than a nonspecific disruption of performance. In an attempt to confirm this hypothesis, the effects of pimozide on both reward and detection thresholds for intracranial stimulation delivered to the medial forebrain bundle-lateral hypothalamic area (MFB-LH) were determined in four animals. The drug caused a systematic increase in the reward threshold of each subject but had no such effect on the detection threshold. We conclude that pimozide selectively inhibits the rewarding effects of brain stimulation, and that therefore, the D2 dopamine receptor has a major role in activating central reward pathways subserving pharmacologic and electrical reinforcement. The dual anhedonic/antipsychotic effects of neuroleptic medication are discussed as a possible paradox of central importance to the psychopathology of schizophrenia.

Animals↗
PubMed1988

The threshold lowering effects of MDMA (ecstasy) on brain-stimulation reward.

3,4-Methylenedioxymethamphetamine (MDMA) is a psychoactive phenylisopropylamine which is structurally similar to both amphetamine-related sympathomimetics and the hallucinogen, mescaline. MDMA produces pleasurable effects which include euphoria, and recent reports continue to demonstrate its widespread recreational use. The aim of the present study was to assess the effects of racemic MDMA on the threshold for rewarding intracranial self-stimulation, an animal model used to assess a drug's abuse liability in man. Rewarding electrical stimulation was delivered via electrodes stereotaxically implanted in the medial forebrain bundle-lateral hypothalamic area of the rat brain. Thresholds were determined by means of a rate-independent psychophysical method. MDMA produced a dose-related lowering of the reward threshold in all four animals tested. Given that increased sensitivity for rewarding brain stimulation, measured as a lowering of the reward threshold, is an animal model of drug-induced euphoria these results suggest a similar mode of action for its reinforcing effects as other abused substances.

3,4-Methylenedioxyamphetamine↗
PubMed1988

Methaqualone.

Methaqualone is considered a sedative hypnotic drug with a pattern of pharmacological effects similar to those of barbiturates such as pentobarbital. It does have chemical similarities to the barbiturates but was, in fact, synthesized as part of an Indian program looking for antimalarial drugs (Brown and Goenechea, 1973). Methaqualone was selected for the focus of this study five years ago, because of its popularity as a euphoriant among casual recreational drug users in the Boston area. Methaqualone, instead of a barbiturate hypnotic, was therefore used to test our proposed methodology for the assessment of the abuse liability of sedative drugs. As one reviews the history of the clinical use and illicit abuse of methaqualone, it appears particularly unfortunate that a study of this sort was neither completed nor available to our Food and Drug Administration (FDA) and Drug Enforcement Agency (DEA) in 1965. It was at this time that the drug was approved for prescription use and placed in Schedule V, a schedule which essentially places no restrictions on the clinical use of a prescription drug (Falco, 1976). This paper will both review the development of methaqualone and present an experimental methodology for assessing its abuse liability under seminaturalistic conditions.

Adult↗
PubMed1988

Comparative study of the abuse liability of alprazolam, lorazepam, diazepam, methaqualone, and placebo.

Subjective effects of two benzodiazepines--alprazolam and lorazepam--were compared with two drugs of known abuse potential--diazepam and methaqualone--and placebo. This double-blind, crossover trial tested 30 casual recreational sedative users in a seminaturalistic setting. Methaqualone was more euphoriant and less sedative than the benzodiazepines. Diazepam and lorazepam were more euphoriant than placebo; alprazolam's euphoriant effect did not differ from these treatments. On other measures of abuse liability the benzodiazepines rated similarly, diazepam rating highest.

Adolescent↗
PubMed1986

Weight changes in antidepressants: a comparison of amitriptyline and trazodone.

Weight data taken from a 6-week randomized double-blind study comparing amitriptyline, trazodone and placebo were analyzed to determine differential weight changes between the two drugs. In 272 depressed outpatients doses were increased over a period of 4 days to reach a maximum level of 200 mg amitriptyline or 400 mg trazodone. After grouping the subjects according to initial weights (ideal, overweight, 20% above, and underweight, 20% below) mean changes were determined for each treatment. The results indicate that amitriptyline, which differed from placebo and trazodone, produced significantly higher weight gains in the ideal and overweight groups. Trazodone on the other hand produced a slight weight loss in the overweight group. Due to a low number of patients in the underweight group, the results were not significantly statistically. The antidepressant effects of both trazodone and amitriptyline were the same and no correlations between Hamilton scores and weight change were found.

Adolescent↗
PubMed1979

Inhibition of the mixed lymphocyte reaction by fractionated niridazole urine dialysate.

Urine dialysate from rats treated orally with 25 mg/Kg 3H-labeled niridazole was fractionated by DEAE-Sepharose column chromatography and was found to contain three radioactive metabolites and no parent compound. When human niridazole urine dialysate (NUD) was fractionated under identical conditions, fractions corresponding to the three rat NUD metabolites were found to inhibit the human one-way MLR. No inhibition was obtained with fractionated control urine dialysate. It was concluded that nonimmunosuppressive niridazole is metabolized by rats and man to produce three active compounds with the ability to suppress the in vitro response to alloantigens.

Animals↗
PubMed1979

Subclavian cannula for temporary hemodialysis.

A new silastic and teflon cannula has been developed for temporary hemodialysis access. It is introduced through the subclavian vein by the Seldinger technique. The cannula which is quick and easy to insert, can be used repeatedly for weeks or months without limiting the patient's mobility and without the need for repeated vessel punctures. Complications are few and largely preventable. Since introduction of the subclavian hemodialysis cannula at the Toronto Western Hospital in September 1977 no patient with end-stage renal failure has required insertion of a silastic-teflon shunt or temporary peritoneal dialysis, nor has hemodialysis had to be postponed because of lack of an arteriovenous fistula.

Bacterial Infections↗