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Biomedical subjects

J B Martin

Publications and source records attributed to J B Martin.

At least 109 records · Page 6Linked to original sources
PubMed1989

Three example applications of optimization techniques to Department of Energy contractor radiation protection programs.

Six numerical examples of optimization of radiation protection are provided in the appendices of International Commission on Radiological Protection (ICRP) Publication No. 37 (1983). In each case, the calculations were based on well-defined parameters and assumptions. In this paper, we examined three different numerical examples that were based on empirical data and less-certain assumptions. In the first example, the optimum sampling frequency for a typical 3H bioassay program was found to be once every 2 mo. However, this result depended on assumed values for several variables that were difficult to evaluate. The second example showed that the optimum frequency for recalibrating a group of "cutie pie" (CP) ionization chamber survey instruments was once every 85 d. This result depended largely on the assumption that an improperly operating CP instrument could lead to a serious overexposure. In the third example, one continuous air monitor (CAM) was determined to be the optimum number in a workplace at a Department of Energy (DOE) Pu facility. The optimum location of the CAM was determined from past glove-box release studies. These examples demonstrated that cost-benefit analysis of individual elements of radiation protection programs can be useful even if limited data are available.

Air Pollution, Radioactive↗
PubMed1989

The relationship of electromyographic and vasomotor activity to MMPI subgroups in chronic headache patients: the use of the original and contemporary MMPI norms.

The relationship of electromyographic (EMG) and temporal artery vasomotor activity to MMPI subgroups was examined in 60 chronic headache sufferers. Analysis of the right frontalis data revealed a significant interaction between MMPI subgroup and position (reclining, sitting, standing) with a trend toward the same interaction with the left frontalis. However, this effect was only found when the contemporary MMPI norms were utilized in the formation of the subgroups. No effects were found for the bilateral trapezius EMG or bilateral temporal artery sites. Analysis of the self report data revealed a significant main effect for the Total Pain Score of the Pain Mannequin but not for a current headache intensity rating. Again, the former effect was seen most clearly when the contemporary MMPI norms were used. In general, these data support a Psychological Distress Hypothesis in that patients with significant elevations (greater than 70) demonstrated greater frontalis EMG activity and higher Pain Mannequin scores. Additionally, the data demonstrate the importance of utilizing the contemporary MMPI norms in the formation of subgroups.

Adult↗
PubMed1989

Iso stimulation of GH and cAMP: comparison of beta-adrenergic- to GRF-stimulated GH release and cAMP accumulation in monolayer cultures of anterior pituitary cells in vitro.

Growth hormone (GH) release and cAMP content were measured in monolayer cultures of anterior pituitary cells after beta-adrenergic and GH-releasing factor (GRF) receptor activation. Isoproterenol (Iso, ED50-20 nM) was less potent than GRF (ED50-20 pM) in stimulating GH release. Iso caused a rapid stimulation of GH release that was maximal after 15 min and declined thereafter, while GRF caused a more gradual increase in GH secretion that was maximal after 30 min and remained elevated after 3 h. Both Iso- and GRF-stimulated GH release were preceded by an increase in cAMP content in the pituitary cells. Further, the addition of 3-isobutyl-1-methylxanthine (IBMX) to the medium enhanced the GH-stimulatory and cAMP-accumulating effects of both secretagogues. Experiments performed with native catecholamines and synthetic catecholamine agonists and antagonists indicated that the GH-stimulatory effect of Iso was mediated by a mixed population of beta 1-adrenergic and beta 2-adrenergic receptors. Additionally, experiments performed with cultured GH3 tumor cells, found that incubation with GRF, Iso, vasoactive intestinal polypeptide, forskolin, or cholera toxin caused an increase in cAMP content in the cells. However, compared to the responses observed in primary pituitary cultures the GH secretory response to these agents was comparatively small. Together, these studies suggest that a mixed population of beta 1-adrenergic and beta 2-adrenergic receptors may act, at least in part, on somatotrophs in the anterior pituitary to stimulate GH release. Although both GRF and beta 2-adrenergic receptor agents affect GH release through a common second messenger system, their differing pharmacokinetic properties suggest distinct intracellular mechanisms.

1-Methyl-3-isobutylxanthine↗
PubMed1989

Sexual and developmental differences in peptides regulating growth hormone secretion in the rat.

Sex differences in the hypothalamic control of growth hormone (GH) secretion were investigated by measuring rat GH-releasing factor (rGRF) and somatostatin in male and female rats. Rat GRF-like immunoreactivity (rGRF-IR) was higher in the median eminence and hypothalamic tissue outside of the median eminence of adult (90-day-old) male compared to female rats. A similar pattern of rGRF-IR content was found in the median eminence of 35-day-old rats. This sex difference developed between days 25 and 35 of age, during which time serum concentrations of insulin-like growth factor (IGF-1) and body weight increased in both sexes. To a lesser extent, the content of somatostatin-like immunoreactivity (SLI) was higher in the median eminence of adult female rats compared to male rats. Whole hypothalamic rGRF-IR and SLI contents were influenced only moderately by adult gonadectomy or gonadal steroid treatments. For example, estrogen increased rGRF-IR content in castrated rats, but orchidectomy alone or orchidectomy followed by testosterone did not influence rGRF-IR content. Additionally, whole hypothalamic SLI content was unaffected by orchidectomy or orchidectomy followed by testosterone or estrogen. One month after ovariectomy, rGRF-IR and SLI in whole hypothalamic fragments were similar to their respective contents in gonad-intact males. However, ovariectomy followed by estrogen or testosterone did not restore rGRF-IR content and partially restored SLI content to levels seen in gonad-intact females.

Aging↗
PubMed1988

Amino acid and neuropeptide neurotransmitters in Huntington's disease cerebellum.

Several neuropathologic studies have suggested that there may be pathologic involvement of the cerebellum in Huntington's disease (HD). To investigate this further, we measured concentrations of neurotransmitter amino acids and the neuropeptides, somatostatin, neuropeptide Y and substance P, in HD cerebellar cortex and dentate nucleus. Twenty-seven pathologically confirmed cases of HD were compared with 20 controls. There were no significant changes in concentrations were significantly increased by 21% in HD cerebellar cortex. In the dentate nucleus, there were small significant increases of neuropeptide Y-like immunoreactivity and substance P-like immunoreactivity. The meaning of the neurotransmitter changes found is unclear: however, the lack of change in GABA and glutamate concentrations argues against a substantial loss of intrinsic cerebellar neurons.

Aged↗
PubMed1988

Characterization of galanin-like immunoreactivity in the rat brain: effects of neonatal glutamate treatment.

Concentrations of the neuropeptide, galanin, were measured using a newly characterized radioimmunoassay in brain regions of adult male rats treated neonatally with monosodium glutamate. Galanin-like immunoreactivity (galanin-IR) was significantly reduced 57% in the median eminence, 15% in the medial basal hypothalamus, and 27% in the septal region when compared to untreated littermates. Concentrations of galanin-IR were reduced 22% in the preoptic region and unchanged in the parietal cortex. These studies suggest that glutamate-sensitive, galanin-containing neurons in the arcuate nucleus project to regions of the basal forebrain of the rat in addition to the median eminence. The galanin projection from the arcuate nucleus to the median eminence suggests that this peptide plays a role in the regulation of anterior pituitary hormone secretion.

Age Factors↗
PubMed1988

Predictive testing for Huntington's disease with use of a linked DNA marker.

The probability of carrying the gene for Huntington's disease can in many cases be estimated in the children of affected persons by identifying a specific DNA marker that is genetically linked to the gene. We studied 47 persons at 50 percent risk of inheriting Huntington's disease who requested a presymptomatic or prenatal genetic-linkage test between September 1986 and January 1988. The participants were given pre-test counseling and psychological and neurologic evaluations. Nineteen persons later voluntarily withdrew from the protocol, including one who would have been excluded anyway, and one person was from a family that was too small to allow testing. Three D4S10 restriction-fragment-length polymorphisms produced by the HindIII, EcoRI, and Bg/I enzymes were used for all tests, and the probability that a subject was a Huntington's disease carrier was calculated. The accuracy of the test was compromised by a 4 percent recombination frequency between D4S10 and the Huntington's disease gene. Fifteen presymptomatic tests and one prenatal test were completed. Four yielded positive results, seven yielded negative results, and five were uninformative; seven persons are awaiting test results. All participants with positive tests experienced intermittent depression, but none required hospitalization, and no suicide threats were reported. Five participants received a diagnosis of Huntington's disease on the basis of the neurologic assessment. We conclude that some persons in the early stages of Huntington's disease may seek presymptomatic testing rather than neurologic evaluations.

Adult↗
PubMed1988

Somatostatin and neuropeptide Y concentrations in pathologically graded cases of Huntington's disease.

Somatostatin and neuropeptide Y concentrations have previously been reported to be increased in the basal ganglia in Huntington's disease (HD). In the present study we have extended these findings by examining both somatostatin-like immunoreactivity (SLI) and neuropeptide Y-like immunoreactivity (NPYLI) in cases of HD, which were graded according to the severity of pathological degeneration in the striatum. In addition, we surveyed a large number of subcortical nuclei and cortical regions for alterations. Both SLI and NPYLI were significantly increased about threefold in the caudate, putamen, and the nucleus accumbens. Increases in mild and severe grades were similar, which is consistent with a relative but not absolute sparing of striatal aspiny neurons in which somatostatin and neuropeptide Y are colocalized. Significant increases of NPYLI were also found in the external pallidum, subthalamic nucleus, substantia nigra compacta, claustrum, anterior and dorsomedial thalamus, bed nucleus of the stria terminalis, and locus ceruleus. SLI was significantly increased in the external pallidum, red nucleus, and locus ceruleus. Measurements of both neuropeptides were made in 24 regions of the cerebral cortex. Significant increases in both NPYLI and SLI were found in the frontal cortex (Brodmann areas 6, 8, 9, 10, 11, and 45) and temporal cortex (Brodmann area 21), whereas NPYLI was also increased in Brodmann areas 12, 20-22, 25, and 42. Alterations in the cerebral cortex were as pronounced in cases with mild striatal pathological changes as in those with severe striatal pathological changes. These alterations may occur early in HD and could reflect a selective sparing of somatostatin-neuropeptide Y cortical neurons combined with cortical atrophy.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

The physician as a locus of authority, responsibility, and operational control of medical systems.

Physicians are commonly being excluded from meaningful participation in the planning, implementation, and operation of automated medical systems in hospitals. The authors advocate a rapid shift toward greater physician involvement in such systems, arguing that such a shift is desirable, feasible, and also inevitable. After reviewing the organization of information systems in hospitals, the authors describe the manner in which physician control of medical systems adds to the worth of such systems by enhancing the quality and efficiency of health care delivery. The proposed information system management role of physicians is characterized in terms of authority, responsibility, and operational control. Finally, advice is offered from an organizational perspective for establishing a physician as the hospital Medical Information Director.

Attitude to Computers↗
PubMed1988

A detailed examination of substance P in pathologically graded cases of Huntington's disease.

Substance P concentrations have been found to be reduced in the basal ganglia in Huntington's disease (HD). In order to further examine this finding in the present study we measured substance P-like immunoreactivity (SPLI) in cases of HD which had been graded as to the severity of pathological changes in the striatum. Marked significant reductions of SPLI were found in all striatal nuclei which were significantly correlated with the percentage of neuronal loss in the varying pathologic grades. Similar changes were found in the projection sites of striatal substance P neurons, the globus pallidus interna and the substantia nigra. These changes are consistent with a loss of striatal substance P containing projection neurons in HD. Significant reductions in SPLI were also found in the external pallidum, bed nucleus of the stria terminalis and the subthalamic nucleus. Small significant increases in SPLI (20-30%) were found in 3 frontal cortical regions (Brodmann areas 6, 8 and 9). The finding of neurochemical changes in the subthalamic nucleus is of particular interest since lesions in this nucleus are known to result in chorea and therefore might contribute to the chorea which is a cardinal symptom of HD.

Aged↗
PubMed1988

Galanin stimulates rat pituitary growth hormone secretion in vitro.

The effect of galanin on growth hormone (GH) secretion was investigated in monolayer cultures of rat anterior pituitary cells. Galanin caused a gradual increase in GH concentrations into the culture medium that was maximal at 90 minutes and sustained after 180 minutes. The ED50 for galanin-stimulated GH secretion was approximately 200 nM compared to an ED50 for rat GH-releasing factor (rGRF)-stimulated GH secretion of 10pM. Galanin and rGRF were additive in increasing GH release into the incubation medium. These data indicate that porcine-derived galanin has a direct effect on pituitary GH secretion in vitro.

Animals↗
PubMed1988

Mortality patterns among hypertensives by reported level of caffeine consumption.

The effect of caffeine consumption on mortality was evaluated in a historical cohort study of 10,064 diagnosed hypertensive individuals participating in the Hypertension Detection and Follow-up Program from 1973 to 1979. Total caffeine intake level from beverages (coffee and tea) and certain medications, was estimated at the 1-year visit. No evidence was found supporting an association between increased level of caffeine consumption and increased all-cause mortality or cardiovascular disease mortality during the following 4 years. Cigarette smoking was significantly associated with mortality; the association being more pronounced among non- and low-caffeine consumers for all-cause mortality and among non-caffeine consumers for all cardiovascular mortality except cerebrovascular mortality.

Adult↗
PubMed1988

Effect of dexamethasone on cortisol and prolactin responses to meals in bulimic and normal women.

In normal individuals, serum cortisol and prolactin concentrations have been shown to rise following a mid-day meal. To determine whether abnormalities of the hypothalamo-pituitary-adrenal axis in bulimics lead to a disrupted hormonal response to eating, cortisol and prolactin responses to meals (600 kcal, 30% protein, 30% fat, 40% carbohydrate) were studied on two consecutive days in six normal weight bulimics and six normal volunteers. Dexamethasone (1 mg orally) was administered at 2330 h after baseline sampling. During baseline sampling, cortisol concentrations were significantly higher in the bulimics (18.2 +/- 0.9 micrograms/dl, mean +/- SEM) than in the normals (12.1 +/- 0.4 micrograms/dl) (p less than 0.001). Post-dexamethasone cortisol concentrations also were higher in the bulimics (5.7 +/- 0.3 micrograms/dl) than in the normals (1.2 +/- 0.2 micrograms/dl) (p less than 0.001). The three bulimics with a major depressive disorder had higher peak post-dexamethasone cortisol concentrations than the nondepressed bulimics. Dexamethasone significantly enhanced the prolactin response to meals among both bulimics (at 90 min post onset of eating) and normals (at 60, 75 and 90 min post onset of eating). This enhancement of the prolactin response to meals by dexamethasone is opposite to the inhibitory effect of dexamethasone on stress-induced prolactin release and suggesting that stress-induced and meal-induced prolactin release involve different neuroendocrine mechanisms.

Adult↗
PubMed1988

Galanin is an estrogen-inducible, secretory product of the rat anterior pituitary.

Galanin is a peptide widely distributed throughout vertebrate central and peripheral nervous systems. Although its precise physiologic role is unknown, it can stimulate the pituitary secretion of prolactin and growth hormone. We examined the control of rat galanin (rGal) gene expression in the anterior pituitary using RNA blot and in situ hybridization analyses and using specific RIA. Pituitaries of normal male and ovariectomized female rats contained little detectable rGal mRNA. Treatment of these animals with 17 beta-estradiol increased pituitary rGal mRNA up to 4000-fold. These increases depended on time and dose of estrogen administration and correlated with up to 50-fold increases in pituitary galanin-like immunoreactivity. Galanin-like immunoreactivity was detectable in the plasma of estrogen-treated animals. Pituitary levels of rGal mRNA in female rats varied greater than 30-fold during the estrous cycle, with a peak on estrus and a nadir on diestrus. Estrogen-induced rGal gene expression was also observed in transplantable MtTW15 prolactin- and growth hormone-containing tumors but not in neuronal tissues expressing this gene. These data demonstrate that rGal is a secreted product of rat anterior pituitary cells, where its gene expression is strongly affected by physiologic levels of circulating estrogen.

Animals↗
PubMed1988

The use of silicone/polyurethane graft polymers as a means of eliminating surface cracking of polyurethane prostheses.

The long-term biodegradation of various polyurethanes with and without surface modifications was evaluated by implanting small porous filamentous patches of these materials subcutaneously in the backs of dogs for one month. Data were compared to those obtained with spun polyurethane vascular grafts of similar materials implanted in the aorto-iliac position in dogs. The extremely high surface area of approximately 7 m2/cm3 of these porous filamentous patches provided numerous sites for surface cracking and the very fine filaments (10 microns in diameter) provided an easily identifiable structure to study the cracking phenomenon. Results from numerous one month implants clearly demonstrated that the subcutaneous implant model effectively reproduced the biodegradation behavior observed in vascular graft implants. The degradation was most pronounced in the softer Shore 80A polyurethanes and less pronounced in the harder 55D and 75D polyurethanes. The degradation could not simply be stopped by stress annealing the polyurethane and the degradation did not require the presence of metallic ions. Antioxidants, surface adsorbed albumin, poly(2-hydroxyethyl-methacrylate) grafting, silicone copolymerization, tetrafluoroethylene plasma discharge and the addition of urea linkages to the polymer were also shown to be ineffective in stopping the biodegradation process. In contrast, covalent bonding or grafting of silicone polymer to the surface of the urethane successfully inhibited the biodegradation process.

Animals↗