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Biomedical subjects

J B Martin

Publications and source records attributed to J B Martin.

At least 19 recordsLinked to original sources
PubMed1992

Cytotoxicity of dichloromethane diphosphonate and of 1-hydroxyethane-1,1-diphosphonate in the amoebae of the slime mould Dictyostelium discoideum. A 31P NMR study.

Two pyrophosphate analogues, dichloromethane diphosphonate (Cl2MDP), and 1-hydroxyethane-1,1-diphosphonate (EHDP), at concentrations of 0.5-1 mM, efficiently inhibited the growth of amoebae of the slime mould Dictyostelium discoideum. Cell viability decreased markedly upon incubation with the diphosphonates. The mechanism of toxicity was investigated by in vivo 31P NMR spectroscopy and the formation of analogues of ATP [adenosine 5'-(beta, gamma-dichloromethane triphosphate) and adenosine 5'-(beta, gamma-1-hydroxyethane triphosphate)] was demonstrated. These two compounds were identified from their 31P NMR spectra in perchloric acid extracts prepared from amoebae poisoned with Cl2MDP or EHDP and may have been synthesized by reversible pyrophosphate exchange catalysed by cytosolic aminoacyl-tRNA synthetases.

Animals↗
PubMed1992

Multinuclear NMR spectroscopy of the cellular slime mold Polysphondylium pallidum. Monitoring of the encystment and excystment processes.

Polysphondylium pallidum microcysts and amoebae have been investigated by 31P- and natural-abundance proton-decoupled 13C-NMR spectroscopy. Microcysts have been found to contain as prominent metabolites a phosphomonoester, inositol hexakisphosphate (1.4 mM), two phosphodiesters [glycerophosphocholine (5.5 mM) and glycerophosphoethanolamine (2.6 mM)], as well as nucleoside triphosphates (3 mM) and polyphosphates (greater than 10 mM), the polyamines 1,3-diamino-propane (3.5 mM), putrescine (16 mM) and spermidine (3 mM) and the sugar trehalose (31 mM). In vivo 31P-NMR has shown that the level of nucleoside triphosphates in microcysts was maintained metabolically and that the pH of their cytosol, deduced from the chemical shift of cytosolic Pi was 7.2. The absence of trehalose, glycerophosphocholine and glycerophosphoethanolamine in P. pallidum amoebae was the most remarkable difference from microcysts. Microcyst germination (excystment), induced by reduction of the ionic strength of the microcyst bathing medium, was monitored non-invasively by 31P- and 13C-NMR spectroscopy. The major modifications observed during excystment were the progressive disappearance of trehalose used as energy source, of glycerophosphocholine and glycerophosphoethanolamine used as membrane phospholipid precursors, and, finally, the appearance of NMR-visible polyphosphates and of cellobiose. As a mirror situation, P. pallidum amoebae responded to a high-ionic-strength stress by production of trehalose, glycerophosphocholine, and glycerophosphoethanolamine, and induction of an encystment process.

Animals↗
PubMed1992

[Treatment of venous thrombosis with low molecular weight heparin and fluindione].

Thirty-one consecutive patients with deep vein thrombosis were treated with Fraxiparine, a low molecular weight heparin, and fluindione, an oral anticoagulant prescribed at an early stage. Despite the weight/biological effectiveness ratio, the dose of Fraxiparine had to be adjusted in 46 percent of the patients to remain within the therapeutic range selected (0.5 to 1 antiXa/ml units). The early administration of fluindione reduced the duration of heparin therapy to 5.75 days. Using a prescription guide on days 2 and 4 might improve the safety of the fluindione induction.

Adult↗
PubMed1992

Neurologic manifestations of hypothalamic disease.

The hypothalamus, in addition to regulating the anterior and posterior pituitary, controls water balance through thirst, regulates food ingestion and body temperature, influences consciousness, sleep, emotion and other behaviors. Much has been learned of these effects in human disease through the clinical manifestations that occur with hypothalamic lesions. This study reviews the clinical pathologic correlations that have been made in recent years showing that regions of the hypothalamus exert functions in humans that are similar to those identified in experimental animals. Clinical pathologic correlations have not always provided precise analysis of hypothalamic function. The hypothalamus is small and often lesions that come to clinical attention achieve considerable size before their recognition, making local anatomic dissections of the effects of the lesions difficult. Nevertheless, the use of modern non-invasive techniques including CT scans and magnetic resonance imaging (MRI) have provided new information not previously available. This paper reviews several cases of hypothalamic disorder recognized recently. (1) A 33-year-old black man with hypothalamic sarcoidosis. Manifestations of hypothalamic dysfunction included panhypopituitarism, aggressive hyperphagia, polydipsia (partially due to hyperglycemia secondary to diabetes mellitus), drowsiness, depression, and irritability. (2) A 37-year-old woman with a large intrahypothalamic tumor (biopsy showed pituitary adenoma), with drowsiness, poikilothermia, lack of satiety, confusion, and memory loss. She becomes depressed when she is transiently more alert (as after hypertonic contrast-dye infusion). (3) A 60-year-old man with hypothalamic compression by a pituitary tumor, associated with syndrome of inappropriate ADH (SIADH), severe anorexia, memory loss, but preserved thirst. After surgical decompression of the tumor his appetite acutely recovered, but he developed severe hypo(poikilo)thermia. (4) A 45-year-old woman with a suprasellar craniopharyngioma presented with severe drowsiness, hyperphagia, depression, and memory loss post-operatively, which responded to antidepressants (except for the memory loss). She had extremely labile blood pressures and serum Na for about 1 week post-operatively.

Adult↗
PubMed1992

Cancer pain: a multidimensional perspective.

Cancer pain has traditionally been studied from a unidimensional/medical model. However, limitations of the medical model have led researchers to the development of multidimensional models of cancer pain. The current manuscript describes a multidimensional model of cancer pain with six components: physiological, sensory, affective, cognitive, behavioral and sociocultural. Research relevant to each component of the model is reviewed with an emphasis on future research directions.

Humans↗
PubMed1992

Information systems for evaluating the quality of prescribing.

OBJECTIVE: An important purpose of drug usage evaluation (DUE) is to provide feedback to physicians on population-based prescribing patterns and problems. This article has four objectives: (1) to outline prescribing information requirements for a computerized information system in terms of the variables needed for DUE, (2) to describe existing computerized information systems that collect and organize prescribing data, (3) to assess existing systems in terms of their capacity to provide the requirements outlined in our first objective, and (4) to suggest design changes to existing systems that would improve the DUE process. ANALYSIS: There are several existing DUE information systems that have some capacity to evaluate the quality of prescribing in specific populations (e.g., veterans, public and private insured groups, hospital service areas). Shortcomings of most DUE information systems include patient identification problems, defects in database design, and lack of software to identify prescribing problems and perform statistical analysis. CONCLUSIONS: DUE information systems could be used and upgraded to enable physicians to develop more rational prescribing rules from population data that would improve the quality of prescribing.

Drug Prescriptions↗
PubMed1992

Design and validation of a critical care simulation model.

The high costs of building, equipping, and staffing critical care beds, coupled with more restrictive reimbursement policies, are forcing hospital administrators to seek ways for determining accurately the number of critical care beds needed. Existing critical care bedsizing models do not capture the complexity of today's critical care environment, nor have they been formally validated using actual hospital performance data. The study described herein was designed to address these needs. A GPSS/H simulation model was developed and validated, and includes the flow of patients through the study hospital's operating rooms, post-anesthesia recovery unit, three intensive care units, and two intermediate care (stepdown) units.

Bed Occupancy↗
PubMed1992

Identification of factors associated with hospital readmission and development of a predictive model.

Multiple hospital admissions, especially those related to the chronically ill, represent a particular challenge to both the acute and long-term care sectors to identify effective methods of resource management. This study analyzes the multiple admission patterns associated with a cohort of 4,219 adult medical-surgical patients discharged alive from a community teaching hospital in Michigan. The sample was divided into two groups: 3,818 patients who survived and 392 who expired during the one-year follow-up period. For the surviving subsample, the characteristics found to be directly associated with the likelihood of readmission included increased age, advanced stage of disease, greater index-episode length of stay, discharge by an internist rather than a surgeon, Medicare as expected source of payment, decreased physician age, discharge to a community setting, and increased number of prior hospital episodes. For the subsample who died, only one explanatory variable was significantly associated with an increased likelihood of readmission-discharge to a community setting (with or without home care) rather than a nursing home. The article includes illustrates of the importance of decisions regarding posthospital, long-term care services on the likelihood of rehospitalization.

Adult↗
PubMed1990

Influence of thyroid hormone on the concentration of galanin in the rat brain and pituitary.

Galanin (GAL) is a 29-amino acid peptide implicated in neuroendocrine regulation of prolactin, growth hormone and thyrotropin in the rat. GAL-like immunoreactivity and GAL messenger RNA (mRNA) are present in the anterior pituitary (AP) and hypothalamus and the expression of GAL mRNA has been shown to be modulated by peripheral gonadal steroid hormones. In view of possible interactions between members of the steroid/thyroid hormone receptor family and recent data suggesting an effect of GAL on thyrotropin secretion, we investigated the possible influence of thyroid status on GAL concentrations in the hypothalamus and AP of the male rat. Three weeks after the surgical removal of the thyroid gland from male rats, the concentrations of GAL in the median eminence (ME) and AP were reduced 54 and 65%, respectively. Similarly, GAL concentrations were decreased 39% in the ME and 69% in the AP of animals rendered hypothyroid by treatment with propylthiouracil (PTU). The effects of PTU treatment in both regions were reversed by daily T4 injections (50 micrograms/kg). The effects of PTU in the ME were reversed after 2 weeks of T4 treatment, whereas 3 weeks of replacement therapy were required to restore GAL concentrations in the AP. However, T4 treatment of intact control animals did not influence GAL concentrations. This study demonstrates that the presence of thyroid hormones is required for the maintenance of physiological concentrations of GAL in the hypothalamus and AP of the rat. These data also suggest that GAL may be involved in the negative feedback regulation of the hypothalamohypophysial-thyroid axis.

Animals↗
PubMed1990

Galanin is a physiological regulator of spontaneous pulsatile secretion of growth hormone in the male rat.

To determine whether galanin (GAL), a 29-amino acid neuropeptide, plays a role in the physiological regulation of the pulsatile secretion of GH and PRL in the male rat, secretory patterns of both hormones were studied in freely moving animals after GAL passive immunoneutralization. Adult male Sprague-Dawley rats were equipped with iv and intracerebroventricular catheters. After 7 days, 3 microliters of a specific GAL antiserum (GAL-AS) or normal rabbit serum (NRS; controls) were infused in the third ventricle of 10 rats, 25 and 1 h before the animals were bled every 15 min for 6 h (1000-1600 h). Plasma GH and PRL concentrations were measured by RIA, and the hormonal secretory patterns were analyzed by the PULSAR program. Control rats, treated with NRS, displayed typical GH secretion, with pulses of high amplitude (167 +/- 27 ng/ml) and low frequency (2.4 +/- 0.2 pulses/6 h), separated by periods of low trough levels (3.8 +/- 0.6 ng/ml). Rats treated with GAL-AS had altered pulsatile GH secretion. Pulse height was markedly reduced (77 +/- 15 ng/ml; P less than 0.01 vs. controls), and peak frequency was higher (3.6 +/- 0.5 pulses/6 h; P less than 0.05), while GH baseline levels and integrated GH secretion over the 6-h sampling period remained unaltered. Injection of rat GH-releasing hormone (1 microgram/rat, iv) caused a similar GH stimulation in both groups of rats, as determined by the peak GH response at 5 min (368 +/- 112 vs. 342 +/- 81 ng/ml) or by the integrated GH response over 1 h (5.13 +/- 1.30 vs. 4.77 +/- 1.15 micrograms.min/ml in NRS- and GAL-AS-treated rats, respectively; P less than 0.05). In contrast to GH, pulsatile secretion of PRL was not affected by the GAL-AS treatment. These results indicate that GAL is a physiological regulator of spontaneous pulsatile secretion of GH, but not PRL, in the male rat. The influence of GAL on GH secretion appears to be exerted within the hypothalamus, mainly by a stimulation of GRF secretion. However, the changes in GH pulse frequency observed after GAL immunoneutralization suggest that GAL might also influence the somatostatin inhibitory tone.

Animals↗
PubMed1979

Immunoreactive and biologically active somatostatin-like material in rat retina.

Somatostatin-like activity, as determined by radioimmunoassay and bioassay, is present in HCl extracts of rat retina. The concentrations of immunoreactive somatostatin are 612 +/- 43 (mean +/- SEM)pg per whole retina of 0.621 +/- 0.044 pg/microgram of protein in retinas from rats killed by decapitation, values which are not significantly different from those in retinas from rats killed by ether inhalation. The immunoreactive somatostatin was partially purified and concentrated by immunoaffinity chromatography. Both the crude retinal extracts and the immunoaffinity-purified immunoreactive somatostatin inhibited, in a dose-related manner, the release of rat growth hormone from dispersed rat anterior pituitary cells in culture. When the immunoaffinity-purified immunoreactive somotostatin was subjected to gel filtration chromatography, 96% of the recovered somatostatin eluted as a peak corresponding in position to that of synthetic somatostatin. Retinas from a group of rats with hereditary degeneration of the photoreceptor cells and another group of rats studied 1 year after transection of the optic nerves demonstrated an increased concentration of immunoreactive somatostatin compared to controls.

Animals↗
PubMed1979

The use of length of stay distributions to predict hospital discharges.

Many hospital admissions scheduling or admissions control systems reported in the literature rely on estimates of future discharges to help control the variance in daily patient census. One of the two most frequently reported methods of estimating discharges attempts to explain the variance in historical length of stay (LPS) data. This paper explores the relationship between LOS variance explanation and the ability to predict discharges and concludes that even a large improvement in the ability to explain LOS variance will only marginally reduce the errors in the associated discharge predictions. In drawing this conclusion, a general discharge prediction model is developed and a more relevant statistic than per cent variance explained is introduced.

Admitting Department, Hospital↗
PubMed1979

Effect of anterior hypothalamic lesions on neurohypophysial and peripheral tissue concentrations of somatostatin in the rat.

Somatostatin (SRIF) is present in nerve endings in the median eminence (ME) and posterior pituitary. Hypothalamic SRIF containing neuronal perikarya are predominantly located in the anterior hypothalamic area (AHA), a region implicated in the inhibitory control of GH secretion. The effect of AHA lesions on SRIF in the ME, posterior pituitary, pancreas, stomach, and small intestine was studied in the rat in order to elucidate the source of ME and posterior pituitary SRIF and to determine if depletion of hypothalamic SRIF affects peripheral organ concentrations of the peptide. Lesioned animals showed a highly significant (P less than 0.01) 83% and 82% reduction in ME and posterior pituitary SRIF and to determine if depletion of hypothalamic SRIF affects peripheral organ concentrations of the peptide. Lesioned animals showed a highly significant (P less than SRIF concentrations in the pancreas, stomach, and small intestine of the lesioned animals. Plasma and pancreatic insulin and pancreatic glucagon were likewise unchanged. These data suggest that the hypothalamic SRIF pathway begins in the AHA, from where axons of somatostatinergic neurosecretory neurons project to both ME and posterior pituitary. AHA lesions have no effect on gut and pancreatic SRIF or pancreatic insulin and glucagon.

Animals↗
PubMed1979

Chromatographic and biological properties of immunoreactive somatostatin in hypothalamic and extrahypothalamic brain regions of the rat.

A sheep antiserum to somatostatin was used to develop RIA and immunoaffinity chromatography methods for the study of immunoreactive somatostatin (IRS) in brain tissue. IRS extracted from rat median eminence, anterior hypothalamic-preoptic area, amygdala, and parietal cortex bound reversibly to immunoaffinity columns, providing a technique for concentration and partial purification. Immunoaffinity purified IRS from each of the four brain regions eluted as four peaks on gel filtration chromatography. Each peak possessed biological activity, as determined by inhibitory effects on the release of GH from cultured rat anterior pituitary cells. No differences were detected by the methods employed between IRS from the anterior hypothalamic-preoptic area, which is rich in IRS-containing neuronal cell bodies, and that from the median eminence, where IRS is localized predominantly in nerve terminals.

Animals↗
PubMed1979

Episodic and TRH induced growth hormone release in primary hypothyroidism of man and rat.

In 27 hypothyroid subjects studied over 20 to 120 minutes, the concentration of serum growth hormone (GH) was variable with the amplitude and frequency of the secretory patterns similar to those reported by others for normal individuals. Serum GH, after the administration of thyrotropin releasing hormone (TRH) did not differ from values observed as spontaneous surges, in contrast to a consistent increase in thyrotropin and prolactin. Episodic secretion of GH persisted in thyroidectomized rats and did not differ significantly from that present in intact controls. It is concluded that episodic GH secretion is not abolished in primary hypothyroidism and that TRH is not a constant GH secretagogue in human subjects with hypothyroidism.

Adolescent↗