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Biomedical subjects

S M Ross

Publications and source records attributed to S M Ross.

At least 19 recordsLinked to original sources
PubMed1992

The effect of estrogen treatment on scopolamine inhibition of lordosis.

Previous evidence indicates that the cholinergic muscarinic antagonist, scopolamine, inhibits lordosis in female rats. In the experiments reported here, the effects of various doses and repeated administrations of estrogen on the scopolamine inhibition of lordosis were examined. In the first experiment, intraperitoneal injections of scopolamine (1 mg/rat) completely inhibited lordosis in ovariectomized rats primed with low doses of estradiol benzoate (0.25 or 0.5 micrograms for 3 days) and progesterone (500 micrograms). However, scopolamine was significantly less effective in inhibiting lordosis in females primed with a higher dose of estradiol benzoate (25 micrograms for 3 days) and progesterone (500 micrograms). When hormone priming was repeated on subsequent weeks, scopolamine continued to inhibit lordosis in females that received 0.25 micrograms estradiol benzoate but was less effective in females primed with 0.5 micrograms. Scopolamine failed to inhibit lordosis in females treated with 25 micrograms estradiol benzoate on these later tests. In the second experiment, various doses of scopolamine (1, 2, or 4 mg/rat) were administered intraperitoneally to females primed with the highest dose of estradiol benzoate (25 micrograms) and progesterone (500 micrograms). Lordosis was inhibited equally by all scopolamine doses during the first week. As in the first experiment, scopolamine failed to inhibit lordosis at all doses on subsequent weeks of testing. These results indicate that the ability of scopolamine to inhibit lordosis is reduced by increasing the dose or the number of estrogen exposures. Because higher doses of scopolamine failed to restore its inhibitory effect on lordosis an upregulation of muscarinic receptors by estrogen cannot account for the reduced effectiveness of scopolamine.

Animals↗
PubMed1992

Professional pilots' evaluation of the extent, causes, and reduction of alcohol use in aviation.

Pilots holding the ATP rating were surveyed to obtain judgments concerning the seriousness of the alcohol problem in various areas of aviation, the reasons for alcohol use, and the probable effectiveness of strategies intended to reduce alcohol use in aviation. Alcohol use was judged to be a more serious problem in general aviation than in corporate, charter, regional, and major airline activities. Respondents identified the individual's inability to control alcohol use as a primary reason for drinking and flying, and they endorsed remedies that are directed toward those individuals who are seen as the source of the problem. Other factors considered important causes of drinking and flying included pilots' beliefs that they can compensate for alcohol's effects and their lack of knowledge about the rate of decrease in blood alcohol concentration (BAC) that occurs as a function of time and amount consumed.

Aerospace Medicine↗
PubMed1992

Synovial fluid stimulates the proliferation of rabbit ligament. Fibroblasts in vitro.

This study was designed to test the hypothesis that synovial fluid may be inhibitory to cell proliferation. The effects of bovine synovial fluid (SF) and hyaluronic acid (HA) on the proliferation of normal rabbit medial collateral ligament (MCL), anterior cruciate ligament (ACL), and MCL scar cells were therefore investigated. Cell lines established from rabbit tissues were plated, incubated, and allowed to attach before treatment with varying concentrations of SF, HA, and a balanced salt solution (BSS). The BSS group was added as a control to observe the effects of media dilution alone on cell proliferation. Cell numbers from each group were quantified at 24, 48, 72, and 96 hours. Results showed that for all cell types, cell proliferation during the log phase of growth was significantly stimulated by SF. Maximum stimulation occurred in 20% SF with stimulation decreasing at higher concentrations of SF. HA had virtually no effect on scar and ACL cells, and only a slight stimulatory effect on MCL cells. Media dilution had no effect on scar cells and began to inhibit cell proliferation of ACL and MCL cells only at high dilutions. These findings suggest that low concentrations of bovine SF stimulate proliferation of rabbit ligament and scar fibroblasts in vitro by a mechanism that appears not to involve HA. Even in high concentrations, SF was not inhibitory to proliferation. The implications of these findings to ligament healing and normal ligament physiology require further investigation.

Animals↗
PubMed1991

Effect of floor conditions upon frictional characteristics of squash court shoes.

Vertical (FN) and horizontal (FH) forces were recorded while four vertically-loaded court shoes were dragged horizontally across six types of floor surface. Variation in coefficient of limiting friction (FH/FN) between floor surfaces was greater than that between shoes. Squash strokes were also performed on the same surfaces during which FH/FN was calculated. Slips occurred on some surfaces either at heel contact or upon attainment of full-sole contact. It is concluded that the coefficient of limiting friction obtained during full-sole contact with the floor is a suitable means of distinguishing between tractional qualities of shoes. Alternatively, this measure is an inadequate predictor of the likelihood of slips in the game of squash racquets. Dusty floor conditions produce poor traction as does a damp sealed floor. As sweat droplets are unavoidable in the game, floors sealed with urethane represent a significant hazard. Bare, clean, wooden flooring which can absorb moisture represents a better surface than a sealed floor from the point of view of traction.

Biophysical Phenomena↗
PubMed1990

Combined DC and ELF magnetic fields can alter cell proliferation.

Effects of extremely-low-frequency (ELF) electromagnetic fields on proliferation of rabbit-ligament fibroblasts were examined. Markedly different effects, ranging from inhibition to stimulation of proliferation, were obtained, depending on the signal parameters of amplitude, frequency, and DC magnetic field. These results demonstrate that simple, single-frequency signals can have dramatic effects on ligament cells, which may be useful for bioelectrical stimulation of growth and repair. Also, the range of frequencies examined in this study covered those commonly used in transmission of electrical energy (50 or 60 Hz), which indicates that further study of possible effects of exposure to fields generated by power transmission equipment is warranted.

Animals↗
PubMed1990

Establishment and comparison of fibroblast cell lines from the medial collateral and anterior cruciate ligaments of the rabbit.

We have developed a procedure to explant fibroblasts from the anterior cruciate ligament (ACL) and the medical collateral ligament (MCL) of the rabbit knee, and have optimized conditions for maintaining them in culture. Maximal growth for both ACL and MCL cells was obtained with Dulbecco's modified Eagle's medium supplemented with 15% fetal bovine serum and 250 microM ascorbate. ACL and MCL fibroblasts displayed intrinsic differences in their responses to changes in culture parameters. Specifically, they displayed different growth responses when plated at different densities and responded to RPMI 1640 medium in very different ways. There were also biochemical differences between the cell types. Both cell types produced similar amounts of collagen in culture, but the ratio of type I to type III, the major collagen subtypes produced by these cells, were different. ACL fibroblasts produced 86.7% type I and 13.3% type III, and MCL fibroblasts produced 71.1% type I and 28.9% type III. In addition, total protein produced by ACL fibroblasts was higher than that produced by MCL cells. This confirms the suggestions of previous researchers that such differences might exist.

Animals↗
PubMed1990

Pilots' knowledge of blood alcohol levels and the 0.04% blood alcohol concentration rule.

A national sample of licensed pilots was surveyed regarding their knowledge of the Federal Aviation Administration's (FAA) 0.04% blood alcohol concentration (BAC) limit, the relationship between the number of drinks and BAC, and the manner in which BAC decays with time. A majority of the 1039 respondents were unaware of the 1985 0.04% BAC rule change. In addition, many lacked an understanding of the relationship between the amount of alcohol consumed and the resulting BAC, and of the rate at which BAC decays. The number of drinks necessary to raise BAC to specific levels was frequently overestimated, and the amount of time necessary for BAC to decay was frequently underestimated. These errors were more pronounced for moderate and heavy drinkers than for abstainers and infrequent drinkers. These results suggest that pilots could have difficulty if they attempt to use the 0.04% BAC value as a guide to safety in their flying activities.

Accidents, Aviation↗
PubMed1989

Studies on the alignment of fibroblasts in uniform applied electrical fields.

Uniform electrical fields have been applied to human gingival fibroblasts by means of uniform ionic currents passed through a thin chamber. Cells were observed to align in fields between 0.1 and 1.5 V/mm but did not display directed motion toward the anode or the cathode of the chamber. Statistical analysis of directional data was used to distinguish threshold levels of orientation at low field intensities, to quantify the dependence of alignment on time and field intensity, and to analyze differences between alignment of cells treated with the Ca2+ transport modifiers A23187, verapamil, and lanthanum. Alignment occurred at a steady rate and was dependent in a saturating fashion on field strength. The Ca2+ ionophore A23187 had a significant inhibitory effect on cell alignment in applied electrical fields; however, the Ca2+ channel blockers lanthanum and verapamil did not have a significant effect on alignment.

Biological Transport↗
PubMed1989

Self-efficacy in alcoholics: clinical validation of the Situational Confidence Questionnaire.

Recent theory and empirical data suggest that self efficacy plays an important role in resistance to relapse for substance abusers. This study investigated the validity of the Situational Confidence Questionnaire (SCQ), a new instrument designed to measure self-efficacy expectations in purported high-risk drinking situations. The SCQ was administered to 46 short-term sober (STS) and 25 long-term sober (LTS) alcoholics. STS subjects were newly admitted alcohol treatment patients and LTS subjects had been abstinent for at least one year. Results indicated significantly higher self efficacy for LTS subjects than for STS subjects on total score and on 7 of the 8 subscales (p less than .001). Stepwise discriminant analysis yielded a linear combination of three subscales to account for 49% of the total variance; 92% of the LTS and 65% of the STS subjects were correctly identified by the classification function. These results extended earlier work with the SCQ using newly sober subjects and, in addition, provide encouraging validity data for the SCQ.

Alcoholism↗
PubMed1989

Beta-N-oxalylamino-L-alanine action on glutamate receptors.

beta-N-Oxalylamino-L-alanine (L-BOAA) is a non-protein excitatory amino acid present in the seed of Lathyrus sativus L. This excitotoxin has been characterized as the causative agent of human neurolathyrism, an upper motor neuron disease producing corticospinal dysfunction from excessive consumption of the lathyrus pea. Previous behavioral, tissue-culture, and in vitro receptor binding investigations revealed that L-BOAA might mediate acute neurotoxicity through quisqualate (QA)-preferring glutamate receptors. The present study demonstrates the stereospecific action of L-BOAA on glutamate receptor binding in whole mouse brain synaptic membranes. L-BOAA was most active in displacing thiocyanate (KSCN)-sensitive specific tritiated (RS)-alpha-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) binding (i.e., QA receptor) (Ki = 0.76 microM) with a rank-order potency of QA greater than kainate greater than N-methyl-D-aspartate (NMDA). By contrast, the nonneurotoxic D-BOAA isomer (100 microM) was essentially inactive in displacing radioligands for glutamate receptors, except the NMDA site, where it was equipotent with L-BOAA. Scatchard analysis of L-BOAA displacement of specific [3H]AMPA binding indicated competitive antagonism (KD: control, 135 nM; L-BOAA, 265 nM) without a significant change in QA-receptor density, and Hill plots yielded coefficients approaching unity. Differential L-BOAA concentration-dependent decreases in specific [3H]AMPA binding were observed in synaptic membranes, indicating that the neurotoxin was more potent in displacing specific binding from frontal cortex membranes, followed by that for corpus striatum, hippocampus, cerebellum, and spinal cord. (ABSTRACT TRUNCATED AT 250 WORDS)

Alanine↗
PubMed1989

Students' time on learning tasks in special education.

The purpose of this study was to measure, through naturalistic observation procedures, the use of time among handicapped students in four special education alternatives--regular class, resource room, special class, and special school. The sample included 230 elementary age students enrolled in 58 classes in 16 schools. ANOVA comparisons revealed that the least restrictive alternatives, particularly the resource room, made more in-class learning time available. Discussion includes recommendations for increasing learning time.

Child↗
PubMed1988

Pilots' attitudes toward alcohol use and flying.

Questionnaires were sent to a national sample of licensed pilots. Respondents reported their flying experience and their drinking behavior. They also indicated the number of drinks that they believed could be safely consumed 3 hours (h) before flying or driving, and estimated the numbers of hours a person should wait, after drinking, before attempting to fly or drive. Similar questions were included regarding marijuana use. Respondents were much more conservative in their attitudes toward the use of alcohol prior to flying than prior to driving. This relationship held both for the number of drinks judged safe 3 h prior to flying or driving and for estimates of the waiting interval that would be appropriate following alcohol consumption. In addition, attitudes toward alcohol use were related to respondents' own drinking behavior, with moderate and heavy drinkers more tolerant of alcohol use in flying and driving situations than abstainers.

Adult↗
PubMed1987

Specific antagonism of excitotoxic action of 'uncommon' amino acids assayed in organotypic mouse cortical cultures.

Beta-N-Methylamino-L-alanine (BMAA) and beta-N-oxalylamino-L-alanine (BOAA) are chemically related excitant amino acids present in the seeds of Cycas circinalis and Lathyrus sativus, respectively. Consumption of these seeds has been linked to Guam amyotrophic lateral sclerosis (BMAA) and lathyrism (BOAA) (a form of primary lateral sclerosis). We report that the acute neuronotoxic actions of these amino acids are blocked selectively by specific glutamate receptor antagonists. Administration of BOAA and BMAA to neonatal mouse cortex explants (EC100 = 28 microM and 1.6 mM, respectively) rapidly induces postsynaptic vacuolation (PSV) and neuronal degeneration characterized by dark/shrunken (D/S) cells. BOAA-mediated neuronotoxic effects are attenuated in a concentration-dependent manner by cis-2,3-piperidine dicarboxylic acid (PDA), an antagonist of quisqualate (QA)-preferring and kainate (KA)-preferring glutamate receptors. PDA maximally protected against BOAA-induced PSV by 84% at 1 mM and D/S cells by 80% at 0.5 mM. BMAA-induced cellular changes were antagonized selectively in a concentration-dependent manner by 2-amino-7-phosphono-heptanoic acid (AP7), an N-methyl-D-aspartate (NMDA) glutamate-receptor antagonist. AP7 maximally protected against BMAA-induced PSV and D/S by 88% at 1.0 and 0.5 mM, respectively. These protective actions were selective and specific since AP7 failed to attenuate BOAA-induced alterations, and PDA was ineffective in ameliorating BMAA-induced changes. Other glutamate receptor antagonists (glutamic diethyl ester and streptomycin) failed to protect the explants from the destructive action of either toxin. Taken collectively, our data indicate that the acute neuronotoxic actions of BOAA and BMAA (or a metabolite) operate through different glutamate receptor species.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1987

Breast-feeding support.

With the objective of prolonging unsupplemented breast-feeding, three groups of breast-feeding mothers were provided with support by frequent home visits by different types of health workers (including a lay worker). A fourth group received limited support and a fifth group received no support. Significant differences were found between some of the groups, the lay worker having the greatest impact. The results indicate that a home visitation programme could be successful in promoting breast-feeding.

Adult↗
PubMed1987

Guam amyotrophic lateral sclerosis-parkinsonism-dementia linked to a plant excitant neurotoxin.

The decline in the high incidence of amyotrophic lateral sclerosis, parkinsonism, and Alzheimer-type dementia among the Chamorro population of the western Pacific islands of Guam and Rota, coupled with the absence of demonstrable viral and hereditable factors in this disease, suggests the gradual disappearance of an environmental factor selectively associated with this culture. One candidate is seed of the neurotoxic plant Cycas circinalis L., a traditional source of food and medicine which has been used less with the Americanization of the Chamorro people after World War II. Macaques were fed the Cycas amino acid beta-N-methylamino-L-alanine, a low-potency convulsant that has excitotoxic activity in mouse brain, which is attenuated by N-methyl-D-aspartate receptor antagonists. These animals developed corticomoto-neuronal dysfunction, parkinsonian features, and behavioral anomalies, with chromatolytic and degenerative changes of motor neurons in cerebral cortex and spinal cord. In concert with existing epidemiological and animal data, these findings support the hypothesis that cycad exposure plays an important role in the etiology of the Guam disease.

Amino Acids, Diamino↗
PubMed1987

Discovery and partial characterization of primate motor-system toxins.

beta-N-Oxalylamino-L-alanine (BOAA) and beta-N-methylamino-L-alanine (BMAA) are chemically related excitant amino acids isolated from the seed of Lathyrus sativus (BOAA) and Cycas circinalis (BMAA), consumption of which has been linked to lathyrism (an upper motor neuron disorder) and Guam amyotrophic lateral sclerosis (ALS), respectively. Both diseases are associated with degeneration of motor neurons. Experimentally, single doses of BOAA or BMAA induce seizures in neonatal mice and postsynaptic neuronal oedema and degeneration in explants of mouse spinal cord and frontal cortex. Preliminary studies show that these behavioural and pathological effects are differentially blocked by glutamate-receptor antagonists. In macaques, several weeks of daily oral doses of BOAA produce clinical and electrophysiological signs of corticospinal dysfunction identical to those seen in comparably well-nourished animals receiving a fortified diet based on seed of Lathyrus sativus. By contrast, comparable oral dosing with BMAA precipitates tremor and weakness, bradykinesia and behavioural changes, with conduction deficits in the principal motor pathway. BOAA and BMAA (or a metabolite thereof) are the first members of the excitotoxin family to have been shown to possess chronic motor-system toxic potential. These observations provide a rational basis for searching for comparable endogenous neurotoxins in sporadic and inherited forms of human motor neuron disease.

Alanine↗
PubMed1987

Specific antagonism of behavioral action of "uncommon" amino acids linked to motor-system diseases.

Beta-N-methylamino-L-alanine (BMAA) and beta-N-oxalylamino-L-alanine (BOAA) are chemically related amino acids present in the seeds of Cycas circinalis and Lathyrus sativus, respectively. Consumption of these seeds has been linked to Guam amyotrophic lateral sclerosis (BMAA) and lathyrism (BOAA; a form of primary lateral sclerosis). A single large dose of BOAA or BMAA causes seizures in newborn mice and postsynaptic neuronal edema and degeneration in CNS explants. We report that the acute neurotoxic actions of these amino acids are blocked selectively by specific glutamate-receptor antagonists (administered intracerebroventricularly) (i.c.v.) prior to the amino acid. Administration of BOAA i.c.v. to neonatal mice (ED100 = 50 micrograms) elicits a spectrum of time-dependent behavioral states including arm and leg rigidity, convulsions, and resting tremor. These are blocked in a dose-dependent manner by cis-2,3-piperidine dicarboxylic acid (PDA), an antagonist of quisqualate (QA)-preferring (A2) and kainate (KA)-preferring (A3) glutamate receptors (ED50s; 2.8 micrograms, rigidity; 1.4 micrograms, convulsions; 2.4 micrograms, resting tremor). BMAA induces a transitory hyperexcitable state followed by a long-lasting whole-body shake/wobble (ED100 = 1,000 micrograms, i.c.v.). These responses are antagonized selectively and dose-dependently by 2-amino-7-phosphonoheptanoic acid (AP7), an N-methyl-D-aspartate (NMDA) or A1 glutamate-receptor antagonist (ED50 = 0.45 microgram). Taken collectively, our data indicate that the acute neuronotoxic actions of BOAA and BMAA (or a metabolite) operate through different glutamate-receptor species. BMAA likely exerts most of its action indirectly via the A1 glutamate receptor, while BOAA acts principally at the A2 and/or A3 receptor.

2-Amino-5-phosphonovalerate↗