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Biomedical subjects

L M Parsons

Publications and source records attributed to L M Parsons.

68 records · Page 4Linked to original sources
PubMed1982

Characterization of nontypable Streptococcus pneumoniae-like organisms isolated from outbreaks of conjunctivitis.

From January through June 1980 seven colleges and universities in various parts of New York State (NYS) reported outbreaks of conjunctivitis affecting at least 1,500 students of both sexes. Of the 125 conjunctival swabs tested in our laboratory, organisms identified as nontypable Streptococcus pneumoniae were isolated in pure culture from 24% and in combination with other organisms from 22%. Although bile-soluble and susceptible to optochin, the isolates had a dry-colony appearance and no typable capsule with the Neufeld capsular-swelling test. Mouse passage of four representative NYS isolates did not stimulate production of a typable capsule. We subsequently chose to refer to these isolates as S. pneumoniae-like organisms. Of primary importance to our study, all NYS isolates tested were similar in biochemical and immunological reactions, antibiotic susceptibility, and virulence in mice. Of 18 strains referred to us from three other outbreaks (California, 1980; NYS, 1981; Illinois, 1981), four of the six tested biochemically gave the same biochemical reactions as the four NYS isolates, and 16 of the 18 tested immunologically reacted strongly with antisera produced against those four isolates, showing line(s) of identity with each other and with the NYS isolates.

Animals↗
PubMed1982

Rapidly developing functional tolerance to ethanol is accompanied by increased erythrocyte cholesterol in mice.

We investigated the time course for development of functional tolerance to the ataxic effects of ethanol in four genetically distinct mouse populations. Two inbred-strains (C57BL/6J and DBA/2J) and two lines of mice (long-sleep and short-sleep) selectively bred for differences in acute ethanol sensitivity were used. Mice were injected i.p. with ethanol in doses that produced ataxia and were tested repeatedly for their ability to balance on a wooden rod. When they regained their balance at threshold, brain ethanol levels were measured in some mice and booster injections of ethanol were administered to the remaining animals. This sequence was repeated for five injections, delivering a total of 6 g/kg of ethanol to the final group of animals. Functional tolerance developed in all four populations of mice as evidence by threshold brain ethanol levels that were significantly higher after two or three successive injections than after one injection. The magnitude of tolerance was not increased by practice on the dowel. To investigate whether alterations in membrane lipid composition accompanied this rapid development of tolerance, we used erythrocytes as a model system and measured the cholesterol and phospholipid content of their membranes. The erythrocyte membranes from ethanol-tolerant mice of each population contained more cholesterol than those from controls. The erythrocyte membrane phospholipid content of ethanol-tolerant animals changed only slightly in two populations.

Animals↗
PubMed1981

Optical information and practice in the discrimination of 3-D mirror-reflected objects.

Two studies of the discrimination of three-dimensional mirror-reflected objects were concerned with the influence of practice and stimulus information for shape, specifically binocular information and perspective transformations. In the first study subjects made 'same-different' responses to successively presented pairs of real objects, under binocular and monocular viewing conditions. In the second study subjects viewed object pairs on a rotating turntable, in five different displays. Neither binocular information nor perspective transformations contributed to isomorph discrimination. In both studies mental rotation and other less well specified strategies were employed. After practice, in contrast to previous reports, five of the six subjects in these studies produced reaction times unrelated to the orientation difference between the objects. These practice effects may reflect either extremely rapid rotation rates, the detection of rotationally invariant features, or the use of multiple strategies.

Cues↗
PubMed1979

Fluidity and lipid composition of mouse biomembranes during adaptation to ethanol.

Showing that ethanol added in vitro increased the fluidity of mouse erythrocyte and synaptosomal membranes and that the same membranes isolated from mice after chronic treatment with ethanol had increased cholesterol and were resistant to ethanol in vitro, the study suggests that the animals had adapted to the chronic presence of the drug by changing their membrane lipid composition to offset the fluidizing effects of ethanol.

Animals↗
PubMed1978

Increased cholesterol content of erythrocyte and brain membranes in ethanol-tolerant mice.

Mice were treated with ethanol for eight or nine days, using a liquid diet regimen known to produce physical dependence. In previous experiments, synaptosomal plasma membranes and erythrocyte ghosts from such ethanol-treated animals were found to be resistant to the fluidizing effects of ethanol in vitro, as measured by electron paramagnetic resonance. In the present experiments, corresponding membranes were analysed for phospholipid and cholesterol. The ratio of cholesterol to phospholipid was found to be significantly increased in both types of membrane after chronic ethanol treatment. The changed ratio was produced by an increase in cholesterol. There was little or no change in phospholipid content of the membranes. Increased cholesterol may explain the previously observed alteration of physical properties of the membranes.

Animals↗
PubMed1977

A scheme for identification of nonfermentative gram-negative bacteria.

A scheme was designed to speed the identification of 50 nonfermentative gram-negative bacteria to genus, species, and biotype using a minimal numer of biochemical tests. When the scheme was evaluated in our laboratory, one technologist identified 93.6% of 188 known isolates (46 species). Later another technologist, given 161 of the same isolates (46 species) as unknowns, identified 91.9%. The isolates that were misidentified in both cases were atypical organisms with aberrant biochemical reactions, plus 1 typical organism with a delayed oxidation of glucose.

Bacteriological Techniques↗
PubMed1975

Nonspecific resistance to Escherichia coli in mice.

Nonspecific cell-mediated immunity to a relatively virulent strain of Escherichia coli was studied in mice infected with Staphylococcus aureus and elicited with specific antigens. The infected and elicited mice were protected against as intraperitoneal challenge by E. coli for an observation period of 7 days, whereas normal mice, given the same number of bacteria, died within 18 to 24 h. However, the amount of time elapsing between elicitation and challenge greatly affected the rate of protection. Little or no protection was observed in mice injected with S. aureus but not elicited or in mice injected with staphylococcal antigens but not infected with staphylococci.

Animals↗
PubMedDate not supplied

Lateral cerebellar hemispheres actively support sensory acquisition and discrimination rather than motor control.

This study examined a new hypothesis proposing that the lateral cerebellum is not activated by motor control per se, as widely assumed, but is engaged during the acquisition and discrimination of tactile sensory information. This proposal derives from neurobiological studies of these regions of the rat cerebellum. Magnetic resonance imaging of the lateral cerebellar output nucleus (dentate) of humans during passive and active sensory tasks confirmed four a priori implications of this hypothesis. Dentate nuclei responded to cutaneous stimuli, even when there were no accompanying overt finger movements. Finger movements not associated with tactile sensory discrimination produced no dentate activation. Sensory discrimination with the fingers induced an increase in dentate activation, with or without finger movements. Finally, dentate activity was greatest when there was the most opportunity to modulate the acquisition of the sensory tactile data: when the discrimination involved the active repositioning of tactile sensory surface of the fingers. Furthermore, activity in cerebellar cortex was strongly correlated with observed dentate activity. This distinct four-way pattern of effects strongly challenges other cerebellar theories. However, contrary to appearances, neither our hypothesis nor findings conflict with behavioral effects of cerebellar damage, neurophysiological data on animals performing motor tasks, or cerebellar contribution to nonmotor, perceptual, and cognitive tasks.

Adult↗