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Biomedical subjects

G B West

Publications and source records attributed to G B West.

At least 19 recordsLinked to original sources
PubMed2004

Retrospective study of mercury in raccoons (Procyon lotor) in south Florida.

Museum and recent collections of raccoon hair were used to assess whether temporal or spatial trends existed in MMHg distributions in south Florida. The hypothesis that MMHg in raccoon hair had remained the same since 1947 could not be rejected. Some sampling regions showed increases while others did not. However, large differences existed between sites, amounting to a factor of 20 for raccoons collected during 2000 and during the period prior to 1960 (museum samples). Raccoon feeding behavior and the production of MMHg most probably accounted for the spatial differences. Large differences in MMHg concentrations existed in different tissues ranging in order of hair, liver, kidney, muscle, heart, brain, and blood in their respective ratios to blood: 96:10:6:5:4:2.5:1. Liver Hg is 7% MMHg, while hair Hg is 99% MMHg. These associations appear largely regulated by metabolic processes. Speciation of Hg is very important for gaining an understanding of ecosystem and organism Hg dynamics. Further work is needed to establish whether Se plays a role in Hg sequestration and whether hair Hg is a good surrogate for estimating Hg concentrations in other tissues in south Florida raccoon populations.

Animal Structures↗
PubMed2001

A general model for ontogenetic growth.

Several equations have been proposed to describe ontogenetic growth trajectories for organisms justified primarily on the goodness of fit rather than on any biological mechanism. Here, we derive a general quantitative model based on fundamental principles for the allocation of metabolic energy between maintenance of existing tissue and the production of new biomass. We thus predict the parameters governing growth curves from basic cellular properties and derive a single parameterless universal curve that describes the growth of many diverse species. The model provides the basis for deriving allometric relationships for growth rates and the timing of life history events.

Animals↗
PubMed2001

Effects of size and temperature on metabolic rate.

We derive a general model, based on principles of biochemical kinetics and allometry, that characterizes the effects of temperature and body mass on metabolic rate. The model fits metabolic rates of microbes, ectotherms, endotherms (including those in hibernation), and plants in temperatures ranging from 0 degrees to 40 degrees C. Mass- and temperature-compensated resting metabolic rates of all organisms are similar: The lowest (for unicellular organisms and plants) is separated from the highest (for endothermic vertebrates) by a factor of about 20. Temperature and body size are primary determinants of biological time and ecological roles.

Amphibians↗
PubMed1999

The fourth dimension of life: fractal geometry and allometric scaling of organisms.

Fractal-like networks effectively endow life with an additional fourth spatial dimension. This is the origin of quarter-power scaling that is so pervasive in biology. Organisms have evolved hierarchical branching networks that terminate in size-invariant units, such as capillaries, leaves, mitochondria, and oxidase molecules. Natural selection has tended to maximize both metabolic capacity, by maximizing the scaling of exchange surface areas, and internal efficiency, by minimizing the scaling of transport distances and times. These design principles are independent of detailed dynamics and explicit models and should apply to virtually all organisms.

Animals↗
PubMed1999

Examining the use of tobacco on college campuses.

The authors used the Health Risk Behavior Survey for University Students to assess the prevalence of tobacco use among undergraduates in the Florida state university system. They examined the relationships of gender, marital situation, and minority status to 6 smoking behaviors (tried cigarettes, smoked regularly, tried to quit smoking, age when first smoked regularly, number of cigarettes smoked in the last month, and number of days smoked in the past month). Findings suggested that White students were more likely than minority students to try cigarettes and women more likely than men to smoke regularly. Married students smoked more regularly than others and were less likely than single students to have tried to quit smoking. The investigators suggested analyzing latent behaviors associated with smoking and called for a national meta-analysis of data from smoking studies to help clinicians deal with student tobacco use.

Adolescent↗
PubMed1997

A general model for the origin of allometric scaling laws in biology.

Allometric scaling relations, including the 3/4 power law for metabolic rates, are characteristic of all organisms and are here derived from a general model that describes how essential materials are transported through space-filling fractal networks of branching tubes. The model assumes that the energy dissipated is minimized and that the terminal tubes do not vary with body size. It provides a complete analysis of scaling relations for mammalian circulatory systems that are in agreement with data. More generally, the model predicts structural and functional properties of vertebrate cardiovascular and respiratory systems, plant vascular systems, insect tracheal tubes, and other distribution networks.

Animals↗
PubMed1996

Gender and marital differences for risk taking among undergraduates.

The authors report the frequency of behaviors which relate to intentional and unintentional injuries in the undergraduate population in Florida (N = 1150). Comparisons of risk behavior are made for men versus women and married versus unmarried students. The findings suggest that college students frequently participate in behaviors which can lead to injury.

Accidents, Traffic↗
PubMed1990

Further thoughts on mast cells, calcium channels and histamine release.

Calcium movements across membranes of mast cells represent a major target for effective anti-allergic drugs, as these are essential events linking stimulation to secretion. Using isolated peritoneal mast cells from two types of genetically different rats and a blocker of the entry of calcium ions into cells, histamine release induced by antigen, calcium ionophore and potassium (in a lowered calcium medium) has been followed. Lower concentrations of the calcium entry blocker were required to inhibit potassium-induced release than those needed for release induced by allergic and other non-allergic stimuli, suggesting that different specialised calcium channels are involved in histamine release from rat mast cells.

Animals↗
PubMed1987

Calcium channels and histamine release from mast cells.

Using isolated peritoneal mast cells from two types of genetically different rats, histamine release induced by allergic stimuli was inhibited, in all cases except one, by significantly lower concentrations of an intracellular calcium antagonist than those required to inhibit release induced by a calcium ionophore. The exception related to inhibition of histamine release induced by clinical dextran in NR rats (which are relatively less sensitive to dextran than are control rats) as the concentrations required were of a similar order as those needed to inhibit release by ionophores. The data further support the suggestion that there are different calcium channels involved in the different release processes.

Animals↗
PubMed1986

Calcium and histamine release from mast cells.

The role of calcium in the process of histamine release from isolated rat peritoneal mast cells and in the pathophysiology of immediate hypersensitivity reactions has been further studied using the intracellular calcium antagonist, TMB-8. Inhibition by TMB-8 of histamine release from mast cells induced by allergic stimuli was found but higher concentrations were needed for reducing release induced by ionophores and activators of calcium gates. This suggests that there are different calcium channels involved in the different release processes.

Animals↗
PubMed1985

Thoughts on mast cells, histamine release and immunoglobulin E.

It is well known that the polysaccharide, dextran, stimulates rat mast cells to undergo histamine secretion, probably by interaction with cell-fixed IgE. Passive sensitisation with antigens greatly enhances histamine release induced in vitro by dextran, and removal of IgE from the cells by acid pH abolishes this release. The importance of IgE antibodies for histamine release from mast cells by agents other than dextran is also well recorded. For example, acetylcholine induces a non-immunological release which is potentiated by the presence of IgE. A link may also exist between cholinergic agents and substance P, a polypeptide which releases histamine by acting on specific receptors and not through interaction with cell-bound IgE. Attempts are made here to gather together some of the physiological and pathological processes involved.

Acetylcholine↗
PubMed1984

Histamine release from mast cells of the rat.

The relative activities of 12 agents inducing anaphylactoid oedema in the paws of two types of genetically different rats have been compared with those inducing histamine release from isolated peritoneal cells. Four groups were identified - group 1 where activities were much higher in R rats than in NR rats, doses in vivo being in all cases much lower than those required in vitro; group 2 where activities were similar in the two types of rat, doses in vivo again being relatively much lower; group 3 where activities were similar in both types of rat though doses in vivo were relatively high; group 4 where activities were similar in both types of rat, but doses in vivo were relatively extremely high. Only the activities of releasers in groups 1, 2 and 3 (represented by dextran, concanavalin A and antigen) required calcium ions in vitro and were potentiated by phosphatidyl serine; they were potentiated in vivo by insulin and inhibited by glucose.

Animals↗