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G Major

Publications and source records attributed to G Major.

33 records · Page 2Linked to original sources
PubMed1992

Dendritic morphology of pyramidal neurones of the visual cortex of the rat. IV: Electrical geometry.

Features of the dendritic morphology of pyramidal neurones of the visual cortex of the rat that are relevant to the development of models of their passive electrical geometry were investigated. The sample of 39 neurones that was used came from layers 2/3 and 5. They had been recorded from and injected intracellularly with horseradish peroxidase (HRP) in vitro as part of a previous study (Larkman and Mason, J. Neurosci 10:1407, 1990). These cells had been reconstructed and measured previously by light microscopy. The relationship between the diameters of parent and daughter dendrites during branching was examined. It was found that most dendrites did not closely obey the "3/2 branch power relationship" required for representation of the dendrites as single equivalent cylinders. Estimates of total neuronal membrane area ranged from 27,100 +/- 7,900 microns2 for layer 2/3 cells to 52,200 +/- 11,800 microns2 for thick layer 5 cells. Dendritic spines contributed approximately half the total membrane area. Both neuronal input resistance and the ratio of membrane time constant to input resistance were correlated with neuronal membrane area as measured anatomically. The relative electrical lengths of the different dendrites of individual neurones were investigated, by using simple transformations to take account of the differences in diameter and spine density between dendritic segments. A novel "morphotonic" transformation is described that represents the purely morphological component of electrotonic length. Morphotonic lengths can be converted into electrotonic lengths by division by a "morphoelectric factor" ([Rm/Ri]1/2). This procedure has the advantage of separating the steps involving anatomical and electrical parameters. These transformations indicated that the dendrites of the apical terminal arbor were much longer electrically than the basal or apical oblique dendrites. In relative electrical terms, most apical oblique trees arose extremely close to the soma, and terminated at similar distances to the basals. These results indicate that the dendrites of these pyramidal cells cannot be represented as single equivalent cylinders. The electrotonic lengths of the dendrites were calculated by using the electrical parameters specific membrane capacitance (Cm), intracellular resistivity (Ri), and specific membrane resistivity (Rm). Conventional values were assumed for Cm (1.0 muFcm-2) and Ri (100 omega cm), but three different Rm values were used for each cell. Two of these were within the conventionally accepted range (10,000-20,000 omega cm2), while the third value was an order of magnitude higher, in line with some recent evidence from modeling and whole-cell recording studies.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Techniques for obtaining analytical solutions to the multicylinder somatic shunt cable model for passive neurones.

The somatic shunt cable model for neurones is extended to the case in which several equivalent cylinders, not necessarily of the same electrotonic length, emanate from the cell soma. The cable equation is assumed to hold in each cylinder and is solved with sealed end conditions and a lumped soma boundary condition at a common origin. A Green's function (G) is defined, corresponding to the voltage response to an instantaneous current pulse at an arbitrary point along one of the cylinders. An eigenfunction expansion for G is obtained where the coefficients are determined using the calculus of residues and compared with an alternative method of derivation using a modified orthogonality condition. This expansion converges quickly for large time, but, for small time, a more convenient alternative expansion is obtained by Laplace transforms. The voltage response to arbitrary currents injected at arbitrary sites in the dendritic tree (including the soma) may then be expressed as a convolution integral involving G. Illustrative examples are presented for a point charge input.

Animals↗
PubMed1989

Public perception of risk and its consequences: the case of a natural fibrous mineral deposit.

A public authority building a breakwater and other harbour facilities at a small seaport (population 3000) had short-term requirements for 261,000 tonnes of rock and ultimately for 1,000,000 tonnes. A suitable quarry was found about 11 km from the port but unfortunately the rock was found to be contaminated to a small extent with a fibrous mineral identified with the analytical transmission electron microscope as a non-commercial type of fine amphibole with many long fibres. Quarrying only was intended and there were no plans to crush the rock, but the projected work soon brought complaints from local residents, who expressed fears concerning risks to health from what soon became known as 'the asbestos mine'. These complaints posed a dilemma for both the construction and health authorities; they were forcefully expressed, and residents were supported by local newspapers, municipal authorities and regional politicians. The Land and Environment Court ordered (by consent) that the construction authority 'take all reasonable measures to ensure that no loose asbestos material and no rock with any asbestos material exposed on the surface (is) removed from the site'. Personal monitoring of quarry workmen by the membrane filter method and ambient air monitoring near residents' homes with analysis by electron microscope showed that only insignificant concentrations of airborne fibres were present. The breakwater was ultimately completed after much delay and extra expense. Other and greater risks to health and safety, such as the transport of liquid chlorine through the centre of the town to the fish processing plant and the storage, distribution and transport of petroleum products from the nearby regional facilities, were not perceived as such by the residents.

Air Pollutants↗
PubMed1983

Development of a micro enzyme-linked immunosorbent assay for antibodies against liver-specific membrane lipoprotein.

Guinea pig antisera raised against human and rabbit liver-specific membrane lipoprotein (LSP) have been used to develop a rapid, reproducible and sensitive solid-phase, enzyme-linked immunosorbent assay (ELISA). The ELISA was used in a series of cross-inhibition experiments to define and quantitate the antigenic specificities of these antisera. The results confirm previous findings that LSP contains both liver-specific and liver non-specific antigens. In addition, it is shown that both human and rabbit LSP contain liver-specific antigens that are species-specific, as well as others that are species cross-reactive. Binding to human LSP was detected by the ELISA with 11 of 13 anti-LSP-positive (by radioimmunoassay) sera from patients with HBsAg-negative chronic active hepatitis. Similar binding was also found with 10 of 11 sera from patients with systemic lupus erythematosus and with 7 of 14 with rheumatoid arthritis --all of which were negative for anti-LSP by radioimmunoassay. It is suggested that immune complexes in these sera might bind to IgG-Fc receptors in LSP and that caution should be exercised in the interpretation of data from ELISA-based studies of anti-LSP in human sera.

Antibodies↗
PubMed1978

A comparative study of Butacote and Naprosyn in ankylosing spondylitis.

A double-blind, cross-over comparison of Naprosyn (naproxen) 750 mg daily and Butacote (enteric-coated phenylbutazone) 300 mg daily was carried out in a multi-centre trial. Twenty-five patients, mostly male and under 40 years of age, were entered. After a 2-week period in which any existing anti-inflammatory drugs were tailed off, patients were entered into the trial and treated for 1 month with each drug. Patients were assessed at 4-weekly intervals. Both drugs significantly reduced morning stiffness. Morning pain and discomfort and wall-tragus distance were also significantly reduced by both drugs during the trial. Results of the Schober test showed improvement during both treatment periods. There were no overall statistically significant differences between the effects of the 2 drugs on objective parameters. However, overall subjective assessment of symptoms showed a greater improvement on Butacote. Treatment preferences by physician and subjective assessment by the patient both favoured Butacote but the difference between the 2 drugs was not statistically significant. Side effects were mostly of a minor nature. One patient had to discontinue the trial, due to indigestion while taking Butacote.

Adult↗
PubMed1974

Vision at work visual defect and the visual demand of tasks.

Several related studies of visual tasks in a large communications undertaking have revealed much defect of vision and many sources of visual fatigue and inefficiency. The nature of visual fatigue is described briefly and a programme to facilitate visual tasks is outlined.

Journal Article↗
PubMedDate not supplied

Cigarette smoking as a risk factor for atherosclerosis. Study of the biologic changes consecutive to smoking in normals, in patients with coronary heart disease and in diabetics.

The atherogenic action of smoking was studied in 112 male subjects with a mean age of 48.6 years, of whom 40 healthy controls, 40 patients with compensated coronary heart disease and 32 diabetics without ketoacidosis. Sixty-two were chronic smokers consuming 19.4 cigarettes/day and the remaining 50 did not smoke. The investigations performed in all the subjects were: erythrocyte count, hemoglobin and hematocrit determination, leukocyte absolute and differential counts, coagulation time (Howell), fibrinogen assay, platelet count and aggregability, total lipids, triglycerides, uric acid, creatininemia and blood glucose determinations. In the group of smokers, these investigations were repeated 60 min after the smoking of two cigarettes. Comparison of the results obtained in smokers and non-smokers, as well as before and after smoking, in the latter group, suggests that the influence of smoking upon the serum lipoprotein fractions is of little importance in atherogenesis, while its action upon the coagulation factors and the blood glucose level seems to have a real atherogenic role.

Adult↗