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Biomedical subjects

M Hall

Publications and source records attributed to M Hall.

At least 325 records · Page 18Linked to original sources
PubMed1977

High density lipoprotein metabolism in man.

The turnover of (125)I-high density lipoprotein (HDL) was examined in a total of 14 studies in eight normal volunteers in an attempt to determine the metabolic relationship between apolipoproteins A-I (apoA-I) and A-II (apoA-II) of HDL and to define further some of the determinants of HDL metabolism. All subjects were first studied under conditions of an isocaloric balanced diet (40% fat, 40% carbohydrate). Four were then studied with an 80% carbohydrate diet, and two were studied while receiving nicotinic acid (1 g three times daily) and ingesting the same isocaloric balanced diet. The decay of autologous (125)I-HDL and the appearance of urinary radioactivity were followed for at least 2 wk in each study. ApoA-I and apoA-II were isolated by Sephadex G-200 chromatography from serial plasma samples in each study. The specific activities of these peptides were then measured directly. It was found that the decay of specific activity of apoA-I and apoA-II were parallel to one another in all studies. The mean half-life of the terminal portion of decay was 5.8 days during the studies with a balanced diet.Mathematical modeling of the decay of plasma radioactivity and appearance of urinary radioactivity was most consistent with a two-compartment model. One compartment is within the plasma and exchanges with a nonplasma component. Catabolism occurs from both of these compartments. With a balanced isocaloric diet, the mean synthetic rate for HDL protein was 8.51 mg/kg per day. HDL synthesis was not altered by the high carbohydrate diet and was only slightly decreased by nicotinic acid treatment. These perturbations had effects on HDL catabolic pathways that were reciprocal in many respects. With an 80% carbohydrate diet, the rate of catabolism from the plasma compartment rose by a mean of 39.1%; with nicotinic acid treatment, it fell by 42.2%. Changes in the rate of catabolism from the second compartment were generally opposite those in the rate of catabolism from the plasma compartment, suggesting that these two catabolic pathways may be reciprocally regulated.

Adolescent↗
PubMed1976

Rhodopsin in the rod outer segment plasma membrane.

Isolated frog retinas were incubated in vitro with a 4-h pulse of [3H]leucine, then chased for 32 h with a nonradioactive amino acid mixture. At the end of the incubation, light and electron microscope autoradiograms were prepared from some of the retinas. The autoradiograms revealed: (a) intense radioactivity in the basal disks of the rod outer segments, (b) diffuse label evenly distributed throughout the rod outer segments, and (c) a high concentration of label in the entire rod outer segment plasma membrane. Incubation under identical conditions, but with puromycin added, significantly inhibited the labeling of all of these components. To identify the labeled proteins, purified outer segments from the remaining retinas were analyzed biochemically by SDS disc gel electrophoresis and gel filtration chromatography. SDS gel electrophoresis showed that about 90% of the total rod outer segment radioactivity chromatographed coincident with visual pigment, suggesting that the radiolabeled protein in the plasma membrane is visual pigment. Gel filtration chromatography demonstrated that the radiolabeled protein co-chromatographed with rhodopsin rather than opsin, and that the newly synthesized visual pigment is both the basal disks and the plasma membrane is present in the native configuration.

Animals↗
PubMed1976

Separation of benefin and trifluralin by gas chromatography using a liquid crystal column.

Benefin (N-[n-butyl]-N-ethyl-2,6-dinitro-alpha, alpha, alpha-trifluoro-p-toluidine) and trifluralin (2,6-dinitro-N,N-di-n-propyl-alpha, alpha, alpha-trifluoro-p-toluidine) (Figure 1) are isomeric preemergent herbicides (1,2). As they possess different activities, their use necessitates the development of a routine analytical method which differentiates between them. The separation of these isomers by gas-liquid chromatography (GLC) using conventional column packings has proved extremely difficult. Two partly successful separations have been previously reported to date. A partial separation was obtained using a Durapak-Carbowax 400/Poracil C column (3) and a complete separation using a column packed with a monomolecular layer of Carbowax 20M on Chromosorb W (4). Unfortunately, this latter column has a very limited life and the analysis time is 25 minutes. This paper reports a rapid and reproducible separation of benefin and trifluralin using a liquid crystal stationary phase.

Chromatography, Gas↗
PubMed1976

Multiple pigmented naevi in an albino.

A case of pigmented naevi arising in an albino is described. The histological appearance of a naevus is described in the nature of the pigment discussed.

Albinism↗
PubMed1976

The adenosine triphosphate content and lactic acid production of guinea-pig skin after mild heat damage.

The depletion of adenosine triphosphate in skin after mild thermal injury is not large enough to be accounted for by loss of oxidative respiration. Measurement of lactic acid production by skin suggest that glycolysis is less sensitive to heat damage than is oxygen uptake. It is therefore likely that glycolysis makes a large contribution to the relatively high levels of ATP persisting in heat damaged skin.

Adenosine Triphosphate↗
PubMed1975

Maximum compliance and the symptom of fullness in Meniere disease.

The symptom of fullness in Meniere disease was investigated in relation to measurements of maximum compliance (Cm) at the eardrum. The symptom of fullness is considered to be related to an increase in inner ear fluid pressure in Meniere disease. The Cms between ears were measured and compared for 36 patients with Meniere disease and the symptom of fullness in only one ear (full ear). A comparison of the Cm between the full ear and nonfull ear showed that the Cm was reduced for 32 of the patients. The data were interpreted as indicating that the Cm can be affected by pathological mechanical changes in the inner ear.

Compliance↗
PubMed1975

Recovery of yeast from vented blood culture bottles.

Rates of isolation of yeasts from blood cultures were significantly enhanced by venting vacuum blood culture bottles in studies of both stimulated and patients' blood cultures; however, the time interval to detection of positivity of yeasts in the clinical studies was significantly (P less than 0.01) shorter in a vented bottle with biphasic brain heart infusion medium than in a vented bottle with soybean-casein digest broth. The mean time intervals to detection of positivity were 2.6 days in the former and 5.2 days in the latter.

Air↗
PubMed1975

Effects of atmosphere of incubation and of routine subcultures on detection of bacteremia in vacuum blood culture bottles.

Studies comparing isolation rates of bacteria and yeasts from vented and unvented vacuum blood culture bottles containing soybean-casein digest broth showed significantly more frequent and more rapid recovery of Candida and Pseudomonas from the vented bottle and no other statistically significant differences between the two. Subculture of bottles on the day of their collection was shown to accelerate recovery of 48% of positive cultures by day 1. A second subculture of known positive cultures yielded additional organisms in 1.5% of cultures.

Air↗
PubMed1975

Effects of thrombin treatment of preparations of factor VIII and the Ca2+-dissociated small active fragment.

When human, canine, or bovine factor VIII preparations are chromatographed on 4% agarose at ionic strength 0.2, the factor VIII activity elutes as a single peak in the void volume with slight tailing. Incubation of such preparations with dilute (0.01 U/ml) highly purified thrombin results in some activation of factor VIII. Chromatography of such incubation mixtures, under the same conditions as before, results in elution of two peaks of factor VIII activity one in the void volume and one much later with marked tailing. The void volume peak has most of the protein and some factor VIII activity. These void volume fractions also contain all the von Willebrand factor activity of thrombin-treated bovine preparations. Longer treatment with thrombin, or treatment with stronger thrombin, appears to shift much more of the procoagulant activity to the later eluting peak. Also, when the peak of factor VIII activity, found in the void volume after thrombin treatment, was again incubated with dilute thrombin, an increase in factor VIII activity occurred. Chromatography of this incubation mixture demonstrated only a small amount of activity in the void volume, while the bulk of the activity was present in the second peak. On the other hand, thrombin treatment of factor VIII activity from peak 2 caused a rapid decline of activity instead of a further increase. It is proposed that the residual factor VIII activity found in the void volume represents unreacted factor VIII, while the late eluting peak represents thrombin-activated material that is of smaller apparent size. The late eluting peak differs from the small active factor VIII fragment obtained by Ca2+ dissociation, as the latter can be activated by thrombin. A similar set of experiments was performed using ultracentifugation of bovine factor VIII preparations on sucrose density gradients. Results of these experiments agreed completely with those obtained with get chromatography. Preparations made from human hemophilic plasma, by the procudure employed in the purification of human factor VIII, were also incubated with thrombin and chromatographed. von Willebrand factor was again found only in the void volume fractions, but there was no factor VIII activity in any fractions eluted. In other control experiments, activated and unactivated factor VIII fractions did not clot fibrinogen and contained no assayable factor IX or X. The thrombin-modified factor VIII of small size was inactivated by both a naturally occurring human inhibitor to factor VIII and the gamma globulin fraction of a rabbit antisera produced against the calcium-dissociated small active factor VIII fragment.

Animals↗