Search PubMed⌕ Search

Biomedical subjects

J A Raymond

Publications and source records attributed to J A Raymond.

12 recordsLinked to original sources
PubMed2001

Semipurification and ice recrystallization inhibition activity of ice-active substances associated with Antarctic photosynthetic organisms.

Ice-active substances (IASs), i.e., macromolecular substances that modify the shape of growing ice crystals, were previously found to be associated with various terrestrial and aquatic photosynthetic organisms from Antarctica, but their chemical nature and function are unknown. In this study, we used the ice-binding properties of the IASs to semipurify IASs from a cyanobacterial mat, a eukaryotic green alga (Prasiola sp.), and a moss (Bryum sp.) and examined the ice recrystallization inhibition (RI) activities of the semipure materials. The semipure materials contain both protein and carbohydrate in which the carbohydrate accounted for 73, 52, and 37%, respectively, of the total carbohydrate + protein. The IASs had RI activity at concentrations of 1.4, 0.05, and 0.01 microg ml-1, respectively. RI activity was greatly reduced by heat treatment, suggesting that the IASs inhibit recrystallization through a specific interaction with ice. These results raise the possibility that the IASs increase freezing tolerance of their respective organisms by preventing the recrystallization of ice.

Antarctic Regions↗
PubMed1989

Inhibition of growth of nonbasal planes in ice by fish antifreezes.

Peptide and glycopeptide antifreezes from a variety of cold-water fishes cause ice single crystals grown from the melt to assume unusual and strikingly similar habits. The antifreezes inhibit growth on the prism faces but allow limited growth on the basal plane. As new layers are deposited on the basal plane, pyramidal surfaces develop on the outside of the crystal, and large hexagonal pits form within the basal plane. The pits are rotated 30 degrees with respect to the normal orientation of hexagonal ice crystals. Growth inhibition on the prism, pyramidal, and pit faces indicates that these faces contain sites of adsorption of the antifreeze molecules. Several properties of the antifreeze pits are consistent with (but do not prove) an origin of the pits at dislocations. The similarity of crystal habit imposed on ice by antifreezes with wide differences in composition and structure indicates a common mechanism.

Adsorption↗
PubMed1977

Adsorption inhibition as a mechanism of freezing resistance in polar fishes.

Polar fishes are known to have serum proteins and glycoproteins that protect them from freezing, by a noncolligative process. Measurements of antifreeze concentrations in ice and scanning electron micrographs of freeze-dried antifreeze solutions indicate that the antifreezes are incorporated in ice during freezing. The antifreezes also have a pronounced effect on the crystal habit of ice grown in their presence. Each of four antifreezes investigated caused ice to grow in long needles whose axes were parallel to the ice c axis. Together these results indicate the antifreezes adsorb to ice surfaces and inhibit their growth. A model in which adsorbed antifreezes raise the curvature of growth steps on the ice surface is proposed to account for the observed depression of the temperature at which freezing occurs and agrees well with experimental observations. The model is similar to one previously proposed for other cases of crystal growth inhibition.

Acclimatization↗
PubMed1976

Prediction of inspired oxygen concentration within a circle anaesthetic system.

Fresh gas flows of nitrous oxide, oxygen and halothane at 6, 3, 2 and 1 litre/min were introduced into a circle absorber system. Spontaneous respiration and IPPV were studied and a regression of inspired on delivered oxygen concentration % was calculated. The difference between delivered and inspired oxygen concentration % was increased by decreasing the fresh gas flow and by decreasiing the proportion of oxygen in that flow, especially during IPPV. Circuits designed to allow a maximum overflow of alveolar gas provided a greater inspired oxygen concentration. The patients' height and weight were related to the scatter of inspired values observed at 1 litre/min of fresh gas flow with IPPV.

Adult↗
PubMed1975

Glycoprotein and protein antifreezes in two Alaskan fishes.

Two macromolecular freezing point depressants have been isolated from the serums of two species of Alaskan fishes. A common property of the four antifreezes thus far isolated is a high alanine content which suggests that the mechanism of these antifreezes may be related to a repeating tripeptide unit.

Alanine↗
PubMed1969

The control bottle.

Explore the source record for details and available documents.

Drug Compounding↗
PubMedDate not supplied

Trimethylamine oxide and urea synthesis in rainbow smelt and some other northern fishes.

Trimethylamine oxide (TMAO) and urea levels in the blood of rainbow smelt, Osmerus mordax, were previously shown to increase dramatically in winter, but the means by which these osmolytes are acquired has remained unclear. In this study, I show that the smelt can synthesize TMAO via liver trimethylamine oxidase activity and thus are not completely dependent on a dietary source of TMAO. Cold-acclimatized Pacific herring, Clupea harengus, were also found to have high levels of TMAO in the blood, while individuals from a temperate-water population of herring did not. Herring also had liver TMA oxidase activity, which appeared to be due to a flavin-containing monooxygenase. In both species, TMA oxidase activity did not appear to be strongly affected by temperature. TMAO data were obtained for three other northern species (Macrozoarces americanus, Eleginus gracilis, and Platichthys stellatus), and these results, together with previously reported data, suggest that TMA oxidase activity is a necessary condition for high levels of TMAO in the blood. In the smelt, urea appears to be synthesized via uricolysis and also through the action of arginase on dietary arginine, while the ornithine urea cycle appears to be nonfunctional. There was no relation among several species of northern fishes between levels of urea in the blood and levels of uricase or arginase activity. Together, these results provide further evidence of the importance of TMAO and urea in some cold water fishes, demonstrate that the synthetic machinery for these osmolytes is present in the liver, and suggest that the elevated levels in response to cold may be due to conservation rather than to increased production.

Adaptation, Physiological↗