The acute effects of cigarette smoke exposure on experimental skin flaps

Random vascular patterned caudally based McFarlane-type skin flaps were elevated in groups of Fischer 344 rats. Groups of rats were then acutely exposed on an intermittent basis to smoke generated from well-characterized research filter cigarettes. Previously developed smoke inhalation exposure protocols were employed using a Maddox-ORNL inhalation exposure system. Rats that continued smoke exposure following surgery showed a significantly greater mean percent area of flap necrosis compared with sham-exposed groups or control groups not exposed. The possible pathogenesis of this observation as well as considerations and correlations with chronic human smokers are discussed. Increased risks of flap necrosis by smoking in the perioperative period are suggested by this study.     

Hypoxia-induced changes in shivering and body temperature

Experiments were carried out on conscious cats to evaluate the general characteristics and modes of action of hypoxia on thermoregulation during cold stress. Intact and carotid-denervated (CD) conscious cats were exposed to ambient hypoxia (low inspired O2 fraction) or CO hypoxia in prevailing laboratory (23-25 degrees C) or cold (5-8 degrees C) environments. In the cold, both groups promptly decreased shivering and body temperature when exposed to either type of hypoxia. Small increases in CO2 concentration reinstituted shivering in both groups. At the same inspired concentration of O2, CD animals decreased shivering and body temperature more than intact cats. While this difference resulted, in part, from a lower alveolar PO2 in CD cats, a difference between intact and CD cats was apparent when the two groups were compared at the same alveolar PO2. During more prolonged hypoxia (45 min), shivering returned but did not reach normoxic levels, and body temperature tended to stabilize at a hypothermic value. Exposure to various levels of hypoxia produced graded suppression of shivering, with the result that the change in body temperature varied directly with inspired O2 concentration. Hypoxia appears to act on the central nervous system to suppress shivering and sinus nerve afferents appear to counteract this direct effect of hypoxia. In intact cats, this counteraction appears to be sufficient to maintain body temperature under hypoxic conditions at room temperature but not in the cold.     

Expression of creatine kinase isoenzyme during oogenesis and embryogenesis in the mouse

Creatine kinase activity was discovered in the growing mouse oocyte and in the preimplantation embryo. Changes in the enzyme activity during the growth and maturation of the egg and during the development of the embryo up to the blastocyst stage were determined. Close similarity of the protein to the brain-type isoenzyme of creatine kinase was established immunochemically. The kinetic parameters of the brain-type isoenzyme (M. R. Iyengar, C. E. Fluellen, and C. W. L. Iyengar, 1982, J. Muscle Cell Motil. 3, 231–246) and the pattern of development-associated changes in activity suggest a possible role for creatine kinase in maintaining the reported high ATP/ADP ratio (L. Ginsberg and N. Hillman, 1975, J. Reprod. Fertil. 43, 83–90), which is essential for the biosynthetic activities of the embryo.     

Differential Dialysis Culture for Separation and Concentration of a Macromolecular Product

A differential dialysis flask, constructed with three chambers and two membranes of different porosity, was used to effect the separation and concentration of enterotoxin B produced extracellularly by a culture of Staphylococcus aureus. Variables were examined that affected the diffusion of glucose, as measured by half-equilibration time and permeability coefficient; the relative chamber volume, type of membrane, membrane masking, and mixing all exerted a substantial influence on diffusion rates. A number of membrane filters were tested for usefulness; one type, made with vinylidene fluoride, had desirable physical and diffusional properties, but neither it nor others consistently withheld the bacteria for more than a marginally useful period of about 50 hr. In ordinary two-chambered dialysis culture, the amount of enterotoxin reached 10 times that in control culture; in differential, three-chambered dialysis culture the comparable factor of increase was about 7, with about two-thirds of this amount being separated from cells in the product chamber of the flask.     

Cation Transport in Escherichia coli : VII. Potassium requirement for phosphate uptake

When Escherichia coli K-12 is grown in media containing limiting amounts of K, growth continues normally until all the extracellular K has been consumed. Thereafter the rates of growth, glucose consumption, and oxygen consumption decrease progressively, and the cell contents of K and P fall. These changes, referred to as K limitation, are all reversed by the addition of K. By specifically altering the ionic composition of the cells it was shown that these metabolic disturbances are not due to changes in the cell content of K or Na, but are directly related to the absence of K from the extracellular medium. The cell pool of inorganic P and the uptake of PO₄ from the medium are low in K-limited cells and are immediately stimulated by the addition of K, suggesting that the primary effect of K limitation is to inhibit PO₄ uptake. All the metabolic effects of K limitation can be attributed to inhibition of PO₄ uptake. The requirement of extracellular K for PO₄ uptake may be due to a coupling between the uptake of K and PO₄.     

Ion Transport in Isolated Rabbit Ileum : III. Chloride fluxes

Unidirectional Cl fluxes across in vitro segments of rabbit ileum have been determined both in the absence and in the presence of an electrochemical potential gradient. The results indicate that Cl transport in this preparation can be attributed to purely passive forces uninfluenced by solvent drag or exchange diffusion. Furthermore, on the basis of this and previous studies, it has been demonstrated that the sum of the partial ionic conductances of Na and Cl accounts for at least 90 per cent of the total tissue conductance.     

Kinetic relations of the Na-amino acid interaction at the mucosal border of intestine

The relation between unidirectional influxes of Na and amino acids across the mucosal border of rabbit ileum was studied under a variety of conditions. At constant Na concentration in the mucosal bathing solution, amino acid influx followed Michaelis-Menten kinetics permitting determination of maximal influx and the apparent Michaelis constant, K_t. Reduction in Na concentration, using choline as substitute cation, caused an increase in K_t for alanine but had no effect on maximal alanine influx. The reciprocal of K_t was a linear function of Na concentration. Similar results were obtained for valine and leucine and these amino acids competitively inhibited alanine influx both in the presence and in the absence of Na. These results lead to a model for the transport system which involves combination of Na and amino acid with a single carrier or site leading to penetration of both solutes. The model predicts that alanine should cause an increase in Na influx and the ratio of this extra Na flux to alanine flux should vary with Na concentration. The observed relation agreed closely with predicted values for Na concentrations from 5 to 140 mM. These results support the hypothesis that interactions between Na and amino acid transport depend in part on a common entry mechanism at the mucosal border of the intestine.