Infinite-cis kinetics support the carrier model for erythrocyte glucose transport

It has been claimed that the Km for infinite-cis uptake of glucose in human erythrocytes is so low that the carrier model for transport must be rejected. We redetermined this parameter for three experimental conditions and found instead that the Km values were in good agreement with the model. For each of a variety of cis glucose concentrations, cells were preequilibrated with various concentrations of glucose, and the apparent Km was determined as the intracellular concentration reducing the initial rate of net uptake by half. The dependence of the apparent Km values on the cis glucose was as predicted by the carrier model; the infinite-cis Km was determined from both this concentration dependence and the extrapolated value at infinite cis glucose. The resulting values were 15 mM for fresh blood at 0 degrees C, 39 mM for outdated blood at 0 degrees C, and 11 mM for outdated blood at 25 degrees C. Previous measurements of the Km at room temperature yielded values of 2-3 mM. These earlier studies used a time course procedure that indicated rapid changes in rates during the initial 10 s of uptake but did not directly measure such changes. We examined the uptake of 60 mM glucose at 20 degrees C into cells containing 0 and 5 mM glucose; rapid changes in rates were not observed in the first few seconds, and the time courses were more consistent with our higher Km values. Our new values, together with other initial rate measurements in the literature, support the adequacy of the carrier model to account for the kinetics of glucose transport in human erythrocytes.     

TRACE METALS IN GIANT KELP,MACROCYSTIS

Concentrations of 38 elements present in Macrocystis tissues are listed. Mean concentrations of Cu, Zn, Fe, and Mn were similar for samples of juvenile and adult sporophytes from field sites. Cu in Macrocystis tissues rose above background levels when concentrations of 0.05 to 0.1 μm were added to the culturing medium. Above-normal accumulation for Zn occurred at 0.1 μm and for Fe at 10 μm . Tissue Mn appeared independent of the ambient Mn concentration over the ranges studied. Computations indicated that upwelling is important for N and P renewal to Macrocystis beds but may be less significant for import of trace metals.     

Immunocytochemical and enzyme histochemical localization of kallikrein-like enzymes in colon, intestine, and stomach of rat and cat

Kallikrein was localized in goblet (or mucous) cells of rat colon and in rat and cat small intestine and stomach by two immunocytochemical techniques. A kallikrein-like enzyme was also localized by enzyme histochemistry in mast cells of colon, intestine, and stomach of the cat, where they appeared to be associated with blood vessels in the lamina propria. The mast cell enzyme, however, was not detected by immunocytochemistry using antibodies to kallikrein. Modification in the enzyme histochemical procedure (pH, fixation) yielded positive results for a kallikrein-like protease in goblet cells of the intestine and colon. The possible physiological and pathological significance of kallikrein-like enzyme in the gastrointestinal tract and elsewhere is discussed.     

Quantitative Description of Cell Cycle Kinetics Under Chemotherapy Utilizing Flow Cytometry

A discrete time cell cycle kinetics model is developed to account for the effects of cytotoxic chemotherapy, particularly including the existence of cells destined to die. A model structure is determined from related experiments, leaving key parameter values undetermined. These values are found by determining the best least squares fit of the predicted to the observed DNA distribution data at a series of time intervals. the numerical methods include separable least squares, linear inequality constrained least squares and the Gauss-Newton method. This approach is applied to an experiment in which the Ehrlich ascites tumour was given a single dose of bleomycin. the results include several different parameters, including the age response function and a time series of cell age and DNA distributions, which can be used as a basis for further treatment.     

Management of female breast disease by Southampton general practitioners.

One hundred and two Southampton general practitioners were interviewed about female breast disease. There was agreement about clinical management and the need to both teach and promote breast self-examination. The general practitioners, however, were divided as to whether any breast screening facilities were needed in Southampton. Records kept by the general practitioners of women seen with breast symptoms showed that one-quarter of all new episodes were referred to hospital at the first visit. That the general practitioners considered early diagnosis to be important was made evident from a number of the results. This attitude is encouraging in view of the evidence showing that long-term survival may be greater when delays are shorter.     

Pyrimidine scavenging by Mycobacterium leprae

Mycobacterium leprae incorporated exogenously supplied pyrimidines as bases or nucleosides, but not as a nucleotide, into its nucleic acids. Notably, thymine was incorporated approximately 5 times more rapidly than thymidine by both suspensions of, or intracellular M. leprae. Thymine incorporation was significantly inhibited by clofazamine and dapsone at near-pharmacological levels. Therefore, incorporation of thymine is preferable as an activity for assessing viability of M. leprae. Nucleosides were converted to nucleotides through kinases, bases through phosphoribosyltransferases. Alternatively, thymine and uracil could first be converted to nucleosides. Cytosine and uracil bases were interconvertible, and uracil alone could supply all the pyrimidine requirements of M. leprae, though conversion to the thymine base was extremely slow. Overall, pyrimidine scavenging occurs at a slower rate than, and appears not to be so important as purine scavenging in M. leprae.     

Seasonal, genetic and age variation in non-esterified fatty acid concentrations in the ewe

Plasma samples were collected at intervals of about 2 weeks from about ten 2 1/2 year old, or older, and five 1 1/2 year old ewes of each of the Scottish Blackface, Finnish Landrace and Tasmanian Merino ewes and were assayed for their non-esterified fatty acid (NEFA) concentrations. The NEFA concentrations showed an increase with time for every animal. The NEFA concentrations and their linear increase was least in the Finnish Landrace animals. The increase with time was greatest in the Merinos. There was no difference between the age groups. There was no evidence of any annual, cyclical trend.