Functional aspects of ano-rectal vascularity

The blood supply of the ano-rectum has been studied in cadaveric specimens by angiographic methods. The vascular anastomosis between the middle rectal and superior rectal vessels was found to be demonstrable on one side only. There appears to be a midline paucity of vessels in both the posterior and anterior rectal walls, and this may be important in the aetiology of anastomotic dehiscence in low anterior resection.     

Differentiation of promyelocytic (HL-60) cells into mature granulocytes: mitochondrial-specific rhodamine 123 fluorescence

Rhodamine 123, a fluorescent dye which binds as a result of the transmembrane potential, was used to stain the mitochondria of HL-60 cells, a cell line established from human promelocytic leukemia cells. The DMSO-induced differentiation of promyelocytic cells into mature granulocytes caused a fourfold decrease in fluorescence intensity that paralleled the disappearance of S-phase and G2M cells. This suggests that upon myeloid differentiation whereby the cells enter an irreversible quiescent state, the mitochondrial mass of the cells has decreased. This suggestion is corroborated by electron microscopy, which shows a decrease in the number of mitochondria, and by decreases in total mitochondrial protein and cytochrome oxidase activity. The respiratory rate of isolated mitochondria did not change, suggesting that the transmembrane potential remained the same. Undifferentiated cells in exponential phase of growth exhibit an intracellular heterogeneity of fluorescence intensity. This heterogeneity appears to have a cell age basis, as late S/G2M cells, obtained by centrifugal elutriation, yielded twice the fluorescence intensity of early G1 cells.     

Free amino Acid pools and enzymes in teratonia and habituated tobaceo tissue cultures

The free amino acid content of habituated (normal) and teratoma (abnormal) tobacco tissue cultured on white's medium were compared. Significant qualitative differences (twofold or more) were observed for serine, proline, alanine, leucine, phenylalanine, and lysine. There were qualitative differences in several unidentified ninhydrin sensitive compounds. One unknown which co-chromatographed with homo-serine was present in high concentrations (9.96 μmol/g dry weight) in habituated but was lacking in teratoma tissue, Isoenzymes of an esterase, acid phosphatase, and oxidase were demonstrated in both tissues. The distinct differences in the isoenzyme pattern of acid phosphatase suggests a differential regulatory capacity of certain phosphomonoester intermediates and P(1) . The invertase activity was higher in habituated tissue, implying a greater capacity to utilize the sole carbon source, socrose.     

Bacterial oxidation of cycloparaffinic hydrocarbons

A series of 10 branched-chain alkanes and 4 cycloalkanes were employed individually as elective culture substrates for bacteria in soil. Only 2-methylbutane and 2-methylpentane yielded bacteria, one each. Both bacteria grew at the expense of eachn-alkane from C₁ to C₂₂ but they were very selective for branched-chain substrates. Compounds with less branching were most readily utilized. Neither organism grew at the expense of various cycloalkanes as sole sources of carbon and energy. The 2-methylbutane isolate was studied in detail. Resting cell suspensions were able to produce α-ketoglutaric acid from each of the compounds the bacterium was able to utilize for growth. “Non-growth hydrocarbons” were also oxidized; in each case only neutral ketonic substances were detected. A series of cycloparaffins, from C₃- to C₈-membered rings, was oxidized to the corresponding cyclomonoketones. No oxidation products of cyclododecane (C₁₂), 1,4-cyclohexadiene (C₆) or benzene could be detected. The metabolic products identified are consistent with the formation of a cyclomonoalcohol as the immediate precursor of the ketone. The alcohol is formed from cycloalkanes, the cycloalkenes, and cycloalkene oxide as substrates. Alcohol formation from the first two probably takes place by independent parallel, rather than sequential, reaction pathways. The epoxide may be a non-obligate intermediate in the cyclomonoolefin conversion to the alcohol. Significant aspects of these conversions are discussed.     

Resistance to H-2-restricted but not to allo-H2-specific graft and cytotoxic T lymphocyte responses in lymphoma mutant

The lymphoma mutant RMA-S escaped graft rejection after transplantation over a minor histocompatibility barrier, whereas it was rejected in H-2 allogeneic mice. The parental control line was rejected in both situations. The mutant, which had been selected against MHC class I molecules retained 5 to 10% of the wild-type H-2Db, Kb, and beta 2-microglobulin expression on the cell surface. It remained sensitive to allo-H-2b CTL in vitro, but was completely resistant to minor histocompatibility antigen-specific, H-2b-restricted CTL. It was equally resistant to other H-2b-restricted responses against internally derived Ag, such as tumor-specific CTL or a CTL clone specific for the influenza virus nucleoprotein. The results indicate a target cell defect that selectively abolishes the sensitivity to H-2-restricted CTL directed against internally processed Ag. This appears sufficient to shift the transplantation response over a minor histocompatibility Ag barrier from rejection to acceptance. There are two possible explanations for the results: 1) a block in the MHC class I-directed pathway for internal Ag processing, and 2) subthreshold H-2/Ag ligand density in relation to triggering requirements of restricted CTL. Regardless of the type of defect, the results demonstrate a difference between allo-H-2-specific and H-2-restricted CTL recognition at the level of the target cell.     

Metabolism of larger high density lipoproteins accumulating in some families of baboons fed a high cholesterol and high saturated fat diet

Progeny of certain baboon sires accumulate lipoproteins in high density lipoprotein-1 (HDL1) when challenged with a high cholesterol, high saturated fat diet. These studies were conducted to determine the apoprotein composition and metabolic fate of HDL1 in the plasma. HDL1 particles containing apoA-I with and without apoE were detected. The majority of particles, however, contained apoA-I without any detectable apoE. To determine the metabolic fate of HDL1 in plasma, HDL1 labeled with iodinated apoA-I from animals with high levels of HDL1 and iodinated apoA-I-labeled autologous HDL were coinjected into both high and low HDL1 animals. The data for the decay of radioactivity in HDL1 and HDL were analyzed by multicompartment modelling. The radioactivity from HDL1 was cleared from the plasma either via direct removal (9.1 +/- 4.7% in low and 21.7 +/- 8.3% in high HDL1 animals) or via its conversion to HDL. A large proportion of radioactivity from HDL1 was rapidly transferred to HDL directly or metabolized via an intermediate compartment. Most of the radioactivity from apoE-poor HDL1, however, was transferred to HDL. Both high and low HDL1 animals catabolized HDL1 and HDL similarly. Low HDL1 animals transferred HDL1 radioactivity to HDL much faster. No detectable radioactivity from HDL was transferred to HDL1. Thus, HDL1 that accumulates in high HDL1 animals is mainly a precursor for HDL. Our hypothesis is that this accumulation of HDL1 is due to the slower cholesteryl ester transfer from HDL to lower density lipoproteins, thus affecting reverse cholesterol transport in high HDL1 baboons.