A comparison between histochemically demonstrable Golgi-associated and bile canalicular TDP-ase activity in liver

Summary Histochemically demonstrable Golgi-associated TDP-ase activity in liver cells from cat, chicken, rat and frog has been investigated.This activity is highly substrate-specific, insensitive to aldehyde fixation, ethanol, acetate, lead and most enzyme inhibitors. It is stimulated by divalent manganese, calcium, magnesium and cobalt and optimum pH is at pH 6 to 7.The characteristics are identical for all four species but significant differences exist at a comparison with bile canalicular activity, Golgi-associated activity in other cells and biochemical findings.This study was supported in part by a grant from the Swedish Medical Research Council.     

Sandwich Embedding of Monolayers of Cells in Epoxy Resin for Ultrathin Sectioning

In this procedure for embedding monolayers of cells, the usual glass slides are replaced by plates of resin 1-1.5 mm thick. Unlike the open-face embedding technique, the present procedure uses only a few drops of unpolymerized resin, which are applied to the fixed and dehydrated cells. During polymerization this small amount of liquid resin spreads across a relative large area, leaves the cells covered by a very thin layer, and permits phase contrast observations through it. Ultrathin sections of a particular cell encircled by a rotary scriber can be obtained by sectioning the resin slide, which has been trimmed and mounted directly in the specimen holder of the ultramicrotome.     

Mechanism of intestinal formation of deoxycholic acid from cholic acid in humans: evidence for a 3-oxo-delta 4-steroid intermediate

12 alpha-Hydroxy-3-oxo-4-cholenoic acid coupled to an adenosine nucleotide has been shown to be a metabolite of cholic acid in the intestinal anaerobic bacteria, Eubacterium species VPI 12708 (1987. J. Biol. Chem. 262: 4701-4707) and it has been suggested that this may be an intermediate in the conversion of cholic acid into deoxycholic acid. The possibility that the intestinal conversion of cholic acid into deoxycholic acid involves a 3-oxo-delta 4-steroid as an intermediate has been studied in the present work by use of [3 beta-3H]- and [5-3H]-labeled cholic acid. Whole cells as well as cell extracts of Eubacterium sp. VPI 12708 catalyzed conversion of [3 beta-3H] + [24-14C]cholic acid into deoxycholic acid with loss of about 50% of 3H label. When unlabeled chenodeoxycholic acid (20 microM) was added along with [3 beta-3] + [24-14C]cholic acid, then approximately 85% of the [3 beta-3H]-labeled was lost from deoxycholic acid. After administration of the same mixture to two healthy volunteers, deoxycholic acid could be isolated that had lost 81 and 84%, respectively, of the 3H label. Conversion of a mixture of [5-3H]- and [24-14C]labeled cholic acid by the above intestinal bacteria or cell extracts led to loss of 79-94 of the [5-3H] label.(ABSTRACT TRUNCATED AT 250 WORDS)     

Trade-off among antiherbivore defences in a south american blackberry (Rubus bogotensis)

Summary The idea of trade-offs among antiherbivore defences in plants is examined using data from a South American blackberry (Rubus bogotensis). Two distinct morphs of R. bogotensis, one with glandular trichomes and one without, were compared with respect to leaf toughness, number of prickles and prickle length. The two morphs were sympatric and grew under similar environmental conditions. The morph lacking trichomes had significantly tougher leaves and also tended to have more and longer prickles. Bioassay showed that Ithomiid larvae fed to a lesser extent on tough leaves than on more tender ones. Correlations between antiherbivore defences within each phenotype revealed three significant or almost significant negative relationships. The comparisons support the hypothesis that trade-offs exist among antiherbivore defences.     

Identification of some major cytokinins in Phaseolus vulgaris and their distribution

The determination of the various endogenous cylokinins and their distribution among organs is important in understanding their role in growth and development in the intact plant. Cytokinins in young plants of Phaseolus vulgaris were purified by immunoaffinity chromatography and HPLC, and characterised by UV spectra. Zeatin nucleotide (zeatin riboside-5'-monophosphate) and isopentenyladenine nucleotide (isopentenyladenosne-5'-monopnosphate) were the most abundant cytokinins in all organs. Their identities were confirmed by GC-MS. The levels of zeatin, zeatin riboside, isopentenyladenine and isopentenyladenosine never exceeded 5% of the nucleotides, as assessed by a methodology that preserves cytokinin nucleotides. Three extraction methods were compared with qualitatively similar results, though differing in their suppression of nucleotidase activity. Cytokinin nucleotide levels were greater in the stems and petioles than in the roots and leaves on a per gram fresh weight basis, and were greater in the stems than in the other organs on a per plant basis. Levels of the zeatin and isopentenyladenine nucleotides were about equal in the stems and leaves, but in the petioles the zeatin nucleotide levels were about twice the level of isopentenyladenine nucleotide, while in the roots they were about half the isopentenyladenine nucleotide level. The importance of considering the cytokinin form is emphasised.     

Reversal of sexual impotence in male patients with chronic obstructive pulmonary disease and hypoxemia with long term oxygen therapy

Erectile impotence is commonly encountered in male patients with respiratory failure and hypoxia. In this study, 42% of the patients experienced reversal of sexual impotence during long term oxygen therapy (LTOT). We examine the association between sexual impotence, gonadal axis hormones, hypoxia, and oxygen therapy. Nineteen sexually impotent male patients eligible for LTOT (pO₂ < 7.3 kPa during stable disease) and with sexual impotence received oxygen therapy for 1 month (n = 12) or 24 h (n = 7). pO₂, LH, FSH, testosterone, and SHBG (sex hormone binding globulin) were monitored. Five of 12 patients receiving oxygen for 1 month regained sexual potency. The responders showed a significant increase in arterial pO₂ and serum testosterone, and a decline in SHBG compared to non-responders. None of the patients receiving oxygen for 24 h experienced reversal of sexual impotence, despite a significant increase in pO₂. In these patients, serum testosterone did not increase significantly. Reversal of sexual impotence may be achieved in some patients with respiratory failure. The oxygen therapy must, however be administered for an adequate length of time.     

The size and shape of human and bovine antithrombin III.

Human and bovine antithrombin, purified by affinity chromatography on heparin-agarose, have been characterized with regard to chemical composition, size, shape and conformation. Both preparations were found to contain several active components of identical or similar size but different electrical charge. Amino acids and carbohydrate analyses revealed striking similarities between human and bovine antithrombin, while immunological analyses failed to demonstrate any cross-reactivity. The molecular weights were determined by sedimentation equilibrium to be 58 000 for human and 56 000 for bovine antithrombin. The small molecular weight difference suggested by these values was verified by several empirical methods of molecular weight estimation. Hydrodynamic measurements indicated that the two proteins have similar molecular shapes, both of which are slightly more extended that that of typical globular proteins. The internal folding of the two polypeptide chains is also similar, as evidenced by the identity of the far-ultraviolet circular dichroism spectra. Specifically, these analyses suggested a low alpha-helix content of both proteins. In conclusion, the marked structural similarity of human and bovine antithrombin indicates that the two proteins may also exhibit extensive functional similarities in the binding of heparin and the inhibition of various coagulation factors.     

Variation in the Number of Genes Coding for Salivary Amylase in the Bank Vole, CLETHRIONOMYS GLAREOLA

A Danish population of bank voles is polymorphic for three electrophoretically different salivary amylases; A, H and S, of which A is the most common. Both single-, double- and triple banded phenotypes were observed, and in several crosses two electrophoretic forms cosegregated. In addition to the qualitative variation, some individuals show consistent quantitative variation in the relative activities of their amylase bands. This variation has been qualified by spectrophotometrical measurements of the relative amounts of amylase protein in the various bands. --Seventy wild chromosomes were analyzed by determining the amounts of amylase they produced when heterozygous with a laboratory stock chromosome known to carry two closely linked amylase genes, both coding for a fourth electrophoretic variant, B. The amount of A-protein divided by half the amount of B-protein was used as an estimate of the number of A-genes on the tested chromosomes. The wild chromosomes fell into three clearly distinguishable classes: 9 clustered around a gene number estimate of one, 45 chromosomes yielded estimates around two genes, and the gene number estimate of the remaining 16 was close to three. The integer values of the gene number estimates and the cosegregation of electrophoretically different salivary amylases are consistent with the model that the population is polymorphic for chromosomes with either one, two, or three closely linked amylase genes. It is suggested that such gene number variation may be more common than generally recognized, and some other reported cases of quantitative enzyme variation, for instance that of human red cell acid phosphatase, are interpreted in terms of variation in the number of genes involved.     

Classification of basiphilous pine forests in Telemark, SE Norway: a numerical approach

The basiphilous pine forests in southern Telemark, SE Norway, have previously been classified according to the ordinary phytosociological methods of the Braun—Blanquet system. The same material was later treated by numerical analysis, i.e., TABORD—classification and the ordination technique 'reciprocal averaging'. No significant differences were found between the numerical and the non—numerical classification except for the classification of some transitional communities. Ordination by 'reciprocal averaging' gave a useful complement to the TABORD classification, and re—leves and species were distributed along interpretable gradients (i.e., along a dry—wet gradient and along a gradient from forest—rim conditions to forest conditions).     

Isolation and characterization of cells from rat adipose tissue developing into adipocytes.

To identify cells developing into adipocytes by accumulation of triglyceride, rat epididymal fat pad cells from small rats were exposed to (3)H-labeled chylomicron fatty acids in vivo and then liberated with collagenase. Tissue remnants were removed by filtration and mature fat cells by flotation. Aggregating cells were then removed by filtration through a 25- micro m nylon screen. Further purification of cells labeled in vivo was obtained by removing floating cells from those adhering to the bottom of a culture dish. The adhering cells multiplied to a confluent monolayer when cultured in Medium 199 containing serum, glucose, insulin, and a triglyceride emulsion. The cells then gradually enlarged due to granulation of the cytoplasm by a lipid-staining material. After about 2 weeks these granules had coalesced forming mature adipocytes of typical signet-ring appearance. Free adipocytes could then be recovered from the cultures by collagenase treatment. After about 2 weeks of culture these cells had the same size (about 30 micro m) as adipocytes recovered in the original collagenase preparation of the rat epididymal fat pad. They contained triglyceride lipase activity and incorporated glucose into triglycerides to the same extent as cells developed in vivo but had higher lipoprotein lipase activity. In vitro, heparin in a low concentration, prostaglandin E(1), isobutylmethylxanthine, and cholera toxin markedly promoted the development of these cells into adipocytes. This could be shown to occur almost completely indicating that this fraction of cells was homogeneous and consisted of cells with the capacity to form adipocytes. The duplication time was about 2 days and did not change with subculturing. Preadipocytes could be obtained by density gradient centrifugation, isolating triglyceride-containing cells either directly from the pad or after 3 days in culture. All of these cells developed into adipocytes as described above but did not multiply as readily. It was concluded that cells from the epididymal fat pad from small rats can be isolated in a homogenous fraction that develops in culture into cells of identical morphology and function as adipocytes formed in vivo. The differentiation of these cells into adipocytes may be manipulated in vitro.