Varied and repeated atropine dosages and exercise-heat stress

Comparisons of physiological responses to 0, 0.5, 1, and 2 mg atropine (IM) were made in seven males (X +/- SD: age, 24 +/- 3 years; ht, 174 +/- 12 cm; wt, 76 +/- 3 kg) while they exercised (approximately 390 W) in a hot-dry (40 degrees C, 20% rh) environment. Responses to 4 mg, as well as repeatability of responses to 2 mg, were studied in two and six of these subjects, respectively. On 8 test days an intramuscular injection of atropine or saline control was administered 20 min before subjects walked on a treadmill for two 50-min bouts. Heart rate (HR) during exercise did not change in the control trial but by min 50 increased during all atropine trials (P less than 0.01). Rectal temperature (Tre) increased (P less than 0.01) in all trials by min 50 and continued increasing (P less than 0.01) in the 2-mg trial during the second exercise bout. For the two subjects tested with all dosages (0.5 - 4 mg atropine), the change in HR and Tre between the atropine and control trials at 50 min of exercise was regressed against the various atropine dosages. The relationship (r = 0.92) for HR was curvilinear while the relationship (r = 0.99) for Tre was linear. Mean weighted skin temperature (Tsk) was relatively constant during exercise and was warmer (P less than 0.05) with increasing atropine dosage. In a repeat 2 mg trial, HR was 6 bt . min-1 lower (P less than 0.05) on the second exposure but Tre was the same (P greater than 0.05) on both days. For subjects walking in the heat, three new observations were: 1) 0.5 mg of atropine resulted in increased HR and Tsk compared to control values; 2) HR was elevated but the magnitude of change decreased with increasing dosage, while the elevation in Tre was consistent with increasing dosage; and 3) rectal temperatures (in trials with and without atropine) were unaffected by previous days of atropine administration.     

Effect of Increased Glucose Levels on Na+/K+-Pump Activity in Cultured Neuroblastoma Cells

Neuroblastoma cells were used to analyze the effect of elevated glucose levels on myo-inositol metabolism and Na+/K+-pump activity. The activity of the Na+/K+ pump in neuroblastoma cells is almost totally sensitive to ouabain inhibition. Culturing neuroblastoma cells in 30 mM glucose caused a significant decrease in Na+/K+-pump activity, myo-inositol metabolism, and myo-inositol content, compared to cells grown in the presence of 30 mM fructose. Glucose supplementation also caused a large intracellular accumulation of sorbitol. The aldose reductase inhibitor sorbinil prevented the abnormalities in myo-inositol metabolism and partially restored Na+/K+-pump activity in neuroblastoma cells cultured in the presence of elevated glucose levels. These results suggest that the accumulation of sorbitol by neuroblastoma cells exposed to elevated concentrations of extracellular glucose causes a decrease in myo-inositol metabolism and these abnormalities are associated with a reduction in Na+/K+-pump activity.     

Acrosomal enzymes of human spermatozoa before and after in vitro capacitation

The effect of in vitro capacitation (events that occur before the acrosome reaction) on the acrosomal enzymes of human spermatozoa was determined. Capacitation of human spermatozoa was assessed by their ability to penetrate denuded hamster oocytes. The activities of a number of enzymes commonly associated with the sperm acrosome, including nonzymogen acrosin, proacrosin, inhibitor-bound acrosin, hyaluronidase, acid phosphatase, beta-glucuronidase, beta-glucosidase, beta-N-acetylglucosaminidase, beta-galactosidase and beta-N-acetylgalactosaminidase were assessed. With the exception of acid phosphatase, no alteration in enzyme activity occurred after 4 h of incubating the spermatozoa under capacitation conditions although gamete fusion took place. The acid phosphatase levels decreased twofold, presumably due to the loss of seminal (prostatic acid phosphatase that loosely adheres to spermatozoa. After 8 h of capacitation, a large decrease in sperm enzyme levels took place only in the case of hyaluronidase, although small decreases were also noted in total acrosin, proacrosin and inhibited acrosin. No new electrophoretically migrating forms of acrosin were observed. Decreases in total acrosin and proacrosin, but not in inhibited acrosin, also occurred when spermatozoa were incubated under noncapacitating conditions for 8 h, indicating that capacitation may specifically cause the release of some acrosin inhibitor from human spermatozoa. It is concluded that, with the possible exception of hyaluronidase, the in vitro capacitation of human spermatozoa does not cause a major change in its acrosomal enzyme content so that these hydrolases are fully present before the acrosome reaction takes place during gamete fusion. Serum albumin appears to protect against the loss of some of these enzymes since the activity of several glycosidases was significantly reduced when the spermatozoa were incubated for 8 h in human serum albumin-free medium.     

Aspartate and asparagine tRNA genes in wheat mitochondrial DNA: a cautionary note on the isolation of tRNA genes from plants.

We have identified genes encoding a "native" tRNA(Asp) (trnD-GTC) and a "chloroplast-like" tRNA(Asn) (trnN-GTT) on opposite strands and 633 bp apart within a sequenced 1640 bp RsaI restriction fragment of wheat mtDNA. The trnD gene has been found previously at a different location in wheat mtDNA (P.B.M. Joyce et al. (1988) Piant Mol. Biol. 11, 833-843); the duplicate copies of this gene are identical within the coding and immediate flanking regions (9 bp downstream and at least 68 bp upstream), after which obvious sequence similarity abruptly disappears. The trnN gene is identical to its homolog in maize ctDNA; continuation of sequence similarity beyond the coding region suggests that this gene originated as promiscuous ctDNA that is now part of the wheat mitochondrial genome. In the course of this work, we have encountered some unexpected similarities between tRNA gene regions from wheat mitochondria and other sources. Detailed analysis of these similarities leads us to suggest that trnN genes reportedly from petunia nuclear DNA (N. Bawnik et al. (1983) Nucleic Acids Res. 11, 1117-1122) and lupine mtDNA (B. Karpińska and H. Augustyniak (1988) Nucleic Acids Res. 16, 6239) are, in fact, from petunia mtDNA and lupine ctDNA, respectively, whereas a putative wheat nuclear tRNA(Ser) (trnS-TGA) gene (Z. Szwekowska-Kulińska et al. (1989) Gene 77, 163-167) is actually from wheat mtDNA. In these instances, it seems probable that the DNA samples used for cloning contained trace amounts of DNA from another sub-cellular compartment, leading to the inadvertent selection of spurious clones.     

Elevated uridine nucleotide pools in fluorouracil/fluorouridine resistant mutants ofNocardia lactamdurans

Summary Selection of spontaneous mutants ofNocardia lactamdurans MA2908 for resistance to 5-fluorouracil results in the simultaneous development of resistance to 5-fluorouridine. The resulting mutants fall into four distinct classes based on the amount of uracil accumulating in fermentation broths. An additional characteristic of these mutants is a reduction in the ability to incorporate exogenous uracil into nucleic acids even though transport and conversion to the nucleotide level appears normal. Finally, production of efrotomycin is increased in these mutants in both chemically defined and complex fermentation media to levels equivalent to those of MA4820, the first productivity mutant isolated in a conventional strain improvement program. Resistance development and uracil excretion are adequately explained by an elevation of the intracellular uridine nucleotide pool, in particular UMP. The role of the uridine necleotides in the efrotomycin fermentation is unknown.     

Presence of chromosomal mosaicism in abnormal preimplantation embryos detected by fluorescence in situ hybridisation

The extent of chromosomal mosaicism in human preimplantation embryos was examined using an improved procedure for the preparation and spreading of interphase nuclei for use in fluorescence in situ hybridisation, allowing the analysis of every nucleus within an embryo. One cell showed no hybridisation signals in only three of the 38 embryos that were included in this study, i.e. the hybridisation efficiency per successfully spread nucleus was 99% (197/200). Double-target in situ hybridisation analyses with X- and Y-chromosome-specific probes was performed to analyse nine embryos resulting from normal fertilisation, 22 polypronucleate embryos and seven cleavage-stage embryos where no (apronucleate) or only one pronucleus (monopronucleate) was observed. We also analysed autosomes 1 and 7 by double-target in situ hybridisation in the nuclei of two apronucleate, one monopronucleate and four polypronucleate embryos. All nine embryos that resulted from normal fertilisation were uniformly XY or XX. None of the apronucleate or monopronucleate embryos was haploid: three were diploid, one was triploid and three were mosaic. Fertilisation was detected by the presence of a Y-specific signal in four of these embryos. Of the polypronucleate embryos, two were diploid, two were triploid and 18 were mosaic for the sex chromosomes and/or autosomes 1 and 7. These results demonstrate that fertilisation sometimes occurs in monopronucleate embryos and that chromosomal mosaicism can be detected with high efficiency in apronucleate, monopronucleate and polypronucleate human embryos using fluorescence in situ hybridisation.     

Gastric colonization withCandida albicans

This is the first report on the isolation ofCryptococcus neoformans from pigeon droppings in China and their serotypes.C. neoformans colonies which produced brown colonies on caffeic acid-cornmeal agar were found in Twenty-five out of thirty-six samples of pigeon droppings. Fifty-one colonies randomly picked from the positive samples were identified asC. neoformans by a commercially available kit for carbon source assimilation test and Christensen's urea agar. Forty (78%) out of the 51 strains were serotyped as A and 11 (22%) as AD. At the same time, seventeen out of nineteen clinical isolates were serotyped as A and 2 as B. There are three findings in our results. One is that onlyC. neoformans var.neoformans strains could be isolated from pigeon droppings, although the varietygattii strains were found in the clinical isolates obtained in the same geographic site in China. The second is that serotype A strains were most frequently seen in natural and clinical materials in the southeast part of China, and serotype AD strains were isolated in pigeon droppings but not in clinical materials. The third is that the coexistence of serotype A and AD cells ofC. neoformans strains in same samples of pigeon droppings were observed.     

Climbing Darwin's ladder

The work of Bartel and Szostak, in which RNA molecules were selected to enhance the ability to catalyze a reaction similar to a step in protein-catalyzed RNA replication, is discussed. An important aspect of this experiment was the ability to reach a high level of functional organization in ten evolutionary steps. Further steps necessary to obtain an RNA enzyme with RNA replicase activity include performing the reaction with mononucleoside 5'-triphosphates, generalizing the reaction to include a variety of sequences without loss of template-dependent specificity, and overcoming template self-structure that could prevent some regions from being copied efficiently.