Hydrogen production by immobilized cells in the nozzle loop bioreactor

Summary The continuous production of hydrogen in a Nozzle Loop Bioreactor was investigated using immobilized Rhodospirillum rubum KS-301 with glucose as the growth-limiting substrate. The maximum hydrogen production rate in the experimental range was 91mL/h at dilution rate 0.4h^-1, initial glucose concentration 5.4g/L, and circulation rate 70h^-1 .     

Sequence and evolution of cattle MHC class I cDNAs: concerted evolution has not taken place in cattle

To explore genetic mechanisms responsible for major histocompatibility complex (MHC) class I evolution in the artiodactyls, we cloned and sequenced MHC class I cDNAs from a Bos taurus bull heterozygous for cattle MHC (BoLA) class I serological specificities w2 and w30. Four unique cDNAs were found, indicating the presence of at least two MHC class I loci. Analysis of these four cDNAs and all previously published BoLA cDNA sequences suggested that there may be three cattle MHC class I loci. Additionally, comparison of all of the BoLA class I cDNAs to MHC class I cDNAs of other artiodactyls showed that some of the BoLA class I cDNAs were more similar to certain sheep cDNAs than they were to other cattle cDNAs. These data indicate that each BoLA class I locus has evolved independently after an ancestral gene duplication event and that inter-locus segmental exchange o or concerted evolution has not occurred rapidly enough to cause extensive divergence between the orthologous MHC class I loci of sheep and cattle.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers L02832–L02835. Correspondence to: T. L. Garber at the present address.     

Isolation and characterization of a putative multidrug resistance pump from Vibrio cholerae

Multidrug-resistant strains of Vibrio cholerae (the causative agent of the diarrhoeal disease cholera) have recently been described. In an attempt to identify a homologue of the Escherichia coli TolC in V . cholerae , we isolated a DNA fragment (pVC) that enabled an E . coli tolC mutant to grow in the presence of 0.05% deoxycholate (DOC). However, other TolC defects were not complemented. Nucleotide sequence analysis of this fragment revealed the presence of two open reading frames (ORF1 and ORF2) separated by 9 bp and encoding 42.4 and 55.8 kDa proteins respectively. The translational products of these two ORFs correlated closely with the molecular weights of the predicted proteins. The deduced amino acid sequences of ORF1 and ORF2 showed a high degree of similarity with conserved regions of the E . coli efflux pump proteins, EmrA and EmrB. The presence of pVC2 within the E . coli efflux pump mutants defective in either the emrAB or the acrAB genes provided the mutants with resistance against several antibiotics. A V . cholerae isogenic mutant defective in ORF2 was constructed by gene replacement. Characterization of this mutant has shown it to be more sensitive to CCCP, PMA, PCP, nalidixic acid and DOC than the parent strain. These results suggest that ORF1 and ORF2 constitute an operon encoding two components of a putative multidrug resistance pump in V . cholerae . In addition, the presence of both structural and functional similarities between VceAB and EmrAB suggests that VceAB is a homologue of EmrAB.     

Mosquito circadian and circa-bi-dian flight rhythms: a two-oscillator model

Summary Circadian rhythmicity was found in the flight activity ofCuliseta incidens recorded in constant darkness for up to 14 weeks. The first nonhuman circa-bi-dian (about-two-day) rhythms were also found (Figs. 6–7). Circadian periods were either stable, remaining <24h (Fig. 1), or labile, with a change from <24h to >24 h (Fig. 2). Inactivity phenomena (day-skipping) were common in the latter group only (Fig. 5). The period at activity onset was much more labile than the period at offset (Fig. 4). The activity patterns of some period-lengthened animals suggested control by two oscillators which could temporarily or permanently uncouple (Figs. 8–9).A pacemaker model consisting of a labile evening (E) oscillator mutually coupled to a stable morning (M) oscillator is the most economical proposal which can account for these results. The view that E and M uncouple and run with different periods can account for many records in which the period was labile. Circa-bi-dian rhythms can be explained by the period of E lengthening to where it synchronizes with M in a 21 mode. Thus, E and M are proposed to behave similarly to the human activity and temperature oscillators. It is speculated that day-skipping might indicate that E oscillates between circadian and circa-bi-dian ranges without overt activity being expressed.Abbreviations LD1212 alternating 12h light, 12h dark - DD constant dark - LL constant light - period of rhythm - _on period at activity onset - _off period at activity offset - activity time - mean activity time     

Dopamine depletion in nucleus accumbens reduces ACTH1–24-induced excessive grooming

Animals were pretreated with 6-OHDA or ascorbate vehicle injected into the nucleus accumbens and tested 10 days later for excessive grooming induced by intracerebroventricular injection of ACTH_1–24. The animals pretreated with 6-OHDA showed a significant decrease in excessive grooming produced by the neuropeptide and this reduction was seen only in the last 30 minutes of a 60-min test session. The results suggest an interaction of ACTH with dopamine systems on the onset and maintenance of excessive grooming.     

Differential Effects of Fluoronorepinephrines on Phosphatidylinositol Turnover in Rat Pinealocytes

(+/-)-Norepinephrines (NAs), substituted with fluorine at positions 2, 5, and 6 of the ring, were compared with the unsubstituted compound with respect to their capacity for eliciting increased incorporation of [32P]orthophosphate into phosphatidylinositol of pinealocytes. 5F-NA and 6F-NA were approximately equipotent with NA, whereas 2F-NA required a higher concentration and gave lower maximum stimulation. Inhibition of these effects by prazosin confirmed the participation of alpha 1-adrenergic receptors. The results are comparable with those reported for alpha 1-adrenergic receptor-mediated events in other systems and different from the beta-adrenergic receptor-mediated elevation of cyclic AMP in pinealocytes. These and earlier results emphasize the importance of the hydroxyl group at position 3 of the ring and at the beta-position of the side chain in catecholamine activation of the pineal alpha-adrenergic receptors, which are involved in alterations of phospholipid metabolism.     

Labeling of the centromeric region on human chromosome 8 by in situ hybridization

Summary Probe DNA that binds preferentially to the centromeric region of human chromosomes 8 was synthesized. Alpha satellite probe DNA molecules were selectively amplified from sorter-purified human chromosomes 8 by in vitro DNA amplification using the polymerase chain reaction (PCR). Probe labeling was performed during PCR by incorporation of biotinylated deoxyuridine. In situ hybridization of unpurified probe DNA comprised of alpha satellite monomer and higher molecular weight DNA fragments with metaphase chromosome spreads showed binding to the centromeric regions of numerous chromosomes. However, blocking with unlabeled total human alphoid DNA dramatically reduced crosshybridization to chromosomes other than 8. Under these conditions, the degenerate probe DNA allowed unambiguous visualization of domains occupied by centromeric DNA of chromosome 8 in metaphase spreads and interphase cell nuclei, thus greatly facilitating the detection of numerical chromosome aberrations in tumor cells. In situ hybridization of size-fractionated alpha satellite DNA identified the monomeric fraction as the major cause of crosshybridization. Alpha satellite dimers and higher molecular weight DNA fragments showed relatively high specificity for human chromosomes 8.     

Sister chromatid exchange (SCE) frequencies differ between directly prepared cytotrophoblasts and cultured mesenchymal core cells

Summary Analysis of sister chromatid exchange (SCE) in chorionic villus cells may become useful in measuring the response of fetal tissues to clastogens or mutagens or for prenatal diagnosis of chromosome breakage syndromes such as Bloom syndrome. Previous studies have failed to analyze cytotrophoblastic cells and mesenchymal core cells, or have found no difference between SCE frequencies in directly prepared and cultured cells. Our data indicate significant differences in SCE frequencies between the two cell types: SCE frequency in directly prepared cytotrophoblasts was 6.73 SCE/cell ± 1.6, whereas SCE frequency in cultured mesenchymal core cells was 10.31 SCE/cell ± 0.49 (P < 0.001). SCE analyses involving chorionic villi must take into account cell type.Presented at the 41st Meeting of the American Society of Human Genetics, Cincinnati, Ohio     

Polymers of Cu/Zn Superoxide Dismutase Produced by Cross-Linking with Glutaraldehyde

Soluble polymers of bovine Cu/Zn superoxide dismutase (EC 1.15.1.1) have been prepared using the homobifunctional cross-linking reagent, glutaraldehyde. A form of the enzyme, a tetramer. with a molecular weight of 64, 000 has been purified by gel filtration. The functional properties of the tctrarner have been investigated. Reconstitution with copper and zinc was required for full activity. After metal reconstitution, the specific activity of the tetramer was shown to be close to 90% that of the native dimerism enzyme.

The serum half-life of the tetramer in rats was found to be increased by a factor of six when compared with native superoxide dismutase. The tissue distribution of the two forms was also found to be direrent with the tetrarner accumulating predominantly in the liver.