The effect of tolbutamide on cerebral blood flow during hypoxia and hypercapnia in the anaesthetized rat

The increase in blood flow in the cerebral cortex of the anaesthetized rat during hypoxia and hypercapnia was investigated. Cerebral blood flow (CBF) was measured using the hydrogen clearance method with acutely implanted platinum electrodes. Hypoxia (PaO₂ 35.3±2.4 Torr) and hypercapnia (PaCO₂ 68.1±5.1 Torr) increased basal CBF from 76.3±9.0 ml/100g/min to 168.1±20.1 ml/100g/min and 162.4±31.9 ml/100g/min respectively. The sulphonylurea tolbutamide (1mM in 1%DMSO) had no significant effect on CBF in hyperoxia or in hypercapnia. However, it attenuated the increase of CBF during hypoxia by 66 ±11% (P<0.01). This suggests that opening of tolbutamide-sensitive potassium channels may be involved in the process of hypoxic vasodilation in the rat cerebral cortex.     

Lung surfactant-associated glycoproteins and proteolipids in human amniotic fluids evaluated by dot immunobinding assays

Dot immunobinding assays for the quantitation of two classes of proteins associated with lung surfactant phospholipids in human amniotic fluid are described. With the use of these assays it was determined that the two classes of surfactant proteins accumulate in the amniotic fluid at the same rate. The concentrations of disaturated phosphatidylcholine and the surfactant-associated proteins are less closely correlated. Centrifugation of amniotic fluids either before or after freezing resulted in a loss ranging from 10 to 35 percent of both surfactant disaturated phosphatidylcholine and proteins depending on the relative centrifugal force used. Preterm amniotic fluids contained significantly less of both surfactant-associated proteins, as well as disaturated phosphatidylcholine, than did term amniotic fluids which suggests that the use of these specific protein markers may enhance the assessment of fetal lung maturity.     

The pathogenesis of rat virus infection in infant and juvenile rats after oronasal inoculation

Summary The pathogenesis of rat virus (RV) infection was studied in random-bred Sprague-Dawley rats after oronasal inoculation of a recent RV isolate designated RV-Yale (RV-Y). RV-Y was pathogenic for rats inoculated as infants (2 days) whereas rats inoculated as juveniles (4 weeks) had asymptomatic infection and no lesions. Rats inoculated as infants developed pantropic infection accompanied by hepatic necrosis, granuloprival cerebellar hypoplasia and hemorrhagic encephalopathy. Virological and serological studies showed that virus could persist in inoculated rats for at least 35 days and for at least 28 days after seroconversion was first detected. Immuno-histochemical results indicated that RV-Y infects tissues conducive to virus excretion including kidney and lung. RV-Y also was found in genital tissues of some rats. Athymic juvenile rats inoculated intraperitoneally with RV-Y had a poor humoral immune response and harbored infectious virus for at least 3 weeks, whereas infection in euthymic control rats was detected for 1 week. These studies indicate that RV-Y can persists in the presence of humoral immunity and suggest that transmission of infection could occur for a substantial period after seroconversion. They also suggest that immunodeficient rats have increased susceptibility to persistent infection.     

Bacteremia caused by a recently described novel Desulfovibrio species.

An obligately anaerobic, fastidious, slowly growing, spiral, gram-negative bacterium was isolated from the blood of a 75-year-old man with acute onset of pyrexia. The patient responded rapidly to appropriate antibiotic therapy. Extensive investigation failed to detect a focus for the infection. Phenotypically, the organism was consistent with Desulfovibrio species. Microscopic investigation revealed an organism with a vibrioid or spirillioid morphology with rapidly progressive motility by means of a single polar flagellum. Biochemically, the organism produced large amounts of H2S and contained desulfovirdin. The 16S rRNA gene sequence of the organism was found to be most similar to those of members of the genus Desulfovibrio, with identical sequence homology to the newly proposed species described by Tee et al. (W. Tee, M. Dyall-Smith, W. Woods, and D. Eisen, J. Clin. Microbiol. 34:1760-1764, 1996). This is a second unrelated isolation of this novel species from two widely different locations in Australia. The two isolates show some phenotypic differences, indicating that they are different strains of the same species.     

Correction of radioresistant DNA synthesis in ataxia telangiectasia fibroblasts by prostaglandin E2 treatment.

Cultured cells from patients inheriting the rare cancer-prone and radiotherapy-sensitive disorder ataxia telangiectasia (AT) exhibit defects in the activation of cell-cycle checkpoints after exposure to ionizing radiation. In particular, the failure of AT cells to arrest transiently the DNA de novo replication machinery immediately after irradiation--so-called radioresistant DNA synthesis (RDS)--is often taken as a molecular hallmark of the disease. Recently we reported that: (i) the radiation-responsive S-phase checkpoint operating in normal human cells is mediated by a signal transduction pathway involving Ca2+/calmodulin-dependent protein kinase II (CaMKII); and (ii) the RDS phenotype of AT cells is associated with failure to mobilize Ca2+ from intracellular stores, which is required for activation of the CaMKII-dependent S-phase arrest. In the present study, we demonstrate that the RDS phenotype of AT dermal fibroblasts can be rectified in the absence of ectopic expression of functional ATM, the 350-kDa protein kinase encoded by the gene mutated in AT. Correction of RDS was observed when AT fibroblasts were coincubated with normal fibroblasts under conditions in which the 2 different cell cultures shared the same medium but were completely separated physically. The RDS trait was also rectified when AT fibroblasts were briefly incubated with prostaglandin E2 in the absence of normal feeder cells, signifying that this ubiquitous eicosanoid can serve as the diffusible "RDS-correction factor" for AT cells in the aforementioned cocultivation studies. It would therefore appear that prostaglandin E2 can assume the role of an extracellular signaling modulator of the S-phase checkpoint in AT cells exposed to ionizing radiation, inducing DNA synthesis shutdown via an alternative, ATM-independent signal transduction pathway.     

Age of diagnosis-based linkage analysis in type 1 diabetes

Genetic linkage studies of type 1 diabetes have produced a number of conflicting results, suggesting a high degree of locus heterogeneity in this disease. Approaches which model such heterogeneity will increase the power to fine map susceptibility loci. Here, using data from a genome scan of 356 affected sib pairs with type 1 diabetes, we performed heterogeneity analysis based on similarity of age at diagnosis of the sib pairs. We observed linkage to the region on chromosome 4p16.3 in sib pairs both diagnosed over the age of 10 years, whilst there was no evidence for linkage in sib pairs diagnosed before age 10 years. In contrast the sib pairs diagnosed before the age of 10 years demonstrated linkage to IDDM10, on chromosome 10p. Age of diagnosis-based heterogeneity analyses in complex diseases may be particularly helpful in mapping some susceptibility loci.     

Sex of affected sibpairs and genetic linkage to type 1 diabetes

A mouse model of diabetes shows gender dimorphism in the cumulative incidence of diabetes. Based on this, evidence for genetic linkage to IDDM13 on chromosome arm 2q was reported to be greater in type 1 diabetes families where there was a predominance of affected female offspring compared with families with a predominance of affected male offspring. Our objective was to investigate whether the sex of affected offspring affects evidence for linkage to susceptibility loci. Data from a genome scan of 356 affected sibpair families with type 1 diabetes were analysed to determine if there is differential evidence for linkage in families with affected children of a particular sex. At markers on chromosomes 3, 5, 7, 9, 11, and 19, we found a number of regions where the evidence for linkage is greater in families with affected sibpairs of a particular sex. Thus, evidence for linkage in families with affected sibpairs of the same gender suggests the presence of additional susceptibility loci. Several biological explanations are possible for these findings, including X and Y linkage, effects of sex hormones on gene expression, and quasi-linkage between sex chromosomes and autosomes.     

The autoantigenic response to rabbit cytochrome c

In this report we describe the production and characterization of autoantibody responses to rabbit cytochrome c (cyt c) in rabbits immunized with either the native monomeric or polymerized form of rabbit cyt c. Fine-specificity analyses of the response indicated that the majority of the response was to the evolutionarily conserved amino-terminal region of the molecule. The relative affinity of the autoantibody interaction with rabbit cyt c was assessed by a solid-phase assay and was found to be lower than that observed for rabbit anti-horse cyt c antibody populations. These findings are consistent with the prediction that low-affinity self-reactive B cells may escape tolerance induction.     

Analysis and gene assignment of mRNAs of a paramyxovirus, simian virus 5

Polypeptides synthesized by the paramyxovirus SV5 in infected CV-1 cells were readily identified when the host cell was treated with actinomycin D. The unglycosylated forms of HN and Fo synthesized in infected cells in the presence of tunicamycin and HN and Fo synthesized in vitro were identified by immunoprecipitation with specific antibodies. Separation of SV5-specific poly(A)-containing RNAs on methyl-mercury agarose gels and in vitro translation of fractions, indicated that the viral polypeptides were translated from individual mRNAs except P (Mr approximately 44K) and the nonstructural polypeptide V (Mr approximately 24K) for which the mRNAs could not be separated. cDNA copies of SV5-specific mRNAs were synthesized and cloned in plasmid pBR322. Clones to NP, P + V, M, F, and HN were identified by hybrid-arrest and hybrid-selection translation of SV5 mRNAs. Tryptic peptide mapping of polypeptides P and V indicated that the peptides of V were a subset of those of P. Hybridization of cDNA probes to infected cell mRNAs separated on agarose gels permitted identification of the NP, P + V, M, F, and HN mRNAs and presumptive polycistronic mRNAs. The sizes and sequence homologies of these polycistronic mRNAs were used to derive a likely gene order on the SV5 50 S genome RNA.