A molecular genetic linkage map of mouse chromosome 18 reveals extensive linkage conservation with human chromosomes 5 and 18

An interspecific backcross between C57BL/6J and Mus spretus was used to generate a molecular genetic linkage map of mouse chromosome 18 that includes 23 molecular markers and spans approximately 86% of the estimated length of the chromosome. The Apc, Camk2a, D18Fcr1, D18Fcr2, D18Leh1, D18Leh2, Dcc, Emb-rs3, Fgfa, Fim-2/Csfmr, Gnal, Grl-1, Grp, Hk-1rs1, Ii, Kns, Lmnb, Mbp, Mcc, Mtv-38, Palb, Pdgfrb, and Tpl-2 genes were mapped relative to each other in one interspecific backcross. A second interspecific backcross and a centromere-specific DNA satellite probe were used to determine the distance of the most proximal chromosome 18 marker to the centromere. The interspecific map extends the known regions of linkage homology between mouse chromosome 18 and human chromosomes 5 and 18 and identifies a new homology segment with human chromosome 10p. It also provides molecular access to many regions of mouse chromosome 18 for the first time.     

Significance of the delta 5 and delta 4 steroidogenic pathways in the hamster preovulatory follicle

Isolated hamster granulosa cells and theca from preovulatory follicles were incubated in vitro for 2 and 6 h in the absence/or presence of LH and steroid substrates. The purpose of the experiments was to determine, in theca, the relative activities of the delta 5 and delta 4 pathways under controlled conditions, and to compare the ability of granulosa cells and theca to form progesterone from exogenous pregnenolone. The results of the experiments show that the delta 5 pathway in theca predominates before and up to 2 h after LH stimulation. The delayed effect of LH after 2 h is a switch from delta 5 to delta 4 as the major metabolic pathway. Progesterone formation from exogenous pregnenolone is 7 to 10 times greater in unstimulated granulosa cells than in theca. Acute effects of LH lead to increased conversion of exogenous pregnenolone to progesterone in granulosa cells but not theca. LH does, however, acutely stimulate the thecal conversion of DHEA to androstenedione. The longer term effect of LH in both cell types is to increase pregnenolone conversion to progesterone.     

Structure of a Moloney murine leukemia virus-virus-like 30 recombinant: implications for transduction of the c-Ha-ras proto-oncogene.

Tumor progression locus 2 (Tpl-2) encodes a novel serine-threonine protein kinase which is activated by provirus integration in the late stages of oncogenesis in Moloney leukemia virus (MoMuLV) induced rat T-cell lymphomas. In this report, we present evidence that the provirus integrated in the Tpl-2 locus in 1 of 10 T-cell lymphomas harboring a Tpl-2 rearrangement (2779) is a recombinant between MoMuLV and virus-like 30 (VL30) sequences (Mo-VL30). Recombination between MoMuLV and VL30 may contribute to the transduction of ras, as suggested by the finding that VL30 flanks the ras oncogene in all of the ras transducing viruses isolated from rats to date. The Mo-VL30 recombinant described here represents evidence that recombination between MoMuLV and VL30 can be uncoupled from the transduction of ras, and it may precede the transduction. Sequence comparison between clones of Mo-VL30, Harvey sarcoma virus (Ha-MSV), and genomic c-Ha-ras revealed that all three share a 124-bp region of 87.3% homology. This region was detected at nucleotide positions -1845 to -1720 of c-Ha-ras and 20 bp 5' of the recombination breakpoint between VL30 and ras in Ha-MSV. On the basis of the sequence comparison between VL30, Ha-MSV, and c-Ha-ras, we are proposing a model which explains how VL30 may have facilitated the transduction of c-Ha-ras and perhaps the other ras proto-oncogenes. According to this model, the sequence homology between VL30 and c-Ha-ras targets this gene for transduction by promoting the integration of the provirus in this locus through homologous recombination.     

Microsomal and cytosolic cytochrome P450 mediated benzo(a)pyrene hydroxylation in Pleurotus pulmonarius

Summary Microsomal and soluble fractions of Pleurotus pulmonarius exhibited a reduced carbon monoxide difference spectrum with P450 maxima at 448nm and 450–452nm respectively. Substrate induced Type I spectra were observed on addition of benzo(a)pyrene to both fractions. Benzo(a)pyrene hydroxylation was measured using the aryl hydrocarbon hydroxylase assay and was observed to be P450 dependent as indicated by carbon monoxide inhibition together with the substrate binding characteristics. The activity of the fractions were observed to give K_m of 200mM and 660mM and V_max of 1.25 nmol/min/nmol P450 and 0.57 nmol/min/nmol P450 for the microsomal and cytosolic fractions respectively.     

Regulatory T Cells Prevent Th2 Immune Responses and Pulmonary Eosinophilia during Respiratory Syncytial Virus Infection in Mice

During viral infection, inflammation and recovery are tightly controlled by competing proinflammatory and regulatory immune pathways. Respiratory syncytial virus (RSV) is the leading global cause of infantile bronchiolitis, which is associated with recurrent wheeze and asthma diagnosis in later life. Th2-driven disease has been well described under some conditions for RSV-infected mice. In the present studies, we used the Foxp3^DTR mice (which allow specific conditional depletion of Foxp3⁺ T cells) to investigate the functional effects of regulatory T cells (Tregs) during A2-strain RSV infection. Infected Treg-depleted mice lost significantly more weight than wild-type mice, indicating enhanced disease. This enhancement was characterized by increased cellularity in the bronchoalveolar lavage (BAL) fluid and notable lung eosinophilia not seen in control mice. This was accompanied by abundant CD4⁺ and CD8⁺ T cells exhibiting an activated phenotype and induction of interleukin 13 (IL-13)- and GATA3-expressing Th2-type CD4⁺ T cells that remained present in the airways even 14 days after infection. Therefore, Treg cells perform vital anti-inflammatory functions during RSV infection, suppressing pathogenic T cell responses and inhibiting lung eosinophilia. These findings provide additional evidence that dysregulation of normal immune responses to viral infection may contribute to severe RSV disease.     

Out of Africa and back again: nested cladistic analysis of human Y chromosome variation

We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544 individuals from Africa, Asia, Europe, Oceania, and the New World. Phylogenetic analyses of these nine sites resulted in a tree for 10 distinct Y haplotypes with a coalescence time of approximately 150,000 years. The 10 haplotypes were unevenly distributed among human populations: 5 were restricted to a particular continent, 2 were shared between Africa and Europe, 1 was present only in the Old World, and 2 were found in all geographic regions surveyed. The ancestral haplotype was limited to African populations. Random permutation procedures revealed statistically significant patterns of geographical structuring of this paternal genetic variation. The results of a nested cladistic analysis indicated that these geographical associations arose through a combination of processes, including restricted, recurrent gene flow (isolation by distance) and range expansions. We inferred that one of the oldest events in the nested cladistic analysis was a range expansion out of Africa which resulted in the complete replacement of Y chromosomes throughout the Old World, a finding consistent with many versions of the Out of Africa Replacement Model. A second and more recent range expansion brought Asian Y chromosomes back to Africa without replacing the indigenous African male gene pool. Thus, the previously observed high levels of Y chromosomal genetic diversity in Africa may be due in part to bidirectional population movements. Finally, a comparison of our results with those from nested cladistic analyses of human mtDNA and beta-globin data revealed different patterns of inferences for males and females concerning the relative roles of population history (range expansions) and population structure (recurrent gene flow), thereby adding a new sex-specific component to models of human evolution.      

Peptide analogues of 1811–1818 loop of the A3 subunit of the light chain A3-C1–C2 of FVIII of blood coagulation: biological evaluation

Factor VIII, the plasma protein deficient or defective in individuals with hemophilia A, is a critical member of the blood coagulation cascade. Recent studies have identified the FVIII light chain region Glu1811-Lys1818 as being involved in FIXa binding and in the assembly of the FX-activating FIXaz–FVIIIa complex. Based on this, a series of 12 peptides, analogues of the 1811–1818 loop of the A3 subunit of the light chain A3-C1–C2 of FVIIIa, were synthesized and evaluated for their anticoagulant activity. Only peptide Ac-ETKTYFWK-NH₂ showed significant anticoagulant activity by inhibiting about 40% factor VIII at a concentration of 0.43 mM. It also showed a prolongation of activated partial thromboplastin time of 6.1 s, whereas its effect on prothrombin time measurements was meaningless. All the other peptides did not show any measurable effect at the concentration of 0.43 mM. These findings are encouraging though further investigation of the effect of this active peptide in different biological settings is needed in order to evaluate its possible clinical applications.