Virulence of protein A-deficient and alpha-toxin-deficient mutants of Staphylococcus aureus isolated by allele replacement.

The gene coding for protein A (spa) of Staphylococcus aureus 8325-4 has been inactivated by substituting part of the spa coding sequence for a DNA fragment specifying resistance to ethidium bromide. The in vitro-constructed spa::EtBrr substitution mutation was introduced into the S. aureus chromosome by recombinational allele replacement. Southern blot hybridization showed that the in vitro-constructed mutation was present in the chromosomal spa locus. We have previously reported the inactivation of the alpha-toxin gene (hly) by allele replacement with an in vitro-constructed hly::Emr (erythromycin resistance) mutation (M. O'Reilly, J.C.S. de Azavedo, S. Kennedy, and T.J. Foster, Microb. Pathogen. 1:125-138, 1986). A double Spa- Hly- mutant was constructed by transduction. The virulence of Spa- and Hly- mutants was tested by experimental infection of mice. When subcutaneous injections were given, Hly- mutants formed a flat, darkened lesion, whereas Hly+ strains caused a raised, cream lesion. Alpha-toxin was shown to be a major factor in forming subcutaneous lesions and in causing the death of mice injected intraperitoneally. Spa- mutants were slightly less virulent than their Spa+ counterparts, which suggests that protein A is also a virulence factor of S. aureus.     

Thyroid hormone and development of the rat hippocampus: cell acquisition in the dentate gyrus

A quantitative autoradiographic histological study was carried out to examine mechanisms underlying the reduction in the rates of growth and of cell acquisition, including that of granule cells, in the dentate gyrus of hypothyroid rats. Thyroid deficiency in early life had no effect on the replication of intrinsic cells present in the polymorph and granular layers. The pyknotic index was also normal in the "proliferative zone", polymorph layer and granule cell layer, indicating that thyroid hormone had no effect on the survival of replicating, migrating or maturing granule cells. By contrast, the arrival of migrating cells from the "proliferative zone" to the granular layer was severely retarded in thyroid deficiency. This deficit was rapidly restored after a physiological dose of thyroxine given to hypothyroid rats. The present findings are consistent with our previous proposal that the role of thyroid hormone in the formation and/or the maintenance of nerve cells is related to changes in either cell migration or maturation, rather than to alterations in the replication of germinal cells.     

Fine mapping of a gene responsible for regulating dietary cholesterol absorption; founder effects underlie cases of phytosterolaemia in multiple communities

Sitosterolaemia (also known as phytosterolaemia, MIM 210250) is a rare recessive autosomal inherited disorder, characterised by the presence of tendon and tuberous xanthomas, accelerated atherosclerosis and premature coronary artery disease. The defective gene is hypothesised to play an important role in regulating dietary sterol absorption and biliary secretion, thus defining a molecular mechanism whereby this physiological process is carried out. The disease locus was localised previously to chromosome 2p21, in a 15 cM interval between microsatellite markers D2S1788 and D2S1352 (based upon 10 families, maximum lodscore 4.49). In this study, we have extended these studies to include 30 families assembled from around the world. A maximum multipoint lodscore of 11.49 was obtained for marker D2S2998. Homozygosity and haplotype sharing was identified in probands from non-consanguineous marriages from a number of families, strongly supporting the existence of a founder effect among various populations. Additionally, based upon both genealogies, as well as genotyping, two Amish/Mennonite families, that were previously thought not to be related, appear to indicate a founder effect in this population as well. Using both homozygosity mapping, as well as informative recombination events, the sitosterolaemia gene is located at a region defined by markers D2S2294 and Afm210xe9, a distance of less than 2 cM.     

Influence of different hormonal regimens on endometrial microvascular density and VEGF expression in women suffering from breakthrough bleeding

BACKGROUND: The aim of this study was to quantify blood vessel density (BVD) and immunoreactive vascular endothelial growth factor (VEGF) levels in endometrial biopsies taken from women suffering breakthrough bleeding (BTB) under different exogenous hormonal regimes. METHODS: Endometrial biopsies from women in Melbourne with BTB were divided into four groups: combined-continuous hormone therapy (HT) (estrogen and progestin taken daily), cyclical HT (daily estrogen with progestin for 14 days each cycle), progestin-only, or no HT. Subjects from Barcelona were using the Mirena intrauterine levonorgestrel-releasing system for contraceptive purposes, with menstrual diaries for classification into four groups (amenorrhea, infrequent, regular and prolonged). Control biopsies from Melbourne were included in the study. Endometrial samples were immunostained for VEGF and blood vessel localization using an antibody to CD34. RESULTS: Results showed that BVD was significantly reduced in the progestin-only treated group compared with the other three treatment groups (P = 0.028). In addition, all four Mirena BTB groups had significantly reduced BVD compared with controls. Considerable heterogeneity was observed in VEGF immunostaining within and between individual samples with no major differences between HT or Mirena. CONCLUSION: These results provide strong evidence that unopposed progestins reduce endometrial BVD and that there is no link between VEGF immunostaining and BVD or BTB.     

Frequent attenders in secondary care: a 3-year follow-up study of patients with medically unexplained symptoms

BACKGROUND: There are few longitudinal studies of patients with medically unexplained symptoms. The aim of this study was to investigate outcome in frequent attenders in secondary care who present repeatedly with medically unexplained symptoms. METHOD: Forty-eight patients presenting with medically unexplained symptoms, from a sample of 61, participated in a 3-year follow-up study. Psychiatric morbidity, functional impairment and use of services were evaluated. RESULTS: At follow-up there was a high prevalence of psychiatric morbidity with 69% having at least one psychiatric diagnosis. The sample continued to be high users of a range of health services and substantial functional impairment was reported. CONCLUSION: In this group of frequent attenders with medically unexplained symptoms outcome as measured by psychiatric morbidity, service use and functional impairment remained poor after 3 years.     

High tidal volume ventilation induces proinflammatory signaling in rat lung endothelium

Alveolar overdistension during mechanical ventilation causes leukocyte sequestration, leading to lung injury. However, underlying endothelial cell (EC) mechanisms are undefined. In a new approach, we exposed isolated blood-perfused rat lungs to high tidal volume ventilation (HV) for 2 h, then obtained fresh lung endothelial cells (FLEC) by immunosorting at 4 degrees C. Immunoblotting experiments indicated that as compared with FLEC derived from lungs ventilated at low volume (LV), HV markedly enhanced tyrosine phosphorylation (TyrP). The tyrosine kinase blocker, genistein, inhibited this response. HV also induced focal adhesion (FA) formation in FLEC, as detected by immunofluorescent aggregates of the alpha(v)beta(3) integrin that co-localized with aggregations of focal adhesion kinase (FAK). Immunoprecipitation and blotting experiments revealed that HV increased TyrP of the FA protein, paxillin. In addition, HV induced a paxillin-associated P-selectin expression on FLEC that was also inhibited by genistein. However, HV did not increase lung water. These results indicate that in HV, EC signaling in situ causes FA formation and induces TyrP-dependent P-selectin expression. These signaling mechanisms may promote leukocyte-mediated responses in HV.     

Expression of CD4 on peripheral blood granulocytes. a novel finding in a case of myelodysplastic syndrome in association with t(5;12)

Myelodysplastic syndromes (MDS) are associated with cell maturation defects that can manifest as abnormal surface antigen expression. We describe a patient with refractory anemia with excess blasts, who presented with infection and extensive dysplastic features in peripheral blood granulocytes. The granulocytes expressed CD11b, CD13, CD15, CD33, and CD43. The granulocytes also expressed CD4 antigen. Cytogenetic analysis showed a clonal t(5;12)(q33;p13). The patient improved on antibiotics with partial improvement in the dysplastic features. However, shortly after, the patient experienced paravertebral extramedullary blast transformation followed by a leukemia phase of acute monoblastic leukemia. The patient died a few days later. This is the first report describing anomalous expression of CD4 on granulocytes in MDS. Since the breakpoint on chromosome 12 is near the CD4 gene, which is mapped to 12p12, we hypothesize that dysregulation of the CD4 gene may have occurred resulting in its persistent expression on mature and maturing granulocytes.