Use of Wishart Prior and Simple Extensions for Sparse Precision Matrix Estimation

A conjugate Wishart prior is used to present a simple and rapid procedure for computing the analytic posterior (mode and uncertainty) of the precision matrix elements of a Gaussian distribution. An interpretation of covariance estimates in terms of eigenvalues is presented, along with a simple decision-rule step to improve the performance of the estimation of sparse precision matrices and associated graphs. In this, elements of the estimated precision matrix that are zero or near zero can be detected and shrunk to zero. Simulated data sets are used to compare posterior estimation with decision-rule with two other Wishart-based approaches and with graphical lasso. Furthermore, an empirical Bayes procedure is used to select prior hyperparameters in high dimensional cases with extension to sparsity.     

The cloning and expression of a gene encoding haemolytic activity from the fish pathogen Renibacterium salmoninarum

A gene encoding haemolytic activity from Renibacterium salmoninarum (strain PPD) was cloned into Escherichia coli using the cosmid vector pHC79, and subsequently subcloned on a 1.6 kbp SAlI fragment into pBR328. Southern blot hybridisation revealed that a homologous sequence is found in other strains of R. salmoninarum.     

Presence of nucleosomes inPenicillium chrysogenum

We have studied the chromatin structure ofPenicillium chrysogenum. This fungus presents the typical nucleosomal repeat and the core DNA size characteristic of all the eukaryotes. The repeat length (about 180 base pairs) is in the range of those obtained for most fungi (160–180 base pairs) and shorter than in higher eukaryotes. Knowledge aboutP. chrysogenum chromatin structure opens the way to the study of the mechanisms of genetic regulation in this filamentous fungus.     

Mucosal epithelial cells and Langerhans cells are targets for infection by the immunosuppressive type D retrovirus simian AIDS retrovirus serotype 1

Simian acquired immune deficiency syndrome (SAIDS) caused by the type D retrovirus SRV-1 results in opportunistic infections and a spectrum of oral lesions similar to those seen in humans with AIDS. To better understand the pathogenesis of these oral lesions we have retrospectively examined the oral mucosa from ten rhesus monkeys that died with SAIDS and prospectively examined the oral mucosa of ten additional animals inoculated with SRV-1 to determine at what time, and in what cells SRV-1 infection of the oral mucosa occurs. Using single and double label immunohistologic techniques, and electron microscopy we detected SRV-1 in clusters of oral epithelial cells and rare Langerhans cells as early as 1 month postinoculation.     

In vitro activity of 15-azasterol (A25822B) against chalkbrood pathogen Ascosphaera apis in the honey bee

The antifungal agent 15-azasterol A25822B was examined for effects on the growth and development of Ascosphaera apis. The minimum inhibition concentration (MIC) of azasterol against A. apis was 1 m. Growth and development of A. apis was completely controlled at this concentration. At a concentration of 0.01 m growth of A. apis was retarded and although sporocysts were formed developing spores were not be able to reach maturation. A major effect of azasterol at this low concentration was the accumulation of lipid in the hyphae, sporocysts and immature spores. In addition it caused a conformational change in mitochondria and damage to the spore membrane structure. On the basis of these results, further investigations of azasterol for the treatment of chalkbrood disease in the honey bee are warranted.Work was performed during sabbatical leave at the University of California, Davis.     

Distribution of sulphate and iduronic acid residues in heparin and heparan sulphate

1. A method was developed for determination of the uronic acid composition of heparin-like glycosaminoglycans. Polymers or oligosaccharides are degraded to monosaccharides by a combination of acid hydrolysis and deamination with HNO₂. The resulting uronic acid monosaccharides (accounting for about 70% of the uronic acid contents of the starting materials) are isolated and converted into the corresponding aldono-1,4-lactones, which are separated by g.l.c. The calculated ratios of glucuronic acid/iduronic acid are reproducible within 5%. 2. Samples of heparin from pig intestinal mucosa (molar ratio of sulphate/disaccharide unit, 2.40) and heparan sulphate from human aorta (sulphate/disaccharide ratio, 0.46) were subjected to uronic acid analysis. l-Iduronic acid constituted 77% and 19% respectively of the total uronic acid contents. 3. The correlation between the contents of sulphate and iduronic acid indicated by this finding also applied to the fractionated deamination products of the two polymers. The sulphated fragments varied in size from disaccharide to octasaccharide (or larger) and showed sulphate/disaccharide molar ratios in the range of 0.05–2.0. The proportion of iduronic acid increased with increasing ester sulphate contents of the oligosaccharides. 4. Previous studies on the biosynthesis of heparin in a cell-free system have shown that l-iduronic acid residues are formed by C-5 epimerization of d-glucuronic acid units at the polymer level; the process requires concomitant sulphation of the polymer. The results obtained in the present structural study conform to these findings, and suggest further that similar mechanisms may operate in the biosynthesis of heparan sulphate. The epimerization reaction appears to be linked to the sulphation of hydroxyl groups but does not seem to require sulphation of the target uronic acid residues. The significance of sulphamino groups in relation to the formation of iduronic acid is unknown.     

Incidence of peptic ulcer disease in Gothenburg, 1985.

OBJECTIVE--To determine the incidence and age distribution of peptic ulcer disease in adults in Gothenburg. DESIGN--Retrospective study of patients with symptoms over one year. SETTING--All gastroenterology and x ray departments. PATIENTS--Any patient found to have an active ulcer crater during 1985. MAIN OUTCOME MEASURES--Sex, age, past history of gastrointestinal ulcers, and smoking habit. RESULTS--In 1985, 1402 peptic ulcers were diagnosed in 1137 adults. Over half (403; 54%) of the ulcers in men and 393 (60%) ulcers in women were in patients aged over 60. All types of ulcer showed increasing incidence with age. The sex ratio of patients aged 40-50 with peptic ulcers was 1:1. Nearly half (109; 48%) of ulcers diagnosed for the first time in men and 129 (57%) of such ulcers in women were in patients aged over 60. Elderly men and women were also more likely to develop haemorrhage. CONCLUSIONS--In Gothenburg there is a surprisingly high incidence of peptic ulcer disease, which increases considerably with age, possibly explained by the availability of modern diagnostic techniques as 1121 (80%) ulcers had been diagnosed by gastroscopy. Compared with earlier studies there was no difference in the incidence between men and women aged 40-50.     

Isolation of a pathogenic clone of mouse mammary tumor virus.

Exogenous mouse mammary tumor virus (MMTV) was cloned from a GR mammary tumor. Clone lambda GRT39 contained a full-length integrated MMTV(GR) provirus and both 5' and 3' host flanking DNA. The lambda GRT39 provirus had no apparent structural changes associated with cloning and retained the exogenous MMTV gag gene poison sequence. When introduced into rat mammary adenocarcinoma LA7 cells, the lambda GRT39 provirus was fully expressed. lambda GRT39-transfected LA7 cells made MMTV RNA, had gp52 SU protein on the cell surface, and produced B-type retrovirus particles characteristic of MMTV. Mammary tumors developed in hormone-stimulated BALB/c females injected with MMTV from lambda GRT39-transfected LA7 cells [MMTV (lambda GRT39)]. The tumors had new, clonally integrated copies of the MMTV(lambda GRT39) provirus and were expressing MMTV antigen. These data indicate that the lambda GRT39 provirus is biologically active and pathogenic.