Stability of subtilisins and related proteinases (subtilases)

The stability towards thermal and chemical (guanidine hydrochloride, GnHCl) denaturation of six inhibited subtilases (mesentericopeptidase, subtilisins BPN′, Carlsberg and DY, proteinase K and thermitase) has been investigated by kinetic and equilibrium studies. The unfolding processes were monitored by circular dichroic and fluorescence spectroscopy. Experiments in the absence and presence of extraneous calcium in the concentration range 2×10^?3-10^?1 M were performed. The presence of calcium in the weak calcium binding site changes the denaturation drastically. The heat- (or GnHCl-) induced unfolding curves obtained using CD spectroscopy show two independent transitions which seem not to have been resolved before. The presence of Ca²⁺ in the second (third in the case of thermitase) binding site increases the T_m, values by 11-21 °C and the δG_D(H₂O) values obtained from denaturation experiments in GnHCl by 6.7-7.2 kcal/mol when an extraneous Ca²⁺ concentration of 2 × 10^?2 M was used. One interpretation is that the initial step of denaturation in the presence of added calcium is the formation of a partially unfolded intermediate form, retaining a highly ordered structure with 60-85% of the a-helix structure of the native enzyme. This intermediate then unfolds at a temperature considerably higher than that of the same proteinases in the absence of added Ca²⁺. The free energy of stabilization of the intermediates is increased by 1.8-2.8 times in comparison with that for the unfolding reactions of the subtilases with empty Ca2/Ca3 binding sites. A second interpretation is that the two steps in the unfolding curves correspond to enzyme without and with calcium in the weak binding site. Fluorescence experiments confirm the mechanism involving the formation of intermediate states. The results are discussed in relation to the X-ray models of the six subtilases.     

Clinical Experience with Expanded Polytetrafluoroethylene Gore-Tex® Surgical Membrane for Pericardial Closure: A Study of 110 Cases

Complete closure of the pericardium after cardiac operations has the advantage of avoiding injury of the heart and great vessels during reoperation. Between 1985 and 1987, the pericardium was closed with Gore-Tex Surgical Membrane (SM) in a selected series of 110 patients 1 month to 76 years of age. Fifty-three patients had congenital heart lesions and 57 patients had acquired heart disease. Overall hospital mortality was 3/110 cases. In no instance was there a relationship between occurrence of death and pericardial closure with SM. There was one episode of cardiac tamponade on the seventh postoperative day. One patient developed fever and leukocytosis due to a mediastinal hematoma. During a mean follow-up of 15 months, four patients had to be reoperated upon three, four, eight weeks, and eight months after primary operation. The anterior wall of the heart had no adhesion with the SM and the other parts of pericardium could be dissected easily. Scanning electron microscopic examination of the explanted SM patches showed neither cellular ingrowth nor immunocompetent cellular elements. The Gore-Tex Surgical Membrane has the advantages of easy availability and lack of reaction between its surface and the epicardium and pericardium. We believe its routine use should be encouraged in patients with high probability of reoperation after repair of complex cardiac anomalies, implantation of bioprostheses, coronary revascularization for one- or two-vessel disease, and repair of degenerative disease of the ascending aorta.     

Peripancreatic lymphoadenopathy and extrahepatic immunological manifestations in chronic hepatitis C

Abstract. The aim of the study was to determine the role of peripancreatic lymph node swelling in systemic immunological alterations during chronic hepatitis C (HC). The prospective study was carried out as a clinical study in a university hospital. Clinical, haematochemical and ultrasonographic findings in 182 patients were studied. Ultrasonography was performed by the same operator and the findings were evaluated blind without the operator knowing the clinical and haematochemical parameters. Hepatitis B virus (HBV) markers, anti-HCV antibodies. LKMl, cryoglobulinaemia, rheumatoid factor and anti-tissue antibodies were determined. Liver biopsy was carried out in 43 of the 182 patients. One or two pathological peripancreatic lymph nodes (PLNs) were present in 30 of the 182 patients and, of the 30, 28 were anti-HC positive. Only one patient in the non-PLN group was positive for anti-HCV, there being statistical significance ( P <0.0001) between the PLN and non-PLN groups. In HCV-positive patients, extrahepatic immunological manifestations were observed (cryoglobulinaemia; positivity to anti-smooth muscle, antinuclear and antimitochondrial antibodies; positivity to rheumatoid factor and LKMl). In five patients the presence of focal lymphocytic aggregates was detected by biopsy, whereas one patient presented typical ocular lesion of Mikulicz's syndrome. Our results may confirm the marked lymphotropism shown by the HC virus and indicate more complex immune system involvement, especially in view of the coexisting signs of immune system involvement related to the presence of intrahepatic cellular aggregates detected in our study. We believe that the peripancreatic adenopathy in chronic HCV hepatitis is an important diagnostic sign and may indicate an involvement of the C virus in the still unexplained extrahepatic immunological disorders.     

Chronic Morpholine Exposure of Rats

Chronic Morpholine Exposure of Rats. HARBISON, R. D., MARINO,D. J., CONAWAY, C. C., RUBIN, L. F., AND GANDY, J. (1989). FundamAppl. Toxicol. 12,491–507. The chronic toxicity and carcinogenicpotential of morpholine were evaluated in 60 Sprague-Dawleyrats/sex/group receiving morpholine at mean inhalation exposureconcentrations of 0, 10, 50 and 150 ppm for 6 hr/day, 5 days/week,for 104 weeks. Survival, body weight gains, organ weights, hematology,and clinical chemistries were normal in exposed groups and comparableto those of the control animals. The incidences of palpabletissue masses and of histologically confirmed neoplasia werecomparable among all groups, including the control groups, andwere typical of the strain and age of the rats tested. In-lifeclinical examinations revealed increased incidences of irritationaround the eyes and nares, chromadacryorrhea, and urine stainson the fur, predominately in high-dose animals. Morpholine exposurewas associated with corneal irritation seen by ophthalmoscopicexamination and confirmed microscopically as keratitis limitedto the highest exposure group. Irritation of the maxillary andnasoturbinates as indicated by infiltration of neutrophils,focal squamous metaplasia of the turbinate epithelium, and necrosisof the turbinate bone was observed in high-dose animals. Therefore,chronic exposure of rats to morpholine for 2 years at concentrationsof 150 ppm or less revealed no carcinogenic potential or chronicsystemic toxicity. Consistent with its known irritating properties,morpholine produced only local irritation, which was limitedalmost exclusively to high-dose animals.     

Allogeneic bone marrow transplantation versus chemotherapy in high-risk childhood acute lymphoblastic leukaemia in first remission

We compared the outcome of children with high-risk acute lymphoblastic leukaemia (HR-ALL) in first complete remission (first CR) treated with chemotherapy (CHEMO) or with allogeneic bone marrow transplantation (BMT) in a multicentre study.   All children treated by the Italian Paediatric Haematology Oncology Association for HR-ALL in first CR between 1986 and 1994 were eligible for the study. 30 children were given BMT at a median of 4 months from first CR, with preparative regimens including total-body irradiation ( n  =25/30). 130 matched controls for BMT patients were identified among 397 HR-ALL CHEMO patients. Matching on main prognostic factors and duration of first CR was adopted to control the selection and time-to-transplant biases. The comparative analysis was based on the results of a stratified Cox model. The estimated hazard ratios of BMT versus CHEMO at 6 months, 1 year and 2 years after CR were 1.38 (CI 0.59–3.24), 0.69 (CI 0.27–1.77) and 0.35 (CI 0.06–1{\raise 5mu ..91), with an overall non-significant difference between the two groups ( P  = 0.34). With a median follow-up of 4 years, the disease-free survival was 58.5% (SE 9.3) in the BMT group and 47.7% (SE 4.8) in the CHEMO group, at 4 years from CR. Non-leukaemic death occurred in 4% of CHEMO and 10% of BMT patients. In the BMT group the estimated cumulative incidence of relapse at 1.5 years from CR was 31.5% (SE 8.8) and did not change thereafter, whereas in the CHEMO group the corresponding figure was 29.2% (SE 4.1) and the incidence continued to increase thereafter (48.2% (SE 4.8) at 4 years from CR).   The results of this study suggest that, with respect to the CHEMO group, the higher risk of early failure in the BMT group is outweighed by the lower risk of relapse after 1 year. Results prompt the need for a prospective study, in order to demonstrate the likely advantage of BMT in HR childhood ALL in first CR.