Mutating P2 and P1 residues at cleavage junctions in the HIV-1 pol polyprotein. Effects on hydrolysis by HIV-1 proteinase.

Mutations were introduced into the P2 and P1 positions of the junctions, (a) linking reverse transcriptase (RT) and integrase (IN) (-Leu*Phe-) and (b) between the p51 and RNase H domain (-Phe*Tyr-) within p66 of RT in the HIV-1 pol polyprotein. Processing by HIV proteinase (PR) in cis was monitored upon expression of these constructs in E. coli. Whereas the presence of Leu or Phe in P1 permitted rapid cleavage at either junction, substitution of a beta-branched (Ile) hydrophobic residue essentially abolished hydrolysis. By contrast, placement of a beta-branched (Val) residue in the P2 position flanking such -Hydrophobic*Hydrophobic- junctions resulted in effective cleavage of the scissile peptide bond. Gly in P2, however, abrogated cleavage. The significance of these findings in terms of PR specificity, polyprotein processing and the generation of homodimeric (p51/p51) RT for crystallisation purposes is discussed.

Stabilisation of cathepsin E by ATP.

The hydrolysis of 3 distinct substrates by cathepsin E from human red blood cells and gastric mucosa was measured in the presence and absence of physiologically relevant concentrations of ATP. At pH values below about 5.0, the nucleotide was without effect. However, at pH 5.8, whereas cathepsin E was virtually inactive by itself, it was restored to full activity (kcat) by ATP and the non-hydrolysable methylene-ATP analogue. At still higher pH values, kcat progressively diminished but significant levels of cathepsin E activity were readily detectable at pH 7.0. The specificity of this stabilisation effect was examined.

Functional genomics.

We are in the midst of a genomics revolution. The first chapter of this revolution will end later this year with the completion of the first draft of the entire human genome; estimates for the exact number of genes in the human genome vary from 50,000 to 140,000. This endeavor has been a major catalyst for the genomics revolution and has moved science into uncharted territories, which has led to the need to establish both new disciplines and a new vocabulary. Thus we now have pharmacogenomics, genotyping, pharmacogenetics, microarrays, biochips, differential display, bioinformatics and cheminformatic. The meeting provided a taste of the wealth of information that is now being accumulated under the name of both genomics and proteomics. The challenge ahead will be turning this information into knowledge and then translating this knowledge into new therapies.

Chronic splenomegaly in Nairobi, Kenya. I. Epidemiology, malarial antibody and immunoglobulin levels.

Chronic splenomegaly in 131 Kenyan patients was investigated at Kenyatta National Hospital, Nairobi. Patients were allocated to diagnostic groups on the basis of clinical, haematological, parasitological, histological, radiological and endoscopic data. The major diagnostic groups were hyper-reactive malarial splenomegaly, our preferred name for tropical splenomegaly syndrome, (31%), hepatosplenic schistosomiasis (18%), visceral leishmaniasis (5%) and "indeterminate splenomegaly", where no diagnosis could be reached (12%). Another 20% of patients were suffering from various non-schistosomal forms of portal hypertension. A number of specific and rarer causes accounted for the rest of the cases. The tribal and geographical distribution of patients with chronic splenomegaly was compared with the pattern of general medical admissions. Splenomegaly was more frequent than expected in Kamba and Luo patients. Hyper-reactive malarial splenomegaly and hepatosplenic schistosomiasis were common in both groups, whereas visceral leishmaniasis was almost restricted to the Kamba and indeterminate splenomegaly was especially prevalent in the Luo. Malarial antibody and immunoglobulin levels differed significantly between the various diagnostic categories of patients and controls. Malarial serology can be diagnostically useful for chronic splenomegaly, provided results are interpreted in their geographical context.

Chronic splenomegaly in Nairobi, Kenya. II. Portal hypertension.

Eighty-five patients with chronic splenomegaly and proven oesophageal varices were studied at Kenyatta National Hospital, Nairobi. The major defined groups were hepatosplenic schistosomiasis (24%), cirrhosis (20%) and portal vein occlusion (11%). Hyper-reactive malarial splenomegaly (tropical splenomegaly syndrome) was considered as the cause of oesophageal varices in only one patient. In 26% of cases liver biopsy was non-diagnostic and the extrahepatic portal vein was demonstrated radiologically to be patent. Such patients were thought to be suffering from idiopathic portal hypertension, not previously described elsewhere in Africa. Hepatitis B surface antigen was detected in 12% of controls and in 58% of patients with cirrhosis (p less than 0.001). Some serological marker of previous hepatitis B virus infection was present in 92% of patients with cirrhosis and in 79% of controls. Kamba patients from Machakos and Kitui Districts were significantly more prevalent than expected among these 85 cases of portal hypertension.

Creatine phosphate (Neoton) as an additive to St. Thomas' Hospital cardioplegic solution (Plegisol). Results of a clinical study.

Experimentally, creatine phosphate (CP) added to St. Thomas' Hospital cardioplegic solution (STH) improved post-ischaemic recovery of cardiac function in the rat heart. We investigated the effect of adding CP (10.0 mmol/l) to STH. Fifty open-heart surgery patients were randomized into control (STH) and treated (STH + CP) groups (25 per group). Patients underwent (a) monitoring for peri- and postoperative arrhythmias (48-h Holter monitoring). (b) quantitative birefringence assessment of intraoperative myocardial protection in left and right ventricular biopsies sampled at start of bypass (pre-isch.), end of bypass (end-isch.) and after 10 min reperfusion (post-isch.), and (c) measurement of serum creatine kinase-MB isozyme (CK-MB) values for up to 4 days postoperatively; results were assessed with respect to (d) haemodynamics and postoperative clinical outcome. Inotropic support (adrenaline) was required in three patients (12%) from each group; no patient died. All patients required defibrillation, and the number of direct current shocks required for sinus rhythm was the same in each group. The occurrence and incidence of reperfusion-induced arrhythmias were the same in both groups. Serum CK and CK-MB values were similar throughout the sampling period in both groups of patients; one patient in the control group had raised CK-MB levels postoperatively, but perioperative infarction was not indicated by the electrocardiogram.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of standard (non-oxygenated) vs. oxygenated St. Thomas' Hospital cardioplegic solution No. 2 (Plegisol).

Recent studies have suggested that oxygenation of crystalloid cardioplegic solutions improves myocardial preservation. To assess whether oxygenation of St. Thomas' Hospital cardioplegic solution No. 2 (Plegisol) improves its clinical efficacy, 50 patients were randomly assigned into 2 groups: (1) those receiving Plegisol and (2) those receiving O2-Plegisol (PO2 greater than 500 mmHg at 4 degrees C). Efficacy was assessed by (a) clinical and haemodynamic parameters, (b) quantitative birefringence changes in response to ATP and calcium as a measurement of myocardial preservation in left and right ventricular biopsies, (c) creatine kinase (MB isoenzyme) release for up to 4 days postoperatively, (d) electrocardiographic (ECG) monitoring for up to 7 days postoperatively. There were no differences in mean age, ejection fraction, aortic cross-clamp duration, or bypass duration between the 2 groups of patients. In the Plegisol group, 2 patients (8%) died and 4 patients (16%) required inotropic support, whereas in the O2-Plegisol group there were no deaths and only 2 patients (8%) required inotropic support. These differences, however, were not statistically significant. Birefringence assessment demonstrated an improved myocardial response to ATP and calcium (predominantly in the left ventricular epimyocardium and in the right ventricular biopsies) at the end of ischaemia and after reperfusion in patients given O2-Plegisol. Deterioration in cellular assessment of myocardial contractility (measured by a reduction in birefringence of greater than 0.4 nm) was reduced from 20% in Plegisol patients to 12.5% in O2-Plegisol patients. CK-MB values showed no difference at any sampling time between the 2 groups of patients; a mean peak CK-MB of 35 IU/l occurred 2 h postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical validation of St. Thomas' Hospital cardioplegic solution No. 2 (Plegisol).

Recently, the St. Thomas' Hospital cardioplegic solution No. 2 (Plegisol) has become available commercially in the UK. In a series of patients (n = 28) undergoing open heart surgery for a variety of lesions, a clinical validation was performed. Preservation of myocardial contractility was assessed biophysically by quantitative birefringence measurements of myocardial biopsy samples (full thickness apical left ventricle and right ventricle) taken (1) prior to ischaemia, (2) at the end of ischaemia and (3) 10-15 min after reperfusion during cardiopulmonary bypass. In addition, serum CK-MB values were measured in samples taken throughout the operation and for 4 days postoperatively. Postoperative ECG traces (taken every 6 h for 48 h and then daily up to 7 days) were analysed to identify the occurrence of perioperative infarction. There were no hospital deaths. Chronotropic support was required in 5 of 28 patients (18%) for transient heart block. Low cardiac output did not occur postoperatively. Birefringence measurements in biopsy samples taken at the end of the ischaemic period (immediately prior to reperfusion) indicated an apparent left ventricular deterioration in myocardial contractility in 12 of 28 patients (43%) when compared to biopsies sampled prior to the ischaemic period. However, after 10-15 min of aerobic reperfusion, measurements indicated that myocardial contractility recovered to almost pre-ischaemic levels in the majority of patients. Thus, in 22 of 28 patients (79%), left ventricular deterioration did not occur in post-ischaemic biopsy samples when compared to the pre-ischaemic biopsies. Similarly, 21 of 28 patients (75%) had no deterioration of birefringence values in right ventricular biopsies.(ABSTRACT TRUNCATED AT 250 WORDS)

Magnesium and coronary revascularization.

Twenty patients, who underwent coronary revascularization without cardioplegic arrest, were given (during cardiopulmonary bypass) either magnesium chloride 16 mmol in 10 ml of water (magnesium group) or 10 ml of water alone (control group). Plasma and urinary magnesium concentrations were measured for 24 h after operation. ECG was recorded continuously during this period. QT intervals corrected for heart rate (QTcorr) were calculated from periodic full lead ECG. The mean plasma magnesium concentrations in the control group were less than normal throughout the study, while hypomagnesaemia did not occur in the magnesium group. Urinary magnesium excretion was higher in the magnesium group, with 58% of the administered magnesium excreted in the first 24 h. The observed incidence of frequent or ventricular arrhythmias was 22% in the magnesium group compared with 63% in the control group. No significant differences in QTcorr intervals were observed between the groups.

X-ray studies of aspartic proteinase-statine inhibitor complexes.

The conformation of a statine-containing renin inhibitor complexed with the aspartic proteinase from the fungus Endothia parasitica (EC 3.4.23.6) has been determined by X-ray diffraction at 2.2-A resolution (R = 0.17). We describe the structure of the complex at high resolution and compare this with a 3.0-A resolution analysis of a bound inhibitor, L-364,099, containing a cyclohexylalanine analogue of statine. The inhibitors bind in extended conformations in the long active-site cleft, and the hydroxyl of the transition-state analogue, statine, interacts strongly with the catalytic aspartates via hydrogen bonds to the essential carboxyl groups. This work provides a detailed structural analysis of the role of statine in peptide inhibitors. It shows conclusively that statine should be considered a dipeptide analogue (occupying P1 to P1') despite lacking the equivalent of a P1' side chain, although other inhibitor residues (especially P2) may compensate by interacting at the unoccupied S1' specificity subsite.

Immunoglobin M and malarial antibody levels in hyper-reactive malarial splenomegaly.

In a study of chronic splenomegaly in Kenya, hyper-reactive malarial splenomegaly, our preferred name for tropical splenomegaly syndrome, was diagnosed in 38 patients. This diagnosis was based on exclusion of other conditions and observations of hepatic sinusoidal lymphocytosis on liver biopsy. To assess the previously recommended diagnostic criterion of elevation of serum IgM, to two standard deviations (s.d.) above the local mean, serum IgM levels were measured in patients and in 90 geographically matched controls. Patients with IgM levels 2 s.d. above the local mean were compared with those with lower levels. No differences were found other than higher malarial antibody titres in the group with higher IgM levels. Agreement is required concerning diagnostic criteria for hyper-reactive malarial splenomegaly; other features of the syndrome may occur in the absence of marked IgM elevation.

Purification and properties of cathepsin D from rat Yoshida ascites hepatoma AH-130.

Cathepsin D was affinity-purified on pepstatin-Sepharose from control rat liver, from Yoshida ascites hepatoma (AH-130) cells, and from the liver of AH-130 tumour-bearing rats. Apparent molecular mass and immunological reactivity, as determined by SDS-PAGE and immunoblotting, were identical for the three enzyme preparations. The active enzyme concentrations were determined by active-site titration. Catalytic parameters were measured for the three enzymes using two synthetic chromogenic peptides as substrates, and inhibition constants were determined for the proteinases with a number of naturally-occurring as well as synthetic inhibitors. All three enzymes were clearly distinguished from cathepsin E, since none of them was affected by the protein inhibitor from Ascaris lumbricoides. The cathepsin D isolated from AH-130 cells was indistinguishable in its kinetic properties from rat liver cathepsin D, except in its susceptibility to inhibition by isovaleryl-pepstatin. On isoelectrofocusing, the isoenzyme pattern of the tumour enzyme was shifted somewhat towards more basic pI values by comparison with rat liver cathepsin D. These findings are considered with respect to the possibility of an alteration in the S4 subsite of the enzyme active site cleft.

CGP 38 560: orally active, low-molecular-weight renin inhibitor with high potency and specificity.

CGP 38 560 is a low-molecular-weight (730) inhibitor of human renin that contains only one natural amino acid. In vitro, it is a potent inhibitor of human renin (Ki with tetradecapeptide, 0.4 X 10(-9) M). It has a high enzyme specificity (Ki values against human pepsin, gastricsin, and cathepsin D are 5 X 10(-6), 3 X 10(-6), and 0.6 X 10(-6) M) and is also species specific (IC50 values against human, marmoset, dog, and rat plasma renins are 7 X 10(-10), 7 X 10(-10), 7 X 10(-9), and 1 X 10(-6) M). In vivo, CGP 38 560 inhibits plasma renin activity (PRA) and lowers blood pressure (BP) after oral administration to conscious, normotensive, furosemide-pretreated marmosets. A dose of 10 mg/kg induces complete inhibition of PRA and a decrease in BP of 23 +/- 3 mm Hg (n = 4) after 30 min. These effects persist for up to 2 h. Blockade of the renin-angiotensin system appears to cause the hypotensive response since it is completely prevented by pretreatment with a converting-enzyme inhibitor. These findings demonstrate that the molecular size of renin inhibitors may be reduced to improve their oral activity without loss of potency or specificity.

Identification of the aspartic proteinases from human erythrocyte membranes and gastric mucosa (slow-moving proteinase) as catalytically equivalent to cathepsin E.

Three aspartic proteinases with similar Mr values (approx. 80,000) but from distinct sources (human gastric mucosa, human erythrocyte membranes and rat spleen) were shown to have immunological cross-reactivity and comparable mobilities when subjected to polyacrylamide-gel electrophoresis under non-denaturing conditions. Kinetic parameters (kcat, Km and Ki) were determined for the interactions of the three enzymes with two synthetic chromogenic substrates and five inhibitors (naturally occurring and synthetic). On this basis it would appear that all of the enzymes should be considered equivalent to cathepsin E. pH-activity measurements indicated that the aspartic proteinase that originated from the erythrocyte membranes retained activity at a higher pH value than either of its readily soluble counterparts.

The selectivity of statine-based inhibitors against various human aspartic proteinases.

The interactions of five human enzymes (renin, pepsin, gastricsin, cathepsin D and cathepsin E) and the aspartic proteinase from Endothia parasitica with several series of synthetic inhibitors were examined. All of the inhibitors contained the dipeptide analogue statine or its phenylalanine or cyclohexylalanine homologues in the P1-P1' positions. The residues occupying the peripheral sub-sites (P4 to P3') were varied systematically and inhibitory constants were determined for the interactions with each of the proteinases. Inhibitors were elucidated that specifically inhibited human renin and did not affect any of the other human enzymes or the fungal proteinase. With suitable selection of residues to occupy individual sub-sites, effective inhibitors of specific human aspartic proteinases may now be designed.

The enhancer domain of the human cytomegalovirus major immediate-early promoter determines cell type-specific expression in transgenic mice.

The human cytomegalovirus (HCMV) major immediate-early promoter (MIEP) is one of the first promoters to activate upon infection. To examine HCMV MIEP tissue-specific expression, transgenic mice were established containing the lacZ gene regulated by the MIEP (nucleotides -670 to +54). In the transgenic mice, lacZ expression was demonstrated in 19 of 29 tissues tested by histochemical and immunochemical analyses. These tissues included brain, eye, spinal cord, esophagus, stomach, pancreas, kidney, bladder, testis, ovary, spleen, salivary gland, thymus, bone marrow, skin, cartilage, and cardiac, striated and smooth muscles. Although expression was observed in multiple organs, promoter activity was restricted to specific cell types. The cell types which demonstrated HCMV MIEP expression included retinal cells of the eye, ductile cells of the salivary gland, exocrine cells of the pancreas, mucosal cells of the stomach and intestine, neuronal cells of the brain, muscle fibers, thecal cells of the corpus luteum, and Leydig and sperm cells of the testis. These observations indicate that the HCMV MIEP is not a pan-specific promoter and that the majority of expressing tissues correlate with tissues naturally infected by the virus in the human host.