Addition-order dependent modulation of the sensitivity of rabbit erythrocyte membrane to bee venom phospholipase A2 by oleic acid, lysophosphatidyl choline and albumin

The addition of exogenous oleic acid to erythrocyte membranes induces a characteristic membrane crenation and sensitises the cells to the lytic action of phospholipase A2 enzymes. Both effects are extremely sensitive to inhibition by endogenous lysophosphatidyl choline (LPC), but the strength of inhibition depends of the order in which the reagents are added to the cells. These responses are further enhanced when the reagents are extracted from the cell membranes by treatment with albumin. Thus the inhibitory action of LPC added before oleic acid increases when the reagents have been extracted but that of LPC added after oleic acid decreases after extraction. The results are discussed in terms of the stimulation of PLA2 activity by enhanced membrane curvature.

Into the dangerous world: an in vivo study of information processing in agoraphobics

The differential processing of threatening information in anxious patients is now well established, but there has been little attention to situational variation in information processing. A review of the experimental literature suggests that agoraphobics should show interference in the performance of the modified Stroop task for threat words and that this interference should increase in phobic situations. In the present study, agoraphobics and normal controls carried out the Stroop task either in a safe setting or a public place. Agoraphobics showed greater interference with threat words but this interference was not affected by setting. The implications of this result are considered.

Reversible renal failure in renal transplant patients receiving oral acyclovir prophylaxis

Two children who developed acute renal failure in the immediate post-renal transplantation period are presented. Each was immunosuppressed with cyclosporin and was also receiving oral acyclovir for prophylaxis against cytomegalovirus infection. Renal biopsy findings suggested drug toxicity. Discontinuation of acyclovir coincided with reversal of renal impairment. As cyclosporin levels were at the lower end of the therapeutic range, we believe acyclovir to be the likely causative agent.

Zinc and barium inhibit the phospholipase A2 from Naja naja atra by different mechanisms

The mode of inhibition of the phospholipase A2 (PLA2) enzyme from the Chinese cobra (Naja naja atra) by Zn2+ is qualitatively different from inhibition by Ba2+. Inhibition by Ba2+ shows the kinetic characteristics of a conventional competitive inhibitor acting to displace Ca2+ from a single essential site, but Zn2+ has the paradoxical property of being more inhibitory at high than at low Ca2+ concentration. Kinetic analysis of the Ca(2+)-dependence of enzymic activity shows a bimodal response, indicating the presence of two Ca(2+)-binding sites with affinities of 2.7 microM and 125 microM respectively, and we propose that these can be identified with the two Ca(2+)-binding sites revealed by crystallographic analysis [White, Scott, Otwinowski, Gleb and Sigler (1990) Science 250, 1560-1563]. The results are consistent with the model that the enzyme is activated by two Ca2+ ions, one that is essential and can be displaced by Ba2+, and one that modulates the activity by a further 5-10-fold and which can be displaced by Zn2+. An alternative model is also presented in which the modulating Zn(2+)-binding site is a phenomenon of the lipid/water interface.

Prognostic significance of left ventricular aneurysm in the Cardiac Arrhythmia Suppression Trial (CAST) population

Left ventricular aneurysm has been associated with increased mortality rates. The Cardiac Arrhythmia Suppression Trial (CAST) database was used prospectively to assess (1) the prognostic significance of left ventricular (LV) aneurysm after myocardial infarction on mortality rates and (2) the relation of LV aneurysm to ventricular arrhythmias and their suppressibility. All patients in the CAST study were enrolled after myocardial infarction. They had > or = 6 ventricular premature depolarizations (VPDs) per hour and ejection fraction < or = 55%; they were enrolled in the study an average of 96 days after the index myocardial infarction. Of 2494 patients with wall motion data, 164 had LV aneurysm, 600 had only dyskinesis, 913 had only akinesis, and 817 had none of these. Radionuclide scan was used in 39%, two-dimensional echocardiography in 30%, and LV angiogram in 31%. Baseline VPDs and nonsustained ventricular tachycardia were similar in all groups. LV aneurysm patients were more frequently eliminated during open-label titration. The incidence of sustained VT during follow-up was only 2.8% for aneurysm patients, a rate that was similar to the other groups. Patients with LV aneurysm had significantly lower survival rates (82% vs 91%) at 16 months after study entry than those without these wall motion abnormalities (p < 0.005). When survival rates were adjusted for ejection fraction there was still a moderately large hazard ratio (1.34) of LV aneurysm that was not statistically significant (p = 0.18). We conclude that (1) the presence of LV aneurysm does not independently worsen prognosis, and (2) older concepts of LV aneurysm and ventricular arrhythmias must be reevaluated.

Insulin sensitivity and metabolic clearance rate of insulin in cystic fibrosis

We have evaluated the metabolic clearance rate (MCR) of insulin and insulin sensitivity in 12 older patients with cystic fibrosis (CF) using the hyperinsulinemic euglycemic clamp method. Compared with a control group matched accurately for age and body mass index (BMI), the MCR of insulin was significantly enhanced in CF CF = 21.85 +/- 1.17 v controls = 16.01 +/- 0.92 mL/kg/min, P < .005), and this difference persisted after correction for lean body mass ([LBM] CF = 26.32 +/- 1.28 v controls = 19.09 +/- 1.09 mL/kg LBM/min, P < .005). Glucose disposal rates (M) were similar in the two groups during the clamp (CF = 7.28 +/- 0.41 v controls = 6.83 +/- 0.60 mg/kg/min, P > .5), but the insulin sensitivity index, M/I x 100 (I = steady-state insulin concentration), was markedly increased in the CF group (CF = 17.62 +/- 1.30 v controls = 11.75 +/- 0.71, P < .005). In conclusion, the MCR of insulin is enhanced in CF, which is in keeping with previous observations on drug metabolism in this disorder. Second, insulin sensitivity is increased in CF, and this points to a compensatory mechanism to counteract the insulinopenia.

Purification and activation of phospholipase A2 isoforms from Naja mossambica mossambica (spitting cobra) venom

Isoforms of phospholipase A2 (PLA2) from the venom of Naja mossambica mossambica (the spitting cobra) were purified by a combination of gel filtration on Bio-gel P-30 and ion exchange chromatography on DE-52 Cellulose and the purification followed by three types of polyacrylamide gel electrophoresis. SDS PAGE failed to resolve the active band into separate isoforms. Acid/urea PAGE, resolved the peptides and major protein components of the venom and was able to separate two PLA2 bands in the whole venom. Alkali/urea PAGE resolved four PLA2 bands in whole venom, but could resolve six distinct purified PLA2 species. Of the known isoforms, the acidic form (CM-1) was purified to homogeneity. The basic non-toxic isoform (CM-II) was shown to migrate as a close doublet of PLA2 isoforms. A novel minor purified isoform was identified with mobility intermediate between CM-I and the basic non-toxic isoform CM-II. CM-III was shown to contain a minor PLA2 contaminant. The analysis was facilitated by the fact that all of the isoforms could be eluted from the gels with > 60% recovery of activity. The venom therefore contains at least six isoforms of PLA2 which differ largely by their content of acidic acids. Oleoyl imidazolide treatment increased the haemolytic activity of all but the toxic PLA2 isoform in Naja mossambica mossambica, but partially inhibited the catalytic activity of acidic, toxic and newly purified isoforms whilst partially activating the non-toxic isoform.

A study of the photostability of ergocalciferol (vitamin d(2)) in organic solvents

The photolysis of ergocalciferol (vitamin D(2)) in several organic solvents has been studied to determine the influence of solvent dielectric constant and viscosity on the rate of reaction. Ergocalciferol degrades by zero-order kinetics and the rate constants vary from 0.74x10(-5) mol 1(-1) (methanol) to 1.56x10(-5) mol 1(-1) (chloroform). The rates appear to be a linear function of the reciprocal of dielectric constant and viscosity of the medium in the range studied.

Differentials in health-related variables among children at a diarrhoea training unit in Pakistan

The study assesses gender differences and other variables related to diarrhoea in 500 children less than two years of age at a diarrhoea training unit (DTU). During the study period, 78% of the children (51% males and 49% females) who were brought for care had no dehydration. More female children were malnourished than male. Exclusively bottle-fed infants were malnourished in higher proportion than those breastfed exclusively or partially. With worsening of nutritional status, severity of dehydration increased but it had no effect on the frequency of dysentery which was seen in 11 females and 10 males. Appropriate supplementary feeding was alarmingly low. Eighty-seven per cent of children 9-24 months of age had received their immunisation against measles. All children were rehydrated at the DTU and not a single case required admission. The study does not show preferential care-seeking for male children and suggests that educational efforts be focused on exclusive breastfeeding, appropriate weaning and home management of those cases with no dehydration.

Physical symptoms and illness attributions in agoraphobia and panic

The cognitive model of panic disorder proposes that panic patients interpret physical symptoms in a catastrophic way, thus precipitating panic attacks. This study describes the development of a questionnaire measure designed to assess beliefs about the health implications of various symptoms. Two groups, agoraphobics and normals, were compared on a variety of measures. Agoraphobics showed much higher panic frequency, fear of anxiety, and prevalence of frightening cognitions when anxious, but did not score higher than normals when assessing seriousness of symptoms. The implications of these results are considered.

Effect of dehydration on the disposition kinetics of erythromycin in rabbits

The effect of water deprivation on the physiologic, biochemical, and disposition parameters of erythromycin was investigated in rabbits. The packed cell volume, plasma glucose, and total lipid concentration increased significantly in dehydration. The pharmacokinetic parameters of erythromycin after intravenous administration also changed, suggesting a need for monitoring toxicity of erythromycin in the water-deprived population.

Effect of viscosity and buffer salts on the stability of sulphacetamide solutions

A study of identification and rate determination of degradation products of sulphacetamide in aqueous solutions during UV irradiation and thermolysis at 70 degrees , 80 degrees and 90 degrees C is made. The effect of viscosity and buffer salts in presence of antioxidants on the rate of hydrolysis is investigated. An increase in the viscosity of solution results in a decrease in the rate of hydrolysis. Similar viscosity effect has been observed on the photolysis of sulphacetamide solutions. No significant salt effect on the rate of hydrolysis of sulphacetamide in citrate and phosphate buffers (pH7.4) has been noticed. The thermodynamic parameter, E(a), deltaH, deltaS for the reaction have been determined.

Diagnosis of urinary tract infection in children: fresh urine microscopy or culture?

Fresh unspun and unstained urine specimens from 342 children with previous urinary tract infection (UTI) or symptoms compatible with a UTI were examined by microscopy at a magnification of x 400 in a mirrored counting chamber by a clinician, and sent for culture in a microbiology laboratory; 200 samples were also plated onto dip-slides. When microscopy and culture results were discrepant, further urine samples were collected until a diagnosis of UTI (24) or sterile urine (318) could be confirmed. Initial microscopy correctly identified 23 of 24 UTIs and 286 of 318 sterile urines; 1 false-positive result was caused by vaginal contamination with lactobacilli. 32 specimens (9%) gave an equivocal result on microscopy; the 1 other true-positive result was identified correctly on microscopy of the next urine specimen obtained. Culture of the initial urines correctly identified all 24 UTIs, but only 82% of the negative samples. Of the samples from uninfected children, 35 (11%) showed a mixed growth which was sterile on repeat sampling, and 21 (6.6%) initially grew a false-positive pure growth of more than 10(5) colony-forming units/ml of one organism. True UTIs were associated with bacterial counts above 10(7)/ml. Microscopy by a clinician represents a cheaper, quicker, and more reliable screening test for UTI in children than does routine culture in a microbiology laboratory.

Urine collection from disposable nappies

Urine was collected for microscopy and culture by standard use of sterile adhesive bags and by extraction from wet disposable nappies from 45 patients aged 1 to 23 months. Urine can readily be obtained by compression of wet nappy fibres within a 20 ml syringe if highly absorbent brands that contain gel beads are avoided. Red and white cell numbers were reduced on light microscopy of specimens obtained from nappies, but bacterial counts were unchanged. On culture, 6 children were shown to have urinary tract infections by both methods; of the children who did not have a urine infection, the contamination rate was lower from nappy collections (10/39 vs 17/39 from urine bags). Biochemical analysis of urine collected from 11 older children showed very close correlation for sodium, potassium, urea, and creatinine concentrations and osmolality between freshly voided urine and samples obtained after they were soaked into disposable nappies for 3 h and reclaimed, although there was greater variation for measurements of calcium and phosphate. Extraction of urine from disposable nappies put on within 4 h and which are not soiled by faeces is an inexpensive, rapid, and simple method to collect urine from young children for culture, microscopy for bacteria, and biochemical analysis.

The conversion of primaquine into primaquine-aldehyde, primaquine-alcohol, and carboxyprimaquine, a major plasma metabolite

Although efficacy and toxicity of primaquine (PQ) depend on bioconversion, the process is poorly understood, even for carboxyprimaquine (CPQ), the major plasma metabolite. Earlier work to clarify drug metabolism showed that PQ could be converted quantitatively into CPQ, in vitro, with human erythroleukemic K562 cells or nonleukemic bone marrow supplemented with calf serum. We have now found--using systems with serum only, as well as with K562, bone marrow, and adult or embryonic liver cells--that the bioconversion of the side chain of PQ involves a branched pathway with at least three separate enzymes and two derivatives other than CPQ. An oxidase activity in serum converted PQ first into a novel side chain aldehyde (Y). Aldehyde dehydrogenase transformed PQ-aldehyde into CPQ in cell-free systems and in K562, bone marrow, and adult liver cells. Embryonic hepatocytes or bone marrow treated with 1,3-bis(2-chloroethyl)-1-nitrosourea did not produce CPQ; instead, they made a metabolite (Xc) that we could synthetize via PQ-aldehyde and identify as PQ-alcohol. PQ-alcohol replaced CPQ as the final product whenever alcohol-dehydrogenase prevailed over aldehyde dehydrogenase. These enzymes operated in intact cells and controlled the biotransformation of PQ absolutely. Unless both dehydrogenase were absent, inhibited, or deprived of coenzyme, potentially cytotoxic PQ-aldehyde intermediate did not accumulate. Some of the unique tissues schizonticidal and gametocidal effects of PQ may depend on the distribution pattern and relative activities of PQ oxidase, aldehyde dehydrogenase, and alcohol dehydrogenase in human subjects and in parasites.

A study on stability of mestranol

Mestranol, a synthetic oestrogcn, is an oral contraceptive given alongwith progestogens. It is light, heat and air sensitive and on uv irradiation new polymeric species of glucosiduronate and sulphate conjugate are formed. The new species fractions of mestranol are separatable over sephadex in column chromatography and characterized by analytical techniques employed in this investigation. This investigation is aimed to study formation of these species quantitatively for stability induced formulations.

Pyogenic meningitis in hospitalized children in Kelantan, Malaysia

A 2.5-year retrospective study of pyogenic meningitis in hospitalized children in Kelantan was carried out with regard to aetiology, clinical features, investigation, treatment and outcome. There were 58 children with 43 cases (74.1%) occurring below the age of 1 year. Frequent presenting symptoms included fever (98.3%), fits (77.6%), anorexia (39.7%), vomiting (34.5%) and drowsiness (12.1%). On admission, 37 (63.7%) had neck stiffness, 10 (17.2%) had Kernig's sign and 32 (55.2%) had coma. CSF cultures were positive for Haemophilus influenzae in 29 (50%), Streptococcus pneumonia in 13 (22.4%) and Neisseria meningitidis in 3 (5.2%). The antibiotic sensitivity profiles showed that the three main organisms were 100% sensitive to Chloramphenicol, Streptococcus pneumoniae was 100% sensitive to penicillin, Neisseria meningitidis was 100% sensitive to penicillin and ampicillin, and Haemophilus influenzae was 90% sensitive to penicillin and ampicillin. The total hospital mortality was 18.9%. All but two of the eleven deaths occurred in children younger than 1 year. Nineteen of the 35 (54.3%) survivors attended for at least one follow-up after discharge from hospital. Of these 19 children, 47.4% had neurological sequelae.

Multicomponent spectrophotometric assay of sulphacetamide and photodegradation products

A multicomponent, spectrophotometric method has been developed for the simultaneous determination of sulphacetamide, sulphanilamide and major degradation products in photolysed solutions. It is based on a three component (Sulphacetamide, sulphanilamide and azobenzene-4, 4'-disulphonamide) assay at pH 4.0 using 258, 268 and 320 nm as analytical wavelengths. The blue oxidation product of sulphanilamide is determined independently at 550 nm. The reproducibility of the method judged by the analysis of synthetic mixtures, is within +/- 5%. The method is stability indicating for the assay of sulphacetamide in degraded eye-drop preparations and could also be conveniently used for photodegradation studies.

Photo-oxidation of sulphanilamide to blue product

Aqueous solutions of sulphanilamide undergo photolysis to produce several compounds including the blue oxidation product. The kinetics of the reaction leading to blue product has been studied and the apparent first-order rate constants for the formation of blue product at pH 1-11 have been calculated. Effect of certain antioxidants on this reaction at pH 7.0 and rates of inhibition have been determined. Ascorbic acid has been found to completely inhibit the formation of blue product. A reaction pathway for the photo-oxidation of sulphanilamide to blue product has been suggested. The blue product has been shown (James, 1940) to possess much higher antibacterial activity than sulphanilamide.

Failure of spermatozoa from T/t mice to fertilize in vitro is overcome by zona drilling

Failure of epididymal spermatozoa from T/t mutant mice, but not from t/t individuals, to fertilize oocytes in vitro was partially overcome by opening a small aperture in the zona pellucida with acidified Tyrode's solution to permit direct access of the spermatozoon to the vitellus. This study provides a model system to evaluate requirements for successful zona drilling in the treatment of human infertility and further insights into the effects of the t complex on sperm fertility.

Photo-oxidation of sulphanilamide to azo and azoxy compounds

The second-order kinetics for the photochemical formation of azobenzene-4, 4-disulphonamide has been studied at pH 1-11 and at pH 7.0 in the presence of five antioxidants. The rate constants are not affected by changes in pH in the region of 5-9 at which the molecule is predominantly in the unionised form. The rate of formation of azobenzene-4, 4'-disulphonamide is inhibited upto 80% by ascorbic acid. A scheme for the photo-oxidation of sulphanilamide to the azo and azoxy derivatives has been outlined.