Molecular structure of F-actin and location of surface binding sites

Comparisons of three-dimensional maps of vertebrate muscle thin filaments obtained by cryo-electron microscopy and image analysis, reveal the molecular structure of F-actin, the location of the C terminus of the monomer and the positions of the binding sites of tropomyosin, the myosin head and the N-terminal portion of the myosin A1 light chain on the filament. These data provide strong constraints for evaluating models built from the atomic structure of the monomer and the subsequent identification of molecular contacts.

Cholinesterase deficiency and the Churg-Strauss syndrome

We report two patients with the Churg-Strauss syndrome who were found to have decreased cholinesterase activity despite normal phenotypes. Suspicion of abnormal sensitivity to suxamethonium in the first case was raised after prolonged paralysis under anaesthesia. The findings in the second were incidental during the course of intensive care treatment. Both patients received immunosuppressive therapy. Differentiation between the effects of this and the disease process itself cannot be established.

Observations on abortion in Zambia

This report describes the findings of a preliminary investigation of women who sought treatment for abortion from the Gynecological Emergency Ward at the University Teaching Hospital (UTH) in Lusaka, Zambia. Barriers to obtaining legal abortions are identified and the harsh experiences of women seeking treatment for complications of illegally induced abortion are discussed. The data contribute to an understanding of the intensity of abortion for Zambian women and draw attention to the value of small-scale, qualitative research on women's reproductive health care needs. It is suggested that a study be planned at UTH to determine how health care delivery can be improved for women who seek abortion.

Molecular genetic approaches for the diagnosis of clonality in lymphoid neoplasms

Rearrangements of immunoglobulin (Ig) and T cell receptor (TCR) genes provide a highly sensitive molecular marker for the detection of clonality in lymphoid lesions and allow the pathologist to (1) distinguish polyclonal from monoclonal lymphoid proliferations, (2) provide corroborative evidence for lineage when used in conjunction with immunophenotypic techniques, (3) differentiate clonal lymphoid lesions from poorly differentiated nonlymphoid neoplasms, and (4) assess residual disease at the molecular level. The use of these probes in conjunction with morphology and immunohistochemistry or flow cytometry allows the pathologist to assign virtually all lymphoid neoplasms to the B or T cell lineage. The cloning of Ig and TCR genes also has led to the identification of new protooncogenes that reside at the breakpoints of chromosomal translocations frequently observed in lymphoid neoplasms. Molecular probes for these new genes involved in the pathogenesis of lymphoid neoplasms may be used as additional molecular markers for the determination of clonality, lineage, and even histologic subtype of lymphoid neoplasms. Finally, the development of new molecular technologies such as polymerase chain reaction and pulsed-field gel electrophoresis has provided new tools for the highly sensitive detection of genetic rearrangements in human tumors and will greatly enhance the ability of the pathologist to monitor minimal residual disease and detect early relapse.

Interactions between plasticizers and fatty acid metabolism in the perfused rat liver and in vivo. Inhibition of ketogenesis by 2-ethylhexanol

Rates of ketone body (beta-hydroxybutyrate plus acetoacetate) production by perfused livers from starved rats were decreased about 60% from 39 +/- 2 to 17 +/- 3 mumol/g/hr by 2-ethylhexanol (200 microM), a primary metabolite of the plasticizer diethylhexyl phthalate. Inhibition of ketogenesis by ethylhexanol was dose dependent (half-maximal inhibition occurred with 25 microM) in the presence or absence of 4-methylpyrazole, an inhibitor of alcohol dehydrogenase. Concentrations of beta-hydroxybutyrate relative to acetoacetate (B/A) increased in a step-wise manner from 0.32 to 0.75 in the effluent perfusate when ethylhexanol was infused. In contrast, the B/A ratio decreased in parallel with inhibition of ketone body production when alcohol dehydrogenase was inhibited. Pretreatment of rats with phenobarbital, an inducer of omega and omega-1 hydroxylases, diminished inhibition of ketone body production by low (less than 50 microM) of ethylhexanol. Thus, ethylhexanol is oxidized via phenobarbital-inducible pathways to metabolites which do not inhibit ketogenesis. Studies were conducted to determine the site of inhibition of fatty acid oxidation by ethylhexanol. Rates of ketone body production in the presence of oleate (250 microM), which requires transport of the corresponding CoA compound into mitochondria, were reduced from 80 +/- 6 to 58 +/- 8 mumol/g/hr by ethylhexanol. In contrast, ketone body production from hexanoate, which is activated in the mitochondria, was not affected by ethylhexanol. Basal and oleate-stimulated rates of H2O2 production were not affected by ethylhexanol, indicating that peroxisomal beta-oxidation was not altered by the compound. Based on these data it is concluded that 2-ethylhexanol inhibits beta-oxidation of fatty acids in mitochondria but not in peroxisomes. Treatment of rats with ethylhexanol (0.32 g/kg, i.p.) decreased plasma ketone bodies from 1.6 to 0.8 mM, increased hepatic triglycerides and increased lipid predominantly in periportal regions of the liver lobule. These data indicate that alterations in hepatic fatty acid metabolism in periportal regions of the liver lobule may be early events in peroxisome proliferation.

Activation of glycogen phosphorylase in rat pheochromocytoma PC12 cells and isolated hepatocytes by organophosphates

Several organophosphates including diisopropylfluorophosphonate (DPF) and a variety of compounds used as chemical warfare agents produced dose- and time-dependent increases in phosphorylase-a, the phosphorylated form of glycogen phosphorylase in rat pheochromocytoma cells, PC12, and isolated hepatocytes. Increases in phosphorylase-a did not occur in cells exposed to the carbamates, physostigmine or pyridostigmine, or to O-ethyl S-2-diisopropylaminoethylmethyl-phosphonathiolate (VX), an organophosphate which is protonated at physiological pH. When extracellular pH was increased to pH 8, VX acted like the other organophosphates and increased phosphorylase-a activity. The possibility that organophosphates increase phosphorylase-a in intact cells by releasing Ca2+ from intracellular binding sites is supported by the following findings: organophosphate-induced increases in phosphorylase-a did not correlate with changes in cyclic AMP in the two cell types studied; in PC12 cells, increases in this activity occurred in the absence of extracellular calcium and were not inhibited by the calcium channel blocker, verapamil; fluorescence of the calcium sensitive dye, Quin-2, in PC12 cells preloaded with the acetoxymethyl ester of the dye was increased by soman; finally, addition of the calcium ionophore, A23187, to PC12 cells maintained in calcium-free medium caused sarin-stimulated phosphorylase-a activity to return rapidly to basal levels. Collectively, these data argue strongly that organophosphates increase phosphorylase-a activity in intact cells via a novel mechanism involving release of calcium from intracellular binding sites.

Heterogeneity of the silent gene for plasma cholinesterase. Immunological studies

Rocket immuno-electrophoresis and enzyme-linked immunosorbent assays were used to estimate the amount of cholinesterase present in 29 apparent silent homozygotes. 26 of these samples were segregated into four groups representing zero, very low, low and high levels of immunoreactive protein. These groups may represent the genotypes E1sE1s, E1sE1t, E1tE1t and a new genotype E1xE1x, respectively. The possible genotypes of the remaining 3 individuals are discussed.

Effect of epinephrine on glycogen phosphorylase-alpha in various preparations of rat liver

1. Glycogen phosphorylase-alpha, a commonly used index of cytosolic free calcium, was compared in various preparations of rat liver in the absence and presence of 0.1 microM epinephrine. 2. Total phosphorylase in isolated perfused livers and freshly-isolated hepatocytes were the same as that observed in liver in situ; however, phosphorylase-alpha was 50% higher in perfused liver and 80% higher in hepatocytes than activities measured in situ. Total phosphorylase was reduced approximately 50% in hepatocytes maintained in primary culture for 24 hr. 3. Epinephrine increased phosphorylase-alpha approximately 2-fold in livers perfused for 30 min but only about 20% in hepatocytes incubated for 30 min. After 90 min of perfusion or incubation, epinephrine increased phosphorylase-alpha nearly 4-fold in perfused livers and only 30% in isolated hepatocytes. The results suggest that amounts of free calcium and calcium-dependent coupling of adrenergic receptors to phosphorylase-alpha differ markedly between the intact liver and isolated hepatocytes.

Recognition of the Ek1Ek1 homozygote for plasma cholinesterase

A family is reported in which the propositus was found to be sensitive to suxamethonium. Both parents were heterozygote each having genotype Ea1Ek1. The sibling of the propositus had the most common phenotype as defined by dibucaine, fluoride and RO2 numbers. Genetic analysis, however, indicated that this sibling must be an Ek1Ek1 homozygote.

Adenine nucleotides and carbohydrates in subpopulations of hepatic nodules with normal and compromised microcirculation

Fluorescein-isothiocyanate dextran (FITC-dextran), a dye confined to the vascular space, was infused via the hepatic artery and portal vein into perfused livers from fed rats treated with diethylnitrosamine for 4 to 5 months. Fluorescence due to FITC-dextran was detected with fiberoptic microlight guides placed on surface nodules of about 5 mm in diameter. Nodules were categorized into groups with normal and compromised microcirculation based on their fluorescence following infusion of FITC-dextran. Similar results were obtained when nodules were classified based on reflectance of trypan blue. Despite compromised microcirculation, ATP and ADP levels as well as ATP/ADP ratios were comparable in both groups of nodules; however, AMP was elevated in FITC-dextran-negative nodules (i.e., those with compromised microcirculation). Nodules with compromised microcirculation also contained higher glucose and lactate levels than nodules that were well perfused; however, glycogen was five times lower than in FITC-dextran-positive nodules. Fasting reduced ATP/ADP ratios in poorly perfused nodules in comparison to well-perfused nodules. In perfused livers from fed rats where glycogen was high, however, ATP/ADP ratios and rates of ATP depletion during ischemia were the same in well-perfused and poorly perfused nodules. Products of glycogen breakdown (e.g., glucose and lactate) were elevated in nodules from livers of fed but not fasted rats. The results indicate that alteration of perfusion of hepatic nodules does not change ATP levels nor the capacity of nodules to utilize high energy phosphate during anoxia. Thus, near normal energy status is maintained from glycogen metabolism in poorly perfused nodules via glycolysis. Since basal ATP content and utilization is comparable in well and poorly perfused nodules, compromised energy status is unlikely to explain selection of nodules that regress to near normal hepatocytes.

Primary anorectal malignant melanoma. A case report

A case of primary anorectal malignant melanoma in a 66-year-old lady is presented and the clinical, radiological and surgical features reviewed. The presenting symptoms similar to the more commonly encountered haemorrhoids led to a delay in the eventual diagnosis and treatment, resulting in limited post-operative survival. The relevant literature is reviewed and an emphasis made on the accurate histological diagnosis of anorectal growths.

A comparison of glutathione reductase and glutathione peroxidase activities in patients with rheumatoid arthritis and healthy adults

A 30% increase in erythrocyte glutathione peroxidase (GP) activity was found in patients with rheumatoid arthritis when compared with healthy controls (p = 0.001) whereas the increase in glutathione reductase (GR) was statistically insignificant. No correlation was found between the activities of the enzymes and the erythrocyte sedimentation rate (ESR). The enzyme activities were independent of age, sex, or type of drug treatment of the patients. A possible interpretation of the results is presented.

Inheritance of low plasma cholinesterase activity in two families with a history of suxamethonium sensitivity

An hypothesis advanced in 1970 concerning family inheritance of low enzymic activities of plasma cholinesterase has been substantiated. The recognition of three E1kE1s genotypes is reported in this family after investigation of a new generation. A second family with similar genetic characteristics is described.

Segregation of the E1j gene for plasma cholinesterase in family studies

Four families are reported in which the E1j gene is segregating. Two E1jE1k and one E1jE1f genotypes have been recognised by genetic analysis. The biochemical characteristics of several E1j genotypes are presented.

Family studies of the E1kE1s genotype for plasma cholinesterase

Six individuals in three families with a history of suxamethonium sensitivity have been found to have genotype E1kE1s. The biochemical data for the recognition of this genotype have been analysed and the mean values compared with similar parameters for the usual phenotype. Individuals with genotype E1kE1s will be sensitive to suxamethonium.

Some observations of levels of plasma cholinesterase activity within an obstetric population

An account of plasma cholinesterase activity in samples of maternal and cord blood is presented. It is confirmed that plasma exchange markedly reduces the level of activity in maternal blood, and that the level is further reduced during the first 3-4 postnatal days. A particularly marked decrease was found in those cases in which spontaneous mid-trimester abortion occurred. The level of activity in maternal blood (excluding mothers subjected to plasma exchange) at the time of delivery, was higher than that in cord blood in 61% of cases. In 23% of cases the level of activity was appreciably (0.05 units) higher in cord blood, and two-thirds of these cord samples contained the E2+ electrophoretic variant of plasma cholinesterase. The mean levels of activity in maternal and cord blood of Rhesus negative patients were significantly lower than those among Rhesus positive patients but there was no such distinction between Rhesus positive and Rhesus negative males and nonpregnant females. We encountered an incidence of 1:228 abnormal phenotypes in a series of 1593 mothers who underwent Caesarean section under a technique of general anaesthesia which included a suxamethonium infusion. However, probably only two of the seven patients would definitely be sensitive when not pregnant.

Recognition of two new phenotypes segregating the E1k allele for plasma cholinesterase

The first identification of the cholinesterase variants E1kE1k and E1kE1s is reported from a family study. The evidence is based on the biochemical parameters of enzymic activity, and dibucaine, fluoride and RO2 numbers. Two individuals appear to be homozygotes E1kE1k and two are heterozygotes E1kE1s with family evidence supportive of these genotypes. The heterozygotes E1kE1s will be sensitive to suxamethonium.

Contribution of tryptophan residues to the combining site of a monoclonal anti dinitrophenyl spin-label antibody

Two Fab fragments of the monoclonal anti dinitrophenyl (DNP) spin-label antibody AN02 were prepared by recombination of specifically deuterated heavy and light chains. In the recombinant H(I)L(II) all the tyrosines and phenylalanines were perdeuterated as were the tryptophan residues of the heavy chain. In the recombinant H(II)L(I) all the tyrosines and phenylalanines were perdeuterated as were the tryptophan residues of the light chain. Saturation of three resonances of H(I)L(II), assigned to tryptophan protons of the light chain, resulted in magnetization transfer to the aromatic proton at position 6 of the DNP ring and to the CH2 protons of the glycines linked to the DNP in a diamagnetic hapten (DNP-DG). Saturation of three resonances of H(II)L(I) assigned to tryptophan protons of the heavy chain resulted in magnetization transfer to the CH2 protons of the glycines in DNP-DG. From the dependence of the magnetization transfer on the irradiation time, the cross relaxation rates between the involved protons were estimated. The inferred distances between these protons of the hapten and certain tryptophan protons are 3-4 A. It is concluded that in the combining site of AN02 there is one tryptophan from the light chain and one tryptophan from the heavy chain that are very near the hapten. When all tyrosines and phenylalanines were perdeuterated and all tryptophan aromatic protons were deuterated except for the protons at positions 2 and 5, titration of the Fab fragments with variable amounts of paramagnetic hapten showed that one proton from the light chain tryptophan is near (less than 7 A) the unpaired electron and that three other protons are significantly closer than 15 A.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of suxamethonium sensitivity following termination of pregnancy

The cholinesterase genotypes in the majority (25/35) of patients with suxamethonium sensitivity following termination of pregnancy are heterozygotes with an E1a gene. Twelve of these patients have the genotype E1uE1a. The reported duration of apnoea is minimal in the heterozygotes lacking the E1a gene (about 5-10 min) and maximal in the homozygotes E1aE1a (about 35 min). With few exceptions, the heterozygotes having an E1a gene are apnoeic for 10-15 min. The apparent low frequency of suxamethonium in these patients is discussed.

Phenotyping of individuals sensitive to suxamethonium. The Cholinesterase Research Unit at the Royal Postgraduate Medical School

Four hundred and thirty blood samples from suxamethonium-sensitive individuals have been phenotyped by the Cholinesterase Research Unit following its transfer from Exeter to the Hammersmith Hospital. The distribution of genotypes has been shown to be similar to that found in Exeter. Screening for the Elk and Elj genes has not yielded any major differences in the gene frequencies of sensitive individuals, even during pregnancy. The uneven sex distribution of the patients, as well as other unusual points that have arisen, are discussed. A new gene for the biosynthesis of cholinesterase has probably been identified.

E1h, a new allele at cholinesterase locus 1

Unusual inhibition characteristics in two unrelated suxamethonium-sensitive individuals were indicative of a new allele, E1h, segregating with the E1a gene. Family studies substantiate this hypothesis and three new genotypes are recognised.

Recognition of the E1kE1f cholinesterase genotype in a family segregating three rare genes, E1k, E1f and E1a

The first identification of the cholinesterase variant E1kE1f is reported from a family study. The evidence is based on the determination of enzymic activity, dibucaine, fluoride and RO2 numbers. Three individuals appear to have this genotype, and family evidence is not at variance with our conclusions. All three individuals will be sensitive to suxamethonium.