Biosynthesis of biopterin in Ascaris lumbricoides suum

In in vivo experiments, radioactivity from [U-14C]GTP was incorporated into biopterin, and, in fact, all carbon atoms of biopterin synthesized in Ascaris lumbricoides suum originated from GTP. Biopterin was also biosynthesized in homogenates of tissue fluid and muscles of Ascaris lumbricoides suum. The enzyme which catalyzes sepiapterin synthesis from D-erythro-7,8-dihydroneopterin-3'-phosphate was found in A. lumbricoides suum extracts and extracted in the 0--30% (NH4)2SO4 fraction from a 40 000 x g supernatant. The enzyme was purified by Sephadex G-200 column and DEAE-cellulose column chromatography. It is suggested that sepiapterin could be an intermediate compound in biopterin biosynthesis.

Change of polyamine content in mouse skin by leupeptin, a protease inhibitor, during early stage of tumorigenesis

The effect of a microbial protease inhibitor, leupeptin, on the content of polyamine in the mouse skin was examined during the early stage of tumorigenesis induced by a single application of 7,12-dimethylbenz[a]anthracene (DMBA) and repeated application of croton oil thereafter. Polyamine content in the skin was measured at 3, 5, 7, and 9 weeks during tumorigenesis. The mice with no visible tumor were selected for measurement of polyamine content at 9 weeks. Mice were left untreated for at least 1 week before measurement of polyamine. Polyamine in the skin was extracted with ice-cold 0.4N HClO4 and separated into putrescine, spermidine, and spermine fractions through CM-cellulose column. Polyamine concentration was determined by fluorometry with fluorescamine. Group A mice painted with croton oil 3 times a week did not develop tumors. Group B mice painted with a single DMBA developed skin tumors, and group C mice painted with a single DMBA and croton oil 3 times a week showed higher development of skin tumors than group B. Group D mice treated as group C and then painted with leupeptin about 2 hr after croton oil treatment. Animals in groups B, C, and D had higher spermidine content as group A at 3 and 5 weeks. Content of spermidine in group B decreased at 7 and 9 weeks compared with group C which had a high content throughout the time tested. Leupeptin treatment in group D inhibited spermidine content in the skin after 7 weeks without affecting until 5 weeks.

Is normoreninemic essential hypertension caused by disordered central dopaminergic regulation?

Some investigators have reported that plasma prolactin levels are elevated in hypertensive men and that both their hyperprolactinemia and hypertension were controlled by bromocriptine, a dopamine agonist. They concluded that reduced central dopaminergic activity may be a factor in maintaining essential hypertension. We examined the serum prolactin and thyrotropin (TSH) responses to thyrotropin releasing hormone (TRH), metoclopramide (a dopamine antagonist) and bromocriptine in 10 normal and 10 hypertensive normoreninemic men. TRH caused significant increase of both prolactin and TSH and metoclopramide caused significant increase of prolactin in both normals and hypertensives. Bromocriptine suppressed prolactin and TSH significantly in both groups. There were no significant differences in prolactin and TSH levels between the normal and hypertensive groups before or during the tests. These results provide no support for the hypothesis that alterations in the activity of central dopaminergic neurons are involved in the maintenance of the elevated blood pressure of normoreninemic men with essential hypertension.

Antagonistic action of alpha- and beta-agonists on the bullfrog atrium

Action of alpha- and beta-agonists on the membrane potential, current and tension components on the bullfrog atrial muscle were studied by means of the single or double sucrose-gap technique. Isoproterenol (10(-9)-10(-5) M) as well as adrenaline (10(-7)-10(-4) M) produced a dose-dependent positive inotropic effect, while methoxamine (10(-8)-10(-4) M) and phenylephrine (10(-8)-10(-3) M) with propranolol (10(-6) M) elicited a negative inotropic effect. The positive inotropic effect was accompanied by slight hyperpolarization and marked increase of over-shoot and plateau level of action potential, and the negative inotropic effect, by opposite changes. Under voltage clamp, isoproterenol and adrenaline produced enhancement of slow inward current (Is), delayed outward current (Ix) and Is-dependent phasic tension, while Is-independent tonic tension was inhibited. Contrarily, methoxamine and phenylephrine depressed these currents and elicited beta-antagonistic inotropic actions, especially when isoproterenol was present. Specific feature of alpha-agonist action in the presence of isoproterenol was an inward shift of the semi-steady I-V relationship. It is thus suggested that, in the bullfrog atrium, alpha-agonists produce a strong beta-receptor blocking action and an inward shift of the background current. A possible relationship between the latter effect and inhibition of the Na-K pump is also suggested.

Immunological abnormalities of aging: an analysis of T lymphocyte subpopulations of Werner's syndrome

Two T lymphocyte-specific antisera, i.e. naturally-occurring auto-antibody to T cells of systemic lupus erythematosus patients (natural T cell toxic autoantibody) and heterologous antiserum against human brain tissue (antibrain-associated T-cell antigen), were used to detect cell surface antigens of human peripheral T lymphocytes. Nylon column-purified T cells from normal aged individuals and patients with Werner's syndrome (a premature aging syndrome) were reacted with these auto- and heterologous antibodies followed by staining with appropriate fluorescence reagents. The cells were subjected to the automated analysis with fluorescence-activated cell sorter. Fluorescence profiles to T cells of both aged individuals of over 90 yr and Werner's syndrome showed a very similar pattern, with a drastic decrease in the population that had high fluorescence intensity stained with either antiserum accompanied by the relative increase in the cell population that had low fluorescence intensity. Natural T cell toxic autoantibody comparable to that detected in systemic lupus erythematosus patients was found in the serum of six out of seven patients with Werner's syndrome, whereas normal aged individuals produced no such an autoantibody. The results suggest that Werner's syndrome has a change in the lymphocyte population very similar to old individuals, and that such a change is caused by the production of autoantibodies reactive to T lymphocytes.

Electrophysiological actions of mexiletine (Kö1173) on canine Purkinje fibres and ventricular muscle

1 The effects of mexiletine (Kö1173) were investigated in canine isolated cardiac Purkinje fibres and ventricular muscle with microelectrodes. Some Purkinje fibres were depolarized by mechanical stretch to induce spontaneous activity with slow upstroke velocity. The preparations were stimulated at rates of 1, 2, 3 and 4 Hz. The drug concentrations tested were 0.4, 2 and 10 mug/ml in Tyrode solution (KCl = 5.4 mM).2 The ;therapeutic' drug concentration (2 mug/ml) shortened action potential duration and effective refractory period of Purkinje fibres, the effect being pronounced at lower stimulation rates. In ventricular fibres, action potential duration changes were not consistent while the effective refractory period was prolonged.3 In depolarized Purkinje fibres showing automatic activity, the drug (0.4 or 2 mug/ml) depressed phase 4 depolarization and reduced the firing rate without changing maximum diastolic potential. However, when depolarized Purkinje fibres were electrically driven at a constant rate, the maximum diastolic potential became more negative with a concomitant decrease of pacemaker slope and increase of maximum rate of rise (V(max)) of action potentials.4 Moderate (2 mug/ml) to high (10 mug/ml) concentrations of the drug depressed V(max) in Purkinje fibres stimulated at 2 Hz by 12 and 42% respectively and depressed ;membrane responsiveness'. The decrease in V(max) depended upon the stimulation rate, being minimum at the lowest (1 Hz) and maximum at the highest (4 Hz) stimulation rate.5 The drug (2 mug/ml) improved V(max) of the earliest propagated premature action potentials by shifting the takeoff potential to more negative levels in both Purkinje and ventricular fibres.6 Membrane conductance in fibres mounted in a single sucrose gap chamber was increased by the drug (2 mug/ml) in both fibre types in normal and in Na(+)-deficient solutions. This increase was attributed to an increase in membrane K(+) permeability produced by the drug.7 All these effects are similar to those of lignocaine, diphenylhydantoin or aprindine, and can explain the antiarrhythmic action of mexiletine.

Evidence for a new lethal gene causing cardiomyopathy in Japanese black calves

Sudden death with severe dyspnea in new-born or infant calves confined to a family of Japanese black cattle was studied. Neither environmental nor bacteriological factors seemed to be involved in the etiology of the disease. Histopathological examination revealed focal degeneration and necrosis of the muscle fibers in the myocardium, to which a diagnosis of idiopathic cardiomyopathy was proposed. The pedigree and mating type analyses suggested that a new autosomal recessive lethal gene was responsible for the syndrome. Rates of incidence of the affected calves in five sire families were tested for an expectation of 12.5 percent incidence by the chi-square method.

Abnormalities of erythrocyte membranes in biliary atresia: ultrastructure and lipid composition

Biochemical and ultrastructural studies of red blood cell membranes from seven patients with congenital biliary atresia have been performed. Scanning electron microscopic observations revealed that more than half of these cells were of abnormal shapes, such as target, spur and cup-formed cells. By freeze-fracture electron microscopy, membrane particle-free smooth areas were noted in the fracture faces. In addition, the number of membrane-associated particles was 20% less than those in control subjects. The lipid analysis of red blood cells showed a significant increase in phospholipid and a marked increase in cholesterol content. The increase of phospholipid content was primarily caused by the increase of lecithin. The acyl chain analysis of erythrocyte lecithin demonstrated an increase in palmitic, palmitoleic and oleic acid, and a decrease in stearic and linoleic acid. These observations are similar to those of acquired biliary obstruction. The fluidity of erythrocyte membrane lipid, studied by a fluorescence technique using fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH), was found to be less in an individual with congenital biliary atresia than in the control subject.

Effects of anti-inflammatory drugs on platelet aggregation in rabbits

Effects of non-steroidal anti-inflammatory drugs (aspirin, indimethacin, flufenamic acid, tiaramide and HG-70) on rabbit platelet aggregation were studied using Evans aggoregometer and a modified form of Chandler's loop method. Tiaramide in 10(-4) and 10(-5)M inhibited effectively the aggregation caused by ADP in the optical density method and accelerated the restoration of the time course of disaggregation in the loop method. The other 4 drugs were ineffective. In collagen-induced aggregation all 5 drugs inhibited the aggregation. Among them tiaramide was most potent. Only tiaramide prolonged the time taken to induce snow storm and aggregates in the loop method.

Histopathologic features of the skin of hairless newborn pigs with goiter

The skin of 15 hairless newborn pigs with parenchymatous goiter was studied histopathologically. Most of the lesions were in the hair follicles; follicles were scarce and reduced in size, contained slender hairs, and revealed a shortage of penetration into the hypodermis. Hair follicles in the immature stages, hair pegs, and germs also were recognized, with the thin epidermis lacking in keratinization. It was felt that these changes resulted from a retardation of cellular differentiation of the germinal layer. In view of these findings, skin lesions were regarded as hypoplasia of hair.

Interaction between caffeine and adenosine on the membrane current and tension component in the bullfrog atrial muscle

Antagonistic action of caffeine and adenosine were studied at the membrane current and tension component levels in myocardium of the bullfrog atrium, mainly under voltage clamp using the double sucrose-gap method. Caffeine (1-5 mM) produced marked augmentation of the phasic and tonic tensions as well as slow inward current (Is). At higher concentrations it elicited an increase of the delayed outward current (Ix). The augmentation of Is was principally due to increase of the limiting conductance (gs), while the activation and inactivation variables (dinfinity, finfinity) were not changed significantly. The dose-tension response curve for caffeine, which appeared sigmoidal, was notably lowered in the presence of adenosine (1-3 mM), indicating a competitive type of inhibition. Adenosine, in the presence of caffeine, exerted a narcotic-like action by inhibiting all of the membrane currents (INaf, Is, Ix and background inward current, Ib) and tension components (ICa-dependent and independent tensions). The inhibition of Is was due to a decrease of gs and no appreciable change was observed in dinfinity and finfinity. These results suggest that adenosine has a strong stabilizing action on the myocardium, especially when the heart muscle activity is accelerated by increased cyclic AMP.