Effect of serotonergic, corticostriatal and kainic acid lesions on the dopaminergic neurotoxicity of 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) in mice

In mice, prior destruction of striatal 5-hydroxytryptamine (5-HT) neurons by intrastriatal or intraventricular injections of 5,7-dihydroxytryptamine did not abolish or attenuate DA depletions produced in striatum by 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP). This suggests that although they contain monoamine oxidase type B, the oxidative conversion of MPTP to 1-methyl-4-phenyl-pyridinium ion (MPP+) does not take place in 5-HT neurons. Likewise, decortication and kainic acid lesions did not prevent or enhance striatal MPTP-induced DA decrements suggesting that corticostriatal projections and striatal neurons are not involved in the mechanisms of MPTP neurotoxicity.

Chester porphyria: biochemical studies of a new form of acute porphyria

A previously unrecognised form of acute porphyria has been identified in a large family in Chester, UK. Patients presented with attacks of neurovisceral dysfunction and none had experienced cutaneous photosensitivity. Biochemically, the excretion pattern of haem precursors varied between individuals; some had a pattern typical of acute intermittent porphyria, others showed that of variegate porphyria, and some had an intermediate pattern. Studies of the enzymes of haem biosynthesis in peripheral blood cells showed a dual enzyme deficiency, with reduced activity of both porphobilinogen deaminase, as seen in acute intermittent porphyria, and protoporphyrinogen oxidase, as seen in variegate porphyria. The genetic basis of this dual form of acute porphyria and its relation to the other acute porphyrias are not clear.

Autonomic neuropathy in acute intermittent porphyria

Autonomic function was assessed in subjects with acute intermittent porphyria and age- and sex-matched controls using five different bedside tests of cardiovascular reflexes. During the acute attack both parasympathetic and sympathetic tests were impaired, but subsequently improved during remission. Early parasympathetic dysfunction was also detected during remission and in latent asymptomatic acute intermittent porphyria.

Altered HDL subclasses in endogenous hypertriglyceridemia are not affected by weight reduction

Reduction of body weight is commonly used to decrease the plasma lipids of patients with primary endogenous hypertriglyceridemia, but the effects of stabilized weight reduction on lipoprotein compositions and distribution are not well known. Since lipoprotein structures are perhaps as important in normal and abnormal metabolism and atherogenesis as are the levels of lipoproteins, we examined the effects of weight loss on the plasma concentrations, compositions, and ultracentrifugal flotation properties of plasma lipoproteins. Nine patients (eight males, one female) with endogenous hypertriglyceridemia and low high-density lipoprotein (HDL)-cholesterol levels who were approximately 130% of ideal body weight were studied during two dietary periods (basal and low weight). Subjects consumed an isocaloric diet for 5 weeks consisting of approximately 15% protein, approximately 45% carbohydrate, approximately 40% fat, approximately 500 mg/d cholesterol, P/S ratio 0.43 (basal), followed by a hypocaloric diet of the same composition, which was eaten for 16 to 52 weeks, until the desired weight was lost (9.6 +/- 3.6 kg). Then patients continued to eat a diet of the same composition lower in calories but sufficient in quantity to maintain their new lower body weights for the final 5 weeks (low-weight period). The last weeks of the basal and the low-weight periods were spent in a metabolic ward. Thus, high and low body weights were known to be stable for at least 5 weeks. Fasting (12 to 14 hours) plasma total triglycerides decreased in all patients (from 328 +/- 204 mg/dL at basal to 185 +/- 77 mg/dL at low weight, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

"Natural termination": some comments on ending analysis without setting a date

This paper is a re-examination of the rule of date setting in termination. It reviews the literature and presents an analytic case which was terminated in what the patient called a "natural" manner, i.e., without the setting of a date. Some ideas about the nature of the rules used in organizing analysis are discussed.

Neurotoxic action of lead: effect on tetrahydrobiopterin metabolism in the rat

The effects of lead, a known neurotoxin on the metabolism of a vital tetrahydrobiopterin cofactor for the hydroxylation enzymes tyrosine hydroxylase, phenylalanine hydroxylase and tryptophan hydroxylase, have been investigated. Reduced availability of this pteridine has the potential to reduce the level of the neurotransmitters noradrenaline, adrenaline and 5-hydroxytryptophan in the brain. Using the rat as a model, increases in tetrahydrobiopterin concentration and in the activity of dihydropteridine reductase, an enzyme involved in tetrahydrobiopterin metabolism, were observed after exposure to lead via the drinking water. Possible explanations for this increased level of tetrahydrobiopterin relate to alterations in the balance between synthesis and salvage of this co-factor.

Cardiovascular and metabolic responses to submaximal exercise in hemodialysis patients

Eight chronic hemodialysis (cHD) patients and six healthy sedentary controls (C) were exercised for 60 minutes at 52 +/- 8% (cHD patients) and 48 +/- 4% (C) of their maximal oxygen consumption levels. Plasma lactate levels at rest and during exercise were comparable in both groups. Respiratory exchange ratios were lower in cHD patients, but they increased during exercise to levels comparable to those of the C group. Despite comparable heart rates at rest, exercise of similar intensity led to lower heart rates at 30 and 60 minutes in cHD patients compared to C (P less than 0.05). The cHD patients had higher systolic and mean arterial pressures at rest than did C (P less than 0.05), but during exercise the increments in systolic and mean blood pressures were lower in cHD patients than they were in C (P less than 0.05). In spite of these blunted cardiovascular responses, plasma catecholamines increased during exercise in both groups. Plasma glucose levels were similar in both groups during exercise in spite of significantly higher plasma levels of insulin and glucagon in cHD patients throughout the exercise session (P less than 0.01). These data demonstrate that chronic cHD patients can exercise at a modest intensity for a prolonged period of time without untoward cardiovascular or metabolic responses. Their poor exercise response does not appear to be related to an inadequate activation of the sympathoadrenal system.

A new immunologic test for CNS cysticercosis

A new radioimmunoassay for cerebral cysticercosis was studied in 70 patients. The assay showed nearly 100% sensitivity for ventricular cysts or meningitis, 86% sensitivity for multiple parenchymal cysts, and a false-positive rate of 7%. Both serum and CSF antibody levels were useful diagnostically, and the contribution of both improved accuracy. In some patients, there was endogenous CNS production of IgG against the cysticercus antigen, which leads to elevated CSF levels and normal serum levels. Patients with high CSF total IgG levels may show false-positive CSF antibody elevation with normal serum levels.