Nicotine and amyloid formation.

The major protein constituents of amyloid deposits in Alzheimer's disease (AD) are the 40-residue beta-amyloid (Abeta) (1-40) peptide and the 42-residue Abeta(1-42) peptide. The Abeta(1-42) is more pathogenic and produced in greater quantities in familial forms of AD. A major goal of research is to uncover a suitable inhibitor that either slows down or inhibits Abeta formation (beta-amyloidosis). During beta-amyloidosis, structural changes associated with the conversion of monomeric Abeta peptide building blocks into the aggregated fibrillar beta-sheet structures occur (alpha-helix-->beta-sheet or random, extended chain-->beta-sheet). In previous work, we and others established that nicotine, a major component of cigarette smoke, inhibits beta-amyloidosis of the Abeta(1-42), which may result from nicotine binding to the alpha-helical structure. These conclusions were based on solution nuclear magnetic resonance (NMR) spectroscopic studies with the nonnative 28-residue Abeta(1-28). This information suggests that, when administered therapeutically to AD patients, nicotine may not only affect cholinergic activation, but could also conceivably alter amyloid deposition. In this report, NMR studies were augmented with the naturally occurring Abeta(1-42), under conditions where the peptide folds into a predominantly alpha-helical or random, extended chain structure. The major result is that nicotine shows only modest binding to these conformations, indicating that the nicotine inhibition to beta-amyloidosis probably results from binding to a small, soluble beta-sheet aggregate that is NMR invisible.

Metabolic responses to intracerebroventricular leptin and restricted feeding.

Leptin is a hormone secreted by adipocytes, which plays an important role in the control of food intake and metabolic processes. In the current study, a dose-dependent relationship was shown between a bolus intracerebroventricular rat recombinant leptin administration and reductions in food intake and body weight in Sprague-Dawley rats. During the 24 h postinjection period, food intake was decreased by 24, 26, and 52% with 0.625, 2.5, and 10 microg of leptin, respectively. Body weight was reduced by 2, 3, and 5% at 24 h after leptin administration at the doses of 0.156, 2.5, and 10 microg, respectively. Furthermore, indirect calorimetry demonstrated that five daily i.c.v. injections of leptin resulted in an increase in heat production per unit of metabolic body size and fat oxidation by approximately 10 and 48%, respectively. In contrast, food-restricted rats that consumed the equivalent amount of food as leptin-treated rats for 5 days decreased their energy expenditure by 10%. Food restriction was found to decrease respiratory quotient in a similar pattern as the leptin administration. When ad lib feeding was resumed, food-restricted rats quickly recovered their normal food intakes, body weights, and metabolism. Conversely, leptin treatment has prolonged effects on body weight resulting from different metabolic responses than food restriction. Leptin not only suppresses food intake, but also enhances energy expenditure to reduce fat depots.

Patient satisfaction with a direct access vasectomy service.

This study of patient satisfaction with a direct access vasectomy service was carried out by questionnaire offered to 100 patients attending a day surgery unit for vasectomy. Seventy eight patients responded and there was overall satisfaction with the service, with 72 patients (96 per cent of respondents) describing it as excellent or good. The commonest criticism expressed by respondents concerned long waiting times in the unit before surgery on the day of operation. Vasectomy is a straightforward and minor surgical procedure which suits a direct access service.

PIP: Findings are presented from a study of patient satisfaction with a direct access vasectomy service. A questionnaire was offered to 100 consecutive patients attending a day surgery unit for vasectomy. Potential respondents were asked to complete the questionnaire a fortnight after the operation and to return it in the self-addressed envelope provided. 78 patients responded, voicing their overall satisfaction with the service. 72 patients described the service as either excellent or good. 6% of the men sought postoperative general practitioner/practice nurse consultation; 3 patients for advice on scrotal contusion and pain and the rest for medical certificates for absence from work. 19 patients made 20 criticisms of the service. Respondents' most common criticism was of long waiting times in the unit before surgery on the day of the operation. Vasectomy is a straightforward and minor surgical procedure which suits a direct access service.

Electron paramagnetic resonance (EPR) studies on hydrogenase-1 (HYD1) purified from a mutant strain (AP6) of Escherichia coli enhanced in HYD1.

Hydrogenase-1 (HYD1), overexpressed by twofold, has been purified to homogeneity and to a high specific activity from a mutant strain (AP6) of Escherichia coli which lacks hydrogenase-2. Plasma emission spectroscopy indicated that 0.93 atom of nickel and 11.4 iron atoms were present in HYD1. EPR studies on the as isolated HYD1 detected a complex 3Fe-4S signal and a Ni(III) species. Reduction with hydrogen gas caused disappearance of both the 3Fe-4S cluster and initial Ni(III) signals. At the same time the EPR signature (small g = 2.19 signal) of the activated hydrogenase appeared. The detection of a 4Fe-4S cluster signal was noted. Reduction of HYD1 with sodium dithionite caused all nickel signals to disappear. The 4Fe-4S complex intensity was slightly increased. The EPR responses in the three oxidation-reduction states are consistent with other known (NiFe)-hydrogenases.

Cloning, sequencing and overexpression of the Desulfovibrio gigas ferredoxin gene in E. coli.

We have cloned the gene encoding Desulfovibrio gigas ferredoxin using a photodigoxigenin-labelled probe synthesized with the polymerase chain reaction. The DNA sequence of the gene predicts a polypeptide of 58 residues after removal of the initial formyl methionine (polypeptide M(r) = 6,276). The ferredoxin gene was expressed in aerobically grown E. coli behind the lac promoter of pUC18 resulting in a high level of ferredoxin expression which comprises about 10% of the total cell protein. EPR analysis of recombinant ferredoxin revealed the presence of a [3Fe-4S] cluster which is characteristic of native D. gigas ferredoxin II.

Cloning, sequencing, and mutational analysis of the hyb operon encoding Escherichia coli hydrogenase 2.

The genes encoding the two structural subunits of Escherichia coli hydrogenase 2 (HYD2) have been cloned and sequenced. They occur in an operon (hyb) which contains seven open reading frames. An hyb deletion mutant (strain AP3) failed to grown on dihydrogen-fumarate medium and also produced very low levels of HYD1. All seven open reading frames are required for restoration of wild-type levels of active HYD2 in AP3. The hyb operon was mapped at 65 min on the E. coli chromosome.

Community-acquired bacteraemic Acinetobacter pneumonia with survival.

A 65 year old man was admitted with segmental consolidation of the left upper lobe after having stayed in a hotel for 2 days. He deteriorated rapidly on conventional antibiotic therapy and required ventilatory support. Acinetobacter calcoaceticus var. anitratus was grown from the sputum and blood cultures, which was treated with a combination of anti-pseudomonal agent, aminoglycoside and cotrimoxazole. He made a slow but remarkable recovery from the pneumonia. Acinetobacter is a rare potentially fatal cause of community-acquired pneumonia.

Carboxy-terminal processing of the large subunit of [NiFe] hydrogenases.

Two electrophoretic forms of the large subunit of the soluble periplasmic [NiFe] hydrogenase from Desulfovibrio gigas have been detected by Western analysis. The faster moving form co-migrates with the large subunit from purified, active enzyme. Amino acid sequence and composition of the C-terminal tryptic peptide of the large subunit from purified hydrogenase revealed that it is 15 amino acids shorter than that predicted by the nucleotide sequence. Processing of the nascent large subunit occurs by C-terminal cleavage between His536 and Val537, residues which are highly conserved among [NiFe] hydrogenases. Mutagenesis of the analogous residues, His582 and Val583, in the E. coli hydrogenase-1 (HYD1) large subunit resulted in significant decrease in processing and HYD1 activity.

Accumulation of lipid peroxidation products in human myotonic dystrophic muscle.

The possibility of oxygen radical-induced injury contributing to the pathogenesis of muscle disorders was studied. Significant increases in fluorescent lipid peroxidation products was found in the muscle samples of myotonic dystrophy (MyD) patients as compared to controls as well as patients with Duchenne Muscular dystrophy (DMD), Amyotrophic Lateral Sclerosis (ALS), Polymyositis and Limb Girdle Dystrophy (LGD). The results demonstrate the possibility that in MyD the primary genetic disorder leads to the rapid generation of oxygen radicals, tissue depletion of antioxidants followed by peroxidation of membrane lipids, impaired calcium homeostasis and finally atrophy of the muscle.

Elevated levels of prostaglandins E2 and F2( in human neuromuscular disorders.

Prostaglandins (Pgs), especially PGE2 and F2( ( have been implicated in variety of pathological processes including proteolysis of normal and dystrophic muscle. Using a modified radioimmunoassay which did not involve extraction in organic solvents and purification, thus eliminating acid artifacts, we measured PGE2 and F2( levels in patients with myotonic (MyD), Duchenne (DMD), and limb girdle (LGD) dystrophies and amyotrophic lateral sclerosis (ALS). There was a significant increase in PGE2 and PGF2 in the muscle samples of all the disorders studied as compared to normal controls. It is proposed that increased influx of calcium activated phospholipase A2 (PLA2) leading to the accumulation of arachidonic acid and hence prostaglandins. It appears that the relative increases in PGE2 and PGF2( which are implicated in protein degradation and synthesis respectively in vitro, may reflect the extent of degeneration and regeneration occurring in the diseased muscles.

Abnormal distribution of desmin and vimentin in myofibers in adult onset myotubular myopathy.

We report, for the first time, muscle immunocytochemical studies in sporadic, adult onset myotubular myopathy (SAOMM), which show intramyofibrillar central, perinuclear desmin and vimentin. This pattern was absent in a normal control and in myofibers with increased internal nuclei associated with denervation and myotonic muscular dystrophy (MyD). These findings resemble those reported in 8- to 15-week-old human fetal myotubes and myofibers of infantile MM, implying a possible regression of intermediate filaments of adult myofibers to an early developmental phase in SAOMM.

Calcium, calmodulin and 3',5'-cyclic nucleotide phosphodiesterase activity in human muscular disorders.

3',5'-Cyclic nucleotide phosphodiesterase (PDE) is known to play an important role in the regulation of cyclic nucleotide levels in various tissues including the muscle. Previous studies have estimated the level of this enzyme in several neuromuscular disorders but the results have been variable. Moreover, there was no attempt made to correlate the enzyme levels with the levels of calcium and calmodulin, both of which regulate diverse biological processes including muscle contraction. In the present study we have estimated phosphodiesterase in the muscle of normal controls as well as patients with myotonic (MyD) and Duchenne muscular dystrophy (DMD) and amyotrophic lateral sclerosis (ALS). PDE was found to be increased significantly in all of the diseased muscles as compared to controls (P less than 0.01). But the increase could be coupled with an increase in calcium and calmodulin only in Duchenne dystrophic muscle.