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F Martin

Publications and source records attributed to F Martin.

At least 235 records · Page 13Linked to original sources
PubMed1995

Divergent evolution of a beta/alpha-barrel subclass: detection of numerous phosphate-binding sites by motif search.

Study of the most conserved region in many beta/alpha-barrels, the phosphate-binding site, revealed a sequence motif in a few beta/alpha-barrels with known tertiary structure, namely glycolate oxidase (GOX), cytochrome b2 (Cyb2), tryptophan synthase alpha subunit (TrpA), and the indoleglycerolphosphate synthase (TrpC). Database searches identified this motif in numerous other enzyme families: (1) IMP dehydrogenase (IMPDH) and GMP reductase (GuaC); (2) phosphoribosylformimino-5-aminoimidazol carboxamide ribotide isomerase (HisA) and the cyclase-producing D-erythro-imidazole-glycerolphosphate (HisF) of the histidine biosynthetic pathway; (3) dihydroorotate dehydrogenase (PyrD); (4) glutamate synthase (GltB); (5) ThiE and ThiG involved in the biosynthesis of thiamine as well as related proteins; (6) an uncharacterized open reading frame from Erwinia herbicola; and (7) a glycerol uptake operon antiterminator regulatory protein (GlpP). Secondary structure predictions of the different families mentioned above revealed an alternating order of beta-strands and alpha-helices in agreement with a beta/alpha-barrel-like topology. The putative phosphate-binding site is always found near the C-terminus of the enzymes, which are all at least about 200 amino acids long. This is compatible with its assumed location between strand 7 and helix 8. The identification of a significant motif in functionally diverse enzymes suggests a divergent evolution of at least a considerable fraction of beta/alpha-barrels. In addition to the known accumulation of beta/alpha-barrels in the tryptophan biosynthetic pathway, we observe clusters of these enzymes in histidine biosynthesis, purine metabolism, and apparently also in thiamine biosynthesis. The substrates are mostly heterocyclic compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Oxidoreductases↗
PubMed1995

The class II aminoacyl-tRNA synthetases and their active site: evolutionary conservation of an ATP binding site.

Previous sequence analyses have suggested the existence of two distinct classes of aminoacyl-tRNA synthetase. The partition was established on the basis of exclusive sets of sequence motifs (Eriani et al. [1990] Nature 347:203-306). X-ray studies have now well defined the structural basis of the two classes: the class I enzymes share with dehydrogenases and kinases the classic nucleotide binding fold called the Rossmann fold, whereas the class II enzymes possess a different fold, not found elsewhere, built around a six-stranded antiparallel beta-sheet. The two classes of synthetases catalyze the same global reaction that is the attachment of an amino acid to the tRNA, but differ as to where on the terminal adenosine of the tRNA the amino acid is placed: class I enzymes act on the 2' hydroxyl whereas the class II enzymes prefer the 3' hydroxyl group. The three-dimensional structure of aspartyl-tRNA synthetase from yeast, a typical class II enzyme, is described here, in relation to its function. The crucial role of the sequence motifs in substrate binding and enzyme structure is high-lighted. Overall these results underline the existence of an intimate evolutionary link between the aminoacyl-tRNA synthetases, despite their actual structural diversity.

Adenosine Triphosphate↗
PubMed1995

Both apoptosis and necrosis occur following intrastriatal administration of excitotoxins.

To learn about the mechanisms of excitotoxic cell death in vivo, three different excitatory amino acid receptor agonists (kainic acid, quinolinic acid or quisqualic acid) were injected in the left striatum of adult rats. Brains were examined at 24 and 48 h after injection. Morphological and biochemical studies were performed using conventional stains, histochemistry, in situ labelling of nuclear DNA fragmentation, and agarose gel electrophoresis of extracted DNA. Large numbers of cells with cytoplasmic shrinkage and nuclear condensation or granular degeneration of the chromatin, and fewer cells with apoptotic morphology were distributed at random in the injured areas of the three groups of treated animals but not in rats injected with vehicle alone. A ladder pattern, typical of internucleosomal DNA fragmentation, was observed 24 h after treatment. This was replaced by a smear pattern, consistent with random DNA breakdown, at 48 h. These morphological and biochemical results suggest that prevailing necrosis together with apoptosis occur following intrastriatal injection of different excitotoxins.

Animals↗
PubMed1995

[Perforation of colonic diverticulum under corticoids: a complication to be known and recognized].

Glucocorticoids can produce acute perforation of colonic diverticula and peritoneal infection. We report two observations in which patients presented a peritoneal collection with no specific clinical signs. The diagnosis was considered after C-T scan or ultrasans. Residues of contrast liquid, after an earlier X-ray exploration, have made the diagnosis of diverticula easier. In one case, corticosteroids were started as a short cure for the treatment of a myeloma. In the other case, patient received a long term corticosteroid therapy at low dose for an asthmatic disease. The perforation was induced by an increased dosage. Diverticular perforations result from inhibition of synthesis of prostaglandins who have the beneficial property of "cytoprotection" and from the immunosuppressive action of glucocorticoids which favour the diffusion of the peritoneal infection. diffusion of the peritoneal infection.

Aged↗
PubMed1995

A role for calcium release-activated current (CRAC) in cholinergic modulation of electrical activity in pancreatic beta-cells.

S. Bordin and colleagues have proposed that the depolarizing effects of acetylcholine and other muscarinic agonists on pancreatic beta-cells are mediated by a calcium release-activated current (CRAC). We support this hypothesis with additional data, and present a theoretical model which accounts for most known data on muscarinic effects. Additional phenomena, such as the biphasic responses of beta-cells to changes in glucose concentration and the depolarizing effects of the sarco-endoplasmic reticulum calcium ATPase pump poison thapsigargin, are also accounted for by our model. The ability of this single hypothesis, that CRAC is present in beta-cells, to explain so many phenomena motivates a more complete characterization of this current.

Acetylcholine↗
PubMed1995

Effect of Beconase nasal spray on olfactory function in post-nasal polypectomy patients: a prospective controlled trial.

Numerous studies have postulated the possible benefit of corticosteroids on olfaction in patients with nasal/sinus disease. Twenty-nine patients with bilateral nasal polyps were included in our study using strict selection criteria to reduce other aetiologies of olfactory dysfunction. The University of Pennsylvania Smell Identification Test (UPSIT) was performed pre-operatively on the right and left nostrils separately. Following intranasal polypectomy the patients received a six-week course of beclomethasone nasal spray (Beconase) to one nostril only, with the other acting as a control. The UPSIT scores were again obtained for each nostril separately. Wilcoxon Signed Rank test revealed no statistically significant difference in UPSIT scores between treated and untreated nostrils (p = 0.31; power 70 per cent; ES = 0.47). We conclude that topical beclomethasone does not improve olfaction following nasal polypectomy.

Administration, Intranasal↗
PubMed1995

Meiotic instability of Pythium sylvaticum as demonstrated by inheritance of nuclear markers and karyotype analysis.

Progeny from a sexual outcross between opposite mating types of Pythium sylvaticum were analyzed for inheritance of RFLP and random amplified polymorphic DNA (RAPD) markers. Although most were inherited in expected Mendelian frequencies, several were not. Pulsed field gel electrophoresis was employed to examine these unexpected patterns of marker inheritance at a karyotypic level. Parental oogonial and antheridial isolates had different electrophoretic karyotypes and minimum number of chromosome-sized DNAs (13 and 12, respectively), however, summation of the sizes of all chromosomal bands for each isolate was similar at approximately 37 Mb. Progeny karyotypes differed significantly from each other and the parental isolates, ranging in estimated minimum number of chromosome-sized DNAs from 9 to 13 and the summation of band sizes within each isolate from 28.1 to 39.0 Mb. For the eight isolates most extensively analyzed, 80% of the progeny chromosome-sized DNAs were nonparental in size or hybridization grouping of cDNA clones and isolated RAPD markers. Based on the results of Southern analysis it appears that length mutations and perhaps aneuploidy and translocations have contributed to generation of karyotypic polymorphisms. Nineteen field isolates of P. sylvaticum collected from the same location also exhibited significantly different karyotypes, suggesting that the meiotic instability observed in the laboratory also is occurring in field populations.

Base Sequence↗
PubMed1995

Human papillomavirus infection in the malignant and premalignant head and neck epithelium.

A prospective study was undertaken to determine the prevalence and histological correlates of human papillomavirus infection in the head and neck epithelium. Oral, pharyngeal, and laryngeal paraffin-embedded samples were analyzed by polymerase chain reaction with use of human papillomavirus E6 consensus sequence primers. Human papillomavirus infection was detected in 20 of 126 (15.9%) patients. Twenty-five of 230 (10.9%) samples contained human papillomavirus DNA. Papillomaviruses were detected in 15 of 131 (11.4%) head and neck squamous cell carcinomas, in 3 of 32 (9.4%) dysplasias, and 2 of 19 (10.5%) keratoses. The most commonly identified human papillomavirus in cancerous, precancerous, and keratotic lesions was type 16 (80.0% of the isolates). Five papillomas were shown to contain human papillomavirus type 6. No other lesion in 42 samples contained human papillomavirus. Our data are consistent with the hypothesis that infection with certain types of human papillomavirus contributes to head and neck cancer although this may be so only in a minority of cases. Human papillomavirus infection may play a role in the earliest stages of tumorigenesis, since papillomaviruses can be found in laryngeal premalignant and keratotic lesions, which are closely linked to tobacco use.

Adolescent↗
PubMed1995

A restraining system for rhesus monkeys used in space research.

A new chronic restraining system has been designed specifically for male rhesus monkeys (8-13 kg) housed in weightlessness for scientific purposes. The restraining system consists of a coat (jacket and skirt) and a chair. The system separates the thorax from the lower part of the body, and allows large movements of the upper part of the body. The macaque can feed and groom itself, and can also sleep in close-to-normal position.

Animals↗
PubMed1995

Secretagogue-induced [Ca2+]i changes in single rat pancreatic islets and correlation with simultaneously measured insulin release.

The effects of secretagogues (glucose, tolbutamide and phorbol esters) on simultaneously measured intracellular free calcium concentration ([Ca2+]i) and insulin release were studied in rat pancreatic islets of Langerhans. Stimulatory concentrations (11mM) of glucose caused a transient [Ca2+]i. In contrast with mouse islets, rat islets scarcely showed glucose-induced [Ca2+]i oscillations. Digital image analysis showed that [Ca2+]i changes occurred synchronously across the whole islets. As expected simultaneously measured insulin release was biphasic with a clear second phase. This clearly indicated that in rat islets there is a lack of correlation between [Ca2+]i and insulin release. This was further explored using agents which separately promoted the first (tolbutamide, 200 microns and second (phorbol-12-myristate-13-acetate; PMA; 5nM) phases of insulin release. Tolbutamide induced a transient increase in [Ca2+]i. These results suggest that in rat islets the first phase of insulin release is calcium dependent, whereas the second phase is related to the activation of protein kinase C (PKC). However, the glucose-induced second phase of insulin release did not coincide with an increase in membrane-associated PKC activity. Other messengers may contribute to this late phase of insulin release.

Animals↗
PubMed1995

Slow [Ca2+]i oscillations induced by ketoisocaproate in single mouse pancreatic islets.

The effect of alpha-ketoisocaproate (KIC), the first catabolic metabolite of the amino acid leucine, on [Ca2+]i, insulin release, and membrane potential was measured in mouse pancreatic islets of Langerhans. Stimulatory concentrations of KIC (2.5-10 mmol/l) caused slow oscillations of [Ca2+]i and cyclic variations of the membrane potential. Slow [Ca2+]i oscillations depended on extracellular calcium. Simultaneous measurements of [Ca2+]i and insulin release resolved pulsatile insulin secretion that paralleled slow [Ca2+]i oscillations. Whereas 11 mmol/l glucose induced a significant increase in cAMP, KIC was unable to modify it. Glucagon (10 nmol/l), which significantly increased cAMP in mouse islets, also increased the frequency of glucose-induced fast [Ca2+]i oscillations. However, neither glucagon (10 nmol/l) nor dibutyryl cAMP (1 mmol/l) was able to change the slow oscillation pattern into a fast pattern. Imaging of Ca2+ showed that KIC-induced slow oscillations were synchronic throughout the whole islet. It is suggested that beta-cell electrical activity plays a role in the origin of slow [Ca2+]i oscillations.

Animals↗
PubMed1995

Vitamin A distribution among fat globule core, fat globule membrane, and serum fraction in milk.

In cream suspensions and partly skimmed milks obtained by successive centrifugation from whole milk, the concentration of vitamin A per gram of fat was inversely related to the mean size of fat globules. This result indicated that not all the vitamin A of milk was located in the fat globule core, which was further supported by studies of buttermilk and butter oil fractions obtained by churning of cream. These studies indicated that a portion of the vitamin A was associated with the fat globule membrane. The vitamin A content per gram of fat of purified fat globules was similar to vitamin A content per gram of fat of the whole milk from which they were isolated. This result indicated that the amount of vitamin A in the serum fraction was negligible and that vitamin A was localized in the fat globule and fat globule membrane.

Animals↗
PubMed1995

[Rupture of an aneurysm of the internal iliac artery into the primary iliac vein].

Authors present a case of spontaneous rupture of internal iliac artery in common iliac venous, and propose a review of cases reported in literature. Abreast of modern imagery and especially computed tomography is able to give a precise diagnosis, but angiography is the Most accurate procedure for detecting arteriovenous fistula and cannot be excluded out of diagnostic approach.

Aged↗
PubMed1995

Domestic violence: recognition, intervention, and prevention.

Domestic violence is a significant social and health problem that has received intensive recent publicity in the lay media. Nurses should play a major role in primary, secondary, and tertiary prevention interventions. Intensified health promotion and public policy initiatives can reduce the incidence of domestic violence in the future.

Adult↗
PubMed1995

[Verrucous carcinoma. Nosologic aspects, apropos of 4 cases].

INTRODUCTION: The nosology of verrucous carcinomas is a complicated problem. The name given to each manifestation may vary with localization. We report our findings in four cases with this skin disease. CASE REPORTS: Four patients, 76, 52, 76 and 55 years of age, presented with verrucous carcinoma. In the first case, the disease began with a chronic varicose ulceration localized on the anterolateral aspect of the right leg. In the second, the lesion was localized on the lateral aspect of the right leg facing a zone showing signs of repeated microtraumatisms. HPV-18 was isolated in this patient. The third case had a vegetating lesion on the dorsal aspect of the right hand, simulating a wart. The fourth case is a historic case in which a voluminous tumour developed over several years on an ulceration of the medial aspect of the left malleole, associated with trauma and venous insufficiency. COMMENTS: The three recent cases did not raise any particular problem with diagnosis. The diagnosis in the historical case, published in 1969 as a vegetating pyoderma, was corrected later. This illustrates the nosology problems raised in this particular form of epidermoid carcinoma which often has an impressive clinical presentation and a reassuring histology. The group of verrucous carcinomas include different skin or mucosal lesions formerly designated as oral florid papillomatosis, Buschke-Löwenstein acuminate condyloma or pseudo-epitheliomatous vegetating pyoderma. Cuniculatum epithelioma was added to this group for simplification although this rarely observed lesion is a separate entity. CONCLUSION: The pathology diagnosis of verrucous carcinoma requires large and deep biopsy. Treatment is surgical and regular follow-up is needed as for all malignant tumours.

Aged↗
PubMed1995

Frequency of obstructive sleep apnoea syndrome detected by means of a questionnaire in patients with coronary heart disease.

As previous studies have suggested an association between obstructive sleep apnea syndrome (OSA) and ischaemic heart disease, the aim of the present study was to evaluate the frequency of clinically relevant OSA in this selected population. From September 1992 to April 1993, 136 patients referred to the Cardiology Unit for suspected angina pectoris were asked to participate in the study. The main inclusion criterion was a stable coronary heart disease, diagnosed by angiography. A sleep questionnaire was administered by a trained physician. Patients who experienced one of the following symptoms: association of body mass index (-weight/height2) above 27.5 and heavy snoring, breathing stops, or daytime hypersomnolence, were selected for a nocturnal oxygen saturation recording. The occurrence of at least one desaturation, defined as a 4% fall from baseline, led to a full night-time polysomnography. One hundred and eight patients (78 males), satisfied the entry criteria. A pulse oximetry was performed in 15, and three patients experienced a significant desaturation. Finally, one patient satisfied the criteria of OSA. The estimated proportion of OSA amounted to 0.92%, in accordance with the prevalence of OSA described in the general population. Clinically relevant OSA does not appear to be more frequent in patients suffering from stable coronary heart disease. Systematic sleep investigations in such patients do not appear to be useful in daily clinical practice.

Aged↗