Streptomyces contain a 7.0 kDa cold shock like protein.
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Amino Acid Sequence↗
Biomedical subjects
G Cohen
Publications and source records attributed to G Cohen.
[Pneumopathies caused by Chlamydia pneumoniae].
Among the atypical pneumonias observed between March 1990 and March 1991, 6 were diagnosed as being caused by Chlamydia pneumoniae of the TWAR strain. The serological diagnosis was obtained by a microimmunofluorescence test. All 6 patients had anti-TWAR antibody levels higher than 512; they were treated with a macrolide administered by the oral route and were cured without sequelae or recurrences. Four cases received a ten day course of roxithromycin 300 mg/day and one case received erythromycin 2 g/day also for 10 days. The sixth case received a short course of azithromycin 500 mg once daily for three days. In 2 other patients presenting with clinical and radiological signs of pneumonia the diagnosis of C. pneumoniae infection could not be made despite an antibody level equal or higher than 512, since the serological results showed cross-reactions between C. pneumoniae, C. trachomatis and C. psittaci antibody responses.
Aged↗
Lead poisoning in young children in Washington, DC: a crisis that remains to be addressed.
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Child↗
Hypofrontality in neuroleptic-naive patients and in patients with chronic schizophrenia. Assessment with xenon 133 single-photon emission computed tomography and the Tower of London.
The "hypofrontality hypothesis" has been supported by many neuroimaging studies, but not all, perhaps because of heterogeneity of samples. The present study examined three different samples that permitted assessment of a variety of confounders, such as effects of long-term treatment, chronicity of illness, and presenting phenomenology: (1) 13 neuroleptic-naive schizophrenic patients, (2) 23 nonnaive schizophrenic patients who had been relatively chronically ill but were medication free for at least 3 weeks, and (3) 15 healthy normal volunteers. Regional cerebral blood flow was measured using single-photon emission computed tomography with xenon 133 as the tracer. The control condition consisted of looking at undulating colored shapes on a video monitor, while the experimental task was the Tower of London. We observed the Tower of London to be a relatively specific stimulant of the left mesial frontal cortex (probably including parts of the cingulate gyrus) in healthy normal volunteers. Both the neuroleptic-naive and the nonnaive patients lacked this area of activation, as well as a related one in the right parietal cortex (representing the circuitry specifically activated by the Tower of London). Decreased activation occurred only in the patients with high scores for negative symptoms. These results suggest that hypofrontality is related to negative symptoms and is not a long-term effect of neuroleptic treatment or of chronicity of illness.
Adult↗
The oxidant stress hypothesis in Parkinson's disease: evidence supporting it.
Oxidant stress, due to the formation of hydrogen peroxide and oxygen-derived free radicals, can cause cell damage due to chain reactions of membrane lipid peroxidation. Because the substantia nigra is rich in dopamine, which can undergo both enzymatic oxidation via monoamine oxidase and nonenzymatic autoxidation, hydrogen peroxide and oxyradicals (superoxide anion radical and hydroxyl radical) are generated in this midbrain nucleus. Although proof that oxidant stress actually causes the loss of monoaminergic neurons in patients with Parkinson's disease is lacking, there is a considerable body of evidence from studies in both animals and humans that support the concept. (1) Neurotoxins that selectively destroy the dopaminergic neurons in the nigra, such as 6-hydroxydopamine and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), appear to act via oxidant stress. (2) The substantia nigra of patients with Parkinson's disease reveals evidence of oxidant stress by the findings of increased lipid peroxidation and decreased reduced glutathione. (3) Total iron is increased and ferritin is reduced in the substantia nigra pars compacta in patients with Parkinson's disease. This combination suggests that this transition metal is in a low molecular weight form, capable of catalyzing nonenzymatic oxidative reactions, especially the conversion of hydrogen peroxide to hydroxyl radical, which is the most reactive of the oxygen radicals. (4) Neuromelanin, a product of dopamine autoxidation, can serve as a reservoir for iron, promoting the generation of oxyradicals. (5) Antioxidant defense mechanisms appear to be reduced in the parkinsonian substantia nigra with the findings of decreased activities of glutathione peroxidase and catalase.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Enhancement of osteoinduction by vitamin D metabolites in rachitic host rats.
Diaphyseal bone from normal Sprague-Dawley rats was delipidated in chloroform-methanol and demineralized in 0.6 N HCl at 4 degrees C. The bones were then implanted for 7-28 days into rats made rachitic by a low-phosphate, vitamin D-deficient diet (VDP-) for 3 weeks. Bones from VDP- and normal rats were also implanted into normal hosts. When normal rats were used as the host environment, a consistent sequence of cartilage induction and bone formation was observed. Demineralized rachitic bone (RB) implanted into normal host rats resulted in cartilage and bone induction similar to that seen for normal bone (NB) implants. Transmission electron microscopy of RB in normal hosts revealed morphologically normal chondrocytes and cartilage matrix with normal mineralization. In contrast, implantation of NB in VDP- hosts resulted in delayed chondrogenesis and lack of calcification. Furthermore, similar results were observed when RB was implanted into VDP- hosts. Treatment of VDP- hosts with either 1 alpha-hydroxyvitamin D3 or 24,25-dihydroxyvitamin D3 did not accelerate the sequential appearance of precartilage or cartilage. However, 24,25-(OH)2D3 administered alone or in combination with 1 alpha-OHD3 significantly increased the amount of calcified cartilage observed at 2 weeks postimplantation compared to implants from either untreated VDP-hosts or those treated only with 1 alpha-OHD3. New bone formation was observed at 4 weeks postimplantation in all vitamin D-treated groups as determined by von Kossa staining or direct electron microscope examination. There was no apparent difference in the quantitative or qualitative bone formed within the various vitamin D-treated groups. Serum calcium and phosphorus levels were lower and alkaline phosphatase levels were higher in VDP- hosts compared with normal animals or those treated with vitamin D metabolites. The results of this study show a reduction in the capacity of progenitor cells in VDP- rat hosts to respond to osteoinductive factor(s). This impaired response appears to be corrected by vitamin D metabolites.
24,25-Dihydroxyvitamin D 3↗
Segmentation techniques for the classification of brain tissue using magnetic resonance imaging.
A technique is described for classifying brain tissue into three components: gray matter, white matter, and cerebrospinal fluid. This technique uses simultaneously registered proton density and T2-weighted images. Samples of each of the three types of tissue are identified on both image sets and used as "training classes"; these tissue samples are then used to generate a linear discriminant function, which is used to classify the remaining pixels in the image data set. Effects of varying the location and number of training classes have been explored; six pairs of training classes have been found to yield a suitable classification. Interrater and test-retest reliability have been examined and found to be good. Intrascanner and interscanner reproducibility has also been evaluated; classification rates are reproducible within the same individual when the same scanner is used, but in this study poor reproducibility occurs when the same individual is scanned on two different scanners. The validity of the technique has been tested by examining correlations between traced and segmented regions of interest, evaluating correlations with age, and conducting phantom studies, in addition to using visual inspection of the classified images as an indication of face validity. From all four perspectives, the method has been found to have good validity. Additional applications, strengths, and limitations are discussed.
Age Factors↗
Penicillin and cephalosporin biosynthetic genes: structure, organization, regulation, and evolution.
Penicillins and cephalosporins are produced by a wide variety of microorganisms, including some filamentous fungi, many gram-positive streptomycetes, and a few gram-negative unicellular bacteria. All produce these beta-lactam antibiotics by essentially the same biosynthetic pathway. Recently, most of the penicillin and cephalosporin biosynthetic genes have been cloned, sequenced, and expressed. The biosynthetic genes code for enzymes that possess multifunctional peptide synthetase, cyclase, epimerase, expandase, hydroxylase, lysine aminotransferase, and acetyltransferase activities and are organized in chromosomal gene clusters and coordinately expressed. DNA hybridization screens of streptomycetes demonstrate that beta-lactam biosynthetic genes may be more widespread in nature than is indicated by conventional antibiotic screens. They offer the possibility of expanding the search for organisms with potential to make new beta-lactam antibiotics. Attempts to improve current yields of beta-lactams in production strains by introducing into them additional copies of biosynthetic genes have been partially successful. Comparative sequence analysis of bacterial and fungal beta-lactam biosynthetic genes show they share very high sequence identity. A model that explains the similarity of biosynthetic genes from an evolutionary standpoint assumes horizontal gene-transfer between the two groups of organisms. Indirect evidence suggests the transfer occurred from the bacteria to the fungi.
Amino Acid Sequence↗
Image processing for the study of brain structure and function: problems and programs.
Fundamental problems in the analysis of functional and structural imaging data include data transport, boundary identification (including manual tracing, edge detection, and tissue segmentation), volume estimation, three-dimensional reconstruction and display, surface and volume rendering, shape analysis, and image overlay. These problems require that research investigators have access to suitable methods of image analysis, implemented on a set of software programs, in order to conduct neuroimaging research. The authors describe a group of software programs designed to provide a comprehensive solution for these problems.
Brain↗
Long-term study of brain lesions following soman, in comparison to DFP and metrazol poisoning.
The long-term histopathological effects of acute lethal (95 micrograms kg-1) and sublethal (56 micrograms kg-1) doses of soman were studied in rats and were compared to lesions caused by equipotent doses of either another cholinesterase (ChE) inhibitor, DFP (1.8 mg kg-1), or a non-organophosphorus convulsant, metrazol (100 mg kg-1). Severe toxic signs were noted following one LD50 dose administration of all the compounds, yet only soman induced brain lesions. Moreover, even when administered at a sublethal dose (0.5 LD50), soman induced some histological changes without any clinical signs of intoxication. Soman-induced brain lesions were assessed quantitatively using a computerized image analyser. The analysis was carried out for up to 3 months following administration, and a dynamic pattern of pathology was shown. The cortical thickness and area of CA1 and CA3 cells declined significantly as early as 1 week post-exposure. No pathological findings were detected following DFP and metrazol administration. It is therefore suggested that brain lesions are not common for all ChE inhibitors and that convulsions per se are not the only factor leading to brain damage following the administration of soman. The degenerative process (found also with the sublethal dose of soman) might be due to a secondary effect, unrelated to soman's clinical toxicity, but leading to long-term brain injuries.
Animals↗
[The estrogen-androgen profile is unchanged in men with cholelithiasis].
It is well established that cholelithiasis is more frequent in women than in men. This difference is usually explained by the effects of estrogens and progesterone on the metabolism of bile acids, biliary cholesterol secretion and saturation, and gallbladder motility. Another explanation could be a protective effect of androgens against cholelithiasis in men. To test this hypothesis, we determined the hormonal, androgenic and estrogenic, status of 15 male patients with asymptomatic gallstone disease and in 15 control patients with normal gallbladder matched for age and body weight. No significant difference in the plasma concentrations and the urinary excretion rate of sex hormones (testosterone, dihydrotestosterone, androstenedione, testosterone and androstanediol glucuronides, estradiol, estrone, total estrogens), as well as in the plasma sex hormone binding globulin, was found between the 2 groups of patients. The development of cholelithiasis in men, therefore, does not appear to be related to modification of sex steroids.
Adult↗
Evidence for the interaction between antacid and gastric mucosa using an "artificial stomach" model including gastric mucosa.
In light of evidence that certain aluminum-based antacids adhere to the gastric mucosa, we modified our previously described "artificial stomach" (AS) model by including a piece of hog stomach and compared the antacid activity of six aluminum-containing antacid products in the model with and without gastric mucosa. The activity of three of these, Maalox, Riopan and Supralox, was not significantly different in the two systems. In contrast, the activity of the other three, Aludrox, Phosphalugel and Simeco, was significantly greater with mucosa. Antacid activity of one product from each set (Supralox, Phosphalugel) was evaluated in two in vivo methods in human volunteers. For both antacids, results in vivo were similar to those obtained with the AS-containing mucosa. Without mucosa, in vivo and in vitro results were dissimilar for Phosphalugel, thus validating the modified AS. The difference between the two sets of antacids can be explained by 1) the fact that the Al:Mg ratio in the set affected by mucosa is greater than that of unaffected antacids, and 2) a weaker antacid load than in unaffected Supralox. We suggest that in an acid milieu, aluminum ions in antacids like Aludrox, Phosphalugel and Simeco are bound to sialic acid residues in mucus glycoproteins, thus retarding the transit of these antacids through both the AS and the real stomach and prolonging their activity in both situations. When the Al:Mg ratio is low or when the amount of antacid salts is large, aluminum ions tend to be buried in complexes, giving them less chance to interact with gastric mucus, so they transit the stomach more quickly.
Adult↗
High level expression in Escherichia coli of isopenicillin N synthase genes from Flavobacterium and Streptomyces, and recovery of active enzyme from inclusion bodies.
A T7 promoter-based vector was used to express the isopenicillin N synthase (IPNS) genes of Flavobacterium sp. 12,154 and Streptomyces jumonjinensis in Escherichia coli. Most of the IPNS synthesized at 37 degrees C, and representing some 22% and 51% of the total cell protein respectively, occurred in an insoluble, enzymatically inactive form. Active IPNS was recovered in a rapid and simple two-step procedure in which the insoluble material was first denatured in 5 M urea and then refolded by passing the solubilized IPNS through a G-25 Sephadex sizing column. Further chromatography on DEAE-Sepharose resulted in highly active IPNS preparations. This procedure was found to be well suited for scaling up to produce large amounts of IPNS.
Cloning, Molecular↗
Intramitochondrial formation of oxidized glutathione during the oxidation of benzylamine by monoamine oxidase.
Oxidation of benzylamine by MAO results in an accumulation of GSSG in mouse liver mitochondria. Formation of GSSG is prevented by deprenyl, an inhibitor of MAO-B, but not by catalase. GSSG accumulation also occurs with dopamine as substrate. Oxidation of monoamines by mitochondrial MAO represents a potential oxidant stress for mitochondria.
Animals↗
Role of transesophageal echocardiography in the diagnosis and management of prosthetic valve thrombosis.
Thrombosis is a serious complication of heart valve replacement. Diagnosis is often difficult with previously reported techniques, including precordial two-dimensional echocardiography, suffering from low sensitivity and specificity. Management is similarly difficult, with a 40% to 50% reported mortality rate in early surgical series. Three cases are presented in which thrombosis of a left-sided prosthetic valve (one aortic, three mitral) was diagnosed by means of transesophageal echocardiography. All three patients were treated with streptokinase and had clinical and echocardiographic resolution. In one patient, who had recurrent thrombosis and received a second course of streptokinase, the course was complicated by a massive embolic stroke and death. Another patient with a recurrence underwent successful valve replacement. Transesophageal echocardiography is ideal for the diagnosis and follow-up of patients with prosthetic valve thrombosis. Although effective, thrombolysis in this setting is associated with a high risk of thromboembolic phenomena and significant risk of death. Thrombolytic therapy may be considered in highly selected patients who have an unacceptable risk for reoperation.
Adult↗
T1 and T2 relaxation times in schizophrenia as measured with magnetic resonance imaging.
T1 and T2 relaxation times were measured in ten brain regions on the right and left side in a sample of 27 schizophrenic patients and 37 normal controls. The schizophrenic patients showed a prolongation of T2 relaxation time, and to a lesser extent of T1 relaxation time, which was more predominantly localized in the right hemisphere and in gray matter structures. These results may indicate that metabolic, physiological, or neurochemical brain function in schizophrenia is related in some way to a change in tissue fluid in neuronal cell bodies or interstitial gray matter.
Adult↗
Problems with ratio and proportion measures of imaged cerebral structures.
Ratio measures, such as the ventricle-brain ratio (VBR) based on computed tomography or magnetic resonance imaging, are widely used in psychiatric research in studies of brain function and morphology. While imaging techniques have advanced considerably, the form of the index of a structure's size has remained the same--a proportion based on an estimate of the structure's size divided by a like estimate of the whole brain size. We demonstrate that ratio and similar indices can suffer greatly in reliability when compared with simple volume measures. This loss of reliability is related to the relation of a structure's size and whole brain size. We review various methods for measuring the size of structures and discuss their strengths and limitations in terms of reliability and validity. In many instances, other methods of "correcting" for brain size (e.g., regression or covariance) may yield measurements that are more appropriate than ratios.
Adult↗
Protein import into peroxisomes in vitro.
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Amino Acid Sequence↗