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Biomedical subjects

D Klein

Publications and source records attributed to D Klein.

At least 91 records · Page 5Linked to original sources
PubMed1996

2-Chloroacetophenone is an effective glutathione depletor in isolated rat hepatocytes.

The glutathione (GSH) depleting effect of 2-chloroacetophenone (CN) was studied in freshly isolated rat hepatocytes. CN proved to be more effective in depleting GSH than diethylmaleate, phorone or styrene oxide. The reaction between GSH and CN followed a 1:1 stoichiometry, allowing adjustment of cellular GSH concentrations at distinct levels. After incubating cells (8 mg protein/ml) with 200 mumol CN/l for 5 min, GSH depletion was almost complete without signs of cytotoxicity. At 300 mumol/l CN, GSH depletion persisted, and cytotoxicity occurred after 30 min. Activities of cytochrome P450 dependent enzymes, even at concentrations up to 500 mumol CN/l, were only marginally affected. Therefore, CN is of particular value for in vitro studies at decreased availability of GSH.

Animals↗
PubMed1996

[Indications for total parenteral nutrition or small intestine transplantation?--Prognostic factors in short bowel syndrome].

After massive intestinal resection resulting in short bowel syndrome it is often unclear if the patient will remain on total parenteral nutrition (TPN) or regain enteral autonomy. Small bowel transplantation or bowel-lengthening procedures could potentially be a therapeutic option for patients confined to life-long parenteral nutrition. Initiated early in the course of the disease this could prevent frequent serious complications of long-term parenteral nutrition. However, it is unclear which factors determine the outcome of these patients. For further information on the long-term prognosis, data of 33 patients with short bowel syndrome operated in our institution from 1982 to 1995 were retrospectively analyzed and the present status of all living patients evaluated. Gender, age or underlying disease had no influence on the adaptation of the small intestine or the duration of TPN in the surviving patients. Return to enteral autonomy mainly depended upon the length of the remaining small and large bowel. Thus the further course of the disease can be predicted and necessary measures can be taken as this information is always available at the time of initial surgery.

Adult↗
PubMed1995

Determination of Cu-containing metallothionein: comparison of Ag saturation assay, thiomolybdate assay, and enzyme-linked immunosorbent assay.

Three methods for the quantification of Cu-containing metallothionein (MT) (Ag saturation assay, thiomolybdate assay, and enzyme-linked immunosorbent assay (ELISA)) were compared for their ability to recover in vitro prepared standard Cu-MT both in absence and presence of rat liver cytosol. Uniform molar calibration of the assays was achieved using the nitrogen content of the standard Cu-MT measured by the Kjeldahl procedure. With all three methods Cu-MT reliably could be quantified. The Ag saturation assay and the thiomolybdate assay, dependent on the amount of Cu-MT and the presence of hepatic cytosol, showed a tendency to over- or underestimate the theoretical expectation. The ELISA generally performed best and moreover was three orders of magnitude more sensitive than the other two assays. With all three methods corresponding MT levels were found in the Cu-rich liver of a Long-Evans Cinnamon rat.

Animals↗
PubMed1995

The neural substrates underlying word generation: a bilingual functional-imaging study.

We used positron emission tomography to investigate word generation in subjects whose first language was English but who were also proficient in French. These subjects performed three types of lexical search: rhyme generation based on phonological cues, synonym generation requiring a semantic search, and translation involving access to a semantic representation in the other language. Two control tasks required word repetition in each language. We investigated whether phonological and semantic word-generation activate similar regions and whether the same neural substrates subserve the second language as subserve the first. A series of cerebral blood flow increases, corresponding to Brodmann's areas 47, 46, 45, and 8, were observed in the left frontal cortex when the baseline repetition task was subtracted from each of the respective generation tasks. The results suggest that common neural substrates are involved in within- and across-language searches and that the left inferior frontal region is activated irrespective of whether the search is guided by phonological or semantic cues.

Acoustic Stimulation↗
PubMed1995

Involvement of nitric oxide in the regulation of peripheral blood leukocyte counts.

A role for nitric oxide (NO) in the regulation of blood leukocyte numbers was examined in BALB/c mice by employing the NO synthase inhibitor NG-nitro L-arginine methyl ester (L-NAME). Treatment of animals with a single dose of 50 mg/kg body wt caused a dramatic increase in the number of circulating neutrophils and a moderate decrease in the number of circulating lymphocytes. These effects were partially reversed by the simultaneous inoculation of L-arginine (250 mg/kg body wt.) but not by D-arginine. A second NO synthase inhibitor, NG-nitro L-arginine, induced changes comparable to those elicited by L-NAME. Because catecholamines and glucocorticoids are well-known modulators of blood leukocyte counts, experiments were carried out in adrenalectomized mice. It was found that adrenalectomy did not modify the increase in the number of circulating neutrophils induced by L-NAME but completely prevented the decrease of circulating lymphocytes. Taken together, these findings support the hypothesis that NO plays an important role in the regulation of the peripheral blood number of neutrophils and lymphocytes, and that this function involves, in each case, the participation of different mechanisms.

Animals↗
PubMed1995

Molecular cloning of major histocompatibility complex class II B gene cDNA from the Bengalese finch Lonchura striata.

The only avian major histocompatibility complex (Mhc) genes thus far identified are from species of the relatively small order of Galliformes, while by far the largest order of Passeriformes (songbirds), containing some 60% of extant bird species, has not been studied at all in this regard. The Galliformes emerged more than 55 million years (my) ago, the Passeriformes some 25 my ago. Because of the potential for the use of Mhc genes as markers in the study of songbird populations, an attempt was made to clone class II B genes of a passeriform species, the Bengalese finch Lonchura striata acuticauda. Using a set of primers designed on the basis of known sequences, a probe corresponding to part of exon II was obtained by the polymerase chain reaction. The probe was then used to screen a Bengalese finch cDNA library and to isolate and sequence two nearly full-length clones. The sequences reveal the presence of one presumably functional class II B locus in this bird species.

Amino Acid Sequence↗
PubMed1995

Kinetic study of interaction between BRL 42715, beta-lactamases, and D-alanyl-D-alanine peptidases.

A detailed kinetic study of the interactions between BRL 42715, a beta-lactamase-inhibiting penem, and various beta-lactamases (EC 3.5.2.6) and D-alanyl-D-alanine peptidases (DD-peptidases, EC 3.4.16.4) is presented. The compound was a very efficient inactivator of all active-site serine beta-lactamases but was hydrolyzed by the class B, Zn(2+)-containing enzymes, with very different kcat values. Inactivation of the Streptomyces sp. strain R61 extracellular DD-peptidase was not observed, and the Actinomadura sp. strain R39 DD-peptidase exhibited a low level of sensitivity to the compound.

Anti-Bacterial Agents↗
PubMed1995

Involvement of bactericidal factors from thrombin-stimulated platelets in clearance of adherent viridans streptococci in experimental infective endocarditis.

Platelets activated with thrombin release bactericidal factors. We studied the role of the susceptibility of viridans streptococci to these bactericidal factors in the development of infective endocarditis (IE). By using the experimental endocarditis rabbit model, the initial adherence and the development of IE were assessed for 10 viridans streptococcal strains differing in their susceptibilities to releasate (material released) from thrombin-activated platelets. Six strains were susceptible and four strains were resistant to these releasates. The numbers of vegetations (VGs) colonized at 5 min and 48 h after intravenous challenge with 10(4) CFU were determined. At 5 min after challenge, significantly more VGs were colonized with bacteria of the six platelet releasate-susceptible strains than with bacteria of the four releasate-resistant strains (P < 0.005). In the releasate-susceptible group of strains, the number of colonized VGs decreased significantly between 5 min and 48 h after intravenous inoculation (P < 0.001). Such a decrease was not observed with the releasate-resistant strains. As a result, the final developments of IE due to releasate-susceptible and -resistant strains were not significantly different. The releasate-susceptible strain 1 and the releasate-resistant strain 2 were selected for more detailed experiments. Rabbits were killed at 5 and 30 min and 2, 4, and 48 h after inoculation. The number of culture-positive VGs as well as the number of adherent bacteria on the individual VGs were determined. The 90% infective dose for each strain was 10(5) CFU. At low inoculum concentrations (10(3) and 10(4) CFU) a larger proportion of the inoculated bacteria of both strains was found to be adherent on VGs than at higher challenge doses. The number of culture-positive VGs as well as the number of adherent bacteria per VG decreased rapidly in the first 30 min after challenge with strain 1 but not after challenge with strain 2. Additional experiments with the platelet releasate-susceptible strain S224 and the platelet releasate-resistant stain S182 confirmed the data obtained with strains 1 and 2 and indicated that releasate-susceptible strains disappeared from the VGs with time, whereas releasate-susceptible strains persisted. In vitro studies with VGs excised 5 min after challenge with stain 1 or 2 showed that clearance of the releasate-susceptible strain 1 was not caused by complement bactericidal activity or surface phagocytosis by polymorphonuclear cells. Bacterial cells of strain 1 adherent on excised VTGs were rapidly cleared by exposure to fresh clotting blood or to releasates from thrombin-stimulated platelet suspension.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Acetaminophen-induced toxicity to human epidermoid cell line A431 and hepatoblastoma cell line Hep G2, in vitro, is diminished by silymarin.

The skin and liver may be targets for cytotoxicity induced by oxidative drug metabolites. We used human epidermoid A431 cells and human hepatoblastoma Hep G2 cells as the experimental model. The aim of the study was to investigate and evaluate the effect of silymarin on acetaminophen (APAP)-induced toxicity under controlled conditions. Silymarin is known to be a potent antioxidant that diminishes toxicity induced by a variety of other hepatotoxins (e.g. Amanita phaloides, algae's toxins, carbon tetrachloride). Glutathione (GSH) depletion was enhanced by adding to the medium buthionine sulfoximine [L-buthionine-(S,R)-sulfoximine, BSO]. Cells were incubated with high-concentration 5-20 mM APAP or alpha-(minimum essential medium for 2-24 h to evaluate the drug's ability to reduce cytoviability. Viability was then quantitated by metabolism of the tetrazolium dyes (MTT) and neutral red (NR). Cytoviability was 100% for controls. For Hep G2 treated for 24 h with 20 mM, APAP viability was 56.0% by MTT and 62.5% by NR. BSO-treated cells showed an enhanced cytotoxicity, determined by both assays. Administration of 0.5 mM silymarin reduced cytotoxicity significantly. In A431 cells, treatment with 20 mM APAP reduced viability by 57% (MTT) and 69% (NR) versus control (100%). BSO further decreased viability. Since incubation with silymarin showed significant protection against APAP toxicity, it can be considered a cytoprotective agent in this in vitro model of drug toxicity. GSH concentrations in both cell lines decrease significantly after exposure to 20 mM APAP, or 0.5 mM versus control (p < 0.05), and increased (p < 0.001) if incubated with APAP and silymarin. The protective effect could be through mitochondrial membrane stabilization and/or an increase in available GSH.

Acetaminophen↗
PubMed1995

Treatment of chronic depression with sertraline or imipramine: preliminary blinded response rates and high rates of undertreatment in the community.

Despite the prevalence of chronic depression and its associated morbidity, there has been little systematic study of pharmacotherapy for this disorder. In this article, we report a preliminary analysis of the first 12-week phase of a multicenter clinical trial that will eventually include approximately 635 patients in acute, continuation, crossover, and maintenance studies of sertraline, a selective serotonin reuptake inhibitor (SSRI), and imipramine, a tricyclic antidepressant, for the treatment of chronic depression. Of the first 212 patients to enter the study, 168 completed all 12 weeks; of these, 61.3 percent were responders, including 58.9 percent of the 73 patients with chronic major depression and 63.2 percent of the 95 patients with double depression. Only 26.8 percent of the 198 patients for whom such data were available had ever had an adequate trial of an antidepressant medication, defined as 150 mg/day of imipramine or its equivalent taken for at least 4 consecutive weeks. In general, demographic and diagnostic characteristics were more similar than different for patients with chronic major and double depression. However, comorbid generalized anxiety disorder was significantly more common in patients with chronic major depression (11.2% threshold for chronic versus 4.9% threshold for double depression, p = .02). The results of this study provide preliminary evidence of the responsiveness of patients with chronic major or double depression to an SSRI or a tricyclic antidepressant.

1-Naphthylamine↗
PubMed1995

Studies of adenovirus-induced eye disease in the rabbit model.

PURPOSE: To achieve a better understanding of the pathogenic processes associated with human adenovirus (Ad)-induced ocular disease. METHODS: Growth curves of Ad5 and Ad14 were performed in cell cultures derived from rabbit and human corneal epithelium (CE) and corneal keratocytes (CK). For in vivo studies, rabbit eyes were inoculated intrastromally and topically with 10(6) plaque-forming units per eye of Ad5 and ultraviolet light-inactivated (UV-1) Ad5 or Ad14, and the clinical features of the eyes were evaluated by biomicroscopic slit lamp examinations. Duration and quantitation of virus in tear samples were monitored. Humoral response was evaluated by enzyme-linked immunosorbent assay and serum neutralization titrations. Histopathologic and immunocytochemical staining of frozen corneal tissues was performed to determine the expression of major histocompatibility complex (MHC) class I and II and the presence of CD4+ and CD8+ T lymphocytes and CD18+ cells after the immunopathologic response elicited by virus inoculation. RESULTS: Both Ad5 and Ad14 replicated in all human cell cultures studied. In cells of rabbit origin, Ad5 replicated in cultured CE and CK cells, whereas Ad14 replication appeared restricted. Virus titers in ocular samples from Ad5-inoculated eyes peaked on postinoculation days 3 through 4, with approximately a 100-fold increase in infectious virus in comparison to initial titers. The duration of Ad5 shedding was 8.9 +/- 2.4 days. Ad5, Ad5 UV-I, and Ad14 induced seroconversion and subepithelial opacities. CD4+ and CD8+ T lymphocytes and CD18+ cells were present in these intrastromal immune cell infiltrates. Expression of MHC class I and II was observed in keratocytes and immune cells; MHC class I also was expressed on CE cells in inflamed areas. CONCLUSIONS: Ad5 is capable of replicating in both CE and CK cells of the rabbit eye. The presence of Ad antigens within the corneal stroma originating from infectious virus (Ad5), UV-inactivated virus (Ad5), or nonreplicating infectious virus (Ad14) can elicit indistinguishable immunopathologic responses in the stroma composed of CD4+, CD8+, and CD18+ cells.

Adenoviridae↗
PubMed1995

A method for quantification and correction of proteins after transfer to immobilization membranes.

A method is described for quantification of specific proteins after electrophoresis and transfer to immobilization membranes for Western blots. This method is analogous to methods used to correct the amounts of specific transcripts detected on Northern blots. Ponceau S staining of proteins bound to immobilization membranes is efficient and accurate compared to antibody binding in terms of time, effort and cost. Comparison of Ponceau S to other detection and staining methods for quantifying proteins and the basic chemistry of Ponceau S are summarized.

Actins↗
PubMed1994

Beating neonatal rat cardiomyocytes as a model to study the role of xenoreactive natural antibodies in xenotransplantation.

The hyperacute rejection reaction of xenogeneic organs is supposed to be triggered by xenoreactive natural antibodies of the recipient organism. In an experimental set-up allowing for rapid medium exchange, primary cultures of spontaneously beating neonatal rat cardiomyocytes were challenged with dialyzed human serum containing xenoreactive natural antibodies. After adding the serum specimens, a reproducible pattern of disturbed contractility was observed: following an initial increase in beating frequency, spontaneous contractions stopped completely. This standstill was reversible in all experiments. No signs of permanent cytotoxicity were observed. The temporary cessation of contractions was prevented by raising extracellular calcium concentration, but not by extracellular electrical stimulation. After absorption of xenoreactive natural antibodies, cellular contractions ensued without interruption. Inactivated serum specimens produced similar effects on contractility, although the duration of the standstill period was significantly shorter. The same qualitative phenomenon occurred when sera of other xenogeneic species were used. These results point to a temporary functional disturbance of parenchymal cells by xenoreactive natural antibodies, whereas no chronic cytotoxicity was conspicuous in these experiments.

Animals↗
PubMed1994

Left putaminal activation when speaking a second language: evidence from PET.

The neural representation of the languages of the polyglot speaker has been highly controversial. We used positron emission tomography (PET) to investigate whether production in a second language (L2) involves the same neural substrates as that of a first language (L1) in normal bilingual subjects who learned L2 after the age of 5 years. Comparison of cerebral blood flow (CBF) when repeating words in L2 and repeating words in L1 yielded only a single significant CBF change: an increase in the left putamen. We hypothesize that this region plays a specific role for articulation in L2. The role of the putamen in articulation is supported by foreign accent syndrome (FAS), which can occur after left putaminal damage. The increased articulatory demands imposed by speaking a second language may require complex motor control for speech production in L2.

Adult↗
PubMed1994

Chemotaxis, sporulation, and larvicide production in Bacillus sphaericus 2362. The influence of L-ethionine, and of aminophenylboronic acid.

4-Aminophenylboronic acid (APBA), a known inhibitor of sporulation in Bacilli, as well as L-ethionine, a known inhibitor of chemotaxis in Enterobacteria, inhibited both sporulation and chemotactic behavior but not growth of Bacillus sphaericus. Both compounds also inhibited the methyl group turnover on the methyl-accepting chemotaxis protein (P53) in this microorganism. Sporulation of B. sphaericus was inhibited only when APBA was added to the growing culture before the late logarithmic stage. It was previously demonstrated that the ability of B. sphaericus to respond to chemoattractants sharply declines at the same age of the culture. Thus, it seems plausible that the action of both inhibitors upon sporulation may be attributed to the inhibition of some regulatory pathway common to chemotaxis and sporulation and involving protein methylation. Possible exchange of the nutrient depletion-related sensory information between chemotaxis and sporulation systems at the level of methyl group transfer is discussed.

Bacillus↗
PubMed1994

Chemotaxis, sporulation, and larvicide production in Bacillus sphaericus 2362. The influence of L-ethionine, and of aminophenylboronic acid.

4-Aminophenylboronic acid (APBA), a known inhibitor of sporulation in Bacilli, as well as L-ethionine, a known inhibitor of chemotaxis in Enterobacteria, inhibited both sporulation and chemotactic behavior but not growth of Bacillus sphaericus. Both compounds also inhibited the methyl group turnover on the methyl-accepting chemotaxis protein (P53) in this microorganism. Sporulation of B. sphaericus was inhibited only when APBA was added to the growing culture before the late logarithmic stage. It was previously demonstrated that the ability of B. sphaericus to respond to chemoattractants sharply declines at the same age of the culture. Thus, it seems plausible that the action of both inhibitors upon sporulation may be attributed to the inhibition of some regulatory pathway common to chemotaxis and sporulation and involving protein methylation. Possible exchange of the nutrient depletion-related sensory information between chemotaxis and sporulation systems at the level of methyl group transfer is discussed.

Bacillus↗
PubMed1994

Crystallization and preliminary crystallographic analysis of sfericase. A Bacillus sphaericus calcium-dependent serine proteinase.

Sfericase is an important intracellular proteinase produced by Bacillus sphaericus in the stationary phase of growth. It is a Ca(2+)-dependent serine proteinase with optimal activity at pH 9.0 to 9.3. The molecular mass of sfericase is 32 kDa, as determined by sedimentation equilibrium. It seems to be involved in the interplay of various elements of the mosquitocidal activity of B. sphaericus, and hence is important for biological mosquito control. Sfericase significantly reduces viscosity of human pathological bronchial secretions and has recently shown good clinical effects in treatment of bronchitis, pneumonia and sinusitis. This enzyme was isolated from B. sphaericus and single crystals were obtained by the hanging drop vapor diffusion method. The crystals belong to the monoclinic space group P2, with cell dimensions of a = 46.94 A, b = 64.55 A, c = 86.23 A and beta = 95.4 degrees. These crystals are mechanically strong, they are stable in the X-ray beam and they diffract to better than 1.8 A resolution. The cell dimensions are consistent with four molecules per unit cell and two molecules in the asymmetric unit. A complete native data set to 1.77 A resolution has been collected on a Rigaku R-AXIS-IIc Imaging Plate Detector system and a heavy-atom derivative search is presently in progress.

Amino Acid Sequence↗