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C Mohr

Publications and source records attributed to C Mohr.

At least 19 recordsLinked to original sources
PubMed1992

Posttranslational isoprenylation of rho protein is a prerequisite for its interaction with mastoparan and other amphiphilic agents.

The amphiphilic agents melittin, compound 48/80 and mastoparan inhibit ADP-ribosylation of porcine brain rho protein by Clostridium botulinum exoenzyme C3. However, ADP-ribosylation of recombinant rhoA expressed in E.coli was not inhibited by these agents. Accordingly, steady state GTP hydrolysis by recombinant rhoA was not stimulated by mastoparan, whereas GTP hydrolysis by porcine brain rho was stimulated 2.5-fold in the presence of this wasp venom. After microinjection of recombinant rhoA into Xenopus laevis oocytes the inhibitory effect of mastoparan on C3 ADP-ribosylation was restored. The data suggest that the amphiphilic agents tested are only active at the posttranslationally processed form of rho and that they exert their effects via the C-terminal end.

Adenosine Diphosphate Ribose↗
PubMed1992

Purification and characterization of an ADP-ribosyltransferase produced by Clostridium limosum.

We purified a novel ADP-ribosyltransferase produced by a Clostridium limosum strain isolated from a lung abscess and compared the exoenzyme with Clostridium botulinum ADP-ribosyltransferase C3. The C. limosum exoenzyme has a molecular weight of about 25,000 and a pI of 10.3. The specific activity of the ADP-ribosyltransferase is 3.1 nmol/mg/min with a Km for NAD of 0.3 microM. Partial amino acid sequence analysis of the tryptic peptides revealed about 70% homology with C3. The novel exoenzyme modifies selectively the small GTP-binding proteins of the rho family in human platelet membranes presumably at the same amino acid (asparagine 41) as known for C3. Recombinant rhoA and rhoB serve as substrates for C3 and the C. limosum exoenzyme. Whereas recombinant rac1 protein is only marginally ADP-ribosylated by C3 or by the C. limosum exoenzyme in the absence of detergent, in the presence of 0.01% sodium dodecyl sulfate rac1 is modified by C3 but not by the C. limosum exoenzyme. Recombinant CDC42Hs protein is a poor substrate for C. limosum exoenzyme and is even less modified by C3. The C. limosum exoenzyme is auto-ADP-ribosylated in the presence of 0.01% sodium dodecyl sulfate by forming an ADP-ribose protein bond highly stable toward hydroxylamine. The data indicate that ADP-ribosylation of small GTP-binding proteins of the rho family is not unique to C. botulinum C3 ADP-ribosyltransferase but is also catalyzed by a C3-related exoenzyme from C. limosum.

ADP Ribose Transferases↗
PubMed1992

ADP-ribosylation of rho proteins is inhibited by melittin, mast cell degranulating peptide and compound 48/80.

The amphiphilic agents melittin, mast cell degranulating peptide and compound 48/80 inhibit the ADP-ribosylation of the small GTP-binding proteins rho by Clostridium botulinum exoenzyme C3. Half-maximal and maximal inhibition (greater than 90%) of ADP-ribosylation occurred at about 8 and 25 micrograms/ml for compound 48/80, at 10 and 45 microM for mast cell degranulating peptide and at 15 and 50 microM for melittin, respectively. In addition, these compounds increase the steady state GTP hydrolysis and the association and dissociation rate of GTP-binding of rho proteins through an increase of GDP/GTP exchange. The data suggest that the amphiphilic agents tested interact with small GTP-binding proteins of the rho protein family.

ADP Ribose Transferases↗
PubMed1992

Coxsackievirus B3-induced production of tumor necrosis factor-alpha, IL-1 beta, and IL-6 in human monocytes.

Infections by coxsackievirus B3 (CVB3) have previously been shown to cause acute and chronic myocarditis characterized by a heavy mononuclear leukocyte infiltration and myocyte necrosis. Because clinical and experimental evidence suggested that cardiac damage may result from immunologic rather than viral mechanisms, we examined in this study the in vitro interaction of CVB3 with human monocytes. CVB3 was capable of infecting freshly harvested monocytes as revealed by immunofluorescence and release of infectious virus particles. Virus infection did not reduce monocyte viability but, on the contrary, enhanced spreading and adherence. In a dose-dependent manner, CVB3 stimulated the release of cytokines from monocytes. Whereas a potent production of TNF-alpha, IL-1 beta, and IL-6 was dependent on exposure to infectious CVB3, IFN release was also induced by UV-inactivated virus. On a molecular level, CVB3 stimulated cytokine gene expression as shown by a marked TNF-alpha, IL-1 beta, and IL-6 mRNA accumulation. Supernatants of CVB3-infected monocytes displayed cytotoxic activity against Girardi heart cells which could be abrogated by an anti-TNF-alpha antiserum. These data suggest that CVB3-induced cytokine release from monocytes may participate in virus-induced organ damage such as myocarditis, which may either occur by a direct cytotoxicity of cytokines or by activation of cytotoxic lymphocytes.

Cell Adhesion↗
PubMed1992

ADP-ribosylation by Clostridium botulinum C3 exoenzyme increases steady-state GTPase activities of recombinant rhoA and rhoB proteins.

ADP-ribosylation of recombinant rhoA and rhoB proteins by Clostridium botulinum C3 exoenzyme increased steady-state GTP hydrolysis by 50 to 80%. ADP-ribosylation and increase in GTP hydrolysis occurred at similar concentrations of C3, depended on the presence of NAD and were prevented by anti-C3 antibody or heat inactivation of C3. In contrast, GTP hydrolysis by Ile-41 rhoA or Ha-ras, which are no substrates for the transferase, were not affected by C3. ADP-ribosylation facilitated the [3H]GDP release and subsequently, the binding of [3H]GTP to rhoA. The data indicate that the increase in the steady-state GTPase activity by ADP-ribosylation is caused by increasing the rate of GDP release which is suggested to be the rate limiting step of the GTPase cycle of the small GTP-binding proteins.

ADP Ribose Transferases↗
PubMed1992

Clostridium botulinum C3 ADP-ribosyltransferase.

C3 and C3-like ADP-ribosyltransferases modify the low-molecular-mass GTP-binding proteins Rho and Rac. ADP-ribosylation occurs in asparagine-41, which is located in the putative effector region of these highly conserved regulatory proteins. First studies indicate that the Rho proteins are somehow involved in the regulation of cytoskeletal proteins, e.g., microfilament proteins. Although the precise mechanism of the interaction of the C3 substrate with cytoskeletal elements is unclear, it appears that the ADP-ribosylation by C3 renders the GTP-binding protein biologically inactive. Thus C3 and/or C3-like ADP-ribosyltransferases may be useful instruments with which to study the physiological functions of its eukaryotic substrates. Moreover, those studies may help to elucidate whether these exoenzymes are of pathophysiological and pathogenetic relevance in diseases caused by clostridia producing these agents.

ADP Ribose Transferases↗
PubMed1992

Prospective flow cytometric analysis of head and neck carcinomas. Prognostic relevance of DNA-content and S-fraction.

Flow cytometric data were obtained from 142 primary squamous cell carcinomas of the oral cavity or the oropharynx. Aneuploidy was found in 36.8% of the tumours. The DNA indices showed a significant correlation with the S-fraction, tumour size and evidence of suspicious lymphnodes. There was no clear correspondence between the S-fraction and the tumour stage. Tumour size, histopathologically-positive lymphnodes and the mode of treatment were significantly correlated with the survival rates. In contrast, there was no clear correlation between flow cytometric data and the prognosis of the whole group as well as several clinical subgroups. In 40 patients who received preoperative irradiation, DNA indices and S-fractions were compared before and after the preoperative treatment. In 12 of 14 aneuploid tumours irradiation led to a decrease in the DNA indices into the range of euploidy. Only 2 tumours remained aneuploid. After irradiation 26 of 37 tumours showed a decrease in S-fraction, 11 tumours showed an increase. Loss of aneuploidy after irradiation was associated with a histologically-proven increasing devitalization of tumour cells, decrease in S-fraction corresponded to a tendency to a better prognosis.

Adult↗
PubMed1992

Chemical distribution of glycosphingolipids in third-instar larval organs of the blowfly, Calliphora vicina (Insecta: Diptera).

As a first approach to testing the working hypothesis that glycosphingolipids are functionally involved in the ontogeny of insects, their chemical distribution in larval organs was determined and any stadium-correlated differences documented. Selected organs, i.e., the fatbody, striated muscle, intestinal tract, salivary glands, imaginal discs, and central nervous system, were dissected from seven-day-old larvae of the blowfly, Calliphora vicina, and their glycolipids isolated. Two-dimensional, high-performance thin-layer chromatography was used to separate the neutral and acidic glycolipids of each organ. Significantly different total glycolipid component-patterns were obtained for the individual organs, whereby, except for a number of additional uncharacterized components in the intestinal tract, the neutral glycolipids of all organs were found to be qualitatively similar. However, major quantitative differences between the selected organs were found in their total glycolipid-carbohydrate contents, as well as the respective quantitative neutral glycosphingolipid-component distributions. The acidic glycolipids showed pronounced qualitative as well as quantitative organ-dependent variations. Whereas the highest proportion of uncharged glycolipids was characteristic of the fatbody, a high proportion of zwitterionic glycolipid-components was observed to be typical of the central nervous system and imaginal discs, i.e., of organs persisting during larval life and throughout metamorphosis. Imaginal disc glycolipids were distinguished by their high content of acidic glycolipids, a putative reflection of the functional role of these glycoconjugates in regulated cell reorganization during metamorphosis.

Animals↗
PubMed1992

Enhanced release of prostaglandin E2 from macrophages of rats with silicosis.

The pathogenesis of silicosis results, in part, from interactions between silica particles and alveolar macrophages (AM) with release of cytokines and other mediators. Different arachidonic acid metabolites have been shown to promote or to suppress inflammation and fibrosis. We designed experiments to study the production of cyclooxygenase metabolites and tumor necrosis factor-alpha (TNF-alpha) from macrophages during active silicosis. Macrophages were harvested from rats 5 to 7 mo after an 8-day silica aerosol exposure. Upon in vitro culture of AM, the spontaneous release of prostaglandin E2 (PGE2), thromboxane B2 (TXB2), and prostaglandin D2 (PGD2) of silica-exposed animals was higher than that of sham-exposed animals. Moreover, AM from silicotic rats displayed an increased sensitivity to low concentrations of lipopolysaccharide (LPS, 10 ng/ml) and released copious amounts of PGE2 and TXB2. When compared with similarly enhanced release of TNF-alpha from AM of silica-exposed rats, PGE2 production occurred later and started to increase when TNF-alpha production declined. Addition of the cyclooxygenase blocker indomethacin augmented TNF-alpha production, whereas the addition of PGE2 counteracted TNF-alpha release. Also peritoneal macrophages, which did not have direct contact with silica particles, released enhanced levels of PGE2 in response to low LPS doses. We conclude that AM and other macrophages from silica-exposed rats are preactivated and display an enhanced prostanoid production that could serve anti-inflammatory or immunomodulating roles in silicosis.

Animals↗
PubMed1992

Reduced release of leukotrienes B4 and C4 from alveolar macrophages of rats with silicosis.

Silicosis leads to altered release of fibrogenic and immunomodulating mediators from alveolar macrophages (AM). Since 5-lipoxygenase metabolites have been shown to possess proinflammatory effects and to promote the release of cytokines such as tumor necrosis factor-alpha (TNF-alpha) from mononuclear phagocytes, we determined leukotriene secretion from silica-exposed AM. Rats were exposed to an aerosol of silica particles for 8 days and AM were harvested by bronchoalveolar lavage 5 to 7 mo after exposure. AM from both air-sham control and silica-exposed rats displayed minimal spontaneous leukotriene release upon in vitro culture. Stimulation with opsonized zymosan particles induced leukotriene B4 (LTB4) and leukotriene C4 (LTC4) secretion, which was much greater in control AM than in AM from silica-dusted rats. The reverse was found for zymosan-induced TNF-alpha production, which was higher in AM from silica-exposed than from control rats. To study the interrelation between leukotriene and TNF-alpha release, we incubated zymosan-stimulated AM with the 5-lipoxygenase inhibitor VZ 65. VZ 65 suppressed zymosan-induced TNF-alpha release from AM in a dose-dependent manner, and TNF-alpha production could be restored almost completely by addition of LTB4. These experiments demonstrate that silica exposure resulted in a decreased LTB4 and LTC4 production from AM, which may represent a regulatory mechanism to counterbalance enhanced TNF-alpha production during silicosis.

Animals↗
PubMed1992

[Phosphate concentration. Does reduction in infant formula feeding modify the micro-ecology of the intestine?].

The potential influence of phosphates in formulas on intestinal microflora was studied in 25 infants, aged 8 days to 12 weeks. The babies were either fed an infant formula with the usual phosphate concentration (n = 10) or an infant formula with reduced phosphate and protein concentrations (n = 7). The microbiological findings were compared with those obtained from breastfed infants (n = 8). Low-phosphate concentrations did not correlate with a predominance of bifidobacteria or suppression of putrefactive bacteria in the feces. The fecal excretion of phosphates and fat was found to be significantly lower with mother's milk compared to formulas both rich and poor in phosphate. Protein synthesis and breakdown rates, as well as the net protein gain, did not have a significant correlation with protein intake.

Bifidobacterium↗
PubMed1992

Host-microflora correlations in infant nutrition.

The intestinal microflora represents an enormous cell mass and has a high metabolic capacity. The symbiotic efficacy of these microbes in humans is still a matter of discussion. Of particular interest, from a biogenetic point of view, are potential symbiotic relations between the bifidobacterial microflora and the breast-fed infant. Our group has conducted studies related to this topic; they were aimed at determining the dimension of microbial assimilation by the host. Our studies with 15N-labeled bifidobacteria have shown that the bifidobacterial microflora is capable of upgrading nonessential nitrogen such as urea nitrogen for the synthesis of microbial protein. Oral single pulse labelings with 15N-labeled bifidobacteria were absorbed to approximately 90% and retained in the infant's protein pool to approximately 70%. These findings demonstrate the high intensity of the substrate flow from the microflora to the host. This might become important under conditions of marginal food protein intake or during periods of accelerated growth.

Animals↗
PubMed1991

Interaction of mastoparan with the low molecular mass GTP-binding proteins rho/rac.

Mastoparan, which has been shown to active G proteins, inhibits the ADP-ribosylation of 20 kDa human platelet membrane proteins catalyzed by Clostridium botulinum exoenzyme C3 half-maximally and maximally (90%) at 20 and 100 microM concentrations, respectively. Inhibition of ADP-ribosylation was enhanced by GTP-gamma S. Mastoparan increased GTP hydrolysis by porcine brain rho protein and stimulated GTP binding in a concentration dependent manner. The data suggest that mastoparan not only interacts with heterotrimeric G proteins but also with low molecular mass GTP-binding proteins of the rho/rac family.

ADP Ribose Transferases↗
PubMed1991

ADP-ribosylation and de-ADP-ribosylation of the rho protein by Clostridium botulinum exoenzyme C3. Regulation by EDTA, guanine nucleotides and pH.

Pretreatment of rho protein purified from pig brain cytosol with EDTA (3 mM) for 10 min at 30 degrees C inhibited its ADP-ribosylation by Clostridium botulinum C3 ADP-ribosyltransferase by more than 90%. The EDTA effect was not caused by alteration of C3. GDP or GDP beta S present during the pretreatment period completely prevented the decrease in ADP-ribosylation with half-maximal and maximal effects at 3 and 300 microM, respectively. GTP or GTP gamma S were less efficacious in preventing the decrease in ADP-ribosylation, but were more potent (half-maximal and maximal effects at 0.1 and 3 microM, respectively). [32P]ADP-ribose incorporated in pig brain rho by C3 was de-ADP-ribosylated by the enzyme in the presence of nicotinamide and at low pH. Concomitantly, [32P]NAD was formed. The pH optima for ADP-ribosylation and de-ADP-ribosylation were pH 7.5 and 5.5, respectively. De-ADP-ribosylation was most efficient with nicotinamide, less effective with 3-acetylpyridine and not observed with 3-aminopyridine, 4-aminopyridine, 4-acetylpyridine and isonicotinic acid. As observed for the ADP-ribosylation, the de-ADP-ribosylation by C3 was maximal with the GDP-bound form of rho and blocked after EDTA treatment.

ADP Ribose Transferases↗
PubMed1991

Long-term treatment effects in patients with bilateral retinoblastoma: ocular and mid-facial findings.

A total of 99 patients with bilateral retinoblastoma who had been treated between 1965 and 1982 were reexamined in April 1988 to study the late effects of treatment. Their median age at the follow-up visit in 1988 was 16 years (range, 6-27 years), and the median follow-up was 15 years (range, 6-26 years). All patients underwent a full eye examination, morphometric measurements of the mid-face and genetic counselling. Each eye or orbit and the corresponding side of the patient's mid-face were evaluated separately, resulting in 198 data sets from 99 individuals. Subjects were divided into four treatment groups according to whether photo- and cryo-coagulation, enucleation, radiation therapy or various combinations thereof were used. In all, 81 eyes had a visual acuity of greater than 0.4 (in 23 of these, however, only with low-vision aids). Within a dose range of 36-51 Gy, the location of the tumor (36%) or cataract (15%) were the main factors responsible for poor visual acuity, whereas radiation retinopathy and/or optic neuropathy occurred in only three cases. Cataracts were more frequently observed following orthovoltage as compared with megavoltage therapy (P = 0.012). A total of 72 eyes had been enucleated and had not received radiation therapy at any time. Cosmetic results (as measured by several parameters) in these cases were significantly better then those in 28 subjects who underwent combined radiation therapy and enucleation. As defined by various subjective as well as objective findings, mid-facial hypoplasia occurred significantly more often following orthovoltage as compared with megavoltage therapy.

Adolescent↗
PubMed1991

Symbiotic interactions between colonic microflora and protein metabolism in infants.

The utilization of 15N nitrogen from 15N-labelled bifidobacteria for whole body protein synthesis was studied in 4 infants by oral single-pulse labellings and in 3 other infants, who had colostomies, by colonic pulse labellings. The bifidobacteria were harvested from a modified Petuely culture medium containing 15N ammonium chloride and 15N cystine as the only sources of nitrogen. The tracer dose chosen for the balance studies was 3 mg 15N/kg. 15N concentrations in urine and feces collected over 48 hours after the pulse labellings were determined by emission spectrometry. Oral administration of 15N-labelled bifidobacteria resulted in absorption of approximately 90% renal excretion of 15%, and fecal excretion of 12% of the tracer dose, respectively. Retention in the protein pool averaged 73%. After colonic single pulse labelling with 15N-labelled bifidobacteria, the corresponding values were 85.5%, 2.2%, 14.5% and 83.0%, respectively. Absorption and incorporation of the heavy nitrogen into body proteins were directly demonstrated by increased 15N atom percent excess values within the trichloroacetic acid (TCA) supernatants and the proteins of the plasma, 0.25 and 0.04 atom%, respectively, at 24 hours after oral pulse labellings. One half of the total 15N excreted in urine consisted of urea and approximately 8% was eliminated as ammonia.

Bifidobacterium↗
PubMed1991

Systemic macrophage stimulation in rats with silicosis: enhanced release of tumor necrosis factor-alpha from alveolar and peritoneal macrophages.

In silicosis, alveolar macrophages (AM) are thought to induce chronic inflammation and fibrosis by release of cytokines. Rats were exposed to aerosols of alpha-quartz and examined 4 to 9 mo later for persistence of silica particles and release of tumor necrosis factor-alpha (TNF-alpha) from macrophages. Silica particles were detected in AM, lung parenchyma, and thoracic lymphoid organs, whereas extrathoracic lymphoid tissues and organs were free of the mineral. When AM were tested functionally, no spontaneous release of TNF-alpha was observed. However, upon in vitro stimulation of AM from silicotic rats with a low concentration of lipopolysaccharide (10 ng/ml), abundant TNF-alpha production was found that was higher and occurred more rapidly than with AM from sham-exposed animals. Peritoneal macrophages, which did not have contact with silica particles, displayed a similarly enhanced TNF-alpha release in response to low doses of lipopolysaccharide. These data demonstrate a state of systemic preactivation ("priming") of macrophages that supports the notion that silicosis is associated with a general immunostimulation.

Animals↗