Biomedical subjects

S Ullrich

Publications and source records attributed to S Ullrich.

At least 55 records · Page 3Linked to original sources

PubMed1996

[Effect of strabismus operation of corneal topography].

BACKGROUND: In order to determine the short- and long-term influence of strabismus surgery on corneal curvature, a prospective study was carried out measuring corneal topography before and after operation. PATIENTS AND METHODS: Corneal topography was performed using a computer assisted videokeratoscope. 77 eyes of 74 patients were examined 1 day before and 1 day as well as 3 months after surgery. Data of the semimeridians at 0 degree, 90 degrees, 180 degrees and 270 degrees in the 3-, 5- and 7-mm zone and of the corneal center were analyzed. Objective refraction, induced astigmatism and simulated keratometer reading were evaluated. 39 horizontal recess-resect procedures. 12 inferior rectus recessions, 10 horizontal resections. 10 inferior oblique recessions and 6 other procedures were performed. RESULTS: The spheric equivalent of objective refraction decreased by 0.23 D. The absolute astigmatism increased by 0.16 D, the maximum change was 1 D. Changes of objective refraction were statistically not significant. The simulated keratometer reading increased by 0.2 D postoperatively and returned to the initial value after 3 months. With few exceptions, corneal topographic changes were small, statistically not significant and nearly disappeared after 3 months. Corneal flattening tended to occur in the semimeridian of resection while corneal steepening was observed at the site of recession. CONCLUSIONS: The influence of strabismus surgery on corneal astigmatism is usually small and mostly transitory. In a few cases, however, the induced astigmatism persists. Patients should be informed about this possibility preoperatively.

Adolescent↗

PubMed1996

Toxic effects on bacterial metabolism of the redox dye 5-cyano-2,3-ditolyl tetrazolium chloride.

The monotetrazolium redox dye 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) has been used as a vital stain of actively respiring bacteria for several years. In this study, inhibitory effects on bacterial metabolism of this redox dye have been examined in a brackish water environment (Kiel Fjord, Germany) and a freshwater environment (Elbe River, Germany). As the results from time series experiments (1 to 10 h) show, bacterial growth and respiration of the investigated natural communities were clearly reduced by CTC supply. Compared with untreated controls (100%), CTC-treated samples showed distinctly lower heterotrophic bacterial plate counts (0 to 24 and 11.8 to 23.7%, respectively), bacterial production (0.9 to 14.1 and 1.1 to 9.6%, respectively), bacterial respiration (4.1 to 9.4 and 6.8 to 43.8% for several concentrations of (sup14)C-labeled glucose), and [(sup14)C]glucose incorporation (0.2 to 4.2%). Additionally, toxicity of CTC was demonstrated by luminescence in a Microtox bioassay. CTC concentrations of 0.1 and 5.0 (mu)M required only 15 min for decreases of approximately 50 and 100%, respectively. The suppression of CTC on several bacterial metabolic processes suggests that determination by the CTC technique underestimates the actual number of active cells distinctly. This conclusion is confirmed by the comparison of generation times calculated on the basis of thymidine uptake data and active bacterial counts determined by the CTC assay and microautoradiography. While unrealistic short generation times (0.5 to 5 h) resulted from the CTC assay, the generation times calculated according to microautoradiography ranged within values (7 to 21 h) reported elsewhere for comparable aquatic environments. The inhibitory effect of CTC demonstrated in our experiments is an aspect with regard to the application of this tetrazolium dye for the estimation of active bacteria in natural aquatic environments which hitherto has not been considered.

Journal Article↗

PubMed1996

Postreceptor signalling of growth hormone and prolactin and their effects in the differentiated insulin-secreting cell line, INS-1.

Signal transduction of two mitogens for pancreatic beta-cells, GH and PRL, was investigated using the differentiated insulin-secreting cell line, INS-1. Addition of human GH (hGH) or ovine PRL in a serum-substitute medium increased growth, insulin content, and nutrient metabolism evaluated by tetrazolium salt reduction. hGH, bovine GH (bGH), and PRL also stimulated [3H]thymidine incorporation in a dose-dependent manner (1 pM - 1 nM). hGH induced cytosolic Ca2+ ([Ca2+]i) rises, which were transient, dependent on the presence of extracellular Ca2+, blocked by verapamil, calciseptine, and the hyperpolarizing agent diazoxide, suggesting that hGH stimulates Ca(2+)-influx through L-type Ca(2+)-channels. Similar effects on [Ca2+]i were observed with bGH or PRL. hGH caused membrane depolarization in a small proportion of the cells ( < 25%) as detected by cell-attached patch-clamp analysis. However, hGH failed to stimulate acute insulin secretion. hGH, bGH, and PRL promoted tyrosine phosphorylation of JAK2 tyrosine kinase. Verapamil inhibited neither [3H]thymidine incorporation nor JAK2 phosphorylation stimulated by hGH, whereas a tyrosine kinase inhibitor, lavendustin A, blocked the mitogenic effect. Involvement of cAMP is suggested because Rp-cyclic adenosine-3', 5'-monophosphorothioate, a competitive inhibitor of protein kinase A, abolished hGH-induced [Ca2+]i rises and DNA synthesis. cAMP appears to play a permissive role, although hGH failed to raise cellular cAMP levels. These results support the idea that activation of JAK2 is a major signaling event, whereas the [CA2+]i rise is not a prerequisite, for the mitogenic effects of GH and PRL in insulin-secreting cells.

Animals↗

PubMed1995

Adequate connexin-mediated coupling is required for proper insulin production.

To assess whether connexin (Cx) expression contributes to insulin secretion, we have investigated normal and tumoral insulin-producing cells for connexins, gap junctions, and coupling. We have found that the glucose-sensitive cells of pancreatic islets and of a rat insulinoma are functionally coupled by gap junctions made of Cx43. In contrast, cells of several lines secreting insulin abnormally do not express Cx43, gap junctions, and coupling. After correction of these defects by stable transfection of Cx43 cDNA, cells expressing modest levels of Cx43 and coupling, as observed in native beta-cells, showed an expression of the insulin gene and an insulin content that were markedly elevated, compared with those observed in both wild-type (uncoupled) cells and in transfected cells overexpressing Cx43. These findings indicate that adequate levels of Cx-mediated coupling are required for proper insulin production and storage.

Animals↗

PubMed1994

Topography of mammalian connexins in human skin.

We have explored the expression of gap junction proteins in normal human skin by immunostaining cryostat sections (indirect immunofluorescence) or lyophilized epidermis (Western blotting) with antibodies against four mammalian connexins Cx26, Cx32, Cx40, Cx43; and by hybridizing total epidermal RNA (Northern blotting) with cRNA probes for Cx26, Cx32, and Cx43. We found that epidermal keratinocytes express Cx43 but not Cx26, Cx32, or Cx40. This expression was minimal in the basal layer, much higher in the spinous layer, reduced in the granular layer, and absent in the stratum corneum. Immunostaining for Cx43 was also observed in sebaceous glands, hairs, and eccrine sweat ducts. The two latter epidermal adnexae were also markedly labeled by antibodies against Cx26, a gap junction protein that was undetectable by immunofluorescence in interfollicular keratinocytes. Immunoblots of polyacrylamide gel electrophoresis-separated epidermal proteins and hybridization of epidermal RNA confirmed the presence of Cx43 in epidermis. These observations indicate that 1) Cx43 and Cx26 are components of human keratinocyte gap junctions; 2) these two proteins are differentially expressed in the interfollicular epidermis and the skin adnexae; 3) in interfollicular epidermis, Cx43 is a predominant gap junction protein, mostly expressed by the differentiating spinous cells; 4) Cx43 distribution is in accordance with the extensive dye coupling previously observed in this epidermal compartment.

Animals↗

PubMed1994

[Erythrocyte deformability in pregnancy-induced hypertension].

Erythrocyte deformability and red blood cells characteristics (MCV, MCH, Hct) were studied in 18 patients with gestational hypertension (24 normotensive primigravidae and 20 non-pregnant nulliparous women). The deformability of red cells was determined by red cell filtration in a filtrometer MF4 after prefiltration through cotton wool. We found a statistically reduced deformability in patients with gestational hypertension compared with normal pregnancy and non pregnant controls. Our data suggest a strong correlation between red cell filterability and newborn weight (r = 0.59, p < 0.02). The deformability of erythrocytes in gestational hypertension mainly depends on the fluidity of the cell membrane (lipid contents). Other factors of minor importance are the hemoglobin viscosity and the cell membrane surface area/cell volume ratio. The significantly lower erythrocyte fluidity in patients with gestational hypertension may also be explained by an enlarged metabolic pool of free calcium ions in these red blood cells.

Birth Rate↗

PubMed1992

Characterization of small-molecular-mass guanine-nucleotide-binding regulatory proteins in insulin-secreting cells and PC12 cells.

The distribution of ras-related small-molecular-mass guanine-nucleotide-binding regulatory proteins (SMG) of two insulin-secreting cell lines, RINm5F and HIT-T15, and of a catecholamine-secreting cell line, PC12, have been studied using different techniques. About ten such proteins were detected by [32P]GTP binding after two-dimensional gel electrophoresis and transfer to nitrocellulose membranes. In insulin-secreting cells, rho protein(s) that cannot be detected with the GTP-binding technique were identified by ADP ribosylation with Clostridium botulinum C3 exoenzyme. After subcellular fractionation, SMG displayed specific distributions. The insulin-secreting cell line RINm5F and the catecholamine-secreting cell line PC12 expressed a similar set of these proteins with analogous localization. [32P]GTP binding analysis revealed that at least seven SMG were associated with the secretory granule enriched fraction of RINm5F cells and with the fraction containing dense secretory granules from PC12 cells, proteins of 27 (pI 5.4), 23 (pI 6.8) and 25 kDa (pI 6.7) being the most abundant. These proteins were present in a highly purified granule fraction of a solid rat insulinoma. The 23 kDa (pI 6.8) and 25 kDa (pI 6.7) proteins, but not the protein migrating at 27 kDa (pI 5.4), were detected in the corresponding fraction from HIT-T15 cells. A monoclonal antibody directed against smg25A/rab3A recognized the SMG in secretory granules migrating at 25 kDa (pI 6.7) and 27 kDa (pI 5.4). This antibody also revealed the presence of such protein(s) in homogenates of rat pancreatic islets. During stimulation of insulin secretion of either intact or permeabilized cells, there was no detectable redistribution to the cytosol or to the plasma membrane of the major proteins located on secretory granules. In view of the invariable presence of at least two of the SMG in granules of secretory cells, these proteins are good candidates for regulation of hormone secretion.

Adenosine Diphosphate Ribose↗

PubMed1992

Urocanic acid isomers, immunosuppressive cytokines and the induction of human immunodeficiency virus.

The ability of cis-urocanic acid to mimic the effects of ultraviolet (UV) was tested in two systems that show cellular responses to direct UV irradiation. First, cultured mouse keratinocytes were treated with cis-urocanic acid and the cell culture supernatants were injected into mice to test for the ability to block spleen cell proliferation in the mixed lymphocyte reaction. Second, human fibroblasts carrying the chloramphenicol acetyltransferase gene under the control of the human immunodeficiency virus (HIV) long terminal repeat promoter were tested for the ability of cis-urocanic acid to induce gene expression. In these tests cis-urocanic acid did not induce a response comparable with UV irradiation alone, although at toxic concentrations cis-UCA did induce low expression from the viral promoter. These data suggest that, unlike UVB radiation, cis-urocanic acid does not activate keratinocytes to produce immunosuppressive cytokines nor does it induce expression of the HIV promoter.

Animals↗

PubMed1991

p53 mutations, ras mutations, and p53-heat shock 70 protein complexes in human lung carcinoma cell lines.

The p53 tumor suppressor gene is frequently mutated and the K-ras oncogene is occasionally mutated in primary specimens of human lung carcinomas. These mutated genes also cooperate in the immortalization and neoplastic transformation of rodent cells. To determine whether these mutations are necessary for maintenance of the immortalized and/or neoplastically transformed states of human bronchial epithelial cells, the p53 gene and regions of the ras (K-, H-, and N-) genes were sequenced in nine human lung carcinoma cell lines. Detection of p53 mutations by polymerase chain amplification and direct DNA sequencing was corroborated by p53 immunocytochemistry and coimmunoprecipitation of p53 with heat shock protein 70. p53 and ras genes were frequently, but not always, mutated in the carcinoma cell lines. These data are consistent with the hypothesis that multiple genetic changes involving both protooncogenes and tumor suppressor genes occur during lung carcinogenesis.

Base Sequence↗

PubMed1991

Redistribution of ADP-ribosylation factor during stimulation of permeabilized cells with GTP analogues.

Low-molecular-mass GTP-binding proteins of the ras family were analysed by [32P]GTP binding after PAGE and transfer to nitrocellulose membranes. By this technique, several GTP-binding proteins in the 20-30 kDa range were detected in both cytosolic and microsomal fractions of RINm5F cells. One of these, displaying an apparent molecular mass of about 20 kDa and a pI of 6.7, was mainly cytosolic and was shown to be the ADP-ribosylation factor (ARF) by using specific antibodies. When permeabilized RINm5F cells were incubated with the stable GTP analogues guanosine 5'-[gamma-thio]triphosphate (GTP[S]) and guanosine 5'-[beta gamma-imido]triphosphate (p[NH]ppG) the amount of ARF increased in a fraction containing both Golgi and plasma-membrane markers, but not in the fraction containing secretory granules, mitochondria and lysosomes. GTP, GDP and its beta-thio analogue did not enhance ARF binding to membranes, smg25/rab3 and rho, as well as all the other small GTP-binding proteins detected by the [32P]GTP binding, did not redistribute under these conditions. As GTP[S] stimulates insulin secretion in these cells, we also examined the relationship between ARF translocation and insulin secretion. Both phenomena were elicited by GTP[S] with an EC50 (median effective concentration) of about 10 microM. p[NH]ppG was equipotent with GTP[S] in inducing insulin secretion (EC50 about 10 microM), but higher concentrations (about 500 microns) were required to achieve the same maximal ARF redistribution. These results suggest that: (1) ARF is subject to cycling between a membrane-associated and a free/loosely attached form, determined by the species of bound guanine nucleotide; (2) ARF alone does not seem to regulate exocytosis in insulin-secreting cells.

ADP-Ribosylation Factors↗

PubMed1990

Potentiation of stimulus-induced insulin secretion in protein kinase C-deficient RINm5F cells.

The role of protein kinase C (PKC) in stimulus recognition and insulin secretion was investigated after long-term (24 h) treatment of RINm5F cells with phorbol 12-myristate 13-acetate (PMA). Three methods revealed that PKC was no longer detectable, and PMA-induced insulin secretion was abolished. Such PKC-deficient cells displayed enhanced insulin secretion (2-6-fold) in response to vasopressin and carbachol (activating phospholipase C) as well as to D-glyceraldehyde and alanine (promoting membrane depolarization and voltage-gated Ca2+ influx). Insulin release stimulated by 1-oleoyl-2-acetylglycerol (OAG) was also greater in PKC-deficient cells. OAG caused membrane depolarization and raised the cytosolic Ca2+ concentration ([Ca2+]i), both of which were unaffected by PKC down-regulation. Except for that caused by vasopressin, the secretagogue-induced [Ca2+]i elevations were similar in control and PKC-depleted cells. The [Ca2+]i rise evoked by vasopressin was enhanced during the early phase (observed both in cell suspensions and at the single cell level) and the stimulation of diacylglycerol production was also augmented. These findings suggest more efficient activation of phospholipase C by vasopressin after PKC depletion. Electrically permeabilized cells were used to test whether the release process is facilitated after long-term PMA treatment. PKC deficiency was associated with only slightly increased responsiveness to half-maximally (2 microM) but not to maximally stimulatory Ca2+ concentrations. At 2 microM-Ca2+ vasopressin caused secretion, which was also augmented by PMA pretreatment. The difference between intact and permeabilized cells could indicate the loss in the latter of soluble factors which mediate the enhanced secretory responses. However, changes in cyclic AMP production could not explain the difference. These results demonstrate that PKC not only exerts inhibitory influences on the coupling of receptors to phospholipase C but also interferes with more distal steps implicated in insulin secretion.

Alanine↗

PubMed1990

Somatostatin inhibition of Ca2(+)-induced insulin secretion in permeabilized HIT-T15 cells.

Somatostatin inhibited Ca2(+)-induced insulin secretion in permeabilized HIT-T15 cells, albeit with decreased sensitivity relative to intact cells. The inhibitory action required the presence of GTP, whereas GDP could not substitute for GTP. Pertussis-toxin treatment before cell permeabilization abolished the inhibition of secretion. Thus somatostatin, by activating a G-protein, interferes with exocytosis distal to the generation of soluble intracellular messengers.

Animals↗

PubMed1990

Carcinoembryonic antigen enhances metastatic potential of human colorectal carcinoma.

Patients with human colorectal carcinoma have a poor prognosis when serum carcinoembryonic antigen level exceeds 5 ng/mL. The hypothesis that carcinoembryonic antigen enhances metastasis by promoting the attachment of tumor cells to Kupffer cells and hepatocytes was tested in an experimental metastasis model in which colorectal carcinoma cells were injected into the spleens of BALB/c athymic nude mice and liver colonies counted 5 weeks later. Pretreatment with systemic injections of carcinoembryonic antigen significantly increased the metastatic potential of a poorly metastatic colorectal carcinoma cell line KM-12c, but did not induce the nonmetastatic colorectal carcinoma cell line HC 2998 to produce metastases, nor did carcinoembryonic antigen make the highly metastatic colorectal carcinoma cell line mHC 1410 more metastatic. Carcinoembryonic antigen did not stimulate proliferation of colorectal carcinoma but appeared to be a cofactor for metastasis possibly as an adhesion factor.

Animals↗

PubMed1990

Somatostatin inhibition of hormone release: effects on cytosolic Ca++ and interference with distal secretory events.

In normal pituitary cells somatostatin (SRIF) blocks the spontaneous oscillations in [Ca++]i by inhibiting the generation of action potentials. This is sufficient to explain the inhibitory effect on basal, but not entirely that on stimulated pituitary hormone secretion. In insulin secreting cells, which, in contrast to pituitary cells, only fire action potentials on stimulus-evoked depolarization, SRIF hyperpolarization and lowering of [Ca++]i is only transient. The marked inhibition of insulin secretion is suggested to be due to a coordinated action of SRIF on membrane potential and [Ca++]i as well as a direct interference with late secretory events.

Animals↗

PubMed1989

Different requirements for protein kinase C activation and Ca2+-independent insulin secretion in response to guanine nucleotides. Endogenously generated diacylglycerol requires elevated Ca2+ for kinase C insertion into membranes.

Electrically permeabilized RINm5F cells were used to assess the factors required for activation of protein kinase C (PKC) and insulin secretion. PKC was activated either by phorbol 12-myristate 13-acetate (PMA) or by the generation of endogenous diacylglycerol in response to the nonhydrolyzable guanine nucleotide analog guanosine 5'-O-(thiotriphosphate) (GTP gamma S). As shown previously, both PMA and GTP gamma S elicit Ca2+-independent insulin secretion. This effect was mimicked by guanyl-5'-yl imidodiphosphate (Gpp(NH)p) but not by guanosine 5'-O-(3-fluorotriphosphate) and guanosine 5'-O-(3-phenyltriphosphate) possessing only one negative charge in the gamma-phosphate group. The action of PMA was mediated by PKC, since the agent caused both phosphorylation of specific protein substrates and association of the enzyme with cellular membranes. This translocation was independent of the Ca2+ concentration employed. In contrast, GTP gamma S only promoted association of PKC with membranes at 10(-6) and 10(-5) M Ca2+ and failed to alter significantly protein phosphorylation in the absence of Ca2+. Neither Gpp(NH)p, which stimulates insulin release, nor the other two GTP analogs, increased the proportion of PKC associated with membranes. To verify that the Ca2+-dependent effect of GTP gamma S on PKC is due to activation of phospholipase C, we measured the generation of diacylglycerol. GTP gamma S indeed stimulated diacylglycerol production in the leaky cells by about 50% at Ca2+ concentrations between 10(-7) and 10(-5) M, an effect which was almost abolished in the absence of Ca2+. Thus, at 10(-7) M Ca2+, the concentration found in resting intact cells, the generated diacylglycerol was not sufficient to cause PKC insertion into the membrane, demonstrating that both elevated Ca2+ and diacylglycerol are necessary for translocation to occur. It is concluded that while PKC activation by PMA elicits Ca2+-independent insulin secretion, the kinase seems not to mediate the stimulatory action of GTP analogs in the absence of Ca2+.

Animals↗

PubMed1989

Galanin inhibits insulin secretion by direct interference with exocytosis.

Electrically permeabilized RINm5F cells were used to study whether galanin inhibits insulin secretion distally to the generation of soluble second messengers. Ca2+-induced insulin secretion was inhibited by the neuropeptide in a dose-dependent manner. Galanin appears to act via a G-protein as pertussis toxin treatment abolished the effect. GTP (100 microM), GDP (100 microM) and a low dose of GTP gamma S (10 microM) did not affect galanin-mediated inhibition of secretion. In contrast, at 100 microM, GTP gamma S attenuated and GDP beta S abolished the effect of the peptide. We conclude that galanin inhibits exocytosis directly by a mechanism involving a G-protein.

Calcium↗

PubMed1989

Evolutionary conservation of the biochemical properties of p53: specific interaction of Xenopus laevis p53 with simian virus 40 large T antigen and mammalian heat shock proteins 70.

We have investigated the biochemical properties of Xenopus laevis p53. With an in vitro binding assay, we can detect a specific association between X. laevis p53 and simian virus 40 large T antigen. Furthermore, X. laevis p53 expressed in monkey COS cells is stably associated with this viral antigen. Like mammalian p53, X. laevis p53 in complex with simian virus 40 large T antigen exhibits a 20-fold increase of its half-life. On the other hand, X. laevis p53 is unable to associate either in vivo or in vitro with adenovirus type 5 E1B 55-kilodalton protein. We show by an immunological technique that X. laevis p53 forms specific complexes with mammalian hsp72 and hsp73 heat shock proteins only at a temperature well above the optimal growth temperature for X. laevis. Our results suggest that the protein-binding properties of p53 are closely related to the functional activity of the protein.

Animals↗

PubMed1989

Characterization of alpha 2-adrenoceptors in a plasma membrane enriched fraction from the insulin-secreting cell line RINm5F.

A plasma membrane enriched fraction from the insulin-secreting cell line RINm5F was used to characterize [3H]clonidine binding. After a single self-generating Percoll gradient, the specific activity of 5'-nucleotidase (a plasma membrane marker) of the membrane fraction was enriched about 8-fold over that of the homogenate and nearly 30% of the total amount was recovered. The fraction was essentially free of mitochondria and secretory granules. [3H]clonidine binding to this membrane fraction revealed a single, high affinity binding site with a Kd of 2.3 nmol/l. The binding was competitively inhibited by adrenergic agonists in the following order of potency: clonidine greater than epinephrine greater than phenylephrine greater than isoproterenol, and by antagonists in the order of potency: idazoxan greater than yohimbine greater than propranolol greater than prazosin. Pertussis toxin pretreatment of the cells did not alter the inhibition of [3H]clonidine binding by epinephrine and clonidine nor the estimated receptor number for [3H]clonidine. In conclusion, the pharmacologic characteristics of [3H]clonidine binding sites on a plasma membrane enriched fraction from insulin-secreting RINm5F cells demonstrate that the receptor is of the alpha 2-adrenergic subtype.

Adrenergic alpha-Agonists↗