Biomedical subjects

G Wolf

Publications and source records attributed to G Wolf.

At least 325 records · Page 18Linked to original sources

PubMed1996

[The "other" parvovirus: first description of the minute virus of canines (Canine parvovirus type 1) in Germany].

During an investigation of a late abortion in a Yorkshire terrier minute virus of canines (MVC) antigen could be demonstrated in fetal tissues by immunofluorescence. The bitch had a high specific anti-MVC serum titer when tested about four weeks after the abortion. Those results implicate an etiological role of MVC in this abortion and to our knowledge it presents the first described case of a MVC-associated abortion in Germany.

Abortion, Veterinary↗

PubMed1996

From converting enzyme inhibition to angiotensin II receptor blockade: new insight on angiotensin II receptor subtypes in the kidney.

Since the discovery of renin, almost 100 years ago, all the components of the renin-angiotensin system have been characterized on a molecular level. Angiotensin II (Ang II) receptors can be grouped in two classes: AT1 and AT2 receptors. In addition to these receptor subtypes, several other Ang-II-binding sites with different properties have been identified. The majority of Ang II receptors in the kidney comprises the AT1 type, whereas AT2 receptors are only expressed by distinct structures such as the renal capsule and the juxtaglomerular apparatus. The vast majority of physiological functions of angiotensin II in the kidney are mediated through AT1 receptors. Important exceptions may be the pressure-induced natriuresis and chemotaxis for macrophages/ monocytes, as well as growth-suppressive effects which may be mediated by AT2 receptors.

Angiotensin Receptor Antagonists↗

PubMed1996

Funding nursing education: the Medicare dilemma. Interview by Cheryl Slagle King.

Comprehensive analysis of current Medicare funding for hospital-based diploma programs is multi-factorial, and must incorporate a market of constrained costs, impending Medicare Reform and emerging opportunities for APNs. In addition, consideration must be given to fundamental issues surrounding all aspects of nursing education. APNQ interviews Dr. Carol A. Anderson and Dr. Gail Wolf who make thought-provoking points in arguments covering a spectrum of nursing issues.

Education, Nursing, Diploma Programs↗

PubMed1995

PTB domains of IRS-1 and Shc have distinct but overlapping binding specificities.

PTB domains are non-Src homology 2 (SH2) phosphotyrosine binding domains originally described in the receptor tyrosine kinase substrate, Shc. By serial truncation, we show that a 174-residue region of Shc p52 (33-206) has full PTB activity. We also show that a 173-residue region of insulin receptor substrate-1 (IRS-1; residues 144-316) has related PTB activity. In vitro both domains bind directly to activated insulin receptors. Binding is abrogated by substitution of Tyr-960 and selectively inhibited by phosphopeptides containing NPXY sequences. Phosphopeptide assays developed to compare PTB domain specificities show that the Shc PTB domain binds with highest affinity to psi XN beta 1 beta 2 pY motifs derived from middle T (mT), TrkA, ErbB4, or epidermal growth factor receptors (psi = hydrophobic, beta = beta-turn forming); the IRS-1 PTB domain does not bind with this motif. In contrast, both the Shc and IRS-1 PTB domains bind psi psi psi XXN beta 1 beta 2pY sequences derived from insulin and interleukin 4 receptors, although specificities vary in detail. Shc and IRS-1 are phosphorylated by distinct but overlapping sets of receptor-linked tyrosine kinases. These differences may be accounted for by the inherent specificities of their respective PTB domains.

3T3 Cells↗

PubMed1995

L-O-(2-malonyl)tyrosine: a new phosphotyrosyl mimetic for the preparation of Src homology 2 domain inhibitory peptides.

Inhibition of Src homology 2 (SH2) domain-binding interactions affords one potential means of modulating protein-tyrosine kinase-dependent signaling. Small phosphotyrosyl (pTyr)-containing peptides are able to bind to SH2 domains and compete with larger pTyr peptides or native pTyr-containing protein ligands. Such pTyr-containing peptides are limited in their utility as SH2 domain inhibitors in vivo due to their hydrolytic lability to protein-tyrosine phosphatases (PTPs) and the poor cellular penetration of the ionized phosphate moiety. An important aspect of SH2 domain inhibitor design is the creation of pTyr mimetics which are stable to PTPs and have reasonable bioavailability. To date, most PTP-resistant pTyr mimetics which bind to SH2 domains are phosphonates such as (phosphonomethyl)phenylalanine (Pmp, 2), [(monofluorophosphono)methyl]phenylalanine (FPmp, 3) or [(difluorophosphono)methyl]-phenylalanine (F2Pmp, 4). Herein we report the incorporation of a new non-phosphorus-containing pTyr mimetic, L-O-(2-malonyl)tyrosine (L-OMT, 5), into SH2 domain inhibitory peptides using the protected analogue L-N alpha-Fmoc-O'-(O",O"-di-tert-butyl-2-malonyl)tyrosine (6) and solid-phase peptide synthesis techniques. Five OMT-containing peptides were prepared against the following SH2 domains: the PI-3 kinase C-terminal p85 SH2 domain (Ac-D-(L-OMT)-V-P-M-L-amide, 10, IC50 = 14.2 microM), the Src SH2 domain (Ac-Q-(L-OMT)-E-E-I-P-amide, 11, IC50 = 25 microM, and Ac-Q-(L-OMT)-(L-OMT)-E-I-P-amide, 14, IC50 = 23 microM), the Grb2 SH2 domain (Ac-N-(L-OMT)-V-N-I-E-amide, 12, IC50 = 120 microM), and the N-terminal SH-PTP2 SH2 domain (Ac-L-N-(L-OMT)-I-D-L-D-L-V-amide, 13, IC50 = 22.0 microM). These results show that peptides 10, 11, 13, and 14 have reasonable affinity for their respective SH2 domains, with the IC50 value for the SH-PTP2 SH2 domain-directed peptide 13 being equivalent to that previously observed for the corresponding F2Pmp-containing peptide. OMT may afford a new structural starting point for the development of novel and useful SH2 domain inhibitors.

Amino Acid Sequence↗

PubMed1995

Localization of NADPH-diaphorase/nitric oxide synthase in the rat retina: an electron microscopic study.

The activity of NADPH-diaphorase (NADPH-d), a marker for nitric oxide synthase (NOS), was examined histochemically in the rat and mice retina. Mice in which the neuronal NOS gene has been disrupted (nNOS- mice) were used for specificity controls. Light microscopically a few amacrine cells were heavily stained. Other cells were stained weakly or not at all. Under the electron microscope, formazan precipitates were detectable on membranes of endoplasmic reticulum, nuclear envelope, mitochondria, and, in a few cases, the Golgi complex. Bipolar, horizontal, and Müller cells, were if at all, sparsely labeled with formazan. Labeled mitochondria were observed in rod endings and in inner segments of photoreceptors. Outer segments of photoreceptors and ganglion cells were completely free of reaction product. The NADPH-d reaction in wild-type mice displayed a similar distribution pattern to that in rats. Retinae of nNOS- mice showed a complete lack of prominent NADPH-d stained (amacrine) cells. None or a very few labeled membranes were seen.

Animals↗

PubMed1995

Cyclosporine stimulates expression of transforming growth factor-beta in renal cells. Possible mechanism of cyclosporines antiproliferative effects.

CsA induces a reversible inhibition of proliferation in cultured murine proximal tubular cells (MCT cells) and syngeneic tubulointerstitial fibroblasts (TFB). To test whether this effect may be caused by endogenous synthesis and release of transforming growth factor-beta 1 (TGF-beta 1), a well-known inhibitor of mitosis, MCT cells and TFB grown in serum-free media were treated with different concentrations of CsA. CsA, in a dose-dependent manner in a range of 500-2000 ng/ml, stimulated expression of TGF-beta 1 protein and steady-state mRNA levels in both cell lines (MCT cells: controls, 9.3 +/- 1.0; 1500 ng/ml CsA, 19.1 +/- 6.1 pg TGF-beta 1/10(3) cells [P < 0.05 vs. controls]; TFB: controls, 5.4 +/- 0.9; 1500 ng/ml CsA, 7.7 +/- 0.3 pg TGF-beta 1/10(3) cells; n = 6). Short-term daily intraperitoneal injections of CsA (40 mg/kg body weight/day) into SJL mice for 1 and 4 weeks also induced an increase in whole kidney levels of TGF-beta 1 mRNA. Incubation of MCT cells and TFB with CsA in the presence of 30 micrograms/ml of a neutralizing anti-TGF-beta 1-3 mAb partly reversed the cell cycle arrest induced by CsA. These data suggest that CsA-mediated intrarenal synthesis and release of TGF-beta 1 may play a role in the CsA-induced growth arrest and might therefore be relevant in the development of chronic CsA nephrotoxicity, which is characterized by striped fibrosis and tubular atrophy.

Animals↗

PubMed1995

Specificity of the PTB domain of Shc for beta turn-forming pentapeptide motifs amino-terminal to phosphotyrosine.

Shc phosphorylation in cells following growth factor, insulin, cytokine, and lymphocyte receptor activation leads to its association with Grb2 and activation of Ras. In addition to being a cytoplasmic substrate of tyrosine kinases, Shc contains an SH2 domain and a non-SH2 phosphotyrosine binding (PTB) domain. Here we show that the Shc PTB domain, but not the SH2 domain, binds with high affinity (ID50 approximately equal to 1 microM) to phosphopeptides corresponding to the sequence surrounding Tyr250 of the polyoma virus middle T (mT) antigen (LLSNPTpYSVMRSK). Truncation studies show that five residues amino-terminal to tyrosine are required for high affinity binding, whereas all residues carboxyl-terminal to tyrosine can be deleted without loss of affinity. Substitution studies show that tyrosine phosphorylation is required and residues at -5, -3, -2, and -1 positions relative to pTyr are important for this interaction. 1H NMR studies demonstrate that the phosphorylated mT antigen-derived sequence forms a stable beta turn in solution, and correlations between structure and function indicate that the beta turn is important for PTB domain recognition. These results show that PTB domains are functionally distinct from SH2 domains. Whereas SH2 domain binding specificity derives from peptide sequences carboxyl-terminal to phosphotyrosine, the Shc PTB domain gains specificity by interacting with beta turn-forming sequences amino-terminal to phosphotyrosine.

Amino Acid Sequence↗

PubMed1995

Conformationally constrained phosphotyrosyl mimetics designed as monomeric Src homology 2 domain inhibitors.

Inhibitors of specific src homology 2 (SH2) domain binding interactions could potentially afford new therapeutic approaches toward a variety of diseases, including several cancers. To date SH2 domain inhibitors have been confined to small phosphotyrosyl (pTyr)-containing peptides that appear to bind along the surface of SH2 domains with specific recognition features protruding into the protein. Among these protrusions is the pTyr residue itself, which is inserted into a well-formed binding pocket. In the present study monomeric pTyr mimetics were prepared having key aspects of their structure constrained to conformations of the bound pTyr residue observed in the previously reported X-ray structure of a pTyr-peptide bound to the Lck SH2 domain. The resulting constrained pTyr mimetics were examined for inhibitory potency in six SH2 domain constructs: Lck, Src, Grb2, and the C-terminal SH2 domains of PLC gamma (PLC gamma-C) and the p85 subunit of PI-3 kinase (p85-C), as well as the N-terminal SH2 domain of SH PTP2. Although inhibition constants were in the millimolar range, it was observed that capping pTyr as its N alpha-acetyl carboxamide [(L)-1] provided a roughly 2-3-fold increase in potency relative to free pTyr. Diastereomeric indanylglycine-based analogues (+/-)-3a,b were essentially inactive. Of note was methanobenzazocine (+/-)-2. While being racemic and a partial pTyr structure, this analogue retained full binding potency of the enantiomerically pure N alpha-acetyl pTyr amide (L)-1. Modification and elaboration of 2 could potentially result in small molecule inhibitors having greater potency.

Amino Acid Sequence↗

PubMed1995

[Treatment of thrombotic thrombocytopenic purpura (Moschcowitz's disease) with vincristine].

A 64-year old female had been diagnosed as having thrombotic thrombocytopenic purpura (TTP; Moschcowitz syndrome) in 1984. The initial episode and one recurrence 5 years later were successfully treated with fresh plasma transfusions without plasmapheresis. Two days before the present admission, she noticed pain in the knee and haematomas in both legs. Marked thrombocytopenia (9000/microliters), haemolytic anaemia (lactate dehydrogenase 1800 U/l, haemoglobin 7.8 g/dl, haptoglobin 5 mg/dl) and skin haemorrhages suggested a second recurrence of TTP. The blood film showed a massive increase in fragmented cells (more than 30 per field), microspherocytes and normoblasts. Thrombocyte values initially rose on daily treatment with plasmapheresis using membrane separation and fresh plasma exchange. However, after two attempts at stopping therapy, plasmapheresis and fresh plasma replacement failed to normalise thrombocyte values. The patient had a total of 44 plasmaphereses. Intravenous administration of three doses of 1.5 mg vincristine at intervals of 7 and 5 days combined with further plasmapheresis treatment soon led to normalisation of the thrombocyte count (320,000/microliters), a fall in lactate dehydrogenase (120 U/l) and a disappearance of fragment cells in the blood smear. The patient is still in complete remission 6 months after stopping treatment. Treatment with vincristine should be considered for TTP refractory to treatment.

Bone Marrow Examination↗

PubMed1995

Angiotensin as a renal growth promoting factor.

The kidney has been traditionally considered to be one the pivotal organs involved in the systemic actions of the renin-angiotensin system (RAS) with renin produced in the juxtaglomerular apparatus and angiotensin II (ANG II) as a key player in the regulation of glomerular hemodynamics. However, many studies in the last decade, facilitated by a throughout molecular characterization of all elements of the RAS, have provided convincing evidence that the kidney exhibits a local RAS which may independently function from the systemic actions of the endocrine RAS. Moreover, even local distinct cell populations along the nephron possess all components of a functioning RAS. For example, proximal tubular cells express mRNA and protein for angiotensinogen, renin, and angiotensin converting enzyme (ACE). They bear different types of ANG II receptors with the appropriate signal transduction systems, and these cells also exhibit surface proteases like angiotensinase A which are required for the inactivation of ANG II. Moreover, recent studies in the isolated perfused kidney have clearly shown that proximal tubular cells produce considerable amounts of ANG II and these concentrations exceed approximately hundred times the systemic concentration of the peptide. Besides the well-known regulation of glomerular hemodynamics by contraction of the efferent glomerular arteriole and mesangium cells, ANG II influences transport and acidification processes in proximal and distal tubules. In addition, the octapeptide stimulates metabolic pathways like tubular gluconeogenesis and ammoniagenesis. Accumulating data over the last years derived from in vivo and in vitro studies have demonstrated that ANG II is also a growth factor for renal cells. For example, cell culture experiments have shown that the octapeptide stimulates proliferation or hypertrophy of mesangial cells. In contrast, proliferation of cultured proximal tubular cells is inhibited by ANG II and cellular hypertrophy of these cells is induced. Many studies have provided evidence that early mesangial proliferation/hypertrophy and tubular hypertrophy is a predecessor of the subsequent development of glomerulosclerosis and interstitial fibrosis, situations with irreversible morphological changes of the kidney's architecture leading finally to end-stage renal disease. Therefore, the identification of ANG II as a renal growth factor and a better understanding of its local intrarenal synthesis and growth stimulating effects on different cell types along the nephron may help to develop rational therapeutic interventions to prevent the progression of renal disease.

Angiotensin II↗

PubMed1995

Cellular biology of tubulointerstitial growth.

The study of tubular growth has certainly become more complex since Pierre-Rayers's time and is progressing toward a molecular dissection of regulatory events. Understanding the mechanisms of tubular growth is important, because these cells represent the bulk of the nephron, and there is convincing evidence of a link between tubular hypertrophy and the progression of renal disease with irreversible tubulointerstitial fibrosis as an end point. Two tubular growth responses can be distinguished: hypertrophy and hyperplasia. These fundamentally different patterns of growth indicate that diverse molecular mechanisms may be involved in inducing distinct growth responses. It is likely that cytokines and polypeptide growth factors play a role in tubular hypertrophy and hyperplasia. Probably, a combination of growth factors including inhibitory polypeptides like TGF beta, rather than a single factor, is necessary for differentiated tubular growth responses. Such factors bind to their receptors, and signals are transduced to the nucleus by various second messengers involving protein kinases, cyclic nucleotides, Ca++, and inositolphosphates. The phosphorylation of nuclear trans-acting factors resulting in an expression of immediate early genes may be the common pathway of many of these mediators. Finally, whether the cell is to proliferate or to remain in the G1-phase of the cell cycle is determined by the very complex cascade phosphorylation of kinases and their associations with different cyclins. How the induction of immediate early genes is linked to events of the cell cycle is currently incompletely understood. Negative regulation of growth through protein growth suppressors like the retinoblastoma gene product or the expression of special genes only during cell rest may be mandatory for the fine tuning of tubular growth.

Base Sequence↗

PubMed1995

Identification of cell membrane proteins linked to susceptibility to bovine viral diarrhoea virus infection.

Three monoclonal antibodies directed against cell surface molecules of bovine cells inhibited subsequent infections with bovine viral diarrhoea virus (BVDV). They specifically blocked the infectivity of three non-cytopathogenic and three cytopathogenic BVDV strains. These results showed that an important mechanism for virus uptake was inhibited. The ligand of the monoclonal antibody BVD/CA 17, which blocked infectivity most efficiently, was found on leukocytes from a wide range of domestic and wild even-toed ungulates using flow cytometric analysis. In contrast, the monoclonal antibodies BVD/CA 26 and BVD/CA 27 appeared to be specific for bovine cells. Immunoprecipitation of labelled bovine cell surface proteins showed that the three monoclonal antibodies bound to proteins with identical relative molecular masses (M(r)). Proteins of an apparent M(r) of 93 K and 60 K were precipitated from lysates of fetal bovine kidney cells irrespectively of the MAbs used.

Animals↗

PubMed1995

Viability of embryos following second polar body removal in a mouse model.

PURPOSE: Our purpose was to evaluate the effect of the second polar body removal on the viability and development potential of the resulting embryos. METHOD: The second polar body was removed in 343 mouse oocytes and the development potential of the resulting embryos was compared in vitro to that in 223 intact mouse embryos and 222 controls which were placed under the same conditions as those micromanipulated. RESULTS: The proportion of morphologically normal blastocysts formed by polar body biopsied oocytes (70.8%) was not significantly different from that obtained from the control (81.1%) and intact (85%) oocytes. Cell counts of blastocysts obtained from the manipulated and non-manipulated oocytes were also not statistically different. CONCLUSION: The second polar body biopsy does not have a significant adverse effect on preimplantation development and may be applied for genetic evaluation of oocytes.

Animals↗

PubMed1995

A dual approach to structural texture analysis in microscopic cell images.

The computer-based quantitative analysis of microscopic cell images provides important diagnostic information in clinical and experimental pathology. The arrangement of various cell structures can be described as texture. We developed a new approach to structural texture analysis. It assumes that texture consists of homogeneous regions (texture primitives). Texture can be regarded in a dual way--as a composition of regions or as a pattern composed of the regions' boundaries (lines). We implemented methods for the segmentation of regions and lines in grayscale images. The detection of regions is followed by a region-growing process to avoid an oversegmentation. The segmented regions and lines are stored in a uniform data structure which reflects their arrangement in the image. The presented methods were applied to study the chromatin distribution in cell nuclei and the development and differentiation of intermediate filaments in fetal liver cells.

Algorithms↗

PubMed1995

Evidence for bidirectional changes in nitric oxide synthase activity in the rat striatum after excitotoxically (quinolinic acid) induced degeneration.

Nitric oxide, a gaseous inter- and intracellular messenger, is thought to mediate neurotoxicity via excitatory amino acid receptors which may contribute to the pathogenesis of a variety of neuronal diseases. Excitotoxin lesions induced by quinolinic acid were made unilaterally in the rat striatum to study biochemically, light- and electron microscopically the possible involvement of the nitric oxide synthesizing enzyme nitric oxide synthase in degeneration processes. 5 days after quinolinic acid injection nitric oxide synthase activity in the striatum was elevated to 196.5% (P < 0.005% as compared to controls). There was no requirement of Ca2+ for the enzyme activity measured indicating that the elevation is due to the inducible isoform of nitric oxide synthase. Parallel to the depletion of neurons by quinolinic acid a massive gliosis was seen. Whereas quiescent astroglial cells in the normal striatum did not show any light microscopically detectable nicotinamide adenine dinucleotide phosphate diaphorase reaction, reactive astroglia revealed a substantial labeling distributed over the cell body and their stellar processes. Within the lesion and, particularly, close to the needle tract the number of microglia/macrophages labeled by isolectin B4 increased dramatically. Reactive microglial cells macrophages, situated along the needle tract and characterized by a pseudopodic or a globular shape, contained highest staining activity. At the ultrastructural level only disintegrated, if any, neuronal perikarya were seen five days after quinolinic acid injection while numerous reactive glial cells were observed. Reactive astroglia showed nicotinamide adenine dinucleotide phosphate diaphorase activity by displaying a substantial labeling of the nuclear envelope and endoplasmic membranes. Occasionally stained mitochondria were encountered. Globular-shaped (ameboidal) microglia near the needle tract were rich in phagocytotic debris and, apart from formazan-positive endomembranes, their plasmalemma was often nicotinamide adenine dinucleotide phosphate diaphorase stained. Additionally, in those cells regions of highly electron-dense puncta were seen which differ sharply from other cytoplasmic areas. Such sand-like accumulations of nicotinamide adenine dinucleotide phosphate diaphorase positive grains have never been observed in other cell types, indicating a special type of nitric oxide synthase representation, possibly that of the inducible isoform.

Amino Acid Oxidoreductases↗

PubMed1995

Neuroendocrine tumours in various organ systems in a ten-year period.

Neuroendocrine cells are present in various organ systems. These widely distributed cells as well as their histogenetically related tumours can produce various peptides and peptide hormones. From 1984 to 1993, 349 neuroendocrine tumours were found among 511,382 histological diagnoses at the Institute of Pathology of the Medical School of the Karl Franzens University in Graz. In 30% carcinoid of the appendix was diagnosed, in 16% carcinoid of the colorectum, in 9% carcinoid of the small intestine and in 2% duodenal carcinoid. Carcinoid of the stomach was detected in 14%. Seven of these cases showed microcarcinoidosis and five of them were combined with an adenocarcinoma. Carcinoid of the oesophagus was present in 1%, neuroendocrine pancreatic tumours in 6%. Neuroendocrine tumours of the bronchial system were found in 12%, medullary thyroid cancer in 5%. In 1% a Merkel-cell tumour was diagnosed. Other more rare localizations of neuroendocrine tumours were the uterus, ovary, breast, testes, epididymis, anal region and the upper respiratory tract.

Adult↗

PubMed1995

Intraoperative radiation therapy in advanced thyroid cancer.

An intraoperative radiation therapy (IORT)-protocol was designed for poorly differentiated non-anaplastic thyroid carcinoma. Out of 155 cases of differentiated thyroid tumours, 12 showed marked vascular/capsular invasion. Five entered the study (three primarily local invasive tumours, two local recurring). IORT was administered after tumour surgery (4-10 GY) and combined with post-operative percutaneous irradiation. The tumour control rate in the thyroid bed was achieved in all five patients, 1/5 developed mediastinal nodes and 1/5 with primary mediastinal tumour extension showed tumour progression. No specific complications occurred.

Adenocarcinoma, Follicular↗