Search PubMed⌕ Search

Biomedical subjects

W Richter

Publications and source records attributed to W Richter.

At least 127 records · Page 7Linked to original sources
PubMed1993

Prevalence of autoantibodies to the 65- and 67-kD isoforms of glutamate decarboxylase in insulin-dependent diabetes mellitus.

We investigated the presence of autoantibodies to baculovirus-expressed human recombinant 65- and 67-kD isoforms of glutamate decarboxylase (GAD65 and GAD67) in insulin-dependent diabetes mellitus (IDDM). In the immunoprecipitation test using [35S]methionine-labeled GADs antibodies to GAD65 were detected in 13/15 (87%) islet cell antibody (ICA)-positive and in 1/35 (2.9%) ICA-negative first-degree relatives of patients with IDDM, in 6/11 (54.5%) ICA-positive nondiabetic schoolchildren, and in 35/50 (70%) patients with newly diagnosed IDDM. GAD67 antibodies were positive only in five (33%) of the ICA-positive relatives (P < 0.05) and in nine (18%) IDDM patients at onset (P < 0.00001). After onset of IDDM antibodies to GAD65 and GAD67 declined but were still positive in 25 and 9.4% of subjects with long-standing IDDM (> 10 yr). In all study groups antibodies to GAD67 were only detected in GAD65 antibody-positive sera. An immunotrapping enzyme activity assay for GAD65 antibodies was positive in 64/75 (85.3%) of sera that were GAD antibody positive in the immunoprecipitation test (r = 0.870, P < 0.0001). In two (2.7%) sera GAD65 antibodies that block GAD enzyme activity were found. Our data suggest that antibodies to GAD65 but not to GAD67 represent sensitive markers for preclinical and overt IDDM. The immunotrapping assay here described represents a valuable technique for specific and sensitive screening for GAD antibodies.

Antibody Specificity↗
PubMed1993

Cytoplasmic islet cell antibodies recognize distinct islet antigens in IDDM but not in stiff man syndrome.

Cytoplasmic islet cell antibodies are well-established predictive markers of IDDM. Although target molecules of ICA have been suggested to be gangliosides, human monoclonal ICA of the immunoglobulin G class (MICA 1-6) produced from a patient with newly diagnosed IDDM recognized glutamate decarboxylase as a target antigen. Here we analyzed the possible heterogeneity of target antigens of ICA by subtracting the GAD-specific ICA staining from total ICA staining of sera. This was achieved 1) by preabsorption of ICA+ sera with recombinant GAD65 and/or GAD67 expressed in a baculovirus system and 2) by ICA analysis of sera on mouse pancreas, as GAD antibodies do not stain mouse islets in the immunofluorescence test. We show that 24 of 25 sera from newly diagnosed patients with IDDM recognize islet antigens besides GAD. In contrast, GAD was the only islet antigen recognized by ICA from 7 sera from patients with stiff man syndrome. Two of these sera, however, recognized antigens besides GAD in Purkinje cells. In patients with IDDM, non-GAD ICA were diverse. One group, found in 64% of the sera, stained human and mouse islets, whereas the other group of non-GAD ICA was human specific. Therefore, mouse islets distinguish two groups of non-GAD ICA and lack additional target epitopes of ICA besides GAD. Longitudinal analysis of 6 sera from nondiabetic ICA+ individuals revealed that mouse-reactive ICA may appear closer to clinical onset of IDDM in some individuals. Mouse-reactive ICAs, however, remained absent in 36% of the patients at diagnosis of IDDM.

Adolescent↗
PubMed1993

Differential expression of GAD65 and GAD67 in human, rat, and mouse pancreatic islets.

The smaller form of the autoantigen glutamic acid decarboxylase, GAD65 (formerly the 64,000 M(r) autoantigen), is a major target of humoral autoimmunity in type I diabetes. Human autoantisera have been used extensively to characterize the GAD65 antigen in both rat and human islets, but the protein has escaped detection in mouse islets. We have now analyzed the expression of GAD65 and GAD67, the larger glutamic acid decarboxylase protein, in human, rat, and mouse islets of Langerhans and brain, using human monoclonal islet cell autoantibodies, human autoantisera, and experimentally raised antibodies to glutamic acid decarboxylase. Human monoclonal autoantibodies and experimentally raised antibodies reacted with mouse GAD65 produced in a baculovirus expression system by Western blotting and immunoprecipitation and with GAD65 in mouse brain by immunohistochemistry but failed to detect GAD65 in mouse islets by the latter two methods. However, analysis of mouse islets by Western blotting technique, using the most sensitive experimentally raised antibody, showed that mouse islets express both GAD65 and GAD67 but at levels that are severalfold lower than those in mouse brain or in human and rat islets. Furthermore, both human and rat islets predominantly express GAD65, whereas GAD67 is the major glutamic acid decarboxylase protein in mouse islets. Human islets are significantly distinct from mouse and rat islets and from brain because they only express GAD65, which is consistent with the predominant role of this form as a target of autoantibodies associated with beta-cell destruction in humans. Human as well as rat islet GAD65 are found in both membrane-bound and soluble forms. The low level of glutamic acid decarboxylase expression in mouse islets compared with human and rat islets is likely to have implications for both the development of tolerance to glutamic acid decarboxylase as well as the homing of glutamic acid decarboxylase-specific lymphocytes to the mouse beta-cell. In this context, the results suggest 1) that the mouse is ideal for studies of the consequences of an expression of high levels of glutamic acid decarboxylase in the beta-cell from a transgene and 2) that the rat may be better suited than the mouse for development of nontransgenic animal models of glutamic acid decarboxylase autoimmunity by immunization.

Amino Acid Sequence↗
PubMed1993

[Quantitative 201Tl-scintigraphy of the lower limb in arterial occlusive disease].

201Tl scintigraphy is useful in evaluating the hemodynamic consequences of arterial stenoses in arterial occlusive disease. The aim of the present study was to determine normal values for absolute Tl uptake in the lower leg, for the quotient between left and right lower leg uptake as well as for the redistribution pattern after bicycle exercise. We examined as reference 49 patients without clinical evidence of peripheral or coronary artery disease: absolute Tl uptake in the lower leg in anterior scintigraphy (acquisition time: 120 sec) was 5.02 +/- 1.70 counts/pixel (left) and 5.21 +/- 1.53 counts/pixel (right), the quotient between right and left lower leg was 0.85 +/- 0.09 and the redistribution pattern (quotient of the mean activity exercise/rest) 0.82 +/- 0.17 (left) and 0.83 +/- 0.15 (right). The arithmetic mean minus 2 standard deviations was regarded as the lower limit of normal. In 8 patients with mechanical compression of the left femoral artery before injection at least two scintigraphic parameters were abnormal, in 7 patients with angiographically proven peripheral artery disease at least one scintigraphic parameter was below normal. Quantification of Tl redistribution offers diagnostic advantages in bilateral peripheral artery disease.

Adult↗
PubMed1993

[Prophylactic inhalation of amphotericin B in invasive aspergillosis: a distribution study].

Invasive pulmonary aspergillosis (IPA) during periods of immunosuppression or prolonged neutropenia is a serious condition with high mortality. Prophylaxis is unsatisfactory because of the low effectiveness of systemic administration of amphotericin B (AMB) and because of its side effects. Prophylactic inhalation of AMB by means of a nebulizing system may be able to reduce the incidence of IPA. Therefore, we studied the distribution of nebulized 99mTc-labeled AMB and estimated its particle size. AMB is homogeneously distributed in the lung and partly deposited in the terminal respiratory unit; it remains there with a half-life of at least 14 h. Therefore, prophylaxis of IPA with AMB nebulized as described can be recommended.

Administration, Inhalation↗
PubMed1993

[Microstructure of fossil mammalian bones from the Rixdorfer Horizon of Weichsel-Kaltzeit at Niederlehme near Königs Wusterhausen (Brandengurg)].

The structure is reported of bones of glacial-period mammals, which were found in 1973 to 1989 in gravel-sandy soil of the fossiliferous layer "Rixdorfer Horizont" at Niederlehme near Königs Wusterhausen. The findings, probably, date from one of the interstages of the glacial period "Weichsel-Kaltzeit" before the stage "Brandenburger Stadium". Their embedding took place more than 20,000 years ago. Changes of the deposit of bones and teeth from older sediments are not to exclude in the finding place Niederlehme. In the collection of findings with 102 skeletal parts are to define following species: Mammuthus primigenius, Coelodonta antiquitatis, Equus sp., Bison priscus, Megalocerus giganteus, Cervus elaphus, Rangifer tarandus and Canis lupus. A trajectorial direction of the trabecula in the substantia spongiosa is evident. There are also specific channels of blood vessels with different diameters. This channels have completely closed bone-wall (with a central venous sinus of diameter 5 to 10 mm) or in little vessels (diameter 1 to 3 mm), we have found many apertures to the rooms of the substantia spongiosa. The microscopical investigation of bones of Mammuthus primigenius has shown Havers' channels and perforating channels, Havers' systems and lacunae osseae.

Animals↗
PubMed1992

Human monoclonal islet cell antibodies from a patient with insulin-dependent diabetes mellitus reveal glutamate decarboxylase as the target antigen.

The autoimmune phenomena associated with destruction of the beta cell in pancreatic islets and development of type 1 (insulin-dependent) diabetes mellitus (IDDM) include circulating islet cell antibodies. We have immortalized peripheral blood lymphocytes from prediabetic individuals and patients with newly diagnosed IDDM by Epstein-Barr virus transformation. IgG-positive cells were selected by anti-human IgG-coupled magnetic beads and expanded in cell culture. Supernatants were screened for cytoplasmic islet cell antibodies using the conventional indirect immunofluorescence test on cryostat sections of human pancreas. Six islet cell-specific B-cell lines, originating from a patient with newly diagnosed IDDM, could be stabilized on a monoclonal level. All six monoclonal islet cell antibodies (MICA 1-6) were of the IgG class. None of the MICA reacted with human thyroid, adrenal gland, anterior pituitary, liver, lung, stomach, and intestine tissues but all six reacted with pancreatic islets of different mammalian species and, in addition, with neurons of rat cerebellar cortex. MICA 1-6 were shown to recognize four distinct antigenic epitopes in islets. Islet cell antibody-positive diabetic sera but not normal human sera blocked the binding of the monoclonal antibodies to their target epitopes. Immunoprecipitation of 35S-labeled human islet cell extracts revealed that a protein of identical size to the enzyme glutamate decarboxylase (EC 4.1.1.15) was a target of all MICA. Furthermore, antigen immunotrapped by the MICA from brain homogenates showed glutamate decarboxylase enzyme activity. MICA 1-6 therefore reveal glutamate decarboxylase as the predominant target antigen of cytoplasmic islet cell autoantibodies in a patient with newly diagnosed IDDM.

Adolescent↗
PubMed1992

[Radioimmunoscintigraphy of colorectal tumors with 99m-Tc marked CEA antibodies. Indications and clinical value].

In Germany, radioimmunoscintigraphy (RIS) (scintigraphic, specific imaging of benign and malignant diseases by radioactively labelled monoclonal antibodies) has been employed since 1985 in clinical trials involving patients with colorectal cancer. After proving successful for identifying primary tumors, RIS is now increasingly being used for the early diagnosis of recurrent and metastatic lesions. In this prospective study involving 75 patients with colorectal tumors confirmed by endoscopy and biopsy, it was shown that RIS using the SPECT technique with 99m-Tc-labelled monoclonal CEA antibodies has a sensitivity of 78% in the detection of local recurrent disease in cases in which diagnostic work-up has been inconclusive.

Adult↗
PubMed1992

Ochratoxin A production in Bavarian cereal grains stored at 15 and 19% moisture content.

Wheat, barley, and maize, each in 15-kg parcels at 15 and 19% initial moisture content (IMC), were kept in a Bavarian farm granary from June through November 1990. During this period, the grain at each IMC was analyzed for mycotoxins and monitored for grain temperature, carbon dioxide, seed germination, and microfloral incidence and abundance. Barley and maize stored for 20 weeks at 19% IMC contained ochratoxin A in amounts of 70 and 90 microg/kg, respectively. This mycotoxin was not detected in wheat stored at 19% IMC, nor in the grains stored at 15% IMC. Aflatoxin B1, sterigmatocystin, citrinin, and zearalenone were also assayed but not detected in grains stored at either IMC. Principal component analysis of the data indicated that ochratoxin A was produced in a damp niche in maize, when abundant metabolic activity and CO2 production by Penicillium glandicola and Aspergillus spp. were common.

Edible Grain↗
PubMed1992

Antibodies to the M(r) 64,000 (64K) protein in islet cell antibody positive non-diabetic individuals indicate high risk for impaired beta-cell function.

A prospective study of a normal childhood population identified 44 islet cell antibody positive individuals. These subjects were typed for HLA DR and DQ alleles and investigated for the presence of antibodies to the M(r) 64,000 (64K) islet cell antigen, complement-fixing islet cell antibodies and radiobinding insulin autoantibodies to determine their potency in detecting subjects with impaired Beta-cell function. At initial testing 64K antibodies were found in six of 44 islet cell antibody positive subjects (13.6%). The same sera were also positive for complement-fixing islet cell antibodies and five of them had insulin autoantibodies. During the follow-up at 18 months, islet cell antibodies remained detectable in 50% of the subjects studied. In all six cases who were originally positive, 64K antibodies were persistently detectable, whereas complement-fixing islet cell antibodies became negative in two of six and insulin autoantibodies in one of five individuals. HLA DR4 (p less than 0.005) and absence of asparic acid (Asp) at position 57 of the HLA DQ beta chain (p less than 0.05) were significantly increased in subjects with 64K antibodies compared with control subjects. Of 40 individuals tested in the intravenous glucose tolerance test, three had a first phase insulin response below the first percentile of normal control subjects. Two children developed Type 1 (insulin-dependent) diabetes mellitus after 18 and 26 months, respectively. Each of these subjects was non-Asp homozygous and had persistent islet cell and 64K antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Dextran sulfate-dependent fusion of liposomes containing cationic stearylamine.

The incorporation of the positively charged stearylamine into phosphatidylcholine liposomes was studied by measuring electrophoretic mobilities. Up to a molar ratio SA/PC = 0.5 an increase of the positive zeta potential can be observed. Addition of the negatively charged macromolecule dextran sulfate leads to a change of the sign of the surface potential of the PC/SA liposomes indicating binding of the macromolecule to the surface. This process is accompanied by an increase in turbidity, which is dependent on the molecular weight of the dextran sulfate and the SA concentration (measured by turbidimetry). Using the NBD/Rh and Pyr-PC fluorescence assays the fusion of SA containing liposomes was investigated. A strong influence of the SA content and molecular weight of dextran sulfate on the fusion extent was observed. The fusion extent is proportional to the SA content in the PC membrane and the molecular weight of dextran sulfate. PC/SA/PE liposomes exhibit a higher fusion extent after addition of dextran sulfate compared to PC/SA liposomes indicating that PE additionally destabilizes the bilayer. Freeze-fracture electron microscopy reveals that the reaction products are large complexes composed of multilamellar stacks of tightly packed, straight membranes and aggregated vesicles. The tight packing of the membranes in the stacks (and the narrow contact of the aggregated vesicles) indicates a strong adherence of opposite membrane surfaces induced by dextran sulfate.

Amines↗
PubMed1992

Redox cycling of potential antitumor aziridinyl quinones.

The formation of reactive oxygen intermediates (ROI) during redox cycling of newly synthesized potential antitumor 2,5-bis (1-aziridinyl)-1,4-benzoquinone (BABQ) derivatives has been studied by assaying the production of ROI (superoxide, hydroxyl radical, and hydrogen peroxide) by xanthine oxidase in the presence of BABQ derivatives. At low concentrations (< 10 microM) some BABQ derivatives turned out to inhibit the production of superoxide and hydroxyl radicals by xanthine oxidase, while the effect on the xanthine-oxidase-induced production of hydrogen peroxide was much less pronounced. Induction of DNA strand breaks by reactive oxygen species generated by xanthine oxidase was also inhibited by BABQ derivatives. The DNA damage was comparable to the amount of hydroxyl radicals produced. The inhibiting effect on hydroxyl radical production can be explained as a consequence of the lowered level of superoxide, which disrupts the Haber-Weiss reaction sequence. The inhibitory effect of BABQ derivatives on superoxide formation correlated with their one-electron reduction potentials: BABQ derivatives with a high reduction potential scavenge superoxide anion radicals produced by xanthine oxidase, leading to reduced BABQ species and production of hydrogen peroxide from reoxidation of reduced BABQ. This study, using a unique series of BABQ derivatives with an extended range of reduction potentials, demonstrates that the formation of superoxide and hydroxyl radicals by bioreductively activated antitumor quinones can in principle be uncoupled from alkylating activity.

Antineoplastic Agents↗
PubMed1992

[The value of radioimmunoscintigraphy compared to computed tomography in the diagnosis and relapse diagnosis of colorectal tumors].

Radioimmunoscintigraphy (= RIS, scintigraphic "specific" imaging of benign and malignant diseases by means of radioactively marked monoclonal antibodies) has been performed in Germany in clinical studies since 1985 in patients suffering from colorectal cancer. After having been successfully proven in primary studies, RIS is now being used in the early diagnosis of recurrences and metastases. In the prospective study presented here the clinical usefulness of RIS was assessed in comparison against well-tried diagnostic methods including computed tomography in patients suffering from colorectal cancer. It was shown that RIS in SPECT technique (= single photon emission computed tomography) with 99mTc-labelled monoclonal CEA antibodies can visualise local recurrences if diagnostic findings are doubtful, with a sensitivity of 78% versus 50% for CT findings.

Adult↗
PubMed1992

Regression of left ventricular hypertrophy.

Since our first studies on hypertrophy regression, this parameter has achieved an increasing interest in the treatment of hypertension. During the past 8 years we studied different groups of antihypertensive drugs with the use of magnetic resonance imaging (MRI). This article discusses the antihypertensive drug carvedilol. We examined 17 patients with diastolic blood pressure of at least 95 mm Hg and left ventricular wall thickness of at least 15 mm. Measurements were carried out before and after treatment with 25 mg/day carvedilol for 6 months. We demonstrated a significant regression of septal thickness from 17.7 to 16.3 mm. At each wall, three measurements at different points were performed by MRI and the means were calculated. Left ventricular ejection fraction and wall motion did not show any significant changes in radionuclide ventriculography after treatment. The diastolic blood pressure was reduced from 98.0 to 88.7 mm Hg. All differences are significant (p less than 0.05). There was no significant correlation between the extent of regression of septal hypertrophy and the degree of pretherapeutic hypertrophy, the age of patients, or the dimension of blood pressure reduction.

Animals↗
PubMed1992

Chemical and physiological properties of polysucrose, a new marker of intestinal permeability to macromolecules.

To measure intestinal absorption of macromolecules we have developed a new technique employing synthetic polysucrose polymers as probe molecules. Polysucrose (PS) is water-soluble, nontoxic, resistant to intestinal enzymes, spherical and can be produced with a molecular weight distribution that relates to the size of many normal food proteins. Normally, a very small fraction of large molecules passes the exclusion barrier of the healthy intestine. Thus, quantification of resorbed macromolecules requires assays of high sensitivity. For detection of PS in various biological fluids, micro-ELISAs have been established. PS with a mean molecular weight of 14,700 daltons (PS 15,000) is rapidly excreted into the urine. Twenty-one healthy volunteers who orally ingested 1 g of this preparation showed a 12-hour urine excretion of 0.018% (interquartile range 0.014-0.022).

Adult↗
PubMed1992

Is it still adequate to study the nervous system using methods of catalytic enzyme histochemistry?

The frequent use of methods different from enzyme histochemistry evokes the question, whether it is still useful to apply methods of catalytic enzyme histochemistry to study the nervous system. In this brief overview it is shown, that catalytic enzyme histochemistry can still contribute to a better understanding of nervous system function. This was enabled by methodological progress, i.e., the modification of already existing procedures or the development of new techniques for the visualization and measurement of enzymes in tissue sections using their catalytic properties. The methods for acetylcholinesterase, monoamine oxidase as well as certain exoglycosidases and phosphatases will be given as examples. The application of these procedures as well as of methods for proteases, oxyradical-generating oxidases and enzymes involved in the metabolism of amino acid and other transmitters will illustrate, that qualitative (localization) and quantitative (measurement) catalytic enzyme histochemistry can still contribute to a better understanding of nervous system function.

Animals↗