Biomedical subjects

D Jung

Publications and source records attributed to D Jung.

At least 73 records · Page 4Linked to original sources

PubMed1997

Expression and function of the peptide transporters in escape variants of human renal cell carcinomas.

The transporter associated with antigen processing (TAP) complex is a heterodimeric transmembrane pump consisting of the TAP-1 and TAP-2 subunits; these subunits translocate peptides from the cytoplasm into the lumen of the endoplasmic reticulum, where they bind nascent major histocompatibility complex (MHC) class I molecules. Loss or reduced expression of the TAP genes results in the synthesis of unstable peptide free MHC class I molecules that are only weakly expressed on the cell surface. In a number of human tumor cell lines, downregulation of MHC class I expression has been found to be associated with reduced or absent TAP expression. To investigate whether alterations in MHC class I expression occur during transformation and subsequent progression and whether MHC class I suppression is caused by impaired TAP function, we analyzed the protein expression of MHC class I heavy and light chain and TAP-1 in three renal cell carcinoma (RCC) cell lines and short-term cultures from corresponding normal kidney tissue. In one case a cell line established from a metastatic lesion was also available. Compared with normal epithelial cells, suppression of TAP-1 and MHC class I molecules was detected in all three primary RCC cells and was even more pronounced in the metastatic cell line. In contrast to normal epithelial cells, MHC class I membrane expression of two RCC lines was enhanced by culture in the presence of MHC class I binding peptides or at low temperature (26 degrees C) instead of 37 degrees C. Unstable MHC class I surface expression is caused by dissociation of the MHC class I heavy and light chain molecules as a result of functional defects in the antigen processing machinery, e.g., impaired peptide transport. Attempts to counteract the reduced immunogenicity by transferring the TAP genes into these cells demonstrated that TAP-1-modified RCC cells expressed higher levels of MHC class I molecules. These data indicate that downregulation and instability of MHC class I surface expression in RCC cells is at least partially caused by deficient loading with endogenous peptides and can be restored by TAP gene transfer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1996

Characterization of delta-sarcoglycan, a novel component of the oligomeric sarcoglycan complex involved in limb-girdle muscular dystrophy.

The sarcoglycan complex is known to be involved in limb-girdle muscular dystrophy (LGMD) and is composed of at least three proteins: alpha-, beta-, and gamma-sarcoglycan. delta-Sarcoglycan has now been identified as a second 35-kDa sarcolemmal transmembrane glycoprotein that shares high homology with gamma-sarcoglycan and is expressed mainly in skeletal and cardiac muscle. Biochemical analysis has demonstrated that gamma- and delta-sarcoglycan are separate entities within the sarcoglycan complex and that all four sarcoglycans exist in the complex on a stoichiometrically equal basis. Immunohistochemical analysis of skeletal muscle biopsies from patients with LGMD2C, LGMD2D, and LGMD2E demonstrated a reduction of the entire sarcoglycan complex in these muscular dystrophies. Furthermore, we have mapped the human delta-sarcoglycan gene to chromosome 5q33-q34 in a region overlapping the recently linked autosomal recessive LGMD2F locus.

Amino Acid Sequence↗

PubMed1996

Defective propagation of signals generated by sympathetic nerve stimulation in the liver of connexin32-deficient mice.

The gap junctional protein connexin32 is expressed in hepatocytes, exocrine pancreatic cells, Schwann cells, and other cell types. We have inactivated the connexin32 gene by homologous recombination in the mouse genome and have generated homozygous connexin32-deficient mice that were viable and fertile but weighed on the average approximately 17% less than wild-type controls. Electrical stimulation of sympathetic nerves in connexin32-deficient liver triggered a 78% lower amount of glucose mobilization from glycogen stores, when compared with wild-type liver. Thus, connexin32-containing gap junctions are essential in mouse liver for maximal intercellular propagation of the noradrenaline signal from the periportal (upstream) area, where it is received from sympathetic nerve endings, to perivenous (downstream) hepatocytes. In connexin32-defective liver, the amount of connexin26 protein expressed was found to be lower than in wild-type liver, and the total area of gap junction plaques was approximately 1000-fold smaller than in wild-type liver. In contrast to patients with connexin32 defects suffering from X chromosome-linked Charcot-Marie-Tooth disease (CMTX) due to demyelination in Schwann cells of peripheral nerves, connexin32-deficient mice did not show neurological abnormalities when analyzed at 3 months of age. It is possible, however, that they may develop neurodegenerative symptoms at older age.

Animals↗

PubMed1996

Absence of gamma-sarcoglycan (35 DAG) in autosomal recessive muscular dystrophy linked to chromosome 13q12.

We have partially sequenced rabbit skeletal muscle gamma-sarcoglycan, an integral component of the dystrophin-glycoprotein complex. Specific antibodies were produced against a gamma-sarcoglycan peptide and used to examine the expression of gamma-sarcoglycan in skeletal muscle of patients with severe childhood autosomal muscular dystrophy linked to chromosome 13q12 (SCARMD). We show by immunofluorescence and Western blotting that in skeletal muscle from these patients gamma-sarcoglycan is completely absent and alpha- and beta-sarcoglycan are greatly reduced in abundance, whereas other components of the DGC are preserved. In addition, we show that in normal muscle alpha-, beta-, and gamma-sarcoglycan constitute a tightly associated sarcolemma complex which cannot be disrupted by SDS treatment.

Animals↗

PubMed1996

Clinical heterogeneity of adhalin deficiency.

We report adhalin deficiency in 8 patients with clinically diagnosed muscular dystrophy, dystrophic histopathological features, high plasma creatine kinase levels, normal expression of dystrophin, and marked variability of symptoms. Although the distribution of hyposthenia was similar in all 8 patients and predominantly involved muscles in the pelvic girdle, age at onset and rate of disease progression were highly variable: In 2 patients onset, at ages 24 and 25, was later than has been previously observed. We found no apparent relation between disease severity and the quantity of adhalin expressed. Two kinds of myopathy with adhalin deficiency have been reported: one caused by a mutation in the adhalin gene on chromosome 17 (primary adhalinopathy) and the other linked to chromosome 13. The product of the gene on chromosome 13 is probably associated with adhalin and its deficiency results in secondary adhalinopathy. The severity of clinical phenotypes in these adhalinopathies seems to relate more to the kind and site of the mutations than to the residual amount of the protein. We also detected a variable reduction in the laminin beta 1 subunit by immunohistochemistry in most patients, confirming that this is commonly associated with adhalin deficiency.

Adolescent↗

PubMed1996

Effect of food on the relative bioavailability of oral ganciclovir.

The steady-state pharmacokinetics of oral ganciclovir in the fasting versus fed state were studied in 20 patients infected with human immunodeficiency virus and with a seropositive test result for cytomegalovirus in a two-way crossover study. Patients received oral ganciclovir at a dose of 1000 mg every 8 hours for 8 days. On days 4 and 8, subjects were randomly assigned to receive the morning dose either after an overnight fast or after a standardized 602-calorie, high-fat (46.5%) breakfast. Serial blood samples were obtained over the 8-hour morning dose interval. The mean time to maximum concentration (tmax) was increased from 1.8 hours in the fasting state to 3.0 hours in the fed state. Mean maximum serum concentration (Cmax) and area under the concentration-time curve from time 0 to 8 hours (AUC0-8) of ganciclovir were significantly higher in the fed state than after an overnight fast. Because food could potentially increase the bioavailability of oral ganciclovir, patients should be instructed to take each dose of oral ganciclovir with food.

Administration, Oral↗

PubMed1996

Elimination of polychlorinated dibenzo-p-dioxins and dibenzofurans in occupationally exposed persons.

The elimination of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) was investigated in a group of n = 43 exposed workers with 2 blood measurements and n = 5 workers with 3 measurements. Under the assumption of a one-compartment, first-order kinetic model the median half-life for 2,3,7,8-TCDD was 7.2 yr, while for the other dioxins the estimates were between 3.7 yr for 1,2,3,4,6,7,8-HpCDD (hepta-chlorinated) and 15.7 yr for 1,2,3,7,8-PCDD (penta-chlorinated). For the furans median half-lives between 3.0 yr for 1,2,3,4,6,7,8-HpCDF and 19.6 yr for 2,3,4,7,8-PCDF were observed. There was no indication for a deviation from a first-order kinetic. Increasing age and percent body fat were associated with increasing half-life for most of the congeners. Smokers in general had a faster decay than non- and ex-smokers. In summary, the higher chlorinated PCDD/F like TCDD appear to be highly persistent in humans with half-lives ranging between 4 and 12 yr.

Adipose Tissue↗

PubMed1996

Forced expression of dystrophin deletion constructs reveals structure-function correlations.

Dystrophin plays an important role in skeletal muscle by linking the cytoskeleton and the extracellular matrix. The amino terminus of dystrophin binds to actin and possibly other components of the subsarcolemmal cytoskeleton, while the carboxy terminus associates with a group of integral and peripheral membrane proteins and glycoproteins that are collectively known as the dystrophin-associated protein (DAP) complex. We have generated transgenic/mdx mice expressing "full-length" dystrophin constructs, but with consecutive deletions within the COOH-terminal domains. These mice have enabled analysis of the interaction between dystrophin and members of the DAP complex and the effects that perturbing these associations have on the dystrophic process. Deletions within the cysteine-rich region disrupt the interaction between dystrophin and the DAP complex, leading to a severe dystrophic pathology. These deletions remove the beta-dystroglycan-binding site, which leads to a parallel loss of both beta-dystroglycan and the sarcoglycan complex from the sarcolemma. In contrast, deletion of the alternatively spliced domain and the extreme COOH terminus has no apparent effect on the function of dystrophin when expressed at normal levels. The proteins resulting from these latter two deletions supported formation of a completely normal DAP complex, and their expression was associated with normal muscle morphology in mdx mice. These data indicate that the cysteine-rich domain is critical for functional activity, presumably by mediating a direct interaction with beta-dystroglycan. However, the remainder of the COOH terminus is not required for assembly of the DAP complex.

Animals↗

PubMed1996

Non-neural agrin codistributes with acetylcholine receptors during early differentiation of Torpedo electrocytes.

Agrin, an extracellular matrix protein synthesized by nerves and muscles is known to promote the clustering of acetylcholine receptors and other synaptic proteins in cultured myotubes. This observation suggests that agrin may provide at least part of the signal for synaptic specialization in vivo. The extracellular matrix components agrin, laminin and merosin bind to alpha-dystroglycan, a heavily glycosylated peripheral protein part of the dystrophin-glycoprotein complex, previously characterized in the sarcolemma of skeletal and cardiac muscles and at the neuromuscular junction. In order to understand further the function of agrin and alpha DG in the genesis of the acetylcholine receptor-rich membrane domain, the settling of components of the dystrophin-glycoprotein complex and agrin was followed by immunofluorescence localization in developing Torpedo marmorata electrocytes. In 40-45 mm Torpedo embryos, a stage of development at which the electrocytes exhibit a definite structural polarity, dystrophin, alpha/beta-dystroglycan and agrin accumulated concomitantly with acetylcholine receptors at the ventral pole of the cells. Among these components, agrin appeared as the most intensely concentrated and sharply localized. The scarcity of the nerve-electrocyte synaptic contacts at this stage of development, monitored by antibodies against synaptic vesicles, further indicates that before innervation, the machinery for acetylcholine receptor clustering is provided by electrocyte-derived agrin rather than by neural agrin. These observations suggest a two-step process of acetylcholine receptor clustering involving: (i) an instructive role of electrocyte-derived agrin in the formation of a dystrophin-based membrane scaffold upon which acetylcholine receptor molecules would accumulate according to a diffusion trap model; and (ii) a maturation and/or stabilization step controlled by neural agrin. In the light of these data, the existence of more than one agrin receptor is postulated to account for the action of agrin variants at different stages of the differentiation of the postsynaptic membrane in Torpedo electrocytes.

Agrin↗

PubMed1996

[Principles of surgical treatment of obstructive sleep apnea by interventions on the facial bones].

The clinical picture of the obstructive sleep apnea syndrome is caused by a multifactorial etiology. Therefore a lot of different conservative as well as surgical therapeutic approaches are discussed. In approximately 40% of the patients an obstruction of the pharyngeal airway is combined with an abnormal sagittal morphology of the skull. In these cases a simultaneous maxillomandibular advancement by at least 10 mm seems to be a causal therapy, leading to an enlargement of the pharyngeal airways. The current therapeutic results are roughly stable up to a period of approximately 3 years. Requirement of this therapy is the exclusion and/or the prior therapy of an extreme obesity, which can favour the manifestation of an obstructive sleep apnea syndrome.

Airway Obstruction↗

PubMed1995

Identification and characterization of the dystrophin anchoring site on beta-dystroglycan.

Dystrophin, the product of the Duchenne muscular dystrophy gene, is tightly associated with the sarcolemmal membrane to a large glycoprotein complex. One function of the dystrophin-glycoprotein complex is to link the cytoskeleton to the extracellular matrix in skeletal muscle. However, the molecular interactions of dystrophin with the membrane components of the dystrophin-glycoprotein complex are still elusive. Here, we demonstrate and characterize a specific interaction between beta-dystroglycan and dystrophin. We show that skeletal muscle and brain dystrophin as well as brain dystrophin isoforms specifically bind to beta-dystroglycan. To localize and characterize the dystrophin and beta-dystroglycan interaction domains, we reconstituted the interaction in vitro using dystrophin fusion proteins and in vitro translated beta-dystroglycan. We demonstrated that the 15 C-terminal amino acids of beta-dystroglycan constituted a unique binding site for the second half of the hinge 4 and the cysteine-rich domain of dystrophin (amino acids 3054-3271). This dystrophin binding site is located in a proline-rich environment of beta-dystroglycan within amino acids 880-895. The identification of the interaction sites in dystrophin and beta-dystroglycan provides further insight into the structure and the molecular organization of the dystrophin-glycoprotein complex at the sarcolemma membrane and will be helpful for studying the pathogenesis of Duchenne muscular dystrophy.

Amino Acid Sequence↗

PubMed1995

SH3 domain-mediated interaction of dystroglycan and Grb2.

Dystroglycan is a novel laminin receptor that links the extracellular matrix and sarcolemma in skeletal muscle. The dystroglycan complex containing alpha- and beta-dystroglycan also serves as an agrin receptor in muscle, where it may regulate agrin-induced acetylcholine receptor clustering at the neuromuscular junction. beta-Dystroglycan has now been expressed in vitro and shown to directly interact with Grb2, an adapter protein involved in signal transduction and cytoskeletal organization. Protein binding assays with two Grb2 mutants, Grb2/P49L and Grb2/G203R, which correspond to the loss-of-function mutants in the Caenorhabditis elegans sem-5, demonstrated that the dystroglycan-Grb2 association is through beta-dystroglycan C-terminal proline-rich domains and Grb2 Src homology 3 domains. Affinity chromatography has also shown endogenous skeletal muscle Grb2 interacts with beta-dystroglycan. Immunoprecipitation experiments have demonstrated that Grb2 associates with alpha/beta-dystroglycan in vivo in both skeletal muscle and brain. The specific dystroglycan-Grb2 interaction may play an important role in extracellular matrix-mediated signal transduction and/or cytoskeleton organization in skeletal muscle that may be essential for muscle cell viability.

Adaptor Proteins, Signal Transducing↗

PubMed1995

Identification of alpha-syntrophin binding to syntrophin triplet, dystrophin, and utrophin.

Syntrophin represents three cytoplasmic components of the dystrophin-glycoprotein complex that links the cytoskeleton to the extracellular matrix in skeletal muscle. alpha-Syntrophin has now been translated in vitro and shown to associate directly with all three components of the syntrophin triplet and with dystrophin. The in vitro translated 71-kDa non-muscle dystrophin isoform, containing the cystein-rich/C-terminal domain, can also interact with the syntrophin triplet. The syntrophin binding motif in dystrophin was localized to exons 73 and 74 including amino acids 3447-3481 by comparing the interactions of alpha-syntrophin and seven overlapping human dystrophin fusion proteins. More than one syntrophin interaction site in this binding motif was suggested. alpha-Syntrophin also interacts directly with a C-terminal utrophin fusion protein. alpha-Syntrophin is localized to the muscle sarcolemma as well as to the neuromuscular junction in control mouse muscle. However, similar to utrophin, alpha-syntrophin is only present at the neuromuscular junction in mdx mouse muscle in which dystrophin is absent. Our data suggest that alpha-syntrophin binds all syntrophin isoforms, and syntrophin directly interacts with dystrophin through more than one binding site in dystrophin exons 73 and 74 including amino acids 3447-3481.

ATP-Binding Cassette Transporters↗

PubMed1995

DNA damage in nurses handling antineoplastic agents.

In 91 nurses from several divisions of four hospitals in Germany the genotoxic effect caused by the occupational exposure presumably due to mixing of antineoplastic agents was investigated. The amount of DNA single strand breaks and alkali labile sites in the peripheral mononuclear blood cells of the nurses was measured using the alkaline elution method. In ten nurses handling antineoplastic agents not using recommended safety precautions such as safety hoods, gloves or surgical masks a 50% higher level of DNA strand breaks and alkali-labile sites (p < 0.005; U-test) was detected compared to 54 controls. After applying recommended safety precautions a statistically significant decrease (p < 0.01) in the level of DNA strand breaks to the level of controls was observed. In other nurses handling antineoplastic agents by using adequate safety equipment no significantly different amount of DNA strand breaks compared to that of controls was detected. No significant correlation between the level of DNA strand breaks and the weekly contact frequency, the life-time exposure to antineoplastic agents, or the time elapsed since the last handling of the drugs was found in this study.

Adult↗

PubMed1995

Pharmacokinetic, safety, and antiviral profiles of oral ganciclovir in persons infected with human immunodeficiency virus: a phase I/II study. AIDS Clinical Trials Group, and Cytomegalovirus Cooperative Study Group.

A phase I/II study evaluated the pharmacokinetics, tolerability, and antiviral activity of oral ganciclovir in persons infected with human immunodeficiency virus (HIV). Oral bioavailability ranged from 2.6% to 7.3%. The mean maximum serum concentration achieved at 1000 mg every 8 h was 1.11 micrograms/mL, and mean trough level was 0.54 microgram/mL. The time to maximum serum drug concentration was 1.0-2.9 h, with a serum half-life of 3.0-7.3 h, suggesting prolonged oral absorption. Serious adverse events were uncommon. Decreased cytomegalovirus (CMV) shedding was observed from all sites. The median days (by dosage) to retinitis progression assessed by retinal examination after initiation of oral ganciclovir were 62 (1000 mg every 8 h), 148 (500 mg every 3 h), 75 (750 mg every 3 h), 148 (1000 mg every 3 h), and 139 (2000 mg every 8 h). Thus, oral ganciclovir has pharmacokinetic, toxicity, and antiviral profiles that may prove beneficial for both maintenance therapy of CMV retinitis and prevention of CMV disease in HIV-infected persons.

Administration, Oral↗

PubMed1994

Fluid dynamic study of the moving actuator type total artificial heart by image-processing technique.

Flow velocity inside the artificial ventricle of a moving actuator type total artificial heart is investigated by the image-processing technique. Optical flow is estimated from two sequential images of flow patterns to find flow-velocity distribution. The region with high velocity inside the artificial ventricle is found from the estimated flow-velocity distribution. Fluid velocity in a simple glass conduit is analysed and can be estimated by calculating optical flow.

Blood Flow Velocity↗

PubMed1994

Porphyrin studies in TCDD-exposed workers.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been shown to inhibit uroporphyrinogen decarboxylase activity resulting in chronic hepatic porphyria. From a cross-sectional study of 170 workers in chemical industry 68 showed elevated coproporphyrin levels, interpreted as secondary coproporphyrinuria. Three persons suffered from chronic hepatic porphyria in subclinical stages. None of the workers showed an overt porphyria cutanea tarda. A low-grade zinc protoporphyrinemia was observed in three persons. Forty-three of the 170 workers were evaluable for investigating the effect of TCDD on porphyrin levels. No significant correlation was found between TCDD concentration in adipose tissue and the level of uroporphyrin and coproporphyrin. The influence of a chloracne history is described.

Adipose Tissue↗

PubMed1993

Interaction of brain mitochondria with microtubules reconstituted from brain tubulin and MAP2 or TAU.

To explore the behaviour of microtubule-associated proteins, MAP2 and TAU in the interactions of mitochondria with microtubules, an homologous acellular system has been reconstituted with organelles isolated from rat brain. We have established a quantitative in vitro binding assay based on the cosedimentation of 125I-labeled microtubules with mitochondria. We found that binding of microtubules to mitochondria was concentration dependent and saturable. Binding was insensitive to ATP. A comparison of taxol-stabilized microtubules prepared from MAP-free tubulin or tubulin coated with TAU or MAP2 showed that the microtubule-associated proteins diminished, or reduced to background levels, the formation of complexes with mitochondria. In contrast, the amount of MAP-free taxol microtubules that cosedimented with mitochondria increased two- and six-fold when mitochondria were coated with MAP2 or TAU. These studies suggest that the two major brain MAPs could have a crosslinking or a spacing role, depending on their organelle localization.

Adenosine Triphosphate↗