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Biomedical subjects

J Kuhn

Publications and source records attributed to J Kuhn.

At least 19 recordsLinked to original sources
PubMed2003

The transmembrane domain of the DnaJ-like protein DjlA is a dimerisation domain.

DjlA is a bitopic inner membrane protein, which belongs to the DnaJ co-chaperone family in Escherichia coli. Overproduction of DjlA leads to the synthesis of colanic acid, resulting in mucoidy, via the activation of the two-component regulatory system RcsC/B that controls the cps (capsular polysaccharide) operon. This induction requires both the co-chaperone activity of DjlA, in cooperation with DnaK and GrpE, and its unique transmembrane (TM) domain. Here, we show that the TM segment of DjlA acts as a dimerisation domain: when fused to the N-terminal DNA-binding domain of the lambda cI repressor protein, it can substitute for the native C-terminal dimerisation domain of cI, thus generating an active cI repressor. Replacing the TM domain of DjlA by other TM domains, with or without dimerising capacity, revealed that dimerisation is not sufficient for the induction of cps expression, indicating an additional sequence- or structurally specific role for the TM domain. Finally, the conserved glycines present in the TM domain of DjlA are essential for the induction of mucoidy, but not for dimerisation.

Amino Acid Sequence↗
PubMed2003

[Social status and health of young people in the German Federal State of Brandenburg].

UNLABELLED: In the German Federal State of Brandenburg, reporting on health and social issues is closely linked. This also applies to the present article, which attempts to describe the social and health situation of young people in Brandenburg. The aim is to define future priorities in health prevention. METHODS: In addition to data from official statistics (on demographic trends, employment and social security) and from surveys conducted among young adults, the results from serial medical and dental examinations of 10th-grade pupils are presented. RESULTS: The number of young citizens in Brandenburg aged 16-25 will rise until the middle of the decade but then fall sharply. This will apply in particular to the rural areas far from Berlin. Sociological studies show that "work and family" enjoy the highest priority among people. However, less educated young people are increasingly doubtful about their ability to live their lives according to these priorities. According to medical statistics, every tenth young person suffers from allergies (especially allergic rhinitis). The same applies with regard to orthopaedic data. Approx. 5% of young people are obese, pupils of special schools more frequently than grammar school pupils. DISCUSSION: Healthy schooling, healthy professional training and good opportunities on the labour market are the key pillars of health policy in Brandenburg. The social and health situation of young people in Brandenburg is a complex issue and can only be improved by networking and cooperation among of all parties concerned.

Adolescent↗
PubMed2001

Netrin signal is produced in leech embryos by segmentally iterated sets of central neurons and longitudinal muscle cells.

Abstract. Netrins are secreted molecules capable of attracting or repelling growing axons. They and their receptors, along with other netrin-interacting proteins, are widely conserved among animals from a broad range of phyla. We have raised and purified an antibody against a recently cloned leech netrin, which has allowed us to characterize embryonic netrin expression by cells in peripheral tissues and in the central nervous system. During early gangliogenesis, netrin expression was detected at particularly high levels in five bilateral pairs of central neurons. Towards the end of the period of axonal outgrowth, netrin expression was observed to be restricted to only six central neurons, comprising two bilateral pairs and two unpaired cells. A pair of netrin-producing central neurons, the bipolar cells, was identified by their expression of the antigen recognized by the monoclonal antibody Laz1-1. Double staining of sensory afferents from segmental sensilla with the monoclonal antibody Lan3-2 and the bipolar cells with the netrin antibody revealed that the terminals of these afferents grow up to the bipolar cells and turn anteriorly or posteriorly, without extending any further medially. Peripheral netrin expression was found to be restricted to longitudinal muscle cells in the ventral half of the body wall. Extracellular, secreted netrin was detected in a broad longitudinal stripe located symmetrically with respect to the ventral midline. The pattern of expression of netrin in leech embryos is consistent with observed expression patterns in other animals, suggesting that developmental netrin functions are conserved among all bilateral animals.

Animals↗
PubMed2001

Phase I and pharmacokinetic study of NSC 655649, a rebeccamycin analog with topoisomerase inhibitory properties.

PURPOSE: To assess the feasibility of administering NSC 655649, a water-soluble, rebeccamycin analog with topoisomerase inhibitory properties, as a brief intravenous (IV) infusion once every 3 weeks and to determine the maximum-tolerated dose (MTD) of NSC 655649, characterize its pharmacokinetic behavior, and seek preliminary evidence of antitumor activity. PATIENTS AND METHODS: Patients with advanced solid malignancies were treated with escalating doses of NSC 655649 administered over 30 to 60 minutes IV once every 3 weeks. An accelerated dose-escalation method was used to guide dose escalation. After three patients were treated at the first dose level, doses were escalated in increments that ranged up to 150% using single patient cohorts until moderate toxicity was observed, when a more conservative dose-escalation scheme was invoked. MTD was defined as the highest dose level at which the incidence of dose-limiting toxicity did not exceed 20%. MTD was determined for both minimally pretreated (MP) and heavily pretreated (HP) patients. Plasma and urine were sampled to characterize the pharmacokinetic and excretory behavior of NSC 655649. RESULTS: Forty-five patients were treated with 130 courses of NSC 655649 at doses ranging from 20 mg/m(2) to 744 mg/m(2). Myelosuppression was the principal toxicity. Severe neutropenia, which was often associated with thrombocytopenia, was unacceptably high in HP and MP patients treated at 572 mg/m(2) and 744 mg/m(2), respectively. Nausea, vomiting, and diarrhea were common but rarely severe. The pharmacokinetics of NSC 655649 were dose dependent and fit a three-compartment model. The clearance and terminal elimination half-lives for NSC 655649 averaged 7.57 (SD = 4.2) L/h/m(2) and 48.85 (SD = 23.65) hours, respectively. Despite a heterogeneous population of MP and HP patients, the magnitude of drug exposure correlated well with the severity of myelosuppression. Antitumor activity was observed in two HP ovarian cancer patients and one patient with a soft tissue sarcoma refractory to etoposide and doxorubicin. CONCLUSION: Recommended phase II doses are 500 mg/m(2) and 572 mg/m(2) IV once every 3 weeks for HP and MP patients, respectively. The absence of severe nonhematologic toxicities, the encouraging antitumor activity in HP patients, and the unique mechanism of antineoplastic activity of NSC 655649 warrant further clinical development.

Adult↗
PubMed2001

Sulfated tyrosines contribute to the formation of the C5a docking site of the human C5a anaphylatoxin receptor.

The complement anaphylatoxin C5a and its seven-transmembrane segment (7TMS) receptor play an important role in host defense and in a number of inflammation-associated pathologies. The NH(2)-terminal domain of the C5a receptor (C5aR/CD88) contributes substantially to its ability to bind C5a. Here we show that the tyrosines at positions 11 and 14 of the C5aR are posttranslationally modified by the addition of sulfate groups. The sulfate moieties of each of these tyrosines are critical to the ability of the C5aR to bind C5a and to mobilize calcium. A C5aR variant lacking these sulfate moieties efficiently mobilized calcium in response to a small peptide agonist, but not to C5a, consistent with a two-site model of ligand association in which the tyrosine-sulfated region of the C5aR mediates the initial docking interaction. A peptide based on the NH(2) terminus of the C5aR and sulfated at these two tyrosines, but not its unsulfated analogue or a doubly sulfated control peptide, partially inhibited C5a association with its receptor. These observations clarify structural and mutagenic studies of the C5a/C5aR association and suggest that related 7TMS receptors are also modified by functionally important sulfate groups on their NH(2)-terminal tyrosines.

Amino Acid Sequence↗
PubMed2001

Observation of exotic meson production in the reaction pi- p --> eta'pi- p at 18 GeV/c.

An amplitude analysis of an exclusive sample of 5765 events from the reaction pi- p-->eta'pi- p at 18 GeV/c is described. The eta'pi- production is dominated by natural parity exchange and by three partial waves: those with J(PC) = 1(-+), 2(++), and 4(++). A mass-dependent analysis of the partial-wave amplitudes indicates the production of the a2(1320) meson as well as the a4(2040) meson, observed for the first time decaying to eta'pi-. The dominant, exotic (non- qq) 1(-+) partial wave is shown to be resonant with a mass of 1.597+/-0.010(+0.045)(-0.010) GeV/c2 and a width of 0.340+/-0.040+/-0.050 GeV/c2. This exotic state, the pi1(1600), is produced with a t dependence which is different from that of the a2(1320) meson, indicating differences between the production mechanisms for the two states.

Journal Article↗
PubMed2001

Phase II trial of intratumoral administration of ONYX-015, a replication-selective adenovirus, in patients with refractory head and neck cancer.

PURPOSE: To determine the safety, humoral immune response replication, and activity of multiple intratumoral injections of ONYX-015 (replication selective adenovirus) in patients with recurrent squamous cell carcinoma of the head and neck (SCCHN). PATIENTS AND METHODS: This phase II trial enrolled patients with SCCHN who had recurrence/relapse after prior conventional treatment. Patients received ONYX-015 at a dose of 2 x 10(11) particles via intratumoral injection for either 5 consecutive days (standard) or twice daily for 2 consecutive weeks (hyperfractionated) during a 21-day cycle. Patients were monitored for tumor response, toxicity, and antibody formation. RESULTS: Forty patients (30 standard and 10 hyperfractionated) received 533 injections of ONYX-015. Standard treatment resulted in 14% partial to complete regression, 41% stable disease, and 45% progressive disease rates. Hyperfractionated treatment resulted in 10% complete response, 62% stable disease, and 29% progressive disease rates. Treatment-related toxicity included mild to moderate fever (67% overall) and injection site pain (47% on the standard regimen, 80% on the hyperfractionated regimen). Detectable circulating ONYX-015 genome suggestive of intratumoral replication was identified in 41% of tested patients on days 5 and 6 of cycle 1; 9% of patients had evidence of viral replication 10 days after injection during cycle 1, and no patients had evidence of replication > or = 22 days after injection. CONCLUSION: ONYX-015 can be safely administered via intratumoral injection to patients with recurrent/refractory SCCHN. ONYX-015 viremia is transient. Evidence of modest antitumoral activity is suggested.

Adenovirus E1B Proteins↗
PubMed2001

The bacteriophage lambda attachment site in wild strains of Escherichia coli.

The attachment site (attlambda) of bacteriophage lambda was examined in wild strains of Escherichia coli. Although the att region is non-coding, the DNA sequence was invariant in the 13 strains examined. Two other non-coding regions showed nine changes, all associated with a single strain. In four of 33 strains, sequences were inserted in or near the attlambda site and in two of these the insert was related to lambda. Among strains that can be lysogenized by lambda, integration was via the attlambda site in all cases. Some resistant strains can be lysogenized, and these have been termed "lenient." Most of these fail to give normal phage yield after induction. In some cases rare lysogens have been formed in cells that belong to a mutant subpopulation.

Bacteriophage lambda↗
PubMed2001

The RNA world of plant mitochondria.

Mitochondria are well known as the cellular power factory. Much less is known about these organelles as a genetic system. This is particularly true for mitochondria of plants, which subsist with respect to attention by the scientific community in the shadow of the chloroplasts. Nevertheless the mitochondrial genetic system is essential for the function of mitochondria and thus for the survival of the plant. In plant mitochondria the pathway from the genetic information encoded in the DNA to the functional protein leads through a very diverse RNA world. How the RNA is generated and what kinds of regulation and control mechanisms are operative in transcription are current topics in research. Furthermore, the modes of posttranscriptional alterations and their consequences for RNA stability and thus for gene expression in plant mitochondria are currently objects of intensive investigations. In this article current results obtained in the examination of plant mitochondrial transcription, RNA processing, and RNA stability are illustrated. Recent developments in the characterization of promoter structure and the respective transcription apparatus as well as new aspects of RNA processing steps including mRNA 3' processing and stability, mRNA polyadenylation, RNA editing, and tRNA maturation are presented. We also consider new suggestions concerning the endosymbiont hypothesis and evolution of mitochondria. These novel considerations may yield important clues for the further analysis of the plant mitochondrial genetic system. Conversely, an increasing knowledge about the mechanisms and components of the organellar genetic system might reveal new aspects of the evolutionary history of mitochondria.

Base Sequence↗
PubMed2001

Centrosomes and the Scrambled protein coordinate microtubule-independent actin reorganization.

In Drosophila syncytial blastoderm embryos, centrosomes specify the position of actin-based interphase caps and mitotic furrows. Mutations in the scrambled locus prevent assembly of mitotic furrows, but do not block actin cap formation. The scrambled gene encodes a protein that localizes to the mitotic furrows and centrosomes. Sced localization, actin reorganization from caps into mitotic furrows, and centrosome-coordinated assembly of actin caps are not blocked by microtubule disruption. Our results indicate that centrosomes may coordinate assembly of cortical actin caps through a microtubule-independent mechanism, and that Scrambled mediates a second microtubule-independent process that drives mitotic furrow assembly.

Actins↗
PubMed2001

Gamma probe guided biopsy of the sentinel node in malignant melanoma: a multicentre study.

Sentinel lymph node biopsy was attempted in 336 patients with clinically node-negative cutaneous melanoma. All patients were injected with technetium-99m labelled radiocolloid, with 108 patients simultaneously receiving vital blue dye for sentinel node identification. Sentinel lymph nodes were identified in 329 patients, giving a technical success rate of 97.9%. Metastatic disease was identified in 39 (11.9%) of the patients in whom sentinel nodes were found. Patients with negative sentinel nodes were observed and patients with positive sentinel nodes underwent comprehensive lymph node dissection. The presence of metastatic disease in the sentinel nodes and primary tumour depth by Breslow or Clark levels were joint predictors of survival based on Cox proportional hazards modelling. Disease recurrences occurred in 26 (8.8%) patients with negative sentinel lymph nodes, with isolated regional recurrences as the first site in 10 (3.4%). No patients with Clark level II primary tumours were found to have positive sentinel nodes or disease recurrences. One patient with a thin (<0.75 mm) Clark level III primary had metastatic disease in a sentinel node. Patients with metastases confined to the sentinel nodes had similar survival rates regardless of the number of nodes involved.

Adolescent↗
PubMed2001

Transcript lifetime is balanced between stabilizing stem-loop structures and degradation-promoting polyadenylation in plant mitochondria.

To determine the influence of posttranscriptional modifications on 3' end processing and RNA stability in plant mitochondria, pea atp9 and Oenothera atp1 transcripts were investigated for the presence and function of 3' nonencoded nucleotides. A 3' rapid amplification of cDNA ends approach initiated at oligo(dT)-adapter primers finds the expected poly(A) tails predominantly attached within the second stem or downstream of the double stem-loop structures at sites of previously mapped 3' ends. Functional studies in a pea mitochondrial in vitro processing system reveal a rapid removal of the poly(A) tails up to termini at the stem-loop structure but little if any influence on further degradation of the RNA. In contrast 3' poly(A) tracts at RNAs without such stem-loop structures significantly promote total degradation in vitro. To determine the in vivo identity of 3' nonencoded nucleotides more accurately, pea atp9 transcripts were analyzed by a direct anchor primer ligation-reverse transcriptase PCR approach. This analysis identified maximally 3-nucleotide-long nonencoded extensions most frequently of adenosines combined with cytidines. Processing assays with substrates containing homopolymer stretches of different lengths showed that 10 or more adenosines accelerate RNA processivity, while 3 adenosines have no impact on RNA life span. Thus polyadenylation can generally stimulate the decay of RNAs, but processivity of degradation is almost annihilated by the stabilizing effect of the stem-loop structures. These antagonistic actions thus result in the efficient formation of 3' processed and stable transcripts.

Arabidopsis Proteins↗
PubMed2001

Low proliferative rate of invasive node-negative breast cancer predicts for a favorable outcome: a prospective evaluation of 669 patients.

This study was designed to compare outcome in terms of disease-free survival (DFS) in women with histologically negative axillary lymph nodes and documented low proliferative rate cancer to other well-defined prognostic factors including type of adjuvant treatment. Between 1988 and 1998, we studied 669 patients with invasive node-negative breast cancer up to 5 cm in size and low proliferative rate measured by flow cytometry to determine S-phase fraction (SPF) or by histochemistry (Ki67/MIB1). At a median follow-up of 53 months, 5-year DFS for the entire group was 94% and did not differ significantly by type of systemic adjuvant treatment: none (133 patients, 95% DFS), tamoxifen (441 patients, 94% DFS), or chemotherapy with doxorubicin and cyclophosphamide (95 patients, 92% DFS). In a multivariate prognostic factor analysis, only tumor size was significant; 5-year DFS was 96% for T1N0 cancer versus 89% for T2N0 cancer (P = 0.01). We have prospectively confirmed that a low rate of proliferation as measured by SPF or MIB1 determination confers an excellent prognosis in invasive node-negative breast cancer up to 5 cm in size, regardless of adjuvant treatment.

Adult↗
PubMed2000

Molecular cloning and expression of human UDP-d-Xylose:proteoglycan core protein beta-d-xylosyltransferase and its first isoform XT-II.

Human UDP-d-xylose:proteoglycan core protein beta-d-xylosyltransferase (EC 2.4.2.26, XT-I) initiates the biosynthesis of glycosaminoglycan chains in proteoglycans by transferring xylose from UDP-xylose to specific serine residues of the core protein. Based on the partial amino acid sequence of the purified enzyme from human JAR choriocarcinoma cell culture supernatant we isolated a cDNA encoding XT-I using the degenerate reverse transcriptase-polymerase chain reaction method. This enzyme, which is involved in chondroitin sulfate, heparan sulfate, heparin and dermatan sulfate biosynthesis, belongs to a novel family of glycosyltransferases with no homology to proteins known so far. 5' and 3'-RACE were performed to isolate a novel cDNA fragment of 3726 bp with a single open reading frame encoding at least 827 amino acid residues with a molecular mass of 91 kDa. The human XT-I gene was located on chromosome 16p13.1 using radiation hybrid mapping, and extracts from CHO-K1 cells transfected with the XT-I cDNA in an expression vector exhibited marked XT activity. A new 3608 bp cDNA fragment encoding a protein of 865 amino acid residues was also isolated by PCR using degenerate primers based on the amino acid sequence of human XT-I. The amino acid sequence of this XT-II isoform displayed 55% identity to the human XT-I. The XT-II gene was located on chromosome 17q21.3-17q22, and the exon/intron structure of the 15 kb gene was determined. RT-PCR analyses of XT-I and XT-II mRNA from various tissues confirmed that both XT-I and XT-II transcripts are ubiquitously expressed in the human tissues, although with different levels of transcription. Furthermore, the cDNAs encoding XT-I and XT-II from rat were cloned. The deduced amino acid sequences of rat xylosyltransferases displayed 94% identity to the corresponding human enzyme.

Amino Acid Sequence↗
PubMed2000

First isolation of human UDP-D-xylose: proteoglycan core protein beta-D-xylosyltransferase secreted from cultured JAR choriocarcinoma cells.

Human UDP-d-xylose:proteoglycan core protein beta-d-xylosyltransferase (EC, XT) initiates the biosynthesis of glycosaminoglycan lateral chains in proteoglycans by transfer of xylose from UDP-xylose to specific serine residues of the core protein. In this study, we report the first isolation of the XT and present the first partial amino acid sequence of this enzyme. We purified XT 4,700-fold with 1% yield from serum-free JAR choriocarcinoma cell culture supernatant. The isolation procedure included a combination of ammonium sulfate precipitation, heparin affinity chromatography, ion exchange chromatography, and protamine affinity chromatography. Among other proteins an unknown protein was detected by matrix-assisted laser desorption ionization mass spectrometry-time of flight analysis in the purified sample. The molecular mass of this protein was determined as 120 kDa by SDS-polyacrylamide gel electrophoresis. The isolated protein was enzymatically cleaved by trypsin and endoproteinase Lys-C. Eleven peptide fragments were sequenced by Edman degradation. Searches with the amino acid sequences in protein and EST data bases showed no homology to known sequences. XT was enriched by immunoaffinity chromatography with an immobilized antibody against a synthetic peptide deduced from the sequenced peptide fragments and was specifically eluted with the antigen. In addition, XT was purified alternatively with an aprotinin affinity chromatography and was detected by Western blot analysis in the enzyme-containing fraction.

Amino Acid Sequence↗
PubMed2000

Selective replication and oncolysis in p53 mutant tumors with ONYX-015, an E1B-55kD gene-deleted adenovirus, in patients with advanced head and neck cancer: a phase II trial.

ONYX-015 is an E1B-55kDa gene-deleted adenovirus engineered to selectively replicate in and lyse p53-deficient cancer cells. To evaluate the selectivity of ONYX-015 replication and cytopathic effects for the first time in humans, we carried out a Phase II clinical testing of intratumoral and peritumoral ONYX-015 injection in 37 patients with recurrent head and neck carcinoma. Patients received ONYX-015 at a daily dose of 1 x 10(10) plaque-forming units (pfu) via intratumoral injection for 5 days during week 1 of each 3-week cycle (n = 30; cohort A), or 1 x 10(10) pfu twice a day for 10 days during weeks 1 and 2 of each 3-week cycle. Posttreatment biopsies documented selective ONYX-015 presence and/or replication in the tumor tissue of 7 of 11 patients biopsied on days 5-14, but not in immediately adjacent normal tissue (0 of 11 patients; P = 0.01). Tissue destruction was also highly selective; significant tumor regression (>50%) occurred in 21% of evaluable patients, whereas no toxicity to injected normal peritumoral tissues was demonstrated. p53 mutant tumors were significantly more likely to undergo ONYX-015-induced necrosis (7 of 12) than were p53 wild-type tumors (0 of 7; P = 0.017). High neutralizing antibody titers did not prevent infection and/or replication within tumors. ONYX-015 is the first genetically engineered replication-competent virus to demonstrate selective intratumoral replication and necrosis in patients. This agent demonstrates the promise of replication-selective viruses as a novel therapeutic platform against cancer.

Adenovirus E1B Proteins↗
PubMed2000

Identification of residues important both for primary receptor binding and specificity in fibroblast growth factor-7.

Fibroblast growth factors (FGFs) mediate a multitude of physiological and pathological processes by activating a family of tyrosine kinase receptors (FGFRs). Each FGFR binds to a unique subset of FGFs and ligand binding specificity is essential in regulating FGF activity. FGF-7 recognizes one FGFR isoform known as the FGFR2 IIIb isoform or keratinocyte growth factor receptor (KGFR), whereas FGF-2 binds well to FGFR1, FGFR2, and FGFR4 but interacts poorly with KGFR. Previously, mutations in FGF-2 identified a set of residues that are important for high affinity receptor binding, known as the primary receptor-binding site. FGF-7 contains this primary site as well as a region that restricts interaction with FGFR1. The sequences that confer on FGF-7 its specific binding to KGFR have not been identified. By utilizing domain swapping and site-directed mutagenesis we have found that the loop connecting the beta4-beta5 strands of FGF-7 contributes to high affinity receptor binding and is critical for KGFR recognition. Replacement of this loop with the homologous loop from FGF-2 dramatically reduced both the affinity of FGF-7 for KGFR and its biological potency but did not result in the ability to bind FGFR1. Point mutations in residues comprising this loop of FGF-7 reduced both binding affinity and biological potency. The reciprocal loop replacement mutant (FGF2-L4/7) retained FGF-2 like affinity for FGFR1 and for KGFR. Our results show that topologically similar regions in these two FGFs have different roles in regulating receptor binding specificity and suggest that specificity may require the concerted action of distinct regions of an FGF.

3T3 Cells↗