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Biomedical subjects

C Klein

Publications and source records attributed to C Klein.

At least 253 records · Page 14Linked to original sources
PubMed1996

Nerve conduction abnormalities in the arms of patients with arteriovenous fistula.

Fifteen patients with unilateral functioning arteriovenous fistula were assessed clinically and electromyographically to identify local neurologic changes. Ten of the patients were symptomatic (motor and/or sensory) and 5 were asymptomatic. Clinically, 11 patients had signs of a mild polyneuropathy, 2 patients of ulnar neuropathy, and 1 patient had signs of median neuropathy. A decrease of the above-elbow ulnar conduction velocity was noted in the study group on the side of the functional fistula, and in the symptomatic patients only on the side of the nonfunctional/nonexisting fistula. We suggest that ulnar nerve vulnerability should be taken into consideration during construction of the fistula, as well as during dialysis.

Adult↗
PubMed1996

[Mandibular micrognathism as a sequela of early childhood capitulum fractures and their treatment using distraction osteogenesis].

We report about our experience in five patients who suffered from a mandibular micrognathia after ancylosis of the temporomandibular joint. At first the ancylosis was removed using a costochondral graft. About one year later, the mandible was cut by an osteotomy behind the last visible toothbud and a distractor was inserted. The mandible was to a slide overcorrection. This has to be taken into account to compensate a certain relapse. At first we used an unidirectional device, for one and a half years we have used a bidirectional device (Normed from Tuttlingen/Germany) which enables us to correct mandibular hypoplasias more adequately. Up to now our experience shows, that gradual callus-distraction leads to stable normalization of mandibular hypoplasias. Functional problems concerning chewing and speech are solved, the dramatical improvement of the profile of the face may avoid psycho-social problems for these patients.

Adolescent↗
PubMed1996

Recirculatory pharmacokinetic models of markers of blood, extracellular fluid and total body water administered concomitantly.

Pharmacokinetic models were developed to describe the disposition of markers of extracellular fluid (inulin) and total body water (antipyrine) from the moment of injection to incorporate the intravascular mixing component, determined by a marker of intravascular space (indocyanine green, ICG). The simultaneous dispositions of these markers were characterized in four halothane-anesthetized dogs. After injection of ICG, [14C]-inulin, and antipyrine into the right atrium, femoral arterial blood samples were collected every 3 sec for 1 min and less frequently to 20 min for ICG and to 360 min for inulin and antipyrine. ICG and antipyrine concentrations were measured by high-performance liquid chromatography and [14C]-inulin concentrations were measured by liquid scintillation counting. The marker concentration histories were characterized completely by fully identifiable recirculatory compartmental models. Because neither ICG nor inulin distribute beyond intravascular space before recirculation, their first-pass data were modelled simultaneously to improve confidence in central circulation model parameters. This central circulation model included an estimate of cardiac output that was retained in the recirculatory models of all markers. Three tissue compartments were identified for antipyrine, a lipid soluble marker that equilibrates with tissue (including the lung) and estimates total body water and tissue blood flow. The hydrophilic marker, inulin, diffuses into interstitial fluid so slowly that only two extravascular compartments were identified. These models may be used to determine how cardiac output and its distribution, pulmonary drug uptake, and nondistributive blood flow contribute to variability in patient response to drugs with a rapid onset of effect.

Animals↗
PubMed1995

Cloning of a cDNA encoding a novel heat-shock protein from Dictyostelium discoideum.

We have cloned, from Dictyostelium discoideum, a cDNA encoding a new heat-shock (HS) protein (Hsp) with a predicted molecular mass of 31,447 Da. Outside of its low molecular mass, this Hsp does not share any similarity with the small Hsp currently identified or with alpha-crystallins. Northern blot analysis indicates that this HS-inducible gene is also developmentally regulated .

Amino Acid Sequence↗
PubMed1995

Establishment of micrometastatic carcinoma cell lines: a novel source of tumor cell vaccines.

BACKGROUND: Cancer cells of microscopic metastases can be envisaged as ideal constituents for the development of a genetically modified, autologous tumor cell vaccine. However, their extremely low number has thus far blocked this approach. PURPOSE: The aim of this study was to culture micrometastatic tumor cells present in bone marrow of patients with various forms of epithelial cancer and to thereby establish immortalized cell lines. METHODS: Bone marrow aspirates from the upper iliac crest of 152 patients with cancer of the prostate, kidney, lung, breast, or colorectum were cultured at 1 x 10(7) to 6 x 10(7) mononuclear cells (MNC) per flask in fetal calf serum-containing RPMI-1640 medium supplemented with 10 ng/mL epidermal growth factor and 10 ng/mL basic fibroblast growth factor. The proliferation of epithelial cells on extracellular matrix-coated plates was monitored by sampling and staining aliquots with cytokeratin-specific antibodies. After 3-6 weeks in culture, the cells were transferred to Petri dishes, and 200-300 epithelial cells per plate were microinjected with DNA encoding for the simian virus 40 (SV40) large T antigen. Cells were screened at various time points for expression of large T antigen and epithelial markers, such as cytokeratins, prostate-specific antigen, prolactin-inducible protein, or intestinal-specific annexin; their bone marrow-seeking potential was tested in immunodeficient SCID (i.e., severe combined immunodeficiency) mice given subcutaneous transplants of the immortalized cells. RESULTS: Prior to culture, more than 90% of all samples presented with fewer than 10 tumor cells per 8 x 10(5) MNC. In 68 cases (44.7%), the established culture conditions allowed a two to four log transient expansion of these cells with rather small differences among the tumor types studied. Epidermal growth factor and basic fibroblast growth factor were found to be essential for this culture system. After microinjection of the propagated cells with T-antigen DNA, permanent cell lines were obtained; some of these cell lines (prostate and lung cancer cell lines) are now beyond culture passage 80. The cells showed no notable changes in the pattern of expressed epithelial antigens and were able to disseminate into bone marrow in SCID mice. CONCLUSIONS: This procedure allows the selective immortalization of micrometastatic carcinoma cells. Integration of SV40 DNA and expression of T antigen did not substantially change the epithelial phenotype of the propagated cells. IMPLICATIONS: The established system will allow an in-depth molecular analysis of human micrometastatic cancer cells and could become a useful source for the generation of autologous tumor cell vaccines.

Animals↗
PubMed1995

Towards structure-based drug design: crystal structure of a multisubstrate adduct complex of glycinamide ribonucleotide transformylase at 1.96 A resolution.

An inhibitor complex structure of glycinamide ribonucleotide transformylase (GAR-Tfase; EC 2.1.2.2) from Escherichia coli has been determined with a multisubstrate adduct BW1476U89 to an R-value of 19.1% at 1.96 A resolution. The structure was determined by a combination of molecular and single isomorphous replacement using data from two different monoclinic crystal lattices and collecting data from crystals soaked in 20% (w/v) methyl-pentanediol as cryoprotectant for shock-freezing at -150 degrees C. The multisubstrate adduct is bound in an extended crevice at the interface between the two functional domains of the enzyme. This inhibitor is positioned in the binding site by three sets of tight interactions with its phosphate, glutamate and pyrimidone ring moieties, while its interventing linker atoms are more flexible and adopt two distinct sets of conformations. The highly conserved Arg103, His108 and Gln170 residues that are key in ligand binding and catalysis (His108), have compensatory conformational variation that gives some clues as to their role in substrate specificity and in the formyl transfer. The molecular design of 1476U89 as a multisubstrate adduct inhibitor (Ki approximately 100 pM at pH 8.5), is confirmed as it closely mimics the shape, molecular interaction and combined binding constants of the natural 10-formyltetrahydrofolate (10-CHO-H4F; Km approximately 77.4 microM at pH 8.5) and glycinamide-ribonucleotide (GAR; Km approximately 8.1 microM at pH 8.5) substrates. The stereochemistry of this ligand complex suggests that His108 may act as an electrophile stabilizing the oxyanion of the tetrahedral intermediate that is formed as a result of the direct attack on the 10-CHO-H4F by the amino group of GAR. Structural comparison of the folate binding modes among GAR-Tfase, dihydrofolate reductase and thymidylate synthase reveals that folate derivates bound to GAR-Tfase differentially adopt the trans conformation for the dihedral angle between atoms C-6 and C-9 providing a handle for targeting specific folate-dependent enzymes. The structural information derived from two different discrete conformations of the ligand in the binding site also suggests several leads for the de novo design of inhibitors of GAR-Tfase that may develop into useful chemotherapeutic agents.

Acyltransferases↗
PubMed1995

Cloning and expression of the alpha subunit of succinyl-CoA synthetase from Dictyostelium discoideum.

We have isolated and characterized a genomic fragment and a cDNA clone for the alpha subunit of succinyl-CoA synthetase (SCS) from Dictyostelium discoideum. The coding region predicts a protein of 310 amino acids. Direct amino acid sequence data indicate that the first 16 amino acids encoded by the cDNA comprise a mitochondrial targeting sequence. The predicted molecular mass of the mature protein is 31 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The deduced amino acid sequence of the alpha subunit from D. discoideum shows 75% identity to that from rat liver, which represents a GTP-utilizing form of SCS, and 62% identity to the Escherichia coli protein, which is an ATP-utilizing form. We have previously shown that the enzyme purified from growing D. discoideum is a GTP-utilizing enzyme. In D. discoideum, the alpha subunit is a single copy gene that is developmentally regulated. Highest levels of its mRNA are seen in growing cells, which is followed by a relatively dramatic decline at the time cells complete their aggregation program. In contrast, the level of the protein, as determined by Western blots, remains unchanged throughout development. This indicates that any developmental changes in SCS activity reflect changes in the availability of its substrates or effectors and not changes in the level of enzyme.

Amino Acid Sequence↗
PubMed1995

Lack of glycosyl-phosphatidylinositol anchoring leads to precursor retention by a unique mechanism in Dictyostelium discoideum.

Gp80, a cell-adhesion molecule in Dictyostelium discoideum, is modified by N- and O-linked oligosaccharides, and a glycosylphosphatidylinositol (GPI) anchor. To identify sequences important for the addition of these modifications to gp80, we created a hybrid protein in which the C-terminal 136 amino acids of yeast invertase were replaced by the C-terminal 110 amino acids of gp80. When expressed in D. discoideum, this protein (Inv-gp80) was not GPI-anchored and was retained in a pre-Golgi compartment. Inv-gp80 did, however, display characteristics of a transmembrane protein, suggesting a novel mechanism for its retention. We also expressed a truncated version of the hybrid protein in which the C-terminal 22 amino acids of the Inv-gp80 were deleted. The truncated protein (Inv-gp80stop) was O-glycosylated and secreted. These observations indicate that the hybrid protein is not abnormally folded and demonstrate the importance of the C-terminal 22 amino acids in the retention of Inv-gp80. Together, the data suggest that oligomerization of the protein blocks its GPI anchoring.

Animals↗
PubMed1995

Bone marrow transplantation in major histocompatibility complex class II deficiency: a single-center study of 19 patients.

Major histocompatibility complex (MHC) class II deficiency (bare lymphocyte syndrome) is a rare inborn error of the immune system characterized by impaired antigen presentation and combined immunodeficiency. It causes severe and unremitting infections leading to progressive liver and lung dysfunctions and death during childhood. As in other combined immunodeficiency disorders, bone marrow transplantation (BMT) is considered the treatment of choice for MHC class II deficiency. We analyzed the files of 19 patients who have undergone BMT in our center. Of the 7 patients who underwent HLA-identical BMT, 3 died in the immediate posttransplant period of severe viral infections, whereas the remaining 4 were cured, with recovery of normal immune functions. Of the 12 patients who underwent HLA-haplo-identical BMT, 3 were cured, 1 was improved by partial engraftment, 7 died of infectious complications due to graft failure or rejection, and 1 is still immunodeficient because of engraftment failure. A favorable outcome in the HLA-non-identical BMT group was associated with an age of less than 2 years at the time of transplantation. All the patients with stable long-term engraftment had persistently low CD4 counts after transplantation (105 to 650/microL at last follow up), but no clear susceptibility to opportunistic infections despite persisting MHC class II deficiency on thymic epithelium and other nonhematopoietic cells. We conclude that HLA-identical and -haploidentical BMT can cure MHC class II deficiency, although the success rate of haploidentical BMT is lower than that in other combined immunodeficiency syndromes. HLA-haploidentical BMT should preferably be performed in the first 2 years of life, before the acquisition of chronic virus carriage and sequelae of infections.

Bone Marrow Transplantation↗
PubMed1995

Lengthening of the hypoplastic mandible by gradual distraction in childhood--a preliminary report.

Uni- or bilateral mandibular hypoplasia can be associated with various syndromes or is acquired after early traumatic or inflammatory disease in the temporomandibular joint (TMJ). Early treatment is necessary to avoid consequent impairment of midfacial growth. The standard treatment of these malformations consists of the application of bone grafts which can lead to unpredictable growth. Furthermore, these procedures often require intermaxillary fixation and sometimes blood transfusions. Lengthening of the mandible by gradual distraction, according to the method of Ilizarov, opens new perspectives for interceptive therapy. This paper reports on this method applied in 9 cases of mandibular hypoplasia. Out of 3 bilateral and 6 unilateral mandibular distractions the average amount of bone lengthening was 21 mm, ranging from 15 to 25 mm. In order to facilitate ossification, the mandibles were maintained in external fixation for an average of 9 weeks subsequent to the period of active lengthening. Thereafter, immediate postoperative orthodontic treatment is necessary to avoid a relapse. No complications were noted during the follow-up period (max 17 months).

Adolescent↗
PubMed1995

EBV-associated lymphoproliferative syndrome with a distinct 69 base-pair deletion in the LMP-1 oncogene.

We describe an immunocompetent 12-year-old boy with chronic EBV infection and lymphoid interstitial pneumonitis. Lymph node biopsies showed effacement of the architecture with polymorphic cellular infiltrates, consisting predominantly of T cells and natural killer cells. No clonal rearrangement of TCR or immunoglobulin genes was seen. DNA was extracted from hilar lymph nodes; sequencing of the carboxy terminal region of the latent membrane protein 1 (LMP-1) oncogene revealed a 69 base-pair deletion and four point mutations. Immunosuppressive treatment with prednisone and cyclosporine reversed the lymphadenopathy.

Base Composition↗
PubMed1995

NDT80, a meiosis-specific gene required for exit from pachytene in Saccharomyces cerevisiae.

We describe the identification of a new meiosis-specific gene of Saccharomyces cerevisiae, NDT80. The ndt80 null and point mutants arrest at the pachytene stage of meiosis, with homologs connected by full-length synaptonemal complexes and spindle pole bodies duplicated but unseparated. Meiotic recombination in an ndt80 delta mutant is relatively normal, although commitment to heteroallelic recombination is elevated two- to threefold and crossing over is decreased twofold compared with those of the wild type. ndt80 arrest is not alleviated by mutations in early recombination genes, e.g., SPO11 or RAD50, and thus cannot be attributed to an intermediate block in prophase chromosome metabolism like that observed in several other mutants. The ndt80 mutant phenotype during meiosis most closely resembles that of a cdc28 mutant, which contains a thermolabile p34, the catalytic subunit of maturation-promoting factor. Cloning and molecular analysis reveal that the NDT80 gene maps on the right arm of chromosome VIII between EPT1 and a Phe-tRNA gene, encodes a 627-amino-acid protein which exhibits no significant homology to other known proteins, and is transcribed specifically during middle meiotic prophase. The NDT80 gene product could be a component of the cell cycle regulatory machinery involved in the transition out of pachytene, a participant in an unknown aspect of meiosis sensed by a pachytene checkpoint, or a SPO11- and RAD50-independent component of meiotic chromosomes that is the target of cell cycle signaling.

Amino Acid Sequence↗
PubMed1995

Three-dimensional co-location of RNA polymerase I and DNA during interphase and mitosis by confocal microscopy.

The relative three-dimensional co-location of RNA polymerase I (RPI) and DNA was studied using confocal laser scanning microscopy during interphase and all the steps of mitosis in human cancerous cells. For each step of the cell cycle, immunolabeled RPI molecules and DNA specifically stained with chromomycin A3 were simultaneously imaged at high resolution through numerous optical sections. Then, all the data obtained were used to generate transverse sections, anaglyphs and volumic representations, which are all prerequisite approaches to a representative study of the three-dimensional organization of the nucleolus and the mitotic chromosomes. Our results indicated that in the interphasic nuclei, in which DNA is organized as a regular 3-D network, RPI was present within numerous irregular spheres arranged as several twisted necklaces. During metaphase, RPI labeling was segregated into pairs of spheres and typical crescent-shaped structures; both were centrally located within the set of chromosomes. During anaphase and telophase, a typical central and symmetric arrangement of labeled structures was systematically seen among the decondensing chromosomes, arranged as a regular cylinder and as a hollow half-sphere, respectively. This typical 3-D organization of structures containing RPI relative to DNA is another strong example of the non-random organization of the genome during interphase and mitosis.

Carcinoma, Squamous Cell↗
PubMed1995

[Historical development of surgical wisdom tooth extraction].

Surgical removal of the wisdom teeth is a routine procedure nowadays. Only at the end of the nineteenth century the use of local anesthesia together with the development of radiology led to the establishment of surgical dentistry. Especially the technique of removal of the lower third molar was totally changed and modified many times, depending on the position of the wisdom teeth. First hand instruments were used; later, mechanical devices for bone resection and tooth splitting were employed. Since the 1950s, highly dangerous infections have become rare, thanks to the use of antibiotics. Many publications concerning incision procedure, bone resection and tooth splitting marked the following years.

Germany↗
PubMed1995

[Pseudotransitory ischemic attacks as the initial symptom of multiple system atrophy].

A 59-year-old man presented with an 18-month history of episodes of visual disturbance and dysphagia in association with gait unsteadiness and leg weakness lasting between 45 and 120 min. These episodes were interpreted as vertebrobasilar transitory ischemic attacks. However, they had been preceded by impotence for 6 months. Autonomic function tests remained normal until the age of 62 years when the patient developed documented orthostatic hypotension. Parkinsonism was precipitated by neuroleptic treatment at the age of 59 years, at which time pyramidal signs were evident. The patient was unable to tolerate levodopa preparations and subsequently developed the full clinical picture of pathologically proven multiple system atrophy, dying at age 65, 7 years after his first symptom.

Aged↗
PubMed1994

Increased recruitment of TATA-binding protein to the promoter by transcriptional activation domains in vivo.

The rate at which the TATA-binding protein (TBP) interacts with the TATA element and promotes transcription by RNA polymerase II was determined in yeast cells. A TBP derivative with altered TATA-element specificity was rapidly induced, and transcription from promoters with appropriately mutated TATA elements was measured. Without a functional activator protein, basal transcription was observed only after a lag of several hours. In contrast, GCN4-activated transcription occurred rapidly upon induction of the TBP derivative. These results suggest that accessibility of TBP to the chromatin template in vivo is rate limiting and that activation domains increase recruitment of TBP to the promoter.

Base Sequence↗
PubMed1994

Nitric oxide regulation of glyceraldehyde-3-phosphate dehydrogenase activity in Dictyostelium discoideum cells and lysates.

The ability of compounds releasing nitric oxide (NO) to regulate glyceraldehyde-3-phosphate dehydrogenase (GraPDH) activity was analysed both in cell homogenates and in intact Dictyostelium discoideum. The time course of GraPDH inactivation in cell lysates by NO-releasing compounds suggests that two processes may be involved, one of which accounts for the majority of the inactivation and shows a close correlation with GraPDH ADP-ribosylation. Maximal ADP-ribosylation under these conditions exhibited a stoichiometry of about 0.4 mol ADP-ribose/mol enzyme tetramer. NO-mediated inhibition of GraPDH activity was attenuated if specific substrates, cofactors, or cysteine were added to cytosol preparations. Under such conditions, ADP-ribosylation of the enzyme was correspondingly reduced or negligible. Intact cells treated with NO-releasing compounds were shown to respond by rapidly decreasing their GraPDH activity. This inhibition was transient and, after a 10-min incubation, enzyme activity returned to the level seen in control cells. The time course of these in vivo changes correlated well with those of the NO-stimulated ADP-ribosylation of GraPDH also seen in intact cells. The basis underlying the NO-stimulated inhibition of GraPDH activity was investigated and found to reflect a decreased Vmax. No changes in either the Km of the enzyme for its substrates or its state of polymerization were observed.

Adenosine Diphosphate Ribose↗