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Biomedical subjects

C Klein

Publications and source records attributed to C Klein.

At least 271 records · Page 15Linked to original sources
PubMed1994

Sphingolipid activator protein D (sap-D) stimulates the lysosomal degradation of ceramide in vivo.

Glycosphingolipids of cultured fibroblasts from patients with total sphingolipid activator proteins (SAPs) deficiency (Schnabel et al. J. Biol. Chem. 267:3312-3315, 1992) were labeled biosynthetically with [14C]serine. After a chase period of 120h the patients' fibroblasts showed increased labeling of ceramide, glucosylceramide, lactosylceramide and ganglioside GM3 in comparison to normal control cells. Addition of sap-D to the chase-media of the patients' fibroblasts led to the degradation of the accumulated ceramide down to nearly normal levels, whereas the levels of other labeled sphingolipids remained unaffected. In contrast, addition of sap-B to the chase-media of the patients' fibroblasts did not reduce the increased ceramide levels but resulted, as expected from in vitro experiments, in a specific decrease of levels of lactosylceramide and ganglioside GM3. Therefore, we conclude that sap-D stimulates in vivo the lysosomal degradation of ceramide.

Cells, Cultured↗
PubMed1994

The UV response involving the Ras signaling pathway and AP-1 transcription factors is conserved between yeast and mammals.

UV irradiation of mammalian cells activates AP-1 through a Ras-dependent pathway, independently of DNA damage. We show that the yeast S. cerevisiae has a remarkably similar UV response involving the AP-1 factor Gcn4, which is distinct from the DNA damage response. Transcriptional activation of HIS3 and HIS4 by Gcn4 is triggered by UV irradiation in a Ras-dependent fashion. Moreover, resistance of yeast to UV irradiation is correlated with the level of Ras activity and Gcn4 function. Like mammalian cells in which activated Ras leads to increased c-Jun synthesis and phosphorylation, the effects in yeast involve increased translation of GCN4 mRNA and a posttranslational event. However, this effect on GCN4 translation is different from the response to amino acid or purine starvation. Therefore, a UV signaling pathway involving Ras and AP-1 is an ancient and universal mechanism involved in protection against damage to cellular components other than DNA.

Amitrole↗
PubMed1994

High levels of interleukin-6 are associated with low tumor burden and low growth fraction in multiple myeloma.

Interleukin-6 (IL-6) is a multifunctional cytokine postulated to play a central role as a growth factor for multiple myeloma (MM). We evaluated the spontaneous secretion of IL-6 in supernatants of Ficoll-Hypaque--enriched bone marrow (BM) cultures from 35 patients with MM. The levels of IL-6 were correlated with biological and clinical characteristics of the disease. High levels of IL-6 production defined a subgroup of patients with low tumor burden as determined by lower serum beta 2-microglobulin (B2M) (P = .02) and lower percentage of myeloma cells infiltrating the bone marrow (P = .003), higher synthetic rates of monoclonal protein (P = .006), and low proliferative compartments as measured by the percentage of Ki-67--positive myeloma cells. Patients with high proliferative fractions (Ki-67--positive myeloma cells > 20%) had significantly lower levels of IL-6 when compared with patients with low proliferative fractions (P = .005). Our findings do not support IL-6 as a major growth factor for MM, but demonstrate an association of high levels of IL-6 secretion with low tumor cell burden and low proliferative fraction.

Aged↗
PubMed1994

Regulatory role of GDP in the phosphoenzyme formation of guanine nucleotide: specific forms of succinyl coenzyme A synthetase.

We have previously shown that micromolar concentrations of GDP stimulate the GTP-mediated phosphorylation of p36, the alpha subunit of succinyl-CoA synthetase (SCS), in lysates prepared from Dictyostelium discoideum. In this study, we report that this phenomenon represents an enhanced catalytic capacity of SCS to form the phosphoenzyme intermediate. Low concentrations of GDP stimulate phosphoenzyme formation by either GTP, or succinyl-CoA and P(i). Under these conditions GDP enhances the apparent rate of phosphoenzyme formation but does not significantly alter the fraction of phosphorylated enzyme. This effect is retained during purification of the protein and is also observed with purified pig heart SCS, indicating that GDP directly alters the enzyme to enhance its rate of phosphorylation. Under these conditions, GDP does not function at the catalytic site, implying an allosteric regulation of SCS.

Allosteric Regulation↗
PubMed1994

Osseous substance formation induced in porous calcium phosphate ceramics in soft tissues.

Porous calcium phosphate ceramics prepared according to the methods of laboratories in Leiden were implanted subcutaneously in rats for 3, 6 and 12 w. No bone formation could be observed. Porous calcium phosphate ceramics prepared according to the methods of laboratories in Sichuan were implanted subcutaneously/intramuscularly in dogs for 1, 3, 5 and 7 months. In particular, ceramics containing alpha-tricalcium phosphate evoked bone formation in the pores of the ceramics. The amount of bone was similar at the different time periods.

Animals↗
PubMed1994

Calcium uptake and gp80 messenger RNA destabilization follows cAMP receptor down regulation in Dictyostelium discoideum.

The mechanism by which high concentrations of cAMP selectively destabilize the gp80 mRNA in Dictyostelium discoideum was investigated. This treatment which leads to down-regulation of the cAMP receptor was also found to cause an increase in calcium uptake. Given this observation, we sought a role for calcium as a second messenger in the degradation of the gp80 mRNA. Changes in the mRNA levels were examined after treating cells with compounds known to alter their intracellular Ca2+ concentrations. This included the use of A23187, Ca2+, 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate HC1 (TMB-8), LiCl and 8-p-chlorophenylthioadenosine 3',5'-cyclic monophosphate (ClPhS-Ado-3':5'-P). The sum of the data suggest that it is the cAMP-induced influx of Ca2+ across the plasma membrane, as apposed to a cAMP-mediated release of Ca2+ from intracellular stores, that initiates gp80 mRNA degradation. Treatment of cells with Concanavalin A (ConA) to induce cAMP receptor down-regulation, also causes a reduction in gp80 mRNA levels and an increase in calcium uptake.

Animals↗
PubMed1994

Partial albinism with immunodeficiency (Griscelli syndrome).

Partial albinism with immunodeficiency is a rare and fatal immunologic disorder characterized by pigmentary dilution and variable cellular immunodeficiency. To define the phenotype, therapy, and outcome, we retrospectively analyzed seven consecutive patients. Primary abnormalities included a silvery-grayish sheen to the hair, large pigment agglomerations in hair shafts, and an abundance of mature melanosomes in melanocytes, with reduced pigmentation of adjacent keratinocytes. Clinical onset occurred between the ages of 4 months and 4 years and was characterized by accelerated phases (lymphohistiocytic infiltration of multiple organs, including the brain and the meninges), triggered by viral and bacterial infections. Characteristic laboratory features included pancytopenia, hypofibrinogenemia, hypertriglyceridemia, and hypoproteinemia. Consistent immunologic abnormalities were characterized by absent delayed-type cutaneous hypersensitivity and impaired natural killer cell function. Some patients had secondary hypogammaglobulinemia, impaired major histocompatibility complex-mediated cytotoxic effects, a decreased capacity of lymphocytes to trigger a mixed lymphocyte reaction, or various functional granulocytic abnormalities. The disease seems to be invariably lethal without bone marrow transplantation; the mean age at the time of death was 5 years. Bone marrow transplantation has been performed in three cases; two patients died in the immediate posttransplantation period of infectious complications, but one patient is cured after a follow-up of 5 years. We conclude that partial albinism with immunodeficiency (Griscelli syndrome) can be differentiated from Chédiak-Higashi syndrome by pathognomonic histologic features. One of the underlying immunologic defects may be a defective function of natural killer cells, predisposing the patient to virus-associated hemophagocytic syndrome or accelerated phases. The prognosis is very poor unless early bone marrow transplantation is carried out.

Adrenal Cortex Hormones↗
PubMed1994

Scalp distribution of slow cortical potentials in schizophrenic patients.

Surface-negative slow cortical potentials (SPs) indicate increased excitability of the underlying cortical networks. Deviant patterns of SPs in schizophrenic patients may reveal in atypical regulation of cortical excitability. This hypothesis was examined by comparing SP-scalp distribution between patients with a chronic schizophrenic disorder and matched control Ss using reaction time paradigms. In study I (12 Ss/group) a CNV was evoked during a 3-s visual S1, while the parallel presentation of clicks at various time intervals should "probe" the brain state during the CNV. The CNV showed a frontal predominance in patients compared to a centroparietal maximum in controls, suggesting an atypical spatio-temporal regulation of SPs in patients. Similar modulation of probe-evoked responses parallel to the CNV in both groups indicated the functional significance of SPs to be similar in schizophrenics and controls. In study II (17 Ss/group) association between a visual S1 and a lateralised tactile S2 allowed fast responses with the respective hand. This association could be formed in one trial series, while the side of tactile stimulation was unpredictable in another. Feedback of response adequacy was provided 1.5 s after S2. Groupds did not differ in mean CNV-amplitudes or -lateralisation. On the other hand, patients developed a pronounced, broadly distributed feedback-preceding negativity (FNP) on all trials, while controls exhibited a right-hemisperic FPN only, when the side of S2 was unpredictable and feedback became salient.

Adult↗
PubMed1994

Growth phase-dependent regulation and membrane localization of SpaB, a protein involved in biosynthesis of the lantibiotic subtilin.

The information responsible for biosynthesis of the lantibiotic subtilin is organized in an operon-like structure that starts with the spaB gene. The spaB gene encodes an open reading frame consisting of 1,030 amino acid residues, and it was calculated that a protein having a theoretical molecular mass of 120.5 kDa could be produced from this gene. This is consistent with the apparent molecular weight for SpaB of 115,000 which was estimated after sodium dodecyl sulfate-gel electrophoresis and identification with SpaB-specific antibodies. The SpaB protein is very similar to proteins EpiB and NisB, which were identified previously as being involved in epidermin and nisin biosynthesis. Upstream from SpaB a characteristic sigma A promoter sequence was identified. An immunoblot analysis revealed that SpaB expression was strongly regulated. No SpaB protein was detected in the early logarithmic growth phase, and maximum SpaB expression was observed in the early stationary growth phase. The expression of SpaB was strongly correlated with subtilin biosynthesis. Deletion mutations in either of two recently identified regulatory genes, spaR and spaK, which act as a "two-component" regulatory system necessary for growth phase-dependent induction of subtilin biosynthesis (C. Klein, C. Kaletta, and K. D. Entian, Appl. Environ. Microbiol. 59:296-303, 1993), also resulted in failure of SpaB expression. To investigate the intracellular localization of SpaB, vesicles of Bacillus subtilis were prepared. The SpaB protein cosedimented with the vesicle fraction and was released only after vigorous resuspension of the vesicles. Our results suggest that SpaB is membrane associated and that subtilin biosynthesis occurs at the cytoplasmic membrane of B. subtilis.

Amino Acid Sequence↗
PubMed1994

Genes involved in self-protection against the lantibiotic subtilin produced by Bacillus subtilis ATCC 6633.

Subtilin is a ribosomally synthesized peptide antibiotic produced by Bacillus subtilis ATCC 6633. Recently, we reported regarding genes spaB, spaT, and spaC (C. Klein, C. Kaletta, N. Schnell, and K.-D. Entian, Appl. Environ. Microbiol. 58:132-142, 1992) which are involved in the biosynthesis of subtilin, and genes spaR and spaK (C. Klein, C. Kaletta, and K.-D. Entian, Appl. Environ. Microbiol. 59:296-303, 1993), which regulate subtilin biosynthesis via a histidine kinase/response regulator system. Further sequence analysis revealed the presence of three additional open reading frames, spaI, spaF, and spaG, downstream of the structural gene spaS. The spaI gene encodes a hydrophilic 19.3-kDa lipoprotein containing a consensus signal sequence, indicating that this protein might be membrane anchored. A similar gene, nisI, has been identified in the nisin producer. SpaF shows strong homology to members of the family of ABC transporters. spaG encodes a hydrophobic protein which might form the active transporter together with SpaF. Gene disruption mutants in all three genes were still able to produce subtilin; however, these mutants were more sensitive to subtilin than the wild-type strain. These results show that these genes are involved in the immunity mechanism of the producer strain. A similar involvement of an ABC transporter in the self-protection mechanism has been described for the McbE and McbF transporter, which confers immunity against microcin B17 in Escherichia coli. Mutants containing mutations in the genes spaR and spaK, which are responsible for regulation of subtilin biosynthesis, also became more sensitive to subtilin.(ABSTRACT TRUNCATED AT 250 WORDS)

ATP-Binding Cassette Transporters↗
PubMed1994

Loss of thrombospondin transcriptional activity in nickel-transformed cells.

mRNA from normal Chinese hamster embryo (CHE) cells was transcribed to cDNA and subtracted with an excess of mRNA from Chinese hamster embryo cells transformed by nickel compounds. Here we report the recovery of a sequence found to be highly homologous to the mouse thrombospondin 1 gene that was obtained by this subtraction procedure. Since thrombospondin is antiangiogenic, cancer cells expressing high levels of thrombospondin cannot grow in vivo because capillaries will not proliferate to cells secreting thrombospondin. To examine expression of thrombospondin, normal CHE cells were stained with monoclonal antibodies to human thrombospondin. The protein was present abundantly in the cytoplasm of normal cells but at greatly reduced levels in Ni-transformed cells. Analysis of mRNA by Northern (RNA) blot revealed transcripts in normal cells but little thrombospondin mRNA in Ni-transformed cells. Loss of thrombospondin mRNA expression was related to Ni treatment rather than transformation, since Ni-resistant cells also exhibited fewer thrombospondin transcripts than did wild-type cells. Digestion of genomic DNA with various combinations of restriction enzymes revealed thrombospondin gene patterns that were identical in both cell types, suggesting that there were no major deletions or rearrangements of the gene in the nickel-transformed cells. The inactivation of the thrombospondin gene was further investigated by analyzing the promoter activity of this gene linked to a chloramphenicol acetyltransferase (CAT) reporter plasmid that was transfected into normal and Ni-transformed cells. The CAT activity in normal cells was significantly higher than in Ni-transformed cells, suggesting that the promoter region of thrombospondin was less efficiently transcribed in Ni-transformed cells. We studied the consequences of enhanced expression of the retinoblastoma (Rb) gene, a known tumor suppressor gene, on CAT transcription driven by the human thrombospondin promoter. Cotransfection of an expression vector containing the mouse Rb gene greatly enhanced the transcription from the thrombospondin promoter such that the expression was higher in normal cells than in transformed cells.

Amino Acid Sequence↗
PubMed1994

Protein kinase A mediates growth-regulated expression of yeast ribosomal protein genes by modulating RAP1 transcriptional activity.

Yeast ribosomal protein genes are coordinately regulated as a function of cell growth; RNA levels decrease during amino acid starvation but increase following a carbon source upshift. Binding sites for RAP1, a multifunctional transcription factor, are present in nearly all ribosomal protein genes and are associated with growth rate regulation. We show that ribosomal protein mRNA levels are increased twofold in strains that have constitutively high levels of cyclic AMP-dependent protein kinase (protein kinase A [PKA]) activity. The PKA-dependent induction requires RAP1 binding sites, and it reflects increased transcriptional activation by RAP1. Growth-regulated transcription of ribosomal protein genes strongly depends on the ability to regulate PKA activity. Cells with constitutively high PKA levels do not show the transcriptional decrease in response to amino acid starvation. Conversely, in cells with constitutively low PKA activity, ribosomal protein mRNAs levels are lower and largely uninducible upon carbon source upshift. We suggest that modulation of RAP1 transcriptional activity by PKA accounts for growth-regulated expression of ribosomal protein genes.

Amino Acid Sequence↗
PubMed1994

[Video technology and the personal computer in the therapy simulator].

PURPOSE: Technical progress in the development of radiation therapy simulators provided valuable addition of electronically stored images and monitor indicators for individual radiation parameters. One can store as well as print these data as a treatment plan. The possibility of supplementing older simulators with these technical options will be reported in the following paper. METHODS: The modification of our simulator installation was done simply. The new equipment needed to expand our simulator facility was almost exclusively derived from the fields of entertainment and home electronics (Visualizer/video camera, video tape recorder, video mixer, additional monitor; personal computer and printer). RESULTS: With these modifications we reached the technical standards of the latest simulator generation. In addition, we succeeded in implementing additional technical options: e.g. image inversion with contrast alignment to diagnostic displays, complete magnetic tape recording of the entire x-ray process with possible repetition, electronic overlapping of the simulator image and the diagnostic image (e.g. NMR; angiograms) to determine the treatment volume, automation in x-ray documentation. CONCLUSION: Increased precision and rational work steps employing readily available equipment will lead to further improvement in the quality of radiotherapy.

Computer Systems↗
PubMed1994

[Iatrogenic stenoses of the respiratory tract. Evolution of therapeutic indications. Based on 217 surgical cases].

The authors report a series of 217 non-neoplastic stenoses of the upper airways operated in the period 1978-1991. One hundred and twenty patients with tracheal stenoses underwent tracheal resection and end-to-end anastomosis, with 117 excellent results and 3 deaths. The treatment of 97 patients with laryngotracheal stenoses was much more complex and difficult to manage: Fifty-nine underwent tracheal and subglottic resection-anastomosis with 58 successes and 1 death--Seven had resection-anastomosis with total cricoidectomy and stenting. They were 6 successes and 1 death--Three had supraglottic resection-anastomosis with 3 successes--Twelve underwent laryngeal enlargement over a T-tube with successes in 11 cases and failure in 1 case. Sixteen had complex combinations of resection and modeling with 13 successes, 2 failures, and 1 death. In this series under the same therapeutic options, the results were successful in 96% of cases, with 4% of failures (7% of them resulting in death). The anatomical type, tracheal or laryngotracheal, length of the stenosis, neuropsychological sequelae, and overall poor respiratory status of the patients must be taken into account before deciding the therapeutic strategy. Old age is not a contraindication to tracheal resection, but is certainly a risk factor for morbidity and mortality. The key to success is undoubtedly careful preoperative preparation, treatment of local infection and inflammation, as well as meticulous mucomucosal approximation of healthy margins at the anastomosis.

Adolescent↗
PubMed1994

Biogenesis of gp80, the GPI-anchored cohesion protein in D. discoideum.

We have begun to assess the contributions made by co- and post-translational modifications to the physical properties of the D. discoideum protein gp80, and its sensitivity to hydrolysis by an endogenous GPI-PLC like activity. Two-dimensional gel electrophoresis indicates that the presence of various gp80 isoforms reflects the differential processing of its N-linked oligosaccharides. The presence or absence of this modification does not, however, appear to alter the sensitivity of the protein to the endogenous GPI-PIPLC activity. gp80 synthesized in cells defective in O-glycosylation is found predominantly in the medium as proteolytic products. The relationship of the O-linked modifications to the endogenous GPI-PIPLC activity is not yet clear. However, their absence does not alter the sensitivity of gp80 to exogenous GPI-PIPLC. We attempted to inhibit the GPI anchoring of gp80 using mannoseamine. Although cells displayed a reversible block in the onset of aggregation and gp80 synthesis, this did not appear to reflect changes in anchoring. The contribution is now being examined in chimeric proteins.

Animals↗
PubMed1994

Constitutive overexpression of a GPI-anchored cell adhesion molecule in Dictyostelium discoideum cells.

gp80 is the best characterized cell adhesion molecule of Dictyostelium discoideum. It has a glycolipid anchor that, although it shows resistance to exogenous GPI-PLC, is sensitive to an endogenous hydrolyzing activity. Preliminary data suggest that acylation on the inositol ring is not the basis for this resistance. In order to investigate the features of glycolipid anchoring during Dictyostelium development we have obtained stable transformants that overexpress gp80 during its whole life cycle.

Animals↗
PubMed1994

[Ilizarov bone lengthening for treatment of mandibular micrognathism in childhood].

Uni- or bilateral mandibular micrognathia could be congenital or acquired. In case of missing early correction of the lower jaw the midface will become malformed adaptively. Previous therapeutic strategies based on orthodontic measures and/or the use of costochondral grafts. However, especially the surgical treatment is often impossible in little children. In this report three cases of mandibular bone lengthening are presented. This less invasive but most effective surgical technique, which bases on Ilizarov's method originally, is an encouraging alternative procedure.

Adolescent↗