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Biomedical subjects

S Kern

Publications and source records attributed to S Kern.

At least 37 records · Page 2Linked to original sources
PubMed2000

Tissue specificity of glucocorticoid sensitivity in healthy adults.

Contradicting data exist as to whether interindividual patterns in glucocorticoid (GC) sensitivity vary between different target tissues in humans. This study therefore measured GC sensitivity in 36 healthy subjects in three target tissues: the immune system; the cardiovascular system, and the hypothalamus-pituitary-adrenal axis. For this purpose, dexamethasone inhibition of lipopolysaccharide-induced interleukin-6 and tumor necrosis factor-alpha production in peripheral leukocytes, beclomethasone dipropionate-induced skin blanching, and suppression of cortisol levels after low-dose (0.5 mg) dexamethasone suppression test were determined in each subject. The results showed the expected glucocorticoid-induced suppression of interleukin-6 and tumor necrosis factor-alpha production (both P < 0.001), dose-dependent skin blanching (P < 0.001), and suppression of salivary cortisol response to awakening (P < 0.001). However, neither simple correlations nor cluster analysis revealed a significant association among the three bioassays for GC sensitivity. In contrast to the idea that interindividual variation in GC sensitivity is an intrinsic trait affecting all tissues, these results suggest that this variability is target tissue specific in healthy subjects.

Adult↗
PubMed1999

Rapid detection of epidemic strains of methicillin-resistant Staphylococcus aureus.

Fifty methicillin-resistant Staphylococcus aureus (MRSA) initial isolates obtained from patients hospitalized in the orthopedic clinic of the Frankfurt University Hospital and 150 methicillin-sensitive Staphylococcus aureus (MSSA) isolates were investigated in this study to determine whether the Slidex Staph-Kit is capable of differentiating between MRSA and MSSA owing to its unique performance characteristics. The Slidex Staph-Kit is a combined latex hemagglutination test designed to detect clumping factor, protein A, and a specific surface immunogen for S. aureus. Clumping factor-positive strains cause erythrocytes sensitized with fibrinogen to hemagglutinate, thereby resulting in visible red clumps. S. aureus strains deficient in clumping factor agglutinate latex particles sensitized with specific antibodies against surface proteins of S. aureus, thereby resulting in visible white clumps. Our results demonstrate that white clumping has a 99% specificity as well as a 98% positive predictive value for MRSA. Clumping factor-negative MRSA, which have been reported to occur in several countries, are epidemic in the Frankfurt area and account for 80% of all MRSA initial isolates in the orthopedic clinic of the Frankfurt University Hospital. Genotyping of all MRSA isolates by macrorestriction analysis of chromosomal DNA revealed that 83% of clumping factor-negative MRSA are closely related to the "southern-German" epidemic strain. This is the first study demonstrating the Slidex Staph-Kit's capability for identifying epidemic clumping factor-negative S. aureus strains as methicillin resistant even prior to antimicrobial susceptibility testing.

Agglutination Tests↗
PubMed1999

Rare-MR-urography--a new diagnostic method in autosomal recessive polycystic kidney disease.

PURPOSE: To describe the appearance of autosomal recessive polycystic kidney disease (ARPKD) by using a new diagnostic method: RARE-MR-urography. MATERIAL AND METHODS: Eight children were evaluated using MR images from 0.23 T and 1.5 T MR units, using T1-weighted spin-echo and T2-weighted turbo spin-echo sequences and RARE-MR-urography. Signal intensities, morphological appearance of the affected kidneys and, specifically, the picture of the urinary tract in RARE-MR-urography, were evaluated. RESULTS: All children showed enlargement, reniform but humpy kidney shape, homogeneous-grainy renal parenchyma, normal renal pelvis and calyces. Although ARPKD is always associated with some degree of congenital hepatic fibrosis, there was no bile duct dilatation or liver fibrosis at the time of examination. Signal intensity was hyperintense in T2-weighted images in all cases. In 5 cases, T1-weighted images were hypointense. In RARE-MR-urography, hyperintense, linear, radial patterns in cortex and medulla were seen, which represent microcystic dilatation of collecting ducts and are therefore characteristic of ARPKD. Four patients presented with a few circumscribed small subcapsular cysts. CONCLUSION: RARE-MR-urography is a noninvasive method which demonstrates the pathognomonic water-filled cystic structures throughout the kindeys in ARPKD.

Adolescent↗
PubMed1998

Relative clauses in French children's narrative texts.

This study investigates the use of relative clauses in French children's narrative monologues. Narrative texts were collected from French-speaking monolinguals in four age groups (five, seven, ten years and adults). Twenty subjects from each group were asked to tell a story based on a picture book consisting of twenty-four images without text (Frog, Where are you?). Relative constructions were coded following the categories defined by Dasinger & Toupin (1994) into two main functional classes: general discourse and narrative functions. The results show that the use of relative clauses in general discourse functions precedes their use in more specific narrative functions. An analysis of textual connectivity (Berman & Slobin, 1994) in one episode reveals that children and adults differ in their choice of preferred structures. The results also show that children use fewer transitive predicates in relative clauses than do adults. Transitive verbs are essential for advancing the narrative plot (Hopper & Thompson, 1980). While subject relative clauses are acquired early and used frequently, the development of their multifunctional use in diverse narrative functions extends well beyond childhood.

Adult↗
PubMed1998

Does anti-atherogenic estradiol valerate treatment cause adverse effects on liver and uterus in NZW rabbits?

The rabbit has been a widely accepted animal model for atherosclerosis research since Anitschkow first used this animal in 1913 in identifying dietary-induced hypercholesterolemia as a major risk factor for atherogenesis. Experiments with cholesterol-fed rabbits have demonstrated the beneficial effects of estrogen treatment on the development of atheroma for more than 50 y. Clinical trials have found a reduction in cardiovascular events of up to 50% in postmenopausal women receiving estrogen replacement therapy. However, metabolic conditions in rabbits, as well as physiological estrogen serum levels, differ in some aspects from those in humans. In rabbits, experimentally-induced hormone levels are about 5- to 10-fold higher than those found in untreated animals. Normal physiological estrogen levels in rabbits are not cardioprotective under dietary-induced hypercholesterolemia. We investigated whether replacement induced "hyperestrogenemia" causes adverse effects on organs other than the cardiovascular system. Twenty-nine female rabbits were divided into 4 different groups, 2 without and 2 with estrogen treatment (1 mg estradiol valerate/kg body weight/w over 12 w). Organ weights, transaminases and uterine histology were examined. In rabbits treated with estrogen, we did not see relevant adverse effects on heart, kidney and liver weights, or on liver enzymes. But there was a significant increase in spleen weights, as well as notable changes in the endometrium with moderate inflammation. These findings indicate that the dosage of estrogen commonly used for atherosclerosis research does not cause serious disorders in the major organs of cholesterol-fed rabbits.

Animals↗
PubMed1998

Two active copies of the X-linked gene spermidine/spermine N1-acetyltransferase (SSAT) in a female lung cancer cell line are associated with an increase in sensitivity to an antitumor polyamine analogue.

The expression of the polyamine catabolic enzyme, spermidine/spermine N1-acetyltransferase (SSAT), has been associated with tumor sensitivity to antitumor polyamine analogues. In the sensitive cell types the level of SSAT is greatly induced by these agents. Although SSAT expression is regulated at many levels, the initial regulation of this X-linked gene occurs at the level of transcription. Because most previous work in human cell lines has been performed in cells of male origin and because the SSAT gene is located near the pseudoautosomal region of the X chromosome, we investigated the possibility that both copies of SSAT could be expressed in normal and tumor cells in women. DNA methyl-sensitive restriction enzyme analysis of DNA from normal peripheral lymphocytes suggested that like most X-linked genes, only one copy of SSAT is actively transcribed. However, in an examination of four representative human lung tumor cell lines derived from women, two were found to have a methylation pattern identical to male-derived cells, suggesting a reactivation of the normally inactive allele or loss of the inactive allele. Microsatellite repeat polymorphism analysis indicated that one of the lines, a female carcinoid line, NCI H727, had reactivated the previously inactive copy, thus providing H727 with two active alleles, whereas a small cell lung cancer line, H889, appears to have lost the inactive allele. Most importantly, the H727 line expressed high amounts of SSAT mRNA and protein in response to treatment with the polyamine analogue, N1,N12-bis(ethyl)spermine, a compound known to increase SSAT transcription in sensitive cell types. H727 was also the only female line that responded to treatment in a cytotoxic manner. These data suggest that both copies of the SSAT allele may be expressed and that the inappropriate expression of the second copy can lead to an increase in tumor sensitivity to polyamine analogues that induce SSAT.

Acetyltransferases↗
PubMed1997

High resolution analysis of chromosome 3p alterations in cervical carcinoma.

Although loss of heterozygosity (LOH) for loci on chromosome 3p is a common event in cervical carcinoma (CC), the frequency and affected regions of 3p are inconsistent among studies. Here we report a comprehensive analysis of LOH on 3p in 66 primary tumors and 16 CC-derived cell lines using a high density of marker loci. Clonal LOH was found in over 70% of primary tumors, and the patterns of loss indicated four to five target regions, with 3p14 being the most frequent. The majority of tumors had complex patterns of allelic imbalance, with regions of subclonal and clonal losses often present in individual tumors. We exploited marker homozygosity in CC-derived cell lines as an indirect measure of LOH and identified four homozygous deletions (HDs) during this analysis at loci located within the 3p14.2 region to which the FHIT gene has been mapped recently. This led to a careful reevaluation of the LOH patterns in primary CCs, which showed apparent retention of heterozygosity for loci in this region indicative of the presence of several additional HDs. To our knowledge, this is the first report of HDs encompassing the FHIT gene region in primary tumor samples and underscores the usefulness of high resolution genetic analysis of tumor genomes in determining the chromosomal aberrations underlying the malignant progression of CC.

Alleles↗
PubMed1997

Direct hybridization of large-insert genomic clones on high-density gridded cDNA filter arrays.

A major challenge to positional cloning approaches is the identification of coding sequences within a region of interest. Hybridization of genomic fragments that represent a cloned contig of a defined genomic region in appropriate cDNA libraries theoretically represents a direct solution to this problem. However, this is technically difficult and in general, success with this approach has been limited to the use of small fragments, such as those cloned in cosmids and phages. Since most physical maps are composed of genomic DNA cloned in vectors with significantly greater insert size capacity, there is a need to develop efficient methods to use these clones directly as hybridization probes. Here we describe a highly sensitive protocol for hybridization of P1-derived artificial chromosomes (PACs; average insert size, 120 kb) on a composite, normalized cDNA library comprised of 200000 clones spotted at high density on nylon filters. Because limited sequence information on more than 150000 of these clones is now available in the public domain, positive hybridization results can be rapidly converted to cDNA sequence information without recourse to any clone manipulation in the initial phases of a project. Using these protocols, we have been able to reproducibly detect coding exons that constitute as little as 0.2% of the total PAC insert.

Base Sequence↗
PubMed1996

Simultaneous assessment of loss of heterozygosity at multiple microsatellite loci using semi-automated fluorescence-based detection: subregional mapping of chromosome 4 in cervical carcinoma.

Detection of loss of heterozygosity (LOH) by comparison of normal and tumor genotypes using PCR-based microsatellite loci provides considerable advantages over traditional Southern blotting-based approaches. However, current methodologies are limited by several factors, including the numbers of loci that can be evaluated for LOH in a single experiment, the discrimination of true alleles versus "stutter bands," and the use of radionucleotides in detecting PCR products. Here we describe methods for high throughput simultaneous assessment of LOH at multiple loci in human tumors; these methods rely on the detection of amplified microsatellite loci by fluorescence-based DNA sequencing technology. Data generated by this approach are processed by several computer software programs that enable the automated linear quantitation and calculation of allelic ratios, allowing rapid ascertainment of LOH. As a test of this approach, genotypes at a series of loci on chromosome 4 were determined for 58 carcinomas of the uterine cervix. The results underscore the efficacy, sensitivity, and remarkable reproducibility of this approach to LOH detection and provide subchromosomal localization of two regions of chromosome 4 commonly altered in cervical tumors.

Chromosome Deletion↗
PubMed1996

Analysis of replication error (RER+) phenotypes in cervical carcinoma.

Infection of epithelial cells with human papillomavirus is an important early event in the development of cervical dysplasia. However, progression to overt malignancy appears dependent upon further genetic and/or epigenetic events. We have recently developed methodologies for the simultaneous analysis of loss of heterozygosity (LOH) at multiple PCR-based microsatellite loci using semiautomated fluorescent DNA sequencing technology to determine the locations of tumor suppressor genes which are inactivated during tumor progression. While examining 30 microsatellite loci for LOH on chromosomes 3p, 4, and 11q, we detected novel tumor-specific alleles indicative of microsatellite instability (MI). The methodology allowed rapid and accurate comparison of over 3000 genotypes from 89 primary tumors and 10 cervical carcinoma-derived cell lines and showed that five tumors (5.6%) and one human papillomavirus-negative cell line, C33A, had genetic features consistent with a replication error (RER+) phenotype as defined by MI at two or more loci. In each of the RER+ tumors, LOH was also observed at one or more loci on each of the three chromosomes examined. These findings suggest that defects in DNA repair-associated genes are rarely acquired and do not supersede allelic loss during cervical carcinogenesis. In addition, the semiautomated multiplex approach has proven unequivocal in the detection and interpretation of MI and should greatly accelerate the rapidity and accuracy of analysis of such defects in tumors. Moreover, the number of loci that can be relatively easily examined in this way will also allow a detailed statistical consideration of the importance of such events.

Chromosomes, Human, Pair 11↗
PubMed1995

Indomethacin blocks the immunosuppressive activity of rat testicular macrophages cultured in vitro.

Macrophages are a prominent resident cell type in the interstitial tissue of the testis in several mammalian species. This presence in an immunologically-privileged site prompted an investigation of their ability to initiate and regulate lymphocyte proliferation in vitro. Isolated rat peripheral blood lymphocytes (PBL) were cultured either directly with isolated rat testicular (Tm) or peritoneal (Pm) macrophages or with the conditioned medium from cultures of these cells (Ts or Ps). The presence of Tm and Ts reduced the proliferative response of PBL to 65% +/- 3% and 65% +/- 4% of that observed in the control cultures. Stimulation of the Tm with lipopolysaccharide (LPS) did not significantly alter this effect. Dialysis of Ts (to remove molecules < 14,000 MW) before addition to PBL cultures did significantly reduce the amount of inhibition, with PBL proliferation reaching 93% +/- 4% of the control. LPS in conjunction with indomethacin (IDM) or interferon gamma (IFN gamma) induced PBL proliferation at levels comparable to or significantly greater than those of the controls (104% +/- 4% and 113% +/- 6%, respectively). The collective addition of IDM, IFN gamma and LPS to Tm cultures increased PBL proliferation over control levels (119% +/- 5% for Ts and 133% +/- 6% for Tm). Prostaglandin levels in macrophage-conditioned medium were measured by specific radioimmunoassay and were significantly greater in Ts (13.1 +/- 0.4 ng/ml PGE2 and 16.8 +/- 0.6 ng/ml PGF2 alpha) than in Ps (both below the assay minimum sensitivities). The results indicate that the rat testicular macrophages produce high basal levels of prostaglandin E2 and F2 alpha. These products appear largely responsible for the inhibition by these cells of mitogen-induced PBL proliferation in vitro, and may contribute to both the immune-privileged status and the normal physiology of the rodent testis.

Animals↗
PubMed1995

Cytokine secretion by macrophages in the rat testis.

The rat testis contains a large population of resident macrophages, the physiological roles of which are yet to be established. To investigate the functional capacity of these cells, we have analyzed the secretion of the cytokines interleukin (IL)-1, IL-6, tumor necrosis factor alpha (TNF alpha), and granulocyte macrophage-colony stimulating factor (GM-CSF) by isolated testicular macrophages (TMs) and, for comparison, by isolated rat peritoneal macrophages (PMs). Cells were cultured for 48 h in serum-free medium alone or with lipopolysaccharide (LPS, 10 micrograms/ml) and/or recombinant interferon-gamma (rIFN gamma, 200 U/ml). Specific bioassays were used to measure cytokines in the media collected from cultures. Basal production of IL-1, TNF alpha, and IL-6 by TMs and PMs were similar, but TMs produced 8-fold greater levels of GM-CSF than did PMs. LPS, alone or in combination with IFN gamma, significantly enhanced the secretion of all cytokines by PMs (340-840% increase). LPS alone had little effect on TM secretion except to reduce GM-CSF levels some 4-fold. The addition of LPS and IFN gamma increased IL-1, IL-6, and TNF alpha levels (200-750% increase) and reduced GM-CSF levels to 45% of basal levels. Treatment of cultures with indomethacin to minimize prostaglandin production enhanced the LPS-induced effects in both cell types. Expression of the mRNA for each cytokine in cultures of testicular and peritoneal macrophages, as well as in intact testis, was confirmed by reverse transcription polymerase chain reaction. These studies indicate that macrophages resident within the rat testis have a novel cytokine secretion profile and an altered responsiveness to inflammatory activators compared with macrophages from the peritoneal cavity. This may be important in physiological processes in the testis and may contribute to the dysfunctional afferent immune activity thought to underlie the immunologically privileged status of the testes.

Animals↗
PubMed1995

Investigating local regulation of the testes of ruminants.

In addition to endocrine regulation by the gonadotrophic hormones, the functions of the testes are regulated locally by paracrine and autocrine factors. Some attempts have been made to isolate cells from the testes of immature bulls and rams for investigation of cell function in vitro. However, most studies have used in vitro cultures of cells isolated from the testes of rats and a large variety of factors have been identified as potential local regulators. This review examines the importance of Sertoli cell-germ cell interactions, Leydig cells and steroidogenesis, blood flow and vascular permeability, and cytokines and immune cells as local regulators of the testes. The small amount of work undertaken on the testes of ruminants is reviewed together with approaches such as the transilluminated dissection of staged seminiferous tubules and in vivo cell depletion models used with rats. The suitability and limitation of these approaches for ruminants are considered, and immunological and molecular probes are raised as options for future investigations of the local regulation of the testes of ruminants.

Androgens↗
PubMed1993

Influence of S9 mix composition on the SOS response in Escherichia coli PQ37 by polycyclic aromatic hydrocarbons.

To investigate the variability in test results obtained with the SOS chromotest (Escherichia coli PQ37 genotoxicity assay) when varying the composition of the exogenous metabolizing system (S9 mix), we examined the influence of different S9 and NADP concentrations, of buffer pH value, of SDS concentrations, the effects of E. coli PQ37 density and centrifugation steps on the expression of beta-galactosidase (beta g) and alkaline phosphatase (ap) activity, the calculated induction factors (IFs) and SOS-inducing potencies (SOSIPs). Additionally we examined the metabolic potency (stability) of S9 mix when stored at 37 degrees C before use. Initially, we used 0-5000 ng (= 0-20 nmole) benzo[a]pyrene (B[a]P) as a reference compound for the test procedure in the presence of standard S9 mix. Subsequently, to evaluate the results of S9 mix variations we examined several polycyclic aromatic hydrocarbons (PAHs) using both the standard and a modified S9 mix composition and test protocol. We observed the highest beta g and ap activities and/or IFs using only 11-27 microliters 9000 x g liver supernatant (S9) from Aroclor 1254-induced rats per assay (20-50% of standard amount) and calibrating the S9 mix Tris buffer to pH 7.8-8.0. 60-300 micrograms NADP/assay (10-50% of standard) was sufficient for optimum activation of PAHs. In contrast to previous investigations about the variability of the SOS chromotest in the absence of a metabolizing system, higher induction factors were obtained when using higher bacterial densities (12-18 x 10(6) cfu/assay). Centrifugation steps as recommended by other investigators were not necessary when using optimum S9 amounts. The metabolic activity of S9 mix remained nearly constant approximately 20 min after preparation, but decreased to 80% of its activity in about 1 h.

Animals↗
PubMed1993

The self-locking Balgrist hip socket for cementless fixation: biomechanical principles and clinical results.

The Balgrist hip socket, initially made entirely of HDPE (high molecular weight polyethylene), now made of outer titanium alloy shell that faces the bone of the acetabulum has been in clinical use for 10 years. The purpose of this presentation is to illustrate the biomechanical principles that have governed this unique design and to present the clinical results that we have obtained until the end of 1991 with 717 implants. From 1982 to 1987 Balgrist HDPE sockets had been implanted for 346 hips, from 1984 to 1991 Balgrist Titanium alloy sockets have been implanted for 371 hips. The number of revision are 55 of 717 hips. 48 hips out of 55 were with Balgrist HDPE sockets. On the contrary, only 7 hips were with Balgrist titanium socket. The greatest benefit of Balgrist Titanium socket is the excellent mechanical lock with subchondral bone of the acetabulum.

Biomechanical Phenomena↗