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Biomedical subjects

I Kern

Publications and source records attributed to I Kern.

At least 19 recordsLinked to original sources
PubMed2003

Recurrent de novo mitochondrial DNA mutations in respiratory chain deficiency.

Starting from a cohort of 50 NADH-oxidoreductase (complex I) deficient patients, we carried out the systematic sequence analysis of all mitochondrially encoded complex I subunits (ND1 to ND6 and ND4L) in affected tissues. This approach yielded the unexpectedly high rate of 20% mutation identification in our series. Recurrent heteroplasmic mutations included two hitherto unreported (T10158C and T14487C) and three previously reported mutations (T10191C, T12706C and A13514G) in children with Leigh or Leigh-like encephalopathy. The recurrent mutations consistently involved T-->C transitions (p<10(-4)). This study supports the view that an efficient molecular screening should be based on an accurate identification of respiratory chain enzyme deficiency.

Adolescent↗
PubMed2000

Wegener's granulomatosis in the upper respiratory tract.

Wegener's granulomatosis is a distinct clinico-pathological entity characterised by necrotising vasculitis of small arteries and veins in conjunction with the formation of granuloma in the upper and lower respiratory tracts, and glomerulonephritis. The vast majority of patients have antineutrophil cytoplasmic antibodies in the serum with a characteristic cytoplasmic pattern. However, in early phases of the disease only the upper respiratory tract may be affected, clinical and histological features may be nonspecific, and antineutrophil cytoplasmic antibodies not present. In this paper we present four patients with involvement of the upper respiratory tract suspicious for early Wegener's granulomatosis. We emphasise the significance of clinical, histological and serological parameters in the early detection of Wegener's granulomatosis.

Aged↗
PubMed2000

Familial t(6;21)(p21.1;p13) translocation associated with male-only sterility.

A 38-year-old male with primary infertility was referred for cytogenetic investigation. Karyotype analysis revealed a 46,XY,t(6;21)(p21.1;pl3) translocation. The Ag-nucleolar organizer regions (NORs) banding technique demonstrated that the 21p NORs were retained in the derivative and actively transcribed. Family studies showed that three brothers, two sisters and their mother carried the t(6;21). All carrier males suffered from primary infertility with severe oligoasthenoteratospermia or azoospermia, whereas at least two of the three carrier women were fertile. The region of the translocation breakpoint was narrowed down cytogenetically and by fluorescence in situ hybridisation as 21p13 and 6p21.1. Southern blot analysis showed that the gene ZNF165, which maps to this region and which is specifically expressed in the testis, was not disrupted by the translocation. However, studies performed on testicular biopsy showed spermatocyte meiosis anomalies. We discuss the possible mechanisms by which the translocation might affect meiosis in spermatogenesis and lead to infertility.

Adult↗
PubMed1999

Mutational analysis of the Streptococcus pneumoniae bimodular class A penicillin-binding proteins.

One group of penicillin target enzymes, the class A high-molecular-weight penicillin-binding proteins (PBPs), are bimodular enzymes. In addition to a central penicillin-binding-transpeptidase domain, they contain an N-terminal putative glycosyltransferase domain. Mutations in the genes for each of the three Streptococcus pneumoniae class A PBPs, PBP1a, PBP1b, and PBP2a, were isolated by insertion duplication mutagenesis within the glycosyltransferase domain, documenting that their function is not essential for cellular growth in the laboratory. PBP1b PBP2a and PBP1a PBP1b double mutants could also be isolated, and both showed defects in positioning of the septum. Attempts to obtain a PBP2a PBP1a double mutant failed. All mutants with a disrupted pbp2a gene showed higher sensitivity to moenomycin, an antibiotic known to inhibit PBP-associated glycosyltransferase activity, indicating that PBP2a is the primary target for glycosyltransferase inhibitors in S. pneumoniae.

Amino Acid Sequence↗
PubMed1998

Right hemisphere activation during indirect semantic priming: evidence from event-related potentials.

Healthy subjects performed a lexical decision task in a semantic priming paradigm while event-related potentials (ERPs) were recorded from 64 channels. Semantic distance between prime and target was varied by including directly, indirectly, and nonrelated word pairs. At centro-parietal electrodes an N400 to nonrelated pairs was elicited bilaterally which was sensitive only to direct, but not to indirect semantic priming. These N400 priming effects were mirrored by the RT data. At inferior fronto-temporal sites directly related words showed ERP priming effects over both hemispheres. However, indirectly related words only elicited ERP priming effects over the right hemisphere. These results support the hypothesis that the right hemisphere semantic system is involved in processing of remote semantic information.

Adult↗
PubMed1998

Acquisition of five high-Mr penicillin-binding protein variants during transfer of high-level beta-lactam resistance from Streptococcus mitis to Streptococcus pneumoniae.

Penicillin-resistant isolates of Streptococcus pneumoniae generally contain mosaic genes encoding the low-affinity penicillin-binding proteins (PBPs) PBP2x, PBP2b, and PBP1a. We now present evidence that PBP2a and PBP1b also appear to be low-affinity variants and are encoded by distinct alleles in beta-lactam-resistant transformants of S. pneumoniae obtained with chromosomal donor DNA from a Streptococcus mitis isolate. Different lineages of beta-lactam-resistant pneumococcal transformants were analyzed, and transformants with low-affinity variants of all high-molecular-mass PBPs, PBP2x, -2a, -2b, -1a, and -1b, were isolated. The MICs of benzyl-penicillin, oxacillin, and cefotaxime for these transformants were up to 40, 100, and 50 microg/ml, respectively, close to the MICs for the S. mitis donor strain. Recruitment of low-affinity PBPs was accompanied by a decrease in cross-linked muropeptides as revealed by high-performance liquid chromatography of muramidase-digested cell walls, but no qualitative changes in muropeptide chemistry were detected. The growth rates of all transformants were identical to that of the parental S. pneumoniae strain. The results stress the potential for the acquisition by S. pneumoniae of high-level beta-lactam resistance by interspecies gene transfer.

Amino Acid Sequence↗
PubMed1998

The effect of latent adenovirus 5 infection on cigarette smoke-induced lung inflammation.

The aim of this study was to test the hypothesis that latent adenovirus (Ad) 5 infection increases the lung inflammation that follows a single acute exposure to cigarette smoke. A recently developed model of latent adenoviral infection in guinea-pigs was used. Twelve animals were infected with Ad5 (10(8) plaque-forming units) and 12 animals were sham-infected. Thirty five days later six Ad5-infected and six sham-infected animals were exposed to the smoke from five cigarettes. The remaining animals were used as controls for both infection and smoking. As markers of inflammation, the volume fraction of macrophages, T-lymphocytes, neutrophils and eosinophils were measured by quantitative histology. We found that latent Ad5-infection alone, doubled the number of macrophages in the lung parenchyma and that smoking alone, doubled the volume fraction of neutrophils in the airway wall and the volume fraction of macrophages in the lung parenchyma. Neither viral infection nor smoking, alone, had an effect on T-lymphocytes or eosinophils. However, the combination of viral infection and smoking doubled the T-lymphocyte helper cells and quadrupled the volume fraction of macrophages in the lung parenchyma. We conclude that in guinea-pigs, latent adenovirus 5 infection increases the inflammation that follows a single acute exposure to cigarette smoke, by increasing the volume fraction of macrophages and T-lymphocyte helper cells.

Adenoviridae Infections↗
PubMed1995

A novel antigen-processing-defective phenotype in major histocompatibility complex class II-positive CIITA transfectants is corrected by interferon-gamma.

Presentation of exogenous protein antigens to T lymphocytes is based on the intersection of two complex pathways: (a) synthesis, assembly, and transport of major histocompatibility complex (MHC) class II-invariant chain complexes from the endoplasmic reticulum to a specialized endosomal compartment, and (b) endocytosis, denaturation, and proteolysis of antigens followed by loading of antigenic peptides onto newly synthesized MHC class II molecules. It is believed that expression of MHC class II heterodimers, invariant chain and human leukocyte antigen-DM is both necessary and sufficient to reconstitute a functional MHC class II loading compartment in antigen-presenting cells. Expression of each of these essential molecules is under the control of the MHC class II transactivator CIITA. Unexpectedly, however, whereas interferon gamma stimulation does confer effective antigen-processing function to nonprofessional antigen presenting cells, such as melanoma cells, expression of the CIITA transactivator alone is not sufficient. Activation of antigen-specific T cells thus requires additional CIITA-independent factor(s), and such factor(s) can be induced by interferon gamma.

Antigen-Presenting Cells↗
PubMed1995

Secretion of streptokinase fusion proteins from Escherichia coli cells through the hemolysin transporter.

The hemolysin (HlyA) secretion system was used to achieve the sec-independent secretion of streptokinase (Skc) originating from Streptococcus equisimilis into the medium by Escherichia coli cells. The in-frame fusions of the skc gene, either possessing or lacking a region encoding the signal peptide (SP) with the 3'-end of the hlyA gene of various lengths were analysed. All hybrids retained Skc activity. Hybrid proteins devoided of the N-terminal SP, regardless of length of the hlyA secretion signal (62 vs. 194 amino acids), were secreted into the medium by the E. coli HlyA transporter at similar levels. Considerable amounts of hybrid proteins were still, however, associated with E. coli cells, mainly in the degraded form.

Bacterial Proteins↗
PubMed1995

The two novel MHC class II transactivators RFX5 and CIITA both control expression of HLA-DM genes.

MHC-encoded HLA-DMA and -DMB molecules are atypical MHC chains that play an essential role in antigen presentation by MHC class II molecules. They resemble both MHC class I and II molecules but are not expressed at the cell surface. From the study of MHC class II regulatory mutants, it was found recently that two novel transactivators, CIITA and RFX5, are essential for the control of MHC class II gene expression. We report here that CIITA and RFX5, although operating at different levels of transcriptional control, are also both essential regulators of HLA-DMA and -DMB genes. This is true for both the constitutive and the inducible mode of DM gene expression. Indeed, both CIITA and RFX5 cDNA can correct the HLA-DMA and -DMB gene expression defect in the respective regulatory mutants. The involvement of these two transcription factors accounts for the coordinate expression of MHC class II and HLA-DM, two sets of molecules that perform quite different functions in the overall process of antigen presentation.

Cell Line↗
PubMed1993

Laparoscopy for the non-palpable testis: a review of twenty-eight patients (1988-90).

The applications of laparoscopy as a diagnostic and therapeutic tool are being continually expanded and applied to the younger patient. In this study, 28 boys with 32 non-palpable testes underwent laparoscopy as part of their management. The patients' ages ranged from 10 months to 13 years. There was one failed laparoscopy and one minor complication. Blind ending vas deferens and vessels proximal to the deep inguinal ring were noted in six patients and no viable testes were found in these boys. Five abdominal testes were noted; three underwent scrotal fixation, one was excised after failed Fowler-Stephens orchidopexy and one had a staged procedure. Twenty-one non-palpable testes were noted on laparoscopy to have the vas deferens and vessels entering the inguinal canal; of these, 12 were atrophic on inguinal exploration. The remaining nine testes were successfully fixed in the scrotum. This study concludes that laparoscopy is a safe and effective part of the management of the non-palpable testis. The advantages of laparoscopy in the localization of the testis and its potential uses in treatment are highlighted.

Child↗
PubMed1991

Tongue tie.

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Child↗
PubMed1987

Microheterogeneity in Aspergillus nidulans 5S rRNA genes.

We have determined the sequence of 4 Aspergillus nidulans 5S rRNA genes and compared it with 4 previously established sequences. No extensive homologies are found in 5' flanking sequences, but in the 3' flanks of two genes and two pseudogenes similar sequences are observed. In the coding sequences differences occur in 7 positions. Two 5S rRNA genes which are found in one plasmid 1.1 kb apart are located in opposite orientations.

Aspergillus nidulans↗