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Biomedical subjects

B Köhler

Publications and source records attributed to B Köhler.

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

The delivery of salts to the xylem. Three types of anion conductance in the plasmalemma of the xylem parenchyma of roots of barley.

To explore possible pathways for anions to enter the xylem in the root during the transport of salts to the shoot, we used the patch-clamp method on protoplasts prepared from the xylem parenchyma of barley (Hordeum vulgare L.) plants. K(+) currents were suppressed by tetraethylammonium or N-methylglucamine in the solutions in the pipette and the bath, and the permeating anions were Cl(-) or NO(3)(-). We recorded the activities of three distinct anion conductances: (a) an inwardly rectifying anion channel (X-IRAC), characterized by activation at hyperpolarization and open times of up to several seconds; (b) a quickly activating anion conductance (X-QUAC), important for anion efflux at voltages between -50 mV and the equilibrium potential of the prevailing anion; and (c) a slowly activating anion conductance (X-SLAC), activating above -100 mV. Both X-IRAC and X-QUAC were permeable for Cl(-) and NO(3)(-); X-QUAC was also permeable for malate. The occurrence of X-IRAC became more frequent with an increase in cytoplasmic Ca(2+), while the occurrence of X-QUAC decreased. Anion currents through X-SLAC, and particularly through X-QUAC, were estimated to be large enough to account for reported rates of xylem loading, which is in accordance with the notion that xylem loading is a passive process.

Anions↗
PubMed1999

Prophylactic antibiotic therapy is associated with an increased prevalence of Aspergillus colonization in adult cystic fibrosis patients.

Aspergillus colonization is a common phenomenon in adult cystic fibrosis (CF) patients. The clinical significance of Aspergillus for the pathogenesis of CF lung disease remains unclear and factors predisposing to such colonization are still completely unknown. We investigated the prevalence of Aspergillus colonization in 104 adult CF patients who attended our outpatient clinic in 1997. With respect to demographic and clinical data, and antibiotic therapy received, we further examined which factors were associated with Aspergillus colonization in these patients. Repeated investigations of CF sputum samples revealed Aspergillus species in 43/104 (41.3%; 95% confidence interval 30.2-52.5%) of the patients. We found no significant relationship between Aspergillus colonization and age (P > 0.4), gender (P = 0.4), colonization with pseudomonas species (P > 0.6), lower lung function values (P > 0.9), or worse chest radiography (P > 0.1). Surprisingly, the prevalence of Aspergillus colonization was higher in CF patients receiving prophylactic antibiotic therapy (oral antibiotics: P = 0.05; inhalative antibiotics: P = 0.035; both antibiotics: P = 0.048). Prophylactic antibiotics are widely used to eradicate or decrease chronic bronchopulmonary infection in CF. Our results indicate that long-term antibiotic therapy may predispose CF patients to Aspergillus colonization.

Adult↗
PubMed1999

Coenonia anatina gen. nov., sp. nov., a novel bacterium associated with respiratory disease in ducks and geese.

Taxon 1502 was originally described as a Riemerella anatipestifer-like bacterium causing exudative septicaemia in ducks and geese. In the present study, an integrated genotypic and phenotypic approach was used to elucidate the phylogenetic affiliation and taxonomic relationships of 12 strains of taxon 1502. Whole-cell protein and fatty acid analyses and an extensive biochemical examination by using conventional tests and several API microtest systems indicated that all isolates formed a homogeneous taxon, which was confirmed by DNA-DNA hybridizations. 16S rDNA sequence analysis of a representative strain (LMG 14382T) indicated that this taxon belongs to the Cytophaga-Flavobacterium-Bacteroides phylum and revealed a moderate but distinct relationship to species of the genus Capnocytophaga (overall 16S rDNA sequence identities were 88.8-90.2%). Taxon 1502 is concluded to represent a single species that should be allocated to a novel genus, and the name Coenonia anatina gen. nov., sp. nov. is proposed. The DNA G + C content of representative strains was 35-36 mol% and the type strain is LMG 14382T.

Animals↗
PubMed1999

Bilateral Wilms tumor in a boy with severe hypospadias and cryptochidism due to a heterozygous mutation in the WT1 gene.

Mutations in the WT1 gene causing Wilms tumors were first reported in WAGR syndrome (Wilms tumor, Aniridia, Genitourinary malformation, mental Retardation) and Denys Drash syndrome (pseudohermaphroditism, Wilms tumor, nephropathy), but only in a few patients with hypospadias and cryptorchidism without other signs of Denys Drash (DDS) or WAGR syndrome WT1 mutations were identified. We report a boy, who was born in 1989 with hypospadias and bilateral cryptorchidism. Previous karyotyping and endocrine studies had ruled out any known cause of male pseudohermaphroditism. Subsequently, he developed a bilateral Wilms tumor, which was detected by palpation at the age of 15 months during a routine visit by the general pediatrician. Because of its extensive size, surgery and chemotherapy were needed for treatment. Analysis of the WT1 gene was performed 5 y after diagnosis and revealed a C to T transition in one allele generating a stop codon at codon 362 and subsequently leading to a truncated protein with loss of its ability to bind to DNA. No signs of DDS or WAGR syndrome are present in the boy. The work up of this patient and the so far known few comparable cases from the literature lead to the conclusion that in newborns with severe urogenital malformations not due to known chromosomal or endocrine disorders mutational screening of the WT1 gene should be performed, to evaluate the high risk of developing a Wilms tumor. We favor mutational screening in these patients as an easy tool for investigation, because in the future it will probably decrease the necessity of frequent control visits in patients without a WT1 mutation.

Base Sequence↗
PubMed1999

[New knowledge of the molecular biology of enterohemorrhagic Escherichia coli (EHEC) O157].

Since 1982, enterohaemorrhagic Escherichia coli (EHEC) have been identified as a cause of diarrhoea and haemorrhagic colitis. The most serious complication of the infection is the haemolytic-uraemic syndrome (HUS) that develops in 5 to 10% of children with diarrhoea. Shiga toxins (Stx) are the most important presently known virulence factors of EHEC. After reaching the bloodstream, the toxins cause damage of endothelial cells but also of tubular cells in the kidneys which may result in renal failure. In EHEC O157 isolates from patients, we were able to identify seven different combinations of stx genes that occurred with different frequency. The genes encoding Stx are located in the genomes of prophages that are integrated in EHEC chromosomes. In addition, EHEC O157 strains possess a chromosomally located pathogenicity island (pais) termed LEE that contains numerous pathogenicity genes including the eae gene encoding intimin. Moreover, EHEC O157 strains possess a 93-kb plasmid harbouring genes encoding the EHEC-hemolysin (EHEC-HlyA), a serin protease (EspP) that cleaves factor V and a protein called ToxB that shows homology with the toxin B of Clostridium difficile. The EHEC O157 strains exist in two variants, namely non-sorbitol-fermenting (NSF) O157:H7 and sorbitol-fermenting (SF) O157:H- strains that are evolutionary older. Our results obtained up to now demonstrate marked differences in epidemiology of the infection caused by the respective EHEC O157 variants. EHEC O157:H7 strains occur worldwide, whereas SF strains have been hitherto found only in Germany and recently also in the Czech Republic. While the EHEC O157:H7 strains occur mainly during warm months, the SF strains are more frequent during the cold season of the year. In addition, differences exist with regard to the resistance to heavy metals, the plasmid structure, and the reservoir. We postulate that SF O157:H- strains occur only in the human intestine, whereas NSF O157:H7 strains have become adapted to other hosts, such as cattle, promoting a more rapid spread of the strains.

Animals↗
PubMed1998

Detection of acid production from carbohydrates by Riemerella anatipestifer and related organisms using the buffered single substrate test.

One hundred and twenty-one Riemerella anatipestifer field strains from wild birds, domesticated poultry and pigs were examined for their ability to produce acid from carbohydrates by using conventional biochemical and buffered single substrate (BSS) test methods. The type strains of the species R. anatipestifer and taxometrically related genera Chryseobacterium and Bergeyella were included in the study. In contrast to 10 indole-positive R. anatipestifer variant strains, only a few of the 111 typical indole-negative R. anatipestifer strains produced acid from dextrin (32%), glucose (17%), maltose (14%) and trehalose (5%) when the conventional test procedure was used. Using the BSS test all the field isolates and the type strain of R. anatipestifer produced acid from one or more carbohydrates, most of them from dextrin (96%), maltose (91%), glucose (87%), mannose (83%), less frequently from fructose (38%) and only in some cases from trehalose (19%). One hundred and six (87%) of the R. anatipestifer strains could be assigned to 8 biovars, based on the diversity of the carbohydrate acidification patterns. The remaining 16 R. anatipestifer isolates gave delayed reactions and displayed 13 different carbohydrate acidification profiles. The Chryseobacterium and Bergeyella type strains also produced acid from more carbohydrates when the BSS test was used. The BSS-carbohydrate acidification pattern of the Chryseobacterium indologenes strain was similar to that of R. anatipestifer biovar 3.

Animals↗
PubMed1998

A 3-year clinical evaluation of two composite resins in class-II cavities.

The purpose of this investigation was to study the clinical performance of a new system with a proposed expanding liner for composite restorations introduced in the late 1980s. The present study reports on baseline data and the result after 3 years. One hundred and four class-II cavities in 95 patients were alternatively restored by Superlux Molar and the reference material P-50 APC by 12 general practitioners in 3 public dental health clinics. After 3 years 82 restorations (79%) were available for examination. The restorations were evaluated on the basis of USPHS criteria after 1 week and again after 3 years. Stone casts were used to quantitatively categorize wear in accordance with the Leinfelder method. Color slides and bitewings were taken to supplement the clinical evaluation of color match and marginal adaptation, respectively, and secondary caries. The failure rate (USPHS rating, Charlie) was four restorations of Superlux Molar and seven of P-50 APC. The average wear after 3 years of Superlux Molar was 131 microm and of P-50 APC, 128 microm. There were no statistically significant differences between the two materials with regard to, for example, handling characteristics, anatomic form, color match, marginal discoloration, or failures. A significantly higher wear rate was found after 3 years in patients with a high level of salivary lactobacilli (> 10(5) colony-forming units (CFU)/mL at base line) compared with those with lower levels. This suggests that an acidic environment might enhance the wear rate.

Analysis of Variance↗
PubMed1997

Trends in dental health among Icelandic urban children.

Caries experience, oral hygiene and caries-related salivary parameters were recorded in a 20% representative sample of 12-year-old schoolchildren in Reykjavik, Iceland in 1991. The majority of the children was re-examined 3 years later in 1994. Trends in prevalence of caries and salivary bacteria were assessed by comparison with an analogous earlier longitudinal study (1984-87). Mean DFS values for 12-year-olds were 12.1 and 4.1, for 15-year-olds 23.3 and 11.3 in the earlier and later study, respectively. Reduction in DFS was 66% and 52% for the respective age groups. The decline was most pronounced in the group with low caries prevalence. Trends in caries experience were paralleled by salivary bacteria. The mean caries scores and frequency distributions of 15-year-olds in 1994 closely resembled those of 12-year-olds a decade earlier, suggesting a delay rather than a true fall in caries prevalence.

Adolescent↗
PubMed1997

Caries risk assessment in adolescents.

Detailed caries records and salivary microbiological tests were utilized to predict caries development in a group of 15-16-year-old Swedish adolescents. Both, caries experience and salivary microorganisms, correlated significantly with a subsequent 3-year increment of DFS. The strongest associations were recorded between the prevalence of baseline incipient lesions and the development of manifest caries (r = 0.51). Incipient lesions accounted for 27% of the 31% variability in the DFS increment explained by joined caries and salivary data. All predictors analysed showed insufficient sensitivity for identifying true caries active individuals. However, the combined sensitivity and specificity for incipient lesions and comprehensive caries record (incipient + manifest lesions) attained values allowing to predict caries development in the majority of individuals. Using precavity lesions as a sole predictor, 79-81% of the individuals were correctly classified with regard to their future caries levels. The addition of manifest caries increased the accuracy of classification to 86-89% depending on the stringency of screening and validation criteria.

Adolescent↗
PubMed1996

Screening for mutations of the human thyroid peroxidase gene in patients with congenital hypothyroidism.

While congenital hypothyroidism in 80-90% of the affected individuals is caused by thyroid dysgenesis (athyrosis, ectopy or hypoplasia), hypothyroidism in patients with a thyroid gland of normal position and size can be due to regulatory or enzymatic defects of thyroid hormone biosynthesis. Beside defects of thyroglobulinsynthesis, defects of the sodium-iodide-transporter or the TSH-receptor, a defect of the thyroidperoxidase, the key-enzyme of thyroid hormone biosynthesis, can cause a total iodide organification defect and thereby congenital hypothyroidism. We screened 14 of 103 patients (13.6%) with non familial congenital hypothyroidism and a normally developed thyroid gland detected by the newborn screening program with the PCR-SSCP (single-stranded-conformational-polymorphism) technique for mutations in the exons 2, 8, 9, 10 and 14 of the human thyroperoxidase gene, and in which mutations had been described previously in Dutch and Brazilian families with total organification defects. Most of the previously reported mutations were found in exons 8, 9 and 10 which code for the caralytic part of the enzyme. In two patients a GGCC-duplication in exon 8 was detected leading to a premature stop codon in exon 9. While one patient without neonatal goiter was homozygous for this mutation, the second patient was only heterozygous thus demanding another mutation on the second TPO-allel to explain the phenotype. Since the GGCC duplication is easily demonstrable by a NaeI digestion, because it creates a restriction site for this enzyme, screening for this mutation is indicated since it is easy to perform. In contrast to the perchlorate discharge test molecular genetic studies are less invasive, but as useful in making a definitive diagnosis in the individual patient. Furthermore it is the first feasible step to study the etiology and epidemiology of the so far only putative defects of thyroid hormone biosynthesis leading to congenital hypothyroidism.

Congenital Hypothyroidism↗
PubMed1996

Transient congenital hypothyroidism and hyperthyrotropinemia: normal thyroid function and physical development at the ages of 6-14 years.

Since the introduction of screening programs for congenital hypothyroidism, transient disturbances of thyroid function, especially transient congenital hypothyroidism and hyperthyrotropinemia, mostly due to iodine deficiency or contamination have been observed with variable frequencies. This study was carried out to reevaluate the thyroid function and physical development of 61 schoolchildren with transient congenital hypothyroidism or transient congenital hyperthyrotropinemia. Abnormalities were observed in 3 children. Thyroid function and growth were normal in all children, except 2 with moderately elevated TSH levels at the age of 7.7 and 10 yr in the presence of normal thyroid hormone levels. In 1 child, the TSH elevation was due to an ectopic hemithyroidea; in the other child, an unknown familial cause was suggested. In 1 girl (aged 12 yr), a euthyroid goiter caused by autoimmune thyroiditis was detected. We conclude from our investigation that frequent monitoring of thyroid function in children with transient congenital hypothyroidism or transient congenital hyperthyrotropinemia is not necessary during childhood if, postnatally, thyroid function recovered spontaneously. However, the growth and development of children with neonatal thyroid dysfunction should be followed, and if abnormalities occur, thyroid function tests are essential.

Adolescent↗
PubMed1995

Differences in the detection and enumeration of mutans streptococci due to differences in methods.

Different methods reported for assessing mutans streptococci (MS) make the direct comparisons of results across studies difficult. To quantitate the variations of MS estimates attributable to differences in method, stimulated and unstimulated saliva samples and oral swab samples were compared with pooled dental-plaque samples. Detection of MS in stimulated saliva samples was in excellent agreement with the presence of MS in pooled plaque samples. MS detection in unstimulated saliva samples, however, was significantly discordant with that in either pooled plaque or oral swab samples. When caries status was used as the criterion of validity of MS estimates, stimulated saliva samples demonstrated a sensitivity (94%) similar to that of pooled plaque samples, but exhibited a lower specificity (11%) than that of pooled plaque samples (17%). As a result, the measure of association between MS and caries was biased (towards null) when MS status was based on stimulated saliva samples. Interestingly though, in enumerating MS, stimulated saliva samples yielded significantly higher levels of MS (about 1.5 log10 increase) with a lower variability compared to unstimulated saliva samples. The use of different culture media for detection of MS gave different results as well. MS detection was poor (kappa = 0.31) and MS levels were lower (p = 0.0001) when samples were grown on glucose-sucrose-potassium tellurite-bacitracin agar compared to mitis-salivarius-bacitracin agar. Together with the relative ease of sampling and processing, these findings collectively justify the use of plaque samples for the qualitative assessment of MS and stimulated saliva samples for the quantitative assessment of MS, while providing a basis for adjustment of estimates when comparing results across studies.

Analysis of Variance↗
PubMed1995

Mutans streptococci, lactobacilli and caries experience in 12-year-old Icelandic urban children, 1984 and 1991.

In order to evaluate changes in salivary counts of cariogenic bacteria and relate these to trends in caries experience, stimulated saliva was collected from a 20% random sample of 12-yr-old residents of Reykjavik, Iceland (252 children) in 1991 under conditions consistent with those of a survey conducted in 1984. The mean and median counts of salivary mutans streptococci and lactobacilli remained similar in the two studies. However, the frequency distribution at lower levels of mutans streptococci differed significantly between 1991 and 1984, e.g. in the present study 25.8% of the children had < 10(5) compared with 13.8% in the study 1984. The mean caries prevalence in the permanent dentition (DFStot) was 11.0, which is significantly lower than in 1984 (mean DFStot 28.8). A significant difference in caries prevalence was found at various levels of salivary mutans streptococci. Strep. mutans (serotype c/e/f) was carried by all mutans streptococci-positive children, save one child, who carried only Strep. sobrinus. The proportion of 12-yr-olds who carried Strep. sobrinus had decreased significantly to 15.7% from 34.0% in 1984. Significantly more children with Strep. sobrinus showed high levels of total mutans streptococci than children with only Strep. mutans. As the case was in 1984 significantly more Strep. sobrinus carriers had a high level of salivary lactobacilli as well as higher caries prevalence than the children who did not carry this species.

Child↗
PubMed1995

Mutans streptococci and dental caries prevalence in a group of Latvian preschool children.

Paraffin-stimulated saliva samples were collected from 140 children 3- and 4-yr old attending nine nursery schools in Latvia. The salivary levels of mutans streptococci were rated from zero to 3 after being cultured on a commercially available strip selective for these microorganisms. Of the children, 29.3% were rated at zero (approximately < 10(4) cfu per ml saliva). This group of children demonstrated the lowest mean caries prevalence dmfstot = 1.5 (SD 1.9). The highest dmfstot was found among children in class 2 (38.6%; approximately > 10(5)-10(6) cfu/ml) and class 3 (12.1%; approximately > 10(6) cfu/ml) with a mean caries prevalence of 6.5 (SD 5.8) and 6.4 (SD 6.0), respectively. The study demonstrates the association between high caries prevalence and high salivary levels of mutans streptococci in the young child. It is suggested that early identi-fication of mutans streptococci-colonized children might be of value in selecting at caries risk children for preventive measures.

Child, Preschool↗
PubMed1995

Clinical evaluation of a Mycobacterium tuberculosis PCR assay.

On the basis of previously published PCR primer sequences, we have designed a sensitive system for detecting DNA of the Mycobacterium tuberculosis complex (MTB) in patient sputum samples which employs a fast and simplified sample preparation method appropriate for routine diagnostic testing. In order to evaluate the accuracy of the PCR assay, we performed a prospective study with 103 patients, comparing PCR results with culture results of samples obtained from a parallel culture assay as well as with subsequent culture results. Using two MTB-specific PCR primer systems, we found 48 of 49 tuberculosis (Tb) patients to be PCR positive (PCR sensitivity, 0.98). Sixteen of 54 presumably non-Tb patients showed amplifiable MTB DNA (specificity, 0.7). The study demonstrates that for diagnostic applications of MTB PCR two MTB-specific primer pairs should be used. MTB infection is extremely unlikely in cases of MTB PCR-negative samples: with our method for the exclusion of active Tb, the validity of one PCR assay seems to be equivalent to those of at least three culturing procedures. Positive PCR results do not necessarily reflect active MTB infection. It remains to be shown whether positive PCR results in Tb-negative patients mean false-positivity, an early laboratory finding which predicts a subsequent reactivation of a prior Tb infection, or whether asymptomatic patients may carry PCR-amplifiable MTB DNA without any clinical relevance. It is important to point out that the validity of PCR results in clinical studies depends on the use of contamination controls parallel to all PCR steps and the simplicity of the DNA extraction method as well as on the specificity of the PCR results.

Base Sequence↗