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Biomedical subjects

A Koch

Publications and source records attributed to A Koch.

At least 109 records · Page 6Linked to original sources
PubMed2001

A novel transgenic model to characterize the specific effects of follicle-stimulating hormone on gonadal physiology in the absence of luteinizing hormone actions.

Gonadal function is wholly reliant on the two pituitary-derived gonadotropins, FSH and LH. Identifying the specific effects of FSH has been difficult because of the intimate relationship between LH and FSH action and inherent limitations of classic research paradigms. We describe a novel transgenic model to characterize the definitive actions of FSH alone, distinct from LH effects, created by combining transgenic FSH expression with the gonadotropin-deficient background of the hypogonadal (hpg) mouse. A tandem transgene construct encoding each alpha- and beta-subunit of human FSH, under the rat insulin II promoter, expressed biologically active heterodimers at serum levels, by immunoassay, equivalent to circulating FSH concentrations in fertile humans (0.1-25 IU/liter). Transgenic mice were crossed into the hpg mouse genotype to obtain LH-deficient animals secreting FSH alone. Testis weights of adult FSHxhpg mice were increased up to 5-fold, relative to nontransgenic hpg controls (P < 0.001). However, only transgenic males with serum FSH levels more than 1 IU/liter showed testis weights increased relative to hpg controls, indicating a physiological FSH threshold for the testicular response. Histology of enlarged FSHxhpg testes revealed round spermatids and sparse numbers of elongated spermatids, demonstrating that the testosterone-independent FSH response targeting the Sertoli cell can facilitate completion of meiosis and minimal initiation, but not completion, of spermiogenesis. Transgenic FSH also induced inhibin B secretion in FSHxhpg mice, but showed a distinct sexual dimorphism with only females exhibiting a strong FSH dose-dependent increase in serum inhibin B levels (r(2) = 0.84). In addition, ovaries of FSHxhpg females were enlarged up to 10-fold (P < 0.001), characterized by increased follicular recruitment and development to type 7 antral follicles. Thus, these findings show that the transgenic FSHxhpg mouse provides a unique model for detailed investigations of the definitive in vivo actions of FSH alone.

Animals↗
PubMed2001

Beta(1-->3)-glucan in house dust of German homes: housing characteristics, occupant behavior, and relations with endotoxins, allergens, and molds.

beta(1-->3)-Glucans are potent proinflammatory agents that have been suggested to play a role in indoor-related respiratory health effects. The aim of this study was to assess whether beta(1-->3)-glucan concentrations in house dust are correlated with levels of endotoxins, allergens, and culturable mold spore counts in house dust. Further, the associations of beta(1-->3)-glucan with housing characteristics and occupant behavior were assessed. beta(1-->3)-Glucan was measured in settled house dust from living room floors of 395 homes of two German cities, Erfurt and Hamburg, with a specific enzyme immunoassay. Concentrations ranged from below the limit of detection to 19,013 microg/m(2) (22,588 microg/g dust). Concentrations per square meter were found to be correlated with endotoxins, mite and cat allergens, and culturable mold spores. Correlations were weaker when concentrations were expressed per gram of dust, indicating that variance in concentrations of all factors is largely determined by the amount of dust sampled. Associations between beta(1-->3)-glucan, housing characteristics, and occupant behavior were found for concentrations per square meter but not for concentrations per gram of dust. The following characteristics were associated with a significant increase in beta(1-->3)-glucan levels: carpets in the living room [means ratio (MR) = 1.9-2.1], keeping a dog inside (MR = 1.4), use of the home by four or more persons (MR = 1.4), use of the living room for > 180 hr/week (MR = 2.1), lower frequency of vacuum cleaning (MR = 1.6-3.0) and dust cleaning (MR = 1.2 and 1.4, respectively), and presence of mold spots during the past 12 months (MR = 1.4). We conclude that that the amount of dust sampled can be used as a proxy for hygiene and that beta(1-->3)-glucan concentrations per square meter are related to the amount of dust sampled.

Air Pollution, Indoor↗
PubMed2001

Deficits and remedy of the standard random effects methods in meta-analysis.

The random effects model is often used in meta-analyses. A corresponding significance test based on a normal approximation has been established. Its type I error is derived in this article by theoretical considerations and computer simulations. The test can be conservative as well as unacceptably anti-conservative. The anti-conservatism increases with the increasing number of patients and the decreasing number of studies. A modification is proposed, which keeps the nominal level asymptotically as the number of patients approaches infinity. Simulations show that the modified test is often conservative, but its conservatism is small in those situations where the standard test is highly anti-conservative.

Bias↗
PubMed2000

Src homology 2-containing inositol 5-phosphatase 1 binds to the multifunctional docking site of c-Met and potentiates hepatocyte growth factor-induced branching tubulogenesis.

Hepatocyte growth factor (HGF)/scatter factor is a multifunctional cytokine that induces mitogenesis, motility, and morphogenesis in epithelial, endothelial, and neuronal cells. The receptor for HGF/scatter factor was identified as c-Met tyrosine kinase, and activation of the receptor induces multiple signaling cascades. To gain further insight into c-Met-mediated multiple events at a molecular level, we isolated several signaling molecules including a novel binding partner of c-Met, SH2 domain-containing inositol 5-phosphatase 1 (SHIP-1). Western blot analysis revealed that SHIP-1 is expressed in the epithelial cell line, Madin-Darby canine kidney (MDCK) cells. SHIP-1 binds at phosphotyrosine 1356 at the multifunctional docking site. Because a number of signaling molecules such as Grb2, phosphatidylinositol 3-kinase, and Gab1 bind to the multifunctional docking site, we further performed an in vitro competition study using glutathione S-transferase- or His-tagged signaling molecules with c-Met tyrosine kinase. Our binding study revealed that SHIP-1, Grb2, and Gab1 bound preferentially over phosphatidylinositol 3-kinase. Surprisingly, MDCK cells that overexpress SHIP-1 demonstrated branching tubulogenesis within 2 days after HGF treatment, whereas wild-type MDCK cells showed tubulogenesis only after 6 days following treatment without altering cell scattering or cell growth potency. Furthermore, overexpression of a mutant SHIP-1 lacking catalytic activity impaired HGF-mediated branching tubulogenesis.

Animals↗
PubMed2000

The direct association of the multiple PDZ domain containing proteins (MUPP-1) with the human c-Kit C-terminus is regulated by tyrosine kinase activity.

We have identified the multiple PDZ domain containing protein (MUPP-1 or MPDZ) as a novel binding partner of the human c-Kit. c-Kit binds specifically to the 10th PDZ domain of MUPP-1 via its C-terminal sequence. Furthermore, a kinase negative-mutant receptor interacted more strongly with MUPP-1 than the wild-type c-Kit. Strikingly, a constitutively activated c-Kit (D816V-Kit) did not bind to MUPP-1, although this oncogenic form retains the PDZ binding motif 'HDDV' at the C-terminal end. Deletion of V967 of c-Kit abolished binding to MUPP-1 and drastically reduced its tyrosine kinase activity, suggesting that the structure of the C-terminal tail of c-Kit influences its enzymatic activity.

Amino Acid Sequence↗
PubMed2000

[Population screening for HIV in Sisimiut, Greenland].

INTRODUCTION: In the years 1985-1998, 91 HIV-positive persons were diagnosed in Greenland, resulting in an incidence of HIV infection three times higher in Greenland than in Denmark. Of these cases 25% were diagnosed in Sisimiut, which, however, only comprises 10% of the total population of Greenland. In spite of an active HIV case-tracing programme at the Health Centre, there was a fear of unknown HIV-positives in the town. Therefore, the Health Centre initiated an HIV screening campaign among all adults and school children in the town of Sisimiut and two adjacent settlements. MATERIAL AND METHODS: The screening campaign was carried out in the weeks 46 and 47 in November 1998 by the staff at the Health Centre. All participants filled out a questionnaire concerning demographic variables, and had blood samples drawn. For adults the campaign mainly took place in the community centre and the large work places, and for the children at the schools. Blood samples were tested for antibodies against HIV 1 and 2 at Statens Serum Institut using ELISA tests and confirmatory Western Blot. RESULTS: Of the total population of 4807, 2858 persons took part in the screening campaign (participation rate 59%). Among adults the participation rate was 50%, and for children aged 6-17 years the rate was 86%. Four HIV-positive persons were tested positive. Of these three were already known HIV-positives, and the last person was highly suspect of HIV infection. DISCUSSION: There is no evidence of widespread HIV infection in Sisimiut. No unknown groups of HIV-positive persons were identified. Thus, the intensive case-tracing programme as carried out by the Health Centre seems effective.

Adolescent↗
PubMed2000

[CONSORT--What is to be expected from a reputable scientific publication].

The publication of the CONSORT Statement was aimed at the improvement of the quality of research reports of randomized controlled clinical trials. It contains the most important standards of high quality research. Although originally meant for randomized studies only most aspects of this statement can be applied to other kinds of clinical studies. The following--and last--article of this series on medical biostatistics presents and comments the most important criteria.

Clinical Trials as Topic↗
PubMed2000

Direct interaction of nerve growth factor receptor, TrkA, with non-receptor tyrosine kinase, c-Abl, through the activation loop.

The nerve growth factor receptor, TrkA, is essential for the survival and differentiation of neurons in the central and peripheral nervous systems. To understand the molecular principles underlying this differentiation step, we employed a yeast two-hybrid screening protocol using human TrkA as bait. We isolated c-Abl as a TrkA-interacting protein, in addition to known proteins such as phospholipase Cgamma and SH2-B. This interaction was confirmed by an in vitro binding assay using glutathione S-tranferase-Abl fusion protein. Furthermore, we show here that c-Abl binds to phosphotyrosine residue(s) in the kinase activation loop of TrkA.

Adaptor Proteins, Signal Transducing↗
PubMed2000

[Meta-analysis as a tool for evaluation of evidence].

In these days, more than one clinical trial is mostly performed to evaluate a new treatment or therapeutic intervention. This necessitates a combined evaluation of their results. An integration of evidence from several trials is also helpful to determine the actual knowledge. These are the main goals of meta-analyses. Since the end of the 80s meta-analyses are widely used in clinical research. At the beginning of a meta-analysis, a protocol has to be developed. Similar to a protocol of a clinical trial, the inclusion and exclusion criteria for trials, the hypotheses and the planned analyses have to be fixed. After a careful localization of trials, a combined statistical analysis is performed. An investigation of heterogeneity, i.e., differences between study results, is indispensable. During the last years, the tool meta-analysis has been criticized. The criticism mainly results from poorly conducted meta-analyses which generated results without prespecifying hypotheses or which merely combined study results. Well-planned meta-analyses, on the contrary, have an increasing influence in clinical research.

Clinical Protocols↗
PubMed2000

Immunohistochemical examination of the INK4 and Cip inhibitors in the rat neonatal cerebellum: cellular localization and the impact of protein calorie malnutrition.

Expression of the cyclin-dependent kinase inhibitors (CKIs) has been linked to the inhibition of cellular proliferation and the induction of differentiation. Based on structure function analysis, two distinct families of CDKIs, the INK4 and the Cip/Kip family have been identified. The INK4 family member p16(Ink4), and the Cip/Kip protein p27(Kip1) have been implicated in normal development of the CNS and cerebellum. Recent studies have suggested a functional inter-dependence between the CKI and the abundance of cyclin D1 in orchestrating growth factor-induced cellular proliferation. The neonatal rat cerebellum undergoes proliferative growth and differentiation, localized to distinct topographical regions and cell types. The cell type and the temporal profile of CKI expression during postnatal cerebellar development had not been described. The current studies determined the specific cerebellar cell types in which the CKIs were expressed during post natal development by co-staining for cell-type specific markers. p16(Ink4a) and p27(Kip1) immunostaining was identified in both neurons and glial cells, increasing progressively between postnatal days 6 to 13 into adulthood. By contrast, neuronal and glial cell p21(Cip1) staining was prominent at days 6-11 and decreased thereafter. Cyclin D1 was expressed in the proliferating external granular cells, with occassional staining in the molecular, and internal granular layers. Dual immunostaining demonstrated cyclin D1 within cells expressing CKI (p16(Ink4a), p21(Cip1),p27(Kip1)). Cerebellar cellular growth arrest, induced by protein-calorie malnutrition, inhibited cyclin D1 protein levels without affecting CKI immunostaining suggesting CKI do not mediate the developmental arrest. These results demonstrate that the CKIs are induced by differentiation cues in specific cell types with distinct kinetics in the developing cerebellum in vivo.

Animals↗
PubMed2000

Hepatocyte growth-factor-scatter factor can stimulate post-operative tumor-cell proliferation in childhood hepatoblastoma.

Rapid growth of residual tumor after partial hepatectomy has been observed during the period of liver regeneration in children with malignant embryonal hepatoblastoma. The aim of this study was to elucidate the role of hepatocyte growth-factor-scatter factor (HGF-SF) in this phenomenon. Markedly increased serum levels of HGF-SF up to 15 ng/ml were found in 13/18 patients after liver resection and in 6/16 patients with regressive tumors after chemotherapy, in comparison with 15 patients with non-pre-treated hepatoblastoma and 20 healthy children of the same age group. In the tumors, epithelial tumor cells highly expressed the HGF-SF receptor c-met, as shown by immunohistochemistry and m-RNA RT-PCR. The hepatoblastoma cell lines HepT1, HepT3 and HUH6 reacted with significantly increased proliferation to rhHGF-SF in these concentrations (1-15 ng/ml). In the tumors, HGF-SF was found to be expressed in the stromal fibroblasts. In culture, hepatoblastoma cells (HepT3, HUH6) stimulated secretion of the factor by human fibroblasts, indicating the paracrine fashion of intratumoral HGF-SF production. Cultured hepatoblastoma cells ceased to proliferate at 20-50 ng/ml HGF-SF, and they underwent cell death at >/=100 ng/ml. In contrast, the hepatocellular-carcinoma cell line HepG2 decreased growth under HGF-SF in a dose-dependent manner. We conclude that post-operatively secreted and intratumorally produced HGF-SF can function as a growth factor for hepatoblastoma, while the same agent has a cytostatic effect in unphysiologically high concentrations.

Cell Division↗
PubMed2000

[Partial anomalous origin of the left pulmonary artery].

The pulmonary sling or aberrant left pulmonary artery has an incidence of 3% to 6% of all anomalies of the aortic arch system. We report a boy with coexistence of a normal and an anomalous left pulmonary artery. Associated congenital anomalies were coarctation, mitral stenosis, and imperforate anus. Cardiac catheterization and angiocardiography at the age of 5 months demonstrated an inconspicuous pulmonary trunk dividing into left and right branches. There was a normal right pulmonary artery, and a main left pulmonary artery supplying the left upper lobe, lingula, and anterior segments of the left lower lobe. In addition, an anomalous left lower lobe artery originated from the proximal right pulmonary artery, passed inferior to the tracheal bifurcation to the left supplying posterior segments of the left lower lobe. Chest X-rays and bronchoscopy could not detect any malformation of the trachea and pulmonary lobulation. There are only three reports of partial anomalous origin of the left pulmonary artery, and only one had a similar course of the accessory artery. This report is the first to present selective angiography and echocardiographic findings of the partial anomalous left pulmonary artery. The development of the partial anomalous pulmonary artery can be explained by the plexiform nature of the primary pulmonary vascular bed and can help to understand the embryology of the pulmonary arteries.

Abnormalities, Multiple↗
PubMed2000

[Late postoperative cardiac arrhythmias after total cavopulmonary anastomosis and correlation with age of the patients at operation].

Late postoperative arrhythmias are a common problem associated with significant morbidity following Fontan operations. We analyzed in our patients whether age at the time of a modified Fontan procedure (total cavopulmonary connection) has an influence on the frequency of late postoperative arrhythmias. We examined all 66 long-term surviving patients who underwent a total cavopulmonary connection (TCPC) in our center during a nine year period. At the time of TCPC, 31 children were younger (group I) and 35 children were older than 4 years (group II). The follow-up period was almost identical in both groups (group I: 4.29 years, group II: 4.52 years). We evaluated all ecgs performed at maximum intervals of 6 months and all Holter ecgs performed at intervals of 12 months. Atrial tachyarrhythmias (supraventricular tachycardias, atrial flutter) were registered in six patients (9%). All of these patients belonged to group II (17%). Ventricular arrhythmias (couplets, ventricular tachycardia) were found in 3% of the younger and 17% of the older patients. Abnormalities of sinus node function were registered in equal frequency in younger and older children (group I: 35%, group II: 31%), while pauses with a duration of > 2 s where present only in older children (group II: 14%). Pacemaker implantation or antiarrhythmic therapy became necessary in 10/66 patients (15%) affecting none of the children who underwent the TCPC < 4 years (group I) but 10/35 children (group II) who underwent the TCPC at an older age (29%). According to our findings in the medium-term follow-up after TCPC, atrial tachyarrhythmias and complex ventricular arrhythmias are registered less frequently in children who underwent the modified Fontan procedure at an age of less than 4 years. Although further studies will have to show whether these differences persist in the long-term follow-up, these findings represent an additional argument for the elective performance of modified Fontan operations at an age of less than 4 years.

Adolescent↗
PubMed2000

p57(KIP2) is not mutated in hepatoblastoma but shows increased transcriptional activity in a comparative analysis of the three imprinted genes p57(KIP2), IGF2, and H19.

Hepatoblastomas (HBs), representing malignant liver tumors of childhood, show frequent loss of heterozygosity (LOH) in the chromosomal region 11p15.5. This loss is of maternal origin suggesting the presence of a monoallelically expressed tumor suppressor gene in this region. p57(KIP2) (KIP2) located at 11p15.5 is predominantly expressed from the maternal allele and encodes a cyclin-dependent kinase inhibitor. We screened a series of 56 HB tumors and five HB cell lines for allelic loss (LOH) of the KIP2 locus by microsatellite analysis and KIP2 coding sequence mutations by single-strand conformation polymorphism analysis. Although LOH at the KIP2 locus occurred in 25% of the cases, no mutations were found. Analysis of KIP2 mRNA expression by competitive reverse transcriptase-polymerase chain reaction revealed up-regulation in nine of 12 HBs compared to matching liver samples. In contrast, mRNA levels of the putative suppressor gene H19 on 11p15.5 were decreased in 10 of 12 tumors, indicating that KIP2 and H19 are not co-regulated in HBs. IGF2 mRNA expression was increased in 11 of 12 HB samples. All HBs showed monoallelic KIP2 expression. However, the overexpression of KIP2 in HBs with maternal loss of 11p15.5 suggests a reactivation of the paternal allele in these cases. Overexpression of KIP2 in HBs argues against a role as a HB suppressor gene.

Child, Preschool↗
PubMed2000

Determining body fuels of wintering mallards.

Measuring body lipids and proteins of wild animals such as mallards is essential to determine the impact of the environment on their body condition. A major difficulty, however, is that biochemical analysis of carcass is tedious and therefore cannot be applied at a large scale. The main objective of this study was therefore to find out if simple measurements can be used as indices of total body lipids and proteins. Four classes of lipid and protein indices, derived on a 'source' group, were defined according to their complexity and condition of application (field or laboratory). Accuracy of the indices was evaluated on an independent group, of which the body composition calculated from indices was compared to carcass analysis. In live birds, body mass was an accurate and convenient predictor for both lipid and protein masses. If carcasses are available, extensive analysis provides a higher accuracy for body lipids only. This can be simply obtained through multiple regressions using abdominal fat mass and/or dry body mass.

Animals↗
PubMed2000

The vascular endothelial system in the pathogenesis of inflammation and systemic rheumatic diseases: relation to the neuroendocrine system.

There is no doubt that the VES plays a central role in the pathogenesis of immune-mediated and inflammatory conditions. Equally, there is no doubt about the strong influence played by the neuroendocrine-immune system on the pathophysiology and homeostasis of the VES. Nevertheless, much remains to be done to unravel the precise mechanisms by which these systems interact in determining the microvascular dysfunction associated with chronic immune-mediated inflammation.

Androgens↗
PubMed2000

Similarities and differences in the exercise performance of patients after a modified Fontan procedure compared to patients with complete transposition following a Senning operation.

OBJECTIVE: To investigate cardiopulmonary performance in patients after a Fontan procedure, comparing it to patients following a Senning operation. METHODS: We studied 21 children, with a mean age of 11.1 years, after a total cavopulmonary anastomosis, comparing them to 13 with complete transposition after a Senning procedure, having a mean age of 11.8 years, and 21 control subjects with a mean age of 11.2 years. All were tested on a bicycle ergospirometer. RESULTS: Peak consumption of oxygen, maximal work rate, peak oxygen pulse and endexpiratory pressure of carbon dioxide at a work rate of 1.5 Watt/kg were lowest in patients with a modified Fontan procedure, and highest in the control group (p < or = 0.0278). Production of carbon dioxide, and minute ventilation at a work rate of 1.5 Watt/kg, was highest in the patients after Fontan procedure, and lowest in the healthy subjects (p < or = 0.0163). Production of carbon dioxide per single breath was lower in those having a Fontan procedure (28.9 ml) than in the two other groups (35.1 ml; p = 0.0243). The tidal volume showed no significant differences between the three groups. CONCLUSIONS: The reaction to exercise was identical qualitatively in both groups of patients, and comparable to the behaviour of patients with chronic heart failure. Quantitatively, the results of the patients following a Senning procedure lay between those of control subjects and those who had undergone a Fontan operation. The only exception was dead space ventilation, where the patients after a Fontan procedure differed from the two other groups because of their increased ventilation-perfusion mismatch.

Anastomosis, Surgical↗