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Biomedical subjects

A Koch

Publications and source records attributed to A Koch.

At least 217 records · Page 12Linked to original sources
PubMed1996

Variable imprinting of H19 and IGF2 in fetal cerebellum and medulloblastoma.

Only the maternal or paternal allele of an imprinted gene is expressed in somatic cells. The gene for insulin-like growth factor II (IGF2) and the H19 gene (a putative tumor suppressor gene) are imprinted in humans with monoallelic paternal and maternal expression, respectively. Loss of imprinting (LOI) (i.e., biallelic expression) of IGF2 occurs in some tumors and may promote tumor growth. We examined imprinting of IGF2 and H19 in 6 fetal cerebella, 1 adult cerebellum, 15 medulloblastomas, and 7 medulloblastoma cell lines using polymerase chain reaction (PCR) and reverse transcription-PCR of exonic polymorphisms. Loss of imprinting of IGF2 occurred in 2 out of 3 informative fetal cerebella, 3 out of 7 informative medulloblastomas, and 1 out of 4 informative cell lines. Loss of imprinting of H19 occurred in 0 out of 4 informative fetal cerebella, 0 out of 1 informative adult cerebellum, 4 out of 8 informative medulloblastomas, and 1 out of 4 informative cell lines. The biallelic expression of H19 was only partial in two medulloblastomas, however, with one allele being significantly weaker than the other. Loss of imprinting of IGF2 occurs in medulloblastomas or medulloblastoma cell lines but can also occur in normal fetal cerebellum. Its occurrence in medulloblastomas may therefore reflect the tumors' embryonal nature rather than representing a primary pathogenetic mechanism. Our data also indicate that both genes can be imprinted and expressed independently of each another, both in normal cerebellum and medulloblastomas.

Adult↗
PubMed1996

Gliding motility in slide cultures of Myxococcus xanthus in stable and steep chemical gradients.

A method was devised to construct stable and steep chemical gradients in slide cultures to study the movements of gliding cells. The movement of Myxococcus xanthus individual cells and small swarms was studied in these gradients. There was no response to gradients of Casitone and yeast extract that were previously reported to stimulate a positive chemotactic response with M. xanthus.

Caseins↗
PubMed1996

[The musculus pectoralis major rib flap. Personal experiences with 7 cases].

We present a report of our experience with one-step reconstruction of the mandible after resection in tumor cases using an osteomyo-cutaneous flap. We performed a pectoralis major flap with a segment of the fifth rib, blood supplied by the periosteum. In seven cases we had one pseudoarthrosis. The complications in the donor site were none. We see in the pectoralis major-rib flap an alternative to microsurgical techniques, especially in patients with defects in the horizontal part of the mandible.

Adult↗
PubMed1996

Molecular analysis of the lissencephaly gene 1 (LIS-1) in medulloblastomas.

Although medulloblastoma (MB) represents the most frequent malignant brain tumour in children, the molecular pathogenesis of this tumour is still poorly understood. Microsatellite and RFLP studies have revealed allelic losses on the short arm of chromosome 17 in the region 17p13 in approximately 50% of MBs. A candidate for this putative MB suppressor on chromosome 17p13.3 is the recently cloned LIS-1 gene which codes for a regulatory subunit of the intracellular form of the platelet activating factor (PAF) acetylhydrolase. PAF is involved in signal transduction pathways during cerebral development and in the process of neuronal cell migration and differentiation. In this study, 42 medulloblastomas including seven tumour cell lines and 35 primary tumours were analysed for LIS-1 mRNA expression by RT-PCR and Northern blot analysis. Twenty-four paired blood and MB DNA samples were examined by PCR analysis with a panel of microsatellites located on chromosome 17p to detect loss of heterozygosity (LOH). Finally, the single-strand conformation polymorphism (SSCP) technique and DNA sequencing were employed to detect mutations or small deletions in the coding region of the LIS-1 gene. Of 24 MBs, 13 exhibited loss of heterozygosity on chromosome 17p13.3 for at least one of the microsatellite markers. LIS-1 mRNA expression was detected in all MB tumours and MB cell lines. None of the tumours showed a somatic mutation in the LIS-1 coding region. A novel polymorphism in the 3'UTR of LIS-1 was found in MB patients, but also in healthy control persons. These data indicate that the LIS-1 gene located at 17p13.3 is not involved in the molecular pathogenesis of MBs.

Adolescent↗
PubMed1995

Effectiveness of various sperm processing methods in removing seminal plasma from insemination media.

The effectiveness of the wash and swim-up (1 and 2 wash cycle), two layer Percoll gradient, SpermPrep and underlay sperm preparation methods in removing seminal plasma from insemination suspensions was investigated. The number of wash cycles needed to rid sperm suspensions of seminal plasma (n = 15) was also determined. All sperm preparation methods were compared to the control wash and swim-up method, performed using Earle's buffered salt solution (EBSS), without serum supplementation so as not to mask seminal plasma concentrations. Control processing comprised 1 ml semen subjected to two wash cycles in EBSS followed by a swim-up period of 60 min under 5% CO2 in air. The Percoll method comprised 1 ml semen layered on a discontinuous 36 and 81% Percoll gradient (n = 14). In the SpermPrep method, 1 ml semen was run through a SpermPrep II column (n = 10), and underlay samples (n = 12) were processed by two wash cycles, after which sperm pellets were resuspended in the remaining medium, layered under 1.2 ml EBSS and allowed to swim up under 5% CO2 in air for 1 h. Seminal plasma and supernatant fractions obtained after each processing phase were stored at -20 degrees C and protein concentrations were determined by spectrophotometry. The wash and swim-up method was the most effective in removing seminal plasma from sperm suspensions, followed by the two-layer Percoll gradient, underlay and finally the SpermPrep II processing methods.

Chemical Fractionation↗
PubMed1995

Effect of growth hormone on IGF-I levels in a patient with growth hormone deficiency and Wilson disease.

This is a case report of a boy with a combination of two rare disorders:growth hormone deficiency (GHD) and Wilson disease. To our knowledge, no comparable case has yet been published in the literature. GHD was diagnosed at the age of 4.5 years (height standard deviation score (SDS) -4.85). However, because of a difficult family background, growth hormone (GH) therapy could not be started. The boy was not seen again until the age of 7.7 years (height SDS -4.77), when GHD was reconfirmed and GH therapy could be initiated (dose 0.6 IU/kg/week). At that time, elevated liver enzymes (GPT 128 U/l, GOT 67 U/l, gamma-GT 28 U/l) confused diagnostic procedures. On GH, growth velocity SDS increased from -1.86 to +4.50 in the first year and +3.87 in the second year, and height SDS increased to -4.26 and -3.59. However, serum IGF-I levels did not normalize (max. 67 ng/ml), and liver enzymes were still elevated. At the age of 10 years, Wilson disease was diagnosed in view of low concentration of serum ceruloplasmin, elevated urinary copper excretion and high copper content in a liver biopsy sample. Under a combined therapy with D-penicillamine and GH, serum liver enzymes decreased, and IGF-I levels increased to normal. Height SDS for chronological age has improved constantly.

Ceruloplasmin↗
PubMed1995

Mapping of the spinal muscular atrophy (SMA) gene to a 750-kb interval flanked by two new microsatellites.

The gene for autosomal recessive proximal spinal muscular atrophy (SMA) has recently been mapped between D5S629 and D5S557. We report here a new single-locus microsatellite A31 (D5S823) and two multicopy microsatellites 97T-CA and 95/23-CA. The marker A31 maps to the region of overlap between YACs y116, y55 and y122, distal to D5S629; 97T-CA originates from a cosmid corresponding to the STS 97T, localized distally to A31, while 95/23-CA derives from a cosmid corresponding to the STS 97U, localized proximally to D5S557. We tested all our key recombinant families with these markers. In one type I/II SMA family, a recombinant was found that placed the SMA locus distal to D5S823. Homozygosity mapping in a consanguineous type I SMA family indicates that the SMA gene lies proximal to 95/23-CA. Thus, the two new markers, A31 and 95/23-CA further refine the SMA gene to an approximately 750-kb interval.

Base Sequence↗
PubMed1995

Nested polymerase chain reaction study of 53 cases with Turner's syndrome: is cytogenetically undetected Y mosaicism common?

Turner's syndrome patients with Y mosaicism face a high risk of developing gonadoblastoma. Cytogenetic analysis can fail to detect rare cells bearing a normal or structurally abnormal Y chromosome (low level Y mosaicism). We screened 53 individuals with Turner's syndrome for presence of sex-determining region Y (SRY), the testis-specific protein, Y encoded, gene, and the Y centromeric DYZ3 repeat using nested polymerase chain reaction (PCR). Thirty girls (57%) had the 45,X karyotype, determined through standard analysis of blood lymphocytes. The remaining 23 girls (43%) were mosaics and/or had structural abnormalities in 1 X-chromosome. Genomic DNA from blood leukocytes was amplified using 2 rounds of PCR. This method was sensitive enough to detect 0.0001% male DNA on a female background. None of 53 Turner's syndrome cases was positive for Y-specific loci after the first round of PCR. After the second round, 2 of 53 Turner's syndrome cases were positive for SRY mapping to the distal short arm of chromosome Y. In 1 SRY-positive subject, the karyotype was 45,X, and in the other, it was 46,Xi(Xq). None of 53 Turner's syndrome individuals, including the 2 SRY-positive subjects, were positive for the testis-specific protein, Y encoded, gene on the proximal short arm of chromosome Y or the centromeric DYZ3 repeat. These data exclude low level Y mosaicism in almost all Turner's syndrome cases tested.

Base Sequence↗
PubMed1995

Electrophysiology of K+ transport by midgut epithelium of lepidopteran insect larvae. III. Goblet valve patency

The midgut epithelium of lepidopteran insect larvae contains characteristic goblet cells possessing an apical cavity surrounded by goblet cell apical membrane (GCAM) and guarded from the gut lumen by a valve-like structure. The currently accepted model of active K+ secretion by the midgut of lepidopteran insect larvae locates the major active step at the GCAM, implying that actively transported K+ reaches the gut lumen by passing through the valve. The major question for these studies was whether K+ could pass through the valve by diffusion in free solution. Using tetramethylammonium (TMA+) as a surrogate for K+, and exploiting the high sensitivity of standard K+-selective ion-exchange resin to quaternary amines, we used K+-selective intracellular electrodes to measure the rate of access of apically applied TMA+ to the goblet cavity. TMA+ failed to gain access to more than half of the cavities. For those cavities to which it did gain access, the influx and efflux rates and predicted equilibrium concentrations of TMA+ were too low to be consistent with diffusive exit of transported K+ along the same path. Upon superfusion with cytochalasin E, a disrupter of actin-based cytoskeleton, the TMA+ influx rates immediately increased for those cavities previously accessible to TMA+, but not for those previously inaccessible. Increases in TMA+ influx suggestive of spontaneous valve opening were not observed. The results are consistent with an indirect route of access of TMA+ to goblet cavities. We conclude that goblet valves are closed in vitro. Assuming that the goblet cavity is part of the transport route, actively transported K+ must exit the cavity to the gut lumen by a mechanism that does not involve diffusion in free solution.

Journal Article↗
PubMed1995

Electrophysiology of K+ transport by midgut epithelium of lepidopteran insect larvae. IV. A multicompartment model accounts for tetramethylammonium entry into goblet cavities

A quantitative model was developed to explain the kinetics of tetramethylammonium (TMA+) movement into and out of the goblet cavities of posterior midgut cells of Manduca sexta based on the data of the accompanying paper, which indicated that TMA+ does not enter the goblet cavity directly from the lumen. The model has two cellular compartments between the lumen and goblet cavity; these have been tentatively identified as the columnar cell and goblet cell cytoplasm. Five transmembrane pathways are included: from lumen to columnar cell, from columnar cell to goblet cell, from goblet cell cytoplasm to goblet cell cavity, and across the basal membrane of each cell type. These pathways need not be channels; they could use endocytotic or exocytotic mechanisms or, in the case of the cell-to-cell passage, septate junctions. However, in all cases, transfer is proportional to the electrochemical gradient. The model was tested against the results obtained after exposure to TMA+ in short-circuited and open-circuited tissues as well as results from an open-circuited tissue that did not develop a large transepithelial potential. Although driving forces for TMA+ across the membrane barriers were quite different in the different experimental conditions, the transfer coefficients from lumen to columnar cell, from columnar to goblet cell and from both cells across the basal membrane were the same. The only transfer coefficient that changed between short-circuit and open-circuit conditions was that from goblet cell cytoplasm to goblet cavity. This value was high under short-circuit conditions (when K+ transport activity is high), but low under open-circuit conditions (when K+ transport activity is low). The model suggests a hypothesis in which TMA+ enters the goblet cavity by an indirect route across the cell membrane of columnar cells, and thence passes to the goblet cell cytoplasm through intercellular junctions. Results from experiments with cytochalasin E suggest that the actin-based cytoskeleton is involved in limiting cell­cell coupling. In this model, TMA+ passes from the goblet cell cytoplasm to the goblet cavity via the K+/nH+ antiport believed to mediate active transepithelial K+ transport. However, although actively transported K+ is believed to pass from goblet cavity to lumen, TMA+ cannot.

Journal Article↗
PubMed1995

[50-year-old patient with dyspnea, dizziness, palpitations and brief sensory aphasia].

After a syncope, a 50 years old female patient was administered with an incomplete central facial paralysis on the left side combined with dyspnea, tachycardia, and hypotension as well as a systolic nurmur over the tricuspid valve. One week before, a vein stripping of the left long saphenous vein had been undertaken. By doppler-ultrasound, a thrombosis of the left tibial veins could be found as the cause of the pulmonary embolism. Additionally, the echocardiogram showed a relative tricuspid insufficiency and a floating atrial septum combined with an enlarged right atrium as an expression of the pulmonary hypertension. The incomplete central facial paralysis must be due to a paradox embolism in the cerebrovascular circulation as a result of an open foramen ovale. Under a therapy with high-dose heparin, all findings receded totally within one week.

Aphasia, Wernicke↗
PubMed1994

Titin, myosin light chains and C-protein in the developing and failing human heart.

We investigated relative amounts of titin, myosin light chains (MLC), C-protein, and myosin heavy chains (MHC) in the functionally intact contractile apparatus of embryonic, adult normal, and adult failing human left ventricle by SDS polyacrylamide gel electrophoresis and Western blot analysis. The amount of titin and the titin-MHC ratio was significantly (P < 0.05) lower in the embryonic and adult failing human compared to the adult normal fibres. Additionally, we found a protein band having a lower molecular weight but the same immunoreactivity as native titin (fast-migrating titin; FM-titin) in the failing heart only. The MLC-1/MLC-2 ratio was about 1.0 in normal and failing hearts but about 2.0 in the embryonic heart. Relative amount of C-protein was the same in normal and failing fibres but lower in the embryonic ventricles. Length-tension ratio of chemically skinned fibres prepared from terminally failing hearts was impaired compared to normal heart fibres. We conclude that both the reduced titin/MHC ratio and the expression of a structurally different titin form may be involved in the impaired contractile function of the terminally failing human heart.

Carrier Proteins↗
PubMed1994

[Effect of sedation on otoacoustic emissions].

Even though the measurement of transitory evoked otoacoustic emissions (TEOAE) is easy and without problems in babies, sedation might be necessary in children aged between 1 and 4 years. As only very little information is available on the influence of a sedation on the TEOAE, the present study was performed. 35 normal hearing patients who were treated with benzodiazepines as a premedication for an operation were included in the investigation. 15 patients received diazepam and 20 were given flunitrazepam in a dosage of 10 and 1 mg respectively. The TEOAE were measured using the ILO 88 system by Bray and Kemp 1 day before, 1 hour after and 3 days after drug intake. 10 additional subjects of whom measurements were taken at the same time intervals served as controls. No statistically significant changes could be detected before and after drug treatment in respect of amplitudes of the TEOAE and frequency of maximum amplitudes. Hence, we conclude that sedation as used in this study must be considered negligible when measuring TEOAE.

Acoustic Stimulation↗
PubMed1994

Biventricular thrombi in dilated cardiomyopathy: massive simultaneous pulmonary and systemic embolisation.

A patient with biventricular thrombus formation in dilated cardiomyopathy suffered massive combined systemic and pulmonary embolization shortly after oral anticoagulation was started. Although this can be coincidental, it can also suggest that the basis of a thrombus may dissolve first with any, including oral, anticoagulation. In unusual conditions surgical removal of thrombi in dilated cardiomyopathy may be a safer alternative.

Adult↗
PubMed1994

[Specific parent training in alalia. 1: Introduction and presentation of the seminar concept].

Developmental aphasia is the most severe form of speech retardation and needs therapeutic intervention. The young age of these children (< 3 years) makes therapy difficult. A specified speech therapy is not possible at this age. Intensive stimulation of verbal communication by the parents is necessary. Therefore we developed a specialized training program for parents. This preparation is very useful for later therapy and should prevent disturbance of interaction between parents and child. We will present our concept.

Aphasia↗
PubMed1994

[Specific parent training in alalia. 2: Study of experiences of parents in the seminar].

Specified training for parents of children with developmental aphasia has been offered for several years. We want to guide the parents to a controlled stimulation of speech at home. We asked the former participants about their experiences with this training program. We also studied the realization of the program by parents in everyday life before their children started therapy. The experiences were mainly considered positive, realizing the program did not present difficulties.

Aphasia↗
PubMed1994

The failing human heart is unable to use the Frank-Starling mechanism.

There is evidence that the failing human left ventricle in vivo subjected to additional preload is unable to use the Frank-Starling mechanism. The present study compared the force-tension relation in human nonfailing and terminally failing (heart transplants required because of dilated cardiomyopathy) myocardium. Isometric force of contraction of electrically driven left ventricular papillary muscle strips was studied under various preload conditions (2 to 20 mN). To investigate the influence of inotropic stimulation, the force-tension relation was studied in the presence of the cardiac glycoside ouabain. In skinned-fiber preparations of the left ventricle, developed tension was measured after stretching the preparations to 150% of the resting length. To evaluate the length-dependent activation of cardiac myofibrils by Ca2+ in failing and nonfailing myocardium, the tension-Ca2+ relations were also measured. After an increase of preload, the force of contraction gradually increased in nonfailing myocardium but was unchanged in failing myocardium. There were no differences in resting tension, muscle length, or cross-sectional area of the muscles between both groups. Pretreatment with ouabain (0.02 mumol/L) restored the force-tension relation in failing myocardium and preserved the force-tension relation in nonfailing tissue. In skinned-fiber preparations of the same hearts, developed tension increased significantly after stretching only in preparations from nonfailing but not from failing myocardium. The Ca2+ sensitivity of skinned fibers was significantly higher in failing myocardium (EC50, 1.0; 95% confidence limit, 0.88 to 1.21 mumol/L) compared with nonfailing myocardium (EC50, 1.7; 95% confidence limit, 1.55 to 1.86 mumol/L). After increasing the fiber length by stretching, a significant increase in the sensitivity of the myofibrils to Ca2+ was observed in nonfailing but not in failing myocardium. These experiments provide evidence for an impaired force-tension relation in failing human myocardium. On the subcellular level, this phenomenon might be explained by a failure of the myofibrils to increase the Ca2+ sensitivity after an increase of the sarcomere length.

Calcium↗