Search PubMed⌕ Search

Biomedical subjects

A Koch

Publications and source records attributed to A Koch.

At least 235 records · Page 13Linked to original sources
PubMed1994

Tamm-Horsfall glycoprotein: role in inhibition and promotion of renal calcium oxalate stone formation studied with Fourier-transform infrared spectroscopy.

Tamm-Horsfall glycoprotein (THP) from healthy probands inhibits the precipitation of calcium oxalate, whereas THP from individuals who repeatedly develop calcium oxalate stones has no effect or even promotes precipitation. Using Fourier-transform infrared spectroscopy, we found a structural differentiation between these functionally different THPs: a decisive difference in sialic acid content. Quantitative analysis for sialic acid showed the same results. THP from healthy probands had a high sialic acid content (51 +/- 9 g/kg), whereas THP from recurrent stone formers had a decreased sialic acid content (21 +/- 4 g/kg). This explains the dual role of THP in the precipitation of calcium oxalate and the formation of renal stones and shows the importance of glycosylation in the function of this glycoprotein.

Calcium Oxalate↗
PubMed1994

Inotropic effect of the cardioprotective agent 2,3-butanedione monoxime in failing and nonfailing human myocardium.

The drug 2,3-butanedione monoxime (BDM) was suggested to be a potent cardioprotective agent useful for cardiopreservation. The present study investigated the activity of BDM and its mechanism of action in human myocardium. In electrically driven left ventricular papillary muscle strips and right atrial trabeculae from failing (heart transplants) and nonfailing (donor hearts) human myocardium, isometric force development and the force-frequency relationship were examined. To study the sarcolemmal actions of BDM, competition experiments with 125I-iodocyanopindolol, 3H-ouabain and 3H(+)PN 200-110 were performed. The effect of BDM on the contractile apparatus was tested by investigating its effects on Ca++ sensitivity and on the relaxation parameters of skinned fiber preparations. In papillary muscle strips and in atrial trabeculae, BDM (0.001-30 mM) depressed the isometric force of contraction in a concentration-dependent manner. BDM was more potent in atrial than in ventricular tissue and it shifted the Ca++ concentration-response curve in atrial and ventricular tissue to the right. The potency of BDM to depress force development was significantly lower compared with the L type of Ca++ channel antagonist nifedipine in both atrial and ventricular myocardium. In the presence of 10 mM BDM, the force-frequency relationship becomes positive in failing myocardium but not in the presence of 1 mM BDM, which did not affect the specific binding of 125I-iodocyanopindolol, 3H-ouabain or 3H(+)PN 200-110. This indicated there was no action on beta adrenoceptors, cardiac glycoside receptors and dihydropyridine-type Ca++ channels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Force-frequency-relation in human atrial and ventricular myocardium.

In human heart failure, an increase in frequency of stimulation is followed by a reduced force of contraction in vivo and in vitro. The present study aimed to investigate whether a different origin of the myocardial sample or pretreatment with the cardioprotective agent 2,3-butanedione-monoxime (BDM) influences the force-frequency-relationship in electrically driven muscle strips taken from failing and nonfailing human myocardium. With as well as without pretreatment with BDM, the altered force-frequency-relationship in failing compared to nonfailing human ventricular myocardium can be observed. The effectiveness and the potency to increase force of contraction following an increase in frequency of stimulation was significantly higher in atrial than in ventricular myocardium in nonfailing and failing tissue. The different observations in atrial and ventricular myocardium provide evidence for functionally relevant differences in the electromechanical coupling between the human atrial and ventricular myocardium.

Adult↗
PubMed1993

Cloning, sequencing, and heterologous expression of a cellulase-encoding cDNA (cbh1) from Penicillium janthinellum.

From a Penicillium janthinellum cDNA library, two clones with 1.8- and 1.9-kb inserts were isolated by hybridization to a Trichoderma reesei cellulase-encoding gene probe (egl1). Both cDNAs have identical 5' ends and coding sequences, but different polyadenylation start points in their 3' untranslated regions. In the nucleotide (nt) sequence, one open reading frame of 537 amino acids was detected which shows 56% homology with endoglucanase I of T. reesei and 70% homology with cellobiohydrolase I of T. reesei, Phanerochaete chrysosporium, and Humicola grisea. Expression of the 1.9-kb cDNA in the Escherichia coli T7 system led to the detection of a 57-kDa protein, in agreement with the theoretical value. Fusion to the promoter of the yeast phosphoglycerokinase-encoding gene led to efficient expression and partial secretion of the cDNA-encoded cellulase with cellobiohydrolase I activity in Saccharomyces cerevisiae.

Agaricales↗
PubMed1993

[Comparative studies of the ototoxicity of cisplatin and carboplatin].

The application of the potent anticancer drug cisplatin is limited by major side effects such as its ototoxicity and its nephrotoxicity. Since carboplatin has been introduced into clinical use, a platinum derivative with less pronounced ototoxicity and nephrotoxicity is available. The aim of this study was to quantify the ototoxicity of carboplatin comparing it to cisplatin using the wellknown guinea-pig model. Using morphological and functional methods it could be shown that the ototoxic damage was by far higher in a group which had received a total dose of 12 kg cisplatin/kg than in a group which had received a dosage of 90 mg carboplat/kg. Our investigations show that the ototoxic potential of cisplatin in the guinea-pig is more than 9 times higher than that of carboplatin.

Animals↗
PubMed1993

[Symmetry of the human midface].

A new measuring instrument called "zygometer" is introduced. This device provides a simple technique for measuring the position of the zygomatic bone and arch allowing for lateral comparison. Standard measurements of the midface were collected from 250 uninjured test subjects. In 80% of the cases a symmetry of up to 2 mm was determined. The research results are presented and discussed with reference to clinical application.

Animals↗
PubMed1993

Measurement of the midface symmetry in trauma and reconstructive surgery.

The pre- and intraoperative determination of the midface symmetry during the management of trauma or reconstructive surgery cases may be difficult due to swelling of the covering tissue. To handle these problems, a new apparatus, called "Zygometer", is introduced. This instrument is able to measure the position of the midface bones and enables a comparison with the controlateral side. The results of a study with 250 persons to get standard measurements for symmetry and asymmetry are presented and discussed. Indications and clinical application of the zygometer are demonstrated.

Adult↗
PubMed1992

Two signals are involved in polyclonal B cell stimulation by T helper type 2 cells: a role for LFA-1 molecules and interleukin 4.

T helper cell type 2 (Th2) cells when triggered by antibodies to CD3 acquire the capacity to stimulate the polyclonal proliferation of syngeneic, resting B cells. Here, we tested the ability of various monoclonal antibodies (mAb) to block the B cell proliferation-inducing potential of such activated Th2 cells. We demonstrate that anti-interleukin 4, as well as anti-LFA-1 antibodies interfere with the T-B cell interaction. In kinetic studies, anti-LFA-1 was found to be operative during the first half and anti-interleukin 4 during the second half of the 48-h culture period. This defines at least two different steps in B cell triggering by Th2 cells. In addition, the data imply that the T-B cell interaction involves an additional structure, namely an activation molecule, on the T cell surface.

Animals↗
PubMed1992

Driving forces and pathways for H+ and K+ transport in insect midgut goblet cells.

In the midgut of larval lepidopteran insects, goblet cells are believed to secrete K+; the proposed mechanism involves an electrogenic K+/nH+ (n > 1) antiporter coupled to primary active transport of H+ by a vacuolar-type ATPase. Goblet cells have a prominent apical cavity isolated from the gut lumen by a valve-like structure. Using H(+)- and K(+)-selective microelectrodes, we showed that electrochemical gradients of H+ and K+ across the apical membrane and valve are consistent with active secretion of both ions into the cavity and that the transapical H+ electrochemical gradient, but not the transapical pH gradient, is competent to drive K+ secretion by a K+/nH+ antiporter. We used 10 mmol l-1 tetramethylammonium ion (TMA+) as a marker for the ability of small cations to pass from the gut lumen through the valve to the goblet cavity, exploiting the high TMA+ sensitivity of 'K(+)-sensitive' microelectrodes. These studies showed that more than half of the cavities were inaccessible to TMA+. For those cavities that were accessible to TMA+, both entry and exit rates were too slow to be consistent with direct entry through the valves. One or more mixing compartments appear to lie between the lumen bathing solution and the goblet cavity. The lateral intercellular spaces and goblet cell cytoplasm are the most likely compartments. The results are not consistent with free diffusion of ions in a macroscopic valve passage; mechanisms that would allow K+ secreted into the goblet cavity to exit to the gut lumen, while preventing H+ from exiting, remain unclear.

Animals↗
PubMed1992

[Bone-anchored epitheses and audioprostheses: 4 years' experience with the Branemark system in Germany].

Osseointegration describes direct contact between titanium and vital bone. The Branemark System uses this principle for bone anchorage of hearing aids and craniofacial prostheses. The experience made in the ENT Department of the University Hospital in Homburg/Germany with this procedure in the last 4 years is described. During this period, 40 patients have been operated and 119 titanium fixtures have been implanted. 30 patients got bone anchored prostheses (ear, nose or orbit) and 25 patients received bone anchored hearing aids. The large group of 15 patients with congenital ear malformation presented both indications. 100 out of 119 implants i.e. 84% caused no major problems. The most frequent complications were granulations (10 implants i.e., 8.4%). More severe problems as non-integration of three pillars or rejection of one pillar were rare. Our experience for 4 years in an important number of patients was very positive in the majority of cases and allows us to consider the bone anchorage of hearing aids and craniofacial prostheses as a major advance in craniofacial rehabilitation and audiology.

Aged↗
PubMed1992

Increase of the extracellular magnesium concentration reduces cardiac glycoside toxicity in the human myocardium.

We studied the influence of magnesium on contractility and on force-frequency-relationship as well as on the positive inotropic and toxic effects of ouabain (OUA) on electrically driven human right auricular trabeculae. Radioligand binding experiments were performed with myocardial tissue from nonfailing and from terminally failing patients. Magnesium produced a concentration-dependent negative inotropic effect (P < .05). In contrast, OUA (0.03-0.1 mumol/l) concentration-dependently increased isometric force of contraction. The maximal positive inotropic effect of OUA (5.9 +/- 0.9 mN; 1 mmol/l of magnesium) was unchanged after increasing magnesium from 1 to 2 mmol/l (5.8 +/- 0.9 mN). OUA was as effective as Ca++ (15 mmol/l; 6.7 +/- 0.5 mN). OUA (0.05 and 0.03 mumol/l) exerted toxic effects after 2 hr and 0.08 or 0.1 mumol/l of OUA after 30 min, respectively. Time until toxic effects occurred after OUA (0.1 mumol/l) was significantly longer with 2 mmol/l of magnesium compared to 1 mmol/l of magnesium. In right auricular trabeculae, the force of contraction increased with increasing frequency (0.5-1 .5 Hz) of stimulation. The force-frequency-relationship becomes negative after elevation of extracellular Ca++ (2.4 mmol/l of Ca++) (2 Hz: 92 +/- 5.5% basal). Magnesium restored the force-frequency-relationship in the presence of enhanced Ca++ concentration (2.4 mmol/l of Ca++; 2 mmol/l of Mg++; 2 Hz: 145 +/- 16.9% basal). The receptor-density and affinity measured by [3H]OUA binding was not different in nonfailing and failing myocardium. Magnesium increased concentration-dependently the affinity of [3H]OUA to its receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Non-attendance of psychiatric outpatients.

The failure of discharged psychiatric inpatients to attend for continuing outpatient treatment is an important factor in readmission. A study of 136 such patients indicates that frank resistance to treatment and inadequate information given to patients and their families are important contributing factors. A recommendation for improving the situation is made.

Adult↗
PubMed1991

Psychological distress and depression in urbanising elderly black persons.

The findings of a comparative community survey of the socioeconomic, cultural and psychiatric state of elderly black persons in a newly settled township (Khayelitsha--170 persons) and a long established one (Langa--195 persons) revealed marked differences. Symptoms of psychological distress, depression and limitation of daily activities were generally more marked in the former and strikingly so among women: 66% had symptoms warranting further investigation and 44% would have been treated for a depressive disorder if seen by a psychiatrist. Extreme poverty existed in both townships but the Khayelitsha subjects were less well educated, their accommodation was poorer, and fewer had old-age pensions. Elderly black women in newly settled townships have therefore been identified as having high priority for psychiatric and social services.

Activities of Daily Living↗