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Biomedical subjects

G Koch

Publications and source records attributed to G Koch.

At least 109 records · Page 6Linked to original sources
PubMed1997

Effects of long-term infusion of prostacyclin (epoprostenol) on echocardiographic measures of right ventricular structure and function in primary pulmonary hypertension. Primary Pulmonary Hypertension Study Group.

BACKGROUND: Right heart failure is an important cause of morbidity and mortality in primary pulmonary hypertension. In a recent prospective, randomized study of severely symptomatic patients, treatment with prostacyclin (epoprostenol) produced improvements in hemodynamics, quality of life, and survival. This article describes the echocardiographic characteristics of participants in this trial; the relationship of echocardiographic variables to hemodynamic parameters, exercise capacity, and quality of life; and the echocardiographic changes associated with prostacyclin therapy. METHODS AND RESULTS: The 81 patients enrolled in this multicenter trial were randomized to treatment with a long-term infusion of prostacyclin in addition to conventional therapy (n = 41) or conventional therapy alone (n = 40) for 12 weeks. Echocardiograms and assessments of hemodynamics, exercise capacity, and quality of life were performed before and after the treatment phase. On baseline evaluation, patients had marked right ventricular dilatation and dysfunction, abnormal septal curvature, and significant tricuspid regurgitation with a high regurgitant velocity. Pericardial effusions were common. More pronounced abnormalities in right heart structure and function were associated with higher pulmonary arterial and mean right atrial pressures, lower cardiac index, and impaired exercise capacity but had no predictable relationship to quality-of-life indicators. The 12-week infusion of prostacyclin had beneficial effects on right ventricular size, curvature of the interventricular septum, and maximal tricuspid regurgitant jet velocity. CONCLUSIONS: The echocardiographic manifestations of severe primary pulmonary hypertension reflect abnormalities in hemodynamics and exercise capacity. Prostacyclin has beneficial effects on right heart structure and function that may contribute to the clinical improvement and prolonged survival observed with this drug.

Adult↗
PubMed1997

Milk protein-derived opioid receptor ligands.

Milk is mammalian characteristic and is of particular importance for humans: Mother's milk or its substitutes from cows' milk are absolutely essential nutriments for the neonate and cows' milk also represents a basic foodstuff for adults. However, in addition to their well-known nutritive role, milk constituents apparently are also able to carry specific information from the milk producer's to the milk receiver's organism: Thus, a number of milk protein fragments has been shown to behave like opioid receptor ligands able to address opioidergic systems in the adult's or in the neonate's organism. With respect to the proteins, which they are derived off these peptides have been named alpha-casein exorphins or casoxin D (alpha-casein), beta-casomorphins or beta-casorphin (beta-casein), casoxin or casoxin A, B, or C (k-casein), alpha-lactorphins (alpha-lactalbumin), beta-lactorphin (beta-lactoglobulin) or lactoferroxins (lactoferrin). Only casoxins and lactoferroxins display antagonistic properties; the other peptides behave like opioid receptor agonists. Most of the information available so far has been collected about beta-casomorphins. These peptides obviously can be released from beta-casein in the adult's or in the neonate's organism, where they might elicit opioid effects in the frame of a regulatory role as "food hormones". Several synthetic beta-casomorphin derivatives have been shown to be highly specific and potent mu-type opioid receptor ligands which frequently have been used as standard tools in opioid research.

Amino Acid Sequence↗
PubMed1997

Effects of Clostridium botulinum C2 toxin-induced depolymerisation of actin on degranulation of suspended and attached mast cells.

We studied the effects of C. botulinum C2 toxin, which ADP-ribosylates G-actin, on mast cell degranulation. C2 toxin inhibited degranulation of suspended rat peritoneal mast cells induced by compound 48/80 and dinitrophenyl-conjugated bovine serum albumin (DNP-BSA) maximally by about 50 and 90%, respectively. Inhibition by C2 toxin occurred in a time- and concentration-dependent manner. Half-maximal inhibition of DNP-BSA-induced degranulation by C2 toxin occurred at about 0.015 ng/ml, whereas stimulation of mast cells induced by compound 48/80 was half-maximally inhibited at 0.15 ng/ml C2 toxin. C2 toxin also inhibited stimulated [3H]serotonin release from suspended mast cells. Phorbol 12-myristate 13-acetate (PMA)-induced histamine release of suspended mast cells was inhibited by C2 toxin by about 80-90%. C2 toxin had no effect on calcium ionophore A23187-induced histamine release. Toxin treatment of mast cells caused ADP-ribosylation of actin and depolymerisation of F-actin. Attachment of mast cells, which largely increased the diameter of the subcortical actin network, reduced degranulation stimulated by compound 48/80, antigen and calcium ionophore but not by PMA. Opposite to its effect on suspended cells, in adherent mast cells C2 toxin stimulated degranulation by compound 48/80, antigen, and calcium ionophore but not by PMA. The data indicate that mast cell degranulation and responsiveness towards the actin-depolymerising C2 toxin depend largely on mast cell attachment.

Actins↗
PubMed1997

Effects of Clostridium difficile toxin B on activation of rat peritoneal mast cells.

Clostridium difficile toxin B that inactivates Rho subfamily proteins by glucosylation, inhibited dinitrophenyl-conjugated bovine serum albumin (DNP-BSA) and phorbol 12-myristate 13-acetate (PMA)-induced mast cell activation by 80 to 90% in a concentration- and time dependent manner with a delay of about 30 min. Activation of mast cells by compound 48/80 and calcium ionophore A23187 was maximally inhibited by about 50%. Inhibition by toxin B was observed with suspended, attached and permeabilised mast cells. C3 ADP-ribosyltransferase, which selectively inactivates RhoA,B,C subtype proteins inhibited antigen, compound 48/80, PMA, A23187 and GTP[S]-induced degranulation of permeabilised mast cells C3-induced inhibition of stimulated histamine release was smaller than that observed with toxin B and both inhibitory effects were not additive. These findings suggest the involvement of Rho subtype GTPases and additionally, of other members of the Rho subfamily GTPases in activation of rat peritoneal mast cells.

Animals↗
PubMed1997

[Vascular lesions in surgery of the hip joint].

The vascular anatomy in the acetabular region involves a certain risk of arterial and venous injuries complicating orthopaedic surgery. These complications have been grouped into four categories: lacerations, thrombosis, pseudoaneurysms and arteriovenous fistula. In a period of 5 years, three injuries of the external iliac artery and four lesions of the femoral artery associated with total hip arthroplasty were treated surgically at the Department of Vascular Surgery of the University Hospital in Graz. In one case a concomitant lesion of the pelvic vein was observed. The incidence of iatrogenic vascular injuries in total hip surgery is 0.3%. Combined injury of the external iliac artery and vein led to a life-threatening bleeding complication. The vascular lesion became manifest as acute ischaemia of the lower extremity or as an acute haemorrhage 30 min to 2 h after primary surgery. The late complication of a false aneurysm of the femoral artery occurred in one patient 3 weeks after total hip replacement. Reconstruction of the vascular lesions was performed by direct suture, except that two arterial lesions required the use of polytetrafluoroethylene (PTFE) vascular grafts. Vessels in the pelvic region are at high risk if screw fixation acetabular components are used. Perforation of the iliac artery by protruded methylmethacrylate polymer components of cement has been documented. The obturator vessels are in a vulnerable position if the acetabular floor has been broached by operative instruments or eroded by loosening of the prosthesis facilitated by osteoporosis, steroids or sepsis. Femoral vessels are endangered by Hohmann retractors that are not placed directly on bone. Though vascular injury during hip operations is rare, recognition of such complications is important as safe and satisfactory treatment can be achieved. Rapid identification and immediate surgical repair of these lacerations are essential for their management.

Aged↗
PubMed1997

Effect of intensive swimming training on lung volumes, airway resistance and on the maximal expiratory flow-volume relationship in prepubertal girls.

The aim of the present study was to analyse the effect of 1 year of intensive swimming training on lung volumes, airway resistance and on the flow-volume relationship in prepubertal girls. Five girls [9.3 (0.5) years old] performing vigorous swimming training for 12 h a week were compared with a control group of 11 girls [9.3 (0.5) years old] who participated in various sport activities for 2 h per week. Static lung volumes, maximal expiratory flows (MEF) at 75, 50 and 25% of vital capacity, 1-s forced expiratory volume (FEV1.0) and airway resistance (R(aw)) were measured by means of conventional body plethysmograph techniques. Prior to the training period there were no significant differences between the two groups for any of the parameters studied. Moreover, for both groups, all parameters were within the normal range for children of the corresponding age. After 1 year of training, vital capacity (VC), total lung capacity (TLC) and functional residual capacity (FRC) were larger (P < 0.05) in the girl swimmers than in the control group, while physical development in terms of height and weight was similar. FEV1.0 (P < 0.01), MEF25, MEF50 (P < 0.05) and MEF75 as well as the ratio MEF50/TLC (P < 0.05) had increased in the girl swimmers but were unchanged in the control group. R(aw) tended to be lower in the girl swimmers and higher in the control group. The results indicate that intensive swimming training prepuberty enhances static and dynamic lung volumes and improves the conductive properties of both the large and the small airways. As to the causative mechanism, it can be speculated that at prepuberty intensive swimming training promotes isotropic lung growth by harmonizing the development of the airways and of alveolar lung spaces.

Airway Resistance↗
PubMed1997

The effect of early intervention on skeletal pattern in Class II malocclusion: a randomized clinical trial.

Early treatment for Class II malocclusion is frequently undertaken with the objective of correcting skeletal disproportion by altering the growth pattern. Because the majority of previous studies of growth modification for Class II malocclusion have been based on retrospective record reviews, the efficacy of such an approach has not been well established. In this controlled clinical trial, patients in the mixed dentition with overjet > or = 7 mm were randomly assigned to either early treatment with headgear, or modified bionator, or to observation. All patients were observed for 15 months with no other appliances used during this phase of the trial. The three groups, who were equivalent initially, experienced statistically significant differences (p < 0.01) in skeletal change. There was considerable variation in the pattern of change within all three groups, with about 80% of the treated children responding favorably. Although patients in both early treatment groups had approximately the same reduction in Class II severity, as reflected by change in the ANB angle, the mechanism of this change was different. The headgear group showed restricted forward movement of the maxilla, and the functional appliance group showed a greater increase in mandibular length. The permanence of these skeletal changes and their impact on the subsequent treatment remains to be evaluated.

Analysis of Variance↗
PubMed1997

Demographics, health behaviors, and past drug use as predictors of recall accuracy for previous prescription medication use.

Drug data for pharmacoepidemiologic studies are often ascertained by self-report, but little research has addressed the factors influencing its accuracy. Stratified random sampling was used to select individuals for a study comparing interview data on past prescription drug use with dispensation information from the Group Health Cooperative of Puget Sound pharmacy database. The strata included age, gender, and recency of use. Recall accuracy and its determinants were evaluated for repetitively used non-steroidal anti-inflammatory drugs (NSAIDs), short-term NSAIDs (only a single dispensation), and post-menopausal estrogens. We investigated whether recall accuracy was influenced by education, marital status, race, smoking, alcohol consumption, cumulative drug history, the number of different NSAIDs or estrogens dispensed (both by name and dosage), and the number of dispensations of the drug in question. For repetitively used NSAIDs, recall accuracy was positively associated with the number of NSAID dispensations (the odds of recall were 1.7 [95% confidence interval {CL}: 1.3-2.2] times greater for each additional four dispensations of the NSAID), the total number of drugs dispensed and the number of different NSAIDs dispensed. For estrogen and short-term NSAID use, only higher educational attainment improved recall accuracy: the odds of recall were 4.1 (95% CI: 1.4-11.7) and 2.1 (95% CI: 1.0-4.7) times greater for those with some college compared with those with only a high school degree, respectively. This study demonstrates that predictors of recall accuracy for previous medication use differ by the type of drug and the repetitiveness of its use.

Aged↗
PubMed1997

[Isolated pelvic vein thrombosis in a young marathon runner].

The case of a 20-year old female patient who developed an isolated thrombosis of the pelvic vein after a marathon run, is presented. After surgical treatment and anticoagulation for one year, complete restitution was seen. The possible relation between marathon running and venous thrombosis without other risk factors is discussed.

Adult↗
PubMed1997

Glass ionomer materials as a rechargeable fluoride-release system.

It is well established that glass ionomers (GI) release fluoride (F). The degree of F released depends on the physical and chemical properties of the product. In the present study the fluoride release and the capacity of the GI to be recharged with fluoride was tested for five different brands: XR Ionomer (Kerr), Vitrebond (3M), GC Fuji Lining (G.C. Dental Industries Corp.), Baseline VLC (Dentsply) and Zinomer (Dent. Mat.). Fifteen test specimens were prepared for each brand. The specimens were immersed in deionized water. The F released was measured once a day for 11 days. Refluoridation of the test specimens was done with solutions of 0.02%, 0.04% and 0.2% NaF for 5 minutes on days 11, 16, 21 and 26. The F released from recharged specimens was measured daily until day 32. There was a positive correlation between the amount of F in the GI and the ability to release F. The five materials became 'recharged' with F following repeated F exposure in solution, the 0.2% solution being the most effective. XR ionomer released significantly more fluoride than any other material and showed the greatest ability to be recharged. Zinomer released significantly less fluoride than any other material and showed the least ability to be recharged. The present results indicate that GI serves as a F reservoir and can act as a prolonged slow-release system for at least 32 days.

Absorption↗
PubMed1997

Analysis of 274 Omniflow Vascular Prostheses implanted over an eight-year period.

BACKGROUND: Polytetrafluoroethylene (PTFE), dacron, and, more recently, collagen prostheses are finding increasing use for femoropopliteal reconstruction when a suitable vein is not available. The main factors to be considered when choosing a prosthesis are patency, susceptibility to infection and formation of aneurysms. METHODS: Sheep collagen prostheses were implanted on 274 occasions in the femoropopliteal or crural regions. RESULTS: The patency rate for supragenual bypass after 3 years was 61.9% with good vascular periphery and 44% with poor vascular periphery. If the prosthesis extended below the knee, the patency rate was 55.4% with good and 35.3% with unfavourable vascular periphery. Patency for the femorocrural bypass was 28.7% after 2 years. The rate of infection was 0% and an aneurysm occurred in three patients (1.1%). CONCLUSIONS: With this low infection rate and very slight danger of aneurysm, the long-term results suggest that the ovine collagen prosthesis can be recommended for use when no suitable vein is available.

Adult↗
PubMed1997

Transcription termination factor Rho is essential for Micrococcus luteus.

The growth of Micrococcus luteus, a soil microorganism that belongs to the high-G+C gram-positive phylogenetic group, is prevented by bicyclomycin, an antibiotic that inhibits the activity of the M. luteus transcription termination factor Rho. A mutant that can grow in 0.3 mM bicyclomycin has a Rho that is insensitive to bicyclomycin and has the single amino acid residue change of Asp474 to Gly. These results indicate that the function of its Rho factor is essential for M. luteus and that growth of a gram-positive organism can be blocked by bicyclomycin.

Anti-Bacterial Agents↗
PubMed1997

Remineralization of natural carious lesions with a glass ionomer cement.

Remineralization of carious lesions at the histological level is of great benefit since this will arrest lesion progression. The ability of glass ionomer cement (GIC) to (1) release fluoride it originally contains and (2) release "loosely bound" fluoride acquired from its surroundings have been previously demonstrated. This in vitro study examined the potential for caries remineralization if the lesion was placed near a GIC. Sixteen mesiodistal sections were cut through extracted deciduous molars exhibiting approximal white spot lesions. Sections were "linked" to a plastic tooth restored with a GIC to simulate the abutting surfaces of adjacent teeth. Lesions were photographed in water under polarized light initially and after one- and two-week exposures to artificial saliva. The photographs were digitized, lesion body outlined, and the area corresponding to the body of the lesion was determined to provide a comparison over time. Sixty-two percent of the sections showed a quantitative reduction in lesion body size by an average of 43% after the first week and an additional 14% reduction after the second week. All but two sections demonstrated a qualitative change thereby illustrating that a reduction in pore volume size of the lesion body had also occurred. Therefore, fluoride released from a GIC has the potential to enhance remineralization of the early carious lesion in vitro. The greatest remineralization occurred during the first week of artificial saliva exposure.

Cariostatic Agents↗
PubMed1997

Vascular complications in minimally invasive surgery.

Injuries to major vessels in the course of laparoscopic surgery are rare but serious, life-threatening complications. We report nine iatrogenic vascular injuries during minimally invasive surgery that occurred between January 1991 and December 1995 in surgical and obstetric-gynecologic services in the Austrian province of Styria. The total vascular complication rate is 0.08%. As these data show, the distal abdominal aorta and vena cava, as well as the large pelvic vessels, are especially susceptible to injury when the Veress needle and trocars are inserted into the abdomen. Surgical reconstruction of these eight arterial lesions required a polytetrafluorethylene (PTFE) patch in one case, and the resection of the damaged section of the artery and reanastomosis in two others. The remaining lesions, as well as an isolated vein injury, were corrected with direct suturing of the vessel. Pelvic circulation was completely restored in all patients, and permanent damage was avoided.

Adult↗
PubMed1997

Role of Rho protein in lovastatin-induced breakdown of actin cytoskeleton.

The Rho GTPases are involved in actin cytoskeleton organization and signal transduction. They need polyisoprenylation for membrane association and activation. Lovastatin, a hydroxymethylglutaryl coenzyme A inhibitor, prevents isoprene synthesis and thereby lipid modification of the Rho protein carboxy terminus. Because lovastatin causes rounding up of cultured cells, we investigated whether the compound acts on the actin cytoskeleton through Rho proteins. Lovastatin treatment decreased F-actin content in a time- and concentration-dependent manner. G-actin content remained unchanged. In lovastatin-treated NIH 3T3 cells, the amount of Rho protein which was ADP-ribosylated by Clostridium botulinum exoenzyme C3 decreased in membranes and increased in the cytosol fraction. Cycloheximide prevented lovastatin-induced rounding up of cells. However, after microinjection or direct application of exoenzyme C3, cells treated with cycloheximide and lovastatin rounded up again. On the contrary, lovastatin-treated, round Swiss 3T3 cells reverted to a flat morphology when microinjected with dominant active RhoA (Val14RhoA). Escherichia coli cytotoxic necrotizing factor (CNF1) which activates Rho proteins caused flattening of round, lovastatin-treated NIH 3T3 cells. These results suggest that lovastatin affects the actin cytoskeleton through inactivation of Rho proteins.

3T3 Cells↗
PubMed1997

[A break or bend in the unreamed tibial intramedullary nail. Experimental study].

The intramedullary tibial nail with a proximal angle according to Herzog was developed in order to facilitate implantation. However, the modified technique of unreamed nailing also required a shift of the point of insertion; as a consequence the proximal angle required a considerable increase in the force necessary to introduce the nail. In a study using-four cadaver bones and five commercially available unreamed femoral and tibial nails, the authors demonstrate this considerable increase in insertion force and the development of pressure in the medullary cavity. The measurements made with our experimental setup clearly show that the proximal angle of the unreamed tibial nails available for our series does not have a favourable influence on insertion behaviour. As it appears, it results in an increase in the force required for insertion of the nail, thus also causing a greater strain on the bone and an increase in pressure in the medullary cavity. In contrast, the continuous bend of the nail results in a much smoother course of pressure development in the medullary cavity, which does not reach the same high values as with the unreamed tibial nails, despite the fact that less time is required for insertion of the nail. In our opinion, modification of the axial shape of the nail would result both in better implantability and easier removal. We therefore advocate such a modification of the axial shape of intramedullary tibia nails.

Biomechanical Phenomena↗
PubMed1997

[Contour of the lower lip after von Esmarch reconstruction of lower lip vermillion].

After vermilionectomy the defect is usually resurfaced by advancement of the undermined labial mucosa. This procedure was described first by von Esmarch and Kowalzik and not by von Langenbeck, to whom the method is frequently attributed. The aim of this study was to investigate the changes of the contour of the lower lip after this procedure. Thirty-three cases were studied. Pre- and post-operative lateral cephalograms were evaluated. The changes in length, thickness and profile of the lip were examined. All parameters showed only minor changes except a decrease in the visible vermilion height in all cases.

Cephalometry↗