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Biomedical subjects

W Krause

Publications and source records attributed to W Krause.

At least 91 records · Page 5Linked to original sources
PubMed1998

[Effects of varicocele therapy on spermatozoan function].

Men suffering from varicocele have lower mean sperm counts and "worse" seminal parameters than those without a varicocele. Also in those with a varicocele, who already fathered a child, the mean sperm count is lower than in other fertile men. The observations, however, do not refer specifically to an existing varicocele, but are common also in other spermatogenic defects. This holds also true for the frequency of tapering forms. Besides the classical parameters of the spermatozoa also novel parameters of the extended semen analysis were tested. As well in the rate of acrosome-reacting spermatozoa, in the rate of anilinblue stained cells, in the number of zona binding-spermatozoa as in the concentration of sperm antibodies no differences between men with and men without a varicocele were found. The grade of a varicocele does not account for the degree of the spermatogenic defect. The progressive damage to the spermatogenesis by an persisting varicocele is discussed controversely. It was suggested that an early treatment of a varicocele, in particular in the adolescence, might inhibit the later insufficiency of sperm production. Correction of a varicocele is followed by an improvement of seminal parameters, in particular of sperm motility. In controlled studies, however, this effect was also observed in the untreated group. This casts some doubt on the causative effect of the varicocele treatment. The improvement of seminal parameters is not always accompanied by an increase in fertility, although also some functional parameters showed an improvement after correction of the varicocele.

Adolescent↗
PubMed1998

The haemodynamic effects of iodinated water soluble radiographic contrast media: a review.

All classes of iodinated water-soluble radiographic contrast media (RCM) are vasoactive with the iso-osmolar dimers inducing the least changes in the vascular tone. The mechanisms responsible for RCM-induced changes in the vascular tone are not fully understood and could be multifactorial. A direct effect on the vascular smooth muscle cells causing alterations in the ion exchanges across the cell membrane is thought to be an important factor in RCM-induced vasodilatation. The release of the endogenous vasoactive mediators adenosine and endothelin may also play a crucial role in the haemodynamic effects of RCM particularly in the kidney. In addition, the effects of RCM on blood rheology can cause a reduction in the blood flow in the microcirculation. The purpose of this review is to discuss the pathophysiology of the haemodynamic effects of RCM and to offer some insight into the biology of the endothelium and vascular smooth muscle cells as well as the pharmacology of the important vasoactive mediators endothelin and adenosine.

Adenosine↗
PubMed1997

Substance P and epibatidine-evoked catecholamine release from fractionated chromaffin cells.

Bovine chromaffin cells were separated by density gradient centrifugation into subfractions enriched with either > 90% adrenaline- or 70-80% noradrenaline-producing cells. Concentrations of epibatidine (an alkaloid with nicotinic receptor activity) as low as 10 nM released adrenaline and noradrenaline from both fractions of cells maintained as monolayer cultures. The maximal effect was evoked by 30 nM epibatidine and was comparable to that evoked by 10 microM nicotine. The catecholamine release from the noradrenaline fraction was 30-40% higher than from the adrenaline fraction. Initial exposure to 50 nM epibatidine reduced release induced by a second exposure to the drug. There was cross-desensitization between epibatidine and nicotine. Substance P inhibited the epibatidine-evoked catecholamine release from both fractions by up to 85% (IC50 = 3-5 microM). The release of noradrenaline was inhibited more than that of adrenaline. In addition, substance P protected the chromaffin cells against desensitization of the nicotinic receptor by epibatidine. The C-terminal heptapeptide sequence of substance P was 10 x less active, two N-terminal sequences did not modulate the catecholamine release.

Adrenal Medulla↗
PubMed1997

Influence of fibronectin on the motility of human spermatozoa.

The objective of the present study was to scrutinize the concentration of seminal fibronectin and the potential effects of exogenous fibronectin on human sperm motility. In addition, variability in the localization of fibronectin on human spermatozoa from andrological patients was studied, at both the light and electron microscopic levels. A total of 58 freshly ejaculated semen samples from patients attending for infertility treatment were submitted to sperm motility analysis and ELISA quantification of seminal plasma and cell-bound fibronectin. Immunofluorescence and immunoelectron microscopy revealed a relatively broad distribution pattern of fibronectin immunoreactivity on sperm heads and testicular spermatids. Addition of a fibronectin antiserum to vital spermatozoa in vitro at a moderate dilution (1:50) resulted in a significant increase in sperm motility. Purified plasma fibronectin, added at various concentrations to a preparation of live spermatozoa, was found to inhibit sperm motility in a dose-dependent manner. At concentrations from 0.18 to 0.5 mg fibronectin per ml ejaculate, no motile spermatozoa were recorded. Seminal plasma fibronectin ranged between 0.8 and 1000 micrograms/ml in infertility patients. There was a significant inverse correlation between sperm motility and seminal fibronectin in patients with oligo-astheno-teratozoospermia. In a preliminary study in patients with varicocele or hypogonadism, no such correlation was found.

Blotting, Western↗
PubMed1997

Analyses of meiotic chromosomes in testicular biopsies of infertile patients.

Between 1989 and 1992 meiotic chromosome studies and synaptonemal complex analyses were evaluated using light and, in part, electron microscopy in 46 infertile males with highly abnormal spermiograms. This examination focused on whether the breakdown of spermatogenesis could be attributed to pairing anomalies of bivalents. The study of meiotic chromosomes and synaptonemal complexes indicated normal spermatogenesis in five patients (11%); in the remainder, maturation arrest was diagnosed. In 21 individuals (50%) the breakdown was accompanied by pairing anomalies (asynapsis, fragmented synaptonemal complexes, X/Y univalence). Thus it is shown that male infertility can often partly be explained by meiotic disorders.

Atrophy↗
PubMed1997

Biodistribution and computed tomography blood-pool imaging properties of polyethylene glycol-coated iopromide-carrying liposomes.

RATIONALE AND OBJECTIVES: Surface-modified contrast-carrying liposomes potentially are useful as computed tomography (CT) blood-pool agents. The biodistribution and CT-imaging behavior of conventional as well as polyethylene glycol (PEG)-coated iopromide-carrying liposomes were tested. Two different types of PEG-ylated lipids were used to demonstrate possible differences. METHODS: Iopromide-containing liposomes were prepared by a continuous high-pressure extrusion method and subsequently PEG-ylated by simple mixing with either DSPE-PEG2000 or CHHS-PEG2000. The resulting liposomes were investigated in rats (biodistribution) and rabbits (imaging). RESULTS: Surface modification with CHHS-PEG consistently resulted in less effective stabilization of liposomes in the blood than with DSPE-PEG. In the biodistribution study, no significant differences in blood concentration could be found 1 hour after injection between the different formulations at a dose of 250 mg total iodine/kg body weight (approximately 500 mg lipid/kg). At this dose, the unmodified as well as the DSPE-PEG liposomes displayed prolonged blood circulation with CT density differences above 70 Hounsfield units (aorta) for up to 20 minutes (n = 1). CONCLUSIONS: DSPE-PEG-coated and unmodified liposomes proved to be useful for CT blood-pool imaging displaying favorable imaging properties. Future studies will have to demonstrate whether PEG-ylation offers diagnostic or toxicologic advantages over conventional vesicles in this indication.

Animals↗
PubMed1997

Influence of contrast media on blood coagulation.

RATIONALE AND OBJECTIVES: Contrast agents have been reported to influence the blood clotting system to an extent depending mainly on whether the compounds are ionic or nonionic. The objective of the current series of studies was to determine interspecies differences; the effect of variable incubation times; and the effect on thromboplastin times (TPT) of adding heparin to a number of x-ray and magnetic resonance imaging (MRI) contrast agents. In addition, the stability of clots formed in the presence of iopromide was studied. In a final experiment, the effect of the contrast agents on the bleeding time was studied in rats. METHODS: Nine x-ray and three MRI contrast agents were used in the study. Thromboplastin times was determined in platelet-poor plasma of humans, rats, rabbits, or dogs using calcium (Ca) thromboplastin from human placenta or rabbit brain and lung tissue and incubation times as long as 4 hours. Bleeding times were determined in rats 5 minutes, 4 hours, 24 hours, and 48 hours after intravenous injection of the contrast agents by making a small incision into the tail of the animal, immersing the tail in saline, and measuring the time period during which small blood streaks were visible. RESULTS: Nonionic contrast agents (x-ray and MRI) increased the TPT by a factor of 1.5 to 2, whereas ionic compounds prolonged TPT by a factor of > 3. Thromboplastin times increased in the order of dog < rabbit < rat < human 2- to 4-fold. However, the ranking of different contrast agents remained unchanged. Prolongation of bleeding time lasted as long as 24 hours for some contrast agents. Clots formed in the presence of iopromide were unstable and did not absorb the contrast agent. CONCLUSIONS: The animal models used in the current series of studies seem to be valid for predicting the effect of contrast agents on the blood clotting system in humans.

Animals↗
PubMed1997

A prototype liver-specific contrast medium for CT: preclinical evaluation of gadoxetic acid disodium, or Gd-EOB-DTPA.

PURPOSE: The suitability of the hepatobiliary contrast medium gadoxetic acid disodium, or Gd-EOB-DTPA, for liver enhancement at computed tomography (CT) was studied. MATERIALS AND METHODS: CT attenuation levels at 120 kV were measured in samples of increasing concentrations of gadolinium (gadoxetic acid disodium) or iodine (iopromide) in aqueous solutions in vitro. In dogs, CT attenuation in the liver was measured up to 90 minutes after a single intravenous injection of 0.3, 0.5, and 0.7 mmol Gd/kg gadoxetic acid disodium (three dogs per dose group). In addition, three VX2 tumor-bearing rabbits were examined (0.7 mmol Gd/kg). RESULTS: In vitro, the CT attenuation of gadolinium is 40% higher than that of iodine if calculated per milligram of gadolinium and iodine, respectively. In dogs, the median net increase in liver enhancement was 25, 33, and 43 HU with a dose of 0.3, 0.5, and 0.7 mmol Gd/kg, respectively. The gallbladder and bile ducts became clearly visible. In rabbits, liver enhancement of 25 HU provided improved visualization of the unenhanced tumor. CONCLUSION: Because of the higher CT attenuation of gadolinium compared with iodine and because of its liver-specific uptake, gadoxetic acid disodium is a contrast medium that may improve diagnosis of pathologic liver conditions at CT.

Animals↗
PubMed1997

Gd-EOB-DTPA and Yb-EOB-DTPA: two prototypic contrast media for CT detection of liver lesions in dogs.

PURPOSE: To characterize computed tomographic (CT) attenuation of iodine, gadolinium, and ytterbium in vitro and to study CT liver enhancement after administration of two prototypic hepatocyte-directed contrast media in dogs. MATERIALS AND METHODS: Samples with increasing concentrations of iodine, gadolinium, and ytterbium were measured for CT attenuation in a water phantom at tube voltages of 80, 120, and 137 kV. Three groups of five adult beagle dogs each received a 0.5 mmol/kg dose of either gadoxetic acid disodium (gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid [EOB-DTPA]) or Yb-EOB-DTPA as intravenous infusions or Yb-EOB-DTPA as an intravenous bolus injection. RESULTS: At 120 kV, in vitro CT attenuation of gadolinium and ytterbium exceeded that of iodine by 41% and 45%, respectively, when measured at equal mass concentrations (in milligrams per milliliter of saline). In dogs, CT liver enhancement values above the precontrast liver attenuation were 32.6 HU +/- 2.3, 31.4 HU +/- 1.1, and 33.4 HU +/- 5.2 after 0.5 mmol/kg Gd-EOB-DTPA or Yb-EOB-DTPA infusion or Yb-EOB-DTPA bolus, respectively. The values were not significantly different (P > .05) CONCLUSION: Both Gd-EOB-DTPA and Yb-EOB-DTPA provide excellent CT liver enhancement in dogs. CT liver enhancement is not significantly altered by either the absorbing element (gadolinium vs ytterbium) or the mode of application (infusion vs bolus).

Animals↗
PubMed1997

[Endoscopic fusion of the lumbar vertebrae].

For certain indications, anterior fusion of the lumbar spine is a standard operation. The surgeon specializing in operations on the vertebral column needs to learn to utilize the advantages of laparoscopic surgery. However, an absolute must before employing the technique in patients is adequate training in its use in living animals. For this purpose, the pig is a highly suitable model. The surgical team comprises a surgeon experienced in spinal procedures, an abdominal surgeon with skills in laparoscopic surgery and an experienced camera assistant. In the animal model and in clinical trials, a change in position-organ preparation from the cranial direction, a suprasym-physial approach to the vertebrae-has proved expedient. The use of a special instrumentarium for maintaining the pneumo-peritoneum, for protecting the spinal cord and for exact centering, including the application of a special dowel (ESKA-spacer and instruments) is essential. The greater technical effort may be expected to result in shorter hospitalization (2-3 days) in the future.

Animals↗
PubMed1996

[Value of computer-assisted sperm analysis (CASA). Reproducibility--online documentation--prognostic value].

Computer-Assisted Semen Analysis (CASA) permits a determination of sperm count and sperm motility, improves reproducibility and facilitates the documentation of the results. In addition, new motility parameters can be measured. An analysis of the CASA parameters of 792 ejaculates revealed that their distribution is similar to that of the sperm count and sperm motility obtained by simple microscopic counting. A comparison of CASA parameters with the subsequent conception rate with the aid of Cox's regression analysis, showed that sperm count and total motility are the sole predictors of fertility. Attempts to measure sperm morphology using CASA have already been initiated. It can be noted that CASA analysis is superior to the simple microscopic evaluation of the ejaculate in its objectivity, reproducibility and on-line documentation. However, it does not increase the significance of semen analysis in terms of fertility prognosis.

Documentation↗
PubMed1996

Catecholamine release from fractionated chromaffin cells.

Bovine chromaffin cells were separated by density gradient centrifugation into subfractions. After centrifugation on a self-generating Percoll gradient (42.75% isotonic Percoll, 30,000 x g for 22 min at 20 degrees C), the chromaffin cells were found in two clearly distinguishable peaks. The peak with the lower density contained most of the noradrenaline-producing cells (approximately 80%), whereas the adrenaline-producing cells were equally distributed between the two peaks. After collection of suitable fractions from the gradient, cell cultures were obtained, which were enriched with either > 90% adrenaline- or approximately 65% noradrenaline-producing cells. When stimulated by nicotine or carbachol, the dose-response curves of both cell fractions yielded similar EC50s for the release of adrenaline and noradrenaline. On the other hand, the cells of the less dense fraction released 30% more catecholamines (adrenaline as well as noradrenaline) than the cells of the more dense fraction. It is suggested that there are subpopulations among the adrenaline- and noradrenaline-producing cells with differences in receptor-effector coupling.

Adrenergic Agonists↗