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Biomedical subjects

M Ludwig

Publications and source records attributed to M Ludwig.

At least 109 records · Page 6Linked to original sources
PubMed2000

A metal-chelating microscopy tip as a new toolbox for single-molecule experiments by atomic force microscopy.

In recent years, the atomic force microscope (AFM) has contributed much to our understanding of the molecular forces involved in various high-affinity receptor-ligand systems. However, a universal anchor system for such measurements is still required. This would open up new possibilities for the study of biological recognition processes and for the establishment of high-throughput screening applications. One such candidate is the N-nitrilo-triacetic acid (NTA)/His-tag system, which is widely used in molecular biology to isolate and purify histidine-tagged fusion proteins. Here the histidine tag acts as a high-affinity recognition site for the NTA chelator. Accordingly, we have investigated the possibility of using this approach in single-molecule force measurements. Using a histidine-peptide as a model system, we have determined the binding force for various metal ions. At a loading rate of 0.5 microm/s, the determined forces varied from 22 +/- 4 to 58 +/- 5 pN. Most importantly, no interaction was detected for Ca(2+) and Mg(2+) up to concentrations of 10 mM. Furthermore, EDTA and a metal ion reloading step demonstrated the reversibility of the approach. Here the molecular interactions were turned off (EDTA) and on (metal reloading) in a switch-like fashion. Our results show that the NTA/His-tag system will expand the "molecular toolboxes" with which receptor-ligand systems can be investigated at the single-molecule level.

Chelating Agents↗
PubMed2000

Use of frozen-thawed testicular sperm for intracytoplasmic sperm injection.

OBJECTIVE: To determine the feasibility of using frozen-thawed testicular spermatozoa for intracytoplasmic sperm injection. DESIGN: Prospective clinical study. SETTING: A university hospital. PATIENT(S): One hundred seventy-five azoospermic men participating in a routine intracytoplasmic sperm injection program. INTERVENTION(S): The men underwent testicular biopsy for cryopreservation of tissue to be used in consecutive intracytoplasmic sperm injection treatment cycles. Their female partners underwent controlled ovarian hyperstimulation for conventional IVF treatment. MAIN OUTCOME MEASURE(S): Fertilization and pregnancy rates. RESULT(S): In 77% of the patients, spermatozoa could be harvested from the testis by an open testicular biopsy technique and used for intracytoplasmic sperm injection after freezing and thawing of testicular tissue. Histopathologic evaluation revealed a Sertoli cell-only pattern in 21%, maturation arrest in 60%, and hypospermatogenesis in 19% of the patients. In 2. 9% of the patients, carcinoma in situ or a germ cell tumor was detected. In all patients, viable spermatozoa could be visualized after the tissue samples were thawed. One hundred thirty-five intracytoplasmic sperm injection treatment cycles were performed, with a fertilization rate of 45% and a clinical pregnancy rate of 30% per oocyte retrieved. CONCLUSION(S): The use of frozen-thawed testicular tissue allows ovarian stimulation of the female partner to be timed and avoids cancellation of ovum pick-up when spermatozoa cannot be retrieved.

Chromosome Aberrations↗
PubMed2000

Comparison of expressed prostatic secretions with urine after prostatic massage--a means to diagnose chronic prostatitis/inflammatory chronic pelvic pain syndrome.

OBJECTIVES: To compare the analysis of urine after prostatic massage (VB3) with expressed prostatic secretions (EPS) to assess the significance of leukocyte analysis in VB3 and to give a first hint of the diagnosis of inflammatory chronic pelvic pain syndrome (CPPS) when EPS cannot be obtained. METHODS: Three hundred twenty-eight men (mean age 38 years, range 18 to 70) with expressible prostatic secretions were investigated. EPS were stained using the Papanicolaou stain and analyzed for leukocytes per high power field (HPF) (x1000). Additionally, identical aliquots of first voided urine (VB1), midstream urine (VB2), and VB3 were centrifuged, stained (Papanicolaou), and analyzed for leukocytes (x400). Patients with increased numbers of leukocytes in VB1 and VB2 (2 or more per x400) were excluded. For statistical analysis, Spearman's correlation coefficient for nonparametric tests was used. RESULTS: Of 180 men with less than 10 leukocytes per HPF in EPS, 178 (98.9%) had less than 10 leukocytes per view field in VB3. In 148 men with 10 or more leukocytes per HPF in EPS, 136 (91.9%) also had elevated leukocyte counts in VB3. The presence of elevated leukocytes in VB3 predicted the presence of increased leukocytes in EPS with a high certainty: 91.9% sensitivity, 98.9% specificity, and 95.7% accuracy, with a positive and negative predictive value of 98.6% and 93.7%, respectively. CONCLUSIONS: We conclude that the determination of leukocytes in VB3 is a feasible and reliable method compared with the analysis of EPS. However, although this association does not directly prove the significance of VB3 in those patients from whom no EPS can be obtained, we suggest this method be taken into account as an indirect indicator in the diagnosis of inflammation.

Adolescent↗
PubMed2000

7alpha-Hydroperoxycholesterol causes CNS neuronal cell death.

Brain cholesterol, which is synthesized in the central nervous system and also partly taken up from lipoproteins via the blood-brain barrier, is a major component of neuronal membranes. Oxidation of cholesterol leads to the formation of oxysterols, which have been shown to act cytotoxic. The influence of 7alpha-hydroperoxycholesterol, was investigated using the human neuroblastoma cell line SH-SY5Y. 7alpha-Hydroperoxycholesterol caused neuronal cell death; this neurotoxic effect was dose-dependent, within 48 h 10 microM led to 50%, 50 microM to 92% loss of cell viability, which was detected by cell morphology and Trypan blue exclusion. DNA-fragmentation or caspase-3 activity were not detectable, LDH release occurred rapidly and reactive oxygen species (ROS) were generated. Therefore we infer that 7alpha-hydroperoxycholesterol, apart from its role in atherosclerosis, leads to necrosis of neuronal cells.

Apoptosis↗
PubMed2000

No significant leukocytosis under controlled ovarian stimulation using the LHRH antagonist Cetrorelix and recFSH.

OBJECTIVE: To study the influence of an LHRH (luteinizing hormone releasing hormone) antagonist protocol (Cetrorelix) and the use of recombinant follicle-stimulating hormone (FSH) on the development of leukocytosis, compared to the use of urinary HMG (human menopausal gonadotrophin). DESIGN: Prospective, randomized phase III clinical trial. SETTING: Infertility day clinic, Department of Gynecology and Obstetrics. PATIENTS: Thirty patients undergoing IVF/intracytoplasmic sperm injection (ICSI) treatment following controlled ovarian stimulation using a multiple dose protocol and the LHRH antagonist Cetrorelix. MAIN OUTCOME MEASURE: Differences in white blood cell (WBC) count before stimulation, during the follicular phase and in the midluteal phase. RESULTS: Statistically significant increase in WBC count in the HMG group from the start of stimulation to the midluteal phase. No statistically significant increase in the recFSH group, but only a trend towards higher values was observed. CONCLUSION: The development of a leukocytosis in controlled ovarian stimulation does not depend on the protocol used. Urinary gonadotrophins seem to have a greater potential to increase WBC count compared to recombinant gonadotrophins.

Estradiol↗
PubMed2000

Vasopressin regulation of noradrenaline release within the supraoptic nucleus.

The effect of electrically evoked dendritic vasopressin release on noradrenaline release into the hypothalamic supraoptic nucleus was assessed by in vivo microdialysis in conjunction with high pressure liquid chromatography and electrochemical detection. Electrical activation of magnocellular supraoptic neurones by stimulation of their axons at the level of the neural lobe significantly increased noradrenaline release into the nucleus (2.5-fold, P<0.03). This increase was completely blocked by administration of a nonpeptide vasopressin V1a receptor antagonist via the microdialysis probe. These data suggest that dendritically released vasopressin facilitates noradrenaline release into the hypothalamic nucleus.

Antidiuretic Hormone Receptor Antagonists↗
PubMed2000

Differential mRNA expression of the two mineralocorticoid receptor splice variants within the human brain: structure analysis of their different DNA binding domains.

In human brain tissue, cortisol action, at basal concentrations, is mediated by the mineralocorticoid receptor (MR). An in-frame insertion of 12 bp in the MR-DNA-binding domain due to alternative splice site usage between exons 3 and 4 results in an MR mRNA splice variant (MR+4) encoding a receptor protein with four additional amino acids compared to the wild-type MR protein. To elucidate the questions of sex, age, and/or tissue dependent differences of the relative amount of the two mRNA subtypes, we examined 131 fresh human brain tissue samples from temporal and frontal lobe or hippocampus. One hundred and twenty samples were obtained from patients with epilepsy and 11 samples from patients with brain tumours. A small but significant difference of the MR+4 mRNA splice variant proportions in cortex (9.5 +/- 0.8%) and subcortical white matter (6.6 +/- 0.7%) of the temporal lobe could be detected, indicating differential MR splice variant expression within these brain areas. Moreover, the splice variant ratios in samples of the temporal lobe cortex collected from patients with epilepsy differed from samples of patients with brain tumours. These data point to an altered expression of the MR splice variants in epilepsy, and strengthen the supposition of a tissue specific alternative splicing of the MR mRNA. The frequent occurrence of the MR+4 transcript raises the question of its functional significance. For this reason, an MR+4 DNA-binding-domain structure model was generated by computer-based homology modelling based on the known glucocorticoid receptor structure. The data obtained revealed no distorting effect of the inserted four amino acids on the adjacent secondary structures, thereby suggesting that both zinc fingers retain their function. The resulting structure of the MR+4 model leads to the supposition that the receptor retains its function. Moreover, databank analysis with respect to this kind of steroid receptor variation and our own sequence data of the closely related progesterone receptor sustained the hypothesis that only corticosteroid receptors were affected by this alternative splicing event.

Adult↗
PubMed2000

Experience with the elective transfer of two embryos under the conditions of the german embryo protection law: results of a retrospective data analysis of 2573 transfer cycles.

The German embryo protection law (Embryonenschutzgesetz, ESchG) does not allow embryo selection. Therefore, only as many oocytes at the pronuclear stage (PN), as are planned to be transferred, are allowed to be cultured. It is not known whether, under these conditions, it is possible to reduce the number of embryos for transfer without a corresponding reduction of the overall pregnancy rate (PR). We retrospectively analysed 2573 consecutive transfer cycles following either in-vitro fertilization (IVF) or IVF/intracytoplasmic sperm injection. Out of these cycles, 234, 329 and 792 were performed with one, two, and three embryos respectively, because only that number was available (non-elective transfer). Another 123 and 1095 transfer cycles were performed with two and three embryos, respectively, which were selected from a higher number of PN oocytes (elective transfer). The clinical ongoing PR were 3.9, 9.1 and 17.7% respectively for the groups with non-elective transfer of 1, 2 and 3 embryos, and 22.0 and 22.5% for the groups with elective transfers with two and three embryos, respectively. There was no statistically significant difference in PR between the two elective embryo transfer groups up to the age of 40 years. The multiple pregnancy rate was reduced by 7.9%. The reduction of the number of embryos transferred from three to two can be performed even under the conditions of the ESchG without an effect on the overall PR.

Abortion, Spontaneous↗
PubMed2000

Clinical use of a pronuclear stage score following intracytoplasmic sperm injection: impact on pregnancy rates under the conditions of the German embryo protection law.

The German embryo protection law does not allow embryo selection, but only selection of pronuclear stage (PN) oocytes. Only as many PN oocytes are allowed to be selected as are planned to be transferred. Therefore, a clinically applicable score to assess the quality of PN oocytes would be helpful. A recently published score was used under the conditions of the German embryo protection law in 74 non-selected, consecutive intracytoplasmic sperm injection cycles. Only criteria which could be evaluated at the PN stage were included, i.e. not criteria which could only be assessed after pronuclear membrane breakdown or the first cleavage division. Supernumerary PN oocytes were cryopreserved after selection. A mean PN score of <13 (sum of scores of all selected PN oocytes/number of selected PN oocytes) led to a pregnancy rate of 4%, a mean PN score of > or =13 to a pregnancy rate of 22%. Embryo morphology and cumulative PN were correlated (r = 0.52, P < 0.05). The negative predictive value was 92% at a threshold of 13 for the mean PN score. The use of this and perhaps additional scoring systems of PN stage oocytes might help to offer patients in Germany the transfer of two selected PN oocytes, which would reduce the multiple pregnancy rate.

Adult↗
PubMed2000

Ovarian stimulation for assisted reproduction with HMG and concomitant midcycle administration of the GnRH antagonist cetrorelix according to the multiple dose protocol: a prospective uncontrolled phase III study.

A total of 346 women with normal ovulatory function was stimulated with human menopausal gonadotrophins (HMG) to attain ovarian stimulation for IVF or intracytoplasmic sperm injection (ICSI). Stimulation with HMG started on cycle day 2 or 3. After 6 days of stimulation, Cetrorelix in its minimum effective multiple dose of 0. 25 mg/day, was administered daily until induction of ovulation. In total, 333 patients (96.2%) reached the day of HCG administration, and 324 (93.6%) underwent oocyte retrieval. A mean of 25.2 ampoules of HMG was applied for a mean of 10.4 days. Cetrorelix was administered for a mean time lapse of 5.7 days. The mean normal fertilization rate was 60% in the IVF group and 59% in the ICSI group. Seventy pregnancies were attained, reflecting an ongoing clinical pregnancy rate of 24% per transfer. The ongoing clinical implantation rate was 11.4%. Only three cases of raised luteinizing hormone (LH) (>/=10 IU/l) with increased progesterone secretion (>/=1 ng/ml) were observed after initiation of Cetrorelix administration, reflecting an incidence of premature luteinization of 0.9%. The abortion rate was 17%. The incidence of severe ovarian hyperstimulation syndrome (World Health Organization grade III) was as low as 0.6%.

Dose-Response Relationship, Drug↗
PubMed2000

Surgical therapy in infertile men with ejaculatory duct obstruction: technique and outcome of a standardized surgical approach.

In severe oligozoospermia or azoospermia, low ejaculate volume, low ejaculate pH and little or no fructose in seminal plasma suggest an obstruction of the seminal pathways at the level of the prostate gland, when vasal aplasia and ejaculatory disorders are excluded. We report on our standardized surgical approach in 16 consecutive patients with this condition after clinical evaluation, semen analysis, endocrine assessment, testicular biopsy and transrectal ultrasonography. Pre-operatively, sperm analysis demonstrated typical low-volume ejaculates with azoospermia in 12 and severe oligozoospermia in four cases. Ultrasonography demonstrated seven central (Müllerian) and five lateral cystic lesions. Four cases with central obstruction revealed no ultrasonographic pathology. After intra-operative vasopuncture and vasography for definite localization of the level of obstruction, transurethral incision and/or resection of ejaculatory ducts (TURED) was performed. Patency was proven in 15 out of 16 cases by 'intra-operative chromotubation'. In nine out of 12 patients, spermatozoa could be harvested intra-operatively from the vas. During the follow-up of 12 months, post-operative ejaculates showed persistent patency in six out of seven Müllerian cysts with concomitant improvement of sperm quality. Only three of the other nine cases remained patent with the worst results in lateral cystic lesions. Only two of the patients with Müllerian cysts have fathered a child so far. The data provide evidence for the effectiveness of surgical treatment of ejaculatory duct obstruction, especially in the case of central cystic lesions. The combination of surgery, cryostoring of spermatozoa retrieved intra-operatively and the possible storage of ejaculated spermatozoa post-operatively creates the possibility of subsequently using reproductive techniques if pregnancy is not achieved.

Adult↗
PubMed2000

High-normal serum homocysteine concentrations are associated with an increased risk of early atherosclerotic carotid artery wall lesions in healthy subjects.

OBJECTIVE: Moderate hyperhomocysteinaemia is common in the general population and has been linked with systemic atherosclerotic vascular disease. We studied the relation of sonographically determined carotid intima-media wall thickness to serum homocysteine concentrations in asymptomatic, healthy subjects. METHODS AND RESULTS: Seventy-five male and female untreated subjects (mean age 49 years, range 22-75) with normal serum folate concentrations were included. High-resolution duplex sonography was used to determine intima-media thickness of the common carotid artery. Serum homocysteine concentration was measured by high-performance liquid chromotography with fluorescence detection. Mean intima-media thickness (+/- SD) was 0.78 +/- 0.19 mm (range 0.5-1.35) and mean serum homocysteine concentration was 10.5 +/- 2.81 micromol/l (range 5.7-19.6). In stepwise regression models, statistically significant predictors of intima-media thickness included age, body mass index, LDL cholesterol and homocysteine (R2 = 0.51). Homocysteine concentration was independently associated with intima-media thickness after adjustment for the other variables (P < 0.001) and explained an additional 18% of the variation of intima-media thickness. CONCLUSIONS: In healthy subjects, high-normal serum homocysteine concentrations are associated with an increased prevalence of carotid artery wall thickening. The significance of the contribution of homocysteine to the variation of carotid intima-media thickness, even at concentrations previously believed to be normal, suggests a role for homocysteine as an independent risk factor for early carotid artery atherosclerosis in the asymptomatic subjects.

Adult↗
PubMed2000

Influence of urogenital infection on sperm function.

Male accessory sex gland infections are considered to be hazards to male fertility. Various pathophysiologic concepts have evolved from experimental and clinical studies that begin to explain the effects of bacteria and immunologic events on spermatozoa. Recent studies have identified and evaluated mediators that are responsible for specific molecular processes in infections that particularly affect the function of spermatozoa.

Bacterial Infections↗
PubMed2000

Quo vadis neurohypophysial hormone research?

Here we highlight just a few of the outstanding questions in the field of neurohypophysial hormones that we envisage will be addressed successfully in the new millennium. To begin, we focus on the regulation of receptors. Despite intensive investigation with new drugs, molecular modelling and transgenic models, the determinants of receptor selectivity remain elusive; there may even be more vasopressin or oxytocin receptor subtypes to be discovered. We discuss the controversy over the interesting studies that indicate modulation of oxytocin receptor-binding by steroids. Oxytocin and vasopressin release and action in the brain are discussed from several aspects. Dendritically released oxytocin acting locally is important for the milk ejection reflex, and similarly released vasopressin is important in regulating patterning of vasopressin neurone activity. Such dendritically released oxytocin and vasopressin is likely to be important in paracrine modulation of neural circuitry involved in neuroendocrine control, and for a range of behaviours. Is it possible that the whole range of behaviours that comprise 'social' (or 'anti-social') or 'maternal' behaviour can be engineered by modifying the expression of just these one or two peptides and their receptors? However, whether gene expression and knockout approaches will answer all the open questions about the real functions of oxytocin and vasopressin remains to be shown.

Animals↗
PubMed2000

Extracorporal shock wave therapy in the treatment of Peyronie's disease. First results of a case-controlled approach.

OBJECTIVE: To test whether extracorporal shock wave therapy (ESWT) has an effect in the treatment of Peyronie's disease. METHODS: 22 patients with Peyronie's disease and previous unsuccessful oral drug therapy were treated with ESWT in a prospective design with a follow-up of at least 3 months; 23 age-matched patients without previous therapy received oral placebo drug for 6 months daily as control. The standard follow-up included palpation, ultrasound, autophotography and evaluation of symptomatology based on a symptom score. The shock waves were applied under ultrasound guidance using the 'Storz Minilith SL1' lithotripter. RESULTS: The results show a significant decrease in penile curvature in the patients treated with ESWT. Concerning the decrease in pain, subjective improvement and improvement in the quality of sexual intercourse, there was no significant difference to the case-control group. The inhomogeneity of the 2 groups may influence these results due to the questionable varying natural history. CONCLUSIONS: A prospective, controlled multicenter study with standardized parameters (concerning technique and patients) is urgently required to test the effect of ESWT.

Case-Control Studies↗
PubMed2000

No association between an intronic biallelic polymorphism of the FE65 gene and Alzheimer's disease.

The cleavage of the amyloid precursor protein (APP) into amyloidogenic components (Abeta) is a central event in the pathogenesis of Alzheimer's disease (AD). FE65 is a protein that is involved in APP metabolism and may facilitate the production of Abeta. Recently, an intronic polymorphism of the gene encoding FE65 (FE65) was associated with altered risk for the development of sporadic AD. In our sample of 102 AD patients and 351 non-demented controls we did not replicate the association between FE65 and AD. Moreover, we observed no risk-modifying interaction and no linkage disequilibrium between FE65 and the gene encoding the acid protease cathepsin D (catD), which - like FE65 - is involved in APP metabolism and is also located on chromosome 11p15. We conclude that, whereas FE65 is implicated in AD pathology, the gene encoding FE65 does not appear to confer a substantial risk for AD.

Aged↗