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M Schrader

Publications and source records attributed to M Schrader.

At least 55 records · Page 3Linked to original sources
PubMed2001

Molecular markers in testicular germ cell tumors--objects of clinical research or close to becoming clinical tools?

The aim of this short review is to critically evaluate hitherto investigated molecular markers for testicular germ cell tumors. Molecular parameters have been clinically established as diagnostic and prognostic markers for a number of tumors; this has not yet been achieved for germ cell tumors. There are interesting prospects, however. Studies on the ribonucleoprotein telomerase, for example, have demonstrated a correlation between enzyme activity and chemotherapeutic drug sensitivity. Moreover, innovative treatment approaches target this reverse transcriptase via telomerase antisense RNA. Another potential diagnostic marker is the detection of circulating tumor cells, which correlated with an increased relapse rate in initial studies. There are also interesting possibilities for the germ-cell-tumor-specific isochromosome [i(12)p], which is helpful in the differential diagnosis of mediastinal masses. Here initial studies demonstrated a correlation between the copy number and resistance against chemotherapeutic drugs. Without prospective studies to validate data obtained thus far, neither these nor other parameters can be assessed as diagnostic and prognostic factors. Irrespective of their immediate clinical applicability, however, investigations on molecular alterations in testicular germ cell tumors will become the basis for a molecular-diagnostically oriented subclassification of tumors as well as for novel therapeutic approaches.

Chromosome Aberrations↗
PubMed2001

Impact of chemotherapy on male fertility.

Testicular tumors and malignant lymphomas are, with increasing incidence, the most frequent malignant diseases in men between the age of 15 and 34. With the introduction of cisplatin-based polychemotherapy, cure rates rose to over 90% in patients with germ cell tumors and were comparably favorable at around 80% in those with malignant lymphomas. In view of these high cure rates, increasing clinical importance is attached to chemotherapy induced fertility disorders. One problem involved in assessing the influence of chemotherapy on fertility is the fact that the malignant disease itself strongly alters spermatogenesis. This complicates an evaluation of the effect of cytostatic therapy on fertility disorders. There are significant cytostatic- and dose-specific differences. Longterm infertility due to cytostatic therapy may be expected in more than 50% of the patients at a cumulative dose of cisplatin > 0.6 g/m(2), cyclophosphamide > 6 g/m(2), and procarbazine >/= 4 g/m(2). However, it takes up to 3 years or more for spermatogenesis to recover after the termination of chemotherapy. An individual assessment of the post-therapeutic fertility status is extremely limited, since variance of the pretherapeutic fertility status causes interindividual differences, and the numerical data mentioned above only permit a vague estimation. Before patients undergo cytostatic therapy, cryopreservation of germ cells should thus be suggested or, in some cases, testicular extraction of spermatozoa.

Adolescent↗
PubMed2001

Tubulo-reticular clusters of peroxisomes in living COS-7 cells: dynamic behavior and association with lipid droplets.

We characterized more complex peroxisomal structures, i.e., tubulo-reticular peroxisomal clusters, in greater detail under in vivo conditions in COS-7 cells that were transfected with a GFP-PTS1 fusion protein. Live cell imaging revealed the dynamic nature of peroxisomal clusters and allowed a detailed analysis of the motile properties of a heterogeneous peroxisome population. Furthermore, peroxisomal clusters were found to be associated with lipid droplets. The frequency of peroxisomal clusters correlated with an increase in cell density and in the size of lipid droplets. These data provide further evidence for the dynamic nature of the peroxisomal compartment and indicate that peroxisomal clusters have a function in lipid metabolism.

Animals↗
PubMed2001

Peptidomics: the comprehensive analysis of peptides in complex biological mixtures.

Progress in the sequencing of genomes has resulted in an increasing demand for a functional analysis of gene products in order to understand the underlying physiology. Proteomics has established itself as a highly valuable technology for producing functionally related data in an unparalleled fashion, but is methodologically restricted to the analysis of proteins with higher molecular masses (>10 kDa). The development of a technology which covers peptides with low molecular weight and small proteins (0.5 to 15 kDa) was necessary, since peptides, amongst them families of hormones, cytokines and growth factors, play a central role in many biological processes. To summarise the technologies used for this approach the term "peptidomics" is introduced. In this article, we present the rationale and first results of a novel, universal peptide display approach for the analysis and visualisation of peptides and small proteins from biological samples. Special attention is given to samples derived from extracellular fluids such as blood plasma and cerebrospinal fluid. Additionally, a high throughput identification procedure for the analysis of peptides in their native and processed molecular form is outlined.

Combinatorial Chemistry Techniques↗
PubMed2001

Osteoporosis and mild metabolic acidosis in the rat after orchiectomy and their prevention: should prophylactic therapy be administered to patients with androgen deprivation?

PURPOSE: To date there has been little research on the etiology and prophylaxis of osteopenia during androgen deprivation. This condition is gaining increasing attention, partially due to the considerable osteoporosis related side effects of hormone withdrawal symptoms in patients with prostate cancer. We characterized androgen deprivation and its prophylaxis. MATERIALS AND METHODS: A total of 36 male Sprague-Dawley rats underwent laparotomy, orchiectomy or orchiectomy with subsequently treatment with calcium acetate and sodium citrate via the water supply. Postoperative observation was 19 weeks. Test parameters were weight development, testosterone, parathyroid hormone, vitamin D, osteocalcin, cross links, hydroxyproline and cyclic adenosine monophosphate as well as bone density, tensile strength, mineral content and histomorphometry. RESULTS: Animals subjected to orchiectomy had a reduction in bone mineral content and fracture energy with mild metabolic acidosis. The markers of bone metabolism were statistically unchanged, while the ratio of trabeculae-to-tissue area decreased. Animals treated with orchiectomy, calcium acetate and sodium citrate had moderately compensated metabolic alkalosis and increased bone minerals. Fracture energy was likewise normal and there was a tendency toward higher bone metabolism. CONCLUSIONS: Castration led to a reduced increase in body mass, considerable standard deviation from biochemical and histological criteria for tubular bone and, thus, an increased fracture risk. A possible cause may be reduced formation and unchanged bone loss combined with mild metabolic acidosis. Calcium and alkalization seem to be effective prophylaxis for androgen deprivation. Considering the large number of osteoporotic complications after androgen deprivation, further clinical studies are justified to show the benefits of prophylactic therapy.

Acetates↗
PubMed2001

Increased incidence of luteinizing hormone-releasing hormone receptor gene messenger RNA expression in hormone-refractory human prostate cancers.

There are few options for treating hormone-refractory prostate cancer (PC). Various studies indicate that luteinizing hormone-releasing hormone (LHRH) agonists may have a direct inhibitory effect on prostate tumors mediated by specific LHRH receptors. One study evaluated LHRH receptors in hormone-dependent PC tissue, but no data have thus far been obtained on the presence of LHRH receptors in benign prostatic hyperplasia (BPH) and especially hormone-refractory PC in patients. Thus, it is not yet clear whether LHRH receptors indicate tumor-related differentiation or even hormone-refractory dedifferentiation or are likewise associated with BPH. The aim of this study was to determine the rate of LHRH receptor mRNA expression in BPH and in primary, potentially androgen-dependent and in hormone-refractory PC with clinical progression. Multiplex reverse transcription-PCR was used to simultaneously detect the expression of mRNA for LHRH receptors and beta-actin in 48 patients with BPH, 14 with a primary, possibly hormone-dependent, prostate carcinoma (PPC), and 18 with a hormone-refractory prostate carcinoma (HRPC). Sixteen of 18 samples with HRPC showed intact RNA and expressed mRNA for LHRH receptors (100%). However, the RNA-intact PPC and BPH showed significantly lower expression of mRNA for LHRH receptors (46.2 and 55.3%, respectively; variance analysis: P = 0.0017). The significantly higher expression of mRNA for LHRH receptors in HRPC indicates that therapeutic concepts should be developed that target this site of action. In addition to possible direct effects of LHRH agonists or antagonists demonstrated previously in vitro, it seems useful to apply targeted cytotoxic LHRH analogues or monoclonal antibodies.

Aged↗
PubMed2001

Quantification of human telomerase RNA (hTR) and human telomerase reverse transcriptase (hTERT) mRNA in testicular tissue of infertile patients.

AIM: To evaluate the quantitative detection of human telomerase RNA (hTR) and human telomerase reverse transcriptase (hTERT) mRNA as diagnostic parameters in the workup of testicular tissue specimens from patients presenting with non-obstructive azoospermia. METHODS: hTR and hTERT mRNA expression were quantified in 38 cryopreserved testicular tissue specimens by fluorescence real-time reverse transcription-polymerase chain reaction (RT-PCR) in a LightCycler(r). This was paralleled by conventional histological workup in all tissue specimens and additional semithin sectioning preparation in cases with maturation arrest (n = 12) and Sertoli-cell-only syndrome (n = 12). RESULTS: The average normalized hTERT expression (N(hTERT)) was 131.9 +/- 48.0 copies (mean +/- SD) in tissue specimens with full spermatogenesis, N(hTERT) = 51.2 +/- 17.2 copies in those with maturation arrest and N(hTERT) = 2.7 +/- 2.4 copies in those with Sertoli-cell-only syndrome (SCOS). The discriminant analysis showed that detection of N(hTERT) (N(hTR)) had a predictive value of 86.8% (55.3%) for correct classification in one of the three histological subgroups. CONCLUSION: Our results demonstrate that quantitative detection of hTERT mRNA expression in testicular tissue enables a molecular-diagnostic classification of gametogenesis. Quantitative detection of hTERT in testicular biopsies is thus well suited for supplementing the histopathological evaluation.

DNA-Binding Proteins↗
PubMed2000

Fluorescent methylation-specific polymerase chain reaction for DNA-based detection of prostate cancer in bodily fluids.

Promoter hypermethylation of the glutathione S-transferase P1 gene (GSTP1) is the most frequent DNA alteration in prostatic carcinoma. Because this epigenetic DNA alteration can be reliably detected by methylation-specific PCR (MSP), we applied this new technique for molecular detection of prostate cancer in various human bodily fluids. We investigated GSTP1 promoter hypermethylation in DNA isolated from plasma, serum, ejaculate, and urine after prostate massage and from prostate carcinoma tissues from 33 patients with prostate cancer and 26 control patients with benign prostatic hyperplasia (BPH). Fluorescently labeled MSP products were analyzed on an automated gene sequencer. Whereas GSTP1 promoter hypermethylation was not detectable by MSP in prostate tissue and bodily fluids from patients with BPH, we found it in 94% of tumors (16 of 17), 72% of plasma or serum samples (23 of 32), 50% of ejaculate (4 of 8) and 36% of urine (4 of 11) from patients with prostate cancer. Additionally, MSP identified circulating tumor cells in 30% (10 of 33) of prostate cancer patients. Analysis of GSTP1 promoter hypermethylation by MSP thus provides a specific tool for molecular diagnosis of prostate cancer in bodily fluids.

Adenocarcinoma↗
PubMed2000

SH3 binding sites of ZG29p mediate an interaction with amylase and are involved in condensation-sorting in the exocrine rat pancreas.

ZG29p, a novel pancreas-specific zymogen granule protein, has been proposed to act as a 'helper protein' in granule formation. To address its function in more detail, we searched for putative binding partners of ZG29p. In zymogen complexes isolated by nondenaturing isoelectric focusing, ZG29p was associated with a protein complex consisting of amylase and cationic trysinogen. Amylase also coeluted with ZG29p after immunoaffinity chromatography using an antibody to recombinant ZG29p. Cross-linking experiments with granule content proteins revealed a direct interaction between recombinant ZG29p and amylase. An interaction was also observed when purified amylase was used, whereas no interaction with recombinant or purified cationic trypsinogen was seen. ZG29p could also be cross-linked to three membrane proteins with molecular masses of 40, 18, and 16 kDa. The binding of ZG29p to amylase and to the membrane proteins was inhibited in the presence of synthetic peptides matching the consensus sequence of proline-rich SH3 binding sites present in ZG29p. The synthetic peptides could be cross-linked to amylase and to three yet unidentified acidic content proteins with molecular masses of about 30 kDa. The peptides also interacted with purified or recombinant amylase, but not with recombinant or purified cationic trypsinogen. In a condensation-sorting assay, the binding (sorting) of zymogen complexes to the granule membrane was reduced in the presence of the peptides. Our results indicate that the interaction of ZG29p with amylase is mediated by SH3 binding domains and that these domains are involved in the sorting of amylase to the granule membrane.

Amino Acid Sequence↗
PubMed2000

Disulphide-bond pattern and molecular modelling of the dimeric disintegrin EMF-10, a potent and selective integrin alpha5beta1 antagonist from Eristocophis macmahoni venom.

The disulphide-bond pattern of the heterodimeric disintegrin EMF-10, a potent and selective integrin alpha(5)beta(1) antagonist from Eristocophis macmahoni venom, was established by combination of amino-acid analysis, N-terminal sequencing and collision-induced dissociation by nanoelectrospray ionization quadrupole ion-trap MS of fragments isolated by reversed-phase HPLC after degradation of EMF-10 with oxalic acid. Each EMF-10 subunit contains four intrachain disulphide bonds. Two interchain cystine residues join the EMF-10 polypeptides. The intrachain linkages are conserved in monomeric disintegrins. A molecular model of EMF-10 was built using averaged NMR co-ordinates of flavoridin as a template. The active hairpin loops of the EMF-10 subunits occupy opposite locations at the ends of an elongated disulphide-bond ladder. In the EMF-10 model the N-terminal polypeptide of EMF-10B is close to the RGD-loop of the EMF-10A subunit, suggesting that the N-terminal region of the B-subunit could potentially influence the biological activity of the A-subunit.

Amino Acid Sequence↗
PubMed2000

Replacement of glycine 232 by aspartic acid in the KdpA subunit broadens the ion specificity of the K(+)-translocating KdpFABC complex.

Replacement of glycine residue 232 with aspartate in the KdpA subunit of the K(+)-translocating KdpFABC complex of Escherichia coli leads to a transport complex that has reduced affinity for K(+) and has lost the ability to discriminate Rb(+) ions (, J. Biol. Chem. 270:6678-6685). This glycine residue is the first in a highly conserved GGG motif that was aligned with the GYG sequence of the selectivity filter (P- or H5-loop) of K(+) channels (, Nature. 371:119-122). Investigations with the purified and reconstituted KdpFABC complex using the potential sensitive fluorescent dye DiSC(3)(5) and the "caged-ATP/planar bilayer method" confirm the altered ion specificity observed in uptake measurements with whole cells. In the absence of cations a transient current was observed in the planar bilayer measurements, a phenomenon that was previously observed with the wild-type enzyme and with another kdpA mutant (A:Q116R) and most likely represents the movement of a protein-fixed charge during a conformational transition. After addition of K(+) or Rb(+), a stationary current could be observed, representing the continuous pumping activity of the KdpFABC complex. In addition, DiSC(3)(5) and planar bilayer measurements indicate that the A:G232D Kdp-ATPase also transports Na(+), Li(+), and H(+) with a reduced rate. Similarities to mutations in the GYG motif of K(+) channels are discussed.

Adenosine Triphosphatases↗
PubMed2000

Telomerase activity and expression of telomerase subunits in the testicular tissue of infertile patients.

OBJECTIVE: Determination of telomerase activity and the expression of human telomerase RNA (hTR) and human telomerase reverse transcriptase (hTERT) in the testicular tissue of patients with infertility arising from various causes. DESIGN: Prospective observational study. SETTING: A university hospital. PATIENT(S): Thirty-three patients with azoospermia arising from various causes. There were 12 testicular biopsy specimens from patients with Sertoli cell-only syndrome, 9 from patients with maturation arrest, and 12 from patients with obstructive azoospermia and normal histologic findings. INTERVENTION(S): Thirty-three testicular biopsies. MAIN OUTCOME MEASURE(S): Correlation of histologic findings at testicular biopsy with telomerase activity, hTERT, and hTR. RESULT(S): All 12 biopsy specimens from patients with obstructive azoospermia were positive for telomerase activity, hTR, and hTERT. Biopsy specimens from the 9 patients with maturation arrest were positive for telomerase activity in 8 cases, hTR in 9 cases, and hTERT in 5 cases. None of the patients with Sertoli cell-only syndrome showed either telomerase activity or hTERT, but all of them showed hTR. CONCLUSION(S): Telomerase activity and evidence of hTERT in testicular tissue are highly sensitive and highly specific markers of gametogenesis, which could gain in importance as part of the fertility workup before microinjection procedures.

DNA-Binding Proteins↗
PubMed2000

Concomitment spread of a renal cell carcinoma beyond the kidney and a transitional cell carcinoma beyond the bladder.

We report the case of a 61-year-old man, with a rare combination of two advanced urological tumors: a concomitant spread of an adenocarcinoma beyond the kidney and a urothelial carcinoma beyond the bladder. We simultaneously performed a primary curative prostatovesiculectomy and a nephroureterectomy on the right with ileal neobladder. To our knowledge, a case report of concomitant spread of an adenocarcinoma beyond the kidney (pT3 pN0 M0 G3) and a urothelial carcinoma beyond the bladder (pT3a pN0 M0 G3) with subsequent curative therapy has thus far not been published. A combination of the two diseases described here is obviously a remarkable rarity.

Carcinoma, Renal Cell↗
PubMed2000

Interaction of peroxisomes with microtubules. In vitro studies using a novel peroxisome-microtubule binding assay.

The association of membrane-bounded cell organelles to microtubules is crucial for determination of their shape, intracellular localization and translocation. We have shown previously the high affinity binding of peroxisomes to microtubules which appears to be of static nature as in vivo studies indicate that only a few peroxisomes move along the microtubular tracks. In order to characterize the interactions of peroxisomes with microtubules, we have developed a semiquantitative in vitro binding assay, which is based on the association of highly purified rat liver peroxisomes to microtubules coated onto microtiterplates. The binding was visualized by differential interference contrast and immunofluorescence using a confocal laser scanning microscope. The binding was concentration dependent and saturable, being affected by time, temperature, and pH. Addition of ATP or the motor proteins kinesin and dynein increased the binding capacity, while ATP-depletion or microtubule associated proteins (MAPs) decreased it. KCl treatment of peroxisomes reduced the binding, which was restored by dialyzed KCl-stripping eluate as well as by rat liver cytosol. The reconstituting effect of cytosol was abolished by its pretreatment with proteases or N-ethylmaleimide. Moreover, the treatment of peroxisomes with proteases or N-ethylmaleimide reduced their binding, which was not reversed by cytosol. These results suggest the involvement of a peroxisomal membrane protein and cytosolic factor(s) in the binding of peroxisomes to microtubules. This notion is supported by the observation that distinct subfractions of dialyzed KCl-stripping eluate obtained by gel chromatography augmented the binding. Those subfractions, as well as purified peroxisome fractions, exhibited strong immunoreactivity with an antibody to cytoplasmic linker protein (CLIP)-115, revealing a 70-kDa polypeptide. Moreover, immunodepletion of KCl-stripping eluate and its subfractions with an antibody to the conserved microtubule binding domain of CLIPs, abolished their promoting effect on the binding, thus suggesting the involvement of a CLIP-related protein in the binding of peroxisomes to microtubules.

Adenosine Triphosphate↗
PubMed2000

Social network methods for endemic foci of syphilis: a pilot project.

BACKGROUND: Social network methods have improved our understanding of sexually transmitted disease transmission dynamics, and may be of use in routine field operations for partner notification. GOAL: To augment traditional syphilis-control activities with social network methods in an Atlanta area with high syphilis morbidity. STUDY DESIGN: Disease investigators conducted interviews, used network diagrams to prioritize their work, and relied on network connections for finding hard-to-reach persons. RESULTS: A total of 396 contacts were elicited from 48 infected and 50 uninfected persons. The cumulative prevalence of syphilis was 12.6%, and 24 persons infected with HIV were identified. Network methods disclosed a large, interconnected group (276 persons) characterized by high network centrality and the substantial presence of small, interactive subgroups (microstructures). CONCLUSION: The network approach is a feasible field technique, and can identify core groups involved in the intense transmission of syphilis. The targeted, network-based approach may be useful in attempts to eliminate syphilis.

Adult↗
PubMed2000

The disulfide bond pattern of catrocollastatin C, a disintegrin-like/cysteine-rich protein isolated from Crotalus atrox venom.

The disulfide bond pattern of catrocollastatin-C was determined by N-terminal sequencing and mass spectrometry. The N-terminal disintegrin-like domain is a compact structure including eight disulfide bonds, seven of them in the same pattern as the disintegrin bitistatin. The protein has two extra cysteine residues (XIII and XVI) that form an additional disulfide bond that is characteristically found in the disintegrin-like domains of cellular metalloproteinases (ADAMs) and PIII snake venom Zn-metalloproteinases (SVMPs). The C-terminal cysteine-rich domain of catrocollastatin-C contains five disulfide bonds between nearest-neighbor cysteines and a long range disulfide bridge between CysV and CysX. These results provide structural evidence for a redefinition of the disintegrin-like and cysteine-rich domain boundaries. An evolutionary pathway for ADAMs, PIII, and PII SVMPs based on disulfide bond engineering is also proposed.

Amino Acid Motifs↗