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Biomedical subjects

B Fischer

Publications and source records attributed to B Fischer.

At least 73 records · Page 4Linked to original sources
PubMed2001

Molecular remodeling of members of the relaxin family during primate evolution.

Employing comparative analysis of the cDNA-coding sequences of the unique preprorelaxin of the Afro-lorisiform Galago crassicaudatus and the Malagasy lemur Varecia variegata and the relaxin-like factor (RLF) of G. crassicaudatus, we demonstrated distinct differences in the dynamics of molecular remodeling of both hormones during primate evolution. The lorisiform and lemuriform preprorelaxin sequences encoded identical hormones, providing the first endocrinological evidence for the monophyletic origin of all Strepsirrhini. Structural analysis revealed the lemuriform members of the relaxin family to be potentially bioactive single-gene products. In contrast to the "two-prong" relaxin receptor-binding motif (RELVR) present within the B-domains of other primate relaxins, strepsirrhine relaxin contained a unique "three-prong" motif (RRLIR) with highest sequence homology to the receptor-binding motif of the evolutionarily much older skate relaxin. In contrast to relaxin, the RLF molecule was highly conserved during primate evolution and contained within its B-domain the putative relaxin receptor-binding motif and a pentameric sequence implicated in binding to specific RLF receptors. Mutually exclusive expression of strepsirrhine preprorelaxin and RLF were observed in the fetal villous trophoblast cells of the strepsirrhine placenta and postpubertal testicular Leydig cells, respectively, reflecting distinct functional roles for both hormones within the reproductive tract of Strepsirrhini.

Amino Acid Sequence↗
PubMed2001

Canine relaxin-like factor: unique molecular structure and differential expression within reproductive tissues of the dog.

Employing postpubertal testicular tissue, we determined the cDNA coding sequence of a truncated canine relaxin-like factor (RLF) consisting of a signal peptide of 28 amino acids (aa), a B-domain of 23 aa, a truncated C-domain of 34 aa, and an A domain of 26 aa, respectively. Within the B-domain of canine RLF, the putative relaxin receptor binding motif contained a single substitution with the C-terminal arginine replaced by a serine residue, and the putative RLF receptor binding motif was truncated. Leydig cells specifically expressed RLF in the normal postpubertal and cryptochid testis as well as in testicular Leydig cell adenoma. The epididymis was an additional source of RLF in the dog. In the female reproductive tract, expression of immunoreactive RLF and relaxin were compared. Within the ovary, RLF, but not relaxin, was detected in follicular theca interna and granulosa cells and the corpus luteum. In the nonpregnant uterus, luminal and glandular epithelium coexpressed RLF and relaxin. Uteroplacental tissue at early stages of gestation revealed RLF expression in the proliferative fetal villous cytotrophoblast and in maternal uterine cells. In the mature canine placenta, the trophoblast surrounding the maternal blood vessels and the hemophagous cytotrophoblast of the paraplacental zone expressed RLF. Canine relaxin was absent in the paraplacental areas. Western analysis of placental tissue extracts revealed the presence of specific immunoreactive bands likely resembling unprocessed and enzymatically cleaved RLF. Differential expression of RLF and relaxin appears to reflect distinct autocrine and paracrine functions of RLF in canine reproductive tissues.

Amino Acid Sequence↗
PubMed2001

Epidermal growth factor-like ligands and erbB genes in the peri-implantation rabbit uterus and blastocyst.

Molecular cloning of the partial cDNA coding sequences of the four erbB receptors and the epidermal growth factor (EGF)-like ligands EGF, transforming growth factor alpha (TGF), and heparin-binding EGF (HB-EGF) has provided the basis for a comprehensive analysis of the spatiotemporal expression pattern of the EGF receptor/ligand system during the peri-implantation period in the rabbit. Employing nonradioactive in situ hybridization and immunolocalization, we observed differential expression of erbB1-erbB3 within the trophectoderm of the blastocyst. ErbB1 was strongly expressed in the cytotrophoblast but was downregulated upon syncytium formation. ErbB3 was a product of both the cyto- and syncytiotrophoblast. Despite the expression of erbB2 mRNA, the trophectoderm was devoid of immunoreactive ErbB2. ErbB4 gene activity was exclusively detected in the trophoblast at midpregnancy. The luminal and glandular epithelium and stroma of the nonpregnant, pseudopregnant, and pregnant rabbit uterus at Day 6 of gestation also expressed ErbB1-ErbB3. In the peri-implantation period, gene activities of erbB1-erbB3 were upregulated upon decidualization. At the site of implantation, uterine luminal epithelial cells apposing the preimplantation blastocyst displayed a distinct membrane immunolocalization of ErbB2, identifying the uterine epithelium as target for EGF, TGFalpha, and HB-EGF derived from both the embryonic trophectoderm and the uterine epithelium. In the luminal epithelium at the antimesometrial uterine site, HB-EGF gene activity was upregulated at the time of blastocyst attachment, but this upregulation was not reflected in an increase in immunoreactive HB-EGF. The detection of tyrosine phosphorylated ErbB2 in the rabbit placenta indicated the presence of a functional ErbB/EGF-like system in the pregnant rabbit uterus. This study provides strong evidence for a role of the ErbB/EGF-like system in embryo/maternal interactions during the peri-implantation period in the rabbit.

Animals↗
PubMed2000

Relaxin-like factor (RLF) is differentially expressed in the normal and neoplastic human mammary gland.

BACKGROUND: Expression of relaxin-like factor (RLF), a member of the relaxin family, was studied in normal, benign, and malignant neoplastic human breast tissue. METHODS: Reverse transcription polymerase chain reaction (RT-PCR) and nonradioactive in situ hybridization were employed to detect RLF transcripts. RLF epitopes were detected with a rabbit polyclonal antiserum generated against the putative receptor binding domain of human RLF. The RLF antiserum was characterized by Western blot analysis on human testicular and placental tissues, recombinant glutathione S-transferase-RLF fusion protein, and baculovirus-derived recombinant marmoset-RLF and marmoset-relaxin. RESULTS: RT-PCR analysis revealed RLF amplicons in a cDNA library of normal human breast tissue and in malignant neoplastic breast tissue. RLF hybridization signals were localized exclusively in the tubuloalveolar and ductal breast epithelium but were absent in stromal cells. Benign breast disease displayed weaker RLF hybridization signals compared with normal tubuloalveolar breast tissue. Malignant transformation of breast epithelial tissues resulted in down-regulation of RLF gene expression. The weakest expression of RLF mRNA was observed in lymph node metastases of corresponding primary ductal carcinomas. Immunoreactive RLF was exclusively expressed in breast epithelial cells. Despite strong RLF hybridization signals, the tubuloalveolar epithelial cells of normal breast tissue displayed only very weak immunoreactive RLF. Benign breast disease showed clearly detectable levels of both RLF mRNA and immunoreactive protein. In contrast, epithelial cells in breast carcinoma and lymph node metastases displayed strong expression of immunoreactive RLF, although expression of RLF transcripts was weak. CONCLUSIONS: Results demonstrated that transcriptional and posttranscriptional mechanisms affected human RLF gene expression in normal and neoplastic epithelial breast cells.

Animals↗
PubMed2000

Consideration of a North American heroin-assisted clinical trial for the treatment of opiate-dependent individuals.

Untreated opiate addiction remains a major public health problem in North America (US and Canada). Increased morbidity and mortality as well as criminal behavior related to untreated opiate dependence constitute significant social and economic burdens. While the principal treatment modality to opiate addiction in North America has been methadone treatment since the 1960s, its reach and effectiveness has been limited; at any given time, only about 25% (US) and 15-20% (Canada) of all opiate addicts are in methadone treatment. Reasons for low levels of treatment participation among this subset of users include perceptions among users that treatment programs are punitive and that the medication is fraught with side effects. In the meantime, alternatives to methadone have been recently approved or are in development, including levo-alpha acetylmethadol and buprenorphine. However, the extent to which they will solve the current problem is still unknown, and therefore development of additional treatment strategies needs to continue. Recent studies of heroin-assisted treatment in Europe (Switzerland, the Netherlands and Great Britain) produced preliminary yet encouraging results in attracting and retaining long-term, treatment-resistant addicts in treatment, as well as improving treatment outcomes. However encouraging, the North American context differs from Europe. A study performed in North America would provide critical information on whether utilizing injectable opiates enhances the overall therapeutic attractiveness and effectiveness of substance abuse treatment to a subset of recalcitrant users. Implications of positive results would expand the continuum of effective interventions in the US and Canada, and increase the number of long-term, treatment-resistant opiate addicts in treatment.

Journal Article↗
PubMed2000

Novel inhibitors of nucleoside triphosphate diphosphohydrolases: chemical synthesis and biochemical and pharmacological characterizations.

To elucidate the physiological role played by nucleoside triphosphate diphosphohydrolase (NTPDase; EC 3.6.1.5), adenine nucleotide analogues, modified on the purine ring, have been synthesized and tested as potential inhibitors. Resistance of ATP analogues to hydrolysis and their potency as NTPDase inhibitors were evaluated. For this purpose, a particulate fraction isolated from bovine spleen was used as the enzyme source. Among the synthesized analogues, 8-thiobutyladenosine 5'-triphosphate (8-BuS-ATP) was found to be the most effective nonhydrolyzable competitive inhibitor, with an estimated K(i) of 10 microM. This nonhydrolyzable analogue did not exert any P2X-receptor-mediated effect on endothelium-denuded blood vessels, from the guinea pig mesenteric bed. In agreement with this observation, infusion of the analogue did not cause any significant blood pressure variations of the precontracted vessel. Because in previous studies on isolated turkey erythrocytes and rat astrocytes 8-BuS-ATP was not able to trigger any P2Y(1)-receptor-mediated effect, it therefore appears that this NTPDase inhibitor does not interfere with purinergic receptors.

Adenosine Triphosphate↗
PubMed2000

The insulin-dependent glucose transporter isoform 4 is expressed in bovine blastocysts.

We have investigated the expression of two glucose transporter isoforms, Glut1 and 4, in 14- and 16-day-old bovine blastocysts (d14, d16) using RT-PCR, competitive RT-PCR and in situ hybridization. The blastocysts were grown in vivo or had been produced in vitro. Glut1 mRNA was detected in all blastocysts studied, Glut4 in all d14 blastocysts, but only in a few d16 blastocysts. Glut4 mRNA was localized in trophoblast and endoderm cells. Glut1 mRNA increased from d14 to d16 while Glut4 transcription was down-regulated in d16 blastocysts. The mRNA amounts varied between 0.8 to 23 pg and 3.9 to 65 fg per 100 ng embryonic RNA for Glut1 and Glut4, respectively, displaying a 100- to 1500-fold lower expression of Glut4 compared with Glut1 during blastocyst elongation. This is the first report on the expression of the insulin-sensitive Glut4 isoform in mammalian preimplantation embryos.

Animals↗
PubMed2000

Dynamics of surface migration in the weak corrugation regime

We report a systematic study for metal-on-metal surface migration in the weak corrugation regime, i.e., with migration barriers falling below approximately 100 meV. The migration characteristics are elucidated by variable-temperature scanning tunneling microscopy observations in the 50-200 K temperature range, which are analyzed by means of nucleation theory. The results demonstrate that, upon entering the weak corrugation regime, the dynamics of the systems are characterized by increasingly reduced effective preexponential factors, while Arrhenius behavior prevails.

Journal Article↗
PubMed2000

Relaxin-like factor (RLF) mRNA expression in the fallow deer.

Employing RT- and RACE-PCR on RNA isolated from testicular tissue, we have cloned the coding cDNA sequence for the RLF, also known as Insl3, of the fallow deer. The RLF coding sequence consisted of 396 bp encoding a peptide of 131 amino acids and shared highest homology with bovine, sheep and goat RLF. Northern analysis revealed a single 0.9 kb transcript in the deer testis. There is only one RLF gene in the deer genome. Nonradioactive in situ hybridization revealed the Leydig cells to be the sole source for RLF mRNA in the deer testis. In the non-pregnant uterus, RLF transcripts were located in the luminal and glandular epithelium of the endometrium. Within the ovary of the pregnant doe, follicular theca interna cells and the corpus luteum expressed RLF transcripts. In uteroplacental tissues, luminal and glandular epithelium, fetal uninucleate and binucleate trophoblast cells (BNC) of the basic villous trophoblast layer expressed RLF mRNA. BNC located at the apical trophoblast layer or the tip of the fetal villus were devoid of RLF transcripts. Pseudostratified trophoblast cells at the base of fetal villi coexpressed RLF mRNA and immunoreactive MHC class Ib molecules.

Amino Acid Sequence↗
PubMed2000

Ten novel BRCA1 and BRCA2 mutations in breast and/or ovarian cancer families from northern Germany.

Germline mutations in the BRCA1 and BRCA2 gene account for the majority of high-risk breast/ovarian cancer families. We have screened such families from Northern Germany by using DHPLC analysis and subsequent direct sequencing techniques. In ten families we identified six novel BRCA1 and 4 novel BRCA2 mutations comprising four frame shift mutations, one nonsense and one splice site mutation in the BRCA1 gene as well as three frameshift mutations and one nonsense mutation in the BRCA2 gene. Our analysis contributes to the further characterisation of the mutational spectrum of BRCA1 and BRCA2.

Adult↗
PubMed2000

Acidic pH inhibits non-MHC-restricted killer cell functions.

Immunotherapeutic strategies in advanced stages of solid tumors have generally met with little success. Various mechanisms have been discussed permitting the escape of tumor cells from an effective antitumoral immune response. Solid tumors are known to develop regions with acidic interstitial pH. In a recent study performed in the human system, we were able to demonstrate that non-MHC-restricted cytotoxicity is inhibited by an acidic microenvironment. To get more insight into the mechanisms leading to this reduced cytotoxic activity, we have now investigated the influence of an acidic extracellular pH (pH(e)) on the killing process in detail. Unstimulated PBMC and LAK cells were used as effector cells. Both populations are able to kill tumor cells in a MHC-independent manner via perforin/granzymes or TNFalpha, whereas only IL-2-activated cells can use the killing pathway via Fas/FasL. We studied the influence of a declining pH(e) on the different killing pathways against TNFalpha-sensitive and -resistant, as well as Fas-positive and -negative, target cells. Experiments in the absence of extracellular Ca(2+) were used to discriminate the Ca(2+)-dependent perforin-mediated killing. Here we show that the release of perforin/granzyme-containing granules, the secretion of TNFalpha, and also the cytotoxic action of Fas/FasL interaction or of membrane-bound TNFalpha were considerably inhibited by declining pH(e). Furthermore, the secretion of the activating cytokine IFNgamma, as well as the release of the down-regulating cytokines IL-10 and TGF-beta(1), was strictly influenced by surrounding pH. As a pH(e) of 5.8 resulted in a nearly complete loss of cytotoxic effector cell functions without affecting their viability, we investigated the influence of pH(e) on basic cellular functions, e.g. , mitochondrial activity and regulation of intracellular pH. We found an increasing inhibition of both functions with declining pH(e). Therefore, an acidic pH(e) obviously impairs fundamental cellular regulation, which finally prevents the killing process. In summary, our data show a strict pH(e) dependence of various killer cell functions. Thus, an acidic microenvironment within solid tumors may contribute to the observed immunosuppression in vivo, compromising antitumoral defense and immunotherapy in general, respectively.

Acids↗
PubMed2000

Social costs of untreated opioid dependence.

Using cost-of-illness methodology applied to a comprehensive survey of 114 daily opiate users not currently in or seeking treatment for their addiction, we estimated the 1996 social costs of untreated opioid dependence in Toronto (Ontario, Canada). The survey collected data on social and demographic characteristics, drug use history, physical and mental health status, the use of health care and substance treatment services, drug use modality and sex-related risks of infectious diseases, sources of income, as well as criminality and involvement with the law enforcement system. The annual social cost generated by this sample, calculated at Canadian $5.086 million, is explained mostly by crime victimization (44.6%) and law enforcement (42.4%), followed by productivity losses (7.0%) and the utilization of health care (6.1%). Applying the $13,100 cost to the estimated 8,000 to 13,000 users and 2.456 million residents living in Toronto yields a range of social cost between $43 and $69 per capita.

Cost of Illness↗
PubMed2000

Optomotor and neuropsychological performance in old age.

While a delayed initiation of visually guided saccades with increasing age has been documented in a number of studies, little research has been done on the control of antisaccades. The present study investigates aging effects on the control of visually guided saccades (prosaccades) and antisaccades as well as a selection of neuropsychological functions by the cross-sectional comparison of 14, 22, and 16 participants aged 20-35 years, 59-73 years, and 74-88 years, respectively. The geriatric and neurological status of the elder participants (including evidence from computed tomography, electroencephalography, and neurological soft signs) was assessed. In four task blocks of 200 trials each, pro- and antisaccades were elicited under the 200-ms-gap and overlap conditions. Left- and right-sided stimuli were presented in random order at 4 degrees, and the order of the task blocks was varied within each age group. In addition, the Wisconsin card-sorting test (WCST) and working memory, go-nogo discrimination, alertness, and stimulus-response incompatibility tests were administered. Participants aged 59-73 years exhibited widespread reductions of optomotor and neuropsychological performance, with greatest effect sizes of age differences in the optomotor parameters and the WCST measures. A further decay after the age of 73 years was discernible in those optomotor functions reflecting saccade disinhibition (in particular, directional errors during the antisaccade task and premature responses) and the performance in some neuropsychological tests. In line with previously published reports, variance in optomotor performance could be explained by two factors, accounting for a total of 76% of the age variance. Our results suggest that the investigation of saccade control may be a highly sensitive tool for neurodevelopmental aging research.

Adult↗
PubMed2000

Expression of proto-oncogenes in bovine preimplantation blastocysts.

Proto-oncogenes are involved in the regulation of gene expression, for example after ligand binding to growth factor receptors. Expression of the proto-oncogenes c-fos, c-jun, c-ha-ras and c-myc was studied in in vivo grown and in vitro cultured bovine preimplantation blastocysts employing RT-PCR, ribonuclease protection assay and immunohistochemistry. Thirteen- and 14- day-old preimplantation blastocysts, i.e. stages before and during trophoblast elongation, were used. In in vivo-grown blastocysts c-fos, c-jun and c-ha-ras transcripts as well as c-Fos, c-Jun and c-Myc proteins were detected in all stages studied. Cultured blastocysts were treated with 10 nM epidermal growth factor and 10 nM transforming growth factor-alpha simultaneously. Epidermal growth factor and transforming growth factor-alpha treatment induced c-fos mRNA and c-Myc protein expression. The induction of downstream targets of the epidermal growth factor receptor by epidermal growth factor and transforming growth factor-alpha indicates a functional epidermal growth factor signal transduction pathway in elongating bovine blastocysts.

Animals↗
PubMed2000

Ultrasonic characterization of liquids using resonance antireflection

This paper presents an ultrasonic method for measuring the density of liquids with a solid layer separating a reference fluid and a test fluid. By adjusting the frequency of the exciting signal according to the thickness of the layer, it is possible to generate destructive interference of the waves reflected at the first and at the second boundary of the layer. Thus, the layer appears to vanish for the incident waves. The resulting echo signal depends only on the acoustic impedances of the reference fluid and the test fluid and the density which is of interest can be extracted. Short and long-term drifts of the electronics and the ultrasonic transducer implied are eliminated by using the well-known pulse-echo technique with additional frontwave detection.

Journal Article↗
PubMed2000

On the production and correction of involuntary prosaccades in a gap antisaccade task.

In an antisaccade task, where saccades in the direction opposite of a suddenly presented stimulus are required, certain numbers of prosaccades can occur. The hypothesis is put forward that poor fixation and poor voluntary saccade control constitute two independent sources for the errors. This possibility is investigated by including the corrections of the errors in the analysis. First, the eye movements of 346 normal subjects (group N) performing a gap antisaccade and an overlap prosaccade task were measured. For each subject the proportion of express saccades in the overlap prosaccade task and the proportion of prosaccades in the gap antisaccade task were determined. The data of 150 subjects with more than 20% proerrors were divided into two groups: group A with relatively many, group B with relatively few express saccades in the overlap prosaccade task. Group A subjects produced their errors after significantly shorter reaction times and they corrected their errors significantly faster and more often than group B subjects. Second, we analysed the data of three groups of subjects: the complete normal group N, a group D of dyslexic subjects (n=343), and a group T containing all subjects irrespective of their cognitive achievements (n=780). A highly significant negative correlation exists between the correction rates and the error rates. A factor analysis of the variables performed for each group separately results in only two factors, one describing prosaccade the other antisaccade control. Only the error rate contributes significantly to both factors indicating that high errors may have two independent reasons.

Adolescent↗