Search PubMed⌕ Search

Biomedical subjects

B Albrecht

Publications and source records attributed to B Albrecht.

At least 55 records · Page 3Linked to original sources
PubMed1994

A bifunctional control element in the human IgE germline promoter involved in repression and IL-4 activation.

One of the first steps during Ig heavy chain isotype switching to IgE is the IL-4 induced synthesis of IgE germline transcripts. To further characterize the molecular mechanism of the IL-4 action, the regulatory DNA elements involved in the control of expression of these transcripts were analyzed. Transient transfection of a B cell tumor line revealed the presence of a 15 bp IL-4 responsive cis-acting element (IL-4RE) highly homologous to an IL-4 response element in the human CD23b promoter. An IL-4 induced DNA binding protein specifically interacted with this sequence. Point mutations within that sequence not only abolished IL-4 inducibility of reporter constructs but also prevented binding of the nuclear factor to the mutated sequence. A stretch of 16 nucleotides just upstream of the IL-4RE contributed to IL-4 inducibility and formed nucleoprotein complexes with constitutive factors. All reporter constructs containing the functional IL-4RE were transcriptionally very weak but could be readily activated upon IL-4 induction. Transfection of constructs containing the mutated IL-4RE or plasmids lacking that sequence displayed a high constitutive promoter activity and were IL-4 unresponsive. These data suggest that in the absence of the cytokine the activity of the IgE germline promoter is actively repressed through the action of the IL-4RE. The same sequence appears to be critically involved in the IL-4 induced activation of the promoter via the binding of a cytokine induced transcription factor.

Base Sequence↗
PubMed1993

Chromosomal mapping in the mouse of eight K(+)-channel genes representing the four Shaker-like subfamilies Shaker, Shab, Shaw, and Shal.

The four Shaker-like subfamilies of Shaker-, Shab-, Shaw-, and Shal-related K+ channels in mammals have been defined on the basis of their sequence homologies to the corresponding Drosophila genes. Using interspecific backcrosses between Mus musculus and Mus spretus, we have chromosomally mapped in the mouse the Shaker-related K(+)-channel genes Kcna1, Kcna2, Kcna4, Kcna5, and Kcna6; the Shab-related gene Kcnb1; the Shaw-related gene Kcnc4; and the Shal-related gene Kcnd2. The following localizations were determined: Chr 2, cen-Acra-Kcna4-Pax-6-a-Pck-1-Kras-3-Kcn b1 (corresponding human Chrs 11p and 20q, respectively); Chr 3, cen-Hao-2-(Kcna2, Kcnc4)-Amy-1 (human Chr 1); and Chr 6, cen-Cola-2-Met-Kcnd2-Cpa-Tcrb-adr/Clc-1-Hox-1.1-Myk - 103-Raf-1-(Tpi-1, Kcna1, Kcna5, Kcna6) (human Chrs 7q and 12p, respectively). Thus, there is a cluster of at least three Shaker-related K(+)-channel genes on distal mouse Chr 6 and a cluster on Chr 2 that at least consists of one Shaker-related and one Shaw-related gene. The three other K(+)-channel genes are not linked to each other. The map positions of the different types of K(+)-channel genes in the mouse are discussed in relation to those of their homologs in man and to hereditary diseases of mouse and man that might involve K+ channels.

Animals↗
PubMed1993

Cloning and characterization of a human delayed rectifier potassium channel gene.

A human genomic DNA library was screened for sequences homologues to the rat delayed rectifier Kv 2.1 (DRK1) K+ channel cDNA. Three phages were isolated which hybridized to Kv 2.1 cDNA probes. Alignment of the human genomic DNA sequence with the rat cDNA sequence indicated that the open reading frame (ORF) is interrupted by a large intervening sequence, that separates exons encoding the membrane spanning core region of the K+ channel polypeptide. The Kv 2.1 gene occurs once in the human genome and has been mapped to chromosome 20. The human, mouse and rat Kv 2.1 proteins have been highly conserved, showing only a few substitutions outside of the membrane spanning domains in the amino- and carboxy-terminal cytoplasmic domains. Nevertheless, expression of human DRK1 channels in Xenopus oocytes showed that mouse, rat and human Kv 2.1 channels have distinct pharmacological and electrophysiological properties. The observed differences in activation, voltage-dependence, 4-aminopyridine sensitivity and single-channel conductance have to be attributed to amino acid substitutions in the amino-and/or carboxy-terminal cytoplasmic domains. Obviously, these domains of Kv 2.1 channels influence biophysical K+ channel properties, which are thought to be determined solely by the membrane spanning core domain of potassium channels.

Amino Acid Sequence↗
PubMed1992

Activation of protein kinase-C differentially regulates insulin-like growth factor-I and basic fibroblast growth factor messenger RNA levels.

Fibroblasts represent one of the in vivo sites of insulin-like growth factor-I (IGF-I) production. In this study rat dermal fibroblasts in culture were used as a model system to assess the effect of activation of protein kinase-C on the levels of the mRNAs encoding IGF-I and another growth factor, basic fibroblast growth factor (bFGF). IGF-I and bFGF mRNA levels were determined using a solution hybridization/RNase protection assay. Treatment of cells in serum-free medium containing 0.25% BSA (MEM + BSA) with the tumor-promoting phorbol ester phorbol 12-myristate 13-acetate (PMA) decreased IGF-I and increased bFGF mRNA levels in a time- and dose-dependent fashion. The peak effect of 100 nM PMA on IGF-I mRNA levels occurred at 9 h, whereas the peak effect on bFGF mRNA levels occurred after 3 h of incubation. In dose-response studies, half-maximal inhibition of IGF-I mRNA levels was achieved with approximately 0.08 nM PMA, while half-maximal stimulation of bFGF mRNA levels was achieved with approximately 3 nM PMA. Inhibition of protein synthesis with cycloheximide abrogated the effect of PMA on bFGF mRNA levels, but only partially inhibited the effect of PMA on IGF-I mRNA levels. Studies employing sphingosine or staurosporine to inhibit protein kinase-C or preincubation in high doses of PMA to down-regulate protein kinase-C suggested that the effect of PMA on IGF-I and bFGF mRNA levels was mediated by activation of protein kinase-C, although both staurosporine and sphingosine had independent effects on the levels of these mRNAs and down-regulation of protein kinase-C had a sustained effect on IGF-I mRNA levels. Ligands known to activate protein kinase-C were then tested. Treatment of cells with 100 micrograms/ml of the synthetic diacylglycerol 1-oleoyl-2-acetyl-sn-glycerol decreased IGF-I mRNA levels to 25% and increased bFGF mRNA levels to 520% of the level present in cells maintained in MEM + BSA. Treatment of cells with thrombin or bradykinin also decreased IGF-I mRNA levels and increased bFGF mRNA levels, but whereas the effect of thrombin on IGF-I mRNA levels was marked, the effect of bradykinin was minimal, and whereas the effect of thrombin on bFGF mRNA levels was sustained, the effect of bradykinin was transient.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

In vivo utilization of N-(phosphonomethyl)-anilines and related substances by Pseudomonas spec. GS.

Utilization of various phosphonates as source for phosphorus by the glyphosate degrading strain Pseudomonas spec. GS was investigated. Metabolites of phosphonate degradation were characterized indicating the cleavage of the C-P-bound as primary step of breakdown. The phosphonate N-(phosphonomethyl)-4'-nitroazobenzene-4-amine (azophon) was characterized as a suitable substrate for detection of C-P-bond splitting activity in vivo. Pseudomonas cells permeabilized by toluene treatment were also capable of phosphonate degradation whereas no in vitro activity of a putative C-P-bond cleaving enzyme was detectable after cell disruption.

Aniline Compounds↗
PubMed1990

[Glyphosate utilization by Pseudomonas spec. GS].

Pseudomonas spec. GS grown in the presence of 14C-labelled glyphosate metabolizes the herbicide to inorganic phosphate as well as in respect of utilization of the C-skeleton. Furthermore it was shown that the primary step of degradation is the breakdown of the C-P-bond, because sarcosine was found as a transient metabolite.

Amino Acids↗
PubMed1989

1,25-Dihydroxyvitamin D3 prevents the decrease of bone mineral appositional rate in rats with inflammation-mediated osteopenia (IMO).

We have studied the effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on bone mass and bone mineral appositional rate in intact rats and rats with inflammation-mediated osteopenia (IMO), where osteoblast number and mineral appositional rate are decreased. 1,25(OH)2D3 prevents IMO-specific bone loss when given in a daily dose of 25 ng per rat, but does not when given in higher doses. The hormone was effective, when given over the complete duration of the experiment (21 days), but not when given over shorter time periods (7 and 14 days, respectively). 1,25(OH)2D3 prevents IMO-dependent reduction in mineral appositional rate and leads to an only moderate increase in intact rats. We conclude, that 1,25(OH)2D3 is more effective in stimulating mineral appositional rate in rats with IMO where mineral apposition is impaired.

Animals↗
PubMed1987

The relationship of tubal infertility to barrier method and oral contraceptive use.

We studied past contraceptive use in 283 nulliparous infertile women who had a diagnosis of tubal adhesions or occlusion and in 3833 women admitted for delivery at seven collaborating hospitals from 1981 to 1983. The relative risk of tubal infertility associated with barrier contraceptive use or oral contraceptive use was calculated using multivariate logistic regression to control for confounding by region, age, religion, education, smoking, number of sexual partners, time since menarche, and use of other contraceptive methods. Women who had ever used barrier methods of contraception were at a significantly decreased risk of tubal infertility (relative risk = 0.6; 95% confidence limits, 0.5 and 0.8). When type of barrier method used for the longest time was evaluated, those who used the diaphragm or condoms plus spermicides were at lower risk than those who used condoms or spermicides alone. Overall, past use of oral contraceptives neither increased nor decreased a woman's risk of tubal infertility, but there was evidence that the association between oral contraceptives and tubal infertility may vary by the amount of estrogen and type of progestogen in the oral contraceptive used. We conclude that contraceptive users who use barrier methods that combine both a mechanical and chemical barrier, such as diaphragms, cervical caps, and condoms plus spermicides, have the clearest protection against tubal damage.

Adult↗
PubMed1987

The association between smoking and female infertility as influenced by cause of the infertility.

Smoking histories were compared in 901 women with infertility of different types and 1264 women admitted for delivery at seven collaborating hospitals. The relative risk for infertility associated with cigarette smoking prior to the infertility diagnosis for nulliparous cases or first live birth for controls was calculated using a multivariate logistic-regression model to control for potential confounding factors, including center, age, religion, education, number of sexual partners, and contraceptive use. The adjusted risk for infertility attributed primarily to cervical factor (n = 96) was 1.7 (P = 0.04), to tubal disease unrelated to endometriosis (n = 225) was 1.6 (P = 0.009), to ovulatory factor (n = 389) was 1.0 (not significant [NS]), and to endometriosis (n = 191) was 0.9 (NS). The authors conclude that cigarette smoking is significantly associated only with certain types of primary female infertility.

Adult↗
PubMed1986

The relation of endometriosis to menstrual characteristics, smoking, and exercise.

We compared menstrual characteristics and constitutional factors in 268 white women with primary infertility due to endometriosis and in 3,794 white women admitted for delivery at seven collaborating hospitals from 1981 to 1983. Adjusting for confounding factors, including location, age, religion, and education, women with short-cycle lengths (less than or equal to 27 days) and longer flow (greater than or equal to one week) had more than double the risk for endometriosis compared with women with longer cycle lengths and shorter duration of flow. There was a trend for increasing risk for endometriosis to be associated with increasing menstrual pain. Adjusting for these menstrual characteristics, we found decreased risk for endometriosis associated with smoking or exercise that was largely confined to women who began either habit at an early age and were heavier smokers or more strenuous exercisers. We conclude that risk for endometriosis may relate to menstrual factors that predispose to greater pelvic contamination with menstrual products and to constitutional factors that influence endogenous hormonal levels.

Adolescent↗
PubMed1985

Tubal infertility and the intrauterine device.

To study the association between intrauterine devices (IUDs) and pelvic inflammatory disease, we compared contraceptive histories in 4185 while women--283 nulliparous women with primary tubal infertility, 69 women with secondary tubal infertility, and 3833 women admitted for delivery at seven collaborating hospitals from 1981 to 1983. The relative risk of tubal infertility associated with IUD use was calculated by means of multivariate logistic regression to control for confounding factors, including region, year of menarche, religion, education, smoking, and reported number of sexual partners. The adjusted risk of primary tubal infertility associated with any IUD use before a first live birth was 2.0 (95 per cent confidence limits, 1.5 to 2.6) relative to nonuse. Users of the Dalkon Shield had an adjusted risk of 3.3 (1.7 to 6.1), users of the Lippes Loop or Saf-T-Coil had a risk of 2.9 (1.7 to 5.2), and users of copper IUDs had a risk of 1.6 (1.1 to 2.4). Women who reported having only one sexual partner had no increased risk of primary tubal infertility associated with IUD use. The adjusted risk of secondary tubal infertility associated with use of a copper IUD after a first live birth was not statistically significant (1.5; 95 per cent confidence limits, 0.8 to 3.0), whereas the risk from similar use of noncopper devices was significant (2.8; 1.3 to 5.9). We conclude that tubal infertility is associated with IUD use, but less so with copper IUDs.

Adult↗
PubMed1984

Collaborative study of pregnancy rates following danazol therapy of stage I endometriosis.

Pregnancy rates following danazol therapy of endometriosis vary widely. In order to reduce variations in patient selection and establish danazol effectiveness, six collaborative centers evaluated 75 infertile patients with normal infertility screening studies and mild (stage I) endometriosis documented by laparoscopy. Following diagnosis and 3 months coital exposure, all patients were treated with danazol for 6 months, and patient surveillance after danazol therapy lasted at least 12 months, with a range of 12 to 34 months. Of the 75 patients treated, 21 (28%) conceived, and the term pregnancy rate was 20% (15 of 75). The low pregnancy rate observed in these patients suggests that the role of danazol therapy for patients with mild endometriosis and infertility should be reconsidered.

Adult↗