Biomedical subjects
Publications and source records attributed to G Sturm.
For the first time, we describe the detection of hyperfine transitions in zero magnetic field using field-cycling techniques and pulsed EPR spectroscopy. The sample investigated was coal, which shows an anisotropic electron spin-(13)C hyperfine interaction.
p38, a subfamily of the mitogen-activated protein kinases (MAPKs), is a crucial signal transducer between a variety of extracellular stimuli and gene expression in mammalian cells. This kinase is activated in cultured cells stimulated by heat shock, osmotic stress, and proinflammatory cytokines, but a similar activation of p38 MAPKs in vascular smooth muscle cells (SMCs) stimulated by mechanical stress has yet to be studied. We studied signal pathways leading to time- and strength-dependent p38 activation in rat SMCs in response to cyclic strain stress. p38 phosphorylation in stressed SMCs showed maximal activation at 10 minutes. This activation was significantly inhibited by pretreatment of the SMCs with pertussis toxin, a G-protein antagonist, and enhanced by treatment with suramin, a growth factor receptor antagonist, but opposite effects in the activation of extracellular signal-regulated kinases stimulated by mechanical forces were found. p38 activation was markedly reduced in stressed SMCs after protein kinase C depletion. Interestingly, SMC lines stably expressing dominant-negative ras (ras N17) or rac1 (rac1 N17) almost abolished p38 phosphorylation induced by cyclic strain stress. When p38 activation was inhibited by the specific inhibitor SB 202190, SMC migration, determined in a Boyden chamber in response to stimulation with platelet-derived growth factor-BB, and SMC proliferation, stimulated by cyclic strain stress, were abrogated. Thus, we provide the first evidence that cyclic strain stress rapidly activates p38 MAPKs via activation of protein kinase C ras/rac signal pathways, suggesting that p38 MAPKs are important signal transducers mediating the mechanical stress-induced cell responses essential for SMC migration and proliferation.
OBJECTIVE: To evaluate the impact of long-term, non-suppressive levothyroxine (L-T(4)) treatment on quantitative ultrasonometry in women. DESIGN: This was a case-control study. SUBJECTS AND METHODS: Altogether 667 women (mean age+/-s.d., 49.5+/-13.1 years) were studied. Of these, 156 (23%) had non-toxic goitre or hypothyroidism and had been taking L-T(4) (75-100 microg/day) for at least 5 years (mean+/-s.d., 12.5+/-7.5 years); the remaining 511 (77%) women were not receiving L-T(4). All women had completed a questionnaire on risk factors for thyroid dysfunction and osteoporosis, and those with diseases or treatments known to effect bone metabolism - other than thyroxine or hormone replacement therapy (HRT) - were excluded. Women underwent quantitative ultrasonometry (QUS) at the heel. Speed of sound (SOS), broadband ultrasound attenuation (BUA) and the stiffness index (SI) were compared, first, in all women taking L-T(4) and controls and, secondly, in women taking L-T(4) and controls pair-matched for age, weight, body mass index (BMI), menopausal status and HRT use. RESULTS: Even after matching for age, weight, BMI, menopausal and HRT status, women taking L-T(4) had significantly lower values for SOS and SI (P<0.05), but not for BUA. However, absolute T- and Z-scores for SI were not low in either the study or control groups. Lower values were associated, but not significantly so, with years since the menopause and duration of L-T(4) treatment. CONCLUSIONS: Long-term, non-suppressive L-T(4) treatment in women with goitre or hypothyroidism was associated with a slight reduction in QUS values, which was more pronounced in postmenopausal women. This group could be at higher risk for osteoporotic fracture.
OBJECTIVE: The aim of this study was to evaluate the influence of menopausal status, serum estradiol and body mass index (BMI) on serum leptin concentration in a large sample of pre- and postmenopausal women. DESIGN: 434 healthy women (mean age +/-s.d., 52.2 +/- 10.3 years) were recruited at the University of Marburg on the occasion of a routine gynecological visit. Two hundred and eighteen (50.2%) women were premenopausal (mean age, 36.5 +/- 10.4 years) and not on oral contraceptives or hormone replacement therapy (HRT) and 216 (49.8%) women were postmenopausal (mean age 61.8 +/- 8.9 years) not on HRT. To evaluate the influence of menopausal status, estradiol level and BMI on serum leptin concentrations, women were allocated to one of the four groups: (a) premenopausal women BMI <25 kg/m(2) (n=137), (b) premenopausal women BMI >25 kg/m(2) (n=81), (c) postmenopausal women BMI <25 kg/m(2) (n=94) and (d) postmenopausal women BMI >25 kg/m(2) (n=122). RESULTS: Irrespective of the menopausal status, women with a BMI >25 kg/m(2) had significantly higher leptin concentrations in all age groups compared with women with a BMI <25 kg/m(2) (P<0.001). The multiple linear regression analyses showed that BMI was the only statistically significant independent predictor for leptin. In comparison to postmenopausal women, premenopausal women showed a significantly lower mean age, weight, BMI and FSH concentration (P<0. 001), a higher mean height and serum estradiol (P<0.01 and P<0.001 respectively) but significantly lower serum leptin concentration (P<0.01). The multiple linear regression model showed no significant influence of menopausal status or serum estradiol on serum leptin concentration, even after controlling for BMI. CONCLUSIONS: Serum leptin concentrations are significantly higher in pre- and postmenopausal obese women, compared with normal weight controls. Serum leptin concentrations are not influenced by menopausal status or serum estradiol level.
Leptin plays an important role in reproductive function. In patients with acute anorexia nervosa, serum leptin levels have repeatedly been shown to be lower than in age-matched controls. We have previously hypothesized that the amenorrhea characteristic of anorexia nervosa is related to this low leptin secretion. In an attempt to address this hypothesis, serum levels of leptin and follicle stimulating hormone (FSH) and luteinizing hormone (LH) of 16 female inpatients with anorexia nervosa or an eating disorder not otherwise specified (atypical anorexia nervosa) were measured on a biweekly basis during weight gain. We hypothesized that a serum leptin level of 1.85 microg L(-1) would be associated with gonadotropin levels at or above the minimal level observed during the menstrual cycle in healthy adult fertile females. Our results revealed that increments of LH levels generally tracked increments of leptin levels during the first weeks of treatment. Similarly, in those patients with low referral leptin levels, FSH initially also tracked leptin levels. In contrast, a relationship between gonadotropin levels and leptin secretion was no longer discernible after LH and FSH levels had peaked. Those patients with exceedingly low leptin levels upon admission revealed a slow increase of gonadotropin levels. Our hypothesis of a threshold leptin level of 1.85 microg L(-1) was supported for LH only.
Low density lipoprotein (LDL) is a well-established risk factor for atherosclerosis, stimulating vascular smooth muscle cell (SMC) differentiation and proliferation, but the signal transduction pathways between LDL stimulation and cell proliferation are poorly understood. Because mitogen-activated protein kinases (MAPKs) play a crucial role in mediating cell growth, we studied the effect of LDL on the induction of MAPK phosphatase-1 (MKP-1) in human SMCs and found that LDL stimulated induction of MKP-1 mRNA and proteins in a time- and dose-dependent manner. Heparin, inhibiting LDL-receptor binding, did not influence LDL-stimulated MKP-1 mRNA expression, and human LDL also induced MKP-1 expression in rat SMCs and fibroblasts derived from LDL receptor-deficient mice, indicating an LDL receptor-independent process. Pretreatment of SMCs with pertussis toxin markedly inhibited LDL-induced MKP-1 expression. Depletion of protein kinase C (PKC) by phorbol 12-myristate 13 acetate or inhibition of PKC by calphostin C blocked MKP-1 induction, but the phospholipase C inhibitor U73122 had no effect. Pretreatment of SMCs with genistein or herbimycin A abrogated LDL-stimulated MKP-1 induction. The MAPK kinase inhibitor PD98059 abolished LDL-stimulated activation of extracellular signal-regulated protein kinases (ERKs) but not MKP-1 induction. Furthermore, constitutive expression of MKP-1 in vivo reduced LDL-induced expression of Elk-1-dependent reporter genes, and SMC lines overexpressing recombinant MKP-1 exhibited decreased ERK activities and retarded proliferation in response to LDL. Our findings demonstrate that LDL induces MKP-1 expression in SMCs via activation of PKC and tyrosine kinases, independent of LDL receptors and ERK-MAPKs, and that MKP-1 plays an important role in the regulation of LDL-initiated signal transductions leading to SMC proliferation.
Arachidonic acid (AA) and its metabolites play important roles in a variety of biological processes, such as signal transduction, contraction, chemotaxis, and cell proliferation and differentiation. It was demonstrated recently that AA can activate mitogen-activated protein kinases (MAPKs), which are crucial for transducing signals initiating cell growth and apoptosis. Here we studied the effect of AA on the induction of MAPK phosphatase-1 (MKP-1) in vascular smooth muscle cells (VSMCs) and found that AA stimulated induction of MKP-1 mRNA and proteins in VSMCs in a time- and dose-dependent manner. Specific inhibitors of cyclooxygenase-, lipoxygenase-, and cytochrome P450-dependent metabolism did not affect AA-induced MKP-1 expression, indicating that eicosanoid biosynthesis was not involved in this process. The glutathione precursor N-acetylcysteine, an antioxidant, abolished AA-stimulated MKP-1 gene expression, whereas inhibition of protein kinase C by calphostin C had no influence on MKP-1 induction. VSMC pretreatment with genistein, a tyrosine kinase inhibitor, completely blocked AA-stimulated MKP-1 induction. MAPK kinase inhibitor PD 98059 did abolish AA-stimulated activation of extracellular signal-regulated kinases but not MKP-1 induction. Furthermore, agonists that increase AA release stimulated MKP-1 induction and activation of MAPKs, including extracellular signal-regulated kinases and c-Jun NH2-terminal protein kinases or stress-activated protein kinases. Taken together, our findings demonstrate that AA induced MKP-1 expression in VSMCs via activation of tyrosine kinases involving AA-induced free radical generation, suggesting an important role for MKP-1 in the regulation of AA-initiated signal transduction in VSMCs.
Sequential chromatography of human follicular fluid (hFF) on Sephadex G-50, Q-Sepharose and finally Cibracon Blue yielded a protein molecule which biologically had a stimulating effect on steroid secretion (SSF) by ovarian granulosa cells in vitro. SDS-gel electrophoresis followed by blotting on PVDF membrane of the biologically active fraction revealed 3 bands of ca. 28, 27 and 24 kDa. The N-terminal sequence of the 3 bands corresponded completely with that of apolipoprotein A-I. In view of this, it was of interest to examine whether human ovary expresses apo A-I. Using specific primers for apo A-I and apo A-I-like protein (ALP; Richardson et al., 1996), we could demonstrate the presence of mRNA for apo A-I as well as ALP in the granulosa cells. The expression of ALP was found to be much higher than that of apo A-I. Like hFF-protein, purified apo A-I could also stimulate steroid secretion by human granulosa cells incubated in the presence of cholesterol. The functional role of ovarian apo A-I/ALP may be speculated as a transport molecule for steroid precursors.
The incorporation of omega-3 and omega-6 fatty acids (FAs) into leukocyte membranes and the leukotriene (LT)B4-, LTB5 -, LTC4-, and LTCs-synthesizing capacity in stimulated leukocytes were measured following parenteral omega-3 FA nutrition in 20 postoperative patients. Total parenteral nutrition (TPN) over 5 days postoperatively was isonitrogenous (0.24 g N x kg-1 x d1) and isoenergetic (92 kJ/22 kcal x kg-1 x d-1), containing 0.15 g fish oil and 0.85 g soybean oil per kg-1 x d-1 (FO) or 1.0 g soybean oil x kg-1 x d-1 (SO). Following 5 days' FO administration, the content of eicosapentaenoic acid (EPA) was increased 2.5-fold, LTB5 1.5-fold, and LTC5 sevenfold. With SO nutrition, EPA and LTB5 generation remained unaltered, whereas LTC5 doubled. The production of LTB4 and LTC4 was not affected in any of the groups. We conclude that a 5-day parenteral fish oil supplementation has an immunomodulatory effect on lipid-mediator generation in human leukocytes in postoperative trauma.
The levels of endothelins 1 and 2 (ET-1 and ET-2) have been examined in 415 follicular fluids of 57 women participating in the IVF-ET programme in the University Women's Hospital, Marburg, in relation to the morphological appearance ("maturity") and fertilizability of harvested oocytes as well as to the levels of inhibin, FSH, IGF-1, estradiol and progesterone. Follicular aspiration was done transvaginally in all patients after down regulation with nafareline and ovarian stimulation using urofollitropin and menotropin. Ovulation was induced by hCG. ETs were measured by RIA using commercial kits supplied by Peninsula Laboratories, Belmont, CA. For FF samples, ET-1 and ET-2 RIAs were revalidated. Immunoreactive ET-1 was detectable in all follicular samples, the average level being 18.5 +/- 11.8 pg/ml, ET-2 was present only in 67.5% of the samples, the average level being 13.6 +/- 16.3 pg/ml. There was no significant difference in the average levels of ET-1 in the fluids of small, medium and large follicles. However, there was a significantly higher level of ET-2 in the fluids of medium compared to large follicles and there was a negative correlation of the ET-2 levels to the volume of the follicle (p < 0.01) which suggests that ET-2 could play a role during the maturation of the ovarian follicles. Unlike ET-1, the mean concentrations of ET-2 were significantly higher in the fluids with oocytes which could be fertilized and cleaved than in those with oocytes which did not fertilize or cleave, thus indicating a role for ET-2 in the process of oocyte maturation. No correlations of ET levels were found with the levels of inhibin, FSH, estradiol and progesterone. However, ET-2 levels significantly correlated with the levels of IGF-1 (p < 0.001) indicating a possible synergistic effect of endothelins and IGF-system. In conclusion, this study is further evidence for a physiological role of the ETs in the human ovary.
Within the framework of a cross-sectional study, we investigated 61 employees in an aluminium powder factory to see if aluminium had an influence on bone mineral content using the non-invasive method of bone density measurement. Thirty-two workers had been employed for, on average, 151 months in the area of aluminium powder production. Twenty-nine employees in the same factory, who had not been engaged in the production of aluminium powder, served as controls. The groups differed significantly in the concentrations of aluminium in urine and plasma. The bone mineral content, which was determined in the lumbar spine by means of photon absorptiometry showed no significant difference between the groups. The bone density value amounted to 1.00 g/cm2 for those exposed and 1.02 g/cm2 for the control group (median values). No correlation could be determined between the values obtained from the biological monitoring of the plasma or the duration of exposure and the bone density values. To summarise, using osteodensitometry as the method of investigation here, no influence could be detected for an occupational exposure to aluminium powders on the mineral salt content of the skeletal system in the area of the lumbar spine.
During the physiological adaptation of the Djungarian hamster, Phodopus sungorus, to a short photoperiod in autumn the modulation of specific serotonin (5-HT) binding sites of synaptic membranes was investigated in two brain regions, i.e. cerebral cortex and basal brain (CNS without cerebral cortex, cerebellum, pineal gland, and spinal cord). The radioligands [3H]5-HT and [3H]ketanserin were used to characterize total 5-HT1 and 5-HT2 binding sites, respectively. An increase of 5-HT1 and 5-HT2 binding sites was observed in both brain regions within 14 days after reduction of the photoperiod from a 14:10 h light/dark (l/d) cycle to an 8:16 h l/d cycle. The increase was still present after 56 days of the short photoperiod. Binding kinetics assayed after 4 days of the short photoperiod show that maximal specific binding of [3H]5-HT and [3H]ketanserin was increased, while dissociation constants (KD) were not changed. The membrane anisotropy of synaptic membranes, measured by fluorescence polarization, was reduced transiently during the early part of the adaptation. Neither the phospholipids nor the mole ratio of cholesterol to phospholipids were significantly affected by adaptation to short photoperiod. The results suggest an important role of the central nervous 5-HT system in the physiological adaptation of the Djungarian hamster to a short photoperiod.
A luteinising hormone receptor binding inhibitor (LHRBI) has been purified from bovine corpus luteum (CL). Steroid-free extract of the CL was subjected to successive chromatographies on Sephadex G-50, Q-Sepharose, Orange A dye and metal chelate affinity columns followed by high performance-reverse phase and gel filtration columns. Purification was monitored by the ability of the fractions to inhibit the binding of 125I-human chorionic gonadotropin (hCG) to porcine granulosa cells in vitro. The final isolate showed an 8000-fold enrichment of activity. It was also capable of inhibiting porcine granulosa cell secretion of estradiol and progesterone (P) in vitro. Administration of LHRBI into follicle-stimulating hormone (FSH)-stimulated, immature rats strongly inhibited the ovarian ovulatory response to hCG as revealed by decreased P levels and the number of ova released. The M(r) of LHRBI as assessed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis was ca. 15 kDa and the pI was between 5.0 and 5.5.
Investigations on muscle fat content and intramuscular adipose tissue pattern of 51 male castrated pigs were performed. For each body 4 muscles were collected after slaughter. Breeding lines of swine (German Landrace) had been selected through 8 generations for high ("E(+)-Line") and low ("E(-)-Line") levels of NADPH-generating dehydrogenases including a control group without selection. 42 animals were kept under feeding experiments of various energy levels from 60 kg up to 100 kg body mass. Additionally, out of control line 5 piglets (25 kg) and 4 hogs (135 kg) were examined. Data of ether-extracted total fat content versus data of fat marbling planimetry correlated well with r = 0.9. The average degrees of muscle fattening were: m. semispinalis capitis (11%) much much greater than m. psoas major (1.8%) greater than m. semimembranosus (1.7%) greater than m. long thoracis (1.3%). The specific internal relation of muscle fattening with respect to the collected samples was calculated as r = 0.8. Intramuscular fat showed the tendency to increase with higher levels of dietary energy. The E(+)-Line showed higher (16%) muscle fattening than the E(-)-Line. The control group, however, showed 44% higher levels than the E(+)-Line. So, the results of that K degree-Line could not serve as baseline for interpretations. The criteria of thickness and harmony of marbling scores were used to make statements of meat quality: The samples of m. psoas major and E(+)-Line reached the best, the samples of m. semispinalis capitis and the K degree-Line reached the least values.(ABSTRACT TRUNCATED AT 250 WORDS)
Medroxyprogesterone acetate (MPA) treatment has been shown to exert several beneficial effects in cancer patients. It has been suggested that such effects are due in part to the metabolites derived from MPA in vivo. The first results are reported on the identification of 2 alpha-hydroxy- and 21-hydroxy-MPA, 20-dihydro-MPA, 17 alpha-acetoxy-2 alpha,3 beta-dihydroxy-6 alpha-methylpregn-1,4-dien-20-one and two X,21-dihydroxy-MPAs, one of them presumably being 6 alpha-hydroxymethyl-21-hydroxy-MPA, in patient's plasma by high-performance liquid chromatographic (HPLC), gas chromatographic-mass spectrometric and NMR methods. Additionally, the presence of other metabolites such as di- and tetrahydro-MPAs and 6,21-dihydroxy-MPA, found in urine and other samples, was demonstrated in plasma. For routine clinical examinations an HPLC method is described for determination of, e.g., the unreduced MPA metabolite group in Sep-Pak-ODS column extracts of patients' plasma.
Measurements of morphological and biochemical parameters in subcutaneous adipose tissue as well as investigations of energy metabolism and fat deposition of 89 male castrated pigs were performed. Breeding lines of swine (German Landrace) had been selected through 8 generations for high ("E(+)-Line") and low ("E(-)-Line") levels of NADPH-generating dehydrogenases. A control group ("K.") without selection was closely paralleled. For 21 days the animals were kept under feeding experiments within 2 sectors of growing period (67 kg, 85 kg body mass), and biopsies of backfat were examined subsequently. The inner layer of subcutaneous adipose tissue showed constantly bigger fat cells than the outer layer. The fat cell size increased generally with fattening and body mass respectively. The cellularity of adipose tissue was dependent significantly on the percentage of the very small fat cells measured up to 30 microns diameter (= "PKF30"). The breeding lines differed slightly with respect to their cellularity: The inner layer showed the gradation E+ greater than K. greater than E- concerning fat cell volumes and fat cell surfaces respectively. The PKF30 correlated significantly with food energy level as well as with the respirationally examined protein retention, particularly in inner layers of younger animals. Relations to the fat deposition (examined respirationally or with the D2O-Method and after slaughter respectively) were recognized, not showing validity for all cases. The parameters of lipogenic activity tested by tissue slice preparations and homogenates respectively correlated negatively with average fat cell size.(ABSTRACT TRUNCATED AT 250 WORDS)
The cellularity of subcutaneous adipose tissue of 108 male castrated pigs (German Landrace) was investigated. The tissue was taken bioptically under anesthetic conditions. The outer and the inner layer of backfat were examined separately, fresh unfixed tissue slices floating in Ringer solution were subjected to microscopic measurements of adipocyte diameters. The animals were kept in feeding experiments, 3 and 2 sectors respectively of growing period were examined (40 kg; 66 kg, 88 kg body mass) divided into 6 and 4 feeding levels respectively for 21 days (0.4; 0.6/0.8; 1.0; 1.2; 1.4 MJ metabolic energy per kg body mass0.75 per day). The inner layer of backfat showed bigger fat cells compared to the outer layer. The average fat cell size was greater for the older and heavier than for the younger animals. The gradation of food administration resulted not in a straight parallel rise in fat cell size but in an effective consequence with respect to the distribution frequency of the dates: The higher the food energy level, the more the accumulation of small fat cells from 10 til 30 microns diameter. These cell fractions succeeded in being signified as typical and important closed population. Other authors also had described these particular cells, i.e. "fat cell clusters" and "VSFC" (= very small fat cells) respectively. An external use of the dates for computer simulation programs resulted in success and manifested the independently gained conclusions. The examinations were performed by support of different branches of literature and the results had to be discussed in front of a wide background of known connections.(ABSTRACT TRUNCATED AT 250 WORDS)
The study reports the C-reactive protein (CRP) plasma concentrations in 115 women with a presumed diagnosis of acute adnexitis. In addition to CRP, blood sedimentation rate, white blood cell count and the body temperature were evaluated and compared with the clinical findings. Diagnosis was confirmed or excluded by laparoscopy (n = 69) or laparotomy (n = 9). Clinical examinations and conventional laboratory examinations were of limited value in the diagnosis of acute adnexitis. In contrast, CRP was a highly sensitive indicator of inflammatory pelvic disease. Furthermore, the CRP determination was superior in assessing the efficacy of an antibiotic treatment.