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Biomedical subjects

L Nilsson

Publications and source records attributed to L Nilsson.

At least 343 records · Page 19Linked to original sources
PubMed1986

Inhibitory effects of danazol on steroidogenesis in cultured human granulosa cells.

The effect of danazol on steroidogenesis in cultured human granulosa cells was studied. Granulosa cells obtained from antral follicles in the mid to late follicular phase were cultured for 2 to 6 days. Danazol (0.1 to 5 micrograms/ml) and human chorionic gonadotropin (hCG, 10 IU/ml), alone or in combination, were added to the culture medium. Testosterone (T) (1 microgram/ml) was added as an aromatase substrate in certain experiments. The medium content of progesterone (P) and estradiol (E2) was determined. Basal P secretion was variably influenced by danazol, whereas a consistent dose-dependent and reversible inhibition of the hCG-stimulated P secretion was found. In the presence of T, danazol caused a dose-dependent inhibition of both basal and hCG-stimulated E2 secretion, and this effect became more pronounced with time. The results demonstrate that danazol exerts direct inhibitory effects on steroidogenesis in cultured human granulosa cells.

Adult↗
PubMed1985

Localization of the sites of ADP-ribosylation and GTP binding in the eukaryotic elongation factor EF-2.

Tryptic cleavage of EF-2, molecular mass 93 kDa, produced an 82-kDa polypeptide and a 10-kDa fragment, which was further degraded. By a slower reaction the 82-kDa polypeptide was gradually split into a 48-kDa and a 34-kDa fragment. Similarly, treatment with chymotrypsin resulted in the formation of an 82-kDa polypeptide and a small fragment. In contrast to the tryptic 82-kDa polypeptide the corresponding chymotryptic cleavage product was relatively resistant to further attack. The degradation of the 82-kDa polypeptide with either trypsin or chymotrypsin was facilitated by the presence of guanosine nucleotides, indicating a conformational shift in native EF-2 upon nucleotide binding. No effect was observed in the presence of ATP, indicating that the effect was specific for guanosine nucleotides. After affinity labelling of native EF-2 with oxidized [3H]GTP and subsequent trypsin treatment the radioactivity was recovered in the 48-kDa polypeptide showing that the GTP-binding site was located within this part of the factor. Correspondingly, tryptic degradation of EF-2 labelled with [14C]NAD+ in the presence of diphtheria toxin showed that the site of ADP-ribosylation was within the 34-kDa polypeptide. By cleavage with the tryptophan-specific reagent N-chlorosuccinimide the site of ADP-ribosylation could be located at a distance of 40-60 kDa from the GTP-binding site and about 4-11 kDa from the nearest terminus.

Adenosine Diphosphate Ribose↗
PubMed1985

Reduced ribosomal binding of eukaryotic elongation factor 2 following ADP-ribosylation. Difference in binding selectivity between polyribosomes and reconstituted monoribosomes.

The biological activity of elongation factor 2 (EF-2) following NAD+ - and diphtheria-toxin-dependent ADP-ribosylation was studied (i) in translation experiments using the reticulocyte lysate system and (ii) in ribosomal binding experiments using either reconstituted empty rat liver ribosomes or programmed reticulocyte polysomes. Treatment of the lysates with toxin and NAD+ at a NAD+/ribosome ratio of 4 resulted in a 90% inhibition of the amino acid incorporation rate. The inhibition was overcome by the addition of native EF-2. At this level of inhibition more than 90% of the EF-2 present in the lysates was ADP-ribosylated and the total ribosome association of EF-2 was reduced by approx. 50%. All of the remaining unmodified factor molecules were associated with the ribosomes, whereas only about 3% of the ribosylated factor was ribosome-associated. The nucleotide requirement for the binding of EF-2 to empty reconstituted rat liver ribosomes and programmed reticulocyte polysomes was studied together with the stability of the resulting EF-2 X ribosome complexes using purified 125I-labelled rat liver EF-2. With both types of ribosomes, the complex formation was strictly nucleotide-dependent. Stable, high-affinity complexes were formed in the presence of the non-hydrolysable GTP analogue guanosine 5'-(beta, gamma-methylene)triphosphate (GuoPP[CH2]P). In contrast to the reconstituted ribosomes, GTP stimulated the formation of high-affinity complexes in the presence of polysomes, albeit at a lower efficiency than GuoPP[CH2]P. The formation of high-affinity complexes was restricted to polysomes in the pretranslocation phase of the elongation cycle. Low-affinity post-translocation complexes, demonstrable after fixation, were formed in the presence of GTP, GuoPP[CH2]P and GDP. In polysomes, these complexes involved a different population of particles than did the high-affinity complexes. In the binding experiments using reconstituted or programmed ribosomes, the pretranslocation binding of EF-2 observed in the presence of GuoPP[CH2]P was reduced by approx. 50% after ADP-ribosylation, whereas the post-translocation binding in the presence of GDP was unaltered. The data indicate that the inhibition of translocation caused by diphtheria toxin and NAD+ is mediated through a reduced affinity of the ADP-ribosylated EF-2 for binding to ribosomes in the pretranslocation state.

Adenosine Diphosphate Ribose↗
PubMed1985

The effect of nicotine and cytisine on 3H-acetylcholine release from cortical slices of guinea-pig brain.

Nicotine 1.8 X 10(-5)-1.8 X 10(-4) mol/l enhanced the spontaneous 3H-efflux from guinea-pig cortical slices preloaded with 3H-choline and perfused in the presence of hemicholinium (HC-3). The facilitation of tritium outflow was prevented by tetrodotoxin 5 X 10(-7) mol/l and by D-tubocurarine 4.5 X 10(-6) mol/l. Nicotine 1.8 X 10(-6)-1.8 X 10(-4) mol/l, and the agonist cytisine 5 X 10(-7)-5 X 10(-5) mol/l increased, in a concentration-dependent way, 3H-efflux from electrically-stimulated slices (0.2 Hz). The concentration-response curves of both drugs were parallelly shifted to the right by D-tubocurarine 4.5 X 10(-6) mol/l. The EC50 values (i.e. the concentrations required to cause a 50% increase in the S2/S1 ratio) changed for nicotine from 5.58 X 10(-5) to 4.34 X 10(-4) and for cytisine from 6.3 X 10(-6) to 2.75 X 10(-4) mol/l in the absence and in the presence of the antagonist, respectively. In the range of 0.2-2 Hz the magnitude of the effect of nicotine was inversely related to the rate of stimulation. The response to nicotine was subject to rapidly developing tachyphylaxis; it was resistant to atropine. It is concluded that nicotine and cytisine facilitate 3H-efflux from the cholinergic nerve endings of guinea-pig cerebral cortex. This effect involves sodium-dependent mechanisms and is due to an interaction of the drugs with receptors showing affinity for D-tubocurarine.

Acetylcholine↗
PubMed1985

Simplification of the method of in vitro fertilization: sonographic measurements of follicular diameter as the sole index of follicular maturity.

As a simplification of the in vitro fertilization (IVF) procedure, repeated sonographic scanning of follicular diameters in stimulated cycles was performed, until the largest visible follicle reached a mean diameter of at least 20 mm, at which time human chorionic gonadotropin (hCG) was administered. Follicle puncture was performed either guided by sonography or by laparoscopy 34-36 hr after the hCG injection, and following insemination oocytes were cultured for 48-60 hr before embryo transfer (ET). Serum levels of luteinizing hormone (LH), prolactin (PRL), and estradiol-17 beta (E2) at the time of hCG injection as well as follicular fluid levels of follicle stimulating hormone (FSH), LH, and PRL as well as progesterone (P), testosterone (T), and E2 at the time of puncture were determined in retrospect using specific radioimmunoassay (RIA). It was found that the knowledge of a single value of LH or E2 in serum should have been of little additional value for the decision to give hCG in all stimulation models used: clomiphene + hCG, human menopausal gonadotropin (hMG) + hCG, and clomiphene + hMG + hCG. The concentrations of the three steroids measured in follicular fluid were, in a high proportion of the follicles, within a normal range in all stimulation models. The group receiving clomiphene + hMG + hCG appeared promising through its higher proportion of estrogenic follicles. It is concluded that sonographic measurement of follicular diameters may be used as the sole index of follicular maturity in an IVF program.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Exposure distribution, absorbed doses, and energy imparted for panoramic radiography using Orthopantomograph model OP 5.

The absorbed doses and energy imparted for the Orthopantomograph model OP 5 using two different collimators (0.9-1.3 X 33 mm2 and 0.6-0.9 X 39.5 mm2, respectively) were examined at 70 and 75 kV. The absorbed doses were estimated by thermoluminescence dosimetry in a sectioned phantom and by the energy imparted from measurements of areal exposure using a plane parallel transmission ionization chamber. The exposure distribution was surveyed on radiographic film. The anterior part of the parotid glands received the highest absorbed doses (2.4-3.2 mGy) when the wider collimator was used, with a decrease of two to three times when the narrower collimator was used. Other areas received absorbed doses of about 1.0 to 1.5 mGy or below. An increase of the kV from 70 to 75 had a minor influence. The energy imparted for the wider collimator was 0.6-0.8 and for the narrower collimator, 0.4-0.6 mJ.

Eye↗
PubMed1985

Oocyte maturation as regulated by follicular factors.

Follicular fluid (FFl), obtained from 24 women treated with clomiphene/hCG in an in vitro fertilization program, was characterized with respect to steroid hormone levels and oocyte maturation inhibitor (OMI) activity. Three FFl samples apparently were derived from cystic follicles and contained low steroid levels and no OMI activity in an in vitro rat oocyte assay. The remaining 21 follicles contained normal preovulatory steroid levels and mature and generally fertilizable oocytes. In 7 of these follicles the FFl (at 50% concentration) significantly inhibited rat oocyte meiosis, while 14 exerted no OMI activity. The results confirm earlier work on porcine and human FFl, suggesting that the putative OMI activity declines with follicular maturation.

Animals↗
PubMed1985

Development of arteriovenous shunts in rejecting rat kidneys.

Arteriovenous shunts in rejecting rat kidneys were studied in vivo by injecting radiolabelled 15-micron microspheres into the graft artery 4-7 days after transplantation. Serum creatinine levels were measured and the transplants were examined microscopically. The radioactivity in the transplanted kidneys, lungs and the hind legs was recorded. A progressive increase in the amount of radioactivity found in the lungs started 5 days after allogenic transplantation but not after isotransplantation. Increased serum creatinine levels were first recorded on day 6 and focal necrosis or hemorrhages were not seen microscopically at any time. The results support the hypothesis that arteriovenous anastomoses are opened or created early as a part of the graft rejection process and not as a late consequence of tissue necrosis.

Animals↗
PubMed1985

Effect of gonadotrophins on progesterone secretion by cultured granulosa cells obtained from human preovulatory follicles.

Granulosa cells were obtained from human preovulatory follicles in 31 women undergoing in vitro fertilization and embryo transfer due to tubal infertility. Follicular maturation was stimulated and synchronized by treatment with Clomiphene or human menopausal gonadotrophin (hMG), or both, plus human chorionic gonadotrophin (hCG). Follicles were aspirated by ultrasound guided puncture approximately 34-36 h after the hCG injection. The granulosa cells were washed and suspended in modified medium 199 containing 10% foetal bovine serum and cultured as monolayers for 6-8 days in the absence and presence of hormones and reactants. Progesterone formation was analyzed by RIA. In general, the cells underwent morphological luteinization and secreted high amount of progesterone. Under basal conditions the secretion of progesterone was highest during the first 2 days in culture and then gradually declined. Progesterone secretion was stimulated by human LH, hCG and the adenylate cyclase stimulator forskolin, with a maximal effect between days 2-6. The beta-adrenergic agonist isoproterenol in preliminary experiments potentiated the stimulatory effect of hCG but had no own stimulatory effect. No clear differences in progesterone secretion or responsiveness to in vitro stimulation relating to the various in vivo stimulation protocols were found.

Cell Count↗
PubMed1985

The hormonal situation in the perimenopausal period.

Follicular function starts in the foetal ovary in the 20th week of gestation and continues until or shortly past the menopause. Luteal steroid production occurs only during the fertile period. After the menopause only stromal steroid production continues in the ovary and is probably increased by the increase in gonadotropin levels. The changes in hormonal levels and effects in the pre-, peri- and postmenopausal years are described as a function of these changes.

Adolescent↗
PubMed1984

Quantification of the different ribosomal phases during the translational elongation cycle in rabbit reticulocyte lysates.

The proportionality of different ribosomal phases during elongation was estimated in the highly effective rabbit reticulocyte lysate system by use of several complementary analytical methods. The stoichiometric amounts of ribosome-bound elongation factors EF-1 and EF-2 were determined as a measure of ribosomal A-site occupation. The results were correlated with the puromycin reactivity of the P-site-located nascent polypeptide chains. Approximately 25% of the ribosomes were associated with EF-2, indicating that their A-sites contained peptidyl-tRNA. About 35% were associated with EF-1, signifying that their A-sites were occupied by aminoacyl-tRNA. The puromycin reactivity of the nascent chains was approximately 40%. From these data it is concluded that 75% of the peptidyl-tRNAs were located in the P-sites and that their puromycin reactivity was limited by the availability of ribosomal A-sites free for puromycin interaction. After guanosine 5'-[beta, gamma-methylene]triphosphate blockage of the translation, the ribosomal content of elongation factors drastically changed. Under these conditions the proportion of EF-1-containing ribosomes increased to approximately 50% while EF-2-containing ribosomes decreased to 5%. Concomitantly, the puromycin reactivity increased to approximately 45%. In contrast to previous assumptions the experiments support the view that the elongation rate is limited by the availability of ribosomal A-sites for the selection of mRNA-cognate aminoacyl-tRNAs.

Animals↗
PubMed1984

Self-monitoring of blood glucose by diabetic women during the third trimester of pregnancy.

The clinical value of self-monitoring blood glucose in diabetic pregnancy at home was compared with hospital care in the thirty-second to thirty-sixth week of pregnancy in a prospective randomized study including 100 pregnancies in 97 patients (White's class B, 38; C, 25; D, 28; and F, 9) of which 54 were in the home group and 46 in the hospital group. The duration of pregnancy was not significantly different in two treatment groups, with a median duration of 266.0 days in the home group and 266.5 days in the hospital group. The mean blood glucose values during the study period were 5.9 mmol/L in the home group and 6.0 mmol/L in the hospital group, thus there were no significant group differences. There were no significant group differences in pregnancy complications; however, 10 of 54 (19%) had to interrupt home-monitoring because of pregnancy complications. The perinatal morbidity was not significantly different in the two treatment groups, with the following percentages of complications in the combined series: 4% idiopathic respiratory distress syndrome, 7% transient tachypnea, 2% symptomatic hypoglycemia, 16% hyperbilirubinemia, 22% feeding problems, and 10% erythrocytosis.

Blood Glucose↗
PubMed1984

The decarboxylation of 3-mercaptopyruvate to 2-mercaptoacetate.

Rat brain mitochondria were found to convert 3-mercaptopyruvate to 2-mercaptoacetate in the presence of NAD+, coenzyme A and thiamin pyrophosphate. The overall reaction probably consists of an oxidative decarboxylation of 3-mercaptopyruvate with 2-mercaptoacetyl CoA as a product which is then hydrolyzed to 2-mercaptoacetate by acyl CoA hydrolase.

Animals↗
PubMed1984

Affinity labelling of the eukaryotic elongation factor EF-2 with the guanosine nucleotide analogue 5'-p-fluorosulfonylbenzoylguanosine.

During the translocation of the nascent peptide chain from the ribosomal aminoacyl-site to the peptidyl-site, GTP is hydrolyzed by a mechanism dependent on both ribosomes and the elongation factor EF-2. For insight into the mechanism of GTP hydrolysis, we studied the ability of the GTP analogue 5'-p- fluorosulfonylbenzoylguanosine ( FSO2BzGuo ) to act as an affinity label of the guanine-specific site. Pre-incubation of EF-2 with FSO2BzGuo at increasing concentrations progressively inactivated the EF-2 and ribosome-dependent GTPase activity. Up to 0.5 mM FSO2BzGuo , the inactivation of the GTPase activity was stoichiometrically correlated with the covalent binding of [3H] FSO2BzGuo . Thus, one molecule of covalently bound FSO2BzGuo completely inactivated the GTPase activity of EF-2. Ribosomes or 60-S ribosomal subunits pre-incubated with FSO2BzGuo were not inactivated, consistent with the idea that the GTP hydrolysis involved in the ribosomal translocation takes place on EF-2.

Affinity Labels↗
PubMed1984

Nucleotide-mediated interactions of eukaryotic elongation factor EF-2 with ribosomes.

Eukaryotic elongation factor EF-2 isolated from rat liver microsomal salt-wash showed two types of nucleotide-dependent interactions with reconstituted empty 80S ribosomes when analyzed by gradient centrifugation. Stable EF-2 X ribosome complexes were only formed with GTP analogues with reduced or no ability to serve as substrates for the EF-2 and ribosome-dependent GTPase. GTP-stimulated complex formation was only demonstrable after glutaraldehyde fixation, unless a GTP-regenerating system was included throughout the gradient centrifugation. GDP and to a lesser extent GMP and guanosine also stimulated the less stable type of complex formation as demonstrable after fixation. Under the same conditions some complex formation was also observed with ATP and its analogue adenosine 5'-[beta,gamma-methylene]triphosphate, although with less efficiency than with the corresponding guanosine nucleotides. The results in combination with available data indicate that EF-2 has two binding states with different affinities on the 80S ribosome: a high-affinity pre-translocation state specific for EF-2 X GTP and a low-affinity post-translocation state, in which EF-2 X GDP is bound to the ribosome in a less stable and specific complex.

Animals↗
PubMed1984

Granulosa and thecal cells from human ovarian follicles under growth: steroid formation in vitro and responsiveness to human chorionic gonadotropin.

In order to characterize the patterns of steroid production and gonadotropin responsiveness in growing human follicles, follicular thecal and granulosa cells were incubated for two hours in the presence or absence of human chorionic gonadotropin (hCG). After incubation, tissue cyclic AMP (cAMP) levels and medium content of progesterone (P), androstenedione (A) and estradiol-17 beta (E) were determined. A was the dominant steroid formed by the thecal cells, regardless if these were derived from small (diameter: 4-7.5 mm) or from large (diameter: 8-15 mm) follicles. Granulosa cells from small follicles formed minimal amounts of all steroids measured, while granulosa cells from large follicles produced considerable amounts of E in vitro. Thecal cells from both small and large follicles increased their production of cAMP in the presence of hCG. Steroid formation was significantly increased by hCG in thecal cells from large follicles only. Granulosa cells from large follicles responded to hCG in vitro with increased cAMP and steroid formation, while granulosa cells from small follicles appeared insensitive to hCG in vitro.

Adult↗