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Biomedical subjects

L Nilsson

Publications and source records attributed to L Nilsson.

At least 379 records · Page 21Linked to original sources
PubMed1982

Collagen synthesis inhibition by PGE2 within the human follicular wall--one possible mechanism underlying ovulation.

Follicular wall specimens were taken from various parts of human preovulatory follicles as well as from less developed follicles. The tunica albuginea was isolated and incubated for 2 h in Krebs Ringer bicarbonate buffer containing 3H-proline in the presence or absence of PGE2 (0.1 microgram/ml). Following incubation the incorporated radioactivity was determined and related to the protein content of each strip. PGE2 had a specific effect on the incorporation of 3H-proline into protein in the follicular wall. In the apical part of the preovulatory follicle a significantly decreased incorporation was registered, indicating a reduced net synthesis of collagen. However, PGE2 was without effect on specimens derived from the non-apical parts of the preovulatory follicles as well as from the less developed follicles. It is suggested that the registered biochemical changes induced by PGE2 are of importance for the process of human ovulation.

Adult↗
PubMed1982

Mutagens in larger fungi. I. Forty-eight species screened for mutagenic activity in the Salmonella/microsome assay.

Specimens of large fungi (mushrooms) were screened for mutagenic activity by the Salmonella/microsome assay, with strains TA98, TA2637 and TA100. Our of 48 species tested, 37 exhibited a significant but for the most part weak activity. The activity observed in the presence of S9 mix was typically between 0 and 50% of that without, and in no case was the activity increased in the presence of microsomal enzymes. Six metabolites reported to occur in some of the species included in this investigation were also tested. Significant mutagenic activity was found with isovelleral (5) from Lactarius sp., agaritine (3) from Agaricus bisporus and related sp. and beta-nitraminoalanine (7) from Agaricus silvaticus. Isovelleral may be a major mutagen in some of the sharp-tasting and mutagenic Russulaceae sp. A. bisporus (cultivated specimen) was weakly mutagenic toward all three strains of S. typhimurium, used, and agaritine was weakly active toward TA2637 alone. This implies that this fungus might contain other mutagenic material as well. beta-Nitraminoalanine was not found in the particular collection of A. silvaticus tested here. The mutagenicity observed for the fungus in this work may therefore be due to other metabolites. Even though many species found to be mutagenic are used as food, it seems premature to make specific recommendations about eventual health risks. Further information is needed about the chemistry and toxicology of the active compounds as well as about the effects of various methods used in preparing mushrooms for food.

Animals↗
PubMed1982

Recruitment of an ovulatory follicle in the human following follicle-ectomy and luteectomy.

The study was undertaken to explore the time required for the selection and ovulation of a dominant follicle after interference with the normal menstrual cycle of fertile women. At routine laparotomy (sterilization) a leading follicle or a fresh corpus luteum was excised, and the day of the next ovulation was estimated by monitoring of serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), progesterone, and 17 beta-estradiol and by registration of the growth of the follicles through ultrasonic scanning. The results are in accordance with earlier observations in the rhesus monkey demonstrating that the recruitment and selection of an ovulation-competent follicle takes 12 to 14 days in the primate. Since this time is close to the length of the normal follicular phase and approximately the same after follicle-ectomy and luteectomy, the results suggest an importance of local factors in regulating follicle recruitment.

Adult↗
PubMed1982

Structural variability of tRNA: small-angle x-ray scattering of the yeast tRNAphe-Escherichia coli tRNAGlu2 complex.

The structure of the complex formed in solution between yeast tRNAPhe and Escherichia coli tRNAGlu2 has been studied by small-angle x-ray scattering. The complex has a radius of gyration of 4.0 nm and an electron-pair distance distribution that is incompatible with a model composed to two tRNAs joined at their complementary anticodons and exhibiting the L shape seen in the crystal. Instead a model in which the two tRNAs, still bound via the anticodons, assume a conformation with the acceptor arms folded toward the anticodon arms agrees with the observed scattering curves.

Anticodon↗
PubMed1982

Differential diagnosis of presenile dementia on clinical grounds.

Fifty-seven patients were studied for differential diagnosis between dementias. Three rating-scales were used for identification of Alzheimer's disease (AD), Pick's disease (PD) and multi-infarct dementia (MID). Their validity was tested against verified diagnoses in 28 patients. The rating-scale of ischemic score consisting of 13 items such as abrupt onset, stepwise progression, fluctuating course, history of strokes and neurological symptoms and signs, identifies patients with MID. This can also be achieved by the two rating-scales for diagnosis of AD (12 items) and PD (9 items), which, however, can also be used for the differentiation between these two dementias. The rating-scale for diagnosis of AD contains clinical features such as early spatial disorientation, apraxia, aphasia, agnosia, logoclonia and increased muscular tension. The rating-scale for PD contains i.a. early loss of insight, early signs of disinhibition, echolalia, mutism and amimia. The results show that the differentiation between the major types of presenile dementia can be achieved by a systematic rating of the clinical features.

Adult↗
PubMed1982

Steroid and adenosine 3',5'-monophosphate formation in granulosa and thecal cells from human preovulatory follicles in response to human chorionic gonadotropin.

Granulosa and thecal cells from the preovulatory follicles of 14 women were mechanically isolated and separately incubated for short term periods (0.5-4 h) in the presence and absence of hCG. After incubation, tissue cAMP levels and medium progesterone content of (P), androstenedione (A), and 17 beta-estradiol (E2) were determined. All follicles appeared healthy and mature, as judged by their number of granulosa cells, histological examination of the oocytes, athe steroid levels in antral fluid, as well as the appearance of the oocyte-cumulus complexes. Under basal conditions, both granulosa and thecal cells had the capacity to synthesize all of the steroids measured. The predominant steroid formed by the granulosa cells was P, while the thecal cells formed A as the major steroid. Both cell types produced considerable amounts of E2. The addition of hCG in various concentrations gave rise to concentration-dependent increase in cAMP formation in both cell types. Furthermore, hCG caused a statistically significant increase in the formation of P and A by the thecal cells, while steroid formation by the granulosa cells was not significantly altered. With higher concentrations of hCG, however, there was a tendency toward a stimulation of P synthesis in the granulosa cells from most of the follicles tested. It is concluded that in preovulatory follicles of human origin, follicular steroidogenesis is not rigidly compartmentalized between the two cell types. Furthermore, both granulosa and thecal cells are sensitive to stimulation with hCG in this type of follicle.

Adult↗
PubMed1981

Conformational states of yeast tRNA Phe in the complex with cognate and non cognate synthetases.

The influence of phenylalanyl-tRNA synthetase and seryl-tRNA synthetase on the conformation and structural kinetics of yeast tRNA Phe was investigated. Ethidium substituted for dihydrouracil at position 16 or 17 was used as a structural probe, showing the existence of three conformational states in tRNA. The distribution of states (T1, T2, T3) is changed only by the cognate synthetase towards T3 which probably is related to the X-ray structure. The binding of phenylalanyl-tRNA synthetase leads to an about 10-fold increase in the fast transition T1 in equilibrium or formed from T2 which has been assigned to changes in the anticodon loop conformation and to a 2-3 fold increase in the slow transition which probably extends to other parts of the tRNA molecule. The observed rates for the transition T2 in equilibrium or formed from T3 are close to that observed for the transfer of the activated phenylalanine to tRNA Phe. This raises the possibility that the conformational transition in tRNA is the rate limiting step in the charging reaction.

Amino Acyl-tRNA Synthetases↗
PubMed1981

Acute effects of gonadotrophins and cyclic AMP on protein synthesis and progesterone production by isolated rat granulosa cells.

Amino acid uptake, protein synthesis and progesterone production were studied in rat granulosa cells, isolated from follicles of different stages of development. The amino acid uptake in granulosa cells from prepubertal rats was rapid with a distribution ratio above 1 within 10 min. No significant effects of gonadotrophins were observed on this parameter. The acute influence of exogenous LH and FSH or dibutyryl cyclic AMP (dbcAMP) on incorporation of 3H-leucine or 3H-phenylalanine was investigated as a measure of the rate of protein synthesis. In most experiments progesterone production was determined concomitantly. Both FSH (10 micrograms/ml or 100 micrograms/100 g b.wt.) and dbcAMP (a mM) stimulated (1.6--1.8 fold) the incorporation of leucine into granulosa cell proteins from prepubertal rats while LH was without effect. Progesterone production in these granulosa cells was very low and neither the gonadotrophins nor dbcAMP were stimulatory. Similarly designed experiments were performed on granulosa cells isolated from preovulatory rat follicles. It was then found that both FSH (10 micrograms/ml or 100 micrograms/199 g bst.) and dbcAMP (1 and 5 mM) as well as LH (10 micrograms/ml or 100 micrograms/100 g b.wt.) significantly (1.2--2 fold) stimulated protein synthesis. Furthermore, basal progesterone production was higher and was markedly stimulated (3--6 fold) by all three substances tested. The observations that the protein synthesis in immature granulosa cells is increased by exposure to FSH and dbcAMP while progesterone production in not, whereas both these parameters are stimulated with FSH, LH and dbcAMP in the preovulatory granulosa cells suggest that there might be certain differences in the nature of the proteins synthesized by immature and preovulatory granulosa cells.

Amino Acids↗