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Biomedical subjects

V Hansson

Publications and source records attributed to V Hansson.

At least 145 records · Page 8Linked to original sources
PubMed1984

Catecholamine responsive adenylate cyclase in human myocardial preparations. Properties and optimalization of assay conditions.

In the present study we have investigated the conditions for optimal adenylate cyclase (AC) activity in preparations of human myocardial biopsies, with emphasis on both basal enzyme activity and isoproterenol response. Different preparation procedures (homogenates, membrane particles) of the same biopsy showed no difference in relative response to isoproterenol, although absolute activities, using protein concentration for normalization, showed some variance. The AC-receptor complexes of the preparations were also stable when stored on ice for 3 h, and both basal and stimulated AC activities were constant at a wide range of protein concentrations (2.9-31.9 micrograms/tube), and throughout 92 min incubation. The effects of varying Mg2+, guanyl nucleotides (GTP, GMP-P(NH)P), and ATP concentrations on myocardial AC activities were also investigated under both basal conditions as well as after isoproterenol stimulation. The apparent Km for the substrate (Mg X ATP) binding to the AC was approximately 0.1 mmol/l. Isoproterenol stimulated the AC activity by increasing Vmax (41 to 142 pmol/mg protein X min) without any change in the apparent Km. Maximal relative activation by isoproterenol was achieved at pH 6.5-7.0. The concentration of isoproterenol causing half maximal AC stimulation was approximately 0.1 micrograms/ml (2 X 10(-4) mmol/l). Half maximal inhibition of isoproterenol (4 micrograms/ml) stimulated AC activity was obtained by 0.025 micrograms/ml propranolol (8 X 10(-5) mmol/l). The sensitivity and precision of this assay should make it possible to measure AC activity as well as isoproterenol response in very small quantities of myocardial tissue. This could provide a method for studying receptor functions of sick hearts by endomyocardial biopsies.

Adenosine Triphosphate↗
PubMed1984

Testicular gonadotropin receptors, testicular testosterone, dihydrotestosterone and androstenedione in the developing bull.

The testis homogenate from Red bull (3-17 months of age) show specific binding of hLH and hFSH with Kd of 1.3 +/- 0.1 X 10(-10)M and 1.5 +/- 0.1 X 10(-9)M, respectively. Prepubertal bulls (3-5 3/4 months) exhibit the highest binding capacity of both LH and FSH, revealing the fact that LH and FSH receptors are present in high concentrations prior to the first rise in plasma T. The testicular T concentration was significantly higher in the four prepubertal bulls than in the four older animals in spite of the fact that circulating T is lower before puberty. Thus, local androgen effects within the testis may occur before peripheral androgenization. The prepubertal bull Leydig cell also displayed steroidogenic capacity. The ratio of biologically active (testosterone, dihydrotestosterone) to inactive androgens (androstenedione) increased as the animals approached puberty. Such qualitative changes in steroid production may be one of the factors responsible for peripheral androgenization.

Androgens↗
PubMed1984

Germ cell adenylyl cyclase activity in the human undescended testis and the effect of HCG-treatment.

In the present study we have examined the soluble Mn2+ dependent, germ cell specific adenylyl cyclase (AC) activity and germ cell morphology in testicular biopsies from twenty-three boys, aged 2-17 years, with undescended testes and three adult men with normally descended testes. Eight of the boys were treated with hCG immediately before surgery. Germ cell AC-activity (3.2-3.4 pmoles cAMP/mg protein/min) was found in the adult testes with normal germ cell morphology. Furthermore, low but significant AC-activity (0.2-0.8 pmoles cAMP/mg protein/min) was noted in biopsies containing only primary spermatocytes. There was no Mn2+ dependent AC-activity in Sertoli cell only testes or in testes where only spermatogonia were observed. Treatment with hCG did not influence germ cell maturation or soluble Mn2+ dependent AC-activity.

Adenylyl Cyclases↗
PubMed1984

Soluble Mn2+-dependent adenylate cyclase activity in the testis of the blue fox (Alopex lagopus).

Soluble Mn2+-dependent adenylate cyclase (MnAC) activity was found in testicular cytosol from blue foxes castrated during the breeding season. The rate of MnAC activity was approximately constant for 30 min at 35 degrees C and for 2 hr after storage at 25 degrees C. Activity was directly proportional to cytosol protein concentration and was optimal in the physiological pH range. Enzyme activity declined in the presence of an alkylating agent (N-ethyl maleimide, NEM) and was eliminated at a concentration of 1 mM NEM. Low concentrations (0.1-10 mM) of a reducing agent (beta-mercapto ethanol, beta ME) did not increase MnAC activity, whereas a high concentration (100 mM) led to a significant reduction (p less than 0.01) in activity. Substitution of Mn2+ in the assay medium with Mg2+ led to a total loss of enzyme activity, which could not be regained by adding hormones or by preincubation of cytosol for 60 min. The Km for Mn2+ was estimated to be 3.5 mM. The affinity of the enzyme for Mn2+ was not altered by varying the concentration of ATP. In contrast, increasing concentrations of Mn2+ appeared to increase the affinity of the enzyme for MnATP2-. The Km for MnATP2- thus varied from 6 to 18 mM.

Adenosine Triphosphate↗
PubMed1983

Thyroliberin receptor binding and adenylyl cyclase activation in cultured prolactin-producing rat pituitary tumor cells (GH cells).

A thyroliberin (TRH)-responsive particulate bound adenylyl cyclase is present in two rat anterior pituitary tumor cell strains (GH4C1 and GH3) which synthesize and secrete prolactin. At a given Mg2+ concentration, ATP and the guanyl nucleotides GTP and guanyl 5'-yl-imidodiphosphate (GMP-P(NH)P) caused a dose-dependent increase in adenylyl cyclase activity. The maximum response to thyroliberin occurred with ATP and GTP at concentrations above 0.30 mM and 2 microM, respectively. The maximal stimulatory effect of thyroliberin on adenylyl cyclase activity was 2-fold in the presence of GTP. GMP-P(NH)P increased the basal enzyme activity 4- to 10-fold over and above that of equimolar concentrations of GTP but supported poorly the TRH-induced response. Mg2+ caused a dose-dependent increase in the basal enzyme activity and reduced TRH and fluoride-induced responses. Also, Mn2+ and Co2+ stimulated the basal adenylyl cyclase activity while Zn2+, Ca2+, and Cu2+ inhibited the enzyme, and neither cations supported the TRH response. Half-maximal stimulation of the adenylyl cyclase by TRH and half-maximum binding of [3H]TRH to membranes at 35 degrees C were 102 and 56 nM, respectively. Pretreatment with TRH decreased the apparent Vmax of the enzyme and the maximal binding of [3H]TRH. Of 6 TRH analogs tested, only one was able to displace [3H]TRH from its receptor and to increase the adenylyl cyclase activity. We suggest that adenylyl cyclase activation is an early event in the stimulus secretion coupling between TRH and prolactin-producing GH cells.

Adenylyl Cyclases↗
PubMed1983

Developmental pattern and sensitivity to down-regulation of testicular LH receptors in the pig.

Testicular receptors for luteinizing hormone (LH) were quantified in 40 pigs between the day of birth and 22 weeks of age. The highest specific binding capacity (fmol hLH bound/mg protein) occurred at about 2--3 weeks of age which coincides with the age when the relative volume of Leydig cells is at a maximum. Significantly lower binding capacity was observed at 7 weeks of age which is the time of maximum Leydig cell regression. hCG was injected intramuscularly to immature (3000 IU, 22 days old) and adult boars (10 000 IU, 30--40 weeks old). Twentyfour h after injection the numbers of available LH receptors were reduced to 6 and 18% of control values, respectively. At this time occupied receptors were at a maximum (90% and 67% of controls, respectively). The total number of LH receptors (available + occupied) was increased 1 h after injection after which a gradual decrease was observed. Three days after hCG administration the total receptor quantities were at a minimum in both immature and adult pigs (59% and 31% of controls, respectively) and returned to control levels 5--7 days after treatment. Thus, pig LH receptors appear to be subjected both 'positive' and 'negative' regulation as previously described in the rat.

Aging↗
PubMed1983

Receptors for luteinizing hormone (LH) and follicle stimulating hormone (FSH) in the human undescended testis and the effect of hCG-treatment.

Human testis tissue contains specific receptors for luteinizing hormone (LH) and follicle stimulating hormone (FSH) with Ka's of 1.5 and 1.6 X 10(9) M-1, respectively. Specific binding of [125I]hLH and [125I]hFSH was studied in testicular biopsies from 33 boys (4-16 years of age) with undescended testes and in 2 adult men with normally descended testes. Ten of the boys were treated with human chorionic gonadotrophin (hCG) and operated 1-4 days after the last injection. Samples from each testis were taken for histological evaluation. Specific binding of LH in biopsies from pre-pubertal boys (stage I) was low and differentiated Leydig cells could not be identified histologically. In later pubertal stages the LH binding increased and differentiated Leydig cells could now be recognized. hCG-treatment caused a highly significant increase (P less than 0.001) in the binding of LH without affecting FSH binding. The highest binding of FSH occurred during the onset of puberty. Treatment with hCG did not cause premature differentiation of Sertoli cells or germ cells, but appeared to stimulate Leydig cells.

Adolescent↗
PubMed1983

Effects of FSH, isoproterenol, and cyclic AMP on the production of lactate and pyruvate by cultured Sertoli cells.

We have examined the hormonal regulation of the secretion of lactate and pyruvate from cultured rat Sertoli cells. FSH and isoproterenol caused 3-6-fold stimulation of lactate and pyruvate secretion, whereas ovine LH, TSH, and prolactin were ineffective. Dibutyryl cyclic AMP (10(-4) M) stimulated the secretion of lactate and pyruvate to the same extent as FSH. Much lower stimulation was observed when Sertoli cells from 43-day old rats were exposed to FSH or isoproterenol. FSH increased lactate secretion in a concentration-dependent manner. The concentration of FSH (NIH-S14) causing half-maximal stimulation of lactate secretion (150 ng/ml) was similar to that causing 50% maximal stimulation of Sertoli cell adenylyl cyclase. Both FSH and isoproterenol caused a time-dependent increase in lactate levels in the incubation medium during the first 6-9 hr after the addition of hormones, after which levels were constant or decreased. Thus, the production of lactate and pyruvate by cultured Sertoli cells is stimulated both by FSH and isoproterenol and these effects are exerted via cyclic AMP.

Animals↗
PubMed1982

Relationship between stimulated prolactin release from GH cells and cyclic AMP degradation and formation.

We have studied the relationship between the prolaction (PRL) release induced by thyroliberin (TRH) and theophylline and the formation and inactivation of adenosine 3', 5'-cyclic monophosphate (cyclic AMP) in cultured rat-pituitary cells (GH3 cells). TRH, which stimulated prolactin release, increased cyclic AMP formation and stimulated transiently both the low- and high-Km cyclic phosphodiesterases. The maximal effect on the phosphodiesterase was observed at 30 mM TRH. The stimulatory effect of TRH on the activity of the cyclic AMP phosphodiesterases was duplicated by incubation of the cells with cyclic AMP (2-10 mM). In washed particulate GH3 cell fractions, TRH increased the adenylyl cyclase activity up to 180%. Treatment of GH3 cells with theophylline stimulated the release of PRL and inhibited cyclic AMP degradation probably leading to the measured increase in cellular concentrations of the nucleotide. The effects of TRH and theophylline on cellular cyclic AMP concentrations and on PRL release were additive. There was a positive correlation between PRL release and cellular cyclic AMP concentration (r = 0.97). The elevations observed in cellular cyclic AMP concentration after TRH treatment are due to increased formation which in turn leads to phosphodiesterase activation. Therefore, cyclic AMP formation appears to be an intermediary step in the stimulus-secretion coupling caused by the tripeptide.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1982

Rat sperm enzymes during epididymal transit.

The activities of cAMP and cGMP phosphodiesterases (EC 3.1.4.1), adenylate cyclase (EC 4.6.1.1) and protein carboxyl-methylase (EC 2.1.1.24) were measured in the particulate and soluble (105 000 g supernatant) fractions of washed spermatozoa isolated from five segments of the adult rat epididymis. The activities of both phosphodiesterases decreased during epididymal transit, whereas adenylate cyclase and protein carboxyl-methylase underwent a progressive increase, the latter showing the most marked alteration. Both cAMP and cGMP phosphodiesterases as well as the adenylate cyclase were all associated primarily with the particulate fraction, and the extent to which these enzymes were associated with the membranes increased as the spermatozoa passed through the epididymis. Sperm protein carboxyl-methylase activity was, on the other hand, predominantly soluble in all segments of the epididymis. Adenylate cyclase, cAMP phosphodiesterase and protein carboxyl-methylase activities were found predominantly in the sperm tails, whereas cGMP phosphodiesterase was equally distributed between heads and tails. These observations imply that the acknowledged increase in intracellular cAMP levels which occurs in spermatozoa during epididymal transit may be a consequence of both increased synthesis (adenylate cyclase) and reduced hydrolysis (phosphodiesterase).

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1982

Stage dependent variation in Mn2+-sensitive adenylyl cyclase (AC) activity in spermatids and FSH-sensitive AC in sertoli cells.

The variation of the specific Mn2+-dependent adenylyl cyclase (AC activity in spermatids and follicle stimulating hormone (FSH)-responsive AC activities in Sertoli cells in different stages (I-XIV) of the seminiferous epithelial cycle has been investigated. Maximal Mn2+-dependent AC activity was observed in stages II-III while minimal activity was encountered in stages VII-VIII (spermiation). FSH-responsive AC activity exhibited a pattern that coincided with that of the Mn2+-dependent AC. The stage-dependent variation in spermatid AC activity cannot be explained by altered numbers of haploid cells. This raises the question whether the Sertoli cells may regulate the spermatid AC activity. Sertoli cells in various stages are all exposed to the same concentration of circulatory hormones. Hence the stage-dependent difference in FSH-responsiveness indicates that local influences (from germ cells?) may regulate the response of the AC in Sertoli cells to FSH.

Adenylyl Cyclases↗
PubMed1982

Cellular localization of the Mn2+-dependent adenylyl cyclase in the human testis.

An examination of the activity of the Mn2+-dependent adenylyl cyclase (AC) in fine needle biopsies from human testes was made. Simultaneously the DNA distribution patterns in suspensions of testicular cells derived from the same patients have been determined. The DNA distribution patterns were estimated by microflow fluorimetry (MFF) after straining with fluorochrome (ethidium bromide). Thus, AC activity could be assessed and correlated with the relative number of haploid (1C = spermatids), diploid (2C = spermatogonia and testicular somatic cells), and tetraploid (4C = primary spermatocytes) cells. Testicular Mn2+-dependent AC activities varied between 0 and 8.4 pmol cyclic adenosine monophosphate (cAMP)/mg protein/min and were highly correlated with the contents of haploid (1C) germ cells (spermatids) (r = 0.62, p less than 0.01). There was no correlation between Mn2+-dependent AC activity and diploid or tetraploid cells. This indicates that the Mn2+-dependent AC activity in the human testis, like in the rat and mouse, may be exclusively localized to haploid germ cells. An inverse correlation between plasma FSH and Mn2+-dependent AC activities indicated reduced inhibin secretion in situations where the Sertoli cells did not maintain the testicular germ cell production.

Adenylyl Cyclases↗
PubMed1982

Desensitization of FSH-responsive adenylyl cyclase in cultured immature Sertoli cells by homologous hormone.

Sertoli cell monolayers were prepared from 19-day-old rat testes. On day 7 of culture cells were incubated for 24 hr in the presence or absence of ovine follicle stimulating hormone (oFSH). Cells were harvested, and adenylyl cyclase responses of the membrane particles to FSH, human chorionic gonadotropin (hCG), isoproterenol, and fluoride (F-) were examined in the presence of either GTP or the nonhydrolyzable guanylyl nucleotide GMP-P(NH)P. Culturing the cells in presence of FSH caused a hormone specific desensitization of FSH-responsive adenylyl cyclase, whereas responses to isoproterenol and fluoride were unaffected. Activation of Sertoli cell adenylyl cyclase by GTP and GMP-P(NH)P showed no difference between cells preincubated with or without FSH, indicating that FSH did not change the activity of the G/F (or N) component or its interaction with the catalytic subunit of the adenylyl cyclase. FSH-responsive adenylyl cyclase in cultured Sertoli cells has been shown to be selectively desensitized by homologous hormone. The mechanism may involve alteration or loss of the FSH receptor or changes in the "coupling" of the FSH receptors to the G/F component of the adenylyl cyclase, since there was no alteration in the guanylyl nucleotide and fluoride activation.

Adenylyl Cyclases↗
PubMed1982

Adenylyl cyclase and protein carboxyl methylase in human spermatozoa.

Adenylyl cyclase (AC) and protein carboxyl methylase (PCM) activities in human ejaculated spermatozoa were measured in 31 men being evaluated for infertility at the Infertility Clinic. The spermatozoal Mn2+-sensitive AC activities ranging between zero and 1.4 nmol cyclic adenosine monophosphate (cAMP)/10(9) cells/min, was positively correlated with motility index [% motile sperm X degree (0-4)] (r = 0.72, rho less than 0.05). This confirms a role for cAMP in human sperm motility. PCM activities, ranging between zero and 160 pmoles (CH3OH/10(9) cells/min), were significantly correlated with AC activities (r = 0.86, p less than 0.001). However, PCM activities were not positively correlated with motility index (p = 0.065). PCM most probably is a factor involved in spermatozoal motility since two patients suffering necrospermia possessed spermatozoa deficient in both AC and PCM activities.

Adenylyl Cyclases↗
PubMed1982

Changes in protein carboxyl-methylase isoenzymes during testicular development in the rat.

Measurements of total rat testicular protein carboxyl-methylase (PCM) activity at various ages ranging from 10 to 90 days showed a rapid (fivefold) increase between 20 and 30 days, coincident with the occurrence of haploid germ cells. When partially purified testicular enzyme, at different ages, was fractionated by isoelectric focusing, the activity of the individual PCM isomers displayed clear differences in the time at which maximal activity was reached. The most acid PCM isoenzyme (pI 6.1) was the dominant isoform in the immature testis and exhibited the highest increase in activity between 20 and 30 days of age. During the same age interval, the activity of the other two isoenzymes (pI 6.7 and 7.4) increased only slightly. At 50 days, while the isofocusing profile revealed no additional increase in the activity of the acid isoform (pI 6.1) and only a doubling in the activity of the second isomer (pI 6.7), the most basic isoenzyme displayed a drastic increment in specific activity (approximately sixfold when compared to 30 days). This indicates that the PCM isozymes have different cellular localization in the seminiferous tubules. The acid isomer (pI 6.1) appears to be associated to the early stages of spermatogenesis and may represent both germ cell and somatic cell PCM. The basic isomer (pI 7.4) may be specific for germ cells (spermatids), and is most likely associated with the later stages of germ cell maturation.

Animals↗
PubMed1982

Particulate and solubilized LH receptor in the pig and bull testis.

Particulate and Triton X-100 solubilized receptors for luteinizing hormone (LH) in the pig and bull testis were studied. In some of the experiments tissue from the rat testis was included for comparison. LH receptors in the bull and pig revealed very similar association and dissociation kinetics, affinity (Kd = 1.2-1.8 x 10(-10) M), stability and physicochemical properties. Binding capacity was higher in the pig (73 fmol/mg protein) than in the rat (33 fmol/mg protein) and bull (17 fmol/mg protein). Hormone binding stabilized the receptor against thermal denaturation and temperature stability decreased upon solubilization. It is concluded that the properties of the testicular LH receptor of the pig and bull are very similar to those previously described from the rat.

Animals↗