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At least 793 records · Page 44Linked to original sources
PubMed1998

Effects of F-1394, an acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, on ACAT activity in HepG2 cells and on hepatic secretion of lipids in Triton WR-1339-induced hyperlipidemic rats: possible role of hepatic ACAT in very low density lipoprotein secretion.

We examined the inhibitory potency of F-1394 ((1S,2S)-2-[3-(2,2-dimethylpropyl)-3-nonylureido]cyclohexane -1-yl 3-[(4R)-N-(2,2,5,5-tetramethyl-1,3-dioxane-4-carbonyl)amino]propionate), an acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, on ACAT activity and its hypolipidemic effect. F-1394 inhibited whole-cell ACAT activity in HepG2 cells with an IC50 value of 42 nM. The potency of F-1394 was greater than that of the five other ACAT inhibitors tested (YM-17E, CI-976, 57-118, CL-277,082 and DL-melinamide). In rats made hyperlipidemic by Triton WR-1339, F-1394 caused a reduction in the hepatic secretion rate of cholesterol. These data suggest that inhibition of hepatic ACAT activity helps to reduce very low density lipoprotein secretion from the liver into the circulation.

Animals↗
PubMed1985

Hyperthyroidism caused by a pituitary thyrotrophin-secreting tumour with excessive secretion of thyrotrophin-releasing hormone and subsequently followed by Graves' disease in a middle-aged woman.

A 46-year-old woman had signs of thyrotoxicosis and galactorrhoea. Serum immunoreactive TSH and its alpha-subunit increased in the presence of high serum triiodothyronine (T3), thyroxine (T4), and free T4 concentrations, whereas beta-subunit TSH was undetectable. Exogenous TRH failed to increase serum TSH. Serum TSH was markedly suppressed by glucocorticoid, but was increased by antithyroid drug. L-Dopa or bromocriptine partially suppressed, but nomifensine had no influence on serum TSH. Serum prolactin (Prl) was above normal and markedly increased by TRH, but depressed by bromocriptine and not suppressed by nomifensine. Plasma TRH was normal in the hyperthyroid state, but was increased by glucocorticoid and antithyroid drug. Excess thyroid hormone depressed plasma TRH concentrations. Basal serum GH levels were constantly low. Transsphenoidal removal of the tumour normalized serum hormones (T3, T4 free T4, TSH, alpha-subunit and Prl), and eradicated the clinical signs of hyperthyroidism and galactorrhoea. Histological study of the tumour tissue demonstrated both thyrotrophes and somatotrophes. A reciprocal relationship between serum TSH and T4 concentrations shifted to a higher level before but was normalized after removal of the tumour. Ten months later, the clinical signs of thyrotoxicosis and the increase in serum thyroid hormone recurred without a concomitant increase in serum TSH and its alpha-subunit. Thyroidal auto-antibodies were slightly positive, but thyrotrophin-binding inhibitor immunoglobulin (TBII) was negative. Administration of antithyroid drug produced a euthyroid state, but 3 years later, discontinuation of the treatment resulted in recurrent hyperthyroidism without suppressed plasma TRH and with no evidence of regrowth of the pituitary tumour. It is suggested that the patient initially had hyperthyroidism owing to excessive TSH secretion from the tumour caused by abnormal TRH secretion, and subsequently had hyperthyroidism owing to Graves' disease.

Adenoma↗
PubMed2003

During a corticotropin-releasing hormone test in healthy subjects, administration of a beta-adrenergic antagonist induced secretion of cortisol and dehydroepiandrosterone sulfate and inhibited secretion of ACTH.

OBJECTIVE: In chronic inflammatory diseases, serum levels of dehydroepiandrosterone (DHEA) sulfate (DHEAS) are low. Interestingly, several non-inflammatory diseases display similarly low levels of DHEAS which points to other inhibitory factors such as an activated sympathetic nervous system (SNS) (e.g. in patients with heart failure, fibromyalgia, or cancer cachexia). We aimed to identify the influence of the SNS tone on stimulated adrenal steroid secretion in 16 male and 12 female healthy subjects. METHODS: One group were given oral propranolol 2 h before a corticotropin-releasing hormone (CRH) test, and levels of adrenocorticotropin (ACTH), cortisol, 17-hydroxyprogesterone (17OHP), androstenedione, DHEA, and DHEAS were measured. RESULTS: Propranolol treatment decreased heart rate (by 20%), diastolic blood pressure (by 20%), and plasma ACTH, and increased serum cortisol, serum DHEAS, and the molar ratio of cortisol/17OHP, cortisol/DHEA, and DHEAS/DHEA similarly in female and male subjects. CONCLUSIONS: A beta-adrenergic influence seems to decrease CRH-stimulated cortisol in relation to ACTH and 17OHP, and decreases DHEAS in relation to DHEA. Although other workers have found beta-adrenergic stimulation of steroid secretion in cultured adrenocortical cells, the overall systemic influence of the SNS via beta-adrenoceptors seems to inhibit adrenal steroids under unstimulated and stimulated conditions. Sympathetic hyperactivity may be a common denominator for low levels of DHEAS in inflammatory and non-inflammatory diseases.

17-Hydroxysteroid Dehydrogenases↗
PubMed2005

Efficacy of chimeric molecules directed towards multiple somatostatin and dopamine receptors on inhibition of GH and prolactin secretion from GH-secreting pituitary adenomas classified as partially responsive to somatostatin analog therapy.

OBJECTIVE: This study compared the potency of a somatostatin receptor (sstr)2-sstr5 analog, BIM-23244, of an sstr2-dopamine D2 receptor (sstr2-DAD2) molecule, BIM-23A387 and of new somatostatin-dopamine chimeric molecules with differing, enhanced affinities for sstr2, sstr5 and DAD2, BIM-23A758, BIM-23A760 and BIM-23A761, to suppress GH and prolactin (PRL) from 18 human GH adenomas that are partially responsive to octreotide or lanreotide. MATERIALS AND METHODS: The sstr2, sstr5 and DAD2 mRNA levels were determined by RT-PCR. The effect of drugs was tested in cell cultures at various concentrations. RESULTS: In all tumors, the sstr2, sstr5 and DAD2 mRNA levels were coexpressed (mean levels+/-s.e.m. 0.4+/-0.1, 5.3+/-1.9 and 2.0+/-0.4 copy/copy beta-glucuronidase). In 13 tumors, the maximal suppression of GH secretion produced by BIM-23A387 (30+/-3%) and BIM-23244 (28+/-3%) was greater than that produced by octreotide (23+/-3%). In six out of 13 tumors, BIM-23A758, BIM-23A760 and BIM- 23A761 produced greater maximal suppression of GH secretion than octreotide (33+/-5, 38+/-2 and 41+/-2 vs 24+/-2%). Their EC(50) values were 10, 2 and 4 pmol/l. BIM-23A761 was more effective than BIM-23A387 in GH suppression (41+/-2 vs 32+/-4%). The new chimeric molecules produced maximal PRL suppression greater than octreotide (62+/-8 to 74+/-5 vs 46+/-11%). CONCLUSIONS: Novel dopamine-somatostatin chimeric molecules with differing, enhanced activity at sstr2, sstr5 and DAD2, consistently produced significatly greater suppression of GH and PRL than either octreotide or single-receptor-interacting ligands in tumors from patients classified as only partially responsive to octreotide therapy. The higher efficacy of the chimeric compounds was, at least partially, linked to their high affinity for sstr2 (IC50 1-10 pmol/l). The other mechanisms by which such molecules produce an enhanced inhibition of GH remain to be elucidated.

Acromegaly↗
PubMed1988

Effect of the peripubertal pattern of LH and FSH secretion on in-vitro oestradiol-17 beta secretion and follicular growth within juvenile rat ovaries.

Juvenile rat ovaries were placed in perfusion culture and exposed to (1) no gonadotrophin, (2) tonic NIH-FSH (200 ng RP-1 equiv./ml) or (3) NIH-FSH + NIH-LH pulses (2/h, amplitude = 80 ng RP-1 equiv./ml). After 3 h of perifusion, the ovaries were prepared for histological analysis and the perifusate assayed for oestradiol-17 beta. Since the NIH-FSH preparation is contaminated with LH, a second experiment was conducted using recombinant bovine LH and FSH. Ovaries were perifused for 3 h with (1) no hormones, (2) recombinant FSH (200 ng/ml) or (3) recombinant FSH plus 25 ng recombinant LH/ml. NIH-FSH alone increased the number of mid-size antral follicles (P less than 0.05) and decreased the number of small antral follicles (P less than 0.05). Pulsatile LH in the presence of FSH increased the number of mid-size antral follicles without reducing the number of small antral follicles. Studies with recombinant FSH and LH demonstrated that both FSH and LH are necessary to stimulate follicles to grow, indicating that the growth-promoting property of the NIH-FSH is due to the presence of both FSH and LH. Regardless of whether NIH or recombinant gonadotrophins were used, follicular growth was induced without increasing oestradiol secretion. These results demonstrate that enhanced oestradiol secretion is not essential for the induction of follicular growth, while both LH and FSH are necessary to stimulate small antral follicles to grow into mid-size antral follicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Tissue kallikrein is associated with prolactin-secreting cells within human growth hormone-secreting adenomas.

Tissue kallikrein is a serine protease which may be involved in the intracellular processing of prolactin in the anterior pituitary gland. The expression of tissue kallikrein, in the rat, is promoted by oestrogen and inhibited by dopamine. Human and rat prolactinomas contain markedly increased amounts of tissue kallikrein; this is comparatively reduced if patients are pretreated with the dopamine agonist, bromocriptine, before surgery. Some GH-secreting adenomas are mixed and also contain prolactin-secreting cells. We therefore investigated 27 GH-immunostaining human pituitary adenomas for the presence of immunoreactive tissue kallikrein. Sixteen of the adenomas had positive immunostaining for prolactin; eight of these patients had associated clinical hyperprolactinaemia before the tumour was removed. Tissue kallikrein immunoreactivity was found in ten adenomas, all of which also had prolactin immunopositivity. There was a close relationship between the percentage of cells staining for prolactin and tissue kallikrein but not for GH. A further eight adenomas had patchy positivity, i.e. less than 1% of cells immunostained for tissue kallikrein and six of these also had some prolactin-staining cells. Nine out of eleven purely GH-staining adenomas had no tissue kallikrein immunopositivity, the remaining two showing patchy staining. A review of bromocriptine responsiveness, as assessed by mean GH hormone levels during oral glucose tolerance tests before and after therapy was commenced, indicated that patients with adenomas which stained for prolactin and tissue kallikrein were more likely to respond to bromocriptine than those which failed to do so.

Adenoma↗
PubMed1993

Growth hormone secretion in the horse: unusual pattern at birth and pulsatile secretion through to maturity.

A heterologous radioimmunoassay was developed and validated for the measurement of horse GH in plasma. It utilized recombinant-derived bovine GH as the radiolabelled ligand, a guinea-pig anti-porcine GH serum as first antibody and pituitary-derived horse GH as standard. Cross-reactivities were high with all of the pituitary and recombinant-derived GH preparations tested (49-140%) and very low (< 0.3%) with horse FSH, LH and prolactin. A synthetic analogue of GH-releasing factor(1-29) stimulated the expected pattern of GH release in foals. Plasma GH concentrations in foals were low at birth (< 20 ng/ml) but rose sharply to a definite and, in most cases, very large peak (18-195 ng/ml) during the first 30-40 min post partum, followed by a steady decline to basal levels again by 60-100 min post partum. GH secretion was clearly pulsatile in all older foals tested (2 weeks, 1 month and 4 months of age) and in six adults (three mares and three stallions), all bled at 15-min intervals for 7-8 h. Basal levels and pulse amplitudes were higher in foals than in adults and pulse frequency was higher in stallions than in mares (3-5 pulses/8 h vs 1-2 pulses/8 h). Pulsatile secretion was further characterized in one mare by simultaneous sampling of jugular vein and pituitary cavernous sinus blood. Peak GH concentrations in cavernous sinus blood draining the pituitary gland were more than tenfold higher than the corresponding peak concentrations in peripheral circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1993

Glucagon-like peptide-1 (7-36)amide and glucose-dependent insulinotropic polypeptide secretion in response to nutrient ingestion in man: acute post-prandial and 24-h secretion patterns.

The acute effects of different macronutrients on the secretion of glucagon-like peptide-1(7-36)amide (GLP-1(7-36)amide) and glucose-dependent insulinotropic polypeptide (GIP) were compared in healthy human subjects. Circulating levels of the two hormones were measured over a 24-h period during which subjects consumed a mixed diet. In the first study, eight subjects consumed three equicaloric (375 kcal) test meals of carbohydrate, fat and protein. Small increases in plasma GLP-1(7-36) amide were found after all meals. Levels reached a maximum 30 min after the carbohydrate and 150 min after the fat load. Ingestion of both carbohydrate and fat induced substantial rises in GIP secretion, but the protein meal had no effect. In a second study, eight subjects consumed 75 g glucose or the equivalent portion of complex carbohydrate as boiled brown rice or barley. Plasma GIP, insulin and glucose levels increased after all three meals, the largest increase being observed following glucose and the smallest following the barley meal. Plasma GLP-1(7-36)amide levels rose only following the glucose meal. In the 24-h study, plasma GLP-1(7-36)amide and GIP concentrations were increased following every meal and remained elevated throughout the day, only falling to fasting levels at night. The increases in circulating GLP-1(7-36)amide and GIP levels following carbohydrate or a mixed meal are consistent with their role as incretins. The more sustained rises observed in the daytime during the 24-h study are consistent with an anabolic role in lipid metabolism.

Adult↗
PubMed1994

Effects of pituitary-gonadal suppression with a gonadotrophin-releasing hormone agonist on fetal gonadotrophin secretion, fetal gonadal development and maternal steroid secretion in the sheep.

In order to investigate the regulation of the hypothalamo-pituitary-gonadal axis during fetal development, sheep fetuses at day 70 of gestation were implanted subcutaneously with a biodegradable implant containing the long-acting gonadotrophin-releasing hormone (GnRH) agonist, buserelin. The treatment of fetuses with a GnRH agonist throughout the last half of gestation (term = 145 days) abolished the increase in plasma LH concentrations that was seen in 2-day-old control lambs in response to an injection of GnRH. This attenuated response was associated with corresponding reductions in the pituitary content of LH and FSH. Immunolocalization studies revealed that pituitary glands from newborn lambs implanted with a GnRH agonist during fetal development were devoid of immunopositive LH- and FSH-containing cells. At birth the testicular weights of GnRH agonist-treated ram lambs were significantly decreased by 40% when compared with controls. This was associated with a 45% reduction in the total number of Sertoli cells per testis. In newborn ewe lambs GnRH agonist treatment had no effect on ovarian weight or on the morphological appearance of the ovaries. GnRH agonist treatment had no effect on the plasma concentrations of progesterone and oestrone in the maternal circulation or on the length of gestation. These results show (1) that GnRH positively regulates the synthesis and secretion of gonadotrophins in the fetus, (2) that reduced fetal gonadotrophic support during the last half of gestation results in a reduction in testicular growth, and (3) that fetal gonadotrophins do not affect maternal steroid secretion.

Animals↗
PubMed1997

Ontogeny of inhibin secretion in the rat testis: secretion of inhibin-related proteins from fetal Leydig cells and of bioactive inhibin from Sertoli cells.

The ontogeny of inhibin secretion in the testis of rats was investigated. Testicular localization, content of immunoactive and bioactive inhibin and its molecular size in fetal and neonatal rats (from 16 days of gestation to 5 days of age) were determined. Strong immunostaining with an antiserum against a polypeptide of porcine inhibin alpha-subunit was noted in testicular interstitial cells from 16 days of gestation. Co-localization of inhibin alpha-subunit and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) was observed in the interstitial cells until 2 days of age. Immunoreactive inhibin alpha-subunit in the interstitial tissue had disappeared by 5 days of age, although 3 beta HSD-positive cells were still detected. Weak immunostaining for the inhibin alpha-subunit was detected in the seminiferous tubules, probably in the cytoplasm of Sertoli cells, from 20 days of gestation onward. No inhibin alpha-subunit immunostaining was observed in germ cells throughout the experimental period. Testicular inhibin was detected at 16 days of gestation (49.5 +/- 6.7 pg per testis) by RIA. Testicular immunoreactive inhibin showed a tendency to increase during fetal life and levels were maintained at a similar value after birth (697.0 +/- 46.9 pg per testis at 5 days of age). Inhibin bioactivity and its molecular size in testicular homogenate was examined at 17 days of gestation and 0 and 5 days of age. Although no bioactivity was detected at 17 days of gestation, bioactivity was noted at 0 and 5 days of age (177.7 and 1303.9 pg per testis respectively). Immunoblot analysis with antiserum against inhibin alpha-subunit revealed only approximately 40 kDa molecular masses in the testis at 17 days of gestation, probably inhibin-related proteins, but not inhibin. At 0 and 5 days of age, a protein of 30 kDa molecular mass, possibly inhibin, was detected as well as material of approximately 40 kDa molecular mass. FSH in the plasma was first detected at 19 days of gestation (1197.0 ng/l), increased towards birth, and thereafter decreased (4588.5 +/- 572.3 ng/l at 21 days of gestation and 2400.0 +/- 179.6 ng/l at 5 days of age). These results indicate that Leydig cells in fetal and neonatal rats produce inhibin-related substances with no inhibin bioactivity, whereas Sertoli cells begin to produce inhibin during the perinatal period as a possible regulator of FSH secretion.

3-Hydroxysteroid Dehydrogenases↗
PubMed2002

Influence of sex and gonadal status of sheep on cortisol secretion in response to ACTH and on cortisol and LH secretion in response to stress: importance of different stressors.

There are sex differences in the response to stress and in the influence of stress on reproduction which may be due to gonadal steroids but the nature of these differences and the role of the gonads are not understood. We tested the hypotheses that sex and the presence/absence of gonads (gonadal status) will influence the cortisol response to injection of ACTH, insulin-induced hypoglycaemia and isolation/restraint stress, and that sex and gonadal status will influence the secretion of LH in response to isolation/restraint stress. Four groups of sheep were used in each of three experiments: gonad-intact rams, gonadectomised rams, gonad-intact ewes in the mid-luteal phase of the oestrous cycle and gonadectomised ewes. In Experiment 1 (n=4/group), jugular blood samples were collected every 10 min for 6 h; after 3 h, two animals in each group were injected (i.v.) with ACTH and the remaining two animals were injected (i.v.) with saline. Treatments were reversed 5 days later so that every animal received both treatments. Experiment 2 (n=4/group) used a similar schedule except that insulin was injected (i.v.) instead of ACTH. In Experiment 3 (n=5/group), blood samples were collected every 10 min for 16 h on a control day and again 2 weeks later when, after 8 h of sampling, all sheep were isolated and restrained for 8 h. Plasma cortisol was significantly (P<0.05) elevated following injection of ACTH or insulin and during isolation/restraint stress. There were no significant differences between the sexes in the cortisol response to ACTH. Rams had a greater (P<0.05) cortisol response to insulin-induced hypoglycaemia than ewes while ewes had a greater (P<0.05) cortisol response to isolation/restraint stress than rams. There was no effect of gonadal status on these parameters. Plasma LH was suppressed (P<0.05) in gonadectomised animals during isolation/restraint stress but was not affected in gonad-intact animals, and there were no differences between the sexes. Our results show that the sex that has the greater cortisol response to a stressor depends on the stressor imposed and that these sex differences are likely to be at the level of the hypothalamo-pituitary unit rather than at the adrenal gland. Since there was a sex difference in the cortisol response to isolation/restraint, the lack of a sex difference in the response of LH to this stress suggests that glucocorticoids are unlikely to be a major mediator of the stress-induced suppression of LH secretion.

Adrenocorticotropic Hormone↗
PubMed1983

Effects of ovarian secretions and dopamine on secretion of luteinizing hormone and prolactin in ewes.

In the present study, effects of dopamine (DA) and ovarian secretions on release of luteinizing hormone (LH) and prolactin (PRL) were examined using two methods of withdrawal of progesterone. Eight to 10 d after estrus, 36 ewes were assigned to one of six treatments: 1) lutectomy; 2) lutectomy and DA; 3) ovariectomy; 4) ovariectomy and DA; 5) ovariectomy and estradiol-17 beta or 6) ovariectomy, estradiol-17 beta and DA. Estradiol-17 beta was administered by Silastic implants inserted during surgery. Immediately after surgery, ewes were infused iv with DA (6.6 micrograms X kg-1 X min-1) or saline for 48 h. Infusion of DA did not affect secretion of LH after surgical removal of the corpus luteum. In lutectomized ewes, concentrations of LH in serum increased between 0 and 12 h from .5 to 3.3 ng/ml, declined between 12 and 16 h and then plateaued at 1.1 to 1.5 ng/ml. In contrast, concentrations of LH in ovariectomized ewes increased between 0 and 12 h and then remained at 3 to 5 ng/ml. Surges of LH occurred between 40 and 50 h postsurgery in eight of 12 lutectomized ewes, 11 of 12 ovariectomized ewes with implants of estradiol-17 beta and zero of 12 ovariectomized ewes. The magnitude of the surge of LH was higher in lutectomized ewes than in ovariectomized ewes with implants of estradiol-17 beta. Infusion of DA inhibited release of PRL, but there was no effect of method of progesterone withdrawal. Lutectomized ewes, but not ovariectomized ewes with implants of estradiol-17 beta, had a surge of PRL associated with the surge of LH.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Renal renin secretion rate and norepinephrine secretion rate in response to centrally administered angiotensin-II: role of the medial basal forebrain.

The influence that centrally administered angiotensin-II (ANG-II) and saralasin (SAR) has on renal norepinephrine secretion rate (NESR) and renal renin secretion rate (RSR) were studied. Rats were given thermal lesions of the medial basal forebrain (MBF) or sham surgery. Twenty-four hours later the right kidney was vascularly isolated (but neurally intact) and perfused with an artificial plasma at either a constant pressure (100 mm Hg) or constant flow (600 microliters/min). Renal perfusate was collected before (pre-injection) and at 10 min intervals after central administration of peptides for determination of NESR and RSR. In both perfusion models, intracerebroventricular (ICV) ANG-II increased renal NESR. In MBF lesioned rats pre-injection renal NESR is reduced and the response to ICV ANG-II is blocked. In both perfusion models ICV ANG-II decreases renal RSR. Concomitant administration of SAR blocks the effect of ANG-II on both NESR and RSR. MBF lesioned rats had significantly elevated pre-injection levels of RSR and there is no change in RSR following ICV ANG-II. These experiments indicate that centrally administered ANG-II increases renal NESR concomitant with a decrease in renal RSR and that MBF lesions block those changes.

Angiotensin II↗
PubMed2001

Cutting edge: FISP (IL-4-induced secreted protein), a novel cytokine-like molecule secreted by Th2 cells.

Th cell subsets, namely Th1 and Th2 cells, play an important role in mounting an immune response against invading pathogens. Several genes are selectively up-regulated during differentiation and effector phases of Th subsets. In this study, we report the identification of a novel cytokine-like molecule designated FISP (IL-4-induced secreted protein), which is selectively expressed and secreted by Th2 cells. Detectable levels of FISP are observed only 3 days after initiation of Th2 differentiation. Expression of FISP in developing Th cells requires at least two signals: TCR signaling involving protein kinase C activation and STAT6-dependent IL-4R signaling.

Amino Acid Sequence↗
PubMed2000

Enzymes secreted by filamentous fungi: regulation of secretion and purification of an extracellular protease of Trichoderma harzianum.

Extracellular proteases secreted by the filamentous fungus Trichoderma harzianum have been identified. A proteinase active towards Z-Ala-Ala-Leu-pNa--the substrate of subtilisin-like proteases--dominated in the culture medium. This proteinase is synthesized de novo in response to addition of a protein substrate to the medium. Changing the carbohydrate in the culture medium changed the quantitative and qualitative spectrum of secreted enzymes. The most active extracellular proteinase of Trichoderma harzianum was purified 322-foldfrom the culture medium and obtained with a yield of 7.2%. The molecular mass of this proteinase is 73 kD and its pI is 5.35. The isolated enzyme has two distinct activity maxima, at pH 7.5 and 10.0, and is stable in the pH range 6.0-11.0. The temperature optimum for enzyme activity is 40 degrees C at pH 8. 0. The proteinase is stable up to 45-50 degrees C (depending on the substrate used). Calcium ions stabilized the enzyme at 55-60 degrees C. According to data on the study of functional groups of the active center and substrate specificity, the enzyme isolated from the culture medium of Trichoderma harzianum is a subtilisin-like serine proteinase.

Chromatography, Ion Exchange↗
PubMed1990

Stimulated pepsinogen secretion from dispersed abomasal glands exposed to Ostertagia species secretion.

Carbachol and secretions from Ostertagia species parasites significantly (P less than 0.001) stimulated isolated preparations of dispersed gastric glands from bovine and ovine abomasal mucosa to secrete pepsinogen. Atropine reduced the response to both secretagogues. Live adult and larval stages of Ostertagia ostertagi and O circumcincta and homogenates of these parasites did not significantly (P greater than 0.05) increase pepsinogen production from bovine or ovine gland preparations.

Abomasum↗
PubMed1990

Endogenously secreted IL-4 is required for mouse thymocytes to become cytotoxic. Human, but not mouse, IL-2 induces a functionally immature thymic subset to secrete IL-4 and become CTL.

Experiments described here demonstrate that the differentiation of mouse thymocytes into cytotoxic T lymphocytes (CTL) requires interleukin-4 (IL-4). To reach this conclusion, we took advantage of our discovery that human and mouse IL-2 have very different effects on the development of CTL from a functionally immature subset of thymocytes. The lobster agglutinin 1 (LAg1)-negative subpopulation of thymocytes proliferated when cultured with concanavalin A (Con A)+ human or mouse IL-2, but these cells became CTL only when cultured with Con A+ human IL-2. Furthermore, Con A+ human IL-2, but not mouse IL-2, stimulated IL-4 production by cells within this population. Con A-induced cytotoxicity by mature LAg1-positive thymocytes and normal thymocytes was also accompanied by secretion of IL-4. The anti-IL-4 mAb 11B11 inhibited induction of cytotoxicity by all thymocyte populations tested. Taken together these experiments indicate that stimuli which induce cytotoxicity by mouse thymocytes also induce the secretion of IL-4, which is necessary for the differentiation of thymocyte CTL precursors into CTL.

Animals↗
PubMed1988

Cells involved in the immune response. XXXVI. The thymic antigen-specific suppressor cell in the immunized rabbit is a T cell with receptors for FcG and the antigen and it acts, via a secreted suppressor factor, directly on the immune splenic AFC B cell to inhibit antibody secretion.

Following i.v. immunization of the normal outbred rabbit with sheep (SRBC) or horse (HRBC) erythrocytes, antigen-specific suppressor cells are generated in the thymus capable of inhibiting the generation of haemolytic plaques by the autologous or allogeneic splenic antibody-forming cells (AFC) in the plaque-forming cell (PFC) assay. These suppressor cells secrete an antigen-specific suppressor factor in short-term (4-24 hr) culture in vitro. The suppressor cells are not detected in the thymus prior to Day 4, exhibit peak activity between Days 5 and 11 post-immunization, and decline slowly thereafter. Suppressor cells can no longer be detected in the thymus by Day 60 postimmunization. Suppressor cells are not detected in any of the other lymphoid organs of the immunized rabbit nor in any lymphoid organ in the unimmunized rabbit. The thymic suppressor cell is a T cell with surface receptors for the antigen (SRBC or HRBC) and for FcG. On the other hand, the AFC B cells generated in the spleen of the immunized rabbit possess cell-surface receptors for only the antigen and not for FcG. Both the suppressor cells and the secreted suppressor factor act directly on the AFC B lymphocytes to inhibit the generation of antigen-specific haemolytic plaques in the PFC assay.

Animals↗