Somatostatin inhibits the mitogenic effect of thyroliberin.

The effect of somatostatin and of thyroliberin on the mitotic incidence in the organ-cultured anterior pituitary lobe of the rat was investigated, using the colchicine metaphase-arrest technique. It was found that somatostatin added to the culture medium, together with thyroliberin, blocked the mitogenic effect of the latter.     

Somatostatin inhibits in vitro release of luteinizing hormone releasing hormone from rat mediobasal hypothalamic slices

Summary Somatostatin, in concentrations ranging from 10^–10 M to 10^–7 M, induces a dose-dependent inhibition of LHRH release from mediobasal hypothalamic slices incubated in vitro. In contrast, VIP, secretin, glucagon, substance P, neurotensin and arginine-vasotocin do not affect spontaneous release of LHRH.     

Bio-assay and dose-response of the mitogenic activity of the phytohemagglutinin ofPhaseolus vulgaris

Zusammenfassung Es wird eine reproduzierbare, präzise Methode zur Untersuchung mitogenetischer Eigenschaften von Phytohämagglutininpräparaten beschrieben, die Methode beruht auf dem Einbau von radioaktiven Thymidin in DNS.     

Trans-4-hydroxy-3-methoxycinnamic acid (ferulic acid) inhibits the effect of androgens on the rat prostate

Summary Trans-4-hydroxy-3-methoxycinnamic acid (ferulic acid, FA) antagonized the effect of exogenous androgens on the ventral prostate (VP) in castrated rats as well as the effect of endogenous androgens in intact rats. FA, however, had no effect on the seminal vesicles (SV) and levator ani muscle (LAM), nor oestrogenic effect in female rats and mice. FA did not antagonize the receptor binding of testosterone nor inhibit the conversion of testosterone into 5-dihydrotestosterone (DHT).Supported in part by the project fund (grant 53-403) of Kawasaki Medical School.The authors would like to thank the Central Laboratory, Sankyo Pharmaceutical Co., Tokyo, for supplying 19-nortestosterone-17-ferulate.     

Species-specific differences in the mitogenic activity of heparin-binding growth factors in the sera of various mammals

Sera from different mammalian species displayed great differences in mitogenic activity, as measured by stimulation of DNA synthesis in BALB/c 3T3 cells (3T3 cells). Among the sera examined, fetal bovine serum was least active, and increasing activity was detected in calf serum, human serum, rat serum and mouse serum, in that order. Rat and mouse sera exhibited extremely high mitogenic activity with 3T3 cells, but when TIG-1 human fetal lung fibroblasts were used for the DNA assay instead, the activity levels of all of the sera were lower, and the differences between them were smaller. To determine the reasons for these differences, the heparin-binding growth factors in each serum were separated on a heparin affinity column. Five peaks of DNA-stimulating activity were obtained. Three of these were found in all sera examined, with both 3T3 cells and TIG-1 cells. Two other peaks were found only with 3T3 cells; one was peculiar to rat and mouse sera, with extremely high activity in the rat, and the other was specific to fetal serum. The dependence of the activity of these peaks on the cells used for the test was confirmed using normal rat lung fibroblasts and immortalized rat kidney cells. These findings adequately explain the species-specific differences in mitogenic activity of whole sera, and the variation in activity depending on the cells used for assay of DNA synthesis.     

Effect of a mitogenic concentration on membrane glycoconjugates of human lymphocytes

Periodate oxidation of human peripheral blood lymphocytes followed by reduction with 3H labelled sodium borohydride and acidic hydrolysis generates N-AN 7, glycerol and propane 1-2 diol. This indicates that sialyl, fucosyl and probably galactosyl residues are oxidized by periodate. Neuraminidase-treated lymphocytes exhibit decreased N-AN 7 levels, increased N-AN 8 levels and increased glycerol levels. Such results were neither found with mouse splenocytes nor with calf lymph node cells.     

Early changes of cyclic nucleotide levels in a mitogenic reaction in the rat mesentery

Summary By measuring simultaneously cAMP and cGMP we found a biphasic time course with regard to cGMP and the cGMP/cAMP ratio very early in a mitogenic reaction in vivo. This is a new finding.This work was supported by the Swedish Cancer Society and the Swedish Medical Research Council (project No. 04X-04498). We are indebted to Marcela Bartonek and Margareta Odenö for expert technical assistance and to Erik Leander for help with statistical matters.     

Trans-4-hydroxy-3-methoxycinnamic acid (ferulic acid) inhibits the effect of androgens on the rat prostate.

Trans-4-hydroxy-3-methoxycinnamic acid (ferulic acid, FA) antagonized the effect of exogenous androgens on the ventral prostate (VP) in castrated rats as well as the effect of endogenous androgens in intact rats. FA, however, had no effect on the seminal vesicles (SV) and levator ani muscle (LAM), nor oestrogenic effect in female rats and mice. FA did not antagonize the receptor binding of testosterone nor inhibit the conversion of testosterone into 5 alpha-dihydrotestosterone (DHT).     

Species-specific differences in the mitogenic activity of heparin-binding growth factors in the sera of various mammals.

Sera from different mammalian species displayed great differences in mitogenic activity, as measured by stimulation of DNA synthesis in BALB/c 3T3 cells (3T3 cells). Among the sera examined, fetal bovine serum was least active, and increasing activity was detected in calf serum, human serum, rat serum and mouse serum, in that order. Rat and mouse sera exhibited extremely high mitogenic activity with 3T3 cells, but when TIG-1 human fetal lung fibroblasts were used for the DNA assay instead, the activity levels of all of the sera were lower, and the differences between them were smaller. To determine the reasons for these differences, the heparin-binding growth factors in each serum were separated on a heparin affinity column. Five peaks of DNA-stimulating activity were obtained. Three of these were found in all sera examined, with both 3T3 cells and TIG-1 cells. Two other peaks were found only with 3T3 cells; one was peculiar to rat and mouse sera, with extremely high activity in the rat, and the other was specific to fetal serum. The dependence of the activity of these peaks on the cells used for the test was confirmed using normal rat lung fibroblasts and immortalized rat kidney cells. These findings adequately explain the species-specific differences in mitogenic activity of whole sera, and the variation in activity depending on the cells used for assay of DNA synthesis.     

Early changes of cyclic nucleotide levels in a mitogenic reaction in the rat mesentery.

By measuring simultaneously cAMP and cGMP we found a biphasic time course with regard to cGMP and the cGMP/cAMP ratio very early in a mitogenic reaction in vivo. This is a new finding.     

Somatostatin content and release of isolated pancreatic islets from obese-hyperglycemic mice

Summary The somatostatin content in pancreatic islets of obese-hyperglycemic mice was much lower than in the islets of normal mice. Also the release of somatostatin was decreased from the islets obtained from the obese-hyperglycemic mice. Tissue culture for 1 week changed neither the content of, nor the amount of somatostatin released from, the pancreatic islets.This work was supported by the Swedish Medical Research Council, Nordic Insulin Foundation, Swedish Diabetes Association, the Bergwalls stiftelse and the Anders Swärds stiftelse.     

Development and evaluation of a method of high pressure liquid chromatography for the determination of the level of degradation of thyroliberin (TRH) in blood]

The degradation of the TRH by plasma was studied using a sensitive method for the separation of TRH and products formed by high-pressure liquid chromatographic analysis (HPLC). The detected products are TRH-3H or synthetic TRH. The HPLC analysis is performed on a microparticulate (10 mu) silica gel chromatographic column with CH3CN/0,01 M NH4OAc, at pH 6 (30/70) (V/V). This technique provides a good separation of TRH and the other products of degradation. In our experimental conditions, the human plasma degrades 62.5 +/- 5% of of TRH in 60 mn; very similar results are obtained with thin layer chromatography.     

Somatostatin reduces the release of colony-stimulating activity (CSA) from PHA-activated mouse spleen lymphocytes

Summary PHA-activated lymphocytes release colony-stimulating activity (CSA) for macrophage-granulocyte precursor cells (colony forming units, CFU_C) in the culture medium. Somatostatin, known to interfer with ribosomal protein synthesis, was demonstrated to reduce the release of CSA from PHA-treated mouse spleen lymphocytes.The technical assistance of Ulrike Wallner and Paulette Bais is thankfully acknowledged.     

Reactivity in vitro of the leukocytes of the earthworm Eisenia foetida Sav. to several mitogenic substances]

Earthworm leukocytes were stimulated by various mitogens including LPS, PHA and Con A. Con A could stimulate leukocytes when they were cultivated in totality. After separation into sub-populations, small-non-adherent-leukocytes and large-adherent ones showed specific reactions with mitogens. Both PHA and LPS reacted with small leukocytes but LPS had no action on large adherent leukocytes.     

Somatostatin reduces the release of colony-stimulating activity (CSA) from PHA-activated mouse spleen lymphocytes.

PHA-activated lymphocytes release colony-stimulating activity (CSA) for macrophage-granulocyte precursor cells (colony forming units, CFUc) in the culture medium. Somatostatin, known to interfer with ribosomal protein synthesis, was demonstrated to reduce the release of CSA from PHA-treated mouse spleen lymphocytes.     

Somatostatin content and release of isolated pancreatic islets from obese-hyperglycemic mice.

The somatostatin content in pancreatic islets of obese-hyperglycemic mice was much lower than in the islets of normal mice. Also the release of somatostatin was decreased from the islets obtained from the obese-hyperglycemic mice. Tissue culture for 1 week changed neither the content of, nor the amount of somatostatin released from, the pancreatic islets.     

Somatostatin immunoneutralization overcomes the inhibitory effects of quipazine and pargyline on growth hormone secretion in domestic fowl

The inhibitory effects of pargyline and quipazine on chicken growth hormone secretion were overcome by passive immunoneutralization of endogenous somatostatin (SRIF)-14 or SRIF-28(1-14)-like immunoreactivity. Administration of the specific antisera to control birds pretreated with 0.9% NaCl elevated the basal plasma GH concentrations. These results suggest that peptides with SRIF-14 or SRIF-28(1-14)-like immunoreactivity tonically inhibit GH secretion and are at least partially responsible for the inhibitory effects of pargyline and quipazine on GH release in immature domestic fowl.     

Somatostatin immunoneutralization overcomes the inhibitory effects of quipazine and pargyline on growth hormone secretion in domestic fowl

Summary The inhibitory effects of pargyline and quipazine on chicken growth hormone secretion were overcome by passive immunoneutralization of endogenous somatostatin (SRIF)-14 or SRIF-28(1–14)-like immunoreactivity. Administration of the specific antisera to control birds pretreated with 0.9% NaCl elevated the basal plasma GH concentrations. These results suggest that peptides with SRIF-14 or SRIF-28(1–14)-like immunoreactivity tonically inhibit GH secretion and are at least partially responsible for the inhibitory effects of pargyline and quipazine on GH release in immature domestic fowl.