Analysis of cellular interactions in density-dependent inhibition of 3T3 Cell proliferation

Subpopulations of different proliferative status are determined during cell-density dependent proliferation of 3T3 cells. From these data the probability of conversion of proliferative to quiescent cells is derived and found to correlate well with published data on binding of growth-inhibiting factors secreted from growth-inhibited cells.Based on material presented at the Symposium Intercellular Communication Stuttgart, September 16–17, 1982     

Anti-tumor effects of an antiserum raised in syngeneic mice to a tumor-specific T suppressor factor

Summary DBA/2 mice inoculated with either cells from the syngeneic P815 tumor or tumor cell membrane extracts develop T suppressor cells which suppress the in vitro generation of cytotoxic T lymphocytes with specificity for the tumor. A soluble suppressor factor with similar properties can be isolated from suppressor cell-enriched populations. It can be highly purified by appropriate immunoadsorption. Antisera to this suppressor factor raised in either DBA/2 or C57BL/6 mice can specifically absorb out suppressor factor and eliminate suppressor cells in the presence of complement. The in vivo effects of these antisera were tested for their ability to modulate the growth of P815 tumors in DBA/2 mice. It was found that the antiserum raised in syngeneic (DBA/2) but not allogeneic (C57BL/6) mice was able to significantly slow the rate of tumor growth and to prolong survival in treated mice. The antiserum was effective in this way only if it was administered early in the course of tumor growth. It was shown that this effect was not attributable to the presence in the serum of antibodies directed to antigens present on P815 cells, and it therefore appears to be due to interference with the function of T suppressor cells arising early in the immune response to the tumor cells.     

Development of a Defined Medium for Growth of Cercospora rosicola Passerini

A simple synthetic liquid medium containing a single amino acid, glucose, salts, trace metals, and thiamine was developed for cultivation of Cercospora rosicola Passerini. Thiamine was shown to be important to growth. Culture of C. rosicola Passerini in a chemically defined medium makes possible studies of (+)-abscisic acid biosynthesis and regulation.     

Incorporation of L-[U-14C]leucine into ergosine by cell-free extracts of Clavicepspurpurea (FR.) tul

A cell-free system of $\text{Claviceps}\text{purpurea}$ has been described which incorporates [¹⁴C] leucine into the peptide-type ergot alkaloid ergosine. Cell-free extracts may be prepared either from protoplasts or lyophilized mycelium. Production was markedly stimulated by addition of agroclavine compared with d-lysergic acid and by agitation of the incubation mixture. The synthesis of ergosine is strongly dependent on the presence of ATP in the reaction mixture.     

Primary structure of yeast proteinase B inhibitor 2.

The complete amino acid sequence of yeast proteinase B inhibitor 2 (IB2) was determined to be H3N+-Thr-Lys-Asn-Phe-Ile-Val-Thr-Leu-Lys-Lys-Asn-Thr-Pro-Asp-Val-Glu-Ala-Lys-Lys-Phe-Leu-Asp-Ser-Val-His-His-Ala-Gly-Gly-Ser-Ile-Leu-His-Glu-Phe-Asp-Ile-Ile-Lys-Gly-Tyr-Thr-Ile-Lys-Val-Pro-Asp-Val-Leu-His-Leu-Asn-Lys-Leu-Lys-Glu-Lys-His-Asn-Asp-Val-Ile-Glu-Asn-Val-Glu-Asp-Lys-Glu-Val-His-Thr-Asn-COO-. Elucidation of the primary structure was enabled by automated Edman degradation and COOH-terminal hydrolysis with carboxypeptidases A (bovine pancreas and Y (yeast). IB2 is the first proteinase inhibitor to be sequenced that possesses a structure devoid of disulfide bridges.     

D-Trp8-D-Cys14-somatostatin--demonstration of its differential suppressive activity in juvenile diabetics.

In 8 insulin-dependent diabetics, the effect of D-Trp8-D-Cys14-somatostatin on blood glucose, growth hormone, and glucagon levels as well as on insulin requirements from an artificial endocrine pancreas was studied during a balanced meal. The somatostatin analogue was infused at a rate of 25 microgram/h preceeded by a bolus injection of 25 microgram 30 minutes before ingestion of the meal. At this dose the analogue had no effect on glucagon levels and insulin requirements from the artificial pancreas. On the other hand, there was a significant lowering effect on fasting blood glucose levels, possibly indicating a direct inhibition of hepatic glucose production. Furthermore, there might be a slight effect on growth hormone levels, as was demonstrated by a rebound increase after termination of analogue infusion.     

The effect of three days of blood glucose normalization by means of an "artificial endocrine pancreas" on the concentrations of growth hormone, glucagon, and cortisol in juvenile diabetics.

Glucagon, growth hormone, and cortisol secretion was studied in seven male insulin-dependent diabetics under conventional subcutaneous insulin therapy and after three days of blood glucose normalization attained by the artificial endocrine pancreas (Biostator-GCIIS). The diurnal hormonal profiles under the two types of therapy were compared. Six healthy male students served as control group. A three-day period of blood glucose normalization in insulin-dependent diabetic can restore glucagon secretion to normal. Growth hormone secretion is decreased but not completely normalised. Cortisol secretion is slightly decreased. It is concluded that prolonged normoglycemia achieved by means of an artificial endocrine pancreas may completely control endocrine abnormalities in insulin-dependent diabetics.     

Cyclic 3',5'-adenosine monophosphate in the choroid plexus: stimulation by cholera toxin.

Cholera toxin was found to induce high accumulations of cyclic AMP in the isolated choroid plexus of the rabbit and in the incubation medium. The accumulation showed a characteristic lag phase of at least 30 min and continued for at least 3 hours. Inactivated cholera toxin was unable to increase cyclic AMP levels. There was only a moderate effect of cholera toxin on cyclic AMP “low K_m” phosphodiesterase activity in homogenates. The effect of cholera toxin on cyclic AMP levels confirms the existance of a potent cyclic AMP generating system in the choroid plexus which is activated also by β-adrenergic agonists, histamine and prostaglandin E₁.