Effects of forskolin on adenylate cyclase,cyclic AMP,protein kinase and intermediary metabolism of the thyroid gland

Forskolin (40 μM) stimulated adenylate cyclase activities of bovine thyroid plasma membranes without pthe addition of guanine nucleotides. GDP had little effect on the forskolin-stimulated adenylate cyclase activity while Gpp[NH]p (0.1–1.0 μM) decreased it. In the presence of TSH (10 mU/0.11), Gpp[NH]p no longer caused inhibition. Forskolin did not affect phosphodiesterase activities of thyroid homogenates. Forskolin (10 μM) rapidly increased cAMP levels in bovine thyroid slices both in the absence and presence of a phosphodiesterase inhibitor. The effect of TSH (50 mU/ml) on cAMP levels was additive or greater than additive to that of forskolin. An initial 2-h incubation of slices with forskolin did not decrease their subsequent cAMP responses to either forskolin and/or TSH while similar treatment of slices with TSH induced desensitization of the cAMP response to TSH, but not to forskolin. Forskolin (10 μM) as well as TSH (50 mU/ml) activated cAMP-dependent protein kinase of slices in the absence of a phosphodiesterase inhibitor. Although forskolin activated the adenylate cyclase cAMP system, it did not stimulate iodide organification or glucose oxidation, effects which have been attributed to cAMP. In fact, forskolin inhibited these parameters and ³²P incorporation into phospholipids as well as their stimulation by TSH. These results indicate that an increase in cAMP levels and cAMP-dependent protein kinase activity in thyroid slices may not necessarily reproduce the effects of TSH on the thyroid.     

Purification of endo-(1→3)-β-D-glucanases lysing yeast cell walls from Rhizoctonia solani

Three forms of $\text{endo}\text{-(1→3)-β-}\text{g}\text{-glucanases}$ lysing yeast cell walls from Rhizoctonia solani were separated by precipitation with ammonium sulfate and by successive chromatographies on CM Bio-Gel A and Bio-Gel P-60 or P-30, and were finally purified by substrate affinity chromatography on short-chain pachyman-AH-Sepharose CL 6B column. Each preparation was found to be homogeneous on gel filtration and by electrophoresis on acrylamide gel with sodium dodecyl sulfate. They exhibit high activity against insoluble pachyman, but only restricted activity against soluble short-chain pachyman. In the affinity chromatography, three enzymes were found to be strongly absorbed on the column, so that they could be easily eluted with substrate solution using biospecific counter-ligand. It was thus revealed that covalent binding of such a soluble glucan to aminohexyl-Sepharose provides a useful carrier for separation of $\text{endo}\text{-(1→3)-β-}\text{D}\text{-glucanases}$ lysing yeast cell walls.     

Application of MEN 203 as a polymorphic DNA probe in screening multiple endocrine neoplasia 2a.

Multiple endocrine neoplasia 2a (MEN 2a) is known to be genetically linked to a locus on chromosome 10. The application of polymorphic DNA probes for the region has made it possible to identify carriers of the disease susceptible gene. We performed DNA analysis for a newly found non-Caucasian MEN 2a family using MEN 203 as a probe. Data from DNA analysis of the family members were concordant with the results of conventional endocrinological tests. Furthermore, DNA analysis discriminated four individuals out of fifteen as non-carriers of the gene with a high degree of certainty. The results relieved these people from taking screening tests for years. DNA analysis employing suitable markers such as MEN 203 appears to be useful for a screening program of MEN 2a in Japanese as well as Caucasians.     

Expression of high activity of ornithine decarboxylase and occurrence of unusual chromophobic cells in anterior pituitary gland of a novel growth-retarded strain of mice, grm/grm

Extremely high activity of ornithine decarboxylase (ODC) was detected in the pituitary gland of growth- retarded mice, grm/grm at 2 months after birth. The elevated enzyme activity gradually decreased to the control level in 14 months after birth. In the pituitary gland of the growth-retarded mice, unusual chromophobic cells were also present from the early stages after birth. The chromophobic cells showed conspicuous proliferations and resulted in a distinct hyperplasia of the tissue after 4 months after birth. These findings suggest that OCD is correlated to the progressive transformation of pituitary cells into the chromophobic cells.