An approach to the identification of adenosine''s inhibitory site on adenylate cyclase

The separate and combined effects of molybdate and dithiothreitol on the stability of human uterine 9 S estrogen receptor were studied. Maximal, short-term, protection of the 9 S estrogen receptor was achieved by the joint inclusion of both stabilizing agents in cytosol buffers. This molybdate—dithiothreitol-mediated stability was dependent on reducing agent concentration inferring sulphydryl involvement in 9 S receptor protection by molybdate. The study also showed that molybdate—dithiothreitol could not prevent the gradual decay of the 9 S estrogen receptor to the 4 S form in cytosols stored at 4°C over prolonged periods.     

IS50-mediated inverse transposition. Discrimination between the two ends of an IS element

The crystal and molecular structure of l-pyroglutamyl-β-(2-thienyl)-l-alanyl-l-prolinamide, < Glu-Thi-Pro-NH₂(Thi²-TRH), C₁₇H₂₂N₄O₄S, has been determined from X-ray diffraction data. Thi²-TRH is a highly active analogue of thyroliberin, a thyrotropin-releasing hormone (TRH), in which the imidazole ring of the central histidine moiety in the natural hormone has been replaced by a 2-thienyl group. Thi²-TRH crystallizes from water in the monoclinic space group P2₁, $\text{a = 9.340(1)}\text{A}\text{?}\text{, b = 21.961(3)}\text{A}\text{?}\text{, c = 9.449(1)}\text{A}\text{?}$ and β = 109.58(1) °, with two molecules per asymmetric unit. These independent molecules, A and B, have the same general backbone conformation with the φ₂, ψ₂ and ψ₃ torsional angles close to ?90 °, +120 ° and +150 °, respectively, but they show different magnitudes of rotational disorder in the thiophene ring as well as a certain disorder in the pyrrolidine ring. A and B are cross-linked by four interchain hydrogen bonds, forming a two-stranded antiparallel β-pleated sheet structure. The molecules in these dimer fragments are further hydrogen-bonded to successive translated molecules along the a and c axes, forming a pronounced two-dimensional predominantly hydrophobic layer structure. These layers, in which the atoms are almost equally arranged on both sides, are separated by ordinary van der Waals' distances. A close correlation between the molecular conformation in the solid state and the preferential conformation in solution is found. It is concluded that the crystalline structure of Thi²-TRH possesses structural features which may be of relevance in the hormone-receptor interaction process.     

Evidence for sub-families of actin genes in Dictyostelium as determined by comparisons of 3' end sequences

We have sequenced the 3′ end of five actin genomic clones and three actin complementary DNA clones from Dictyostelium. Comparison of the sequences shows that the protein coding regions are highly conserved, while the region corresponding to the 3′ untranslated regions are divergent. Additional analysis indicates regions of homology in the 3′ untranslated region between sets of actin genes. Southern DNA blot hybridization studies using labeled 3′ ends suggest that there are sub-families of actin genes that are related within the 3′ untranslated regions. No homology is found in the sequences outside the messenger RNA encoding regions. Analysis of the sequence data has shown that the difference in length between the ~1.25 × 10³ and ~1.35 × 10³ base actin messenger RNAs is in the lengths of the 3′ untranslated region.     

Effect of glucose on protein phosphorylation in rat pancreatic islets

Isolated rat pancreatic islets, incubated in the presence of extracellular ³²Pi to steady state ³²P incorporation into cellular phosphopeptides, were exposed to glucose for 10 min. Glucose (16.7 mM) significantly stimulated the phosphorylation of six phosphoproteins with molecular weights of 15,000, 35,000, 49,000, 64,000, 93,000 and 138,000. Mannoheptulose (16.7 mM) markedly inhibited glucose-stimulated phosphorylation of these six phosphoproteins. This protein phosphorylation might be important in mediating glucose-stimulated insulin release.     

BCG-induced granulomatous pulmonary inflammation and splenomegaly in mice: A T-cell-dependent response

When C57BL/6 mice were injected iv with BCG in an oil-in-saline emulsion, they developed intense pulmonary granulomatous inflammation (PGI) and splenomegaly as well as chemotactic activity for macrophages and angiotensin-converting enzyme (ACE) in their lung fluids. PGI, splenomegaly, and levels of chemotactic activity and ACE were markedly reduced in T-cell-deficient “B” mice. The capacity to develop PGI was fully restored and splenomegaly was partially restored in “B” mice by the provision of syngeneic thymocytes, spleen cells, or purified T cells. These results indicate that the full expression of BCG-induced PGI is dependent upon thymus-derived cells and is associated with high levels of chemotactic activity for macrophages and ACE in the lung lavage fluid. Although BCG-induced splenomegaly appears to be T cell dependent, it did not reach its full magnitude in reconstituted “B” mice.     

Neonatal thyroxine treatment enhances classical conditioning in the infant rat

Neonatal rats injected with either thyroxine (T₄) or vehicle (NaOH) on postnatal Days 1, 2, and 3 were given classical-conditioning pairings of an odor with footshock when 7, 9, or 11 days of age. In accord with the conventional acceleration of other indices of maturation following the T₄ treatment, 24-hr retention of the conditioned odor aversion was substantially enhanced among the 11 day-old rats given the earlier T₄ treatment. This effect was marginally significant among 9-day olds but not among 7-day olds.