RELATIVE CONTRIBUTIONS OF EXTRACELLULAR Ca2+ AND Ca2+ STORES TO SMOOTH MUSCLE CONTRACTION IN ARTERIES AND ARTERIOLES OF RAT, GUINEA-PIG DOG AND RABBIT

1. These studies describe the functional effects of modulation of the sarcoplasmic reticulum (SR) Ca²⁺ stores at three levels of the vasculature: (i) large arteries (rat and guinea-pig aorta); (ii) small resistance arteries (rat tail artery, rabbit mesenteric artery, dog mesenteric artery); and (iii) arterioles (guinea-pig submucosal arterioles of the small intestine). 2. All tissues responded to phenylephrine (PE; 10 μmol/L) with a transient contraction in Ca²⁺-free Krebs', reflecting Ca²⁺ release from PE-sensitive Ca²⁺ stores. After pretreatment with cyclopiazonic acid (CPA; 30 μmol/L) or thapsigargin (TSG; 1 μmol/L), putative SR Ca²⁺ pump inhibitors, the PE-induced contraction in a Ca²⁺-free medium was significantly inhibited in arterial tissues at all levels of the vasculature. Similarly, ryanodine (RYA; 30 μmol/L), an agonist that enhances Ca²⁺ release from the SR, also reduced the PE contraction in a Ca²⁺-free solution. 3. CPA or TSG alone in the presence of extracellular Ca²⁺, caused marked and sustained contraction in the rat and guinea-pig aorta and marked but transient or no contraction in the resistance arteries. In the rat and guinea-pig aorta, RYA caused a slowly developing tension. Little increase in basal tension was produced by RYA in resistance arteries and arterioles. 4. The findings show that an agonist-releasable Ca²⁺ pool is present at all levels of the vasculature that is independent of the size of the vessels and suggest that under normal physiological conditions there is an intimate balance between the roles of the plasma membrane and of the SR in the maintenance of vascular contractility. It appears that the role of the SR diminishes as the arteries become smaller, while Ca²⁺ fluxes across the plasma membrane predominates.     

Cumulative pregnancy rates and selective drop-out of patients in in- vitro fertilization treatment

The validity of the cumulative pregnancy rate (CPR) calculated by life- table approach, obtained in a transport in-vitro fertilization (IVF) programme, was tested by the determination of possible influence of selective drop-out of patients with a poor treatment prognosis. A cohort of 1211 patients who had a first IVF cycle was followed, and the CPR after three IVF cycles was assessed. First cycles of patients who discontinued treatment after failed IVF, and of those who did not achieve a pregnancy but proceeded to a subsequent cycle, were compared for fertilization rate and for occurrence of prognosticators of poor treatment outcome: oocyte yield < or =2, and replacement of <2 embryos. The CPR after three cycles was 54.9%. No differences were found in the first and second cycles of patients who continued treatment and those who dropped out. Selective drop-out of patients with a poor treatment prognosis was not found. Therefore, although calculations of CPR using life-table analysis generally overestimate the real probability of pregnancy after successive IVF cycles, the calculated CPR after three IVF cycles gives a reliable indication of the chance of occurrence of a pregnancy for the population studied.      

2,4-Disubstituted thiazoles II. A novel class of antitumor agents, synthesis and biological evaluation

A series of 2,4-disubstituted thiazole derivatives bearing N-n-butyl or N-cyclohexylthioureido synthon at position 2 and N-substituted thiosemicarbazone moiety at position 4 have been synthesized and tested for antitumor activity using the National Cancer Institute's in-vitro-disease-oriented antitumor screen. All of the tested compounds showed antineoplastic activity at concentrations less than 100 μM. Compounds 7, 9, 15 and 17 in particular showed activity with GI₅₀ (mean-graph midpoint) of 17.8, 8.5, 9.5 and 7.4 μM, respectively. The detailed syntheses, spectroscopic and biological data are discussed.