Cyclin synthesis, modification and destruction during meiotic maturation of the starfish oocyte

The pattern of protein synthesis in oocytes of starfish Marthasterias glacialis changes during 1-methyladenine-induced meiotic maturation. One of the newly synthesized proteins, a major 54-kDa polypeptide, was synthesized continuously after activation but was destroyed abruptly just before appearance of the polar bodies at each meiotic division. This protein thus resembles the cyclin proteins identified in cleaving sea urchin and clam embryos. RNA extracted from oocytes before and after maturation encoded virtually identical polypeptides when translated in the reticulocyte lysate. However, there was poor correspondence between the in vitro translation products and the labelling pattern of intact cells. There was no exact in vitro counterpart to the in vivo-labelled cyclin. Instead, a major polypeptide of 52 kDa was seen which appears to be a precursor of the 54-kDa form of cyclin. The 52-kDa polypeptide was identified as cyclin by hybrid arrest of translation. Cyclin mRNA is ot translated to a significant extent before oocyte activation and is present in oocytes as nonadenylated form. It becomes polyadenylated when the oocytes mature. This behavior is also seen in the case of the mRNA for the small subunit of ribonucleotide reductase, another abundant maternal mRNA whose translation is activated at maturation.     

Purification of an acid protease from Mucor rouxii that inactivates chitin synthetase

An acid protease was purified from the mycelial form of Mucor rouxii by a method which involved salt and acid precipitation, gel filtration and anion-exchange chromatography. The enzyme had a molecular mass of 16,000 Da. Its optimum pH was 4.0, maximal activity was obtained at 50°C, and it was inactivated at 70°C. It was not affected by leupeptin or N -p-tosyl-L-lysine chloromethyl ketone (TLCK) but diazoacetyl-DL-norleucine methyl ester (DNME) in the presence of Cu²⁺ and more noticeably pepstatin A, strongly inhibited the activity. This acid protease did not activate zymogenic chitin synthetase from the fungus, but brought about its inactivation even at low concentrations and after short periods of incubation time.Abbreviations TLCK N -p-tosyl-L-lysine chloromethyl ketone - DNME diazoacetyl-DL-norleucine methyl ester - TCA trichloroacetic acid - SDS sodium dodecyl sulfate     

The effect of cold storage at 4 °C on the Rooting of chestnut cuttings

This article reports the effect of cold storage at 4 °C from December to April on chestnut cuttings. Rooting was found to increase after four months preceded by treatment with 4000 mg l^-1 IBA. ThePhaseolus test of the biological activity of extracts of the cuttings showed the inhibition exerted by the acid fraction of the fresh (December) cuttings to have been replaced by a rootpromoting effect in cuttings stored for 4 months at low temperature. Cold storage thus seems to favour rooting.     

The 18p- syndrome. Report of five cases

Five children, three males and two females were found to have a short arm deletion of chromosome 18. Four of them display some of the typical features of this syndrome: microcephaly, round face, hypertelorism, broad-based nose, "carp-mouth", microrethrognathia, pterygium colli, dysplastic and low set ears, clinodactily, failure to grow, muscular hypotony and mental retardation. Different hypotheses are discussed in order to explain the variable phenotypical expression of the 18 p-syndrome.     

Evidence from 18O exchange measurements for steps involving a weak acid and a slow chemical transformation in the mechanism of phosphorylation of the gastric H+, K+-ATPase by inorganic phosphate

Phosphorylation of the gastric H,K-ATPase by Pi has been studied by measuring the P18Oj16O4-j distribution as a function of time at different H+, K+, and [18O]Pi concentrations. The advantage of isotope exchange measurements is that the P18Oj16O4-j distribution depends on the relative rates of HOH loss to form the phosphoenzyme intermediate and Pi dissociation from the enzyme. Therefore, 18O exchange is a sensitive probe of mechanism. K+ increases the exchange rate (v(ex] but does not affect the partition coefficient (Pc) that determines the P18Oj16O4-j distribution. Conversely, H+ inhibits exchange. A single Pc describes the data at every pH, but the value increases from 0.04 at pH 8 to 0.64 at pH 5.5. Vex depends hyperbolically on [Pi]0. Km for Pi does not depend on pH, and Pc does not depend on [Pi]0. Individual rate constants in the phosphorylation mechanism are estimated. Formation of the E.Pi complex that looses HOH is 1-2 orders of magnitude slower at pH 5.5 than at pH 8 and is not diffusion controlled. The observed change in Pc with pH is compatible with catalysis occurring by a different mechanism when a group with pKa = 7.2 is protonated. Slower than diffusion-controlled formation of the E.Pi complex that splits out HOH is evidence for a relatively slow, unimolecular chemical transformation involving an additional intermediate in the phosphorylation mechanism, such as a protein conformational change.     

Uranium-series ages of marine terraces,La Paz Peninsula,Baja California Sur,Mexico

Uranium-series dating of coral samples from raised marine terrace deposits between 1.5 and 10 m above sea level in the La Paz Peninsula area, Baja California Sur, yielded ages between 123 ka and 138 ka that are in agreement with previously reported results. The stratigraphy and ages of marine units near the El Coyote Arroyo indicate the presence of two high stands of the sea during the last interglacial or oxygen isotope substage 5e at about 140 ka and 123 ka. Accepting 5 m for the sea level during the last interglacial transgression, we calculate average uplift rates for the marine terraces of about 70 mm/ka and 40 mm/ka. These slow rates of uplift indicate a relative stability of the La Paz peninsula area for the past 140 000 years. In contrast, areas of Baja California affected by major faultf experienced higher rates of uplift. Rockwell et al. (1987) reported vertical uplift rates of 180 to 300 mm/ka at Punta Banda within the Aqua Blanea fault zone in northern Baja California.