Sulphur isotope evidence for an oxic Archaean atmosphere

The presence of mass-independently fractionated sulphur isotopes (MIF-S) in many sedimentary rocks older than approximately 2.4 billion years (Gyr), and the absence of MIF-S in younger rocks, has been considered the best evidence for a dramatic change from an anoxic to oxic atmosphere around 2.4 Gyr ago. This is because the only mechanism known to produce MIF-S has been ultraviolet photolysis of volcanic sulphur dioxide gas in an oxygen-poor atmosphere. Here we report the absence of MIF-S throughout approximately 100-m sections of 2.76-Gyr-old lake sediments and 2.92-Gyr-old marine shales in the Pilbara Craton, Western Australia. We propose three possible interpretations of the MIF-S geologic record: (1) the level of atmospheric oxygen fluctuated greatly during the Archaean era; (2) the atmosphere has remained oxic since approximately 3.8 Gyr ago, and MIF-S in sedimentary rocks represents times and regions of violent volcanic eruptions that ejected large volumes of sulphur dioxide into the stratosphere; or (3) MIF-S in rocks was mostly created by non-photochemical reactions during sediment diagenesis, and thus is not linked to atmospheric chemistry.     

Diurnal variations in serum and liver zinc levels throughout the 4-day estrous cycle of the hamster

Summary Diurnal variations of serum zinc level and liver zinc level of the golden hamster were found throughout the 4-day estrous cycle, and on the different days of the cycle, the patterns of fluctuation differed.     

Specific inhibition of a calcium dependent activation of brain cyclic AMP phosphodiesterase activity by vinblastine

Summary Vinblastine selectively inhibits the activation of brain cyclic AMP phosphodiesterase activity by Ca⁺⁺-protein activator (50% inhibition by 2×10^–5 M). This inhibitory effect was reversed by excessive amounts of the activator, whereas large quantities of Ca⁺⁺ caused only a slight suppression of the vinblastine effect. This result of vinblastine suggests a new site of its action and also suggests the possible role of protein activator, phosphodiesterase proteins or cyclic nucleotides in the previously known effects of vinblastine in vivo and in vitro.Our thanks to Drs A. R. Rhoads, C. B. Klee and R. A. Fergusson for analyzing PA preparations by gel electrophoresis and gel electrofocusing, and to Drs A. A. Suran and D. Soifer for their valuable critiques to this work. This work was partly supported by Biochemical Research Support Grant No. 5SO7RRO5361 to K.W. and Graduate Training Grant No. 5TO2GMO500002 to W.L.W. from NIH.     

Immunohistochemical evidence that tumors elicit the synthesis of estrogen receptors in the submandibular gland of female rats

We have demonstrated the presence of estrogen receptor mRNA and the mature protein in the cytoplasm and nucleus, respectively, of a 9,10-dimethyl-1,2-benzathracene-induced submandibular gland tumor in female rats. We have previously shown that progesterone receptors are also present in human salivary gland tumors. These results suggest that endocrine therapy may be effective in treatment of submandibular gland tumors.     

Pharmacological studies on thiamine deficiency IV. Blood catecholamine content and blood pressure of thiamine deficient rats

Zusammenfassung Wegen der Senkung des Blut-Katecholamin-Spiegels in unter experimentell erzeugtem Thiaminmangel stehenden Ratten kommt es zu einer Hypotonie. Die Abschwächung der spontanen Freisetzung des Katecholamins aus dem katecholaminspeichernden Gewebe bei Thiaminmangelratten ist als ein Faktor bei der Aminakkumulation bei Thiaminmangel zu denken.     

Control of germ cell nuclear behaviour at fertilization by Tetrahymena intermediate filament protein

Intermediate filament protein [relative molecular mass (Mr) 49,000 (49K)] from the ciliated protozoan Tetrahymena has been shown to resemble intermediate filament proteins from mammalian cells in several respects, and to have a possible role in the oral morphogenesis preceding binary fission in Tetrahymena. Here, based on immunofluorescence localization of the 49K protein in Tetrahymena during the early stages of conjugation, we suggest that the protein is involved in some nuclear events, such as the production of four haploid nuclei by prezygotic divisions (meiosis), selection of one of the four meiotic products, formation of the gametic pronucleus by the mitotic division of the selected meiotic product, transfer of the gametic pronucleus across a cell-cell junction, and zygote formation by pronuclear fusion.     

Induction of IgG1 and IgE responses to protein-conjugated and unconjugated β-lactam antibiotics in the mouse-efficacy of Freund's complete adjuvant

Summary One or two injections two weeks apart of protein-conjugated penicillin G, cephalothin or cefmetazole emulsified with Freund's complete adjuvant were quite effective in producing anti-antibiotic antibodies of the IgE as well as of the IgG₁ class in mice. Long-lasting and boostable production of both antibody classes was also obtained against unconjugated cephalothin or cefmetazole, though the positivity depended on the mouse strain.