Free and polymerized tubulin in cultured bone cells and Chinese hamster ovary cells: the influence of cold and hormones

A low pH method of liposome-membrane fusion (Schneider et al., 1980, Proc. Natl. Acad. Sci. U. S. A. 77:442) was used to enrich the mitochondrial inner membrane lipid bilayer 30-700% with exogenous phospholipid and cholesterol. By varying the phospholipid-to- cholesterol ratio of the liposomes it was possible to incorporate specific amounts of cholesterol (up to 44 mol %) into the inner membrane bilayer in a controlled fashion. The membrane surface area increased proportionally to the increase in total membrane bilayer lipid. Inner membrane enriched with phospholipid only, or with phospholipid plus cholesterol up to 20 mol %, showed randomly distributed intramembrane particles (integral proteins) in the membrane plane, and the average distance between intramembrane particles increased proportionally to the amount of newly incorporated lipid. Membranes containing between 20 and 27 mol % cholesterol exhibited small clusters of intramembrane particles while cholesterol contents above 27 mol % resulted in larger aggregations of intramembrane particles. In phospholipid-enriched membranes with randomly dispersed intramembrane particles, electron transfer activities from NADH- and succinate-dehydrogenase to cytochrome c decreased proportionally to the increase in distance between the particles. In contrast, these electron- transfer activities increased with decreasing distances between intramembrane particles brought about by cholesterol incorporation. These results indicate that (a) catalytically interacting redox components in the mitochondrial inner membrane such as the dehydrogenase complexes, ubiquinone, and heme proteins are independent, laterally diffusible components; (b) the average distance between these redox components is effected by the available surface area of the membrane lipid bilayer; and (c) the distance over which redox components diffuse before collision and electron transfer mediates the rate of such transfer.     

Limited resistance of hypertrophied skeletal muscle to glucocorticoids

Male hypophysectomized rats were initially assigned to a control or an overloaded group that underwent compensatory hypertrophy of plantaris muscles to steady-state levels following removal of synergistic musculature. Plantaris muscle mass of overloaded animals was higher than that of controls by 38% (391 +/- 8 vs 284 +/- 7 mg) and glucocorticoid cytosol specific binding concentrations, using [3H]triamcinolone acetonide (TA) as the labeled steroid, was also significantly higher in hypertrophied muscles (83.3 +/- 3.9 fmol . mg protein-1) than in control muscles 56.3 +/- 3.9 fmol . mg protein-1). Cortisone acetate (CA) was then administered daily subcutaneously in high, 100 mg; intermediate, 10 mg; or low, 1.0 mg . kg-1 body wt doses. Groups of rats were killed after 1/4, 2 days and 7 days. Absolute muscle mass losses after 7 days of CA treatment were approx 80 mg with high doses and 60 mg with intermediate doses in both hypertrophied and control muscles. The low CA dose did not produce atrophy. The absolute depletion of [3H]TA binding activity with CA treatment was always greater in hypertrophied muscles of high and intermediate dose treated than those of their respective controls, but TA binding capacities remained higher in hypertrophied muscles than in controls at almost all time points in all treatment groups. Unlike previous findings in which the simultaneous initiation of overload prevented glucocorticoid induced muscle wasting, no resistance to the effect of CA treatment was observed when treatment was begun after hypertrophy had occurred.     

Movements and associations of ribosomal subunits in a secretory cell during growth inhibition by starvation

In Chironomus tentans salivary gland cells, the cytoplasm can be dissected into concentric zones situated at increasing distances from the nuclear envelope. After RNA labeling, the newly made ribosomal subunits are found in the cytoplasm mainly in the neighborhood of the nucleus with a gradient of increasing abundance towards the periphery of the cell. The gradient for the small subunit lasts for a few hours and disappears entirely after treatment with puromycin. The large subunit also forms a gradient but one which is only partially abolished by puromycin. The residual gradient which which is resistant to the addition of the drug is probably due to the binding of some large ribosomal units to the membranes of the endoplasmic reticulum (J.-E. Edstrom and u. Lonn. 1976. J. Cell Biol. 70:562-572, and U. Lonn and J.-E. Edstrom. 1976. J. Cell. Biol. 70:573-580). If growth is inhibited by starvation, only the puromycin-sensitive type gradient is observed for the large subunit, suggesting that the attachment of these newly made subunits to the endoplasmic reticulum membranes will not occur. If, on the other hand, the drug-resistant gradient is allowed to form in feeding animals, it is conserved during a subsequent starvation for longer periods than in control feeding animals. This observation provides a further support for an effect of starvation on the normal turnover of the large subunits associated with the endoplasmic reticulum. These results also indicate a considerable structural stability in the cytoplasm of these cells worth little or no gross redistribution of cytoplasmic structures over a period of at least 6 days.     

Time-course relationships between serum LH, serum progesterone and urinary preganediol concentrations in normal women

A specific and sensitive gas chromatographic method was used to investigate the concentration of pregnanediol glucuronide in urine in relation to the time of ovulation. Serum LH and progesterone concentrations in the same subjects were used as evidence for the occurrence of ovulation. The urinary concentration of pregnanediol glucuronide in 24-hour collections and in overnight specimens increased 2-fold or more from the day of the midcycle LH peak to the time of predicted ovulation (24-48 hour after the LH peak) in parallel with the rise in serum progesterone concentration.     

Effect of administered 20 beta-hydroxysteroid dehydrogenase on serum progesterone in the rat

Administration of 20 β-hydroxysteroid dehydrogenase from $\text{Streptomyces hydrogenans}$ to rats either intravenously or intraperitoneally results in decreases in serum progesterone.Detectable quantities of the enzyme were present in serum 2 days after intravenous injection. Intraperitoneal injections of 1.3 to 1.9 units of enzyme were effective in reducing serum progesterone over a longer period of time than the corresponding i.v. injections despite the failure of the enzyme to be absorbed into blood in detectable amounts; the serum concentration 2 hours after injection was 23% of that present before injection. The response was similar in diestrous and proestrous rats.     

Microbilobata,a new genus of earliest terebratulid brachiopod from the lower Silurian of Northwestern Canada: Implications for the origin of higher taxa

Microbilobata avalanchensis n. gen. and n. sp. from the Lower Silurian (upper Wenlock) carbonate rocks of the lower Delorme Group in the Avalanche Lake area, northwestern Canada, is described here as the earliest known terebratulid brachiopod. These small shells (less than 2 mm long) are subtriangular, anteriorly emarginate, possibly punctate, with both valves being sulcate at their anterior halves, the ventral sulcus bearing one prominent plica, and the dorsal sulcus marked by two plicae. Internally, M. avalanchensis has a centronelliform loop extending for about three fifths of the total shell length. The shells are silicified in carbonate rocks of mid to outer shelf origin. M. avalanchensis is relatively rare, with about 40 specimens so far found from samples collected at 58–60 m above the base of section AV5 in the Avalanche Lake area. Its presence in rocks of Wenlock age extends the earliest known terebratulids back about 16 million years from the oldest previously recorded terebratulids (earliest Devonian age). The small size and simple form of the new species suggest that heterochrony (progenesis) could have played a role in the origin of the Terebratulida. M. avalanchensis serves as a good example of Cope's Rule, indicating that the terebratulids evolved from a very small, unspecialized ancestor. The unusually small size of this taxon also offers one explanation as to why some ancestors or transitional forms of major taxonomic groups are extremely difficult to find in the fossil record.     

Examination of Duct Physiology in the Human Mammary Gland

BackgroundThe human breast comprise several ductal systems, or lobes, which contain a small amount of fluid containing cells, hormones, proteins and metabolites. The complex physiology of these ducts is likely a contributing factor to the development of breast cancer, especially given that the vast majority of breast cancers begin in a single lobular unit.MethodsWe examined the levels of total protein, progesterone, estradiol, estrone sulfate, dehydroepiandrosterone sulfate, and macrophages in ductal fluid samples obtained from 3 ducts each in 78 women, sampled twice over a 6 month period. Samples were processed for both cytological and molecular analysis. Intraclass correlation coefficients and mixed models were utilized to identify significant data.ResultsWe found that the levels of these ductal fluid components were generally uncorrelated among ducts within a single breast and over time, suggesting that each lobe within the breast has a distinct physiology. However, we also found that estradiol was more correlated in women who were nulliparous or produced nipple aspirate fluid.ConclusionsOur results provide evidence that the microenvironment of any given lobular unit is unique to that individual unit, findings that may provide clues about the initiation and development of ductal carcinomas.