Regression of mouse mammary gland anlagen in recombinants of Tfm and wild-type tissues: testosterone acts via the mesenchyme

In the male mouse, regression of the mammary gland anlagen is induced by testosterone during embryonic life. In the androgen-insensitive Tfm mouse, the gland anlagen are resistant to the testosterone action. To analyze cellular interactions in this process, we isolated the mammary gland anlagen from Tfm- and wild-type embryos. The epithelial buds were separated from the mesenchyme by trypsin-pancreatin treatment. From the epithelial and mesenchymal components, reciprocal recombinations were prepared and cultivated on millipore filter in the presence of testosterone. In combination with androgen-insensitive Tfm- mesenchyme, the wild-type buds survived the action of testosterone. On the other hand, in combination with wild-type mesenchyme, the androgen-insensitive Tfm epithelial buds were destroyed. The results show that testosterone induces detachment and degeneration of the buds via the mesenchyme.     

Production of specific antibodies to contractile proteins,and their use in immunofluorescence microscopy

Summary The injection of rabbits with insoluble or soluble G-actin from chicken smooth or striated muscle will produce antibodies that are equally reactive, and species and tissue non-specific in immunoprecipitation, immunofluorescence and actin-activated Mg²⁺-ATPase^** inhibition test. These antibodies have been used for the identification of actin-containing fibrils in a variety of tissues. When G-actins from chicken smooth or striated muscle are immobilized by chemical linkage to Affi-Gel 702 microbeads, their immunogenicity is increased, but the antibodies obtained against them are species-specific and will only react with actin and actin-containing structures from chicken and are therefore limited in use. It is concluded from this work that insoluble G-actin is the preferable immunogen to obtain precipitating antibodies for wide use.Abbreviations ATPase Adenosinetriphosphatase - FITC Fluoresceinisothiocyanate - SDS Sodiumdodecylsulfate This paper is dedicated to Dr. Dorothy M. Needham, University of Cambridge, England, in honour of her eightieth birthday     

Generation of phosphatidic acid and diacylglycerols following ligation of surface immunoglobulin in human B lymphocytes: potential role in PKC activation.

We have examined signal transduction via membrane IgM (mIgM) in resting and cycling human B cells. Crosslinking mIgM on all of the cell types studied transduced a signal through the phosphatidylinositol pathway, producing inositol 1,4,5-trisphosphate and release of intracellular free calcium. These second messengers were formed regardless of quantitative or qualitative differences in the surface expression of mIgM: cells that had low levels of surface IgM (T-51) or had no light chain associated with surface heavy chain (DB) signaled phosphatidylinositol pathway activation after mIgM crosslinking. Production of specific lipid products in nonquiescent B cells differed from that in normal resting cells. Ligation of surface immunoglobulin on resting B cells resulted in sustained increases of both diacylglycerol and phosphatidic acid, two lipids that can influence PKC activation. Whereas PKC was strongly activated in normal tonsillar B cells, several cell lines had reduced PKC activation following crosslinking of mIgM. The reduction in protein kinase C activation correlated with the absence or reduced levels of phosphatidic acid or diacylglycerol following stimulation: protein kinase C translocated and was activated only in cells that had elevated levels of both diacylglycerides and phosphatidic acid. Anti-IgM-induced phosphorylation of a protein kinase C substrate protein CD20, also increased in those cells having PKC activation and not in cells in which kinase activity was reduced. CD20 phosphorylation also increased following the direct addition of exogenous phosphatidic acid to resting B cells. Together, these observations show that the generation of lipid products following mIgM crosslinking in resting cells can vary from that in cycling cells and may relate to the different levels of PKC activation. In a companion study we report that ligation of surface IgM activates both an acyltransferase and phospholipase D to form phosphatidic acid.     

Inhibitory effects of mersalyl and of antibodies directed against smooth-muscle myosin on a calcium adenosine triphosphatase of the plasma membrane from mouse liver cells.

The effect of mersalyl and of antibodies, directed against smooth-muscle myosin and skeletal muscle myosin, on the (Ca²⁺ + Mg²⁺)-activated adenosine triphosphatase (Ca,Mg)ATPase) system of mouse liver plasma membranes has been studied. Antismooth-muscle myosin inhibited by 38.6% at optimum substrate concentration the (Ca,Mg)ATPase with a K_m of 0.88 × 10^?3m. Mersalyl (0.5 mm) also inhibited this enzyme, the percentage inhibition being 44.6% at optimal substrate concentration. These results suggest the presence of a smooth-muscle myosin-like protein in the plasma membrane of mouse liver cells which has an associated (Ca,Mg)ATPase activity.     

A twofold role for global energy gradients in marine biodiversity trends

Explanations for major biodiversity patterns have not achieved a consensus, even for the latitudinal diversity gradient (LDG), but most relate to patterns of solar energy influx into Earth systems, and its effects on temperature (as biochemical activity rates are temperature sensitive) and photosynthesis (which drives nearly all of the productivity that fuels ecosystems). Marine systems break some of the confounding correlations among temperature, latitude and biodiversity that typify the terrestrial systems that have dominated theoretical discussions and large‐scale analyses. High marine diversities occur not only in warm shallow seas where productivity may be either low or high, depending on regional features, but also in very cold deep‐sea regions, indicating that diversity is promoted by stability in temperature and in trophic resources (nutrients and food items), and more specifically by their interaction, rather than by high mean values of either variable. The common association of high diversity with stable but low to moderate annual productivity suggests that ecological specialization underlies the similarly high diversities in the shallow tropics and deep sea. Recent work on shallow‐marine bivalves is consistent with this view of decreasing specialization in less stable habitats. Lower diversities in shallow seas are associated with either high thermal seasonality (chiefly in temperate latitudes) or highly seasonal trophic supplies (at any latitude), which exclude species that are adapted to narrow ranges of those variables.     

Concomitant Pavlovian conditioning of heart rate and leg flexion responses in the rat

Pavlovian conditioning was studied in male Fischer 344 rats using tones as the conditioned stimulus (CS) and footshock as the unconditioned stimulus (UCS). Different groups of animals received (a) contiguous CS-UCS pairings with a 0.5 sec CS, (b) contiguous CS-UCS pairings with a 4.0 sec CS, or (c) a random sequence of noncontiguous tones and shocks using either a 0.5 sec or a 4.0 sec CS. Heart rate (HR) and leg flexion (LF) responses were recorded. Leg flexion conditioning occurred only in the 0.5 sec contiguous group. Decelerative HR CRs occurred only in the 4.0 sec contiguous group. Accelerative HR changes occurred in the other two groups but were significantly greater in the 0.5 sec contiguous group. These results are similar to but not identical to those obtained during eyeblink or nictitating membrane conditioning in rabbits, and suggest that the topography of the Pavlovian HR CR is dependent on the simultaneous occurrence of other classically conditioned responses.