The complete primary structure of mouse 20S proteasomes

 The proteasome is a large multicatalytic proteinase that plays a role in the generation of peptides for presentation by major histocompatibility complex class I molecules. The 20S proteolytic core of mammalian proteasomes is assembled from a group of 17 protein subunits that generate a distinctive pattern of spots upon two-dimensional gel electrophoresis. The genes for most of these subunits have been cloned from humans and rats. We isolated cDNA clones for the mouse orthologues of ten of the subunits [PSMA1 (C2), PSMA2 (C3), PSMA3 (C8), PSMA4 (C9), PSMA5 (ZETA), PSMA6 (IOTA), PSMA7 (C6-I), PSMB2 (C7-I), PSMB3 (C10-II), and PSMB5 (X)] to complete the cloning of all of the mouse subunits. Using antisera raised against these subunits or their orthologues, we verified the identity of these proteins by two-dimensional NEPHGE-PAGE. Received: 8 March 1999 / Accepted: 8 April 1999     

Estrogen-bridged purines: A new series of anti-tumor agents which alter cell membrane properties

An estrogen-bridged adenine derivative was equitoxic to both the P388 murine leukemia and an adriamycin-resistant subline, $\text{P388}\text{ADR}$. The drug rapidly altered several P388 and $\text{P388}\text{ADR}$ membrane properties resulting in impaired nucleoside transport and increased membrane hydrophobicity. Resistance to anthracyclines in $\text{P388}\text{ADR}$ is associated with an operational barrier to drug retention which was reversed by exposure to the estrogen-bridged adenine derivative. These results suggest further exploration of the estrogen-bridged purines as chemotherapeutic agents.     

Suppression of steroidogenesis in mice granulosa cells by a synthetic nonapeptide fragment of human seminal plasma inhibin.

A synthetic nonapeptide, which is C-terminal sequence of 94-amino acid of prostatic inhibin peptide was tested for progesterone and estrogen secretion by mouse granulosa cell cultures. Nonapeptide suppressed the progesterone and estrogen synthesis, the magnitude of suppression was highest at 5 ng dose level for progesterone and 50 ng dose level for estradiol. The study suggests that, nonapeptide exerts its effect by impairing the binding of FSH to granulosa cell receptors.     

Terminal mycelial clusters of tree roots; Their nutritional importance

Summary This study was concerned with properties of mycelia-agglutinated terminal root clusters, or mycoplasts,' of naturally reproduced seedlings ofPinus resinosa andPinus strobus. These rhizospheric root appendages, formed at the expense of the host plant's carbohydrates, exhibited high catalytic potential, cation exchange capacity, and content of exchangeable bases, including complexible cations. These attributes suggest that mycelial clusters are important components of tree-fungus symbiotic mechanism that increase availability of nutrients to the trees. The mycelial clusters apparently perform the function of mycorrhizal short roots which are often nonexistent under the conditions of reduced radiation in well-stocked forest stands.Research supported by the College of Agriculture and Life Sciences, University of Wisconsin, Madison, and the Wisconsin Department of Natural Resources.     

Reduced water intake: Implications for rodent developmental and reproductive toxicity studies

In developmental and reproductive toxicity studies, drinking water is a common means of delivering the test agent. Reduced consumption of toxicant-containing water raises questions about indirect effects of reduced maternal fluid consumption resulting from unpalatability, versus direct effects of the test compound. Issues to consider include: objective assessment of dehydration and thirst, the relative contributions of innate and learned behaviors to drinking behavior and flavor preference, and the objective assessment of physiologic stress. Not only do lab animals under ad lib conditions consume more water than the minimum required to maintain fluid balance, animals faced with water restriction have substantial physiologic capacity for protection of metabolic processes. Measures of blood biochemistry can provide quantifiable, objective indications of fluid balance, but changes in these parameters could result from other causes such as effects of a test toxicant. Consummatory behaviors in response to perceived need are highly influenced by learning. Hence, the drinking behavior, water intake, and flavor acceptance/preference of animals used in toxicology experiments could be subject to learning experiences with the test compound. Physiological symptoms of stress produced by water deprivation may be distinguishable from the symptoms associated with other generalized stressors, such as food deprivation, but doing so may be beyond the scope of most developmental or reproductive toxicity studies. Use of concurrent controls, paired to test groups for water consumption, could help distinguish between the direct effects of a test toxicant as opposed to effects of reduced water consumption alone. Birth Defects Res (Part B), 86:157–175, 2009. ©2009 Wiley-Liss, Inc.