Genes of the Escherichia coli pur regulon are negatively controlled by a repressor-operator interaction.

Fusions of lacZ were constructed to genes in each of the loci involved in de novo synthesis of IMP. The expression of each pur-lacZ fusion was determined in isogenic purR and purR+ strains. These measurements indicated 5- to 17-fold coregulation of genes purF, purHD, purC, purMN, purL, and purEK and thus confirm the existence of a pur regulon. Gene purB, which encodes an enzyme involved in synthesis of IMP and in the AMP branch of the pathway, was not regulated by purR. Each locus of the pur regulon contains a 16-base-pair conserved operator sequence that overlaps with the promoter. The purR product, purine repressor, was shown to bind specifically to each operator. Thus, binding of repressor to each operator of pur regulon genes negatively coregulates expression.     

Cytochemical localization of glycoconjugates in rat peritoneal mast cells during degranulation

Summary Cytochemical methods for the localization of glycoconjugates including concanavalin A-horseradish peroxidase (ConA-HRP) and dialysed iron were used to study the distribution of glycoconjugates in mast cell granules during degranulation. The ConA-HRP method revealed intense staining of discharged mast cell granules. Dialysed iron staining was seen at the granule periphery, with extruded granules exhibiting more intense staining than undischarged granules.Some of the work reported herein was performed in partial fulfillment of the requirements for a Ph.D. degree.     

Localization of proteoglycan monomer and link protein in the matrix of bovine articular cartilage: An immunohistochemical study

Using monospecific antisera and immunofluorescence microscopy, proteoglycan monomer (PG), and link proteins were demonstrated throughout the extracellular matrix of bovine articular cartilage. A narrow band of strong pericellular staining was usually observed for both molecules, indicating a pericellular concentration of proteoglycan monomer: this conclusion was supported by dye-binding studies. Whereas PG was evenly distributed throughout the remaining matrix, more link protein was detectable in interterritorial sites in middle and deep zones. Well-defined zones of weaker territorial staining for link protein stained strongest for chondroitin sulfate. Trypsin treatment of cartilage resulted in a loss of most of the PG staining, but some selective retention of link protein, particularly around chondrocytes in the superficial zone at and near the articular surface. This residual staining was largely removed if sections were fixed after chondroitinase treatment. After extraction of cartilage with 4M guanidine hydrochloride, only PG remained and this was concentrated in the superficial zone. These observations are shown to support the concept of aggregation of PG and link protein with hyaluronic acid (HA) in cartilage matrix, and the binding of PG and link protein to HA, which is attached to the chondrocyte surface. Culture of cartilage depleted of PG and link protein by trypsin demonstrated that individual chondrocytes can secrete both PG and link proteins and that the organization of cartilage matrix can be regenerated in part over a period of 4 days.     

Biosynthesis of membrane bound Ig and secretion of Ig by chicken lymphoid cells.

The metabolic turnover of membrane proteins of chicken lymphoid cells is studied, using a double isotope labeling technique (i.e., [14C]amino acid pulse and [3H]leucine chase). Compared with other membrane proteins, the metabolic turnover of membrane bound immunoglobulins (M-Ig) is very slow. There was no difference in the turnover between M-Ig and specific antigen binding receptor immunoglobulins. Immunoglobulins appear to be a stable constituent of the lumphocyte membrane. Cellular kinetic experiments show that the rate of biosynthesis of secreted immunoglobulins (S-Ig) is nearly ten times as much as that of M-Ig, suggesting that metabolic pathway leading to M-Ig are distinct from those leading to S-Ig. The difference in 3H/14C ratios between S-Ig and M-Ig reflects the rate of biosynthesis of these immunoglobulins by two types of bursa derived lymphoid cells.     

PLASMA CHOLINE: ITS TURNOVER AND EXCHANGE WITH BRAIN CHOLINE1

—The kinetics of plasma choline (Ch) and the uptake of plasma Ch into the brain were studied by means of intravenous infusion of [²H₄]Ch at various rates into anaesthetized and conscious rats. [²H₄]Ch levels in both arterial and venous plasma at steady state were linearly related to the infusion rate; however, unlabelled Ch levels were independent of infusion rate. [²H₄]Ch levels were higher in the arterial plasma than in the venous plasma, while unlabelled Ch levels were higher in the venous plasma than in the arterial plasma. It was concluded that Ch is being generated in the brain and is released into the venous effluent. The supply of Ch to the plasma is not decreased if the plasma Ch level is increased. The clearance and turnover of Ch in the compartment of its initial distribution are 75 ml kg^-1 min^-1 and 716 nmol kg^-1 min^-1, respectively. The uptake of plasma Ch into the brain is not saturated even at very high levels of plasma Ch.     

Increased signal complexity is associated with increased mating success

The evolution of complex signals has often been explored by testing multiple functional hypotheses regarding how independent signal components provide selective benefits to offset the costs of their production. In the present study, we take a different approach by exploring the function of complexity per se. We test the hypothesis that increased vibratory signal complexity—based on both proportional and temporal patterning—provides selective benefits to courting male Schizocosa stridulans wolf spiders. In support of this hypothesis, all of our quantified metrics of vibratory signal complexity predicted the mating success of male S. stridulans. The rate of visual signalling, which is mechanistically tied to vibratory signal production, was also associated with mating success. We additionally found evidence that males can dynamically adjust the complexity of their vibratory signalling. Together, our results suggest that complexity per se may be a target of female choice.     

Metformin ameliorates olanzapine-induced disturbances in POMC neuron number,axonal projection,and hypothalamic leptin resistance

Antipsychotics have been widely accepted as a treatment of choice for psychiatric illnesses such as schizophrenia. While atypical antipsychotics such as aripiprazole are not associated with obesity and diabetes, olanzapine is still widely used based on the anticipation that it is more effective in treating severe schizophrenia than aripiprazole, despite its metabolic side effects. To address metabolic problems, metformin is widely prescribed. Hypothalamic proopiomelanocortin (POMC) neurons have been identified as the main regulator of metabolism and energy expenditure. Although the relation between POMC neurons and metabolic disorders is well established, little is known about the effects of olanzapine and metformin on hypothalamic POMC neurons. In the present study, we investigated the effect of olanzapine and metformin on the hypothalamic POMC neurons in female mice. Olanzapine administration for 5 days significantly decreased Pomc mRNA expression, POMC neuron numbers, POMC projections, and induced leptin resistance before the onset of obesity. It was also observed that coadministration of metformin with olanzapine not only increased POMC neuron numbers and projections but also improved the leptin response of POMC neurons in the olanzapine-treated female mice. These findings suggest that olanzapine-induced hypothalamic POMC neuron abnormality and leptin resistance, which can be ameliorated by metformin administration, are the possible causes of subsequent hyperphagia.