Short-term adrenalectomy increases glucocorticoid and mineralocorticoid receptor mRNA in selective areas of the developing hippocampus.

In the central nervous system, adrenal steroids bind to two different types of corticosteroid receptors: glucocorticoid (GR) or mineralocorticoid (MR). In vitro biochemical and autoradiographic techniques have been used to infer GR and MR protein abundance in the hippocampus. Adrenalectomy (ADX) is routinely performed to measure the normal receptor number in absence of corticosterone (B), which would otherwise interfere with the binding reaction, The developing rodent has low basal B levels until the third week of life.

[Equality in medical education policy in Mexico].

We compared the results of the educational policies of public versus private medical schools and traditional versus module-based medical programs. The comparison centers on the political value of equality. The hypotheses are the following: a) Public and module-based schools offer more equality of opportunities for enrollment, permanence and graduation of students than private and traditional schools; b) medical schools maintain their educational policies over time.

[The supply of physicians in Mexico: excess and shortage].

The purpose of this paper is to find out whether a decrease in the number of medical undergraduates doing their social service has any influence on the quantity of medical services provided by health care institutions in Mexico. Spearman's Rank Test was used to correlate the number of medical undergraduates and the number of services. Data for analysis were taken from the statistical information bulletins of the Ministry of Health for the decade of the 1980's.

Development of pituitary pro-opiomelanocortin gene and peptide expression: characterization and effect of repeated intermittent maternal isolation.

The dynamics of pro-opiomelanocortin (POMC) biosynthesis in the adult rat are altered by demands imposed on the system, such that acute stress increases in the efficiency of anterior pituitary (AP) posttranslational events, while repeated stress increases pretranslational events. In contrast, the developing animal has a limited adrenocortical response to acute stress during the first 2 weeks of life (stress nonresponsive period). In this study, we investigated how the maturing AP and intermediate lobe (IL) POMC cells respond to repeated demand.

Carbamazepine metabolism in humans: effect of concurrent anticonvulsant therapy.

Free and total carbamazepine (CBZ) and carbamazepine-epoxide (CBZ-EP) plasma levels were obtained on 113 patients with epilepsy (18-61 years old) controlled on either monotherapy or coadministration with either phenobarbital (PB), phenytoin (PHT), valproic acid (VPA), or all three. A subset of patients were administered tetradeuterium labeled CBZ to evaluate the effects of autoinduction and coadministration of VPA on the kinetics of CBZ and its metabolite CBZ-EP. Polytherapy had variable effect on free and total CBZ plasma levels compared to monotherapy.

Interaction of [3H]spiperone with rat striatal dopamine D-2 receptors: kinetic evidence for antagonist-induced formation of ternary complex.

The characteristics of [3H]spiperone interactions with rat striatal dopamine D-2 receptor were investigated. Although the association of [3H]spiperone occurred monoexponentially, the pseudo-first order rate constant of association showed a hyperbolic dependence on ligand concentration. The data were therefore analyzed with the assumption of a two-step binding reaction leading to ligand-induced receptor isomerization.

Structure-activity relationships of sparsomycin and its analogues. Inhibition of peptide bond formation in cell-free systems and of L1210 and bacterial cell growth.

The biological activity of 14 analogues of sparsomycin (1) was studied in cell-free systems of Escherichia coli, Saccharomyces cerevisiae, and Sulfolobus solfataricus by measuring the inhibition of protein synthesis. The inhibition of L1210 colony formation in soft agar and bacterial cell growth in solid as well as in liquid medium was also examined. Each analogue possesses not more than two structural modifications of the sparsomycin molecule.

Thermochemistry of the interaction between peptides and vancomycin or ristocetin.

The thermodynamics of the interaction between the glycopeptide antibiotics vancomycin and ristocetin and bacterial peptidoglycan peptide analogs have been studied by means of a microcalorimetric titration technique. From results of the calorimetric measurements, changes in Gibbs energies, enthalpies, entropies and heat capacities for the binding reactions have been calculated. The derived thermodynamic data have been discussed on the basis of stereochemical data available for the interaction of acetyl-D-alanyl-D-alanine with each of the two antibiotics.

Structural modification of Escherichia coli peptidoglycan induced by bicyclomycin.

We have studied the modification of Escherichia coli peptidoglycan induced by bicyclomycin. For this purpose liquid chromatography for peptidoglycan analysis has been used. The main alteration found was an increase of diaminopimelyl-diaminopimelyl bridge containing subunits.

Specific location of penicillin-binding proteins within the cell envelope of Escherichia coli.

This communication deals with the location of penicillin-binding proteins in the cell envelope of Escherichia coli. For this purpose, bacterial cells have been broken by various procedures and their envelopes have been fractioned. To do so, inner (cytoplasmic) and outer membranes were separated by isopycnic centrifugation in sucrose gradients.

An unusual linkage between polysaccharides and some major proteins from the outer membrane of Escherichia coli.

A small population of OmpA, a major protein from the outer membrane of Escherichia coli, was found covalently associated with either lipopolysaccharide or O-antigen polysaccharide. Radioactive oligosaccharide was elicited linked to OmpA after treatment of the membranes with periodate that hydrolyzed large sugars. Association of saccharides to OmpA could be enhanced by treatment of the outer membrane with NaBH4.

Penicillin binding proteins: role in initiation of murein synthesis in Escherichia coli.

The consequences of the specific inhibition of penicillin binding proteins (Pbps) by beta-lactam antibiotics immediately before resumption of active growth in Escherichia coli suggest that inhibition of murein biosynthesis does not prevent the earlier steps of the initiation of cell growth in mass. The activity of Pbp 2 is apparently critical for the initiation of murein biosynthesis. Provided that Pbp 2 remains active, the other Pbps (1a, 1b, 3, 4, 5, and 6) can be inhibited without any noticeable effect on the initial rate of incorporation of new precursors into macromolecular peptidoglycan.

Final steps of the maturation of Omp F, a major protein from the outer membrane of Escherichia coli.

Pulse-labelling experiments with E. coli cells allowed us to follow the incorporation of de novo proteins into the outer membrane of the cell envelope. Labelled membrane samples containing increasingly different levels of newly synthesized Omp F protein were subjected to chemical cross-linking with a bifunctional cleavable reagent in order to investigate the process of trimer formation of the protein.

Location of some proteins involved in peptidoglycan synthesis and cell division in the inner and outer membranes of Escherichia coli.

Inner and outer membranes of Escherichia coli were separated by isopycnic centrifugation in sucrose gradients and analyzed for the presence of penicillin-binding proteins. All penicillin-binding proteins--except penicillin-binding protein 3, which is found almost exclusively in the cytoplasmic membrane and is involved in septum formation--are also found in gradient fractions corresponding to the outer membrane. Our results support the hypothesis that approximately half of the total amount of penicillin-binding proteins may be sacculus-located proteins linked to the outer membrane, probably through peptidoglycan bridges.

Structural modifications in the peptidoglycan of Escherichia coli associated with changes in the state of growth of the culture.

By determining the composition in muropeptides of the murein of a number of strains of Escherichia coli, purified from cells at various states of growth, the sacculus was found to be considerably modified when cells stop active growth. Murein from resting cells becomes hypercross-linked and richer in covalently bound lipoprotein, whereas the mean length of the glycan chains is considerably reduced. The alteration of the sacculus occurs progressively during the transitions from active growth to stationary phase and vice versa.

Penicillin-binding proteins and peptidoglycan peptide-interacting proteins.

Peptidoglycan peptide-interacting proteins (PPIPs) which include the penicillin-binding proteins (PBPs) are bacterial enzymes which interact with beta-lactams (including penicillins and cephalosporins) and/or acyl-D-ala-D-ala analogues of a non-beta-lactam structure. The PBPs and other PPIPs of Escherichia coli are reviewed.

Labelling of penicillin-binding proteins with a photoreactive peptidoglycan-peptide analogue.

Transpeptidases, DD-carboxypeptidases and endopeptidases from bacteria are usually detected by labelling with radioactive beta-lactam antibiotics, due to a selective stabilization of the enzyme-antibiotic complex, and are therefore generally known as penicillin-binding proteins (PBPs). However, as a general rule, PBPs cannot be detected by labelling with real peptidoglycan substrate analogues other than beta-lactams, partly due to the fact that the acyl intermediates formed do not usually accumulate. We here report the chemical synthesis of a radioactive photoreactive derivative of the peptidoglycan substrate L-lysyl-D-alanyl-D-alanine which is able, due to the shortness of its activated state, to label a number of PBPs of Escherichia coli by quenching the reaction at the intermediate step.

Analysis of the different molecular forms of penicillin-binding protein 1B in Escherichia coli ponB mutants lysogenized with specialized transducing lambda (ponB+) bacteriophages.

Penicillin-binding protein (pbp) 1b, the main DD-transpeptidase/transglycosylase of Escherichia coli, is normally present in the cell in three molecular forms alpha, beta and gamma, differentiated by their mobility in sodium dodecyl sulfate/polyacrylamide gel electrophoresis. The three molecular forms are enzymatically active in vitro and their relative amounts are kept fairly constant in most labelling experiments with radioactive beta-lactam antibiotics. In this paper, we have analyzed the expression of ponB (mrcB), the structural gene for pbp 1b, and the relation among the three forms of pbp 1b in ponB strains lysogenyzed by lambda 540 (ponB+) recombinant bacteriophages.

The mode of action of zaluzanin C, an inhibitor of translation in eukaryotes.

Zaluzanin C, a substance extracted from several species of the genus Zaluzania (Compositae), has been shown to inhibit protein synthesis in intact HeLa cells preferentially to DNA and RNA synthesis. "In vitro" protein synthesis was also blocked by zaluzanin C and the study of the effects of the drug on resolved model systems indicates that it inhibits enzymic translocation of peptidyl-tRNA specifically.