Microglial cells in the central nervous system of the rabbit and rat: cytochemical identification using two different lectins

Microglial cells were selectively demonstrated in the central nervous system of adult rabbits and rats using lectin histochemistry. Biotinylated Ricinus communis agglutinin-120 (RCA-1) and biotinylated Griffonia simplicifolia B4 isolectin (GSA I-B4) were used as histochemical markers on sections of Bouin-fixed paraffin-embedded cerebrum and cerebellum. Results were quite similar using both lectins and both species. GSA I-B4 resulted in a better staining in the rat, while RCA-1 labelling was superior in the rabbit. Neither neurons nor glial cells other than microglia were stained with our technique. Lectin histochemistry applied for the detection of microglial cells appears to be of sufficient selectivity and may be considered as an important tool in the morphological and neurobiological study of these cells.     

The ilvIH operon of Escherichia coli is positively regulated.

The ilvIH operon of Escherichia coli (located near min 2) encodes acetohydroxyacid synthase III, an isozyme involved in branched-chain amino acid biosynthesis. A strain with lacZ fused to the ilvIH promoter was constructed. Transposon Tn10 was introduced into this strain, and tetracycline-resistant derivatives were screened for those in which ilvIH promoter expression was markedly reduced. In one such derivative, strain CV1008, beta-galactosidase expression was reduced more than 30-fold. The transposon giving rise to this phenotype inserted near min 20 on the E. coli chromosome. Extract from a wild-type strain contains a protein, the IHB protein, that binds to two sites upstream of the ilvIH promoter (E. Ricca, D. A. Aker, and J. M. Calvo, J. Bacteriol. 171:1658-1664, 1989). Extract from strain CV1008 lacks IHB-binding activity. These results indicate that the IHB protein is a positive regulator of ilvIH operon expression. The gene that encodes the IHB protein, ihb, was cloned by complementing the transposon-induced mutation. Definitive evidence that the cloned DNA encodes the IHB protein was provided by determining the sequence of more than 17 amino acids at the N terminus of the IHB protein and comparing it with the nucleotide sequence. A mutation that prevents repression of the ilvIH operon by leucine in vivo and that alters the DNA-binding characteristics of the IHB protein in vitro was shown to be an allele of the ihb gene. The ihb gene is identical to oppI, a gene that regulates the oppABCDF operon (E. A. Austin, J. C. Andrews, and S. A. Short, Abstr. Mol. Genet. Bacteria Phages, p. 153, 1989). Thus, oppI/ihb encodes a protein that regulates both ilvIH, an operon that is repressed by leucine, and oppABCDF, an operon involved in peptide transport that is induced by leucine. We propose that the designation lrp be used in the future instead of oppI or ihb and that Lrp (leucine-responsive regulatory protein) be used in place of IHB.     

INFLORESCENCE SIZE AND FRUIT DISTRIBUTION AMONG INDIVIDUALS IN THREE ORCHID SPECIES

Fruit distribution among individuals in populations of three orchid species was analyzed. Fruit set was low in the three species. The distribution of fruits in the non-autogamous species was skewed to the right, with high variance: mean ratios, and a moderate to high proportion of fruitless plants. Larger inflorescence size did not necessarily result in an increase in percent fruit set but tended to increase the probability to produce at least one fruit. Pollinator-mediated selection on inflorescence size through fruit production may be limited by the low overall level of visitation and the resulting uncertainty of pollination at the individual level.     

Long-chain fatty acids bound to alpha-fetoprotein and to serum albumin from fetal and adult pig

1. Pig alpha-fetoprotein (AFP) and albumin were isolated from fetal serum by DEAE-Sephadex ion exchange chromatography combined with Cibacron Blue-Sepharose and trypsin-Sepharose adsorptions. 2. AFP, fetal albumin and adult albumin carried 2.6, 2.4, and 1.9 moles of fatty acids per mole of protein, respectively. 3. Most of fatty acids bound to AFP were polyunsaturated: mainly arachidonic (20:4, n-6) and docosahexaenoic (22:6, n-3) acids, which accounted respectively for 21.7 and 18.8% of the total fatty acids. 4. By contrast, the fatty acids found in the albumins (fetal and adult) were preferentially saturated and monounsaturated. 5. Arachidonic acid was a minor component in both albumins, and no docosahexaenoic acid was detected.     

Characterization, origin and evolution of alpha-fetoprotein and albumin in postnatal rat brain

1. The levels of AFP and albumin in rat brain at birth were 77 and 340 micrograms per g of tissue, respectively. These levels quickly dropped with age. AFP was undetectable in 20 days brain extracts whereas 30 micrograms of albumin per g of brain were still measured. 2. AFP from brain and serum were identical by immunodiffusion, electrophoresis and immuno-affinoelectrophoresis with free Concanavalin A. 3. No in vitro synthesis of AFP and albumin in the postnatal brain was observed. However, the total amount of AFP in the developing rat brain increases from birth to 4-5 days post-partum.     

Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

Evolution of the pineal gland in the adult chicken.

The structural pattern of the pineal gland in the hen corresponds to a more advanced stage of the evolution which began in an early period of the animal's life. This evolution corresponds mainly to the transformation of the large follicular cavities into cellular 'rosettes'. The parafollicular layer disappears from the rosette wall which thus remains with only one row of cells (A and B pinealocytes). The cellular hypertrophy and the great development of the pinealocyte organelles in the adult pineal gland makes us think of this gland as a functionally active organ. This functional activity must have remained during the entire period of the time studied (1--5 years), due to the ultrastructural uniformity found and due to the fact that we could not observe any type of degenerative process in the gland.