Study of Poaceae phenology in a Mediterranean climate. Which species contribute most to airborne pollen counts?

The present study sought to determine which of the common Poaceae species in the study area contribute most to the Poaceae pollen season curve, and to determine the phenological behaviour of the species studied. The different floral phenophases in thirty-three Poaceae species common in and around the city of Córdoba (SW Iberian Peninsula) were checked periodically over the period 2004–2006. Results showed that longer phenological ranges were recorded in the coolest and wettest year, and shorter ranges in the warmest and driest year. Moreover, ranges varied as a function of altitude: populations in lower-lying areas flowered earlier than those at higher altitudes. The results, taken in conjunction with the findings of preliminary research into potential pollen production, showed that probably only four of the Poaceae species studied—Dactylis glomerata, Lolium rigidum, Trisetaria panicea and Vulpia geniculata—were major contributors to the Poaceae airborne pollen curve.     

Evidence for a role of protein kinase C zeta subspecies in maturation of Xenopus laevis oocytes.

A number of studies have demonstrated the activation of phospholipase C-mediated hydrolysis of phosphatidylcholine (PC-PLC) both by growth factors and by the product of the ras oncogene, p21ras. Evidence has been presented indicating that the stimulation of this phospholipid degradative pathway is sufficient to activate mitogenesis in fibroblasts as well as that it is sufficient and necessary for induction of maturation in Xenopus laevis oocytes. However, the mechanism whereby PC-PLC transduces mitogenic signals triggered by growth factors or oncogenes remains to be elucidated. In this study, data are presented that show the involvement of protein kinase C zeta subspecies in the channelling of the mitogenic signal activated by insulin-p21ras-PC-PLC in Xenopus oocytes as well as the lack of a critical role of protein kinase C isotypes alpha, beta, gamma, delta, and epsilon in these pathways.     

The chemical characterization of melanin contained in substantia nigra of human brain

The pigment of substantia nigra human brain has been extracted by a mild procedure consisting of washes with phosphate buffer, methanol and incubation with SDS-proteinase. Pyrolisis gas chromatography mass spectrometry infrared spectrometry, termogravimetric analysis and elemental analysis were the techniques used for the chemical characterization. An indole moiety bound to a sulfur containing amino acid and to palmitic acid were the main aspects found in the structure. The presence of a 7% inorganic component was observed. This probably contains Fe, Cu, Zn and Cr which are also relevant, for the formation and the role of melanin in substantia nigra neurons. The fatty acid moiety is chemically bound to the indole structure as it was not eliminated by repeated methanol washing. The same situation occurs for the sulfur containing gropu. Considering these data and the most abundant molecules present in substantia nigra the precursor of neuromelanin seems to be a cysteinyl-cethecol, to which is then bound a palmityl group.     

Effect of dissolved oxygen concentration on repeated production of gluconic acid by immobilised mycelia of Aspergillus niger

Summary Gluconic acid production from corn starch hydrolysates by immobilised mycelia of Aspergillus niger was studied in a laboratory-scale stirred fermentor at different concentrations of glucose (S ₀) and dissolved oxygen (DO) in the culture broth. Its evolution was simulated quite well by applying the same unstructured model set up in previous experiments using stirred and airlift fermentors. In particular, increasing S ₀ in the range 70–160 g/l, although uninfluential upon the yield coefficient, resulted in an exponential decrease in the gluconic acid formation rate constant. Nevertheless, the greater the oxygen transfer rate used in the fermentor, the smaller the inhibitor effect of the higher concentrations of glucose on gluconate productivity became. This was achieved by enriching the inlet air with pure oxygen so as to maintain the DO level above 75% saturation throughout the fermentation. Offprint requests to: M. Moresi     

Cloning and characterization of a linear 2.3 kb mitochondrial plasmid of maize

Summary A linear 2.3 kb DNA molecule found in maize mitochondria was cloned into pUC8. A natural deletion of this plasmid, found in cmsT and some N (fertile) types of maize plants, was mapped to one end of the plasmid. A minor sequence homology to S-2, another linear mitochondrial plasmid, was detected, as well as more significant sequence homology with chloroplast and maize nuclear DNA. Hybridization to teosinte mitochondrial DNA (mtDNA) revealed the presence of part of the maize plasmid in the high molecular weight mtDNA of the maize relatives. RNA dot hybridization indicates that the plasmid is transcribed in mitochondria. The termini of the 2.3 kb linear plasmid contain inverted repeated sequences; of the first 17 nucleotides of the termini, 16 are identical to the terminal inverted repeats of the linear S plasmids found in the mitochondria of cmsS maize plants.     

Growth hormone releasing effect of hpGRF-40 in rats at different time intervals following ablation of the mediobasal hypothalamus

We have investigated the effect of hypothalamo-pituitary disconnection in the rat on the growth hormone (GH) responsiveness to human pancreatic GH-releasing factor (hpGRF). Adult female rats, sham-operated (sham-op) or bearing a complete mechanical ablation of the mediobasal hypothalamus (MBH-A) were challenged, while under urethane anesthesia, with hpGRF-40 (20,100,500 ng/rat i.v.) at different time intervals after surgery. In sham-op rats only 500 ng/rat of hpGRF-40 stimulated GH release, while in 1-and 7-day MBH-A rats the stimulation also occurred with the lower hpGRF doses and the rise in plasma GH was greater than in sham-op controls. Twenty-one and 42 days after the placing of the lesions the GH response to hpGRF-40 was still present at the 500 ng/rat dose, though it was smaller than in sham-op controls. Evaluation of pituitary GH content demonstrated a progressive and rapid decline starting the first day after the placing of the lesions. These data indicate that GH responsiveness to hpGRF is: 1) enhanced in the anterior pituitary shortly after hypothalamo-pituitary disconnection and, 2) despite a striking reduction of the pituitary GH stores, it is maintained after these lesions.The physiologic growth hormone (GH) releaser in the rat is GH-releasing factor and, recently, a group of peptides has been characterized from human pancreatic tumors (hpGRFs) (1,2) which are potent and specific GH-releasers in both animals (3) and man (4). The availability of these peptides, which show a high degree of homology with the physiologic rat hypothalamic GRF (5), offers the unique opportunity to assess somatotrope responsiveness to GRF molecules in rats with hypothalamo-pituitary disconnection.In this study we have first evaluated the GH pituitary responsiveness to increasing doses of hpGRF-40 in rats following mechanical ablation of the mediobasal hypothalamus (6). These rats, by definition, lack the effect of both central nervous system (CNS) inhibitory (e.g. somatostatin) and stimulatory (e.g. GRF) influences to GH release. With the aim to ascertain how the lack of these two opposing inputs reflects on the secretory capacity of the somatotropes, we also investigated the GH response to hpGRF-40 at different time intervals after the lesioning. In a study in rats with electrolytic lesions of the ventromedial-arcuate region of the hypothalamus Tannenbaum et al (7) had shown persistence of the GH response to huge doses of a hpGRF analog.     

Thymosin-beta 4 gene. Preliminary characterization and expression in tissues, thymic cells, and lymphocytes

A cDNA for rat thymosin-beta 4 was used to investigate the expression of this gene in different tissues, thymic cells, and lymphocytes. Hybridization analysis of total RNA from 13 rat tissues demonstrated the presence of an 800 nucleotides-long mRNA in all the tissues surveyed, with the highest levels in spleen, thymus, and lung. Examination of thymic cells showed that the thymosin-beta 4 gene is predominantly expressed in thymocytes. The thymosin-beta 4 mRNA was also studied in Ig+ and Ig- lymphocytes, being fourfold more abundant in Ig- than Ig+ splenic lymphocytes, whereas similar levels were found in both types of blood cells. The analysis of RNA from T cells at different maturation stages evidenced slight differences in their thymosin-beta 4 mRNA content, indicating that thymosin-beta 4 gene expression is not clearly related to the differentiation process of T cells. All these results do not support the roles for thymosin-beta 4 in cellular immunity and differentiation of lymphoid cells, suggesting a more general function for this peptide. Preliminary characterization of the human beta 4 gene by restriction analysis disclosed a complicated pattern consistent with multiple genes and/or introns. The analysis of genomic DNA from different species ranging from humans to Escherichia coli showed that this gene is only highly conserved in mammals.