Phorbol esters inhibit apoptosis in IL-2-dependent T lymphocytes

The effect of phorbol esters on the proliferation and survival of interleukin-2(IL-2)-dependent cells was studied using an IL-2-dependent T cell line (CTLL-2) and blasts of BALB/c mouse spleen cells stimulated with Concanavalin A. Addition of phorbol 12,13-dibutyrate (PDBu) to CTLL-2 or ConA blasts induces a mitogenic response which is 25-40% of that elicited by IL-2. Interleukin 2 deprivation leads to a marked decline in the number of viable cells (50% of CTLL-2 cells have died after 8-10 hours incubation in IL-2-free medium). The mechanism of cell death seems to correspond to the suicide process known as apoptosis since an early degradation of DNA into oligonucleosome-size fragments could be observed after removal of the growth factor. When present, PDBu inhibits both the activation of the endonuclease and the development of the cell death process in CTLL-2 cells and ConA-blasts deprived of IL-2. Taken together, our results suggest that the tumor promoters phorbol esters inactivate in T cells the mechanism of cell elimination triggered by IL-2 deprivation and may help to explain why transformation of T cells decreases or even abolishes their requirements of IL-2 for survival and growth.     

Relationship between a 47-kDa cytoplasmic membrane polypeptide and nitrate transport in Anacystis nidulans

The polypeptide composition of cytoplasmic membranes of the cyanobacterium Anacystis nidulans changes in response to variations in the nitrogen source available to the cells, differing specifically in the amount of a polypeptide of 47-kDa molecular mass. Synthesis of the polypeptide and expression of nitrate transport activity are repressed by ammonium. Transfer of ammonium-grown cells to a medium containing nitrate as the sole nitrogen source results in parallel development of the 47-kDa polypeptide and nitrate transport activity of the cells. These results suggest the involvement of the 47-kDa cytoplasmic membrane polypeptide in nitrate transport by A. nidulans.     

The caudal spinal cord of coho salmon (Oncorhynchus kisutch): Immunocytochemical evidence of a “caudal serotoninergic system”

Summary The caudal spinal cord of the coho salmon was investigated by means of immunocytochemistry using antisera against serotonin, urotensin I, urotensin II, somatostatin and a urea-extract of bovine Reissner's fiber (AFRU). Populations of serotonin-immunoreactive (IR) neurons were found rostral and dorsal to the urophysis in close spatial association with caudal secretory neurons. Thick, smooth serotonin-IR processes extended toward the external surface of the spinal cord where they displayed conspicuous terminal dilatations. Thin, beaded serotonin-IR fibers appeared to innervate populations of caudal secretory and somatostatin-IR cerebrospinal fluid-contacting neurons. Most caudal neurosecretory cells displayed both urotensin I and urotensin II immunoreactivities; only a minority reacted exclusively with either urotensin I or urotensin II antisera. Urotensin II-IR and somatostatin-IR cerebrospinal fluid (CSF)-contacting neurons were found as an integral component of the central canal wall in the caudal spinal cord and filum terminale; their dendritic processes appeared to contact Reissner's fiber, which displayed a weak AFRU-immunoreactivity while inside the central canal, but became strongly reactive in the interior of the terminal ventricle as it formed the massa caudalis. The distribution of serotoninergic processes points to a regulatory role in the function of caudal secretory and CSF-contacting neurons and to a putative serotonin release into the subarachnoid space and/or meningeal vasculature. It is also suggested that the CSF-contacting neurons of the central canal may participate in a feedback mechanism controlling the secretory activity of the subcommissural organ.Supported by Grant A/1095-1 from the International Foundation for Science, Sweden, to C.Y.; Grant I/63-476 from Volkswagen-Stiftung to E.R.; and Grant S-85-39 from the Dirección de Investigaciones, Universidad Austral de Chile     

Characterization of the cellulase complex from Cellulomonas grown on bagasse pith

Summary The effect of physico-chemical parameters on the cellulolytic activity of Cellulomonas sp. IIbc grown on sugarcane bagasse pith was investigated, and the optimum ranges for enzyme activity were established. The cellulases were more stable when incubated at the optimum growth temperature (32°C) than under optimum activity conditions (45°C for -glucosidases and 50°C for CMC- and FP-cellulases). The -glucosidases were the thermostability-limiting enzymes of the complex. Two types of endoglucanases could be recognized according to their adsorption properties on bagasse: one weakly-bound and one tightly-bound type, the latter constituting approximately 73% of the extracellular endoglucanases at exponential growth phase. Four forms active on filter paper and three active on CMC were obtained by HPLC separation of the extracellular fraction of the culture at stationary phase.Abbreviations CMC carboxymethylcellulose - FP filter paper     

Distribution of intraventricularly injected horseradish peroxidase in cerebrospinal fluid compartments of the rat spinal cord

Summary The circulation of the cerebrospinal fluid along the central canal and its access to the parenchyma of the spinal cord of the rat have been analyzed by injection of horseradish peroxidase (HRP) into the lateral ventricle. Peroxidase was found throughout the central canal 13 min after injection, suggesting a rapid circulation of cerebrospinal fluid along the central canal of the rat spinal cord. It was cleared from the central canal within 2 h, in contrast with the situation in the brain tissue, where it remained in the periventricular areas for 4 h. In the central canal, HRP bound to Reissner's fiber and the luminal surface of the ependymal cells; it penetrated through the intercellular space of the ependymal lining, reached the subependymal neuropil, the basement membrane of local capillaries, and appeared in the lumen of endothelial pinocytotic vesicles. Furthermore, it accumulated in the labyrinths of the basement membrane contacting the basolateral aspect of the ependymal cells. In ependymocytes, HRP was found in single pinocytotic vesicles. The blood vessels supplying the spinal cord were classified into two types. Type-A vessels penetrated the spinal cord laterally and dorsally and displayed the tracer along their external wall as far as the gray matter. Type-B vessels intruded into the spinal cord from the medial ventral sulcus and occupied the anterior commissure of the gray matter, approaching the central canal. They represented the only vessels marked by HRP along their course through the gray matter. HRP spread from the wall of type-B vessels, labeling the labyrinths, the intercellular space of the ependymal lining, and the lumen of the central canal. This suggests a communication between the central canal and the outer cerebrospinal fluid space, at the level of the medial ventral sulcus, via the intercellular spaces, the perivascular basement membrane and its labyrinthine extensions.     

Respiratory response to chemical stimuli and exercise capacity under conditions of acute hypoxia in elite mountain climbers]

To investigate the factors that modulate exercise performance at extreme altitude, the role of the following variables was analyzed in 16 climbers: 1) ventilatory response to chemical stimuli (hypoxia and hypercapnia); and, 2) maximum exercise performance while breathing room air and during acute hypoxia (F1O2, 0.11). Seven climbers (elite climbers, AE) had previously ascended to 8,000 m or more above sea level, and 9 (A) had never achieved such extreme altitude. Then healthy sedentary subjects (C) of similar age (31.1 +/- 6.0 SD years) were used as control group. Elite climbers showed higher ventilatory responses to both transient hypoxia (-0.49 +/- 0.13 L x min-1 x %-1) (p less than 0.05) and progressive hypoxia (-0.47 +/- 0.13 L x min-1 x %-1) than C (-0.33 +/- 0.14 and -0.30 +/- 0.15 L x min-1 x %-1, respectively). By contrast, no differences were observed between the two groups of climbers. The ventilatory response to hypercapnia was higher in AE (3.04 +/- 1.03 L x min-1 mmHg-1) compared to A (1.85 +/- 0.73 L x min-1 mmHg-1) (p less than 0.05) but similar to that observed in C. Breathing 11% O2, maximum workload and oxyhemoglobin desaturation during maximum exercise were similar in both groups of climbers. Additionally, the ventilatory response to hypoxia did not correlate with maximum workload (F1O2, 0.11), maximal ventilation during exercise (F1O2, 0.11), nor with the altitude score. The present study supports previous reports that inform about the role of the ventilatory response to hypoxia in the exercise performance at high altitude.(ABSTRACT TRUNCATED AT 250 WORDS)     

Principles of environmental physics

Book Review

Principles of environmental physicsJ.L. Monteith and M.H. Unsworth Second edition. London: Edward Arnold, 1990. xii + 291 pages. £30.00 (hardback), £14.95 (paperback). ISBN 0-7131-2931-X     

Lipid accumulation inRhodotorula glutinis on sugar cane molasses in single-stage continuous culture

Microbial lipids produced byRhodotorula glutinis grown in continuous culture with molasses under nitrogen-limiting conditions were evaluated and the effects of growth rate on fatty acid composition were studied. As the growth rate decreased, cell biomass, lipid content and lipid yield gradually increased. The maximum lipid content recorded was 39% (w/w) of dry cell biomass at a dilution rate of 0.04 h^–1. The growth rate also affected fatty acid composition: oleic acid decreased with decreasing growth rate while stearic acid increased.     

Changes in soil microflora associated with control of Sclerotium Rolfsii by Furfuraldehyde

The efficacy of 2‐furfuraldehyde for control of Sclerotium rolfsii was studied in laboratory and greenhouse experiments. Mycelial growth of the fungus was reduced proportionally with concentrations of 0.1–0.5 ml furfuraldehyde l^‐1 agar medium, and viability of sclerotia diminished on exposure to 2‐furfuraldehyde vapours. Detectable populations of bacteria and fungi, including Trichoderma spp., were reduced significantly (9=0.05) when furfuraldehyde was added to the agar used for soil dilution plates of untreated soil. Repeated treatments of natural soil with the fumigant significantly increased populations of Trichoderma spp. and bacteria, but diminished numbers of actinomycetes. Increasing dosages applied to soil artificially infested with S. rolfsii caused a reduction of disease on lentil, Lens culinaris. Results indicate that the compound, when applied to field soil, changes the composition of soil microflora and has potential for integrated control of S. rolfsii.