Fluoroaluminates mimic guanosine 5''-[gamma-thio]triphosphate in activating the polyphosphoinositide phosphodiesterase of hepatocyte membranes. Role for the guanine nucleotide regulatory protein Gp in signal transduction.

Fluoride and guanosine 5'-[gamma-thio]triphosphate (GTP gamma S) both activate the hepatocyte membrane polyphosphoinositide phosphodiesterase (PPI-pde) in a concentration-dependent manner. AlCl3 enhances the fluoride effect, supporting the concept that [A1F4]- is the active species. Analysis of the products of inositol lipid hydrolysis demonstrate that phosphatidylinositol bisphosphate is the major lipid to be hydrolysed. Guanosine 5'-[beta-thio]diphosphate (GDP beta S) is an inhibitor of activation of PPI-pde by both fluoride and GTP gamma S. These observations suggest that the guanine nucleotide regulatory protein (termed Gp) bears a structural resemblance to the well-characterized G-proteins of the adenylate cyclase system and the cyclic GMP phosphodiesterase system in phototransduction.     

Incidental capture of bottlenose dolphins (Tursiops truncatus) in shark nets: an assessment of some possible causes

A minimum of 250 bottlenose dolphins, Tursiops truncatus , was caught in anti-shark nets off Natal, South Africa between January 1980 and December 1988. Males and females constituted 45.4% and 54.6% of the catch, respectively. Sexually mature males and females constituted 18.2% and 24% of the total catch, respectively. Of the latter, 65% were lactating and a further 10.3% were pregnant. Adolescents, three or more years old but not mature, contributed 12.4% of the catch. Calves, two growth layer groups (GLGs) or less in the dentine, constituted the greatest portion of the catch, almost 43%, and of these almost 70% were either weaned or weaning at capture. Analyses of biological, environmental and physiographic data for each capture suggest a number of reasons for the catch of bottlenose dolphins. The distribution of catches was random but catch rates were proportional to the number of nets. The stomachs of most dolphins were almost full at the time of capture, suggesting that enmeshing occurred either during or subsequent to feeding. Most captures were of single animals, but lactating females with calves constituted more than 25% of catches. The direction of the prevailing current was significantly related to captures. These data are examined in relation to existing knowledge of bottlenose dolphins in this area and suggest that capture may be a consequence of prey abundance at and around the nets, dolphin capture occurring either during or directly after feeding. Possible methods of reducing captures are proposed.     

Lobar pneumonia caused by Mycoplasma pneumoniae.

Seven patients with Mycoplasma pneumoniae pneumonia presented with moderate to dense consolidation in one (in five patients) or more lobes. The diagnosis was suspected in five patients after failure to respond to 1 to 6 (average 2.6) antibiotics administered for 2 to 12 (average 7) days, and in one patient upon the development of hemolytic anemia. Clues to the diagnosis of nonbacterial pneumonia included a nonrespiratory viral-like prodromal period (in five), a nonproductive cough (in five), lack of rigors (in seven), recent "pneumonia" in family members (in ;three), normal total leukocyte and neutrophil counts (in six) and the absence of bacterial pathogens in smears and cultures of sputum (in all seven). The diagnosis of M. pneumoniae infection was supported by the presence of cold agglutinins (in a titre of 1.64 or greater) in ;the serum of five or six patients and was confirmed by diagnostic levels or increases in the titre of M. pneumoniae complement fixing antibodies. Awareness of the fact that M. pneumoniae can present as lobar consolidation and close attention to the clinical and laboratory data can usually suggest a nonbacterial cause and thus prevent delay in appropriate antibiotic treatment.     

Plasma-membrane location of phosphatidylinositol hydrolysis in rabbit neutrophils stimulated with formylmethionyl-leucylphenylalanine.

Rabbit peritoneal neutrophils, disrupted by sonication, were separated into three subcellular fractions by sucrose-step-gradient centrifugation and these were analysed with respect to biochemical markers. They comprised a high-speed supernatant containing the cytosol, a light particulate fraction enriched in Golgi and plasma membranes and a heavy particulate fraction enriched in granules and nuclei. The light particulate fraction was further separated into its components, which were identified as Golgi membranes (galactosyltransferase activity) and plasma membranes ((radioactivity derived from labelling intact cells with [125I]di-iodosulphanilic acid diazonium salt and [3H]formylmethionyl-leucylphenylalanine ([3H]fMet-Leu-Phe) binding)). In cells prelabelled with [3H]glycerol, the hydrolysis of phosphatidylinositol due to cell stimulation with fMet-Leu-Phe (10 nM) was shown to occur in the light particulate fraction. The [32P]Pi-labelling of phosphatidate, which is an early consequence of phosphatidylinositol hydrolysis, also occurred in this fraction. Analytical sucrose-gradient centrifugation of the light particulate fraction showed that the stimulated increment in [32P]phosphatidate (and thus by implication the initial phosphatidylinositol breakdown) was localized in the plasma membrane.     

Stimulation of phosphatidylinositol turnover in various tissues by cholinergic and adrenergic agonists, by histamine and by caerulein

Studies are reported of the biochemical and pharmacological characteristics of the stimulation of phosphatidylinositol metabolism that is produced in appropriate target tissues by stimulation of various receptors that use Ca(2+) as their second messenger. (1) Muscarinic cholinergic and alpha-adrenergic phosphatidylinositol responses were observed in rat lacrimal gland, and a response to caerulein was detected in the longitudinal smooth muscle of guinea-pig ileum. (2) The muscarinic cholinergic phosphatidylinositol response of rat lacrimal gland, like that of several other tissues, is not dependent on the availability of extracellular Ca(2+). (3) Three phosphatidylinositol responses, namely to histamine in guinea-pig ileum smooth muscle, to alpha-adrenergic stimulation in rat vas deferens and to muscarinic cholinergic stimulation in rat lacrimal gland, were all found to involve phosphatidylinositol breakdown. (4) The stereospecificity of the muscarinic receptor responsible for the phosphatidylinositol response of guinea-pig pancreas was tested by using the two stereoisomeric forms of acetyl-beta-methylcholine; the S-isomer was very much more active than the R-isomer in provoking both phosphatidylinositol breakdown and its labelling with (32)P, as it is in provoking other physiological responses such as contractility or secretion. (5) Pilocarpine, a muscarinic partial agonist, provoked a significantly smaller phosphatidylinositol breakdown in rat parotid fragments than did carbamoylcholine, a potent muscarinic agonist. (6) All of these results are consistent with, but do not prove, a previously offered hypothesis that suggests that phosphatidylinositol breakdown is a reaction essential to stimulus-response coupling at a variety of cell-surface receptors that mobilize Ca(2+) from and through the plasma membranes of target tissues.