Fusion pore in live cells.

Earlier electrophysiological measurements on live secretory cells suggested the presence of fusion pores at the plasma membrane, where secretory vesicles fuse to release vesicular contents. Recent studies using atomic force microscopy demonstrate for the first time the presence of the fusion pore and reveal its morphology and dynamics at near-nanometer resolution and in real time.

SNAREs in opposing bilayers interact in a circular array to form conducting pores.

The process of fusion at the nerve terminal is mediated via a specialized set of proteins in the synaptic vesicles and the presynaptic membrane. Three soluble N-ethylmaleimide-sensitive factor (NSF)-attachment protein receptors (SNAREs) have been implicated in membrane fusion. The structure and arrangement of these SNAREs associated with lipid bilayers were examined using atomic force microscopy.

G(alpha)(i3) in pancreatic zymogen granules participates in vesicular fusion.

Earlier studies indicated that a G(i)-like protein localized in pancreatic zymogen granule (ZG) membrane mediates vesicle swelling, and is a potentially important prerequisite for vesicle fusion at the cell plasma membrane (PM) [Jena et al. (1997) Proc. Natl.

Organic acids from leaves, fruits, and rinds of Garcinia cowa.

Organic acids in fresh leaves, fruits, and dried rinds of Garcinia cowa (G. cowa) were determined by high-performance liquid chromatography. Fresh leaves, fruits, and dried rinds were extracted with water at 120 degrees C for 20-30 min under 15 lbs/in(2) pressure.

Aquaporin 1 regulates GTP-induced rapid gating of water in secretory vesicles.

The swelling of secretory vesicles has been implicated in exocytosis, but the underlying mechanism of vesicle swelling remains largely unknown. Zymogen granules (ZGs), the membrane-bound secretory vesicles in exocrine pancreas, swell in response to GTP mediated by a G(alpha)i3 protein. Evidence is presented here that the water channel aquaporin-1 (AQP1) is present in the ZG membrane and participates in rapid GTP-induced vesicular water gating and swelling.

Structure and dynamics of the fusion pores in live GH-secreting cells revealed using atomic force microscopy.

Earlier studies in live pancreatic acinar cells identified new cellular structures at the cell plasma membrane called 'pits' and 'depressions', where membrane-bound secretory vesicles dock and fuse to release vesicular contents. In the current study, using atomic force microscopy we identify similar structures at the plasma membrane of GH-secreting cells of the pituitary and implicate their involvement in hormone release. Pits containing 100-200 nm in diameter depressions or fusion pores were identified in resting GH-secreting cells.

Age-related effect of aluminium on the catalase activities of the brains of two species of poikilothermic vertebrates.

Background: Although aluminium (Al) has been implicated in various neuropathological states with aging due to its involvement in neurotoxicity, the exact role of the metal ion is still unclear.

Objective: The aim of the present study is to ascertain whether the antioxidant enzymes of the brain protecting from oxidative damages which accumulate with aging are regulated by Al in an age-dependent manner.

Method: The inhibitory effect of Al on the catalase activity of brain homogenates of two species of poikilothermic vertebrates was studied in vitro using a spectrophotometric method.

Structure and dynamics of the fusion pore in live cells.

Atomic force microscopy reveal pit-like structures typically containing three or four, approximately 150 nm in diameter depressions at the apical plasma membrane in live pancreatic acinar cells. Stimulation of secretion causes these depressions to dilate and return to their resting size following completion of the process. Exposure of acinar cells to cytochalasin B results in decreased depression size and a loss in stimulable secretion.

The number of secretory vesicles remains unchanged following exocytosis.

Earlier studies using electron microscopy demonstrate that there is no loss of secretory vesicles following exocytosis. Depletion however, of vesicular contents resulting in the formation of empty or partially empty vesicles is seen in electron micrographs, post exocytosis, in a variety of cells. Our studies using atomic force microscopy (AFM) reveal that following stimulation of secretion, live pancreatic acinar cells having 100-180 nm in diameter fusion pores located at the apical plasma membrane, dilate only 25-35% during exocytosis.

Chemistry and biochemistry of (-)-hydroxycitric acid from Garcinia.

(-)-Hydroxycitric acid [(-)-HCA] is the principal acid of fruit rinds of Garcinia cambogia, Garcinia indica, and Garcinia atroviridis. (-)-HCA was shown to be a potent inhibitor of ATP citrate lyase (EC 4.1.

Impaired hepatocyte glucose transport protein (GLUT2) internalization in chronic pancreatitis.

Chronic pancreatitis (CP) is associated with impaired glucose tolerance and with reduced hepatic sensitivity to insulin. We have previously shown that in normal and sham-operated rats, insulin suppresses hepatic glucose production, and this suppression is associated with a decrease in the hepatocyte plasma membrane-bound quantity of the facilitative glucose transport protein GLUT2. The insulin-mediated reduction in membrane-bound GLUT2 is impaired in CP, and may play a role in the glucose intolerance associated with CP.

Insights on membrane fusion.

Membrane fusion is a fundamental cellular process regulating intracellular transport, neurotransmission, enzyme secretion, hormone release, and the entry/exit of viruses, to name a few. Knowledge of how opposing bilayers fuse, besides advancing our understanding of these cellular processes, will provide us with the facts to ameliorate secretory defects and prevent cellular entry or exit of pathogenic viruses. In the last few years, great strides have been made in our understanding of the molecular machinery and mechanism of membrane fusion.

Effect of age on lipid peroxides, lipofuscin and ascorbic acid contents of the lungs of male garden lizard.

Oxidative damage was assessed through the estimation of lipid peroxides (LP) in the lungs of an ageing short-lived species of reptile, Calotes versicolor, commonly known as the garden lizard. Attempts were also made to trace its relationship with the age pigment, lipofuscin and the antioxidant ascorbic acid. While LP increased with advancing age the contents of both lipofuscin and ascorbic acid did not show appreciable change during maturation ( < 1-1 year old) but declined during senescence phase (1 to 2-4 year old).

Continuous detection of extracellular ATP on living cells by using atomic force microscopy.

Atomic force microscopy is a powerful technique used to investigate the surface of living cells under physiological conditions. The resolution of the instrument is mainly limited by the softness of living cells and the interactions with the scanning tip (cantilever). Atomic force microscopy, in combination with myosin-functionalized cantilevers, was used in the detection of ATP concentrations in solution and on living cells.

The native membrane fusion machinery in cells.

Recombinant SNAREs have been demonstrated as the minimal membrane fusion machinery. The participation of additional proteins in the regulation of membrane fusion has been suggested. In this study we provide nanometer-resolution images of native NSF oligomers and SNARE complexes isolated from neurons and the pancreas.

Binding contribution between synaptic vesicle membrane and plasma membrane proteins in neurons: an AFM study.

The final step in the exocytotic process is the docking and fusion of membrane-bound secretory vesicles at the cell plasma membrane. This docking and fusion is brought about by several participating vesicle membrane, plasma membrane and soluble cytosolic proteins. A clear understanding of the interactions between these participating proteins giving rise to vesicle docking and fusion is essential.

Effects of age and manganese (II) chloride on peroxidase activity of brain and liver of the teleost, Channa punctatus.

Fish provide enormous spectrum of longevity and thus present the possibility of multiple mechanisms of senescence. Oxidative stress as a causative agent of senescence and the protective role of antioxidant enzymes were tested in the teleost, Channa punctatus taking peroxidase (POD) (EC 1.1 1.

Rapid aldosterone-induced cell volume increase of endothelial cells measured by the atomic force microscope.

Atomic force microscopy (AFM) is a useful technique for imaging the surface of living cells in three dimensions. The authors applied AFM to obtain morphological information of individual cultured endothelial cells of bovine aorta under stationary and strain conditions and to simultaneously measure changes in cell volume in response to aldosterone. This mineralocorticoid hormone is known to have acute, non-genomic effects on intracellular pH, intracellular electrolytes and inositol-1,4,5-triphosphate production.

Gi regulation of secretory vesicle swelling examined by atomic force microscopy.

In the last decade, several monomeric and heterotrimeric guanine nucleotide binding proteins have been identified to associate with secretory vesicles and to be implicated in exocytosis. Vesicle volume also has been proposed to play a regulatory role in secretory vesicle fusion at the plasma membrane. However, the molecular mechanism of function of the guanine nucleotide binding proteins and of the regulation of secretory vesicle volume in the exocytotic process remains unclear.

Localization of SH-PTP1 to synaptic vesicles: a possible role in neurotransmission.

The tyrosine kinase pp60src is known to phosphorylate synaptophysin and in doing so may regulate neurotransmitter release. The tyrosyl phosphorylated state of synaptophysin is dependent on pp60src kinase and the unknown protein tyrosine phosphate phosphohydrolase (PTPase, EC 3.1.

Surface dynamics in living acinar cells imaged by atomic force microscopy: identification of plasma membrane structures involved in exocytosis.

The dynamics at the plasma membrane resulting from secretory vesicle docking and fusion and compensatory endocytosis has been difficult to observe in living cells primarily due to limited resolution at the light microscopic level. Using the atomic force microscope, we have been able to image and record changes in plasma membrane structure at ultrahigh resolution after stimulation of secretion from isolated pancreatic acinar cells. "Pits" measuring 500-2000 nm and containing 3-20 depressions measuring 100-180 nm in diameter were observed only at the apical region of acinar cells.

Age related modifications of soluble proteins in various organs of male garden lizard, Calotes versicolor.

The oxidative modification of proteins measured as carbonyl derivatives increased with advancing age in the liver of male garden lizard. The same parameter did not show a significant change in other organs (brain, heart and kidney). Based on the observations in both homeotherms (mammals) and poikilotherms (insect and reptile), the in vivo oxidative modification of cellular proteins appears to be the most common mechanism leading to accumulation of altered proteins during aging.