The reproductive biology of Gerres in Natal estuaries

An investigation of the reproductive state and gonad development of Gerreidae in Natal showed that the fry of Gerres rappi, G. acinaces and G. filamentosus entered estuaries at 10 mm (s.l.). They stayed in the estuary until attainment of maturity, which was between 70 and 110 mm according to species. Gonad activity was initiated in estuaries but all females left before their eggs were ripe. Testes ripened while the fish were still in the estuary but no ripe running individuals were found. Since few large and no spent individuals occurred in the estuaries sampled, it appears that most fish do not return from the sea. Sequence of oocyte maturation and testes development were determined histologically. The estuarine area may be of importance to the fry as a safe nursery ground and to maturing individuals as an environment in which gonad maturity is reached for the first time.     

Studies on catechol-O-methyltransferase in rat brain using two-dimensional gel electrophoresis

The presence of catechol-O-methyltransferase (COMT) in the rat brain was studied using a combination of two-dimensional gel electrophoresis (2-DE), protein blotting and a specific antiserum. Two major immunoreactive proteins were identified—one with mol. wt 23 kdalton and an isoelectric point of 5.2, the other of mol. wt 25 kdalton and an isoelectric point of 5.1. In addition, multiple lower molecular weight immunoreactive proteins, possibly corresponding to breakdown products of the enzyme, were also detected. The 23 kdalton form of COMT, which is probably the soluble form of the enzyme, is a major protein visible on silver-stained 2-D gels of rat brain. In contrast, the other proteins recognized by the antiserum were not detected by the silver stain. These results demonstrate, using 2-DE, that at least two distinct forms of catechol-O-methyltransferase are present in rat brain. In addition, since one of these proteins is stained by silver, these results also serve to identify another protein visible on 2-D electrophoretograms of rat brain.     

Release of norepinephrine from brain vesicular preparations: Effects of an adenylate cyclase activator,forskolin, and a phosphodiesterase inhibitor

1. The calcium-dependent K+-evoked release of [3H]norepinephrine from guinea pig cerebral cortical vesicular preparations is inhibited by norepinephrine, clonidine, and epinephrine. Isoproterenol has no effect and phentolamine prevents the inhibition by norepinephrine. The results indicate that an alpha-adrenergic receptor mediates an inhibitory input to the calcium-dependent release process. The inhibition by norepinephrine is prevented by high concentrations (3.0 mM) of calcium ions. 2. A cyclic AMP phosphodiesterase inhibitor, ZK 62771, slightly elevates [3H]cyclic AMP levels in the guinea pig cerebral cortical preparation and potentiates the marked elevation of [3H]cyclic AMP elicited by the adenylate cyclase activator, forskolin. 3. Neither ZK 62771 nor forskolin alone has significant effects on K+-evoked release of [3H]norepinephrine from the cerebral cortical vesicular preparation; however, a combination of ZK 62771 and forskolin inhibits K+-evoked release by as much as 60%. The inhibition is reversed by high concentrations (2.0 mM) of calcium ions. The results suggest that a marked accumulation of cyclic AMP elicited via both activation of adenylate cyclase and inhibition of phosphodiesterase can be inhibitory to neurotransmitter release from central synaptic terminals.     

Circadian variations of “synaptic” bodies in the pineal glands of Brattleboro rats

Summary The function of the mammalian pincal gland is regulated primarily by the sympathetic system. Arginine-vasopressin (AVP) may also be involved in the regulation of pineal melatonin synthesis under experimental conditions. The present study was conducted in the AVP-deficient rat strain, the Brattleboro rat, to investigate whether the numbers and rhythms of pineal synaptic bodies in this strain are different from those found in intact rats. AVP or its non-vasoconstrictive analog, deamino-D-AVP, was also injected intra-arterially in Brattleboro or Sprague-Dawley rats to test whether this procedure influences synaptic body numbers. Brattleboro rats were killed at different timepoints throughout the 24 h-cycle in March, June and September. Synaptic ribbons, spherules and intermediate structures were quantified and examined with regard to their intracellular location, with or without nocturnal AVP or D-AVP treatment. Numbers of ribbons were low during the day and high during the night (as in genetically intact rats), whereas spherules and intermediate structures numbers exhibited inconstant daily patterns. Night levels of synaptic ribbons were highest in June, lowest in March, whereas day levels did not differ significantly. No significant alterations in pineal synaptic body numbers were found following administration of AVP or D-AVP. Our results therefore indicate that AVP does not play a crucial role in the regulation of pineal synaptic body numbers in rats.     

Small-molecule metabolism: an enzyme mosaic

Escherichia coli has been a popular organism for studying metabolic pathways. In an attempt to find out more about how these pathways are constructed, the enzymes were analysed by defining their protein domains. Structural assignments and sequence comparisons were used to show that 213 domain families constitute 90% of the enzymes in the small-molecule metabolic pathways. Catalytic or cofactor-binding properties between family members are often conserved, while recognition of the main substrate with change in catalytic mechanism is only observed in a few cases of consecutive enzymes in a pathway. Recruitment of domains across pathways is very common, but there is little regularity in the pattern of domains in metabolic pathways. This is analogous to a mosaic in which a stone of a certain colour is selected to fill a position in the picture.     

Regulation of p27Kip1 during gentamicin mediated hair cell death

The INK4 and Kip/Cip families of Cyclin Dependent Kinase inhibitors (CKIs) are regulators of the cell cycle. In addition, CKIS including p27^Kip1can protect cells from apoptosis in vitro. However, little is known about protective effect of p27^Kip1in vivo. We used systemic treatment with aminoglycosides to induce hair-cell death in the basilar papilla (BP), the auditory organ of the avian inner ear, and characterised the expression of p27^Kip1with confocal and immunofluorescence microscopy. In contrast to the adult mammalian cochlea where p27^Kip1is expressed only in supporting cells, p27^Kip1is found in the nuclei of both hair cells and supporting cells in the BP of the normal, mature bird. Forty-eight hours after gentamicin treatment, hair cells with TUNEL positive nuclei and hair cells with pyknotic nuclei were both detected, suggesting many hair cells die by apoptosis. When the BP was double labelled for p27^Kip1and myosin VIIa, a hair-cell specific protein, all dying hair cells that had been ejected from the epithelium were found to be myosin VIIa positive but negative for p27^Kip1even though nuclear remnants were still visible. In the transition zone where partial hair-cell loss occurs, freshly ejected hair cells lying immediately above the surface of the BP no longer expressed p27^Kip1. Damaged hair cells within the epithelium in the transition zone contained p27^Kip1in their cytoplasm but not in their nuclei. These data support recent in vitro findings suggesting that p27^Kip1protects cells from apoptosis and that its downregulation may be a general feature of programmed cell death.     

New multivalent cationic lipids reveal bell curve for transfection efficiency versus membrane charge density: lipid-DNA complexes for gene delivery

BACKGROUND: Gene carriers based on lipids or polymers-rather than on engineered viruses-constitute the latest technique for delivering genes into cells for gene therapy. Cationic liposome-DNA (CL-DNA) complexes have emerged as leading nonviral vectors in worldwide gene therapy clinical trials. To arrive at therapeutic dosages, however, their efficiency requires substantial further improvement. METHODS: Newly synthesized multivalent lipids (MVLs) enable control of headgroup charge and size. Complexes comprised of MVLs and DNA have been characterized by X-ray diffraction and ethidium bromide displacement assays. Their transfection efficiency (TE) in L-cells was measured with a luciferase assay. RESULTS: Plots of TE versus the membrane charge density (sigmaM, average charge/unit area of membrane) for the MVLs and monovalent 2,3-dioleyloxypropyltrimethylammonium chloride (DOTAP) merge onto a universal, bell-shaped curve. This bell curve leads to the identification of three distinct regimes, related to interactions between complexes and cells: at low sigmaM, TE increases with increasing sigmaM; at intermediate sigmaM, TE exhibits saturated behavior; and unexpectedly, at high sigmaM, TE decreases with increasing sigmaM. CONCLUSIONS: Complexes with low sigmaM remain trapped in the endosome. In the high sigmaM regime, accessible for the first time with the new MVLs, complexes escape by overcoming a kinetic barrier to fusion with the endosomal membrane (activated fusion), yet they exhibit a reduced level of efficiency, presumably due to the inability of the DNA to dissociate from the highly charged membranes in the cytosol. The intermediate, optimal regime reflects a compromise between the opposing demands on sigmaM for endosomal escape and dissociation in the cytosol.     

Individual differences among grapheme-color synesthetes: brain-behavior correlations

Grapheme-color synesthetes experience specific colors associated with specific number or letter characters. To determine the neural locus of this condition, we compared behavioral and fMRI responses in six grapheme-color synesthetes to control subjects. In our behavioral experiments, we found that a subject's synesthetic experience can aid in texture segregation (experiment 1) and reduce the effects of crowding (experiment 2). For synesthetes, graphemes produced larger fMRI responses in color-selective area human V4 than for control subjects (experiment 3). Importantly, we found a correlation within subjects between the behavioral and fMRI results; subjects with better performance on the behavioral experiments showed larger fMRI responses in early retinotopic visual areas (V1, V2, V3, and hV4). These results suggest that grapheme-color synesthesia is the result of cross-activation between grapheme-selective and color-selective brain areas. The correlation between the behavioral and fMRI results suggests that grapheme-color synesthetes may constitute a heterogeneous group.