Localization of vimentin,the nonspecific intermediate filament protein,in embryonal glia and in early differentiating neurons: In vivo and in vitro immunofluorescence study of the rat embryo with vimentin and neurofilament antisera

Antisera raised against vimentin, the protein subunit of nonspecific intermediate-sized filaments (IFs), were used in conjunction with neurofilament (NF) antisera to study the early development of neurons and glia in the rat embryo. Vimentin-positive fibers spanning the entire thickness of the neural tube including the cerebral vesicles were first observed on Day 12, concomitant with the appearance of NF protein in more confined areas (anterolateral regions of spinal cord and brain stem; motor roots emerging from the NF-positive areas). From Day 15 onwards vimentin and NF antisera selectively decorated glia and neurons, respectively, both in vivo and in vitro. Before Day 15 it appeared that NF-positive structures also stained with antivimentin in cryostat sections. In vitro experiments confirmed the presence of vimentin in early differentiating neurons. NF-positive cells were observed which also reacted with antivimentin in cultures obtained from 13- and 14-day embryos, but not later in development. Most neurons in these cultures became vimentin negative after 2–3 days in vitro.     

The organization of the gene for the human cerebroside sulfate activator protein

The organization of 14 exons covering 97% of the cDNA sequence of human cerebroside sulfate activator protein precursor has been determined from two overlapping EMBL-4 human genomic clones extending over 17kb. All exons and exon/intron splice junctions and five introns were sequenced. Exon 8 consists of only 9 bp and is involved in alternative splicing which generates three different mRNAs of cerebroside sulfate activator precursor.     

Regional and local variability in recovery of shallow coral communities: Moorea,French Polynesia and central Great Barrier Reef

Coral communities at Moorea, French Polynesia, and on the Great Barrier Reef (GBR), Australia, were severely depleted by disturbances early in the 1980s. Corals were killed by the predatory starfish Acanthaster planci, by cyclones, and/or by depressed sea level. This study compares benthic community structure and coral population structures on three disturbed reefs (Vaipahu-Moorea; Rib and John Brewer Reefs-GBR) and one undisturbed reef (Davies Reef-GBR) in 1987–89. Moorea barrier reefs had been invaded by tall macrophytes Turbinaria ornata and Sargassum sp., whereas the damaged GBR reefs were colonised by a diverse mixture of short macrophytes, turfs and coralline algae. The disturbed areas had broadly similar patterns of living and dead standing coral, and similar progress in recolonisation, which suggests their structure may converge towards that of undisturbed Davies Reef. Corals occupying denuded areas at Vaipahu, Rib and John Brewer were small (median diameter 5 cm in each case) and sparse (means 4–8 m^-2) compared to longer established corals at Davies Reef (median diameter 9 cm; mean 18 m^-2). At Moorea, damselfish and sea urchins interacted with corals in ways not observed in the GBR reefs. Territories of the damselfish Stegastes nigricans covered much of Moorea's shallow reef top. They had significantly higher diversity and density of post-disturbance corals than areas outside of territories, suggesting that the damselfish exerts some influences on coral community dynamics. Sea urchins on Moorea (Diadema setosum Echinometra mathaei, Echinotrix calamaris) were causing widespread destruction of dead standing coral skeletons. Overall, it appears that the future direction and speed of change in the communities will be explicable more in terms of local than regional processes.     

Base-pair probability profiles of RNA secondary structures

Dynamic programming algorithms are able to predict optimal andsuboptimal secondary structures of RNA. These suboptimal oralternative secondary structures are important for the biologicalfunction of RNA. The distribution of secondary structures presentin solution is governed by the thermodynamic equilibrium betweenthe different structures. An algorithm is presented which approximatesthe total partition function by a Boltzmann–weighted summationof optimal and suboptimal secondary structures at several temperatures.A clear representation of the equilibrium distribution of secondarystructures is derived from a two-dimensional bonding matrixwith base–pairing probability as the third dimension.The temperature dependence of the equilibrium distribution givesthe denaturation behavior of the nucleic acid, which may becompared to experimental optical denaturation curves after correctionfor the hypochromicities of the different base-pairs. Similarly,temperature-induced mobility changes detected in temperature-gradientgel electrophoresis of nucleic acids may be interpreted on thebasis of the temperature dependence of the equilibrium distribution.Results are illustrated for natural circular and synthetic linearpotato spindle tuber viroid RNA respectively, and are comparedto experimental data.     

Effects of melatonin injections on the ability of golden hamster pituitaries to secrete prolactin and luteinizing hormone

Chronic afternoon (PM) but not morning injections of melatonin (MEL) induced significant reductions in testicular and seminal vesicle weights as well as attenuating serum prolactin (PRL) and luteinizing hormone (LH) levels. Although there were no treatment-induced effects on hemipituitary weights, PM-Mel injections led to significant reductions in in vitro PRL secretion and tended to increase the ability of dopamine to inhibit PRL release. It was also shown that LH-releasing hormone (LHRH) could inhibit in vitro PRL release from hamster pituitaries. Basal or LHRH-stimulated LH secretion from incubated pituitaries was not affected by Mel in vivo. From these results we conclude that properly timed Mel injections do not reduce pituitary's ability to secrete LH but severely attenuate PRL secretion. These findings are similar to those observed in pituitaries from hamsters housed in short-photoperiod conditions.