Characterization of a Novel Prevacuolar Compartment in Neurospora crassa

Using confocal microscopy, we observed ring-like organelles, similar in size to nuclei, in the hyphal tip of the filamentous fungus Neurospora crassa. These organelles contained a subset of vacuolar proteins. We hypothesize that they are novel prevacuolar compartments (PVCs). We examined the locations of several vacuolar enzymes and of fluorescent compounds that target the vacuole. Vacuolar membrane proteins, such as the vacuolar ATPase (VMA-1) and the polyphosphate polymerase (VTC-4), were observed in the PVCs. A pigment produced by adenine auxotrophs, used to visualize vacuoles, also accumulated in PVCs. Soluble enzymes of the vacuolar lumen, alkaline phosphatase and carboxypeptidase Y, were not observed in PVCs. The fluorescent molecule Oregon Green 488 carboxylic acid diacetate, succinimidyl ester (carboxy-DFFDA) accumulated in vacuoles and in a subset of PVCs, suggesting maturation of PVCs from the tip to distal regions. Three of the nine Rab GTPases in N. crassa, RAB-2, RAB-4, and RAB-7, localized to the PVCs. RAB-2 and RAB-4, which have similar amino acid sequences, are present in filamentous fungi but not in yeasts, and no function has previously been reported for these Rab GTPases in fungi. PVCs are highly pleomorphic, producing tubular projections that subsequently become detached. Dynein and dynactin formed globular clusters enclosed inside the lumen of PVCs. The size, structure, dynamic behavior, and protein composition of the PVCs appear to be significantly different from those of the well-studied prevacuolar compartment of yeasts.     

An “Ethnic” Arboretum

Part I of this three-part series deals generally with sound and its pollution. Part II will move on to measurement, effects, and indoor learning activities. Outdoor activities and references will make up Part III.     

Sodium balance in the catfish Clarias mossambicus exposed to acid water

African catfish, Clarias mossambicus showed no ill effects when kept in acid water pH 4–5 for 3–4 days. Their ionic regulatory response was examined and during 24 h exposure to water of pH 4, Na⁺ efflux increased significantly but was not matched by an increase in Na⁺ influx resulting in a substantial net loss of body Na⁺, which was reduced from 65.4 mmol · kg^?1 to 35.6 mmol · kg^?1, with smaller losses of Cl^? and K⁺.     

The reduction of ferryl myoglobin by ergothioneine: a novel function for ergothioneine

In this paper, we demonstrate that ergothioneine (ES), a naturally occurring thiolhistidine, reduces ferrylmyoglobin (MbIV) to MbIII when the former (ferryl species) is produced by exposing either deoxy MbII or MbIII to H2O2. The reduction of MbIV to MbIII by ES yields the disulfide of ES which the addition of GSH promptly reduces back to ES. The addition of ES (100 microM) in the perfusion buffer of Langendorff rat heart preparations exposed to a brief period of ischemia prevents the myocardial damage (lactate dehydrogenase release) which accompanies reperfusion. The results of these experiments support a view that ES and its redox couple GSH might function in a Mb redox cycle.     

Carbohydrate feeding and exercise: effect of beverage carbohydrate content

The purpose of this study was to determine the effect of ingesting fluids of varying carbohydrate content upon sensory response, physiologic function, and exercise performance during 1.25 h of intermittent cycling in a warm environment (Tdb = 33.4 degrees C). Twelve subjects (7 male, 5 female) completed four separate exercise sessions; each session consisted of three 20 min bouts of cycling at 65% VO2max, with each bout followed by 5 min rest. A timed cycling task (1200 pedal revolutions) completed each exercise session. Immediately prior to the first 20 min cycling bout and during each rest period, subjects consumed 2.5 ml.kg BW-1 of water placebo (WP), or solutions of 6%, 8%, or 10% sucrose with electrolytes (20 mmol.l-1 Na+, 3.2 mmol.l-1 K+). Beverages were administered in double blind, counterbalanced order. Mean (+/- SE) times for the 1200 cycling task differed significantly: WP = 13.62 +/- 0.33 min, *6% = 13.03 +/- 0.24 min, 8% = 13.30 +/- 0.25 min, 10% = 13.57 +/- 0.22 min (* = different from WP and 10%, P less than 0.05). Compared to WP, ingestion of the CHO beverages resulted in higher plasma glucose and insulin concentrations, and higher RER values during the final 20 min of exercise (P less than 0.05). Markers of physiologic function and sensory perception changed similarly throughout exercise; no differences were observed among subjects in response to beverage treatments for changes in plasma concentrations of lactate, sodium, potassium, for changes in plasma volume, plasma osmolality, rectal temperature, heart rate, oxygen uptake, rating of perceived exertion, or for indices of gastrointestinal distress, perceived thirst, and overall beverage acceptance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Assembly of the fertilization membrane of the sea urchin: Isolation of a divalent cation-dependent intermediate and its crosslinking in vitro

To analyze the mechanism of assembly of the fertilization membrane of the sea urchin Strongylocentrotus purpuratus, we inhibited the ovoperoxidase that catalyzes dityrosine formation to isolate an uncrosslinked, soft fertilization membrane (SFM). The SFM intermediates were stabilized by divalent cation-dependent interactions: in the absence of divalent cations, the SFM became amorphous and less refractile and released proteins into the surrounding medium. We term the remaining structures “wraiths.” The rate of this disaggregation was increased in solutions of low ionic strength, but 510 mM divalent cations (Ca²⁺, Mg²⁺, Mn²⁺ or Ba²⁺) prevented disaggregation. Wraiths could be reassembled into structures that resembled SFM by readdition of divalent cations. The SFM contained active ovoperoxidase and could be hardened in vitro by washing away the ovoperoxidase inhibitor and adding H₂O₂. After hardening, certain proteins of over 100 kd were excluded from SDS-polyacrylamide gels, suggesting that these proteins contain the substrates for crosslinking. We propose that the SFM is a divalent cation-dependent intermediate on the pathway of fertilization membrane assembly containing tyrosyl residues that are appropriately juxtaposed for crosslinking.     

Some novel aspects of the relationship between the amino acid gradient and the sodium electrochemical gradient in mouse ascites tumour cells

Accumulation of 2-aminoisobutyrate by mouse ascites tumour cells was studied in circumstances where nigericin reversed the normal direction of the Na+ concentration gradient. The membrane potential (delta psi) was assayed using oxonol V as a voltage-sensitive probe. The amino acid gradient (delta mu A) that formed did not significantly exceed the likely magnitude of the Na+ electrochemical gradient when this was in the range 2-6 kJ mol-1. When delta-Na mu increased up to 11 kJ mol-1, delta mu A was almost constant at 7-8 kJ mol-1. The observations indicate that when delta psi is large changes in cellular [Na+] in the range 16-80 mM scarcely affect delta mu A.     

The vegetation of the moor house national nature reserve in the northern Pennines,England

Summary The vegetation of a 40 km² area in northern England, ranging in altitude from 300 to 850 m, is described. Sheep graze the whole area and influence the composition of most vegetation types. Trees are absent. Blanket bog poor in species predominates and grassy communities on acidic ill-drained soils have considerable extent. There are also limestone outcrops which give rise to Agrosto-Festucetum on mineral soils and a variety of species-rich bryophytic and herbaceous cummunities in eutrophic flushes. An attempt has been made to relate the vegetation units to the classifications used in central Europe.

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Zusammenfassung Die Vegetation von einem 40 km² großen Gebiet in Nordengland, auf Höhen von 300 bis 850 m, wird beschrieben. Schafe grasen auf dem ganzen Gebiet und bestimmen die Zusammensetzung der meisten Vegetationstypen. Bäume sind nicht vorhanden. Artenarmes Hochmoor prädominiert und Gras-Gesellschaften auf saurem, schlecht-entwässertem Boden kommen in beträchtlichem Ausmaß vor. Es gibt auch an die Oberfläche tretenden Kalkstein, der das Entstehen von Agrosto-Festucetum auf Mineralboden veranlasst und eine Mannigfaltigkeit von Moos- und Krautgesellschaften, die darin auf eutrophem Torfboden vielerlei Arten haben. Ein Versuch ist gemacht worden, die Vegetationseinheiten in die in Mitteleuropa gebräuchlichen Klassifikationen einzuordnen.

     

An analysis of the sodium and chloride fluxes in the flounderPlatichthys flesus

Summary The sodium, potassium and chloride influxes and effluxes through the euryhaline flounderPlatichthys flesus are analysed into active and passive components. It is demonstrated that for any aquatic animal the energy required for osmotic regulation is minimal when the potential difference between the animal's body fluids and the medium is the same as the diffusion potential for the ions. This is illustrated by reference to the flounder.This work was supported by N.E.R.C. grant No.: GR/3/1515. We are grateful to the Lancashire and Western Sea Fisheries Committee for supplying the flounders.