Operculum closing as a defence against predatory leeches in four British freshwater prosobranch snails

The defence reaction of operculum closing in response to the presence of the molluscivorous leech Glossiphonia complanata (L.) and the non-molluscivorous Erpobdella octoculata (L.) was studied in four species of freshwater prosobranch gastropod. Bithynia tentaculata (L.) and Valvata piscinalis (Müller) can distinguish between the leeches, reacting only to G. complanata. V. piscinalis is capable of a greater degree of distance chemoreception of the leech ‘scent’. Valvata cristata Müller and Potamopyrgus jenkinsi (Smith) did not react to either leech. V. cristata may not be a potential prey item for G. complanata, while P. jenkinsi is fed on by the leech, but is a relative newcomer to the freshwater fauna. Animal Ecology Research Group, Department of Zoology, University of Oxford Commonwealth Forestry Institute, Department of Plant Sciences, University of Oxford     

Calcium and proton activities in rat cardiac mitochondria. Effect of matrix environment on behaviour of fluorescent probes.

The ionic composition of the mitochondrial matrix, under both physiological and pathophysiological conditions, remains controversial. Although fura-2 and 2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF), fluorescent probes for [Ca2+] and [H+] respectively, have successfully been loaded into mitochondria [Lukács & Kapus (1987) Biochem. J. 248, 609-613; Davis, Altschuld, Jung & Brierley (1987) Biochem. Biophys. Res. Commun. 49, 40-45], the adaptation of fluorescence-ratio spectroscopy to the study of the matrix ion content poses unique problems. In this report, we describe a method for successfully attaching viable rat cardiac mitochondria to glass coverslips, allowing continuous superfusion of isolated organelles during fluorescence microscopy. This technique obviated the need to correct for the accumulation of ion-sensitive and -insensitive fluorescent species of dye both within the matrix and outside of mitochondria in suspension in a cuvette, a particular problem with fura-2. By using this technique for superfusion of immobilized mitochondria, we found the pKa of BCECF for H+ at 25 degrees C shifted from 6.8 in buffer to 7.2 in rat cardiac mitochondria, with a marked hysteresis effect noted for intramitochondrial BCECF calibration curves. At higher pH, photobleaching of BCECF was enhanced. The dissociation constant (Kd) of fura-2 for Ca2+ was found to be 315 nM at 25 degrees C, pH 8.0, but only at [Ca2+] below 1 microM. At matrix [Ca2+] greater than 1 microM, the Kd shifted into the micromolar range, an effect that appeared to be pH-dependent. Importantly, the matrix [Ca2+] was determined to be between 10 and 100 nM at perfusion buffer [Ca2+] below 500 nM, but rose rapidly at the higher extramitochondrial [Ca2+] reported to occur in ischaemic cardiac myocytes. Importantly, mitochondrial transmembrane H+ and Ca2+ gradients both appeared to be maximal at perfusion buffer [H+] and [Ca2+] that approximate those of the cytosol of many resting cells.     

The receptors for prolactin and growth hormone are localized in the same region of human chromosome 5

Prolactin receptor (PRLR) and growth hormone receptor (GHR) are encoded by members of a gene family containing regions of identical sequences. To determine their chromosomal locations, cDNA probes for these genes were used. Analysis of hybridization to several somatic cell hybrids, together with hybridization in situ to metaphase chromosomes, resulted in the assignment of the loci for both receptors to human chromosome 5 in the region p13----p14. Thus, these proteins may be encoded by a cluster of related genes that evolved from a common ancestral gene, in a manner consonant with that of their ligands.     

A novel extracellular carbohydrase produced by Lipomyces tetrasporus

Summary The ascosporogenous yeast Lipomyces tetrasporus produced an unusual extracellular carbohydrase. It was purified to homogeneity using ammonium sulphate precipitation and DEAE Bio-gel A ion-exchange chromatography. While retaining highest activity on low-molecular-weight saccharides such as maltose and nigerose, it displays considerable activity towards polymeric substrates including soluble starch. It is particularly unusual in that it also hydrolyses dextran and has a very high affinity for this substrate. The enzyme has an exo-lytic mode of action with the only hydrolysis product, glucose, being released in the -anomeric form. Optimum activity occurs at pH 4.5 and at 50°C. It is a glycoprotein, and has an M _r value of 150 000 (sodium dodecyl sulphate-polyacrylamide gel electrophoresis) — 183 000 (fast protein liquid chromatography) and a pI of 6.0. Offprint requests to: C. T. Kelly     

Dietary effects on hematologic and serum chemical values in gray short-tailed opossums (Monodelphis domestica)

At the time of weaning (8 weeks), 57 gray short-tailed opossums (Monodelphis domestica) were placed in four dietary groups. One group was fed a horsemeat-based diet that had been used for 2.5 years in our colony, and three groups were fed three different commercial fox food diets. After the animals had reached sexual maturity (6 months), blood samples were collected and subjected to standard hematologic and serum chemical assays. Significant differences were observed among the dietary groups and between sexes in several values, but all animals appeared to be healthy and robust. The ranges, means, and standard deviations for the values presented here can be used as reference values for healthy young adult animals being fed these particular diets.     

Local names for vascular plants in the John Crow mountains,Jamaica

Local names of vascular plants, accompanied by botanical specimens, were collected in the John Crow Mountains, Portland Parish, Jamaica. Each of the names was volunteered by one local informant; many were independently corroborated by others. We recorded 91 names of forest trees and shrubs, 20 names of climbers, and 33 names of other plants. The uneven distribution of local names among different categories of plants is discussed. The names are mostly of English origin, with a scattering from Spanish, Amerindian and West African languages. Many names are not listed in the standard floras; 20 names are apparently hitherto unrecorded in print. The same name was often found to be applied to a different species from the usage given in the floras, showing the variation in vernacular names from one part of the island to another.     

Schistosoma mansoni: complexity of antigenic and nonantigenic surface polypeptides

Two-dimensional gel analysis of the surface polypeptides of the schistosomula stage of Schistosoma mansoni resolved a complex pattern of approximately 20 polypeptides. The majority of these were identified as immunogenic since they were immunoprecipitated with antisera from chronically infected mice and from mice vaccinated with irradiated cercariae. However, several major surface polypeptides were not immunoprecipitated by sera from infected or immune mice and were presumed to be nonantigenic.     

Analysis of the direct effects of prostaglandins on human sperm function

Time-exposure photomicrography and interspecies in-vitro fertilization procedures have been used to examine the influence of prostaglandins on human sperm function. An analysis of variance indicated that the presence of PGs in the incubation media was associated with a significant increase in sperm velocity and the frequency of sperm head rotation, although there were no differences between individual PGs in the degree of stimulation observed. Changes in the penetrating ability of human spermatozoa were detected after exposure to PGs, particularly PGE-1 and PGE-2. PGE-2 induced a sustained increase in penetration rates at all doses of greater than 8.4 micrograms/ml, while exposure to PGE-1 gave a bell-shaped dose-response curve which exhibited a peak between 8.4 and 33.3 micrograms/ml and progressively fell to reach control levels at the maximum concentration tested of 270 micrograms/ml. A combination of PGE-2 and PGE-1 produced a dose-response curve similar to that for PGE-1 alone, while exposure to PGF-2 alpha was without effect. Seminal extracts containing predominantly 19-hydroxy PGE-1, or equal amounts of 19-hydroxy PGE-1 + 2 induced a slight, but significant, rise in penetration rates while a combination of PGs representing the major components of human seminal plasma was without significant effect. We conclude that certain prostaglandins may have a direct action on the functional competence of human spermatozoa.     

A highly antigenic proteoglycan-like component of cholinergic synaptic vesicles

A monoclonal antibody, tor70, recognizes an antigenic determinant on the inside surface of synaptic vesicles, purified from the electric organ of Narcine brasiliensis. The antigenic determinant appears to be unique to vesicles since it co-purifies with vesicle content and is blocked by an antiserum specific for synaptic vesicle antigens. Immunoblotting of vesicle proteins after sodium dodecyl sulfate-polyacrylamide gel electrophoresis shows that the antigen has a low heterogeneous electrophoretic mobility and corresponds to a major protein component of pure synaptic vesicles. Synaptic vesicles contain a proteoglycan-like material since proteolytic digestion yields a ruthenium red-binding material that migrates during electrophoresis with a mammalian heparin standard. The only major vesicle component with which the proteoglycan-like material co-elutes during chromatography on Sepharose 6B is the material recognized by tor70. The antigen adsorbs specifically to beads coated with the lectin wheat germ agglutinin. Isolation of the tor70 antigen by velocity sedimentation in sodium dodecyl sulfate-sucrose gradients shows it to contain glucosamine (0.75 nmol/microgram of protein) and uronic acid but no galactosamine. Earlier work has shown that specific antiserum to pure synaptic vesicles could be used to identify nerve terminals, quantitate vesicle components, purify membranes, and monitor exocytosis. We now know that one of the components recognized by the antiserum is a molecule with properties of a proteoglycan, attached to the inside surface of vesicle membranes.