Microhabitat preferences of benthic fauna in a woodland stream

Estimates of numbers, biomass, and diversity of benthic macroinvertebrates were made quarterly over a two-year period to investigate microhabitat preferences. Although biomass of most taxa was significantly different among sampling times, physical factors also appeared to be important in determining abundance of many taxa. Optimum depth, velocity, substrate type, and turbulence were determined for major taxa. Optimum conditions for diversity appeared to be 34 cm depth, 60 cm s^?1 velocity, and rubble and boulder substrate type. Habitat preference functions were derived for several taxa based on significant polynomial regressions of biomass on depth, velocity, substrate, and Froude number (turbulence). The relationship between abundance and physical habitat conditions was tested by using the product of the preference factors (range: 0–1) for depth, velocity and substrate type as a measure of habitat suitability (joint preference factor). There were significant correlations between biomass [transformed by log_e (x + 1)] of 10 benthic species and the joint preference factor. The joint preference factors accounted for from 11 to 61% of the variation of biomass of the 10 benthic species. The intercepts of the relationships between biomass of individual species and the joint preference factor were not significantly different from zero for any species. Therefore, the joint preference factors appear to be valid indicators of biomass. The preference functions have utility in habitat assessment studies, specifically with regard to minimum instream flow determinations.     

Microsporidiosis in a Daphnia pulex population

The impact of parasitism by Thelohania sp., an intracellular microsporidian, on Daphnia pulex inhabiting a vernal pond was studied for three years. Three issues were considered: the distribution of parasites among hosts, the effect of parasites on individuals, and the impact of parasitism on population growth. Each year, Thelohania infected members of at least half of the generations of Daphnia produced in the pond. When the frequency of infection was low, parasites were found only in large adults. As infection frequency increased, parasitism spread downward through host size classes. However, parasites were rarely found in juveniles. Parasitism reduced clutch size drastically, increased mortality to a variable extent, had little impact on egg size or on per instar growth and none on molt frequency. Interaction with other stresses, such as food limitation, exacerbated some of these effects. Parasitism reduced instantaneous birth rate much more than it elevated instantaneous death rate. Population growth was reduced significantly but it is unlikely that Thelohania alone regulates the growth of this Daphnia population.     

Receptor-like stereospecific binding of a pyrethroid insecticide to mouse brain membranes

A heterogeneous particulate fraction of mouse brain homogenates binds NRDC 157 (3-phenoxybenzyl [1$\text{R}$,$\text{cis}$]-3-(2,2-dibromovinyl)-2,2- dimethylcyclopropanecarboxylate), a potent pyrethroid insecticide, stereospecifically and with high affinity. Stereospecific binding is a minor component of total binding (2.8%); the remainder of observed binding is predominantly nonspecific and unsaturable. Stereospecific binding is half-saturated at 4×10^?8$\text{M}$ and fully saturated at concentrations in excess of 1×10^?7$\text{M}$. The stereospecific binding capacity of this preparation was 200–250 pmoles of NRDC 157 per gram equivalent of brain tissue (2.3–2.8 pmol/mg protein). This binding site may represent the neural receptor involved in the stereospecific toxic action of pyrethroids.     

Radioimmunoassay for quantitative determination of morphine in capsules of Papaver somniferum

A radioimmunoassay (RIA) procedure for the determination of pmol quantitites of morphine in capsule samples of Papaver somniferum was developed. An antiserum developed against a conjugate of morphine-3-hemisuccinate-BSA was relatively specific for morphine and possessed moderated cross-reactivity with codeine and mild cross-reactivity with thebaine, but none with narceine, papaverine, or noscapine. The standard curve was linear over a range of 0.01–0.20 ng. This assay allows for the rapid, sensitive and precise determination of morphine in unpurified aqueous extracts of capsule samples. The amounts of morphine in the aqueous extracts determined by radioimmunoassay were validated by high performance liquid chromatography (HPLC). The two methods show a high correlation coefficient (r = 0.98) with no significant difference in determinations of morphine content by RIA and HPLC.     

Intracellular pH and the cell cycle of mitogen-stimulated murine lymphocytes

Rapidly proliferating, polyclonally stimulated mouse spleen lymphocytes were separated by density-gradient unit-gravity sedimentation. The following measurements were made on each fraction: the average intracellular water volume, the distribution of DNA content by flow microfluorometry, the rate of ³H-thymidine incorporation, and the intracellular pH. Fractions of cells with a small average intracellular volume were predominately in G0 or G1 phase of the cell cycle, while fractions of larger cells had higher proportions of cells in S or G2. Multiple regression analysis of the data for both T and B lymphocytes indicated that the intracellular pH of cells in G0, G1, or G2 is around pH 7.2, and that the intracellular pH of cells in S phase of the cell cycle is around pH 7.4.     

Sequence interrelationships of the subunits of vicilin from pea seeds

Serological studies and comparison of N-terminal amino acid sequences with the amino acid sequence deduced from a cDNA clone have been used to establish the sequence relationships between the subunits of the pea seed storage protein, vicilin. Subunits smaller than M_r～50 000 (i.e., M_r 34 000, 30 000, 25 000, 18 000, 14 000, 13 000 and 12 000) show extensive homology with molecules within M_r～50 000 group. Both the sequencing and serological data confirm earlier evidence from studies on vicilin synthesisin vivo andin vitro which indicated that the vicilin subunits smaller than M_r～50 000 arose by endoproteolytic cleavage of parent molecules within the M_r～50 000 group. Cleavage in different M_r 50 000 parent molecules containing either one or both of two susceptible processing sites accounts for the formation of all the vicilin subunits smaller than M_r～50 000, with the possible exception of the M_r34 000 polypeptide. The position of these sites in the putative parents were defined by reference to a complete amino acid sequence deduced from the sequence of DNA complementary to mRNA for one member of the M_r～50 000 group.     

Linkage group VI of fish of the genus Xiphophorus (Poeciliidae): Assignment of genes coding for glutamine synthetase,uridine monophosphate kinase,and transferrin

Electrophoretic variation ascribable to three protein-coding loci, coding for glutamine synthetase (GS), uridine monophosphate kinase (UMPK), and transferrin (Tf), was observed in three species of fish of the genus Xiphophorus. Electrophoretic patterns in interspecific F1 hybrid heterozygotes suggested monomeric subunit structures of UMPK and Tf and a multimeric structure of undetermined subunit number of GS. Linkage analyses in backcross hybrids indicated a recombination map of GS-0%-Tf-10.8%-UMPK. This group (designated Xiphophorus linkage group VI) was shown to assort independently from the 14 enzyme loci assigned to linkage groups I-V and from 19 other informative markers within the limits of the data.     

Studies of the limited degradation of mucus glycoproteins. The effect of dilute hydrogen peroxide.

1. The action of dilute H2O2 on a series of ovarian-cyst glycoproteins and glycopolypeptides was investigated. 2. Both native glycoproteins and the glycopolypeptides were carbohydrate-rich, of relatively low molecular weight and of simple structure. 3. At pH 5.6 and 37 degrees C, exposure to H2O2 for a limited time brought about a partial degradation, the molecular weight being decreased by 2-4-fold. 4. Carbohydrate analysis showed very little change in the oligosaccharide moiety, apart from a small decrease in sialic acid in some samples. 5. Amino acid analysis showed minor changes in serine, threonine and proline contents, but almost total loss of histidine. Concomitantly, there was a small gain in aspartic acid. 6. Myosin, examined at both pH 5.7 and 6.7, exhibited generally similar behaviour, there being losses of other amino acid residues as well as histidine: the viscosity was decreased to a low value, and a range of peptides of widely varying size was produced. 7. It is suggested that attack on the histidine residue, with partial conversion into aspartic acid, is accompanied by scission of the histidyl peptide bond.     

HEMOPOIETIC STEM CELL PROLIFERATION AND MIGRATION FOLLOWING BORDETELLA PERTUSSIS VACCINE

The ability of a single injection of killed, intact bacteria to effect an increase in the proliferative rate of hemopoietic stem cells was studied. The total numbers of colony forming units in bone marrow, spleen and peripheral blood as well as the proportion of CFU in cycle was assessed. Splenic CFU were observed to rise exponentially due initially to in situ proliferation and later to proliferation in bone marrow with migration via the blood to the spleen. The results are discussed in the light of current concepts of stem cell regulation.