Hemocyanin of the horseshoe crab, Limulus polyphemus. Structural differentiation of the isolated components.

The high molecular weight hemocyanin found in the hemolymph of the horseshoe crab, Limulus polyphemus, is composed of at least eight different kinds of subunits. Ion exchange chromatography at high pH in the presence of EDTA yields five major zones, hemocyanins I to V, three of which are electrophoretically heterogeneous. The subunits have similar molecular weights, 65,000 to 70,000, and their amino acid compositions are remarkably similar to each other and to other arthropod and molluscan hemocyanins. Digestion of the native subunits of Limulus hemocyanin by formic acid or trypsin shows considerable structural diversity which is supported by cyanogen bromide cleavage patterns and by peptide mapping of the tryptic peptides prepared from denatured hemocyanin subunits. The structural differentiation of the subunits is accompanied by functional differentiation, as shown in previous investigations of their O2 and CO affinities (Sullivan, B., Bonaventura, J., and Bonaventura, C. (1974) Proc. Natl. Acad. Sci. U.S.A. 71, 2558-2562; Bonaventura, C., Bonaventura, J., Sullivan, B., and Bourne, S. (1975) Biochemistry 13, 4784-4789). The subunit diversity of Limulus hemocyanin suggests that other electrophoretically heterogeneous hemocyanins may be composed of structurally distinct subunits.     

INHIBITION OF CHLORELLA (CHLOROPHYCEAE) GROWTH BY FATTY ACIDS, USING THE PAPER DISC METHOD1,2

Using the paper disc-agar plate method, a number of fatty and related acids have been tested for tested activity for inhibiting the growth of Chlorella pyrenoidosa Chick. Of the saturated acids, a peak in growth inhibiting activity wax observed in the C₇–C₁₂ range, where inhibition wax observed when solutions down to 0.02 M were applied to the discs. Most of the unsaturated acids tested showed greater inhibition than did the corresponding saturated acids. Acrylic acid showed detectable inhibition at 0.001 M concentration.     

The cellular location of proteases in Candida albicans

Vacuoles prepared from yeast cells of Candida albicans were enriched in proteinase ycaB (EC 3.4.21.48) but not in aminopeptidase or beta-glucosidase. Proteinase ycaB, assayed in situ, increased 1.5-fold during starvation whereas aminopeptidase activity decreased by 25%. Proteinase ycaB increased a further 1.5-fold during germ-tube formation.     

Strategies for automated sequencing of human mitochondrial DNA directly from PCR products.

A rapid, robust and sensitive method has been developed for the amplification and direct sequencing of human mitochondrial DNA. A 403-bp hypervariable segment was amplified by two successive rounds of nested PCR. This was then sequenced by the dideoxy chain termination method using dye-labeled universal sequencing primers in conjunction with an automated DNA sequencer. This paper describes the assessment of four different strategies for this amplification and sequencing process. Optimal results were obtained by immobilizing the biotinylated PCR product on Dynabeads followed by solid-phase sequencing with Sequenase. Degraded samples and those containing trace amounts of DNA such as extracts from hair shafts can be analyzed by this method.     

Changes in Prokaryote and Eukaryote Assemblages Along a Gradient of Hydrocarbon Contamination in Groundwater

Groundwater biota are particularly sensitive to environmental perturbations such as groundwater contamination. The diversity of prokaryotic and eukaryotic biota has been examined along a gradient of chlorinated hydrocarbon (CHC) contamination in the Botany Sands, an urban coastal sand-bed aquifer (Sydney, Australia). Molecular techniques were used to analyze the richness and composition of prokaryote and eukaryote assemblages using 16S and 18S rDNA, respectively. Taxon richness did not change significantly along the gradient for either prokaryotes or eukaryotes; however, significant shifts in assemblage composition were evident for both groups. Assemblage changes were most strongly correlated with concentrations of the major CHC, cis-1,2-dichloroethene, but the concentrations of a number of the contaminants were also correlated, making it difficult to infer if effects were due to any particular contaminant. The presence of cis-1,2-dichloroethene and other secondary ethenes suggests in situ breakdown of the primary CHCs via natural attenuation. The current focus of management of the Botany aquifer is to stop the contaminant plume reaching the adjoining estuary. This approach is clearly justified given the changes evident in the microbial assemblages in the groundwater, which are a likely consequence of the contamination.     

Effects of grouping and fighting on the reproductive tracts of male white-footed mice (Peromyscus leucopus)

Summary Adult, male white-footed mice (Peromyscus leucopus) were subjected to a variety of social situations ranging from isolation during the 20 day experimental period to constant contact with both females and other adult males. Contacts included grouping (three or four males per cage) and exposure to fighters (once daily for 20 minutes). The following measurements were recorded: weights of the body, testes, epididymides, vesicular glands, vesicular gland tissue (wet and dry), seminal fluid of the vesicular gland, adrenal glands, and baculum; spermatozoan reserves of the testes and epididymides. Grouping significantly affected both the weight and spermatozoan reserves of the testes and epididymides, as well as both the tissue and seminal fluid weight of the vesicular glands. The results suggested a graded effect of all treatments on the reproductive tract. In order of magnitude of the associated response, from none to greatest, the treatments may be ranked as follows: pairing with females, isolating, handling, fighting, and grouping. All reproductive parameters measured showed this general ranking, suggesting that the response to the various treatments was similar and differed only quantitatively. The results further suggested decreased secretion of LH and testosterone, although measurements of testosterone did not substantiate this conclusion. The lack of significant effects of grouping on adrenal gland weights strengthened the argument that adrenal involvement is not a necessary adjunct to the suppression of the reproductive tract in groupedPeromyscus, but the adrenal may be involved if contacts between males result in overt fighting.     

Globus and headache: common symptoms of the irritable bowel syndrome.

Persons with the irritable bowel syndrome (IBS) have a significantly higher prevalence of globus and migraine-like headache than age-matched control subjects. On the other hand, persons with organic disease of the esophagus or colon may have a reduced prevalence of functional symptoms involving the opposite end of the gastrointestinal tract. The dispersed pattern of symptoms in IBS suggests that some agent, such as a hormone, may be acting systemically.     

The split calvarial graft donor site in the elderly: a study in cadavers

In 37 cadavers of average age 75.5 years, the calvarium was studied. In all, the diploe and outer and inner tables were found to be definite layers. Although the parietal bone thickness did decrease with age in this study, there was no correlation between age and the outer table or diploe thickness. No significant change with age occurred in the occipital bone. Although this study supports the use of split calvarial grafts in older patients without the necessity for a craniotomy, the relative brittleness of this bone in this population should be considered.