Cytometric investigations on hemocytes of the American oyster, Crassostrea virginica

Pericardial hemolymph was obtained from American Oysters (Crassostrea virginica) and the hemocytes characterized by flow cytometry. The cells were found to have a broad unimodal size distribution with a median diameter of 7 micrometers. Total protein measured by flow cytometric fluorescence of dansylated cells also revealed a broad unimodal distribution similar to that obtained for size. The proportion of hemocytes in each stage of the cell cycle was measured using DNA-specific DAPI fluorescence. Histograms showed a single peak representing the G(0)/G(1) population. There was no evidence of S or G(2)+M phases of the cell cycle, nor was polyploidy seen. The forward and orthogonal light scatter of fixed hemocytes showed no evidence of sub-populations on the basis of cytoplasmic granularity. Thus, in terms of these parameters, oyster hemocytes appear to represent a single population exhibiting graded cellular differences.

In vivo chemoactivation of oyster hemocytes induced by bacterial secretion products

Movements of tissue hemocytes in the Eastern oyster Crassostrea virginica were monitored and quantified by image analysis of sections following inoculation with agar cores containing Escherichia coli or cell-free medium on which the bacteria had previously grown. Hemocytes respond to the presence of live bacteria by accumulating in widely dispersed areas of tissue surrounding the gut and digestive diverticula. The response is rapid and evident within 40 min, is maximal at 1 hr, and declines by 3 hr after inoculation. Sterile implanted agar cores do not produce a response. Bacteria killed with ozone elicit a response when inoculated together with the medium on which they had grown while bacteria killed by heat or formalin do not. Killed bacteria suspended in saline fail to stimulate hemocyte chemokinesis. Cell-free medium applied externally produces a response equal to that measured with live bacteria inoculated internally. Extraction of bacteria-free medium with hexane does not significantly reduce hemocyte chemokinesis. Digestion of bacteria-free medium with pronase completely eliminates chemokinesis. Molecular filtrates of bacteria-free medium induce maximal chemokinetic response at molecular weight as low as 1 kDa. These data show that the oyster hemocyte activators produced by E. coli are most likely low-molecular-weight polypeptides which diffuse from the site of inoculation and can pass through the intact external surface epithelium to induce a chemokinetic response.

Atrial natriuretic peptide gene expression within invertebrate hearts

The present investigation was designed to (1) determine if atrial natriuretic factor gene expression occurs within invertebrates as well as within vertebrates; (2) determine whether the product of this gene expression is the 126-amino-acid atrial natriuretic factor prohormone or some other molecular species; and (3) evaluate within the same invertebrates if the products of atrial natriuretic factor gene expression are released into their circulation. Utilizing a very sensitive RNase protection assay it was found that atrial natriuretic peptide gene expression occurs within the heart of the oyster, Crassostrea virginica, and within the heart of the blue crab, Callinectes sapidus, but was expressed sevenfold less than in a vertebrate heart (i.e., rat, Rattus norvegiucs). High-performance gel-permeation chromatography followed by N-terminal and C-terminal atrial natriuretic factor prohormone radioimmunoassays indicated that the molecular species synthesized within the oyster and blue crab hearts was the atrial natriuretic factor prohormone. The product(s) of this atrial natriuretic factor gene expression (i.e., atrial natriuretic peptides) was found to be released into the circulation, i.e., hemolymph, of both the oyster and the blue crab.

Atrial natriuretic peptides in the heart and hemolymph of the oyster, Crassostrea virginica: a comparison with vertebrates

1. The content of atrial natriuretic peptides (ANPs) in the auricles of oysters, Crassostrea virginica, was significantly (P < 0.01) greater than in their ventricles. 2. High-performance gel permeation chromatography (HP-GPC) followed by ANF radioimmunoassay revealed two peaks in both oyster and vertebrate (rat) hearts--a major peak where the 12.6-14 kDa ANF prohormone elutes and a smaller peak where the pure human form of ANF elutes. 3. HP-GPC evaluation followed by proANF 31-67 radioimmunoassay revealed only an ANF-like prohormone while HP-GPC followed by proANF 1-30 radioimmunoassay revealed the ANF prohormone and a proANF 1-30-like peptide in oyster and rat hearts. 4. ANPs concentrations in hemolymph were 940 +/- 129, 225 +/- 25, and 100 +/- 10 pg/ml by the proANF 1-30, proANF 31-67, and ANF radioimmunoassays, respectively. 5. Atrial natriuretic-like peptides are present in the oyster heart in molecular species similar to vertebrate species and these peptides are also present in hemolymph.

Hydroperoxide metabolism of amphibia: tissue catalases of leopard frogs

Catalase activities were measured and compared in liver, kidney, heart, and lung of American Leopard Frogs (Rana pipiens complex). The order of activities was found to be liver greater than kidney greater than heart approximately lung. The liver enzyme was found to be inhibited by aminotriazole, cyanide, and azide and appears to peroxidatively oxidize ethanol.

Dermal myiasis of the eyelid

A case report describes the clinical findings of dermal myiasis of the upper eyelid in a 6-year-old girl from South America. Dermal myiasis due to Dermatobia hominis can simulate a common furuncle and is known to occur in world travelers.

Succinate dehydrogenase in various tissues of Anodonta couperiana, Elliptio buckleyi and Mercenaria campechiensis (Mollusca: Bivalvia)

The specific activities, kinetic constants and pH optima for succinate dehydrogenase were determined in mantle, gill and adductor muscle from three bivalves (Anodonta couperiana, Elliptio buckleyi and Mercenaria campechiensis). In general the Km values for succinate and Ki values for fumarate differed in all bivalve tissues whereas the Ki for malonate was consistently low. The ratio of Ki (fumarate) to Km (succinate) was less than one for all tissues studied. This is similar to many facultative anaerobes with fumarate reductase activity.