Harold D. Howse

SOME PARASITES AND DISEASES OF ESTUARINE FISHES IN POLLUTED HABITATS OF MISSISSIPPI

Diseases that afflict aquatic animals living in waters suspected or known to be polluted are described. The following pollutants are discussed with regard to their effects on the environment and the animals of the estuaries; pesticides, industrial chemicals, heavy metals, and fecal pollution. Microorganisms are discussed with regard to public health and fish health. Transmission of the virus of infectious hepatitis by oysters is emphasized. Parasitic diseases are discussed with regard to life cycle of the parasite, effects of pollution on intermediate hosts, and host specificity. Diseases caused by various helminth and protozoan parasites are described. Nonparasitic diseases discussed are integumental hyperplasia, liver disease, and various neoplasms. (HLW)

A comparative histochemical and electron microscopic study of the surface coatings of cardiac muscle cells

Abstract An external lamina was present on the plasma membrane of the myocardial cells of all species studied. The thickness of this lamina measured about 1000 A in crustaceans, 300 to 400 A in fishes, 400 to 650 A in amphibians, 400 to 500 A in reptiles, and 200 to 400 A in mammals. Histochemical studies at the light and electron microscopic level showed that the external lamina is rich in carbohydrates with acidic residues. It is proposed that the external lamina acts as a selective barrier between the intra- and extracellular environment. As a circulatory system develops in the myocardium, this function is shared by the basal lamina of endocardial and capillary endothelial cells. A lamina similar to that of the plasma membrane was observed on the luminal surface of the transverse tubular system (T-system). However, a T-system was not found in cells in which the myofibrils are located primarily in the periphery of the cell, but only in cells in which the myofibrils are either centrally located or evenly distributed within the cell.

Prismatic cristae and paracrystalline inclusions in mitochondria of myocardial cells of the oyster Crassostrea virginica Gmelin

SummarySeveral types of unusual mitochondrial configurations were found in myocardial cells of the oyster Crassostrea virginica Gmelin. These mitochondria include, in order of frequency, prismatic cristae, filamentous paracrystals in honeycomb and herringbone configurations, and paracrystals composed of rows of electron dense particles. The long, parallel, evenly spaced prismatic cristae are square or rhomboidal in cross section. In the space between the prismatic cristae are rodlike structures (4–6 nm in diameter) that are regularly spaced about 12nm apart and appear to pass between adjacent cristae. Filamentous paracrystals are observed in slender, elongated mitochondria. The filament spacing and form of these paracrystals suggest that they are composed of the intercristal rods. Alternatively, filamentous paracrystals might be tangential sections of prismatic cristae and intercristal rods. Particulate paracrystals which consist of dense lines or rows of particles are the least frequent type of unusual configuration. The particles are triangular, possibly pyramidal, in shape; their bases are 10–12 nm thick and repeat in rows every 17–18 nm. There is a close association between particulate paracrystals and prismatic cristae plus intercristal rods. Although similar mitochondrial configurations have been associated with disease or altered metabolism in a number of species, we have found no such association in the oyster as yet.

Fine Structure of the Myocardium of the Blue Crab Callinectes sapidus Rathbun

The myocardium of the blue crabCallinestes sapidus has the following ultrastructural features. Myocardial cells are transversely striated with A, I, and Z-bands, H-zones, and M-lines. Thick myofilaments are arranged in a hexagonal pattern and each thick myofilament is surrounded by six thin myofilaments. The sacrotubular system consist of the sacroplasmic reticulum, transverse tubules, and longitudinal tubules. Intercalated discs having gaps 40–600 A wide connect adjacent muscle cells end-to-end. Interstitial cells are often observed beneath the external laminae of the myocardial cells. Nerve terminals and glial elements are also embedded in the myocardial cells. The nerve terminals contain both dense and clear vesicles. The dense vesicles are round (800–1000 A in diameter), whereas clear vesicles are either round (360–600 A in diameter) or flattened (350×700 A). *** DIRECT SUPPORT *** A00BY066 00004

Ubiquitous perivenous smooth muscle cords in viscera of the teleost Rachycentron canadum, with special emphasis on liver

The liver of the cobia, Rachycentron canadum, was examined by gross dissection, histological, and ultrastructural procedures. Other visceral organs were examined by histological techniques only. Unique perivenous smooth muscle cords are associated with veins in these systems, but they are particularly prominent in their association with the hepatic portal veins and their numerous intrahepatic branches. The perivenous smooth muscle cords accompany tributaries of the portal veins to the junction of the venules with the hepatic sinusoids. The reciprocal contraction and relaxation of various segments of the smooth muscle cords appear to result in pooling of blood in temporary reservoirs and in its transport to various regions of the organ. This process might apply to other organ systems as well. Possibly this unique relationship of the smooth muscle cords with veins functions in a diving reflex. Triads are occasionally encountered in the cobia liver.