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Biomedical subjects

R M Overstreet

Publications and source records attributed to R M Overstreet.

At least 37 records · Page 2Linked to original sources
PubMed1993

Host specificity of Calyptospora funduli (Apicomplexa: Calyptosporidae) in atheriniform fishes.

Calyptospora funduli has a broad host specificity, infecting at least 7 natural and 10 additional experimental definitive hosts, all atheriniform fishes within 5 families, but most in the genus Fundulus. Barriers, apparently innate ones, prevent any development of C. funduli in perciform fishes but allow incomplete or abnormal development of the parasite in a few unnatural atheriniform hosts. In the freshwater species Fundulus olivaceus and Fundulus notti, these abnormalities consisted of asynchronous development, degeneration of the parasite in early stages of development, and the formation of numerous macrophage aggregates. Rivulus marmoratus has the ability to eliminate infections with a granulomatous inflammatory response. Additional barriers that limit natural infections of C. funduli in other hosts include feeding behavior, environmental conditions, and geographic isolation.

Animals↗
PubMed1991

Rickettsial and mollicute infections in hepatopancreatic cells of cultured Pacific white shrimp (Penaeus vannamei).

Infections by multiple species of bacteria occurred in hepatopancreatic epithelial cells of cultured Pacific white shrimp (Penaeus vannamei). Grossly, hepatopancreases of moribund shrimp were pale white. Light microscopically, hepatopancreatic tubules appeared atrophied and were associated with granulomas. Examination by scanning and transmission electron microscopy revealed heavy cytoplasmic infections by three forms of microorganisms: (1) a rickettsia-like bacterium, (2) a helical form of a mollicute-like bacterium, and (3) a filamentous mollicute-like bacterium. The rod-shaped rickettsia (900 nm long by 300 nm wide) appeared to be free in the cytoplasm and had both a plasma membrane and a cell wall. Neither form of mollicute possessed a cell wall. The helical mollicute was blunt at its wide end (about 260 nm in diameter) where it contained electron-lucent bodies. Helical turns along its tapered axis resembled those of a spiroplasma (the only helical form of mycoplasma in the class Mollicutes) or a spirochete. The helical bacterium did not possess periplasmic flagella characteristic of spirochetes, which lends support to its being a type of spiroplasma. The filamentous mollicute consisted of masses of short, branched filaments 60 nm wide with intermittent spherical dilations and terminal blebs on the branches. The presumed mollicutes have not been reported previously in crustaceans. Each bacterium, or concurrent infections of the bacteria, are pathogenic to cultured shrimp, could impact culture operations and thus deserve more study.

Animals↗
PubMed1991

Heliconema brooksi n. sp. (Nematoda: Physalopteridae) from the ophichthid eel Ophichthus gomesi in the Gulf of Mexico.

Heliconema brooksi n. sp. is described from the shrimp eel, Ophichthus gomesi, in Mississippi Sound. This species is distinguished from other members of the genus by possessing in the male 40 or more tessellated longitudinal ridges, a spicule ratio averaging 1:10.6, 4 precloacal papillae, and 6 postcloacal papillae. Females have a protruding vulvular flap. Both sexes have a prominent sclerotized cardium. Heliconema brooksi is morphologically most closely related to Heliconema heliconema. A juvenile worm from the white shrimp, Penaeus setiferus, in the same locality may be the infective stage.

Animals↗
PubMed1990

Occurrence of thymic lymphoma in carcinogenesis bioassay specimens of the Japanese medaka (Oryzias latipes).

Multiple cases of thymic lymphoma were diagnosed in bioassay specimens of Japanese medaka (Oryzias latipes), a small fish species. Lymphoma in chemically exposed specimens was not clearly related to specific compounds, dose, or sex. Multiple cases of lymphoma occurred in three specimens held in one aquarium and in two specimens in two other aquaria, suggesting the possibility of horizontal transmission. Forty cases were observed in 9802 specimens (0.41%), with an incidence of 0.46% in exposed specimens (5690 total) and 0.34% in controls (4112 total). Lesions were dominated by small cells with large, basophilic nuclei and a thin cytoplasmic rim. Mitotic figures were frequently observed. Electron microscopy showed that the nuclei of lymphoma cells were highly invaginated but revealed no viral particles. Lymphomas appeared to originate in the thymus and subsequently infiltrate esophagopharyngeal regions, retroperitoneal spaces, cranial regions, heart, and abdominal viscera. Given the scattered occurrence of the lymphomas and the fact that they tend to occur in specimens in contact with one another, we suspect a viral etiology. Lymphoma appears to be the most frequently occurring spontaneous neoplasm in medaka and should be taken into account when assessing results of carcinogenesis studies.

Animals↗
PubMed1990

Carcinogenic effects of some polycyclic aromatic hydrocarbons on the Japanese medaka and guppy in waterborne exposures.

In this paper, we review studies on the carcinogenic effects of two polycyclic aromatic hydrocarbons (PAHs), benzo(a)pyrene (BaP) and 7,12-dimethylbenz(a)anthracene (DMBA), on the Japanese medaka (Oryzias latipes) and the guppy (Poecilia reticulata). Exposure media were prepared by adding PAHs to water, with and without dimethylformamide (DMF) as a carrier, and passing this solution through various sized filters. The low exposure medium was a 0.45 micron filtrate without DMF that contained less than 5 micrograms L-1 PAH. The intermediate medium was a DMF-mediated 0.45 micron filtrate which contained 30-50 micrograms L-1 of PAH. The high medium was a DMF-mediated glass-fibre filtrate which contained 150-250 micrograms L-1 of PAH. Young fish specimens (6-10 d old) were given a 6 h exposure once weekly for 2 to 4 wk. Both BaP and DMBA induced hepatic neoplasms in the two species, with the medaka being more sensitive than the guppy, and DMBA being a stronger carcinogen than BaP. Liver neoplasms almost exclusively developed after exposure to BaP and the neoplasms were limited to the high concentration exposure, whereas DMBA caused a substantial number of extrahepatic neoplasms as well as hepatic ones, especially in the medaka. Furthermore, all three concentrations of DMBA induced hepatic neoplasms in the medaka and all but the low concentration induced neoplasms in the guppy. These studies demonstrate the carcinogenic effects of two waterborne PAHs on two small fish species following brief exposures to very low concentrations, and support the contention that environmental PAHs can contribute to the occurrence of cancer in wild fishes.

Animals↗
PubMed1990

Antipodean aquaculture agents.

Parallel features exist among diseases in Antipodean hosts when compared with those in other tropical and temperate regions. These features can be associated between infections in fish and prawns and between infections in freshwater and saltwater systems. Both fish and prawns are prone to physical stress, to behavioural stress, and to both introduced and native disease agents, agents that are limiting factors in several established aquaculture ventures. Both types of hosts are reared in a variety of facilities, each allowing for a different dynamic predisposition for disease. These diseases include those caused by native freshwater, estuarine and marine agents in both introduced and native hosts, and by introduced agents in those hosts. Some infections reflect unexpected or unidentifiable agents and host responses. Much can be learned in Australia and New Zealand from the infections, successes, failures and innovative methodologies experienced or used in the rest of the world. Potential in the Antipodes for production of unique and abundant fishery products is immense for both local and export markets. Approaches, however, should remain cautious regarding introductions and persistent regarding the investigation of potential diseases, host responses, diagnostic methods and management techniques.

Animals↗
PubMed1988

Dose-related carcinogenic effects of water-borne benzo[a]pyrene on livers of two small fish species.

Benzo[a]pyrene (BaP) administered by water-borne exposures caused dose-related carcinogenic effects in livers of two small fish species, the Japanese medaka (Oryzias latipes) and the guppy (Poecilia reticulata). Medaka and guppies each were given two 6-h exposures. The first exposure was conducted on 6- to 10-day-old specimens. The second exposure was given 7 days later. The tests incorporated five treatment groups: (1) control, (2) carrier (dimethylformamide) control, (3) low BaP dose (not detectable--4 ppb), (4) intermediate BaP dose (about 8-47 ppb BaP), and (5) high BaP dose (200-270 ppb). Following the high-dose exposure, hepatocellular lesions classified as foci of cellular alteration (altered foci), adenomas, and hepatocellular carcinomas occurred in both species. In medaka, the lesions appeared to develop sequentially with the appearance of altered foci followed by adenomas and then hepatocellular carcinomas. Most lesions in guppies, however, were classified as altered foci although a few adenomas occurred in the early (24-week) sample and hepatocellular carcinomas occurred in the late (52-week) sample. When total lesions were combined, medaka had an 11% incidence at 24 weeks after the initial exposure and 36% incidence at 36 weeks. In guppies, 8% had liver lesions at 24 weeks, 19% at 36 weeks, and 20% at 52 weeks. A single extrahepatic neoplasm, a capillary hemangioma in a gill filament, occurred in a medaka from the 36-week high-dose sample. The results suggest that the medaka and guppy are capable of metabolizing water-borne BaP to carcinogenic metabolites which initiate hepatic tumor development.

Adenoma↗
PubMed1987

Exocrine pancreatic neoplasms induced by methylazoxymethanol acetate in the guppy Poecilia reticulata.

Exocrine pancreatic neoplasms developed in the guppy Poecilia reticulata following a single brief exposure to methylazoxymethanol acetate [(MAM-Ac) CAS: 592-62-1]. Fish 6-10 days old were exposed to concentrations of MAM-Ac up to 100 mg/liter for 2 hours. Exposed specimens were transferred to carcinogen-free water and sampled periodically for tumor development. Pancreatic neoplasms occurred in approximately 9% of histologically examined individuals exposed to 10 mg MAM-Ac/liter or less. Neoplastic lesions were not found in 122 control specimens. The neoplasms included 6 cases diagnosed as adenoma, 7 cases diagnosed as acinar cell carcinoma, and 2 cases diagnosed as adenocarcinoma. Adenomas consisted mainly of well-differentiated acinar cells that were filled with zymogen granules. Two adenomas also contained foci of atypical, less-differentiated acinar cells possessing basophilic, fibrillar cytoplasm. Acinar cell carcinomas occurred in several cellular patterns that ranged from well-differentiated to more anaplastic lesions; however, none exhibited areas of ductular proliferation. Adenocarcinomas, on the other hand, exhibited a glandular growth pattern and contained numerous ductlike structures. Both types of carcinomas appear to arise from primary acinar cells. Thus lesions probably progress from adenomas to acinar cell carcinomas and adenocarcinomas. The findings of carcinogen-induced pancreatic neoplasms in guppies further strengthen the usefulness of small fish species in carcinogen testing and provide an additional model for pancreatic tumors.

Adenocarcinoma↗
PubMed1986

Piscine adult nematode invading an open lesion in a human hand.

The first case of an adult, parasitic nematode entering an open lesion is reported. A female dracunculoid, Philometra sp., invaded a puncture wound in a fisherman's hand while he was filleting an infected carangidae fish, Caranx melampygus, in Hawaii. This accidental infection represents a previously unrecognized risk in handling uncooked, infected fish.

Adult↗
PubMed1986

Intraocular neoplasms induced by methylazoxymethanol acetate in Japanese medaka (Oryzias latipes).

Intraocular neoplasms developed in the Japanese medaka, a small fish species, following a single brief exposure to methylazoxymethanol acetate [(MAM-Ac) CAS: 592-62-1]. Specimens 6-10 days old were exposed to doses of MAM-Ac up to 100 mg/liter for 2 hours and then transferred to carcinogen-free water for "grow-out." Of 218 exposed fish examined, 98 (45%) had neoplastic lesions in various stages of development. Of those exposed to 30 mg/liter or more, 57% had the lesions. No lesions were found in eyes or other tissues of 95 control specimens. Early and advanced neoplastic lesions were recognized. Early lesions were characterized by complexes of neoplastic retinal epithelium and tubes that consisted of cells of the sensory retina. Areas of mitotically active, heterogeneous cells associated with such complexes gave rise to advanced neoplasms. We considered the advanced neoplasms to be medulloepitheliomas, which differentiated into three principal cellular patterns: 1) solid masses of unpigmented cells, which frequently showed photoreceptor differentiation as well as ductular formation; 2) heavily pigmented cuboidal to columnar cells resembling retinal epithelium that formed adenomatous patterns; and 3) teratoid medulloepitheliomas. Teratoid medulloepitheliomas, which we considered the most advanced and malignant lesions, consisted of heterogeneous, highly mitotic, invasive cells and contained heteroplastic elements including striated muscle, undifferentiated mesenchymal tissues, and hyaline cartilage. We suggest that MAM-Ac induces hyperplasia of retinal cells followed by establishment of aberrant growth zones containing miscoded cells that give rise to medulloepitheliomas.

Age Factors↗
PubMed1985

Development of aquarium fish models for environmental carcinogenesis: an intermittent-flow exposure system for volatile, hydrophobic chemicals.

An intermittent-flow exposure system was designed to provide stable and manipulative concentrations of volatile and hydrophobic compounds to small aquatic animals for uninterrupted long periods. Test species for 28-day experiments included two aquarium fishes, the Japanese medaka (Oryzias latipes) and the king cobra guppy (Poecilia reticulata). Test chemicals included trichloroethylene, vinylidene chloride, bis(2-chloroethyl)ether, ethylene dichloride, and a mixture of carbon tetrachloride, trichloroethylene, chloroform, bromodichloromethane, chlorodibromomethane and bromoform. These compounds are drinking water biorefractories and are potentially carcinogenic. Concentrated aqueous toxicant solutions, delivered from a remote triple carboy dispensing system, were mixed with diluent water within an isolated chamber containing exposure aquaria and test fish. Toxicant concentrations measured throughout each exposure period proved to be stable within acceptable variability ranges as indicated by coefficients of variation generally less than 15%.

Animals↗
PubMed1985

Development of aquarium fish models for environmental carcinogenesis: tumor induction in seven species.

For small fish species to be utilized as models for carcinogenicity testing they should be capable of developing neoplasms, preferably in multiple tissues, when exposed to known carcinogens. Seven species of small fish were exposed to methylazoxymethanol acetate (MAM-Ac) and tumor development was monitored. Specimens 6-10 days old were exposed to nominal concentrations of MAM-Ac up to 100 mg 1(-1) for 2 h, then transferred to carcinogen-free water. Hepatic neoplasms developed in the Japanese medaka, guppy, sheepshead minnow, Gulf killifish, inland silverside, rivulus, and fathead minnow. Additionally, neoplasms occurred in other organs and tissues of the medaka (retina, various mesenchymal tissues, exocrine pancreas, kidney, and nervous tissue), guppy (mesenchymal tissue, exocrine pancreas, and kidney), and sheepshead minnow (choroid gland, mesenchymal tissues, and nervous tissue). All tumors were diagnosed in specimens within 1 year post-exposure. Early signs of liver tumors appeared in medaka and guppy at about 1 month post-exposure. These studies show that both medaka and guppy would be good models because they appear sensitive to carcinogens, develop tumors in multiple tissues and are easy to breed and maintain. Certain other small fish species also may prove to be good models because of habitat preferences, breeding strategies, or genetic attributes.

Animals↗
PubMed1981

Hemorrhagic lesions in stomach of rhesus monkey caused by a piscine ascaridoid nematode.

Within a few hours after being administered to the rhesus monkey (Macaca mulatta), Hysterothylacium type MB larvae penetrated the stomach wall, causing hemorrhage and attracting eosinophils. Inocula up to 300 larvae, however, did not cause peripheral hypereosinophilia. This species is the first ascaridoid which normally matures in fish that has been shown to penetrate the alimentary tract of a primate. Consequently, human consumption of raw seafood from at least the northern Gulf of Mexico free from infections, with Anisakis spp., Phocanema decipiens, or other species that mature in mammals or birds does not necessarily assure freedom from anisakiasis as previously assumed.

Animals↗
PubMed1980

Biology and pathogenesis of the coccidium Eimeria funduli infecting killifishes.

Epizootics of Eimeria funduli involved estuarine killifishes (Fundulus grandis, F. pulvereus, F. similis, and F. heteroclitus) in Mississippi, Alabama, and Virginia. All of more than 500 specimens examined of F. grandis from Mississippi during 1977 though 1979 had infections, regardless of age, sex, or season collected. Oocysts occurred primarily in the liver and pancreas, replacing up to 85% of both those organs. Infrequent sites of infection were fatty tissue of the body cavity, ovary, intestine, and caudal peduncle. Living fish did not discharge oocysts. Eimeria funduli is the first known eimerian to require a second host. To complete the life cycle, an infective stage in the grass shrimp Palaemonetes pugio had to be eaten. In 6-mo-old killifish reared in the laboratory at 24 C, young schizonts were first observed in hepatic and pancreatic cells 5 days postfeeding, followed by first generation merzoites by day 10, differentiation of sexual stages during days 15 to 20, fertilization between days 19 and 26, sporoblasts from days 25 to 30, and sporozoites about day 60. Unique sporopodia developed on sporocysts by day 35 when still unsporulated. Temperatures of 7 to 10 C irreversibly halted schizogony. Both schizogony and sporogony progressed slower as age of host increased. When infective shrimp in doses ranging from 1 to 10% of a fish's body weight were eaten, the level of intensity of resulting infections did not differ significantly. Pathogenesis followed a specific sequence, with the host response apparently unable to contend with extensive infections as seen typically in nature and in our experiments. Premunition was indicated. When administered Monensin orally, infected fish exhibited a reduction in oocysts by 50 to 70% within 20 days as compared with untreated fish. Furthermore, infected killifish exclusively on a diet of TetraMin for 3 mo completely lost their infections.

Animals↗
PubMed1979

Sporogenesis of a myxosporidan with motile spores.

Three types of cells comprise each Fabespora vermicola sporoblast: valvogenic (VAV), capsulogenic (CAP), and germinative (GEM). Walls, polar caps, and sutures are the main assemblages produced by the VAV cells. The unique polar cap organelle extends over the aperture region of the polar capsule component of the CAP cell. The VAV cell also assembles a wall located on the cytoplasmic side of the plasma membrane facing the sporoblast exterior. Bundles of 7 nm microfilaments develop within the extracellular space between the VAV and interior cells of the sporoblast. These microfilaments assemble late in sporogenesis when the spore acquires the capacity for locomotion. Polar filament construction takes place exclusively within the polar capsule primordium (PCP) by apparent self-assembly prior to the PCP being enveloped by membranes. The CAP and GEM cells accumulate considerable glycogen during sporogenesis. The first identifiable GEM cell is single, but has two unpaired nuclei. These GEM cell nuclei later form a paired structure which is sustained into the spore stage.

Animals↗
PubMed1979

A new and unusual eimerian (protozoa: Eimeriidae) from the liver of the Gulf killifish, Fundulus grandis.

Oocysts and sporocysts of Eimeria funduli sp. n. are described from the Gulf killifish, Fundulus grandis, on the basis of light microscopy, transmission and scanning electron miscroscopy, and location in the liver of infected hosts. The spherical sporulated oocysts of E. funduli isolated from liver tissue measure 20-31 (25) micrometer across with ovoid sporocysts 9-11 X 5-7 (10 X 6) micrometer. A micropyle, polar granule, and oocyst residuum are absent, but sporocysts have Stieda and substieda bodies, a few residual granules, and 10-25 (15) unique projecting structures with expanded distal portions that we term "sporopodia". Sporopodia 1-3 (2) micrometer high support a transparent membrane that completely surrounds the sporocyst. Sporozoites have one large posterior refractile body. Ultrastructurally, the oocyst wall consists of two thin layers of granular material: an electron-dense outer layer with a rough external surface and an electron-lucent inner one of approximately equal thickness. One or two unit membranes line the inner surface of the inner layer. Each layer is 40-60 (55) nm thick. The sporocyst wall, 78-130 (110) nm thick, consists of an electron-lucent material with the outer surface being more electron dense and giving rise to osmiophilic sporopodia; closely associated with these and the outer surface are one or two unit membranes. A thin osmiophilic layer of fine granular material lines the inner surface.

Animals↗