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Biomedical subjects

M L Kent

Publications and source records attributed to M L Kent.

17 recordsLinked to original sources
PubMed1992

A retrovirus in chinook salmon (Oncorhynchus tshawytscha) with plasmacytoid leukemia and evidence for the etiology of the disease.

A plasmacytoid leukemia (PL) has caused mortalities in chinook salmon (Oncorhynchus tshawytscha) reared in seawater netpens in western British Columbia, Canada, since 1988. Kidney or eye tissues from 11 of 13 fish from netpens with clinical PL had reverse transcriptase (RT) activity. This RT activity was associated with virus particles of retrovirus morphology and buoyant density. In a transmission experiment, PL-positive donor fish tissues also had RT activity and virus particles of retrovirus morphology and buoyant density, as did recipient fish tissues following development of the disease 6 weeks postinjection with a tissue homogenate from the donor fish. Kidney and spleen tissues from fish that developed PL following injection with an inoculum that was passed through a 0.22-micron filter, in a separate experiment (M. L. Kent and S. C. Dawe. Further evidence for a viral etiology in the plasmacytoid leukemia of chinook salmon Oncorhynchus tshawytscha. Dis. Aquat. Org., in press, 1992), also exhibited RT activity. The virus particles observed by electron-microscopic examination of tissues or sucrose fractions from PL-positive fish were enveloped and were about 110-nm diameter with a central electron-dense core. Polypeptides of about M(r) 120,000, 80,000, 42,000, 27,000, 25,000, 22,000, and 19,000 were observed when purified virus particles were examined by polyacrylamide gel electrophoresis analysis. Many infectious neoplasms of animals, including fishes, are caused by retroviruses. The evidence in this study shows the presence of a retrovirus in chinook salmon with PL and further suggests a retroviral etiology of the disease. We are tentatively calling this virus salmon leukemia virus.

Animals↗
PubMed1991

Coccidia, X-cell pseudotumors and Ichthyophonus sp. infections in walleye pollock (Theregra chalcogramma) from Auke Bay, Alaska.

One hundred twenty-five walleye pollock (Theragra chalcogramma) were collected from Auke Bay, Alaska (USA) in 1985 and examined for histologic evidence of disease-causing infectious agents in 1987. A Goussia sp.-like coccidium was found in the kidney tubules of 75% and an Eimeria sp.-like coccidium was found in the intestine of 18% of the fish examined. The kidney coccidium was associated with sloughing of the tubular epithelium, peritubular fibrosis and granuloma formation. The intestinal coccidium was associated with severe tissue displacement and inflammation. In addition, X-cell pseudotumors were observed in the pseudobranchs (4%), and the fungus Ichthyophonus sp. was observed in the kidney, intestine or brain of 2% of the pollock.

Animals↗
PubMed1990

Experimental transmission of a plasmacytoid leukemia of chinook salmon, Oncorhynchus tshawytscha.

A plasmacytoid leukemia of chinook salmon, Oncorhynchus tshawytscha, has recently been recognized in seawater netpens in British Columbia, Canada. The disease has occurred at several sites and has caused high mortality. Plasmacytoid leukemia is characterized by a generalized invasion of visceral tissues and the orbit of the eye by plasmacytoid cells. The disease was experimentally transmitted to healthy chinook salmon by i.p. injection of kidney tissue homogenates, but transmission with a cell-free filtrate was equivocal. In another experiment, chinook salmon, coho salmon, O. kisutch, sockeye salmon, O. nerka, rainbow trout, O. mykiss (or Salmo gairdneri), and Atlantic salmon, Salmo salar, were given injections of a tissue homogenate from affected chinook salmon. Ten wk after exposure, plasmacytoid leukemia was observed in all of the sockeye salmon and chinook salmon, one of ten Atlantic salmon, and none of the rainbow trout. Seven of the ten coho salmon examined at 10 wk had lesions suggestive of early development or a mild form of the disease. Multifocal areas of proliferating cells resembling plasmablasts were observed in the visceral fat, and the kidneys exhibited mild to moderate hyperplasia of the hematopoietic interstitium. Our studies support the hypothesis of an infectious etiology for plasmacytoid leukemia, but the agent, perhaps an oncogenic virus, has yet to be detected.

Animals↗
PubMed1989

Impaired defense mechanisms in bay mussels, Mytilus edulis, with hemic neoplasia.

Immunocompetence of bay mussels, Mytilus edulis, with hemic neoplasia was investigated with an in vitro yeast phagocytosis assay and by in vivo clearance from the blood of injected Cytophaga sp. bacteria. The yeast phagocytosis assay was conducted with hemocytes maintained in 90% plasma. Neoplastic hemocytes, characterized by enlarged nuclei and scant cytoplasm, failed to phagocytose yeast cells. In contrast, greater than 90% of hemocytes from unaffected animals and morphologically normal hemocytes from mussels with the disease phagocytosed yeast. Substitution of normal plasma with that from a mussel with advanced disease (essentially 100% neoplastic hemocytes) did not affect the phagocytic capability of normal hemocytes. Conversely, normal plasma did not enhance the phagocytic capabilities of neoplastic cells. Mussels with advanced disease showed reduced bacterial clearance; control or lightly affected mussels (less than 11% neoplastic hemocytes) cleared greater than 90% of injected bacteria in 4 hr, while mussels with advanced disease cleared 44-83%. These experiments indicate that mussels with advanced hemic neoplasia have compromised defense systems. This may account for the reported mortality in mussels and other bivalve molluscs with hemic neoplasia.

Animal Diseases↗
PubMed1989

Prevalence of larval Anisakis simplex in pen-reared and wild-caught salmon (Salmonidae) from Puget Sound, Washington.

The abundance of parasites of public health significance in pen-reared salmon and wild-caught salmon was compared. Two hundred eighty-seven salmon from Puget Sound, Washington, were examined for third-stage larvae of Anisakis simplex. Of these fish, 237 Atlantic salmon (Salmo salar), coho salmon (Oncorhynchus kisutch) and chinook salmon (O. tshawytscha) were reared in commercial salmon pens and 50 sockeye salmon (O. nerka) were caught during their spawning migration. All wild-caught salmon were found to be infected with larval A. simplex; conversely, all pen-reared fishes lacked such infections. Edible musculature of wild salmon were infected with 581 (87%) nematode larvae. Of other salmon parasites known to infect humans, one Diphyllobothrium sp. plerocercoid was collected from each of three of the 50 wild-caught salmon. The study showed that farmed salmon may increase the margin of safety for consumers of raw seafood.

Animals↗
PubMed1988

Transmission of hemic neoplasia in the bay mussel, Mytilus edulis, using whole cells and cell homogenate.

Experimental studies with hemic neoplasia in the bay mussel indicated that the condition can be transmitted allogeneically with intact whole cells and cell-free homogenate. A differential pathogenesis of the disease in mussels receiving the two different inocula supports the argument that actual cell transplantation occurred. In addition to the first demonstration of the infectious nature of the disease with cell-free homogenates, it was also shown that the disease is transmitted by cohabitation. Remission of the disease occurred in some mussels indicating individual variation in recognition mechanisms.

Animals↗
PubMed1988

Fish infected with Sphaerospora spp. Thélohan (Myxosporea) from waters enzootic for proliferative kidney disease of salmonids.

Sphaerospores were found among three species of fish examined from waters known to be enzootic for proliferative kidney disease (PKD) of salmonids. They were detected in the renal tubules of both hatchery-reared rainbow trout (Salmo gairdneri) exposed to the infectious stage of PKD and in chubs (Gila bicolor) in the headwaters of a hatchery where PKD is enzootic. Sticklebacks (Gasterosteus aculeatus) collected near net pens where Pacific salmon had experienced a PKD epizootic were also found to harbor sphaerospores in the lumen of the kidney tubules. The latter two host species contained developmental stages of a myxosporidan in the blood and in the lumen of the kidney tubules which are similar to those of PKX, the causative agent of PKD in salmonid fish. The sphaerospores observed in the rainbow trout are the first to be observed in this species. The similarity to previously observed developmental stages, rarity, and presence of these sphaerospores in salmonid fish from a hatchery where PKD is enzootic suggest that they are the most mature stage of the PKX myxosporidan yet observed.

Animals↗
PubMed1988

Goussia girellae n. sp. (Apicomplexa: Eimeriorina) in the opaleye, Girella nigricans.

Goussia girellae n. sp. is described from the opaleye fish, Girella nigricans. Merogonic stages were observed in the apices of intestinal epithelial cells, in the lamina propria, and in extra-intestinal sites including liver, gills, and spleen. Gamonts were observed in the intestinal epithelial cells. Only unsporulated oocysts were detected in the intestine, and sporulation occurred when feces containing oocysts were incubated for 48 h in seawater at 21 degrees C. Oocysts are elongated (24.8 x 14.7 micron) with a wall about 200 nm thick and have no residuum, micropyle, or polar granule. Sporocysts are ellipsoid (8.5 x 4.5 micron), have a thin two-layered wall approximately 30 nm thick, and consist of two valves joined by a suture. Although moribund opaleye were also infected with Gyrodactylus sp., Cryptobia sp., Cardicola sp., and epitheliocystis organisms (chlamydia), all fish were heavily infected with G. girellae and morbidity was thus attributed to the coccidium.

Animals↗
PubMed1988

An internal X-cell pseudotumor in a black croaker (Cheilotrema saturnum).

Cells closely resembling X-cells were the primary cellular component of a large pseudotumor in the viscera of a black croaker (Cheilotrema saturnum). The fish was captured in coastal waters off San Diego, California and was maintained at the Scripps Aquarium. After 2 years in captivity the fish exhibited extreme abdominal swelling due to a visceral mass, which weighed approximately one-fifth the total body weight. The cells associated with the pseudotumor were identified as X-cells due to their great variability in size, vesicular nuclei which stained negative for DNA and their formation of a pseudotumor. This is the first report of an X-cell pseudotumor in the visceral cavity. We agree with the hypothesis that the X-cell is a protozoan, and the description here of X-cells in a visceral pseudotumor in a fish of the family Sciaenidae associates an additional type of lesion with this enigmatic parasite.

Abdominal Neoplasms↗
PubMed1987

An intranuclear microsporidium associated with acute anemia in the chinook salmon, Oncorhynchus tshawytscha.

An intranuclear microsporidium is described from hemoblastic cells of the chinook salmon, Oncorhynchus tshawytscha. The infection is associated with an acute anemia in the fish. Up to 47% of the hemoblast nuclei were infected in anemic fish. The organisms, found only in spleen and kidney tissues, were 1-2 microns in diameter and consisted of vegetative and early sporulation forms. This microsporidium differs from known species which parasitize fish in its tissue location; however, the absence of mature spores and other life cycle stages precludes determination of its precise taxonomic identity.

Anemia↗
PubMed1987

Effects of cortisol implants on the PKX myxosporean causing proliferative kidney disease in rainbow trout, Salmo gairdneri.

The myxosporean (PKX) that causes proliferative kidney disease in salmonid fishes is found primarily in the kidney interstitium of clinically affected fish, where it invokes a severe inflammatory response. Incomplete spores are observed in the lumen of kidney tubules in recovering fish. PKX-infected rainbow trout, Salmo gairdneri, were immunosuppressed with cortisol implants to determine if a reduction in renal interstitial inflammation would enhance the development of the parasite. Immunosuppression of these fish was indicated by high plasma cortisol levels, chronic mortality due to opportunistic pathogens, and depressed leucocrits when compared to infected fish not receiving cortisol implants. Cortisol-treated PKX-infected fish had 20 times the density of interstitial PKX compared with nontreated fish, but showed less interstitial inflammation. All of the former group examined at 4 wk postimplantation exhibited intraluminal sporogonic forms of PKX, whereas no sporogonic forms were detected in the nontreated fish. Suppression of the inflammatory response clearly enhanced the parasite's ability to reach the sporogonic stage, but did not induce complete development of the spore. Possibly the kidney tubules of rainbow trout do not provide the proper physiological environment for complete sporulation of PKX and a nonsalmonid fish may be the primary host.

Animals↗
PubMed1986

Henneguya exilis Kudo associated with granulomatous branchitis of channel catfish Ictalurus punctatus (Rafinesque).

Outbreaks of a chronic branchitis in channel catfish Ictalurus punctatus (Rafinesque) were observed on four fish farms throughout the state of California from November 1982 to April 1984. Severe granulomatous inflammation of the gill filaments with necrosis of the cartilage of the gill ray and diffuse epithelial hyperplasia, resulting in extensive fusion of gill lamellae, was present on histologic examination of gill specimens from 35 out of 44 fish examined. Numerous, small trophozoites morphologically consistent with presporogonic myxosporean parasites were consistently associated with the inflammatory process. Mature spores of Henneguya exilis Kudo were present in large numbers in gill specimens from two fish and only occasionally in 22 others. Similar cases referred to as "Hamburger Gill Disease" or "proliferative gill disease" have been known to occur in the south-central United States. This report describes the morphologic changes of this condition and discusses its possible pathogenesis.

Animals↗
PubMed1985

PKX, the causative agent of proliferative kidney disease (PKD) in Pacific salmonid fishes and its affinities with the Myxozoa.

Proliferative kidney disease (PKD), caused by an unclassified protozoan (PKX), is reported from Pacific salmon, Oncorhynchus tshawytscha (Walbaum) and O. kisutch (Walbaum), and steelhead trout, Salmo gairdneri Richardson, held at the Mad River Hatchery in California, USA. The cumulative mortality attributed to the disease was 95, 13, and 18% respectively. The mortalities were greatest at mean water temperatures of 12-14 degrees C during July 1983. The ultrastructure of the PKX organism and its associated pathology during clinical disease in all three species were consistent with those of the parasite in rainbow trout (Salmo gairdneri) as described in European outbreaks. Significant mortalities did not occur after August, at which time the parasite could no longer be detected in the salmon species. The steelhead continued to exhibit parasites in the kidney interstitium and epithelium and lumens of the tubules. Myxosporidan trophozoites and developing spores were also observed in the lumens of the kidney tubules of these fish. Although a mixed infection with another parasite may have occurred, evidence suggests that the myxosporidans are later stages of PKX. They were only observed in fish exposed to water with the infective stage and were particularly prominent in recovering fish. The PKX organism is similar to UBO, an unclassified protozoan of carp suspected to be an early stage of Sphaerospora renicola Dykovà & Lom. Both parasites infect the blood and kidney, divide by endogeny, and are released by disintegration of the primary mother cell. The intraluminal myxosporean forms show similarities to Sphaerospora spp. in that they are monosporous and sporoblasts are formed within pseudoplasmodia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Ortholinea alata n. sp. (Myxosporea: Ortholineidae) in the northern butterfly fish Chaetodon rainfordi.

Ortholinea alata n. sp. is described from the northern butterfly fish, Chaetodon rainfordi collected at Heron Island, Great Barrier Reef, Australia. Spherical, disporous trophozoites (10-15 micrometers) and spores were observed in the lumina of kidney tubules and collecting ducts. Spores are broadly triangular with two short, broad processes that extend dorsoventrad from the posterior end of each of the two spore valves. Valves are bisected by a suture in the plane of the polar capsules. Spores are 12.6 micrometers (length) x 9.6 micrometers (width) x 9.9 micrometers (length), and at the anterior end contain two spherical, divergent polar capsules measuring 4.6 (4.1-5.1) micrometers. Sporogenesis is similar to that of renal Sphaerospora spp.; the intraluminal trophozoites of O. alata n. sp. correspond to pseudoplasmodia described for Sphaerospora spp. and no large, multinucleated plasmodia are formed. No significant histopathological changes were observed in the kidneys of infected fish.

Animals↗