Lesions In Hamsters Research Articles

Brain lesions in hamsters induced with a herpes-like virus from Burkitt tumor cells: Sarah Stewart. Proc. Div. Microbiol. New York Acad. Sc

Brain lesions in hamsters induced with a herpes-like virus from Burkitt tumor cells: Sarah Stewart. Proc. Div. Microbiol. New York Acad. Sc

The induction of tumours and other lesions in hamsters by a single subcutaneous injection of 9,10-dimethyl-1,2-benzanthracene or urethane on the first day of life.

The induction of tumours and other lesions in hamsters by a single subcutaneous injection of 9,10-dimethyl-1,2-benzanthracene or urethane on the first day of life.

The epidemiology of dermal leishmansiasis in British Honduras Part III. The transmission of Leishmania mexicana to man by Phlebotomus pessoanus, with observations on the development of the parasite in different species of Phlebotomus

During 1960–1962 a study on the epidemiology of dermal leishmaniasis due to Leishmania mexicana in British Honduras revealed 18 species of Phlebotomus in the enzootic forest areas. In addition, 7 other sandflies remain to be identified and may represent new species. 9 species of Phlebotomus were found commonly to bite man. All were predominantly nocturnal in their feeding habits and, as they were readily infected with L. mexicana, all must be regarded as potential vectors in nature. The infection rates for sandflies fed directly on hamster lesions, at the periphery, and on normal adjacent skin were 95%, 48% and 0% respectively. Maintenance of wild-caught Phlebotomus species is discussed. Best results were obtained by keeping single flies in corked tubes containing a fresh green leaf. The corks had a groove cut throughout their length, to allow air exchange, and all tubes were kept in constant light and at approximately 100% relative humidity. 332 sandflies, including all the known man-biting species from British Honduras, were fed on the lesions of hamsters and mice infected with both human and rodent strains of L. mexicana. 52 flies were induced to re-feed on volunteers (8 fed a second time and 1 a third time), in all inflicting a total of 90 probes. Transmission of L. mexicana to man was achieved, by Phlebotomus pessoanus, on one occasion. This insect had fed on the infected hamster only 3 days and 23 hours previously. The development of L. mexicana in the insect host has been followed by a study of the gut contents and sections of entire sandflies which were fixed at 3, 6, 12, 24, 36, and 48 hours and 3–5 days after their infective feed. The development is to an anterior station, the leptomonads reaching the proboscis as early as 4 days after the infecting blood meal. 439 wild-caught female sandflies were dissected in an attempt to find insects naturally infected with L. mexicana. Flagellates were seen in the hind-gut of one specimen of P. ovallesi and others in the crushed gut from a single P. cruciatus (exact position in the gut uncertain). In the absence of animal inoculation the nature of these flagellates remains uncertain, but they are not thought to be leptomonads of L. mexicana. Attempts to demonstrate mechanical transmission of L. mexicana were made by interrupting sandflies feeding on hamster lesions and immediately allowing such insects to renew feeding on volunteers. No transmission was achieved and it is felt that such a mode of transfer plays little or no part in the transmission of the parasite in nature. On the contrary, the killing and squashing of infected sandflies feeding on human skin may well facilitate entry of the parasite. Although sandflies were successfully infected with L. mexicana after feeding on a newly acquired and non-ulcerative human lesion, man-to-man transmission is considered most unlikely in nature.

Natural infections of leptomonad flagellates in Panamanian Phlebotomus sandflies

In the search for vectors of leishmaniasis in Panama, over 5000 wild-caught Phlebotomus females were dissected and examined for leptomonad flagellates. Natural infections were found in 416 out of a total of 4861 females of six of the seven common man-biting species ( gomezi, panamensis, sanguinarius, shannoni, trapidoi, and ylephiletor). A single female longipalpis was also infected. None of 365 females of 13 other species which never or only occasionally bite man was infected. A total of 262 males, including 242 of common man-biting species, was negative. Leptomonad infections were found in sandflies from each of five endemic areas and in two others where human cases have not been reported. The over-all infection rate of the common man-biters was 8.5%, with rates varying from 1.9% for panamensis to 15.4% for trapidoi. During the rainy season, June through December, the over-all rate (10.6%) was much higher than during the dry season (4.1%). The source of these infections in unknown. However, the vertical distribution of species in simultaneous ground-level and tree-platform catches, together with differential infection rates, suggest that the reservoirs may be found among arboreal animals. Leptomonads were always present in the hindgut of infected females. They also occurred occasionally in the posterior part of the midgut (stomach), rarely in the anterior part (cardia), and only twice were they found in the foregut (esophagus and pharynx, respectively). In over 20% of the infections leptomonads occurred in the Malpighian tubules. In culture the morphology of leptomonads from the natural infections is consistent with that of Leishmania. Lesions produced in hamsters by two of the sandfly strains are indistinguishable from those produced by Panamanian human strains. In the sandfly gut the growth pattern and morphology of the leptomonads in natural infections are similar to those of sandflies fed on hamster lesions produced by both Panamanian human strains and a wild-caught sandfly strain.

Serologic evidence of infection with Eaton agent in lower respiratory illness in childhood.

THE agent isolated in cotton rats, hamsters or embryonated hen's eggs by Eaton et al.1 2 3 from patients with cold-agglutinin-positive atypical pneumonia has been the subject of considerable controversy. This agent could be propagated in embryonated eggs and produced pneumonic lesions in hamsters and cotton rats after intranasal inoculation. The results of neutralization tests in hamsters or cotton rats that suggested the development of antibody to this agent during convalescence from atypical pneumonia have not been accepted by certain workers since the challenge inoculum did not produce pneumonitis in all inoculated animals. In addition, the question of latent agents in cotton . . .

Melioidosis: pathogenesis and immunity in mice and hamsters. I. Studies with virulent strains of Malleomyces pseudomallei.

The pathogenesis of acute respiratory melioidosis mice and hamsters is described. Inhaled organisms giving rise to lesions seemed to be first engulfed by the mononuclear alveolar phagocytes, but in less than 1 day polymorphonuclear cells made their appearance. In spite of this defense reaction, the bacteria continued to multiply and their products caused focal necrosis. These foci enlarged and gave rise to septicemia, toxemia, and eventually death, which usually occurred in 3 to 10 days depending on the dose. Melioidosis, is, therefore, an acute septicotoxemic disease resembling plague and anthrax in this respect. In hamsters the disease process developed more rapidly than in mice and death occurred sooner. The course of the disease in hamsters was sometimes complicated by intraglomerular deposits resembling "fibrinoid," which were similar to those of the generalized Shwartzman phenomenon. This phenomenon may have been an indirect cause of both the perifocal hemorrhage and the extremely large number of bacteria in some of the hamster lesions. When low infecting doses of organisms were employed, mice, but not hamsters, developed a chronic type of disease, lasting 2 to 8 weeks. This was characterized by large abscesses in the spleen or lung, marked proliferation of mononuclear phagocytes and plasma cells, and increased immunity against reinfection (about 40-fold against respiratory challenge). When mice and hamsters inhaled high infecting doses of organisms, a peracute disease resulted with death in 1 to 3 days. Increased numbers of bacteria were observed in the lesions, and the histological changes in the spleen resembled those following the intravenous injection of Malleomyces pseudomallei toxin or the intramuscular injection of large doses of cortisone. These changes were characterized by a swelling of the phagocytes of the white pulp with nuclear debris. The peracute, the acute, and the chronic forms of melioidosis in mice are similar to analogous clinical forms found in man.

Strain variation in Entamoeba histolytica

1. Liver lesions were easily induced in hamsters with two strains of E. histolytica but not with six others.2. Serial liver passage increased the invasiveness to the rat's caecum of one strain which had become attenuated by in vitro cultivation.3. The invasiveness of one of the liver passage substrains was lost a second time after cultivation in vitro and a second series of liver passages restored some degree of virulence.4. Serial liver passage did not increase the invasiveness of two avirulent strains.5. The ease of production of amoebic liver lesions in hamsters is not correlated with invasiveness in the rat's caecum.

Ocular Lesions in Hamsters : With Chronic Toxoplasma and Besnoitia Infection

Ocular Lesions in Hamsters : With Chronic Toxoplasma and Besnoitia Infection

IV. Ineffectiveness of Certain Essential Nutrients in Prevention of Tooth Decay in Cotton Rat Molars

SummaryA variety of tests were made to determine if superabundant amounts of essential nutrients or optimal amounts of these nutrients from different sources would alter the initiation and development of carious lesions in caries-susceptible cotton rats after tooth development was almost complete. Negative results were obtained in all cases indicating that initiation and development of carious lesions in teeth formed before the beginning of the experimental period were not influenced by additional amounts of the known nutrients tested.The ration described by Keyes for production of carious lesions in hamsters resulted in very poor growth and a low rate of initiation and development of carious lesions in the cotton rat. A supplement of 8% dried brewer's yeast to the purified ration produced good growth and permitted a slight reduction in the dental caries experience of cotton rats.

STUDIES ON THE ETIOLOGY OF PRIMARY ATYPICAL PNEUMONIA

Experiments to determine the optimum conditions for propagation of the virus of atypical pneumonia in chick embryos are described. Variations in the activity of infected chick embryo material were investigated. The highest dilution of chick embryo suspension producing pulmonary lesions in hamsters and cotton rats is not over 10(-3). Dilutions of 10(-4) infect chick embryos. The virus is unstable at room temperature and also loses activity when stored in a dry-ice refrigerator unless the suspensions are kept in sealed glass tubes. Filtration experiments indicate a maximum particle size of 180 to 250 mmicro. The virus propagated in chick embryos produces pulmonary lesions in hamsters and cotton rats which have been immunized to their own non-bacterial agents inducing pulmonary lesions. Of these, the pneumonia virus of hamsters most frequently causes intercurrent respiratory infections, and methods of controlling epizootics due to this agent are described.

Effect of the Host in Action of Sulfonamides on Elementary-Body Agents of Murine and Feline Pneumonitis.

SummaryThe effect of sulfamerazine on pulmonary infections in mice, hamsters, rats, and cotton rats, and on yolk sac infections in chick embryos with the agents of murine and feline pneumonitis was studied. The drug inhibited the action of the mouse virus in all the species tested and was effective in very small doses, 0.0025 mg per gram of body weight in mice and somewhat larger doses, 0.1 mg/g, in hamsters. With the agent of feline pneumonitis, large doses of sulfamerazine, near the toxic limits, produced moderate inhibition of the lung lesions in hamsters and white rats, slight inhibition in cotton rats, and no effect in mice or chick embryos.