Search PubMed⌕ Search

Biomedical subjects

J F Bell

Publications and source records attributed to J F Bell.

At least 55 records · Page 3Linked to original sources
PubMed1979

Resistance to tick-borne Francisella tularensis by tick-sensitized rabbits: allergic klendusity.

Mammals become hypersensitive to ticks that feed upon them. That hypersensitivity was thought responsible for an observation that a large number of Francisella tularensis-infected Dermacentor variabilis failed to infect a rabbit previously exposed to ticks of that species. In a series of tests of that hypothesis, rabbits sensitized to ticks were often significantly more resistant than control animals to tick-borne tularemia. The conditions that determine the klendusity are thought to be variable and complex but the phenomenon must be of importance in the epidemiology of some arthropod-borne agents.

Animals↗
PubMed1978

The continuing imperatives of diversity of rabies vaccine.

Current preoccupation with and enthusiasm for the human diploid cell rabies vaccine are reminiscent of the advent of duck embryo vaccine (DEV) a quarter of a century ago. Development of the latter vaccine, considered both potent and entirely safe at the time, had the effect of paralyzing development of other vaccines, at least in the United States. Subsequent experience has demonstrated the DEV is neither potent nor entirely safe, although its use is not attended by the trepidation that accompanied the use of older vaccines. Availability in the USA of only one vaccine licensed for human use has created a hardship on both patients and physicians in as much as a large percentage of vaccinated persons suffer side effects of various degrees that pose problems for continuation of treatment. Experience has shown that most of those problems can be resolved by simple substitution of vaccine of another kind. Data obtained thus far indicate the marked superiority of diploid cell vaccine over DEV in several respects but it is not yet evident that it is completely free of allergen. Moreover, purified preparations of antigenic fractions have been obtained, and other vaccines have been shown to benefit, in apparent potency, from their capability of eliciting interferon formation. Economic considerations cannot be overlooked, and the advantage, in this respect, of suckling mouse brain vaccine in some areas of greatest need is evident.

Humans↗
PubMed1978

Enigmatic resistance of sheep (Ovis aries) to infection by virulent Francisella tularensis.

Tularemia in range sheep is an occasional cause of severe economic loss from mortality and unthriftiness as well as a hazard to persons in contact with the animals. Epizootics are unpredictable and explosive, therefore, prophylaxis is more practical than therapy. Live vaccine of proven value in man and in beavers was inoculated into mature ewes and elicited antibodies without harm to the sheep. However, challenge of immunity was not possible because virulent Francisella tularensis in large doses did not cause significant mortality in healthy, well managed, unimmunized sheep. Evidence suggests that a complex of stresses such as inclement weather, lambing and concomitant ectoparasitism render sheep more susceptible to tularemia.

Animals↗
PubMed1977

Differences in efficiency of protective effect caused by high ambient temperature in mice infected with diverse substrains of rabies virus.

We have shown previously that a non-fatal outcome of infection with street rabies virus occurs more often when mice are exposed to a high ambient temperature (HAT = 35 degrees C) early in the course of the infection. To determine what influence the virus strain had on this protective effect of HAT, we have extended these observations to studies of a fixed rabies strain, CVS and several substrains of CVS virus derived from temperature-sensitive (ts) mutants. In all cases, mortality was reduced to some extent by exposure of the animals to HAT; however, dramatic strain-specific differences in the extent of the effect were noted. Although each of the virus substrains tested was revertant in the ts character (as tested in vitro using a non-permissive temperature of 40-5 degrees C), several substrains (ts 1, ts 4, RT51) caused disease that was sensitive (greater than 90% reduction in mortality) to HAT. Mortality induced by the parental CVS virus was reduced approx. 50% at HAT. A single CVS virus substrain, VSW89, caused disease that wal less affected by HAT than was disease induced by the parental strain. As in previous studies with street virus, the incubation periods for infection with CVS virus substrains were consistently prolonged at HAT.

Animals↗
PubMed1977

Antibody response to rabies virus in Syrian hamsters.

Syrian hamsters were injected with inactivated, attenuated, and virulent rabies virus (RV), and the antibody response was quantified by a neutralization test and the immunoglobulin class of the virus antibody was characterized by indirect fluorescent microscopy. Serum antibodies to RV were found to be predominantly of the immunoglobulin G2 (IgG2) class, although IgG1 anti-RV also were detected in high-titered sera obtained after secondary challenge. Brain extracts of hamsters inoculated intracerebrally with RV contained only IgG2 anti-RV. IgA and IgM anti-RV were not detected. The preferential IgG2 response to RV is in marked contrast to the isolated IgG1 response detected after inoculation of hamsters with soluble purified protein antigens.

Animals↗
PubMed1975

Chronic shedding tularemia nephritis in rodents: possible relation to occurrence of Francisella tularensis in lotic waters.

Contamination of streams by Francisella tularensis, a fastidious pathogen, was discovered by Miller in Russia. Subsequently that contamination was found to be the source of extensive human outbreaks, and to occur as well in North America. Circumstantial evidence supports a hypothesis that infected voles are responsible for the contamination, but when freshly isolated F. tularensis palaearctica is inoculated parenterally, only acute illness and death result whereas long-term contamination of streams would seem to demand a more chronic process. Laboratory studies have demonstrated that voles have an apparent predilection to tularemic nephritis when partially immunized before parenteral infection, but also when naive voles are infected orally. Associated chronic bacteriuria would seem to fulfill requirements for protracted contamination of watersheds.

Animals↗
PubMed1975

Non-fatal rabies in dogs and cats.

Serological studies were performed in 1,015 dog brains and 144 cat brains collected in a rabies enzootic area. Significant levels of rabies virus neutralizing activity were observed in two dog brains and in one cat brain which had been negative for rabies by immunofluorescence and mouse inoculation tests. These results were compared with those obtained in the group of surviving animals at different times after onset of experimentally induced abortive rabies. The possibility that naturally infected animals recovered from rabies central nervous system infection is suggested.

Animals↗
PubMed1974

Effects of high ambient temperature on various stages of rabies virus infection in mice.

Effects of high ambient temperatures on various stages of rabies virus infection have been studied. Ambient temperature increased within the tolerated range was found to have little effect upon body temperature of normal mice, but caused marked elevation of temperature during illness. Temperatures at onset of patent illness in mice were lower than normal. Increased body temperature in the higher thermic ambience during the incubation period was associated with decreased mortality and frequent abortive infections. Exposure to high ambient temperature late in the incubation period delayed onset of illness, decreased mortality, and increased frequency of abortive infections, but exposure to high ambient temperature after onset of patent illness did not affect the course of the disease.

Animals↗