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Biomedical subjects

R P Hanson

Publications and source records attributed to R P Hanson.

At least 37 records · Page 2Linked to original sources
PubMed1976

Experimental chlamydiosis in wild and domestic lagomorphs.

Chlamydia psittaci (strain M56, the agent of epizootic chlamydiosis of muskrats and hares) was highly lethal for the snowshoe hare (Lepus americans) following intravenous inoculation, whereas the agent was much less virulent for cottontail (Sylvilagus floridanus) and albino domestic rabbits (Oryctolagus cuniculus). Tissue titres of strain M56 were generally higher after 96 hr in the snowshoe hare than in tissues of the other lagomorphs. Spleen, liver and bone marrow were apparently the chief sites of primary multiplication of strain M56 in the hare. Virulence appeared to be very host specific in that only strain M56 among the six chlamydiae tested was highly lethal for the snowshoe hare.

Animals↗
PubMed1976

Transmissible mink encephalopathy. Reduced spongiform degeneration in aged mink of the Chediak-Higashi genotype.

Mink which are 18 months or older and are dying of transmissible mink encephalopathy (TME) have been found to have a marked reduction in spongiform degeneration of the brain if they are homozygous for the Aleutian gene and thus exhibit the autosomal recessive disorder known as the Chediak Higashi (CH) syndrome. CH mink younger than 1 year, and young or old non-CH mink have a typical lesion profile with widespread microvacuolation of the neuropile. Whereas aged CH mink have reduced spongiform degeneration at both the light and electron microscopic level, there is no other apparent alteration in the TME disease process. The length of incubation, clinical signs, astrocytic response, and brain concentration of the TME agent are comparable to those seen in non-CH mink. We conclude that spongiform degeneration is a secondary change in TME and speculate that vacuolation may be the result of lysosomal enzymes causing an increase in ganglioside catabolism.

Age Factors↗
PubMed1976

Newcastle disease. Environmental and host influences on immunity induced by non-parenteral vaccination.

Many millions of doses of Newcastle disease vaccine have been given to chickens by two non-parenteral routes; in aerosols and in drinking water. These vaccines, that reach either or both the respiratory and digestive tracts, have afforded protection against disabling disease for millions of chickens but not without irregularity in the adequacy and duration of the response induced. Among the factors that affect the response are the nature of the delivery system (i.e. aerosol particle size), the dose received, the time involved in delivery, the environmental circumstances (i.e. ambient temperature) and the precondition of the host from the withholding of feed and water and from handling and crowding. The site of initial replication is critical, presumably because by inducing nonspecific or specific blockage of other replication sites, it shapes the immune response. Most events in the development of a vaccine-induced infection are dependent upon both thresholds and inherent periodicities. Individual host responsiveness is an interplay between the virus, environmental factors and intrinsic systems of the host.

Administration, Oral↗
PubMed1975

Transmissible mink encephalopathy: infectivity of corneal epithelium.

Corneal epithelium from hamsters dying of transmissible mink encephalopathy contained a virus titer of 10-4.8 times the 50 percent lethal dose (10-4.8 LD50) per 0.05 milliliter when assayed as a cell suspension derived directly from the infected animal. After one passage in tissue culture, an equivalent concentration of cells contained only 10-0.8 LD50 per 0.05 milliliter.. It is concluded that corneal tissues are infectious; the infectivity may be mainly associated with free nerve endings. However, the most important immediate inference is that corneas from human beings affected with Creuzfeldt-Jakob disease are likely to be lethal if transplanted to healthy recipients.

Animals↗
PubMed1975

Transovarial transmission of LaCrosse virus in Aedes triseriatus.

As part of a continuing investigation on the ecology of LaCrosse virus in Wisconsin, field and laboratory studies were conducted to explore the possibility that the virus is transmitted transovarially in A. triseriatus mosquitoes. In laboratory experiments, A. triseriatus mosquitoes were infected by ingesting LaCrosse virus in defibrinated blood. LaCrosse virus was recovered from F1 eggs, larvae, and adults that originated from the infected parent mosquitoes. In a subsequent field study aimed at determining if transovarial transmission accounted for the survival of LaCrosse virus during the winter season, larvae that originated from overwintering A. triseriatus eggs were collected from a LaCrosse virus enzootic area in southwestern Wisconsin. LaCrosse virus was isolated from these larvae and from adult A. triseriatus that were reared from field-collected larvae. These findings strongly imply that A. triseriatus is the reservoir of LaCrosse virus and that transovarial transmission is the mechanism responsible for the maintenance of the virus during the winter season in the north central region of the United States.

Aedes↗
PubMed1975

Effects of bile and gastrointestinal secretions on the infectivity of Newcastle disease virus.

Bile aspirated from chicken gall bladders was found to contain substances neutralizing Newcastle disease virus (NDV). Nonspecific factors were present in the bile, probably the bile acids, which caused a reduction in the infectivity of the virus. Specific anti-NDV activity was found in the bile of birds that had been vaccinated with a lentogenic strain, Ulster, and challenged with a velogenic, viscerotropic strain, California 1083. Immunoglobulins were also found in these secretions and demonstrated to include the immunoglobulin A class as well as immunoglobulin G. Variability in the neutralizing capacity of bile was found with two different plaque clones of strain 1083, indicating antigenic heterogeneity in the viral population. No difference was found between bile from uninfected birds and the bile from NDV-immune birds in their activities against influenza strain Turkey Ontario 7732, whereas activity existed against a non-viscerotropic strain of NDV, Texas GB. These findings suggest that the specific activity of the secretions was most probably due to the presence of secretory antibody. The importance of the antiviral substances present in the alimentary tract was discussed with respect to the protection of the chicken against the viscerotropic pathotype of NDV.

Animals↗
PubMed1975

Intrauterine infection of mice with St. Louis encephalitis virus: immunological, physiological, neurological, and behavioral effects on progeny.

Intravenous injection of pregnant mice with St. Louis encephalitis (SLE) virus at 8 days of gestation resulted in infection of the fetus. Progeny developed no antibody or tolerance to SLE virus since the viral antigen was cleared by maternal antibody before antibody-forming competence developed in the young. Temporary growth retardation was observed in a number of young at 3 weeks of age. After the initial setback the growth rate increased, indicating that early runting was due to an inability to adjust adequately to extrauterine life, which was subsequently overcome. In most other young there were no significant effects on growth, reproduction, or life expectancy. A few young died at or shortly after birth; in these, neurological changes ranging from gross defects such as encephaloceles and hydrocephalus to histological evidence of necrosis and congestion were observed. Neurologically related behavioral changes were detected by using the open field test and the rotating-rod test, which indicated neurological damage and memory impairment in the surviving intrauterinely infected animals.

Animals↗
PubMed1975

Isolation of La Crosse virus (California encephalitis group) from the chipmunk (Tamias striatus), an amplifier host.

La Crosse (LAC) virus was isolated from the blood of seven chipmunks (Tamias striatus) captured during the summer of 1970 in southwestern Wisconsin. With the exception of the original isolate obtained from human brain after fatal encephalitis, these represent the first known isolations of LAC virus from a naturally infected free-living vertebrate. The chipmunks were trapped and periodically recaptured in two study areas where 59 chipmunks became infected and developed neutralizing antibody during the summer cycle of virus transmission. All isolates were obtained from blood samples collected within a 7 week period between 11 July and 23 August, and all were from seronegative chipmunks; 6 of these were recaptured and found to be seropositive 2 to 3 weeks later. The isolates proved identical to each other in comparative micro-neutralization tests using BHK21 cell cultures and immune chipmunk serum or hyperimmune mouse ascitic fluids. Neutralization tests showed the isolates to be different from snowshoe hare, trivittatus, and Jamestown Canyon prototype virus strains but indistinguishable from the LAC prototype. Findings demonstrate multiplication and transmissibility of LAC virus in a naturally infected host and are consistent with the thesis that chipmunks are important amplifying hosts for LAC virus and that Aedes triseriatus mosquitoes serve as vectors in transmitting their infections. Ecological significance of the findings are discussed in regard to current perspectives.

Aedes↗
PubMed1975

Newcastle disease virus antigens and strain variations.

Study of antigenic differences among strains of Newcastle disease virus is complicated by the presence in most field isolates and strains of several genetically distinct plaque populations, and by differences in avidity (reactions to antibody) among Newcastle disease viruses. Kinetic neutralization tests were used to demonstrate antigenic differences among 3 plaque clones of velogenic viscerotropic Newcastle disease viruses recently isolated from 3 avian species. The 3 viruses could be distinguished on the basis of plaque structure and hemagglutinin and neuraminidase activity. Antigenic differences among these viruses distinguished them from older, well characterized Newcastle disease viruses.

Animals↗
PubMed1975

Selection for plaque variants of two California group arboviruses (Jamestown canyon and La Crosse) by passage in natural vertebrate hosts.

The plaque size and distribution of prototype La Crosse (LAC) and Jamestown Canyon (JC) viruses were investigated in Vero cell cultures. The effect of serial passage of the viruses in their natural vertebrate hosts - the chipmunk and grey squirrel for LAC and the white-tailed deer for JC virus - was studied. Prototype JC virus was predominately a pinpoint plaque type (about 0.3 mm in diameter). A large plaque variant (about 1.0 mm in diameter), which was only 1 percent of prototype JC virus, increased to over 80 percent of the resultant virus after one passage in white-tailed deer. The large plaque type (about 1.0 mm in diameter) also predominated in JC isolates from mosquitoes, biting flies, and a white-tailed deer in Wisconsin. Prototype LAC virus consisted of a variety of plaque sizes, ranging in diameter from 0.3 mm to 3.0 mm. Passage through chipmunks increased the mean plaque diameter almost twofold, whereas passage in the grey squirrel resulted in a more uniform small plaque population practically eliminating the largest plaques. Preliminary results suggest that the resultant viruses are antigenically different. If these selective processes occur in nature, they man explain how four serologically related California group arboviruses with distinct vector-host cycles in nature could have evolved and have sympatric distribution.

Animals↗
PubMed1974

Microculture plaque neutralization test for California group arboviruses.

A microculture plaque neutralization test is described for California-group arboviruses that is as precise and quantitative as the standard test conducted in 60-mm petri dishes. It was shown that there was no significant between-panel or between-day variation in determinations and that a single pipette could be used for all serum-dilution levels within a titration without inoculum carry-over effect. The experimental protocol and statistical methods used produce 50% neutralization end points that meet the assumptions of parametric statistics. This permits the power and versatility of the analysis of variance to be exploited in testing for treatment effects in serological and immunological studies with viruses.

Analysis of Variance↗
PubMed1974

Influence of sex and age on natural resistance to St. Louis encephalitis virus infection in mice.

A difference was observed in susceptibility of adult male and female mice to St. Louis encephalitis (SLE) virus as measured by the death rate after intravenous challenge. Female mice that had susceptibility similar to that of males at 2 months of age had increased resistance to SLE virus at 3 and 4 months of age. The increased resistance occurred after sexual maturity, indicating that the resistance factor possibly was related to an aging process in the female. The susceptibility of male mice remained unchanged over the 2- to 4-month period. Neither pregnancy nor castration had any effect on resistance of adult mice to St. Louis encephalitis virus.

Age Factors↗
PubMed1974

Scrapie and transmissible mink encephalopathy: search for infectious nucleic acid.

Brain preparations from animals with scrapie or transmissible mink encephalopathy were phenol extracted and examined for the presence of pathogenic nucleic acid. Animals inoculated with various extracts remained healthy, and analysis on 2.6 to 5% polyacrylamide gels failed to detect a difference in extractable RNA species between infected and normal mink brain.

Animals↗
PubMed1974

Observations on a natural cycle of La Crosse virus (California group) in Southwestern Wisconsin.

Ecological studies were conducted to document the role of the eastern chipmunk (Tramias striatus) as a vertebrate host for La Crosse (LAC) virus in nature during late summer when Aedes triseriatus mosquitoes are most abundant. Movement, home range and density of chipmunk populations were determined by trap mark and recapture techniques on grid study areas. The temporal distribution of A. triseriatus was estimated by use of oviposition traps. Passive antibodies were found in spring-born juveniles captured prior to mid-July and in summer-born juveniles in September. Active antibodies neutralizing LAC virus were first detected in susceptible chipmunks in mid-July and 68 free-living and 4 sentinel animals developed antibodies during the study. Virus transmission continued at a high rate through August but was not detected in September. Chipmunk habitat was ranked for quality and populations of chipmunks. A. triseriatus were more abundant in study areas with most suitable chipmunk habitat. Populations of A. triseriatus were temporally associated with the elaboration of antibodies in chipmunks. In one study area, antibody prevalence rates in adult and spring-born juveniles reached 100% by September. Findings implicate A. triseriatus as the vector and establish chipmunks as important amplifying hosts in discontinuous foci of virus transmission.

Aedes↗