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Biomedical subjects

B R Miller

Publications and source records attributed to B R Miller.

At least 73 records · Page 4Linked to original sources
PubMed1988

Detection of yellow fever virus nucleic acid in infected mosquitoes by RNA:RNA in situ hybridization.

An in situ hybridization technique was developed for the strand-specific detection of yellow fever virus (YFV) RNA. An 35S-labeled, transcribed RNA probe was used to detect positive-sense polarity YFV genomic RNA in infected C6/36 (Aedes albopictus) cells, dissected mosquito tissues, and sections of plastic-embedded, YFV-infected Aedes aegypti mosquitoes. Mosquito tissues fixed in buffered Formalin retained morphological integrity. The low concentrations of probe used yielded high specific signal on infected specimens and low background signal on uninfected specimens.

Animals↗
PubMed1988

Microinjection of DNA into Aedes triseriatus ova and detection of integration.

A technique was developed for microinjection and transformation of Aedes triseriatus mosquitoes. Mosquito ova can be readily microinjected with approximately 0.9 nl of inoculum if desiccated and inoculated before hardening of the chorion. Ova were injected with molecular constructs that conferred antibiotic (G418) resistance to larvae. Insertion of the antibiotic resistance construct into the mosquito genome was demonstrated by Southern blot analysis.

Aedes↗
PubMed1988

Biological characterization of plaque-size variants of yellow fever virus in mosquitoes and mice.

We isolated plaque-size variants of a South American strain of yellow fever virus, and compared their ability to infect orally and be transmitted by vector Aedes aegypti mosquitoes with that of the uncloned, parental virus. We analyzed the same clonal isolates in mouse virulence experiments. No significant differences could be demonstrated in the capacities of the variants to infect and be transmitted by mosquitoes or in mouse virulence tests. The 17D vaccine virus (derived from the African Asibi strain) was, however, markedly attenuated in mosquitoes; also, a variant virus (Asibi strain) derived by continuous passage in HeLa cells (and attenuated for monkeys and mice) was markedly attenuated in mosquitoes when compared with its parent virus. The results suggest that vector competence and mouse virulence are similar in plaque-size variants of the South American strain of yellow fever virus. However, if vigorous and appropriate selection pressures are applied (as established by the derivation of the 17D vaccine and HeLa passaged viruses), attenuated variants can be discovered; their role and prevalence within a virus population in nature is unknown.

Aedes↗
PubMed1988

Oral atropine premedication in infants attenuates cardiovascular depression during halothane anesthesia.

The efficacy of oral atropine premedication in attenuation of the cardiovascular depression associated with halothane anesthesia has not been previously evaluated. A solution containing either oral atropine 0.04 mg/kg (HI), 0.02 mg/kg (LO), or a placebo (NO) was randomly administered to 36 infants 1-6 months old and 36 infants 7-15 months old 30-90 minutes before induction of anesthesia. The onset of action of atropine was approximately 25 minutes after administration as determined by a 15% increase in heart rate (HR) above baseline levels. Heart rate, systolic blood pressure (SBP), and mean arterial blood pressure (MAP) were then measured at 1-minute intervals starting just before induction of anesthesia and continuing until onset of surgical stimulation during anesthesia with halothane (up to 3%), nitrous oxide (60%), and oxygen (40%). In infants 1-6 months old, either dosage of oral atropine preserved HR and SBP as compared with placebo. In infants 7-15 months old, either dosage preserved HR but not SBP. The severity of hypotension was greatest in infants 1-6 months of age given placebos. No significant differences existed between oral atropine 0.04 mg/kg or 0.02 mg/kg in either age range. It is concluded that premedication with oral atropine 0.02 mg/kg is effective in attenuating the cardiovascular depression associated with halothane anesthesia in infants.

Administration, Oral↗
PubMed1987

Vector competence of Aedes albopictus from Houston, Texas, for dengue serotypes 1 to 4, yellow fever and Ross River viruses.

A combination of virus infection and transmission experiments showed that a Houston, Texas strain of Aedes albopictus is a competent vector for dengue (DEN), yellow fever (YF) and Ross River (RR) viruses. However, at 14 days incubation, DEN virus infection rates in a Puerto Rican strain of Aedes aegypti were significantly higher for each of the four DEN serotypes, except DEN-1, than in Houston Ae. albopictus fed simultaneously on the same virus suspensions. The degree of correlation between disseminated DEN infection rates in Houston Ae. albopictus and transmission to an in vitro system ranged from 42 to 88% for the four DEN serotypes. No significant difference was noted in YF virus infection rates or transmission rates in the two mosquito species fed on the same virus suspensions and incubated for the same time period. Also, RR virus infection and transmission rates in Houston and Hawaiian strains of Ae. albopictus were generally comparable.

Aedes↗
PubMed1986

Passage of yellow fever virus: its effect on infection and transmission rates in Aedes aegypti.

The effect of successive lytic passage of yellow fever virus on mosquito infection and transmission rates in the vector, Aedes aegypti, was determined. Three strains of yellow fever virus from Trinidad and Peru were passaged five times in suckling mouse brains and seven times in BHK-21 cells. Mosquitoes were fed meals containing passaged and unpassaged viruses and infection and transmission rates were compared. Rates were similar for all but one of the three virus strains grown in both substrates with the exception of virus strain 1899/81 (human isolate from Peru) passaged seven times in BHK-21 cells. Infection rates declined from 62% (109/177) to 35% (61/176), and transmission rates declined from 64% (60/94) to 45% (22/49). The oligonucleotide fingerprint of strain 1899/81 passaged seven times in BHK-21 cells shared 98% (45/46) of its large, T1-resistant oligonucleotides with the parent strain, indicating limited biochemical differences. The data suggest that uncloned yellow fever virus populations, passaged a limited number of times, and exhibiting some phenotypic changes, are representative of the original virus strain and can be used with a reasonable degree of confidence in vector competence studies.

Aedes↗
PubMed1985

Intracerebral hemorrhage with rapid recovery.

Occasionally, patients with small supratentorial intracerebral hemorrhages exhibit the sudden onset of neurologic deficits, followed by rapid improvement during the next several days. We analyzed the computed tomographic (CT) and clinical features of a group of nine such patients, who were drawn from a series of 120 patients with intracerebral hemorrhage. The temporal pattern of illness was similar to that of a cerebral ischemic event, but the correct diagnosis of intracerebral hemorrhage was made on the basis of the CT findings.

Adult↗
PubMed1985

Oral infection of Aedes aegypti with yellow fever virus: geographic variation and genetic considerations.

Twenty-eight populations representing a worldwide distribution of Aedes aegypti were tested for their ability to become orally infected with yellow fever virus (YFV). Populations had been analyzed for genetic variations at 11 isozyme loci and assigned to one of 8 genetic geographic groups of Ae. aegypti. Infection rates suggest that populations showing isozyme genetic relatedness also demonstrate similarity to oral infection rates with YFV. The findings support the hypothesis that genetic variation exists for oral susceptibility to YFV in Ae. aegypti.

Aedes↗
PubMed1985

Experimental studies on the replication and dissemination of Qalyub virus (Bunyaviridae: Nairovirus) in the putative tick vector, Ornithodoros (Pavlovskyella) erraticus.

A study was undertaken to determine if the argasid tick, Ornithodoros (Pavlovskyella) erraticus, can serve as a biological vector of Qalyub (QYB) virus. The suckling mice used as viremic vertebrate hosts were acceptable hosts for all feeding stages of this tick and developed relatively high titered viremias (4.4-6.5 log10PFU/ml) 24-120 hr post intracerebral inoculation. Larval, nymphal, and adult ticks became orally infected with QYB virus after ingesting 4.4-6.4 log10PFU/ml. The overall infection rate for all experiments was 67/205 and virus was recovered up to day 179 postfeeding. Incubation of known quantities of QYB virus with uninfected triturated tick tissues did not result in any appreciable virus inactivation. QYB viral antigen was detected by immunofluorescence primarily in the tick midgut posterior diverticula cells. First and second instar nymphs orally infected as larvae did not individually transmit QYB virus to suckling mice; however they successfully transmitted the virus when feeding in groups of 11-20 per mouse. Three out of fourteen of the orally-infected male and female ticks individually transmitted QYB virus orally to suckling mice. Organ titrations of ticks orally exposed to QYB virus demonstrated virus primarily in midgut tissues; dissemination to other organ systems was discovered in only 1 tick after 142 days extrinsic incubation. Vertical transmission of virus from infected female ticks to progeny was not demonstrated. Four of the 39 ticks in our colony were infected with a spirochete; presumably, Borrelia crocidurae. O. (P.) erraticus apparently satisfies the conditions that would implicate this species as a biological vector of QYB virus and is the only known arthropod from which this virus has been isolated in nature.

Animals↗
PubMed1984

Mutations affecting functions of the Drosophila gene glued.

Glued mutations in Drosophila comprise an essential complementation group with complex developmental effects. The original Glued mutation (Gl) has dominant nonlethal effects in heterozygous flies, principally on the morphogenesis of the visual system. Gl also has a recessive lethal effect early in development. Mutations that reverse the dominant visual effects of Gl (GlR mutations) were induced by gamma-radiation or by insertions of the transposable P element. The GlR(G) mutations induced by gamma-radiation do not reverse the lethal effect of Gl; these appear to be null mutations, some of which (and possibly all) delete segments of the Glued region. The GlR(P) mutations induced by insertion of the P element also reverse concomitantly a recessive lethal effect of Gl, suggesting that both the recessive and dominant effects are controlled by the same gene. The reversal of a lethal effect of Gl by the P element is remarkable, since it indicates that an essential gene function can be restored by insertion of unrelated DNA. Another class of lethal Glued mutations was induced in the normal Gl+ strain by ethyl methanesulfonate (EMS). The EMS mutations belong to the same essential complementation group as Gl, but do not have the strong dominant effects of Gl on the visual system. The GlR(P) mutations provide a molecular marker for the Glued gene, which was used to map the gene to the 70C2 band of chromosome 3L by in situ hybridization of a P element probe to polytene chromosomes from the GlR(P) strains and also to isolate clones of Glued genomic DNA for molecular studies of the normal gene and the various Glued mutations.

Animals↗
PubMed1984

Arthropod studies with rabies-related Mokola virus.

A cell culture-adapted variant of the rabies-related Mokola virus was demonstrated to replicate in inoculated Aedes aegypti mosquitoes. Replication was slow compared to many arboviruses in their vectors. Maximum titers were not obtained until after approximately 6 weeks of extrinsic incubation. Mokola virus underwent nine mosquito-mosquito passages at approximately monthly intervals and was thus maintained in insects for 340 days before terminating the study. Virus antigen was detected by immunofluorescence in a variety of mosquito tissues and organs, including salivary glands, but primarily in nervous tissue. Irrefutable virus transmission by bite could not be demonstrated because of equivocal results. Transovarial passage of virus was observed in the mosquito. Viremia in baby mice was demonstrable. Ornithodoros moubata nymphal ticks were exposed to viremic mice but failed to become infected.

Aedes↗