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Biomedical subjects

J L Hardy

Publications and source records attributed to J L Hardy.

At least 73 records · Page 4Linked to original sources
PubMed1985

Effect of normal mosquito extracts upon arbovirus recoveries from mosquito pools.

Titers of Turlock (TUR) and Hart Park (HP) viruses were reduced to undetectable levels when virus was mixed with a triturated suspension of uninfected (normal) 4th instar larvae of Culex tarsalis prior to plaque assay in cell culture. There was a linear relationship between the number of larvae in the pool and the titer of virus recoverable. Virus was undetectable when 1,000-10,000 PFU of either agent was added to pools that contained 25 or more larvae. Suspensions of up to 25 adult male or female Cx. tarsalis had little effect on detectable viral titers while pupal suspensions had an intermediate effect. The inhibitory effect of normal larval extracts on viral infectivity could be counteracted by use of polycations or a high pH buffer. A similar reduction in titer of TUR virus was observed with extracts of larvae of Aedes melanimon or Anopheles franciscanus. Larval extracts of Cx. tarsalis similarly reduced titers of California and St. Louis encephalitis viruses but not western equine encephalomyelitis virus. These findings may have significant bearing on the interpretation of transovarial transmission attempts in which pooled larvae are assayed for virus.

Aedes↗
PubMed1984

Host-dependent mutants of Sindbis virus whose growth is restricted in cultured Aedes albopictus cells produce normal yields of virus in intact mosquitoes.

Two host-dependent (hd), temperature-sensitive (ts) mutants of Sindbis virus (SV), clones 35 and 58, which are restricted in their ability to grow at 34 degrees in cultured Aedes albopictus cells [K.J. Kowal and V. Stollar (1981). Virology 114, 140-148] were not restricted in their ability to grow at 28-34 degrees after intrathoracic inoculation of Ae. albopictus, Ae. dorsalis, Ae. epactius, Anopheles freeborni, and Culex tarsalis mosquitoes. Compared to standard SV (SVSTD), the growth of SV clone 35 was somewhat restricted in parenterally infected C. pipiens females. Titers of SVSTD and the two mutants were modulated to relative low levels by some Ae. albopictus and Ae. dorsalis females after 192 hr incubation at 34 degrees but not at 28 degrees, suggesting that under some conditions mosquitoes have the ability to control the replication of SV. The hd and ts phenotypes of SV mutants were retained during growth at 31 degrees for 36 hr and 72 hr in Ae. epactius and Ae. dorsalis females, respectively, and at 28 degrees or 34 degrees for 192 hr in Ae. albopictus females. The demonstration that mutant viral clones, which are restricted in cultured mosquito cells, can produce normal yields of virus in intact mosquitoes indicates that considerable caution must be exercised in extrapolating results obtained with cultured cells to the level of the intact organism.

Aedes↗
PubMed1984

Alkaline phosphatases of the mosquito, Culex tarsalis Coquillett.

Spectrophotometric and isoelectric focusing (IEF) electrophoretic characterization of the alkaline phosphatase (ALKP) of the mosquito, Culex tarsalis, are presented. With p-nitrophenylphosphate (Pnp) as substrate, ALKP was optimally active at 37 degrees C, pH 8.0, 30 mM MgCl2, Vmax was 35.8 mumoles/10 min and the Km was 5.7 mM, with no demonstrable requirement for Zn2+. The spectrophotometric enzyme(s) was stimulated by dithiothreitol, 2-mercaptoethanol, and poly-vinylpyrollidone (PVP); inhibited by NaF, several alternative cations (Ca2+, Ba2+, Fe2+, Cu2+), and EDTA. ALKP activity was cyclic during the 15 day post-adult emergence period of the study. No significant differences were noted between the specific activities of males and females. IEF electrophoresis revealed 6 ALKP isozymes detected with alpha-naphthylphosphate within the pH range 4.0-5.5, with a second group of 3 rather indistinct species in the pH 6.0-7.0 range. IEF ALKP isozymes were stimulated by Mg2+ and PVP and inhibited by EDTA (except ALKP5.0) and cysteine; partial inhibition with phenylalanine. IEF detection of ALKP activity with Pnp indicated that the majority of the activity was localized in the pH 4.0-5.5 range, in close agreement with the alpha-naphthylphosphate results.

Alkaline Phosphatase↗
PubMed1984

Experimental transovarial transmission of St. Louis encephalitis virus by Culex and Aedes mosquitoes.

Colonized and field-collected female Culex tarsalis, infected with St. Louis encephalitis, (SLE) virus by intrathoracic inoculation or by feeding on a viremic host, transmitted virus to their F1 adult and/or larval progeny when reared at 18(+/- 1) degree C but not when reared at 27(+/- 1) degrees C. The minimal infection rates (MIR) for different populations of Cx. tarsalis ranged from 1:32 to less than 1:250 (mean = 1:121) for larval progeny and from 1:32 to less than 1:1, 989 (mean = 1:1,571) for adult progeny. SLE virus also was transmitted transovarially by colonized and field-collected populations of Culex pipiens (mean MIRs = 1:340 and 1:1,815 for larval and adult progeny, respectively) and by a field population of Culex quinquefasciatus (MIR = 1:500 and less than 1:246 for larval and adult progeny, respectively), but not by colonized strains of Cx. quinquefasciatus and Culex peus. SLE virus was not recovered in tests on 5,522 Cx. tarsalis and 4,798 Cx. quinquefasciatus that were collected as larvae or pupae from field sites in Southern California and reared to adults at 18 degrees C in the laboratory. Transovarial transmission of SLE virus by Aedes epactius was confirmed and extended to a closely related species, Aedes atropalpus. Efforts to demonstrate transovarial transmission of SLE virus by Aedes melanimon, Aedes sierrensis, and Aedes triseriatus were unsuccessful. Aedes dorsalis, Cx. peus, and Toxorhynchites amboinensis were equally sensitive hosts for viral isolation when inoculated with suspensions of larvae transovarially infected with SLE virus.

Aedes↗
PubMed1983

Effect of temperature of extrinsic incubation on the vector competence of Culex tarsalis for western equine encephalomyelitis virus.

Culex tarsalis was a less competent vector of western equine encephalomyelitis (WEE) virus after 2-3 weeks' extrinsic incubation at 32 degrees C than after incubation at 18 degrees or 25 degrees C. The high temperature itself was not directly detrimental to mosquito infection as all mosquitoes were initially infected, but subsequently some females were able to limit viral multiplication and/or dissemination. Elevated maintenance temperatures enhanced the expression of modulation, and elevated larval rearing temperatures selected for those females with this trait. This is the first report of an inverse relationship between temperature of extrinsic incubation within the range of 25 degrees-32 degrees C and vector competence of a mosquito for an arbovirus.

Animals↗
PubMed1983

Comparative vector competence of Culex tarsalis and Culex quinquefasciatus from the coachella, imperial, and San Joaquin Valleys of California for St. Louis encephalitis virus.

St. Louis encephalitis (SLE) virus has continued to be active in the Colorado Desert region of Southern California (Coachella and Imperial Valleys) since 1973, while it has virtually disappeared from the Sacramento and San Joaquin Valleys of Central California. Consequently, comparative vector competence studies were undertaken from 1978 to 1981 to evaluate the susceptibility of populations of Culex quinquefasciatus and Culex tarsalis from the San Joaquin and Coachella/Imperial Valleys to oral infection with representative SLE viral strains from each geographical area. Culex quinquefasciatus females from both areas were equally susceptible to infection with both viral strains by the pledget and viremic chick feeding techniques. Although susceptibility profiles were similar by both feeding techniques, infection thresholds (i.e., ID50S) obtained with Cx. quinquefasciatus females were at least 10,000-fold lower when fed on viremic chicks than on virus soaked pledgets. Culex tarslis females from the two geographical areas were equally susceptible to infection with the indigenous viral strain by feeding on pledgets, and were uniformly more susceptible than sympatric populations of Cx. quinquefasciatus. Thus, differences observed in SLE viral activity in different geographical areas of California since 1973 cannot be explained by differences in the susceptibility of Cx. quinquefasciatus or Cx. tarsalis to oral infection with SLE virus.

Animals↗
PubMed1983

Comparison of biological properties of St. Louis encephalitis and Rio bravo viruses.

St. Louis encephalitis (SLE) virus, an arbovirus, and Rio Bravo (RB) virus, a non-arthropod-borne virus, are flaviviruses which cross-react in neutralization tests. Several of their biological properties were compared. Viral growth curves revealed that greater than 99% of infectious SLE (Parton) virus remained cell-associated in Vero cells but was released slowly into the medium of infected BHK-21 cells. In contrast, RB (M-64) virus was released upon maturation into the fluids of Vero and BHK-21 cell cultures. Fortyfold more SLE virus than RB virus adsorbed to monolayer cultures of Aedes dorsalis cells. SLE but not RB virus replicated and reached high titers (10(8) pfu/ml) in Ae. dorsalis cell cultures maintained in media which were expected to enhance recovery of RB virus. Further, SLE but not RB virus replicated in cultured bat epithelial cells and primary duck embryo cells incubated at 42 degrees C. Clearly, the prototype strains of RB and SLE viruses are distinct viruses. Both the classification of RB virus in the genus flavivirus and the antigenic relationship between RB and SLE viruses require further clarification.

Aedes↗
PubMed1983

Historical perspectives on California encephalitis virus in California.

CEV is primarily associated with Ae. melanimon as its maintenance host and vector in California. A few species of lagomorphs and rodents will develop a transient viremia when infected. Infection of domestic mammals and man is frequent but rarely results in a clinical disease. Extensive field and laboratory studies lead to the conclusion that CEV probably is a mosquito virus that is partially adapted to a narrow range of vertebrate hosts but is not reliant on vertebrates for its continuous existence. JCV has many similarities to CEV in California in that it is dependent on one mosquito, Cu. inornata, as its vector and, as far as is known, the same group of mammalian species as for CEV serve as hosts for JCV.

Aedes↗
PubMed1983

Stimulatory protein kinase modulator, the cation-binding protein and megamodulin. 3. Isolation from baker's yeast.

Three peak-activity fractions of megamodulin were noted in Sephadex G-100 filtration of its crude preparation from baker's yeast (Saccharomyces cerevisiae). Megamodulin thus prepared and its Mg2+-binding complex were shown not only to augment the activity of rabbit brain megamodulin-dependent protein kinase I (M-PK1) but also to interact with arginine-rich histone.

Animals↗
PubMed1982

Transovarial and trans-stadial transmission of California encephalitis virus in Aedes dorsalis and Aedes melanimon.

California encephalitis (CE) virus was transmitted transovarially by its natural vectors, Aedes dorsalis and Aedes melanimon following infection by intrathoracic inoculation. Virus was recovered from adult Ae. melanimon reared from eggs that were stored for up to 19 months and exposed to repeated freezing and thawing. Neither time since oviposition nor storage conditions affected infection rates in surviving embryos. Survival rates were highest in eggs stored at 4 degrees C. Transovarial infection with CE virus did not affect survival of embryos, larvae or adults. However, transovarially infected larvae took longer to develop than did their uninfected siblings.

Aedes↗
PubMed1982

Stabilized infection of California encephalitis virus in Aedes dorsalis, and its implications for viral maintenance in nature.

Three populations of Aedes dorsalis were selected which transmitted California encephalitis (CE) virus vertically to over 90% of their progeny. Infected progeny in these subpopulations transmitted virus at similar rates through five generations; females from the last generation transmitted virus by bite to suckling mice. These high rates of vertical transmission appeared to be due to the development of a stabilized infection with CE virus rather than to genetic selection for a more efficient transmitter or for a mutant strain of virus. In developed nonstabilized infections and transmitted virus vertically to approximately 20% of their progeny. The existence of stabilized infections of CE virus in vector populations and its implications for the natural history of CE virus and on the Fine and LeDuc model are discussed.

Aedes↗
PubMed1982

Evaluation of the efficiency of transovarial transmission of California encephalitis viral strains in Aedes dorsalis and Aedes melanimon.

California encephalitis (CE) virus was transmitted transovarially by its natural vector, Aedes melanimon. Vertical transmission rates ranged from 13-26% in geographical populations of Ae. melanimon infected with CE virus by intrathoracic inoculation. No consistent pattern of transmission rates was detected for location or time of year mosquito collection. Vertical transmission rates ranged from 9-29% in Aedes dorsalis inoculated with CE viral strains isolated from Ae. melanimon collected in California. The month or year of viral isolation had no effect on the efficiency of vertical transmission. However, a viral strain isolated from the Owens Valley was less efficiently transmitted than strains from the Sacramento Valley, and strains from the San Joaquin Valley were intermediate in efficiency. Filial infection rates were highest in first ovarian cycle progeny and declined with increasing ovarian cycles in both Ae. dorsalis and Ae. melanimon.

Aedes↗
PubMed1982

Sensitivity to carbon dioxide in mosquitoes infected with California serogroup arboviruses.

Ten species of mosquitoes became sensitive to CO2 following intrathoracic (i.t.) inoculation of California encephalitis (CE) virus. These included field-collected Aedes melanimon, Aedes nigromaculis and Culiseta incidens and laboratory-colonized strains of Aedes dorsalis, Aedes triseriatus, Anopheles freeborni, Culex peus, Culex pipiens pipiens, Culex pipiens quinquefasciatus and Culex tarsalis. Another California serogroup virus, Jerry Slough (= Jamestown Canyon) (JS), also induced CO2 sensitivity in nearly 100% of infected female Ae. dorsalis, Ae. melanimon and Cx. tarsalis. Sensitivity to CO2 developed in Ae. dorsalis and Cx. tarsalis within 3 days after i.t. inoculation of CE virus, remained at a high level through day 10 after inoculation and decreased gradually with time until by 30 days post-inoculation nearly all mosquitoes were nonsensitive. In contrast, Ae. dorsalis infected transovarially with CE virus were not CO2 sensitive. There was homologous but no heterologous interference to the development of CO2 sensitivity when Ae. dorsalis infected transovarially with CE virus were inoculated with CE or JS viruses. Two other bunyaviruses, Main Drain and Turlock, produced CO2 sensitivity in 3-10% and 0%, respectively, of infected Ae. dorsalis, Ae. melanimon and Cx. tarsalis. Two toga-viruses, St. Louis encephalitis and western equine encephalomyelitis, did not induce CO2 sensitivity in Ae. dorsalis and Cx. tarsalis.

Aedes↗
PubMed1981

Dissemination barriers for western equine encephalomyelitis virus in Culex tarsalis infected after ingestion of low viral doses.

There are two dose-dependent barriers to the transmission of western equine encephalomyelitis virus in infected female Culex tarsalis. In the first, virus multiplies in the mesenteron, but does not invade other tissues regardless of the length of extrinsic incubation. We call this the "mesenteronal escape" barrier. In some mosquitoes virus escapes from the infected mesenteron but a second barrier prevents infection of the salivary glands and perhaps neural tissues. We designate this the "salivary gland infection" barrier. The effectiveness of the second barrier decreases with time but still is evident after 21 days of extrinsic incubation. The distribution of virus in the tissues of nontransmitting females with either of these barriers is described.

Animals↗
PubMed1981

Permeability of the midgut basal lamina in the mosquito, Culex tarsalis Coquillett (Insecta, Diptera).

The permeability of the basal lamina of the midgut of the mosquito, Culex tarsalis, was determined for engorged and unfed mosquito midguts both pre- and postfixed. A range of materials, with diameters from less than 2nm (lanthanum) through 90 nm, (polystyrene spheres), was examined. The permeability of the basal lamina was constant under all experimental conditions; 5--8 nm particles (colloidal thorium) were the largest to consistently permeate. The discussion is centered on the question of how a virus particle, often 10 times the diameter of the established permeability limits of the basal lamina, can traverse this structure. Possible explanations are: 1. The basal lamina is a dynamic, plastic structure that easily distorts under physical and/or biochemical stresses, 2. The virion may possess enzymatic activity that locally alters the structure of the basal lamina, or 3. The extracellular surfaces of the midgut epithelium or the basal lamina itself may possess enzymatic properties that alter the size or possibly the structure of the virion as it passes through.

Animals↗