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Biomedical subjects

R L Ward

Publications and source records attributed to R L Ward.

At least 145 records · Page 8Linked to original sources
PubMed1985

Development of methods to measure virus inactivation in fresh waters.

This study concerns the identification and correction of deficiencies in methods used to measure inactivation rates of enteric viruses seeded into environmental waters. It was found that viable microorganisms in an environmental water sample increased greatly after addition of small amounts of nutrients normally present in the unpurified seed virus preparation. This burst of microbial growth was not observed after seeding the water with purified virus. The use of radioactively labeled poliovirus revealed that high percentages of virus particles, sometimes greater than 99%, were lost through adherence to containers, especially in less turbid waters. This effect was partially overcome by the use of polypropylene containers and by the absence of movement during incubation. Adherence to containers clearly demonstrated the need for labeled viruses to monitor losses in this type of study. Loss of viral infectivity in samples found to occur during freezing was avoided by addition of broth. Finally, microbial contamination of the cell cultures during infectivity assays was overcome by the use of gentamicin and increased concentrations of penicillin, streptomycin, and amphotericin B.

Fresh Water↗
PubMed1984

Betaxolol and acetazolamide. Combined ocular hypotensive effect.

To determine the combined ocular hypotensive effect of topical betaxolol hydrochloride and oral acetazolamide, we conducted a three-week clinical trial of the concurrent administration of the two drugs. One drop of betaxolol hydrochloride 0.5% every 12 hours effected a mean reduction in outflow pressure from baseline of 27.3%. When given topically to both eyes of a patient pretreated with oral acetazolamide (500 mg every 12 hours), betaxolol caused an additional mean outflow pressure decrease of 17.6%. Acetazolamide, 500 mg orally every 12 hours, produced a mean outflow pressure reduction from baseline of 42.5%. When added to the therapy regimen of a patient already receiving topical betaxolol, oral acetazolamide caused an additional mean outflow pressure decrease of 35.1%. Our study supports the clinical usefulness of concurrent administration of betaxolol and acetazolamide to lower intraocular pressure.

Acetazolamide↗
PubMed1984

Effects of topical betaxolol, timolol, and placebo on pulmonary function in asthmatic bronchitis.

To evaluate the effects of two beta-adrenergic blocking agents on cardiopulmonary function, we investigated two topical ophthalmologic preparations, betaxolol 1% and timolol 0.5%, in nine patients (eight men and one woman, ranging in age from 25 to 69 years) with reactive airway disease. The randomized, double-masked, crossover study used placebo eyedrops as the control, and each drug was tested on separate days. Spirometric measurements, respiratory rate, pulse rate, and blood pressure were observed at frequent intervals for four hours after the test solutions were instilled. At the end of the test, an inhaled beta-adrenergic stimulant (isoproterenol) was administered, and the measurements were repeated. Timolol produced a significant decrease in airflow, measured by forced expiratory volume in one second (FEV1) and the ratio of FEV1 to vital capacity at each observation time beyond 15 minutes. Betaxolol and placebo eyedrops produced no significant change from control values. These results suggested that timolol can adversely affect patients with reactive airway disease. Betaxolol eyedrops, conversely, caused no decrease in airflow in the same patients with proven airway disease.

Administration, Topical↗
PubMed1984

Studies of echovirus-12 in volunteers: determination of minimal infectious dose and the effect of previous infection on infectious dose.

A two-part study of echovirus-12 was done in volunteers. In the first part the human infectious dose of the virus was determined in 149 healthy adults with undetectable serum antibody, each of whom drank 0-330,000 plaque-forming units (pfu) of virus in 100 ml of nonchlorinated water. Infection was defined as fecal shedding of virus or significant (fourfold or greater) increases in serum antibody titer. The HID50 (i.e., the dose required for infection of 50% of the volunteers) was 919 pfu. Through statistical analysis of the data by probit transformation, a 1% human-infectious dose of 17 pfu was predicted. These results were used in the second portion of the study to determine the effect of previous infection on the infectious dose. Previously infected volunteers (those with neutralizing serum antibody) were given a dose of echovirus-12 (1,500 pfu) that had been found to infect 60% of persons with undetectable serum antibody. The presence of serum antibody caused no significant change in the percentage of volunteers infected by this dose. Furthermore, the concentration of serum antibody did not affect the rate of infection or the duration of viral shedding. These results indicate that previous infection with echovirus-12 does not provide lasting protection against reinfection.

Adolescent↗
PubMed1984

Enteric virus and indicator bacteria levels in a water treatment system modified to reduce trihalomethane production.

A drinking-water treatment plant with high concentrations of trihalomethanes in its finished water and large numbers of viruses in its source water was located. This plant was used to study the effect of an alteration in the point of chlorination from the first to last step of water treatment on the biological and chemical qualities of its finished water. This alteration caused some reduction in trihalomethane production, but trihalomethane concentrations still exceeded the prescribed limit of 100 micrograms/liter. No viruses or bacterial indicators were ever isolated from the finished water of the modified plant. Total virus removal by the treatment steps before chlorination (coagulation, sedimentation, and sand filtration) averaged ca. 90%, whereas removal of bacterial indicators by these processes averaged between 88 and 98%. Recoveries of viruses and bacterial indicators in the source water were generally negatively correlated.

Chlorine↗
PubMed1984

Efficiency of human rotavirus propagation in cell culture.

This study was designed to find methods to reproducibly propagate human rotaviruses from fecal specimens and to determine the relationship between particle numbers and infectivity. Growth of virus was initially compared in primary and continuous lines of monkey kidney cells. Primary cells (African green and cynomolgus monkey kidney) supported virus growth directly from fecal specimens much more efficiently than did continuous lines of African green (CV-1) or rhesus (MA104) monkey kidney cells. Rotaviruses were grown in primary cells from 14 of 14 fecal specimens of different individuals collected over a 3-year period. Although rotaviruses in fecal samples could not always be grown in the continuous cell lines, two passages in primary cells appeared to fully adapt the viruses for propagation in the continuous cell line tested (MA104). The efficiency of rotavirus growth was quantified with five of the fecal isolates. It was calculated that, on the average, 1 out of every 46,000 particles in fecal specimens infected monkey kidney cells. After three passages in primary cells, an average of 1 out of every 6,600 progeny virus particles appeared to be infectious. Thus, rotaviruses in fecal specimens were consistently grown in primary cells, and passage in these cells both increased virus infectivity and adapted the viruses for growth in continuous cell lines.

Animals↗
PubMed1982

Induction of cytopathogenicity in mammalian cell lines challenged with culturable enteric viruses and its enhancement by 5-iododeoxyuridine.

Cultures of 17 established cell lines were tested against 105 enteric virus types for capacity to support viral replication as indicated by cytopathogenic effect production. Enhancement of susceptibility by treatment of the cells with 5-iododeoxyuridine was evaluated in parallel with untreated cells. Cytopathogenic effect was produced in two or more cell lines by every virus tested except six strains of group A coxsackie virus. No cell line was found to be susceptible to these six virus types. In general, treatment with 5-iododeoxyuridine provided a more rapid onset of cytopathogenic effect in susceptible cells and in some instances resulted in refractory cells becoming permissive to viral replication. The use of 5-iododeoxyuridine allowed two human embryonic lines (HEL-299 and L-132), in combination, to be susceptible to all but the six group A coxsackie virus strains.

Adenoviruses, Human↗
PubMed1982

Uptake of bacteriophage f2 through plant roots.

A model system was designed to measure viral uptake through the roots of plants and translocation to distal plant parts. For this study, uptake of bacteriophage f2 was measured in corn and bean plants growing in hydroponic solutions. Few phage were detected in plants with uncut roots. However, when roots of both plant types were cut just before exposure to very high concentrations of phage, the amount of phage uptake was several orders of magnitude greater than with uncut roots, but still was considerably less than that which was theoretically possible. Furthermore, cut roots were rapidly repaired, thus inhibiting uptake, and the amount of uptake in plants with cut roots was proportional to phage exposure levels. Finally, phage were transported to all plant parts examined, but their survival times within each portion of the plants appeared to be of limited duration. All of these factors tend to minimize the possible public health significance associated with viral uptake through the root systems of plants.

Coliphages↗
PubMed1982

Evidence that microorganisms cause inactivation of viruses in activated sludge.

Virus loss in activated sludge appeared to be caused by microorganisms. This conclusion is supported by the finding that poliovirus infectivity decreased during incubation in mixed-liquor suspended solids, primarily because of a sedimentable, heat-sensitive component. Furthermore, broth spiked with mixed-liquor suspended solids acquired antiviral activity during incubation.

Bacterial Physiological Phenomena↗
PubMed1982

Comparison of methods for recovering indigenous viruses from raw wastewater sludge.

Five general methods for recovering indigenous viruses from raw wastewater sludge were compared. Each method included elution, concentration, and disinfection steps. The elution method, found to consistently yield the greatest viral recovery, was a two-phase technique that involved blending sludge with Freon. Other methods, including two being tested as American Society for Testing Materials tentative standard methods, were less effective. Viral recoveries were generally greater (sometimes much greater) if samples were concentrated by high-speed centrifugation rather than by organic flocculation with 3% beef extract. Three cell lines were used to measure viral recoveries by the plaque assay. The efficiency of recovery was greatest on BGM cells, followed by RD and MA-104 cells.

Cell Line↗
PubMed1981

Effects of moisture content on long-term survival and regrowth of bacteria in wastewater sludge.

The effects of moisture content on the survival and regrowth of seeded and indigenous enteric bacteria in raw sludge were determined. Cultures of six strains of fecally associated bacteria grown in sterilized, liquid sludge (5% solids) were all quite stable at this moisture level for over 90 days at 21 degrees C. When the moisture content of the sludge containing these organisms was reduced by evaporation and the samples were stored at 21 degrees C for extended periods, bacterial inactivation rates were generally proportional to the moisture losses of the samples. A dramatic reversal in this effect was observed in samples containing more than 90% solids. In this dried sludge, every bacterial species studied except Proteus mirabilis was found to be extremely stable. Bacteria indigenous to sludge were also found to survive for long periods in dried sludge. Regrowth of bacterial isolates in sterilized raw sludge was found to occur readily at 37 degrees C in samples containing less than or equal to 75% solids, but no growth was observed in samples with greater than or equal to 85% solids. Some growth, but to less than saturation densities, occurred with 80% solids. Growth of seeded Salmonella typhimurium was also found to occur in the presence of indigenous organisms in both liquid and dewatered raw sludges. However, the population density attained was well below that found in sterilized samples of the same sludges. In addition, the number of salmonellae dropped below detectable limits within a few days in sludges containing viable indigenous organisms, whereas little decrease occurred during this time with salmonellae grown in previously sterilized sludges.

Enterococcus faecalis↗
PubMed1981

Response of bacteria in wastewater sludge to moisture loss by evaporation and effect of moisture content on bacterial inactivation by ionizing radiation.

Two studies were carried out to determine the influence of moisture content of the survival of bacteria in raw wastewater sludge. The first study involved the effect of water loss by evaporation on the bacterial population. The second used these dewatered samples to measure the effects of moisture content on the inactivation of bacteria sludge by ionizing radiation. Both studies involved survival measurements of six representative fecally associated bacteria grown separately in sterilized sludge as well as survival data on bacteria indigenous to sludge. Growth of bacteria was stimulated in sludge during the initial phase of moisture removal by evaporation, but the reduction of moisture content below about 50% by weight caused a proportional decrease in bacterial numbers. In comparison with the original sludge, this decrease reached about one-half to one order of magnitude in all dried samples except those containing Proteus mirabilis, which decreased about four orders of magnitude. The rates of inactivation of bacteria by ionizing radiation in sludge were usually modified to some degrees by variations in moisture content. Most bacteria were found to be somewhat protected from ionizing radiation at reduced moisture levels. The largest effect was found with Salmonella typhimurium, whose radiation resistance approximately doubled in dried sludge. However, no excessively large D10 values were found for any bacterial species tested.

Desiccation↗
PubMed1981

Norepinephrine dipivalylate dose-response in ocular hypertensive subjects.

Norepinephrine dipivalylate, a prodrug analog of the catecholamine mediator norepinephrine, was given to 12 ocular hypertensive patients. Single instillations of four concentrations, 0.05%, 0.1%, 0.25%, and 0.5%, were administered weekly to one eye only with the fellow eye receiving a placebo. Intraocular pressure, pupil size, ocular signs, subjective symptoms, heart rate, and blood pressure were monitored at 2, 4, 6, 8, and 12 hours following instillation. An intraocular pressure reduction dose response was seen. After a slow (four-hour) onset of activity, the 0.5% concentration produced clinically acceptable (less than 22 mm Hg) tensions at the 6-, 8-, and 12-hour observations which were significantly (p less than 0.05, paired t test) lower than placebo-control eyes. No clinically important side effects were seen.

Clinical Trials as Topic↗
PubMed1980

Comparative study on the mechanisms of rotavirus inactivation by sodium dodecyl sulfate and ethylenediaminetetraacetate.

This report describes a comparative study on the effects of the anionic detergent sodium dodecyl sulfate and the chelating agent ethylenediaminetetraacetate on purified rotavirus SA-11 particles. Both chemicals readily inactivated rotavirus at quite low concentrations and under very mild conditions. In addition, both agents modified the viral capsid and prevented the adsorption of inactivated virions to cells. Capsid damage by ethylenediaminetetraacetate caused a shift in the densities of rotavirions from about 1.35 to about 1.37 g/ml and a reduction in their sedimentation coefficients. Sodium dodecyl sulfate, on the other hand, did not detectably alter either of these physical properties of rotavirions. Both agents caused some alteration of the isoelectric points of the virions. Finally, analysis of rotavirus proteins showed that ethylenediaminetetraacetate caused the loss of two protein peaks from the electrophoretic pattern of virions but sodium dodecyl sulfate caused the loss of only one of these same protein peaks.

Adsorption↗
PubMed1980

Effects of wastewater sludge and its detergents on the stability of rotavirus.

Wastewater sludge reduced the heat required to inactivate rotavirus SA-11, and ionic detergents were identified as the sludge components responsible for this effect. A similar result was found previously with reovirus (R. L. Ward and C. S. Ashley, Appl. Environ. Microbiol 36:889-897, 1978). The quantitative effects of individual ionic detergents on rotavirus and reovirus were very different, and rotavirus was found to be extremely sensitive to several of these detergents. However, neither virus was destabilized by nonionic detergents. On the contrary, rotavirus was stabilized by a nonionic detergent against the potent destabilizing effects of the ionic detergent sodium dodecyl sulfate. The destabilizing effects of both cationic and anionic detergents on rotavirus were greatly altered by changes in the pH of the medium.

Animals↗