Inactivation of Encephalomyocarditis Virus in Aerosols: Fate of Virus Protein and Ribonucleic Acid

After aerosolization at relative humidities of 50% or lower, encephalomyocarditis virus is rapidly inactivated. In this process the protein coat of the virion is damaged. This appears as a loss of hemagglutination activity and loss of affinity for hemagglutination inhibiting antibodies. The ribonucleic acid of the virus retains its infectivity but it becomes susceptible to ribonuclease. It sediments in sucrose gradients when centrifuged at high speed with the same velocity as free infectious ribonucleic acid extracted with phenol from intact encephalomyocarditis virus.     

Virus survival as a seasonal factor in influenza and poliomyelitis

Summary The influence of temperature and humidity on the survival of airborne viruses was studied in a static system. Preliminary experiments with a bacteriophage showed that relative humidity was more important than temperature and absolute humidity. The effect of relative humidity was not dependent on the composition of the medium surrounding the virus particles. The survival of influenza and poliomyelitis virus are sharply influenced by relative humidity but in an opposite way. Influenza virus survives much better at lower humidities, poliomyelitis virus at higher humidities. In countries with moderate climates the period of increasing morbility for influenza, in winter, coincides with indoor conditions of relative humidity which are optimal to virus survival. For poliomyelitis the same is true during summer (Fig. 7). Indoor relative humidity is considered an important “seasonal factor” in the epidemiology of poliomyelitis and influenza and probably of other diseases.     

Effect of relative humidity of hot air on the heat resistance of Bacillus cereus spores

The heat resistance to hot air of spores of Bacillus cereus (ATCC 14579) attached to carriers of stainless steel or silicone rubber was investigated in a range from 1% to 100% relative humidity (RH). Apart from an initial stage, linear survivor curves were obtained for all relative humidities. Neither the attachment itself nor the material of the carrier had an influence on the resistance. A distinct maximum of heat resistance was found at 40% RH. At 122°C the rate constants at 40% RH were five orders of magnitude smaller than at 100% RH and two orders of magnitude smaller than at 1% RH. At relative humidities of more than 40% the rate constants were strongly temperature dependent, whereas at lower relative humidities they were less temperature dependent. No significant influence of the relative humidity on the Arrhenius activation energy was found within each humidity range. The mean values were 295 kJ mol^-1 for relative humidities of 60% to 100% RH and 165 kJ mol^-1 for 1% to 20% RH. The occurrence of a maximum is ascribed to the existence of two inactivation mechanisms, the first is retarded and the second is accelerated by a reduction of relative humidity. It is assumed that the first mechanism is a protein denaturation. The second mechanism may be an oxidative process.     

Quantitative Studies on Fabrics as Disseminators of Viruses: II. Persistence of Poliomyelitis Virus on Cotton and Wool Fabrics

The length of time that poliovirus could be recovered from wool gabardine and blanket, and from cotton sheeting, terry cloth, and knit jersey fabrics was determined under conditions of controlled temperature and humidity (25 C in 35 and 78% relative humidities). Three types of exposure of the fabrics to viruses were used: direct contact, aerosol, and virus-containing household dust having a high content of textile fibers. When held in 35% relative humidity, virus persisted for 20 weeks on wool fabrics, but only 1 to 4 weeks on cotton fabrics. At this relative humidity, virus titers on wool fabrics decreased rapidly to low but detectable levels which persisted for long periods of time, whereas in 78% relative humidity the decrease in virus titer was less rapid, but the period of viral persistence was shorter. Generally, virus titers on cotton fabrics held in both relative humidities decreased exponentially to an undetectable level. The method of exposure to virus had a definite effect on the duration of viral persistence on a given fabric. Virus contained in household dust was least stable.     

Effects of moisture on the toxicity of inorganic and organic insecticidal dust formulations to German cockroaches (Blattodea: Blattellidae)

Toxicity of boric acid (40-99% [AI]), silica gel, eugenol, and deltamethrin dust formulations to adult male German cockroaches, Blattella germanica (L.), was evaluated at five different relative humidities ranging from 0 to 100% and in the presence of 0 to 1 ml of water. Victor boric acid dust was generally the most toxic boric acid formulation at all relative humidities, despite having the lowest percentage (40%) of boric acid; however, this was the only formulation to have sucrose and other edible ingredients. There was no consistent effect of relative humidity on dust toxicity; LT50 values of Roach Prufe (98% boric acid), Victor, and Drione (silica gel and synergized pyrethrins) increased significantly linearly with relative humidity, whereas other formulations were unaffected. The LT50 values of all boric acid-based dust formulations declined exponentially when wetted with increasing volumes of water. Water did not affect the toxicity of deltamethrin and eugenol dusts, but it caused a linear decline in toxicity of silica gel (Dri-Die). The toxicity of a formulation containing silica gel and synergized pyrethrins (Drione) increased exponentially with increasing amounts of water. Moisture in the form of relative humidity does not strongly affect the toxicity of most insecticidal dust formulations. Presence of water, however, increases the toxicity of boric acid dusts and Drione. Toxicity of the hydrophobic deltamethrin (DeltaDust) and eugenol (EcoPCO D) dusts were unaffected by water.     

Effects of Environmental Factors on the Survival of Airborne T-3 Coliphage

Experiments were conducted to determine the effects of storage temperatures, relative humidity, and additives on the survival of aerosolized Escherichia coli phage T-3. The aerosol stability of the coliphage, calculated as per cent recovery, was not affected by storage at 10 or -70 C for up to 4 months. However, an increase in aerosol decay rate of coliphage stored at 10 C was observed. The effect of humidities ranging from 20 to 90% relative humidity was studied, and it was observed that humidities lower than 70% relative humidity significantly reduce the survival of airborne coliphage. The effect of various compounds on the aerosol decay rate of T-3 coliphage was studied at 50 and 85% relative humidity. Addition of dextrose in 0.1 M concentrations to the disseminating fluid significantly reduced aerosol decay rate at 50% relative humidity without affecting the decay at 85%. Addition of spermine, spermidine-phosphate, thiourea, galacturonic acid, and glucosaminic acid, individually or in combination, had no effect on aerosol decay rates. The use of deuterium oxide as the suspending fluid for dissemination had no effect on aerosol stability of the coliphage.     

Infectivity-destroying Effect of Humidity for Dried Coliphage T1

Infectivity of dried coliphage T1 has been measured as a function of humidity, temperature, and atmospheric pressure. Loss of infectivity by a factor of 10(4) was caused by water vapor of approximately 40 to 85% saturation when the microorganisms were kept for 3 days at 34 C in evacuated containers. At humidities below 40% and above 90% saturation, no loss of infectivity occurred. At a temperature of 24 C, the infectivity loss was 20-fold. When the virus preparation was kept at 34 C and atmospheric pressure, some loss of infectivity was also found at humidities below 40% and above 90% saturation. Damage to tail proteins or to the phage chromosome is considered as a possible explanation for the inactivation.     

Ultrastructural Effects of Water Stress on Chloroplast Development in Jack Bean (Canavalia ensiformis [L.] DC)

An ultrastructural study has been made to determine to what degree chloroplast differentiation is retarded in leaves of young jack bean (Canavalia ensiformis [L.] DC.) seedlings when they are subjected to mild water stress. Rapid chloroplast differentiation occurred when etiolated seedlings were allowed to green at relative humidities above 85% but not at a relative humidity of 25%. Response to a drop in humidity was rapid. Germination and early development in the dark occurred at 100% relative humidity. At the time of exposure to light, the etioplasts contained well formed prolamellar bodies. Under high relative humidity conditions, transformation of the prolamellar body was well advanced within 2 hours. Under low relative humidity conditions, however, prolamellar body differentiation was extremely retarded for more than 24 hours following the beginning of illumination.     

Comparison of the behavioural and physiological responses to humidity of five species of dry-wood termites, Cryptotermes species

ABSTRACT. A circular humidity gradient apparatus with a porous cellulose substrate was used to compare the humidity responses of pseudoworkers (immature wood-feeding forms) of five species of dry-wood termites. Four of these species are widely distributed pests of buildings: Cryptotermes brevis (Walker), C. cynocephalus Light, C. dudleyi Banks and C. havilandi (Sjöstedt). The fifth species, C. naudei Coaton, has not been recorded from buildings. C. havilandi, C. cynocephalus and C. naudei were found to tend to group and feed at humidites above 90% r.h., while C. dudleyi pseudoworkers avoided humidities above 90% r.h. and below 70% r.h. These results accord with the results of studies on the effects of relative humidity on feeding and reproduction of these species. The behaviour of the most widespread species, C. brevis , seems to be closely associated with its ability to undergo acclimatization and to feed efficiently at either medium ( c. 60%) or high ( c. 90%) relative humidity. C. brevis kept at 89% r.h. showed an increased tendency to group at humidities above 90%, with a lower temperature preference, changes in faecal pellet formation and, for one population at least, an increased tolerance of exposure to saturated air. The humidity preferences at constant temperature were compared with the temperature preferences of the same individuals examined in uniform humidity. The value of behavioural responses as indicators of physiological differences between species and populations is considered.     

Effects of hydration in the oxygenation and autoxidation of carbonmonoxyhemoglobin powder

The oxygenation and autoxidation of lyophilized human carbonmonoxyhemoglobin (Hb-CO) kept in environments with different relative humidities were followed with time using visible absorption spectroscopy. The sample kept at 68% relative humidity was the one with the greatest formation of methemoglobin (Met-Hb), while for increasing or decreasing hydrations the Met-Hb content decreased gradually. Besides the presence of Met-Hb, it was observed that the samples kept above about 68% relative humidity were converted to oxyhemoglobin (Hb-O2), the samples kept in the range 45-68% relative humidity were a mixture of Hb-CO and Hb-O2, while the samples kept below about 45% relative humidity and the solution sample continued as Hb-CO. Hemoglobin has, therefore, two critical hydration values, 45% and 68% relative humidity, which correspond to about 0.12 and 0.18 g H2O/g protein, respectively.     

Flowering and Growth Response of Peanut Plants (Arachis hypogaea L. var. Starr) at Two Levels of Relative Humidity

Peanut plants (Arachis hypogaea L. var. Starr) grown under two different relative humidities were used in all experiments. All plants were germinated and grown to flowering in the greenhouse. At this time, one group was moved to a growth room under 95% relative humidity. After 50 days the humidity of the growth room was lowered to 50%. The second group was moved into a growth room at 50% relative humidity and after 50 days the humidity was raised to 95%.     

Quantitative Studies on Fabrics as Disseminators of Viruses: I. Persistence of Vaccinia Virus on Cotton and Wool Fabrics

The persistence of vaccinia virus on wool (blanket and gabardine) and cotton (sheeting, terry cloth, and knit jersey) fabrics was studied. The fabrics were exposed to the virus by three methods: direct contact, aerosol, and virus-containing dust having a high content of textile fibers. Fabrics exposed to virus by each method were held in 35 and 78% relative humidities at 25 C. Virus was recovered for up to 14 weeks from wool fabrics exposed to virus and held in the low humidity. In contrast, virus persisted for shorter periods of time on the cotton fabrics. No virus was detected on terry cloth as early as 3 days after exposure to virus. The virus appeared to be less stable in the high humidity, and the method of exposure of the fabrics to virus apparently had an effect upon the persistence of the agent. On all fabrics, viral persistence was of sufficient duration to be of epidemiological significance.     

Abiotic mortality factors of the coffee berry borer (Hypothenemus hampei)

Mortality of the coffee berry borer was studied under controlled laboratory conditions in Tapachula, Mexico. For adult female borers subjected to a range of relative humidities (RH) without food at 25°C, the longest mean survival time (20 days) was obtained at 93.5% RH. Adult borer survival was also studied at a range of temperatures for a fixed relative humidity (93.5% RH); at 20°C mean survival time was 28 days. Fecundity and mortality of borer stages in berries was studied for a range of humidities at 25°C. Maximum fecundity was obtained at 90 and 93.5% RH. Immature stages were ejected from the berry at 84% RH and above, which is interpreted as a form of brood hygiene.     

Assessment of Aerosol Mixtures of Different Viruses

Aerosol mixtures of the psittacosis agent, yellow fever virus, and variola virus were assayed by selective immunofluorescence in conjunction with fluorescent cell counting. The aerosol behavior of each agent could be readily delineated at test conditions of 80 F (26.67 C) and three relative humidities (30, 50, or 80%). Of the three agents, variola virus exhibited the lowest biological decay. The biological decay rates of the airborne agents were not significantly affected by humidity changes.     

Humidity-invoked upwind orientation of shore insects (Bambidion obtusidens, coleoptera: Carabidae)

Because insects cannot rely solely on kinetic responses to locate upwind humidity resources, an alternative mechanism involving the perception of windborne humidity fluctuations was investigated. In a wind tunnel, upwind responses of adult shore insects (Bembidion obtusidens Fall, Carabidae, Coleoptera) were invoked by pulsed (1.25-Hz) increases (1.7%) of relative humidity at ambient relative humidities of 32, 42, 52, and 62% but not at 72 and 86%. Conversely, upwind responses to pulsed decreases (1.8%) occurred at 65, 72, and 86% but not at 32, 42, and 52% ambient relative humidities. These results suggest that perception by moist-air and dry-air hygroreceptors of turbulence-induced pulses of moist air or of dry air in their habitat trigger positive anemotactic orientation of these insects to upwind humidity resources.     

Destruction of L Cells by Mengo Virus: Use of Interferon to Study the Mechanism

Interferon, when added to L cells, inhibited the synthesis of infectious Mengo viral ribonucleic acid, hemagglutinins, and infectious virus by 85 to 95%. Serum-blocking antigens were also reduced by the action of interferon, but threefold excess amounts of these antigens accumulated in interferon-treated cultures above the amounts expected for the quantity of infectious virus that was produced in these cultures. Radioautographic analysis showed that 28 to 36% of the cells of an interferon-treated population synthesized viral ribonucleic acid and 36 to 47% produced viral antigens as determined by an immunofluorescence technique. Despite the reductions in synthesis of viral components, all cells in an interferon-treated culture underwent cytopathic effects at the same time as cells in infected cultures which had not been treated with interferon. The results are compatible with the hypothesis that the cell destruction which results from the infection of L cells with Mengo virus is due to a protein which is coded for by the virus but is not a component of the mature virion.     

Pinus Halepensis and Quercus Ilex Terpene Emission as Affected by Temperature and Humidity

The short-term relationships of monoterpene emission with temperature and relative humidity were studied in Pinus halepensis L. and Quercus ilex L. seedlings grown in air-conditioned chamber. In P. halepensis terpene emission rate increased with temperature (from 15 to 35 °C) and relative humidity (from 40 - 60 to 65 - 95 %). In Q. ilex, a terpene non-storing species, it increased with temperature only at high relative humidities but not at relative humidities lower than 60 %. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of Temperature on Survival of Airborne Mycoplasma pneumoniae

Aerosols of Mycoplasma pneumoniae were prepared at each of eight relative humidities between 0 and 85% and at five separate temperatures between 10 and 43 C. Survival of these organisms was found to be a function of both relative humidity and temperature. However, the temperature response was mediated by humidity in that the effects of temperature could be observed only if some water vapor was present. At all temperatures, survival of M. pneumoniae in aerosols was found to be best at the extremes of relative humidity. The effects of temperature were such that irrespective of relative humidity an increase in temperature resulted in a decreased airborne survival time.     

Effect of Relative Humidity on Dynamic Aerosols of Adenovirus 12

Dynamic aerosols of adenovirus 12 were generated in the same Henderson apparatus under conditions of high, medium, and low relative humidity. High relative humidities resulted in more recovery of adenovirus 12 from aerosols and lungs of newborn Syrian hamsters. At 89, 51, and 32% relative humidity, the total infectious virus recovered from a 20-min aerosol was 10(6.7), 10(6.0), and 10(4.3) TCD(50), respectively. Hamsters exposed to these 20-min aerosols retained measured lung doses of 10(3.0), 10(2.4), and 10(1.0) TCD(50), respectively. The measured retained lung doses were compared to calculated inhaled lung doses based on both total virus aerosolized and total virus recovery from the aerosols.     

The effects of temperature and humidity on the nocturnal activity of different shell colour morphs of the land snail Arianta arbustorum

The noctural activities of the phenotypic shell colour morphy and age classes (adults and juveniles) of Arianta arbustorum were recorded 1 day week^-1 for 4 weeks in several laboratory microclimatic conditions. Six constant temperatures between 3 and 18C and four levels of relative humidities between 34 and 98% were maintained. A light regime of 16 h light: 8 h dark was used. There are highly significant differences in activity at different levels of adaptation temperature and relative humidity. The interaction between these factors is significant. There are no significant differences in nocturnal activity between the two phenotypic shell colours nor between the two age classes, but the interaction between morph and relative humidity is significant. The interaction between age classes and relative humidity is also significant. Yellows are more active than browns at high humidities, but less active at low. They are therefore likely to be behaviourally more responsive than browns in an environment of fluctuating humidities. This result is discussed in relation to the maintenance of the polymorphism.