Adsorption of Formaldehyde by Various Surfaces During Gaseous Decontamination

Study of the effect of atmospheric relative humity (RH) on the adsorption of paraformaldehyde-generated formaldehyde gas on various surfaces and the effect of the adsorbed formaldehyde on the death rate of bacterial spores showed that increasing the RH caused a corresponding increase of formaldehyde levels on all surfaces. The amount peaked at 83% RH. The levels obtained at 100% RH were slightly below those at 83% RH. Cotton cloth had a much greater affinity for the gas at all RH than either glass or stainless steel. The death rate of bacterial spores on surfaces containing adsorbed formaldehyde was high for the first hour after removal from the formaldehyde atmosphere but decreased rapidly thereafter. This held true for both cotton and glass surfaces. Also, formaldehyde levels of 15 to 27 mug/ml of nutrient broth caused inhibition of bacterial growth, but levels above 27 mug/ml rendered broth sterile.     

Effect of Relative Humidity on Formaldehyde Decontamination

Death rate studies were conducted to determine the effect of varying the concentration, humidity, and type of surface on the sporicidal activity of formaldehyde gas. Washed and unwashed spores were similarly exposed to detect the influence of residual nutrient growth medium upon the rate of kill. The results indicated that the sporicidal activity of formaldehyde gas varies directly with its concentration. Relative humidities (RH) over 50% proved essential for sterility. Spores on a porous surface (cotton cloth) were more readily killed at lower RH than those on a nonporous surface (glass). The reverse occurred at very high RH. At 75% RH, the unwashed spores on glass were killed faster than the washed spores.     

The effects of mercaptoethanol-formaldehyde on tissue fixation and protein retention

Summary The study compared the effects of mercaptoethanol-formaldehyde and formaldehyde alone, on tissue fixation and protein retention in human and mouse tissues. Shrinkage of tissues and the penetration rate of the fixatives were assessed. The cross-linking ability of the fixatives was determined by viscometry, sodium dodecyl sulphate-polyacrylamide gel electrophoresis, and spectrophotometry, using bovine serum albumin and human haemoglobin. Tissues fixed in buffered 0.0025% mercaptoethanol-4% formaldehyde showed good nuclear and cytoplasmic detail, better than those fixed in buffered 4% formaldehyde. There was no significant difference in shrinkage. A mixture of 0.0025% mercaptoethanol-4% formaldehyde penetrated faster into adult liver than 4% formaldehyde. The mean penetration rate (±SE) or coefficient of diffusibility of 0.0025% mercaptoethanol-4% formaldehyde into adult liver was 1.32±0.01 and that of 4% formaldehyde was 1.12±0.06 (p<0.04). Both fixatives diffused more rapidly into mouse liver than into human liver. The cross-linking ability of mercaptoethanol-formaldehyde depends on the concentration of the fixative and the time of fixation. Bovine serum albumin (15%) and 0.1% mercaptoethanol alone formed a gel, whilst electrophoresis showed monomers in the supernatant. Mercaptoethanol (0.1%) also rapidly decreased the absorption at 420 nm, suggesting denaturation. It seems that mercaptoethanol increases the number of thiol groups available to form cross-links with formaldehyde. This study demonstrated that mercaptoethanol-formaldehyde fixed and cross-linked tissues better than formaldehyde at 3 h and 4 h, but not at 1 h and 2 h. The most effective concentration of mercaptoethanol for tissue fixation in 4% formaldehyde is 0.0025%.     

Reaction of Airborne Rhizobium meliloti to Some Environmental Factors

Survival of Rhizobium meliloti 102F5 in aerosols at 20 C was maximal at high relative humidity (RH) and minimal at low RH. Relatively high concentrations of NO(2), SO(2), or formaldehyde were needed to significantly reduce viability of R. meliloti in aerosols at 50% RH. Except for the reduction in activity of formaldehyde by SO(2), there was no additive or antagonistic effect of mixing pollutants. High environmental RH enhanced bactericidal activity of NO(2) and SO(2). High RH minimized and low RH accentuated the biological effect of ultraviolet light of 300 to 400 nm wavelength.     

Penetration of mouse eggs at various intervals after insemination as influenced by concentration of sperm and strain of male

This study was conducted to determine the extent to which the percentage of mouse eggs that were penetrated by sperm at the end of the period of sperm penetration was due to the proportion of eggs penetrated per unit of time and to the span of time of sperm penetration. Female mice of ICR strain were inseminated 1.5 hr after ovulation with 5 X 10(6) sperm/50 microliter from males of DBA/2N, CF1 or C57BL/6N strains to determine the effect of the male. To determine the effect of concentration of sperm ICR females were inseminated with 2, 4, 6, or 8 X 10(6) sperm/50 microliter from CF1 males. Females were killed at various intervals after insemination and the eggs were recovered and examined for evidence of penetration by a sperm. The time intervals from both insemination to the onset of egg penetration and from insemination to cessation of penetration were similar for the three strains of males. Throughout the period of penetration of eggs a constant percentage of eggs was penetrated per hour for a particular strain of male. The relative percentage penetrated per hour very closely approximated the relative percentage of eggs finally penetrated for each strain of male. The percentage of eggs penetrated per hour was linearly positively related to the concentration of sperm inseminated. The final percentage of eggs penetrated depended primarily on the rate at which the eggs were penetrated during the period of sperm penetration and not on the length of the period of egg penetration which was constant.     

REVERSIBLE INHIBITION OF SPERM-EGG FUSION IN THE HAMSTER BY LOW PH*

To study the effect of pH on sperm-egg fusion, hamster eggs were freed from egg investments (cumulus oophorus and zonal pellucida) and inseminated with acrosome-reacted spermatozoa in media with various pH values. One hundred percent of the eggs were penetrated by spermatozoa in phosphate buffered media with pH value higher than 7.1. The rate of penetration declined sharply below pH 7.0 and was 0 at pH 6.1. At pH 6.0–6.1, acrosome-reacted spermatozoa could bind to the egg plasma membrane, but were unable to fuse with it. Similar results were obtained with media buffered with Hepes and Bes. The block of sperm-egg fusion at low pH appeared to be reversible since the eggs that were not penetrated by spermatozoa at low pH were penetrated when they were returned to more alkaline media.     

Reductive N,N-dimethylation of amino acid and peptide derivatives using methanol as the carbonyl source

Formaldehyde is readily formed from methanol in the presence of palladium-on-charcoal and air. The use of this methanolic formaldehyde solution for the reductive methylation of amino groups in amino acid and peptide derivatives by catalytic hydrogenation has been studied and found to be superior to the use of aqueous formaldehyde because no contaminating paraformaldehyde is present. Some data on N-isopropylation are given.     

Penetration of Celery and Alfalfa Roots by Pratylenchus penetrans as Affected by Temperature

A greater percentage of females than juveniles or males of P. penetrans penetrated celery roots grown in infested soil at 5, 18, or 30 C; the difference was greatest at 5 C. The time of initial penetration of alfalfa seedlings inoculated with single nematodes on water agar varied with temperature. Females penetrated the seedlings earlier and over a wider range of temperatures than did males or juveniles. The rate of penetration was highest for females. After initial penetration, the penetration rate decreased with time. At 13-28 C, approximately 80% of roots were penetrated by females and only 25-30% by males and juveniles by the end of the experiment.     

Penetration in vitro of zona-free pig oocytes by homologous and heterologous spermatozoa

We examined the penetrability of pig, rat and bull spermatozoa into zona-free pig oocytes. Frozen-thawed boar spermatozoa penetrated into both zona-intact and zona-free oocytes with similar efficacy in a modified Tris-buffered medium (mTBM) supplemented with BSA and caffeine, but not in medium without caffeine. Rat epididymal spermatozoa did not readily penetrate into zona-free pig oocytes in mTBM with BSA. However, when a modified Krebs-Ringer bicarbonate solution was used, penetration rate varied with sperm concentrations at insemination: 79% of the oocytes were penetrated at 1.0 x 10(6) cells/ml, but very few at 0.1 x 10(6) and 10.0 x 10(6) cells/ml. In all oocytes penetrated, no activation was observed and the sperm nucleus was fully decondensed but did not transform into a male pronucleus. Frozen-thawed bull spermatozoa were also found to penetrate into zona-free pig oocytes in mTBM with BSA, caffeine and heparin: higher penetration rates were obtained with 1.0 x 106 and 10.0 x 10(6) spermatozoa/ml compared with 0.1 x 10(6) spermatozoa/ml. The penetration rate with 1.0 x 10(6) spermatozoa/ml was stable in five different bulls. All oocytes penetrated were activated and male pronuclear formation was observed in 57-79% of the penetrated oocytes. These results suggest that capacitation or the acrosome reaction is required for boar, rat, and possibly, bull spermatozoa to penetrate into zona-free pig oocytes. Bull spermatozoa can easily induce activation of pig oocytes and form male pronuclei, but rat spermatozoa cannot do so, indicating species differences in the ability of spermatozoa to activate pig oocytes and to transform to male pronuclei in the ooplasm.     

Formaldehyde prepared from paraformaldehyde is stable

For critical histological investigations, tissue fixation is sometimes carried out in formaldehyde freshly prepared from paraformaldehyde by heating. The purity of formaldehyde produced in this way is superior to that of commercial stock solutions. We studied the stability of freshly prepared formaldehyde solutions by determination of pH and titration of acid, which reflect the formation of formic acid. It was found that very small amounts of acid are produced during the heating of paraformaldehyde. Prolonged heating or storage of freshly prepared formaldehyde for up to 8 days did not significantly increase the amount of acid. It was also found that heating of the paraformaldehyde is not necessary, since depolymerization may take place at room temperature.

We conclude that formaldehyde prepared from paraformaldehyde remains stable for considerable periods of time, and it is therefore unnecessary to prepare it immediately prior to fixation. Also, in many cases, buffering of the fixative may be omitted, since only minor changes in the pH occur during fixation.     

Formaldehyde prepared from paraformaldehyde is stable

For critical histological investigations, tissue fixation is sometimes carried out in formaldehyde freshly prepared from paraformaldehyde by heating. The purity of formaldehyde produced in this way is superior to that of commercial stock solutions. We studied the stability of freshly prepared formaldehyde solutions by determination of pH and titration of acid, which reflect the formation of formic acid. It was found that very small amounts of acid are produced during the heating of paraformaldehyde. Prolonged heating or storage of freshly prepared formaldehyde for up to 8 days did not significantly increase the amount of acid. It was also found that heating of the paraformaldehyde is not necessary, since depolymerization may take place at room temperature.

We conclude that formaldehyde prepared from paraformaldehyde remains stable for considerable periods of time, and it is therefore unnecessary to prepare it immediately prior to fixation. Also, in many cases, buffering of the fixative may be omitted, since only minor changes in the pH occur during fixation.     

Mechanisms of microbial movement in subsurface materials.

The biological factors important in the penetration of Escherichia coli through anaerobic, nutrient-saturated, Ottawa sand-packed cores were studied under static conditions. In cores saturated with galactose-peptone medium, motile strains of E. coli penetrated four times faster than mutants defective only in flagellar synthesis. Motile, nonchemotactic mutants penetrated the cores faster than did the chemotactic parental strain. This, plus the fact that a chemotactic galactose mutant penetrated cores saturated with peptone medium at the same rate with or without a galactose gradient, indicates that chemotaxis may not be required for bacterial penetration through unconsolidated porous media. The effect of gas production on bacterial penetration was studied by using motile and nonmotile E. coli strains together with their respective isogenic non-gas-producing mutants. No differences were observed between the penetration rates of the two motile strains through cores saturated with peptone medium with or without galactose. However, penetration of both nonmotile strains was detected only with galactose. The nonmotile, gas-producing strain penetrated cores saturated with galactose-peptone medium five to six times faster than did the nonmotile, non-gas-producing mutant, which indicates that gas production is an important mechanism for the movement of nonmotile bacteria through unconsolidated porous media. For motile strains, the penetration rate decreased with increasing galactose concentrations in the core and with decreasing inoculum sizes. Also, motile strains with the faster growth rates had faster penetration rates. These results imply that, for motile bacteria, the penetration rate is regulated by the in situ bacterial growth rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mechanisms of microbial movement in subsurface materials

The biological factors important in the penetration of Escherichia coli through anaerobic, nutrient-saturated, Ottawa sand-packed cores were studied under static conditions. In cores saturated with galactose-peptone medium, motile strains of E. coli penetrated four times faster than mutants defective only in flagellar synthesis. Motile, nonchemotactic mutants penetrated the cores faster than did the chemotactic parental strain. This, plus the fact that a chemotactic galactose mutant penetrated cores saturated with peptone medium at the same rate with or without a galactose gradient, indicates that chemotaxis may not be required for bacterial penetration through unconsolidated porous media. The effect of gas production on bacterial penetration was studied by using motile and nonmotile E. coli strains together with their respective isogenic non-gas-producing mutants. No differences were observed between the penetration rates of the two motile strains through cores saturated with peptone medium with or without galactose. However, penetration of both nonmotile strains was detected only with galactose. The nonmotile, gas-producing strain penetrated cores saturated with galactose-peptone medium five to six times faster than did the nonmotile, non-gas-producing mutant, which indicates that gas production is an important mechanism for the movement of nonmotile bacteria through unconsolidated porous media. For motile strains, the penetration rate decreased with increasing galactose concentrations in the core and with decreasing inoculum sizes. Also, motile strains with the faster growth rates had faster penetration rates. These results imply that, for motile bacteria, the penetration rate is regulated by the in situ bacterial growth rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

A high-performance humidity control system for tiny animals: demonstration of its usefulness in testing egg hatchability of the two-spotted spider mite, Tetranychus urticae

We developed a computer-based system for controlling water vapor conditions (i.e., humidity) using a two-flow method in which streams of humidified and dehumidified air were combined in an acrylic container. The flow rate of each stream was independently controlled to adjust relative humidity (RH). In this system, humidification from 15 to 90?% RH and dehumidification from 90 to 15?% RH at an air temperature (AT) of 25?°C were properly operated with short time constants of 4.3 and 10?min, respectively. Tetranychus urticae egg hatchability was then examined at 20-95?% RH and 25?°C AT. The coefficients of variation of RH were low (0.3-1.5?%). Egg hatchability in a polystyrene Petri dish was lower at 20?% RH than at 70-95?% RH. A delay in hatching was also observed at 70?% RH for eggs tested on a leaf disk placed on water-soaked cotton; this delay was attributed to the AT being 1.4?°C lower on the leaf surface than on the inner surface of the dish. Our system is expected to be useful for further examination of ecological and behavioral responses in pest mites and for developing novel physical control measures using water vapor.     

Physicochemical stability of cimetidine amorphous forms estimated by isothermal microcalorimetry

The effect of humidity on the physicochemical properties of amorphous forms of cimetidine was investigated using differential scanning calorimetry, isothermal microcalorimetry, and x-ray diffraction analysis. Amorphous forms were obtained by the melting (amorphous form M [AM]) and the cotton candy (amorphous form C [AC]) methods. Thermal behaviors of AM and AC with or without seed crystals were measured using an isothermal microcalorimeter under various conditions of relative humidity (RH) and temperature, respectively. The crystallization kinetics of amorphous solids was analyzed based on 10 kinds of solid-state reaction models. AM transformed into form A at 11% RH, 50°C but transformed into a mixture of form A and monohydrate at 51% and 75% RH at 25°C. The mean crystallization times (MCTs) of the heat flow curve of AM and AC at 11% RH, 50°C were 47.82 and 32.00 hours, respectively, but at 11% RH, 25°C both were more than 4320 hours. In contrast, AC transformed into form A under all storage conditions. The MCTs of AC at 51% and 75% RH were 29.61 and 11.81 hours, respectively; whereas the MCTs of AM were 46.79 and 15.52 hours, respectively. The crystallization of amorphous solids followed the three-dimensional growth of nuclei (Avrami equation) with an induction period (IP). The IP for AM at 11% RH, 50°C was more than 2 times that for AC, but the difference in the crystal growth rate constant (CR) between AC and AM was within 10%. The IP for AM at 75% RH, 25°C was reduced to only 10% of the IP at 51% RH with increasing humidity, but the CR did not change significantly. In contrast, the IP for AC was slightly reduced at 75% RH compared with 51% RH, but the CR was about 5 times greater. At 75% RH, 25°C, the IP and CR of AM were about one-fourth the values of AC. This result suggests that the crystallization process consists of an initial stage during which the nuclei are formed and a final stage of growth.     

Survival and efficacy of steinernema carpocapsae in an exposed environment

Factors affecting the persistence and activity of the infective juveniles (IJs) of the nematode Steinernema carpocapsae ’Mexican’ strain on the foliage of bean plants were determined at 45, 60 and 80% relative humidity (RH). The rate of nematode mortality was related to the RH. A gradual reduction in nematode survival was recorded during a 6 h exposure period at 80% and 60% RH, whereas at 45% RH high mortality was observed within 2 h. Addition of the antidesiccant ‘Folicote’ (6% w/w) to the nematode suspension was most effective in ensuring IJ survival at 60% RH, resulting in 38–60% increase in viability during 6 h of exposure. At 80% RH ‘Folicote’ treatment resulted in only 10–20% increase in IJs viability, as compared with non‐treated IJs. At 45% RH, ‘Folicote’ treatment did not significantly increase IJ survival (P>0.05). Survival of the IJs on tomato and soybean leaves was 30–35% higher than of those recovered from leaves of cotton, pepper and bean as well as from filter paper. At 60% RH, IJ movement ceased within 45–60 min of exposure and the nematode body shrank. However, nematode pathogenicity remained almost unaltered up to 4 h of exposure, resulting in 75% mortality of larvae of the Egyptian cotton worm Spodoptera littoralis. A drastic reduction in the nematodes’ efficacy was recorded when the insects were introduced 6 and 8 h after nematode application.     

Root growth in seedlings of annual pasture species

Summary The mean rate at which roots of 12 annual pasture species penetrated a yellow sand to a depth of 80 to 90 cm varied from 0.8 to 3.2 cm per day.Penetration rate was closely correlated with seed weight until roots reached a depth of about 20 cm. Thereafter rates became progressively less dependent on seed size.Penetration rate varied with time. In six species a minimum rate was reached at a depth of 18 to 24 cm. In two species rhythmic fluctuations in root penetration rate appeared to be associated with the development of new leaves on the shoot.Shading the shoots substantially reduced root penetration rate but the rhythmic fluctuations persisted. These observations are consistent with the hypothesis that the rate of root penetration is determined by the supply of metabolites to the root system.     

Penetration of soybean root systems by abscisic Acid isomers

The penetration of soybean (Glycine max L. cv. Ransom) root systems by exogenously applied isomers of abscisic acid was monitored by measuring the concentration of the chemical in the xylem exudate of root systems exposed to a three bar hydrostatic pressure difference. The cis-trans isomer penetrated more readily than the trans-trans isomer; however, up to 6 hours was needed to reach steady-state values. Exogenous abscisic acid also decreased volume flux through the root system and increased total carbon dioxide efflux from the vessel containing the root system.     

Reversible inhibition of the pollen germination and the stigma penetration in Crocus vernus ssp. vernus (Iridaceae) following fumigations with NO2, CO, and O3 Gases

We assessed the pollen hydration, the pollen germination, and the stigma papilla penetration of CROCUS VERNUS subsp. VERNUS (Iridaceae) after 2 h fumigations with O (3), NO (2), and CO gases within humidified (90 - 100 % RH) box experiments. When the pollen and the pistil were separately fumigated, the pollen retained the capacity to emit a tube which penetrated papilla, and the stigma papillae retained the receptivity; when the pistils were first pollinated and then fumigated, the capacity of pollen to hydrate was not affected, but the germination was significantly reduced. The vulnerability to gases became evident at 0.3 ppm O (3), 0.2 ppm NO (2), and 0.5 ppm CO. The inhibition curves as a function of the gas concentrations were of an exponential type, and they saturated at 2 ppm NO (2), 25 ppm CO, and 0.5 ppm O (3), with germination percentages of 17 %, 27 %, and 60 %, respectively. Both the pollen germination and the papilla penetration were fully restored by prolonging for 60 - 90 min the incubation at 90 - 100 % RH, after the cessation of fumigations. The vulnerability of the pollen-papilla system is discussed.     

Effect of environmental conditions during heating on commercial spore strip performance.

Commercial biological indicator spore strips in glassine envelopes, produced by three manufacturers, were evaluated by fraction-negative procedures after being heated at 121.0 +/- 0.05 degrees C. Only one type of spore strip met the manufacturer's specifications. The strips of one manufacturer were further evaluated by fraction-negative and survivor curve-plate count procedures after being heated under several conditions (enclosed in glassine envelopes, in trypticase soy broth plus 0.0015% bromocresol purple, in Trypticase soy broth alone in Water for Injection, directly); Trypticase soy broth plus bromocresol purple and tryptic soy agar, respectively, were used as recovery media. The heating condition affected the D-value of the spore strip. Recovery procedures also had an effect; in all cases, the D-values obtained from the survivor curve tests were larger than those obtained from fraction-negative tests carried out under the same conditions. To determine if the differences in D-values between the two evaluation procedures were caused by the recovery media, we evaluated, by both methods, one type of spore strip heated directly and in glassine envelopes, using tryptic soy agar plus bromocresol purple and Trypticase soy broth plus 1.5% agar, respectively, as the recovery media. The survivor curve results showed that for both enclosed and unenclosed spore strips, there was a marked difference between the two recovery media; however, there was no difference when fraction-negative tests were used.