Microbiological Evaluation of a Large-Volume Air Incinerator

Two semiportable metal air incinerators, each with a capacity of 1,000 to 2,200 standard ft(3) of air per min, were constructed to sterilize infectious aerosols created for investigative work in a microbiological laboratory. Each unit has about the same air-handling capacity as a conventional air incinerator with a brick stack but costs only about one-third as much. The units are unique in that the burner housing and combustion chamber are air-tight and utilize a portion of the contaminated air stream to support combustion of fuel oil. Operation is continuous. Aerosols of liquid and dry suspensions of Bacillus subtilis var. niger spores and dry vegetative cells of Serratia marcescens were disseminated into the two incinerators to determine the conditions required for sterilization of contaminated air. With the latter organisms (concentration 2.03 x 10(7) cells/ft(3) of air), a temperature of 525 F (274 C), measured at the firebox in front of the heat exchanger, was sufficient for sterilization. To sterilize 1.74 x 10(7) and 1.74 x 10(9) wet spores of B. subtilis per ft(3), the required temperature ranged from 525 to 675 F (274 to 357 C) and 625 to 700 F (329 to 371 C), respectively. Air-sterilization temperature varied with each incinerator. This was because of innate differences of fabrication, different spore concentrations, and use of one or two burners With dry B. subtilis spores (1.86 x 10(8)/ft(3)), a temperature of 700 F was required for sterilization. With dry spores, no difference was noted in the sterilization temperature for the two incinerators.     

Containment of Microbial Aerosols in a Microbiological Safety Cabinet

A microbiological safety cabinet was evaluated to determine conditions under which microorganisms might escape. Tests were conducted under three cabinet-closure conditions, various airflow velocities, and different laboratory operations, with 10(5), 1.1 x 10(5), and 10(6) microorganisms per cubic foot of cabinet space released per min for 5 min. The data revealed that (i) escape of a human infectious dose is possible when the cabinet is used with the glove panel off; (ii) the number of organisms that escaped from the cabinet increased with a decrease in air velocity; and (iii) an increase in the number of laboratory operations resulted in an increase in the number of organisms that escaped. Thus, when the glove panel was off, the cabinet was only safe for operations that released a small number of microorganisms into the cabinet, whereas the cabinet was safe for operations of significantly greater hazard when used with the glove panel on but with the gloves unattached.     

Light microscopy of glial cells in turtles and birds

Summary Four classes of glial cells can be recognized in the central nervous system of turtles and birds on the basis of nuclear characteristics (methylene blue) and external morphology (Golgi technique). It seems likely that astrocytes and ependymal cells have a similar origin and function, but no evidence has been seen to indicate that transitional forms exist between astrocytes and oligodendrocytes or microgliacytes. Ependymal cells in the tectum and forebrain are covered by lamellate excrescences which are absent on cells in the spinal cord. Protoplasmic astrocytes are restricted to the gray matter. In the turtle they have an elongate shape characteristic of primitive elements, but stellate forms typical of mammals predominate in the bird. Fibrous astrocytes are abundant in the white matter. Endfeet are lacking in the turtle except on cells located near the pia; they are common for all elements in the bird and can sometimes be observed to outline the course of capillaries. Oligodendrocytes are identical to mammalian and amphibian forms. Small, round somata and long, thin processes are typical of types I and II while a tubular reticulum or membranous sheath characterizes type IV. The lack of a well defined somata and absence of transitional forms (type III) are compatible with the possibility that type IV is not a true cell type but corresponds to the inner cytoplasmic tongue of myelin. Microgliacytes are present in gray and white matter; they have a smaller overall size in the turtle and young chicken than in adult birds.Supported by a postdoctoral fellowship from the United States National Institutes of Health, NB 28,013-01Al.     

STUDIES OF NECROTIC LESIONS IN CORN STALKS

Littlefield , Larry J., and Roy D. Wilcoxson . (U. Minnesota, St. Paul.) Studies of necrotic lesions in corn stalks . Amer. Jour. Bot. 49(10): 1072–1078. Illus. 1962.—In 3-day-old necrotic lesions in corn stalks caused by Fusarium graminearum, ground parenchyma cells were discolored and small amounts of a dark substance were present in the cells. The walls of phloem cells were also slightly discolored and a small amount of dark substance was present in the xylem cells. In older lesions the discoloration of parenchyma and phloem cells was more intense; many of the cells contained occluding substances; many phloem protoplasts collapsed, and xylem cells were partially to completely occluded. The occluding substance filling the cells appeared to be translocated from the lesion into the vessel elements extending beyond the lesion so that the bundles appeared as long, dark streaks in the stalk. The occluding substance in xylem, but not in phloem or parenchyma, stained with ruthenium red, a result indicating presence of pectin. Pectinase, however, did not remove the occluding substance. The pectinase dissolved the parenchyma cells in healthy tissues but not in the necrotic lesions. Necrosis in naturally infected plants began as small lesions, but the parenchyma cells quickly dissolved leaving the vascular bundles free of ground parenchyma. No occlusions were found in the central vascular system; a few xylem cells in the peripheral vascular system were occluded with the same substance observed in artificially inoculated plants. Phloem was entirely destroyed by the pathogen. The necrosis prevented upward movement of dye solution in the stalk, but did not measurably affect transpiration, probably because the lesions were not large. Yield was reduced in plants when lesions involved more than 50% of the tissue in inoculated internodes. Smaller lesions had no effect on yield.     

Vitamin K5 as a Fungistatic Agent

The effectiveness of vitamin K(5) in controlling the growth of different molds at varying pH levels in a culture medium, in tomato juice, and in several berry purees was studied. The molds studied were Aspergillus, Botrytis, Hormodendrum, Mucor, and Penicillium. The results showed that vitamin K(5) was effective as a fungistatic agent at concentrations ranging from 0.006 to 0.02%.     

The inhibition of catalase by glutathione

Reduced glutathione (GSH) inhibited catalase activity in a dose-dependent manner. DL-dithiothreitol (DL-DTT) and dithioerythritol (DTE) also inhibited catalase activity. The inhibition of catalase by GSH and DL-DTT could be reduced by NADPH. Polyacrilamide gel electrophoresis demonstrated the inhibition was partially reversible. The inhibition of catalase by GSH appeared to be partly due to superoxide radicals, since it was inhibited by active manganese superoxide dismutase, but not by heat-inactivated enzyme. Other chemical species also appear to take part in the inhibition, but they could not be identified.     

Sodium-N-butyrate induces cytoskeletal rearrangements and formation of cornified envelopes in cultured adult human keratinocytes

Abstract The technique developed in our laboratory allows us to culture multilayered, stratified sheets of human keratinocytes, which can be used to cover the burn wounds of patients. Organization of cells in these cultures resembles stratum germinativum and stratum spinosum but there are only a few fully keratinized cells and the stratum corneum is not developed. Since the fully differentiated sheets may offer additional advantages as epidermal transplants, attempts were made to enhance the degree of differentiation in vitro. In the present study sodium-N-butyrate (NaB) was used as a differentiating agent and its effect on the cell cycle and cytoarchitecture of epidermal cells was investigated. Incubation of keratinocytes in the presence of 2.5 mM NaB induced the appearance of enucleated cornified envelopes, covering approximately 70–80% of the surface of the cultures. Their appearance correlated with a decrease in expression of keratin K13, previously shown to be inhibited during terminal differentiation of human keratinocytes. An increase in transglutaminase transferase activity was also observed. The induction of cornified layers also correlated with an increase in the amount of microfilament (MF)-associated actin. NaB also induced changes in the cell cycle distribution of the keratinocyte cultures. A decrease in the proportion of S and G_1B phase cells was paralleled by an increase in G_1A cells, maximally expressed 30–48 h following addition of the inducer. Interestingly, NaB also induced a cell arrest in G₂ phase. These cell cycle perturbations preceded the onset of keratinocyte differentiation. The results indicate that the enhanced differentiation of human keratinocytes in the presence of NaB may serve as a means to produce epidermal sheets with improved properties for transplantation in a clinical setting. It also serves as an in vitro model system to study the interrelationships between biochemical events and cell cycle changes accompanying differentiation.     

Differential Expression of mRNA and Protein Encoding Retinal and Pineal S-Antigen During the Light/Dark Cycle

S-Antigen is a soluble cell protein unique to the retina and pineal gland. In the former, it is a well-characterized molecule that participates in light-induced signal transduction in photoreceptor cells. In the latter, the functional role is presently not known. The expression of S-antigen and its mRNA was examined in the rat retina and pineal gland throughout the diurnal cycle and with light interruption of the dark cycle. A cDNA for rat S-antigen was isolated from a pineal gland library to examine the mRNAs. A 1.7-kb mRNA for S-antigen was observed in both the pineal gland and the retina. Retinal S-antigen mRNA was expressed throughout the diurnal cycle and increased with light interruption of the dark cycle. In contrast, pineal gland S-antigen mRNA levels were detectable only during the dark and were absent preceding and during light. The phenotypic expression of immunoreactive S-antigen, identified with two S-antigen monoclonal antibodies (MAbs), MAb A9C6 and MAb C10C10, was analyzed by sodium dodecyl sulfate (SDS)-polyacrylamide gel (PAGE) and isoelectric focusing (IEF) electrophoresis. Immunoblot analysis of gels after SDS-PAGE revealed a single 46-kDa protein in retina. In contrast, two bands of approximately 43 and 46 kDa were identified in the pineal gland. Immunoblots of the retinal extracts separated by IEF electrophoresis revealed five S-antigen isomers, which vary quantitatively throughout the diurnal cycle and when light interrupted the dark cycle. Immunoblots of the pineal gland samples separated by IEF electrophoresis indicated that the pineal gland possesses four pineal gland-specific forms of S-antigen in addition to the five forms present in the retina. The differences observed in the mRNA and protein analyses suggest tissue-specific structural components for S-antigen in the retina and pineal gland that are not regulated in the same manner.