Histone acetylation in insect chromosomes.

Acetylation of histones takes place along the salivary gland chromosomes of Chironomus thummi when RNA synthesis is active. It can be observed but not measured quantitatively by autoradiography of chromosome squashes. The "fixatives" commonly used in preparing squashes of insect chromosomes preferentially extract the highly acetylated "arginine-rich" histone fractions; the use of such fixatives may explain the reported absence of histone acetylation in Drosophila melanogaster.

Virus penetration of examination gloves.

Examination gloves worn for protection from biohazards were sampled and evaluated for their ability to exclude virus particles. We found that thin gloves manufactured from polyethylene or polyvinyl chloride are ineffective barriers while gloves of thin latex are superior but not without failure. Polyethylene and polyvinyl chloride gloves had failure rates of 40% and 22%, respectively. Following exposure to the common disinfectant, 70% ethanol, these failure rates increased to 94% and 56% for polyethylene and polyvinyl chloride gloves, respectively. Latex, although permeable to ethanol, was penetrated by virus less than 1% of the time regardless of whether the latex had been pre-exposed to disinfectant or not. This study highlights the need for caution on the part of those who rely upon examination gloves for protection from infectious agents as well as the need for establishing more adequate standards and testing procedures for their manufacture.

On the quantitation of SV40 virus by plaque assay and immunoperoxidase technique.

Procedures are described for the quantitation of SV40 virus infectivity by plaque formation within 7 days and T antigen assay by the sensitive and economical indirect immunoperoxidase technique.

Evaluation of a room for tuberculosis patient isolation using theatrical fog.

OBJECTIVE: To develop a method to evaluate directional airflow patterns, air dilution, and air mixing in facilities where tuberculosis patients are seen. DESIGN: A tuberculosis patient isolation room was evaluated by analyzing pressure differential between the room and the corridor and by using theatrical fog to visualize room air movement and impact of dilution and exchange, as well as air capture and displacement. Tracer gas was compared to fog results and used to calculate air exchange rates. SETTING: A small research hospital. RESULTS: By adding theatrical fog to the patient room at several locations, we quickly learned that most of the air entering the room through the transom and around the door to the corridor was exhausted through the three exhaust vents. Little air appeared to move toward the exhaust fan. For comparison and to confirm the room air exchange rate, tracer gas was distributed and sampled. The kinetics of decay were very similar whether the tracer gas and room air were mixed during sampling or not. CONCLUSIONS: The fog procedure allowed good visual confirmation of air mixing and airflow patterns and provided quantitative data for evaluating the efficacy of air capture and displacement or dilution and exchange.

A review of some available radioactive and non-radioactive substitutes for use in biomedical research.

The unavailability of disposal facilities for long-lived low-level radioactive waste (LLRW), expense associated with its disposal, and, for some generators, limitation of space to decay short half-life radioactive materials has prompted the search for alternatives to radiochemical techniques. Some of these alternatives are presented below.

Detecting removable surface contamination.

Although surveying for radioactive contamination by wiping surfaces is the norm, this practice can be highly variable and may be inefficient for detecting low-energy beta emitters. Relying on wipe testing may likewise be an inefficient use of personnel and may seriously underrepresent the amount of contamination present. In general practice, it is better to clean and, where applicable, renew surfaces regularly as part of standard operating protocols and work practices.

Management of mixed wastes from biomedical research.

Mixed radioactive and chemical wastes generated by biomedical research were characterized, and various treatment methods for reducing their volume were evaluated. These wastes consist primarily of organic solvents used in the extraction and purification of radiolabeled biomolecules that are contaminated with low levels of the long-lived radionuclides, 3H and 14C. The Rockefeller University's mixed wastes fall into three broad chemical categories: phenol/chloroform, acetonitrile/water, and mixtures of miscellaneous solvents such as carbon tetrachloride, benzene, and other hazardous chemicals. Currently, with the exception of liquid scintillation cocktails (deregulated in 1981), there are no commercial disposal outlets for mixed wastes nor may they be stored legally for more than 90-180 d. Most of these mixed wastes can be effectively rendered into nonradioactive chemical and aqueous radioactive waste, both of which can be disposed of in accordance with existing regulations. However, to do so requires a Resource Conservation and Recovery Act (RCRA) Part B permit for licensure as a treatment, storage, and disposal facility. For many university research facilities, this may require financial and personnel resources disproportionate to the small amounts of waste produced. Also, such treatment, if not done properly, presents potential occupational hazards from the direct handling of waste materials. Deregulation of certain mixed wastes would be the safest, most cost-effective, and practical method for dealing with many mixed wastes of biomedical origin. In any event, a national regulatory solution must be found.

Removable surface contamination at a biomedical research institution.

A rigorous, unannounced, campus-wide survey for removable surface contamination was performed at our institution. Wipe samples (n = 1,090) were collected from a variety of standardized locations in 45 large biomedical research laboratories that routinely use kBq-MBq (microCi-mCi) amounts of 3H, 14C, 32P, 35S, 51Cr, and 125I. The results showed a log-normal distribution for contamination, with about 90% of all samples below ten times background. Although working surfaces and equipment used in these laboratories can become contaminated with radioactive materials, especially by transfer from soiled gloves, the magnitude of the contamination is very small and typically restricted to surfaces, instruments, and equipment that are directly handled in the course of experimental work and which can be reasonably anticipated to be contaminated. These data suggest that contamination is not a significant problem in biomedical research laboratories at this institution and that the best protection from workplace contamination appears to continue to be the use of well-reviewed standard operating procedures and good work practices.

Biodegradation of radioactive animals.

The two most common disposal alternatives for animals contaminated with radioactive materials are incineration and burial. For most of the country burial has entailed shipping the carcasses to a commercial disposal facility at Barnwell, South Carolina, where it was landfilled along with other solid radioactive waste. Unfortunately, since 30 June 1994, this facility accepts waste generated by the states of the Southeast Compact only. Therefore, burial is no longer an option for most of the country's generators and incineration is an option only for those institutions which have, or have access to, an incinerator that is permitted to burn radioactive materials and that accepts animal carcasses with de minimis levels of radioactive contaminants. Many institutions, especially those in congested urban areas where the public does not support incineration, do not have viable outlets for radioactive animal carcasses. Interim, on-site storage poses problems of its own. Biodegradation of animal carcasses with dermestid beetles is an inexpensive approach to this waste management problem.

Elimination of tritiated thymidine from birds.

The kinetics with which tritiated thymidine is eliminated from birds and the concentration of radioactivity remaining in the carcass after 350-430 h were measured. Birds injected with tritiated thymidine eliminated 98% of the radioactivity injected within 28 h. Ninety-eight percent was identified in the excreta, and less than 2% of the radioactivity injected remained in the birds 28 h after injection.