Effect of multilevel laboratory rat caging system on the well-being of the singly-housed Sprague Dawley rat.

Current regulations emphasize that good husbandry practices allow animals to engage in species appropriate postural adjustments without touching the enclosure walls. This study evaluated the well-being of rats housed in a commercially available multilevel rat caging system, with or without access to the upper level of the caging. The evaluation methodologies included assessment of behavioral observations in the home cage, physiological assessment of metabolism and immune function, and determination of the affective state using a spatial cognitive bias assay. The study determined that rats that were provided access to the full multilevel cage during testing after initial restriction to the lower level of the cage demonstrated behavioral changes consistent with a positive affective state, while those with no changes to their housing situation had no significant differences in their affective states. Rats that were consistently housed with access restricted to the lower level of the cage exhibited a tendency to increased neutrophil:lymphocyte ratios as compared with those provided with access to all levels of the multilevel cage. There were no differences in body weight demonstrated between the experimental groups. Overall use of the cage space, as documented through analysis of behavioral observations in the home cage, demonstrated no significant differences in preferred location in the cage during the light or dark cycles, though rats with access to both levels of the cage were significantly more active during the light cycle. The results of this study suggest that the use of a multilevel caging system may improve the well-being of rats used in research.

Operation of magnetically assisted fluidized beds in microgravity and variable gravity: experiment and theory.

The conversion of solid waste into useful resources in support of long duration manned missions in space presents serious technological challenges. Several technologies, including supercritical water oxidation, microwave powered combustion and fluidized bed incineration, have been tested for the conversion of solid waste. However, none of these technologies are compatible with microgravity or hypogravity operating conditions. In this paper, we present the gradient magnetically assisted fluidized bed (G-MAFB) as a promising operating platform for fluidized bed operations in the space environment. Our experimental and theoretical work has resulted in both the development of a theoretical model based on fundamental principles for the design of the G-MAFB, and also the practical implementation of the G-MAFB in the filtration and destruction of solid biomass waste particles from liquid streams.

A microwave-powered sterilizable interface for aseptic access to bioreactors that are vulnerable to microbial contamination.

Novel methods and apparatus that employ the rapid heating characteristics of microwave irradiation to facilitate the aseptic transfer of nutrients, products, and other materials between microbially sensitive systems and the external environment are described. The microwave-sterilizable access port (MSAP) consists of a 600-W magnetron emitting at a frequency of 2.45 GHz, a sterilization chamber with inlet and outlet flow lines, and a specimen transfer interface. Energy is routed to the sterilization chamber via a coaxial transmission line where small quantities of water couple strongly with the incident radiation to produce a superheated vapor phase. The efficiency of energy transfer is enhanced through the use of microwave susceptors within the sterilization chamber. Mating surfaces are thermally sterilized through direct contact with the hot gas. Efficacy has been demonstrated using the thermophile Bacillus stearothermophilus.

Dissolved oxygen determination by electrocatalysed chemiluminescence with in-line solid phase media.

Dissolved elemental oxygen is determined in a flowing aqueous stream using glucose oxidase to catalyse the reaction between D-glucose and O2 to produce hydrogen peroxide. The levels of the resulting H2O2 are detected and quantified by luminol chemiluminescence using in-line solid phase media for pH adjustment of the reagent stream and for controlled release of the luminophore. The reaction is initiated by electrochemical catalysis. By the use of excess D-glucose in the reagent flow stream, the intensity of chemiluminescence is rendered proportional only to fluctuations in the dissolved O2 concentration. The methodology provides a means for the detection of aqueous O2 in the range 0-10 mg/L.

Toxoplasma pneumonia: cytologic diagnosis by bronchoalveolar lavage.

Two cases of toxoplasma pneumonia in immunocompromised hosts are reported. The diagnoses were made by the identification of trophozoites in bronchoalveolar lavage material. The organisms were more readily identified in the air-dried Diff-Quik-stained smears. Cytologic findings and correlation with postmortem examination material in one case are described. A high index of suspicion for this pathogen, as well as screening cytologic preparations at medium to high magnification may increase the diagnostic rate for this uncommon but treatable disease.

Addition of rifampin to combination antibiotic therapy for Pseudomonas aeruginosa bacteremia: prospective trial using the Zelen protocol.

A multicenter, prospective randomized trial was conducted to determine if the addition of rifampin to a combination therapy of an antipseudomonal beta-lactam agent and aminoglycoside improves the outcome of patients with Pseudomonas aeruginosa bacteremia. The Zelen protocol for randomized-consent design was used. Consent was sought only from patients randomized to the experimental therapy (rifampin+). If the experimental therapy was refused, the patient would then receive the standard combination therapy (control); however, when outcome was evaluated, all patients randomized to the rifampin+ group, including those that declined rifampin, were compared with the control group. One hundred twenty-one consecutive hospitalized patients with positive blood cultures for P. aeruginosa were enrolled. Entry was stratified for prior use of empiric antipseudomonal antibiotics, neutropenia, severity of illness, and presence of pneumonia. Fifty-eight patients were randomized to receive rifampin (600 mg orally every 8 h for the first 72 h and then every 12 h for a total of 10 days) plus a beta-lactam agent plus an aminoglycoside. Sixty-three received the standard therapy of a beta-lactam plus an aminoglycoside agent (control). Bacteriologic cure occurred significantly more frequently in patients randomized to the rifampin+ regimen. Breakthrough or relapsing bacteremias occurred in 2% of the three-drug (rifampin+) group, compared with 14% for the two-drug (standard therapy) group. Despite this favorable trend in bacteriological response, no significant differences in survival were seen for the two treatment groups. Rifamycin derivatives warrant further clinical study as antipseudomonal agents. The Zelen protocol appears well suited for comparative trials of antimicrobial agents.

Atypical community-acquired pneumonia: concurrent infection with Chlamydia psittaci and Mycobacterium tuberculosis.

We have presented a case of combined pulmonary infection with Chlamydia psittaci and Mycobacterium tuberculosis, both documented by culture of lymph nodes and respiratory secretions. We describe it not only as an unusual occurrence, but also to illustrate the importance of a systematic and thorough diagnostic approach to every case of pneumonia.

Esophagitis in the immunocompromised host: role of esophagoscopy in diagnosis.

Thirty episodes of presumed infectious esophagitis in immunocompromised patients were investigated by means of esophagoscopy. Indications for esophagoscopy included dysphagia, odynophagia, and retrosternal pain. Factors potentially predisposing patients to esophagitis included previous exposure to radiation, recent cytotoxic chemotherapy, recent antibiotic therapy, corticosteroid therapy, and neutropenia. Sixteen of the 18 barium esophagograms done before esophagoscopy was performed revealed abnormalities; in 14 cases the results were consistent with infectious esophagitis. Abnormalities were noted during 27 of 30 esophagoscopy procedures. Visual findings were consistent with candidal esophagitis in 18 cases, with viral esophagitis in four, and with both in one. Specific infectious diagnoses were established by culture or histology in 17 episodes: 12 of candidal esophagitis, two of herpes simplex esophagitis, two of concomitant candidal and herpetic esophagitis, and one of enteroviral esophagitis. Specific noninfectious diagnoses were made in two episodes, and the esophagus was found to be normal in three. No specific diagnosis was made in eight episodes although visual examination indicated the presence of esophagitis. The only postesophagoscopy complications recorded were isolated episodes of spiking fever in three patients. In this compromised-host population with presumed infectious esophagitis, esophagoscopy resulted in a rapid and specific infectious diagnosis in 57% of episodes.

Phase II trial of methylglyoxal bis (guanylhydrazone) (MGBG) in advanced head and neck cancer.

Methylglyoxal bis (guanylhydrazone) (MGBG) is an inhibitor of polyamine synthesis. In vitro studies demonstrate the accumulation of some tumor cells in S and G2 phases of the cell cycle. Nineteen patients with advanced head and neck cancer were entered in a Phase II trial of MGBG. MGBG, 500 mg/M2, was administered as a brief intravenous infusion weekly for 4 weeks, then every 2 weeks. Dose modifications were based on cumulative toxicity after 2 weekly treatments. All but three patients had prior exposure to chemotherapy for disease recurrence. Of 17 patients evaluable for response and toxicity, one brief partial response was observed. The most common toxicities were mild to moderate nausea, vomiting, diarrhea, and stomatitis. Myelosuppression occurred in three patients. Dose modifications were required in four patients; a maximum dose of 700 mg/M2 was tolerated. The results of four other Phase II single and combination chemotherapy trials of MGBG in head and neck cancer are reviewed. The single agent response rate in 59 patients was 22% (range, 6%-41%). The poor response rate observed in this trial was similar to that in other trials in which a heavily pretreated group of patients was evaluated. It is concluded that single agent MGBG is not a useful drug in heavily pretreated recurrent disease patients. However, because of its biochemical effects, further testing in combination with cycle specific agents and in larger numbers of patients with minimal prior treatment may be warranted.