Cryosurgery of breast cancer.

OBJECTIVE: To determine the feasibility and efficacy of cryosurgery of breast cancer. DESIGN: In phase 1, carcinogen-induced mammary adenocarcinomas in 13 Sprague-Dawley rats were treated by cryosurgery and were then examined for histopathologic change. In phase 2, transplantable mammary adenocarcinomas in 50 DBA/IJ mice were treated by cryosurgery to determine the effect of varying tumor temperatures, and duration and number of freeze-thaw cycles on tumor viability. In phase 3, 2- to 3-cm ultrasound-monitored cryolesions were formed in the breasts of 4 dogs and 4 sheep. These animals were followed up for procedure-related complications; the histopathologic necrosis of the cryolesions were correlated with the ultrasound images. Based on the results of these experiments, ultrasound-guided cryosurgery of breast cancer was initiated in a human clinical trial. RESULTS: In phase 1, a single, short-term (< 7 minutes) freeze killed only tumors smaller than 1.5 cm in diameter, despite an apparent decrease to -40 degrees C at the periphery of each tumor. In phase 2, varying the peripheral tumor temperature to as low as -70 degrees C, using a single, short-term (< 7 minutes) freeze did not alter the results from phase 1. If the ice ball fully encompassed the tumor, however, maintaining it for at least 15 minutes achieved 100% tumor kill independent of tumor size. In phase 3, creation of a reproducible ultrasound-monitored cryolesion was facilitated when 2 freeze-thaw cycles were performed. No procedure-related complications were noted. In the human trial, 2 invasive lobular carcinomas from 1 patient were treated by cryosurgery and were negative for persistent tumor by core needle biopsy performed 4 and 12 weeks after a well-tolerated procedure. CONCLUSIONS: In situ breast cryosurgery has been proved to be feasible and efficacious in small and large animal studies and has been successfully performed in 1 patient with breast cancer. The results of this study suggest that ultrasound-guided cryosurgery of breast cancer warrants further investigation.

Evaluation of isolator caging systems for protection of mice against challenge with mouse hepatitis virus.

Two isolator caging systems were evaluated against challenge with MHV-Y, an enterotropic strain of mouse hepatitis virus. The systems were similar in that they both used an identical shoebox cage equipped with a polycarbonate filter top incorporating a Reemay filter. They differed in that one system supplied HEPA-filtered air through a grommet in the filter lid so that the cage was pressurized slightly. A rack holding 60 cages (30 front and back) was utilized. Thirty cages without filter tops housed one mouse each that had been infected orally with 19,000 ID50 of MHV-Y and an uninfected cagemate. The remaining 30 cages, each housing 2 uninfected mice were divided into 3 groups of 10 cages. Group I cages (controls) had no filter top; Group II cages were equipped with filter tops; and Group III were equipped with filter tops and intracage HEPA-filtered air. The cages housing uninfected mice were interspersed between, above, below and behind cages housing infected mice. The uninfected mice were maintained in contact with the MHV-Y infected mice for 8 weeks. Transmission of MHV-Y was determined serologically by indirect ELISA. All mice housed within the Group I cages (control) seroconverted to MHV, while only 4 mice (2 cages) seroconverted in Group II, and no mice seroconverted in Group III.

The effects of intracage ventilation on microenvironmental conditions in filter-top cages.

Filter-top cages, while effective in reducing cross contamination by particulate material including microbes, can also cause accumulation of the waste gases carbon dioxide and ammonia as well as increased intracage relative humidity. A prototype system which provided each cage with 23 air changes per hour through a nozzle inserted in the filter lid was evaluated. The ventilated cageing system was effective in reducing intracage carbon dioxide, ammonia and relative humidity levels. Mean weekly carbon dioxide levels were 2900 ppm lower, ammonia levels 240 ppm lower and intracage relative humidity levels 8% lower in the ventilated cages than in unventilated controls.

Parvovirus-associated syndrome (Aleutian disease) in two ferrets.

There is a paucity of information regarding natural Aleutian disease, caused by a parvovirus in ferrets. With the increasing popularity of ferrets as household pets and laboratory animals, and with the advent of a USDA-approved rabies vaccine, the occurrence and the etiopathogenesis of naturally acquired diseases in ferrets needs to be documented. We present the clinical and laboratory findings associated with Aleutian disease in 2 domestic ferrets, one with the chronic wasting form of the disease and one with the central nervous system form.

Ketamine/xylazine/butorphanol: a new anesthetic combination for rabbits.

Ketamine is often used in combination with tranquilizers to produce surgical anesthesia in rabbits. While generally effective, there is considerable variation in the depth and duration of anesthesia achieved with ketamine combinations. Butorphanol is a mixed agonist-antagonist opioid that is widely used in a variety of other species. In this study, the commonly used ketamine (35 mg/kg)/xylazine (5 mg/kg) combination is compared with ketamine (35 mg/kg)/xylazine (5 mg/kg)/butorphanol (0.1 mg/kg). Rabbits were anesthetized on consecutive weeks with one of the two regimens. Physiologic parameters including heart rate, respiratory rate, blood pressure and arterial blood gases (pH, PO2, PCO2) were measured throughout anesthesia. Loss of palpebral, pedal and righting reflexes were recorded and reflexes were subsequently evaluated. The addition of butorphanol prolonged reflex loss to 140% (X = 68 min +/- 20 SEM) of control for palpebral reflex; 506% (X = 52 min +/- 18 SEM) of control for pedal reflex; and 159% (X = 128 min +/- 21 SEM) of control for righting reflex. Addition of butorphanol to ketamine/xylazine resulted in mild alterations in the physiologic changes traditionally associated with this combination. Butorphanol can be safely added to the ketamine/xylazine combination in rabbits and results in moderate increases in the duration of reflex loss.

Group G streptococcal lymphadenitis in rats.

Group G streptococci which have been isolated from the oral flora of rats are also normal inhabitants of the human skin, oropharynx, gastrointestinal tract, and female genital tract. This group of streptococci can cause a wide variety of clinical diseases in humans, including septicemia, pharyngitis, endocarditis, pneumonia, and meningitis. Ten days after oral gavage with 7,12-dimethylbenz[a]anthracene, 12 of 22 two-month-old, female, outbred, viral-antibody-free rats presented with red ocular and nasal discharges and marked swelling of the cervical region. Various degrees of firm, nonpitting edema in the region of the cervical lymph nodes and salivary glands as well as pale mucous membranes and dehydration were observed. Pure cultures of beta-hemolytic streptococci were obtained from the cervical lymph nodes of three rats that were necropsied. A rapid latex test system identified the isolates to have group G-specific antigen. These streptococcal isolates fermented trehalose and lactose but not sorbitol and inulin and did not hydrolize sodium hippurate or bile esculin. A Voges-Proskauer test was negative for all six isolates. Serologic tests to detect the presence of immunoglobulin G antibody to rat viral pathogens and Mycoplasma pulmonis were negative. Histopathologic changes included acute necrotizing inflammation of the cervical lymph nodes with multiple large colonies of coccoid bacteria at the perimeter of the necrotiz zone. To our knowledge, this is the first report of naturally occurring disease attributed to group G streptococci in rats.

A comparison of rodent caging systems based on microenvironmental parameters.

Four different mouse caging systems were evaluated for microenvironmental temperature, carbon dioxide, relative humidity (RH) and ammonia levels during a 7-day testing period. All caging systems evaluated had polycarbonate bases and consisted of either a molded polyester (MP) filter lid, one of two different polycarbonate filter lids, or no filter lid which served as a control. At 50% macroenvironmental RH (study I), all systems maintained an intracage temperature of 75.5 degrees F +/- 0.5 degrees. Both polycarbonate systems averaged greater than 2200 ppm of carbon dioxide more than the MP system and the controls. When compared with RH in the control cages, RH levels averaged over 20% and 5 to 8% RH greater in the polycarbonate filter lid systems and the MP system, respectively. There were no appreciable ammonia levels in either the MP or control systems. In the polycarbonate filter lid systems, ammonia levels were detectable on day 4 and were greater than 200 ppm by day 6. At 20% macroenvironmental RH (study II), there was a proportional 15 to 30% RH decrease from study I levels. Ammonia levels were undetectable in any system until day 7 and averaged only 17 ppm in one of the polycarbonate systems. Minimal differences were observed in studies III, IV and V when pine shavings were used instead of hardwood chips, a CD-1 stock instead of a DBA/2J strain, and different grades of filter inserts in the polycarbonate systems, respectively.