Neurokinin-1 receptor expression and antagonism by the NK-1R antagonist maropitant in canine melanoma cell lines and primary tumour tissues

We interrogated the neurokinin-1 receptor (NK-1R)/substance P (SP) pathway in canine melanoma tumour tissues and cell lines. NK-1R messenger RNA (mRNA) and protein expression were observed in the majority of tumour tissues. Immunohistochemical assessment of archived tissue sections revealed NK-1R immunoreactivity in 11 of 15 tumours, which may have diagnostic, prognostic and therapeutic utility. However, we were unable to identify a preclinical in vitro cell line or in vivo xenograft model that recapitulates NK-1R mRNA and protein expression documented in primary tumours. While maropitant inhibited proliferation and enhanced apoptosis in cell lines, in the absence of documented NK-1R expression, this may represent off-target effects. Furthermore, maropitant failed to suppress tumour growth in a canine mouse xenograft model derived from a cell line expressing mRNA but not protein. While NK-1R represents a novel target, in the absence of preclinical models, in-species clinical trials will be necessary to investigate the therapeutic potential for antagonists such as maropitant.

Adjuvant therapy with carboplatin and pamidronate for canine appendicular osteosarcoma

Amputation and chemotherapy are the mainstay of treatment for canine appendicular osteosarcoma (OSA). In vitro studies have demonstrated anti-tumour activity of pamidronate against canine OSA. The purpose of this study was to assess the safety of adding pamidronate to standard post-operative carboplatin chemotherapy in 17 dogs with appendicular OSA treated with limb amputation. Median disease-free interval (DFI) and median survival time (MST) were evaluated as secondary endpoints. Incidence of side effects and treatment outcomes were compared to 14 contemporary control patients treated with carboplatin alone. There were no identified side effects to the pamidronate treatment. The median DFI for the study group was 185 days compared to 172 days for the control group (P = 0.90). The MST of the study group was 311 days compared to 294 days for the control group (P = 0.89). Addition of pamidronate to carboplatin chemotherapy for the treatment of canine appendicular OSA is safe and does not impair efficacy of standard carboplatin treatment.

Phase I study to determine the maximal tolerated dose and dose-limiting toxicities of orally administered idarubicin in dogs with lymphoma

BACKGROUND

Idarubicin, a PO bioavailable anthracycline antibiotic-class chemotherapeutic, could have substantial convenience advantages over currently available similar class agents in use that require IV delivery.

OBJECTIVES

The primary objective of this study was to determine the maximally tolerated dose (MTD), dose-limiting toxicities (DLTs), and basic pharmacokinetic parameters of oral idarubicin exposure in dogs with lymphoma after a single oral dose. A secondary objective was to document preliminary antitumor efficacy in an expanded treatment cohort using the established MTD.

ANIMALS

Client-owned dogs with measurable lymphoma.

METHODS

Dogs (n = 31) were enrolled in a prospective open label phase I study of oral idarubicin. By means of a 3 + 3 cohort design, dose escalations were made with 3 dogs per dose level, and the MTD was established based on the number of patients experiencing a DLT. Plasma concentrations of idarubicin and idarubicinol were determined by postdose sampling. Assessment of antitumor efficacy focused on evaluation of accessible, measurable lymph nodes and skin lesions by modified RECIST guidelines.

RESULTS

The MTD in dogs > 15 kg body weight was 22 mg/m(2) . Adverse hematologic events (neutropenia and thrombocytopenia) were the predominant DLT and generally correlated with higher plasma concentrations of idarubicin and idarubicinol.

CONCLUSIONS AND CLINICAL IMPORTANCE

PO administered idarubicin was generally well-tolerated and had preliminary antitumor activity in dogs with lymphoma. Furthermore, the potential clinical advantage of a safe and efficacious oral anthracycline alternative supports further investigations of this agent in repeated-dose, randomized clinical trials.

Human granulocyte-macrophage colony-stimulating factor DNA cationic-lipid complexed autologous tumour cell vaccination in the treatment of canine B-cell multicentric lymphoma

This study describes the development of an human granulocyte-macrophage colony-stimulating factor DNA cationic-lipid complexed autologous tumour cell vaccine (hGM-CSF CLDC ATCV) and its implementation, following a chemotherapy treatment protocol, in a randomized, placebo-controlled, double-blinded clinical trial in pet dogs with naturally occurring lymphoma. We hypothesized that the use of this vaccine would result in an antitumour immune response leading to improved first remission duration and overall survival in dogs with B-cell lymphoma when compared with chemotherapy alone. Immune stimulation generated by hGM-CSF CLDC ATCV was assessed by means of surrogate in vivo analysis (delayed-type hypersensitivity [DTH]) as well as an ex vivo cellular assay (lymphocyte proliferation assay). The vaccine approach considered in the current report did not result in clinically improved outcomes. A small measure of immunomodulation was documented by DTH and several modifications to the approach are suggested. This report illustrates the feasibility of clinical trials with vaccine strategies using companion animals with non-Hodgkin's lymphoma.

Cisplatin and doxorubicin combination chemotherapy for the treatment of canine osteosarcoma: a pilot study

Sixteen dogs with histologically confirmed appendicular osteosarcoma were treated by amputation followed by cisplatin and doxorubicin chemotherapy. All dogs began chemotherapy within 24 hours of surgery. Cisplatin was administered at 50 mg/m2 intravenously (IV) concurrent with saline-induced diuresis. Doxorubicin was administered 24 hours later at 15 mg/m2 as a slow IV bolus. This protocol was given on a 21-day cycle for 4 cycles. No dose delays were required, but dose reduction of doxorubicin was required in 2 dogs because of neutropenia. Thoracic radiography was performed every 2 months after completion of therapy to monitor for metastatic disease. Two dogs were still alive and free from disease at the time of last contact (24 and 75 months, respectively). Postmortem examinations were performed on 13 of the 14 dogs that died. Eight of these dogs were euthanized because of metastatic osteosarcoma. Of the remaining 5 dogs, euthanasia was performed because of complications of idiopathic megaesophagus (n = 1), arthritis (n = 2), and hemangiosarcoma (n = 2). The median disease-free interval and survival times were 15.7 and 18 months, respectively. When compared to a historical group of 36 dogs with appendicular osteosarcoma treated with surgery and 4 doses of cisplatin. both disease-free interval and overall survival were significantly longer in the study population (P < .015 and P < .007, respectively).

Use of cis-bis-neodecanoato-trans-R,R-1,2-diaminocyclohexane platinum (II), a liposomal cisplatin analogue, in cats with oral squamous cell carcinoma

OBJECTIVE

To determine clinical response and toxic effects of cis-bis-neodecanoato-trans-R,R-1,2-diaminocyclohexane platinum (II) (L-NDDP) administered i.v. at escalating doses to cats with oral squamous cell carcinoma (SCC).

ANIMALS

18 cats with oral SCC.

PROCEDURE

Cats that failed to respond to conventional treatment or had nonresectable tumors were included. Data included a CBC, serum biochemical analyses, urinalysis, cytologic examination of a fine-needle aspirate of enlarged lymph nodes, and thoracic and oral radiographs for clinical staging. A starting dose (75 to 100 mg/m2 of L-NDDP) was administered i.v.. At 21-day intervals, subsequent doses increased by the rate of 5 or 10 mg/m2. Response was evaluated every 21 days by tumor measurement and thoracic radiography. Quality of life was assessed by owners, using a performance status questionnaire.

RESULTS

On average, cats received 2 treatments. Toxicoses included an intermittent, acute anaphylactoid-parasympathomimetic reaction, lethargy or sedation (< or = 24 hours), inappetence or signs of depression (< or = 72 hours), mild to moderate increase in hepatic enzyme activity, and melena. Pulmonary, renal, or hematopoietic abnormalities were not evident. Performance status surveys indicated normal behavior and grooming or decreased activity and self-care (19/20 assessments), ate well with or without assistance (15/20), and did not lose weight (15/20). Median survival time was 59.8 days (mean, 54.1 days).

CONCLUSIONS AND CLINICAL RELEVANCE

L-NDDP was ineffective for treatment of cats with oral SCC. None of the cats had a complete or partial remission. Acute toxicoses and poor therapeutic response limit therapeutic usefulness of L-NDDP in cats, unless dosage, frequency, and administration procedures can be improved.

Immunohistochemical detection of p53 tumor-suppressor protein is a poor indicator of prognosis for canine cutaneous mast cell tumors

Eighty-three canine cutaneous mast cell tumors were graded histologically and evaluated immunohistochemically for p53 tumor-suppressor protein expression. An avidin-biotin immunohistochemical protocol incorporated a rabbit polyclonal antibody (CM-1) directed against normal and mutant p53 protein. Positive staining was observed in 44.6% (37/83) of tumors and included 50% (12/24) of grade I (well differentiated) tumors, 46.9% (23/49) of grade II (intermediate differentiation) tumors, and 20% (2/10) of grade III (poorly differentiated) tumors. A statistically significantly higher proportion (P < 0.019) of tumors from the head and neck (83.3%, 10/12), stained positive for p53 than tumors from the thorax, back, abdomen, and axilla (39.4%, 13/33), legs (35.7%, 10/28), or prepuce, scrotal, or inguinal areas (44.4%, 4/9). No statistically significant difference between p53 labeling and histologic grade, breed, or tumor size was present. Survival data were available for 53/83 (63.9%) of dogs. Positive reactivity for p53 was observed in 47% (25/53) of tumors within this group, with 57.9% (11/19) of grade I, 43.3% (13/30) of grade II, and 25% (1/4) of grade III tumors labeled. Mean survival time for the 53 dogs was 12.1 months. The median survival time for dogs with grade III tumors or tumors >5 cm was statistically significantly shorter (P < 0.0001) than for dogs with grades I and II or smaller tumors. Although p53 protein abnormalities may play a role in tumor development or behavior in some canine cutaneous mast cell tumors, immunoreactivity was not associated with lack of tumor differentiation, tumor locations previously shown to demonstrate aggressive biological behavior, breed predisposition, or survival times.

Adjuvant therapy for melanoma in dogs: results of randomized clinical trials using surgery, liposome-encapsulated muramyl tripeptide, and granulocyte macrophage colony-stimulating factor

Spontaneous canine oral melanoma (COM) is a highly metastatic cancer, resistant to chemotherapy, and can serve as a model for cancer immunotherapy. Liposome-encapsulated muramyl tripeptide-phosphatidylethanolamine (L-MTP-PE) can activate the tumoricidal activity of the monocyte-macrophage system following i.v. injection. The objective of these studies was to evaluate the therapeutic effectiveness of L-MTP-PE administered alone and combined with recombinant canine granulocyte macrophage colony-stimulating factor (rcGM-CSF) in dogs undergoing surgery for oral melanoma. Ninety-eight dogs with histologically confirmed, clinically staged, oral melanoma were entered into two randomized, double-blind, surgical adjuvant trials. In trial 1, 50 dogs were stratified based on clinical stage and randomized to once a week L-MTP-PE or lipid equivalent (control). When all of the clinical stages were combined, no difference in disease-free survival or in survival time (ST) were detected. However, within stage I, dogs receiving L-MTP-PE had a significant increase in ST compared with control, with 80% of the dogs treated with L-MTP-PE still alive at >2 years. Within each stage II and stage III, there was no difference detected between the treatment groups. In trial 2, 48 dogs were stratified on the basis of clinical stage and extent of surgery (simple resection or radical excision), treated with L-MTP-PE two times a week, and randomized to rcGM-CSF or saline (placebo) given s.c. daily for 9 weeks. Within each stage and when all of the stages were combined, there was no difference between the treatment groups. In both studies, stage I COM is associated with a better prognosis. No effect on survival was observed with regard to tumor location in the oral cavity, sex, type/extent of surgery, or age. In a subset of dogs tested, pulmonary alveolar macrophage cytotoxicity was enhanced with combined rcGM-CSF and L-MTP-PE but not in dogs treated with L-MTP-PE alone. The present study indicates that after surgery, L-MTP-PE administered alone or combined with rcGM-CSF showed no significant antitumor activity in treating advanced stage COM. In early stage COM, L-MTP-PE was shown to result in a prolongation of ST. Furthermore, this study provides additional rationale for the use of the dog model for human malignant melanoma.

Inhalation chemotherapy for macroscopic primary or metastatic lung tumors: proof of principle using dogs with spontaneously occurring tumors as a model

This study represents part of an effort to determine the safety and efficacy of inhaled antineoplastic drugs, using pet dogs with spontaneously arising primary and metastatic lung cancers (including sarcoma, carcinoma, and malignant melanoma) as a model. Dogs received new formulations of either paclitaxel (PTX) or doxorubicin (DOX) by the inhalation route every 2 weeks using a specially designed aerosol device. Response was assessed radiographically using the indices of tumor nodule number and volume measurement of discrete pulmonary nodules. Dogs experiencing progressive disease after two consecutive treatments were crossed over to receive the alternate compound. In 24 dogs, 6 (25%) responses were noted including 5 partial responses (PR) and 1 complete response. These include 4 (22.2%) of 18 responses to DOX and 2 (13.3%) of 15 responses to PTX. Responses were noted with osteosarcoma (including three dogs with metastatic osteosarcoma that had failed prior systemic chemotherapy), liposarcoma, hemangiosarcoma, and undifferentiated sarcoma. One dog with mammary carcinoma experienced a 47% reduction in volume after PTX inhalation, just shy of PR criteria. One dog with liposarcoma is experiencing a long-term (>12 months) stabilization of disease on PTX. To date, no systemic toxicities have been observed with either PTX or DOX inhalations. Local (pulmonary) toxicity was not observed with PTX; however, changes consistent with pneumonitis/fibrosis were observed in some dogs receiving DOX. Only one of these dogs showed clinical signs, which were responsive to steroid and antitussive therapy. These data represent "proof of principle" for the avoidance of systemic toxicity while delivering efficacious local drug levels by the inhalation route.

In vitro and in vivo enhancement of canine pulmonary alveolar macrophage cytotoxic activity against canine osteosarcoma cells

The combination of chemotherapy with immunotherapy may offer an advantage over either therapy alone and provide a greater potential for total tumor eradication. Monocyte/macrophage-mediated tumor cell killing is a major mechanism of the host's defense against primary and/or metastatic neoplasia. We evaluated the tumoricidal activity against canine osteosarcoma cells of canine pulmonary alveolar macrophages (PAM) exposed in vitro to two recombinant canine (rc) cytokines (rcTNF alpha and rcIFN gamma). We also evaluated the in vivo tumoricidal activity of PAM from dogs treated with the macrophage activator, liposome-encapsulated muramyl tripeptide-phosphatidyl-ethanolamine (L-MTP-PE) alone or in combination with doxorubicin (DOX). This study demonstrated that rcTNF alpha and rcIFN gamma significantly enhance in vitro canine PAM cytotoxicity against canine osteosarcoma cells, and that PAM from dogs treated with DOX + L-MTP-PE have enhanced cytotoxic activity against osteosarcoma cells when compared to dogs treated with DOX or L-MTP-PE alone. These findings support the rationale for combining a chemotherapy agent with an immunotherapy agent for the treatment of metastatic disease, and suggest a role for TNF alpha and IFN gamma as agents for stimulating the antitumor activity of macrophages.

The effect of dehydroepiandrosterone combined with a low-fat diet in spontaneously obese dogs: a clinical trial

Dehydroepiandrosterone (DHEA) has been shown to have antiobesity activity in rodents and spontaneously obese dogs. This study evaluated the effect of DHEA or placebo combined with a low-fat/high-fiber diet in spontaneously obese dogs in a clinical trial. Spontaneously obese, euthyroid dogs, referred to the University of Wisconsin School of Veterinary Medicine for treatment of their obesity, were evaluated for percent overweight, rate of weight loss, serum cholesterol, plasma lipoprotein and serum biochemistry profiles, complete blood count, and endocrine profiles (T4, T3, cortisol, insulin, and DHEA-sulfate). DHEA-treated dogs had a significantly increased rate of actual and percent excess weight loss compared with placebo-treated dogs. Serum cholesterol decreased in both treatment groups; however, DHEA-treated dogs had a significantly greater reduction than placebo-treated dogs. DHEA-treated dogs had a significant 32% reduction in total plasma cholesterol, which was due to a 27% reduction in the lipoprotein fraction containing the high-density lipoprotein (HDL) and a 50% reduction in the lipoprotein fraction containing the low-density lipoprotein (LDL). Placebo-treated dogs did not have a significant reduction in total plasma cholesterol or in the fraction containing LDL; however, they did have a significant 11% reduction in the fraction containing HDL. Significant decreases in serum T4 and T3 observed in dogs receiving DHEA were not noted in dogs receiving placebo. DHEA in combination with caloric restriction results in a faster rate of weight loss than does caloric restriction alone. In addition, DHEA has hypocholesterolemic activity, particularly affecting the lipoprotein fraction containing the LDL cholesterol.

Immunohistochemical detection of p53 tumor suppressor gene protein in canine epithelial colorectal tumors

Eighty canine epithelial colorectal tumors obtained by excisional biopsy were evaluated immunohistochemically for p53 tumor suppressor gene protein. Dogs in the study average 6.9 years of age (range, 1-12.5 years). A standard avidin-biotin immunohistochemical protocol incorporated a polyclonal antibody of rabbit origin (CM-1) as the primary antibody. Positive staining was observed within all subcategories of lesions, including hyperplastic polyps 1/2 (50%), adenomas 14/29 (48%), carcinomas in situ 9/22 (41%), adenocarcinomas 3/4 (75%), and invasive carcinomas 8/23 (35%). A total of 35/80 (44%) positive tumors wee identified. Fifteen of 31 (48%) benign tumors labeled for p53 protein compared to 20/49 (41%) malignant tumors. Survival data was available for 57/80 (71%) dogs. The average age of dogs within the group with survival data was 4.4 years. Males predominated 34/57 (60%). Mean survival time was 20.6 months. There was no significant difference in survival time between dogs grouped according to p53 immunoreactivity, cellular stain location, or tumor site. A statistically significant increase in survival time was observed between dogs with clean surgical margins and those without (P < 0.018) and for dogs with adenomas or carcinomas in situ over dogs with invasive carcinomas (P < 0.02). In this study, the overall greater positive staining frequency of benign lesions compared to malignant lesions is contrary to data derived from similar immunohistochemical analyses of human tumors and is incongruous with the theorized late-stage participation of the p53 protein in the development of human colorectal cancers. The results of this study suggest that if the p53 tumor suppressor gene protein is involved in the progression of canine colorectal tumors, it may play a relatively early role, possibly analogous to the early appearance of p53 overexpression in precancerous lesions of human ulcerative colitis. Immunohistochemical detection of p53 was not useful prognostically.

Amputation and carboplatin for treatment of dogs with osteosarcoma: 48 cases (1991 to 1993)

Forty-eight dogs with histologically confirmed appendicular osteosarcoma (OSA) entered a prospective clinical trial evaluating treatment with amputation and up to 4 doses of carboplatin given every 21 days. The median disease-free interval (DFI) was 257 days, with 31.2% of the dogs disease-free at 1 year. The median survival time was 321 days, with 35.4% of the dogs alive at 1 year. Dogs with proximal humeral OSA had shorter DFI (P = .016) and survival (P = .037) times than dogs with OSA at other locations. Dogs with lower body weights ( < 40 kg) had longer DFI (P = .0056) and survival (P = .007) times than larger dogs. Survival times for dogs that received carboplatin were statistically longer than those previously reported for amputation alone (P < .001). DFI and survival times are similar to those previously reported for 2 to 4 doses of cisplatin. Carboplatin appears to be a well-tolerated chemotherapeutic drug that can be given safely every 21 days at a dose of 300 mg/m2. Neutropenia was the dose-limiting toxicity in this study.

Canine osteosarcoma: amputation and chemoimmunotherapy

Canine osteosarcoma is a highly metastatic cancer commonly seen in large breed dogs. At the time of diagnosis, approximately 90% to 95% of the dogs have established micrometastases. Dogs undergoing amputation alone have a median survival time of 3 to 4 months. Amputation followed by cisplatin chemotherapy increases median survival times to 9 to 11 months. When dogs are treated with amputation and cisplatin, followed by immunotherapy (with liposome-encapsulated muramyl tripeptide phosphatidylethanolamine), median survival times increase to 14.4 months, the longest reported median survival time for dogs with osteosarcoma treated by amputation and any form of adjuvant therapy.

Adjuvant therapy for osteosarcoma in dogs: results of randomized clinical trials using combined liposome-encapsulated muramyl tripeptide and cisplatin

Two randomized, double-blind clinical trials in dogs with spontaneous appendicular osteosarcoma treated with combination chemoimmunotherapy are reported. In both trials, dogs without overt metastasis underwent complete amputation of the affected limb. In trial 1, 40 dogs were treated with cisplatin chemotherapy [(CDDP), 70 mg/m2 i.v. every 28 days x 4]. Following CDDP, dogs without evidence of overt metastasis (n = 25) were randomized to receive liposome-encapsulated muramyl tripeptide phosphatidylethanolamine ](L-MTP-PE), 2 mg/m2 i.v.) or placebo liposomes (lipid equivalent) twice weekly for 8 weeks. Of 14 dogs in the placebo group, 13 (93%) died of metastasis; the median survival time was 9.8 months. Of 11 dogs in the L-MTP-PE group, 8 (73%) developed metastasis; the median survival time was 14.4 months, which was significantly longer than that of the placebo group (P < 0.01). In trial 2, 64 dogs received CDDP (70 mg/m2 i.v. every 21 days x 4) and were randomized to concurrently receive L-MTP-PE (2 mg/m2 i.v.) twice or once weekly, or placebo liposomes once weekly for 8 weeks. Median survival times were 10.3, 10.5, and 7.6 months, respectively. There were no significant differences among the three treatment groups in trial 2. Survival times for dogs receiving L-MTP-PE in trial 1 were significantly longer than those for dogs in trial 2 that received four doses of CDDP concurrently with twice weekly L-MTP-PE (P < 0. 04). The results of the first trial confirm our previous observation that L-MTP-PE has antimetastatic activity in dogs with osteosarcoma when given following amputation. The results of the second trial demonstrate that there is no survival advantage of administering L-MTP-PE concurrently with CDDP.

Liposome-encapsulated muramyl tripeptide phosphatidylethanolamine adjuvant immunotherapy for splenic hemangiosarcoma in the dog: a randomized multi-institutional clinical trial

Canine splenic hemangiosarcoma (HSA) is a spontaneous tumor with high metastatic potential. Despite surgical excision, most dogs die within 2 months of diagnosis as a result of widespread visceral metastasis. This study was designed to determine the efficacy of liposome-encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE) when used in combination with splenectomy and systemic chemotherapy for the treatment of HSA in the dog. Thirty-two dogs with HSA and without gross evidence of metastases were treated with splenectomy, stratified by clinical stage, and randomized to receive doxorubicin/cyclophosphamide chemotherapy and either L-MTP-PE immunotherapy or lipid equivalent (placebo liposomes). Dogs were subsequently followed to determine disease-free survival and overall survival times. The effects of L-MTP-PE on serum tumor necrosis factor-alpha and interleukin 6 activity were assessed on a small subset of dogs. Dogs receiving L-MTP-PE had significantly prolonged disease-free survival (P = 0.037) and overall survival (P = 0.029) compared with dogs receiving placebo. Dogs with clinical stage I disease had significantly prolonged disease-free survival (P = 0. 026) and overall survival (P = 0.017) compared with dogs with clinical stage II disease. Dogs receiving L-MTP-PE had significantly greater serum tumor necrosis factor-alpha (P < 0.001) and interleukin 6 (P = 0.007) activities compared with placebo-treated dogs. L-MTP-PE has significant antimetastatic activity in highly malignant, spontaneously occurring, splenic HSA in the dog. Canine HSA may have potential as a large animal model for additional investigation of antimetastatic chemoimmunotherapy.

The effect of high fat diet and dehydroepiandrosterone (DHEA) administration in the rhesus monkey

Dehydroepiandrosterone (DHEA) lowers serum cholesterol, particularly the low density lipoprotein (LDL) fraction, in rhesus monkeys on a commercial diet (12% calories from fat, 0.0083% cholesterol). We fed rhesus monkeys a diet of 30% calories from fat and 0.1% cholesterol for 12 weeks, then commercial chow for 7 weeks. Six monkeys each received DHEA or placebo, orally for 17 weeks. Food intake increased the first 6 weeks, but decreased thereafter. Monkeys had a 22% mean weight gain while on high fat diet. DHEA monkeys had higher T4 levels than placebo monkeys at weeks 8 and 16. After 12 weeks on high fat diet, all monkeys had elevated serum cholesterol concentrations, an increase in amount and percentage of intermediate density lipoprotein and LDL cholesterol, and an increase in amount, but a decrease in percentage of high density lipoprotein cholesterol. There were no significant differences in serum cholesterol or plasma lipoprotein concentrations between DHEA and placebo monkeys while on high fat diet (a trend toward lower levels was noted in the DHEA group). On commercial chow, plasma lipoprotein concentrations decreased for all monkeys, and DHEA monkeys had significantly lower total and LDL cholesterol than placebo monkeys. We conclude that a high fat diet (30% fat) masks any cholesterol-lowering effects of DHEA.

In vitro and in vivo production of interleukin-6 induced by muramyl peptides and lipopolysaccharide in normal dogs

Interleukin-6 (IL-6) is a multifactorial cytokine produced by many cells including monocytes and macrophages in the immune-stimulated host. We measured IL-6 activity induced by muramyl dipeptide (MDP) and lipopolysaccharide (LPS) in vitro and by liposome-encapsulated muramyl tripeptide-phosphatidylethanolamine (L-MTP-PE) in vivo in normal dogs. Adherent mononuclear cells were cultured with MDP, LPS, or MDP plus LPS for various time periods. After incubation, culture supernatants were collected and assayed for IL-6 activity. Sera from dogs following L-MTP-PE administration were also evaluated for IL-6 activity. IL-6 activity both in supernatants and sera was measured using a 7TD1 bioassay. Significantly elevated IL-6 activity could be measured as early as 2 hours after mononuclear cells were exposed to MDP, LPS, or MDP plus LPS. IL-6 activity induced by LPS was greater than that induced by MDP, and the combination of MDP and LPS induced the greatest increase in IL-6 activity. Serum IL-6 activity was elevated within 3 to 4 hours post L-MTP-PE administration and subsequently declined to pretreatment level at 24 hours post injection. Neutralization of supernatant and serum IL-6 activity was not achieved with goat or rabbit anti-recombinant human IL-6 polyclonal antibody. This study demonstrates that MDP and LPS, alone and in combination, can induce enhanced IL-6 activity of canine adherent mononuclear cells in vitro, and that intravenous injection of L-MTP-PE is capable of eliciting increased IL-6 activity in vivo in normal dogs. These findings suggest that IL-6 may play an important role in the biologic response observed in canine cancer patients treated with L-MTP-PE.

Liposome-encapsulated muramyl tripeptide phosphatidylethanolamine for the treatment of feline mammary adenocarcinoma--a multicenter randomized double-blind study

Forty cats with previously untreated, histologically confirmed mammary gland adenocarcinoma received a radical mastectomy of the affected mammary chain(s). All cats were stratified according to clinical stage and randomized to receive either weekly intravenous liposome-encapsulated muramyl tripeptide phosphatidylethanolamine or placebo (lipid-equivalent) for eight consecutive weeks in this double-blind study. Thirty-six of the 40 cats were available for follow-up. No significant differences in either disease-free interval or survival were found as a result of treatment. Cats with clinical stage II disease had a statistically significantly longer disease-free interval (p < 0.02), and overall survival (p < 0.005) when compared with clinical stage III cats.

Prognostic factors for treatment of malignant lymphoma in dogs

Pretreatment characteristics of 138 dogs with malignant lymphoma were analyzed to determine prognostic factors associated with outcome (ie, complete response rate, time to relapse after complete response, survival time). Dogs were all treated for 10 weeks, using a standard induction chemotherapy protocol, and were then given asparaginase weekly. Once the disease became progressive, second-line chemotherapy was instituted. Age, sex, weight, clinical stage, performance grade, immunophenotype, and malignancy grade assigned according to the National Cancer Institute's Working Formulation were not associated with complete response rate. However, malignancy grade assigned according to the Kiel classification was found to be associated with complete response rate; dogs with high-grade malignancies had a significantly higher complete response rate than did dogs with low-grade malignancies. By means of multivariate analysis, clinical stage and immunophenotype were found to be prognostic factors for time to relapse (among dogs that had had a complete response) and survival time. In addition, malignancy grade assigned according to the Kiel classification was found to be a prognostic factor for time to relapse; whereas, malignancy grade assigned according to the Working Formulation was determined to be a prognostic factor for survival time.

Hypocholesterolemic effect of exogenous dehydroepiandrosterone administration in the rhesus monkey

The effect(s) of exogenous dehydroepiandrosterone (DHEA) was studied in healthy non-obese rhesus monkeys. Six monkeys were given 60 mg/kg/day DHEA for 4 weeks. The dose was then increased to 75 mg/kg/day for an additional 4 weeks. Another six monkeys were given placebo, daily for 8 weeks. Body weight, activity level, average daily food intake, and plasma T4, insulin, total androgen and cortisol concentrations remained unchanged for all 12 monkeys throughout the 8 weeks. Both groups had a significant (p < 0.05) decrease in total plasma cholesterol, however the DHEA treated monkeys were significantly lower than the placebo monkeys. The change in cholesterol in the DHEA treated group primarily affected the fraction containing the low density lipoprotein cholesterol which remained overall unchanged for the placebo monkeys. Both groups had a decrease in high density lipoprotein cholesterol, however there was no difference between the treatment groups. We conclude that in the rhesus monkey, exogenous administration of DHEA acutely reduces cholesterol concentration, particularly the lipoprotein fraction containing low density lipoprotein, without changing food intake, activity level, or body weight.

Current studies of liposome muramyl tripeptide (CGP 19835A lipid) therapy for metastasis in spontaneous tumors: a progress review

Targeted delivery of macrophage activating agents is an attractive approach to treat micrometastatic disease. Liposome-encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE) is a potent activator of monocytes/macrophages in humans, mice, and dogs. We have conducted clinical trials in dogs with malignant and highly metastatic spontaneous tumors. Presented are results of our trials evaluating L-MTP-PE in combination with surgery and chemotherapy in dogs with spontaneous osteosarcoma and hemangiosarcoma, particularly relevant malignancies having having many similarities to human cancer. Osteosarcoma dogs received chemotherapy following surgery (cisplatin q 28 days x 4). At completion of chemotherapy, dogs were randomized to receive L-MTP-PE or placebo. The L-MTP-PE group had a significantly longer median survival time compared to the placebo group (p < 0.021). Dogs with splenic hemangiosarcoma received combination chemotherapy following surgery (doxorubicin and cyclophosphamide q 21 days x 4). At the first chemotherapy, dogs were randomized to receive L-MTP-PE or placebo. The L-MTP-PE group had a significantly longer median survival time compared to the placebo group (p < 0.03). These studies show that L-MTP-PE is an effective agent for treatment of metastasis and can be safely administered in combination with chemotherapy.

Induction of serum tumor necrosis factor-alpha and interleukin-6 activity by liposome-encapsulated muramyl tripeptide-phosphatidylethanolamine (L-MTP-PE) in normal cats

Tumor necrosis factor-alpha (TNF alpha) and interleukin-6 (IL-6) are products of activated monocytes/macrophages with anti-tumor activity. Liposome-encapsulated muramyl tripeptide-phosphatidylethanolamine (L-MTP-PE) is a potent monocyte/macrophage activator. Sera from cats after intravenous L-MTP-PE administration showed TNF alpha activity using a WEHI-164 cell cytotoxicity assay and IL-6 activity using an IL-6 dependent mouse 7TD1 hybridoma cell proliferation assay. Serum TNF alpha activity peaked at 2 hours after L-MTP-PE administration. Significant differences from lipid-equivalent controls were observed at 2 and 3 hours (P < 0.05). Neutralization of serum TNF alpha activity was accomplished with serial dilutions of rhTNF alpha monoclonal antibody. Serum IL-6 activity peaked at 3 hours after L-MTP-PE administration. Significant differences from lipid-equivalent controls were observed at 2, 3, and 4 hours (P < 0.05). Neutralization of serum IL-6 activity was not achieved with goat anti-rhIL-6 polyclonal antibody. Intravenous L-MTP-PE, but not lipid-equivalent, induces serum TNF alpha and IL-6 activity in normal cats.

Effect of liposome-muramyl tripeptide combined with recombinant canine granulocyte colony-stimulating factor on canine monocyte activity

Liposome-muramyl tripeptide-phosphatidylethanolamine (L-MTP-PE) has been shown to activate monocytes in vivo to become tumoricidal resulting in reduction in metastasis as well as prolongation of survival time in murine and canine tumor models. Granulocyte colony-stimulating factor (G-CSF) is a cytokine which will stimulate the proliferation of granulocytes as well as monocytes. Recombinant canine G-CSF (rcG-CSF) was administered to normal dogs as a method of increasing the monocyte population prior to in vivo monocyte activation using L-MTP-PE. rcG-CSF administration resulted in a 3.5-fold increase in absolute monocyte counts and when combined with L-MTP-PE, resulted in an enhanced level of serum tumor necrosis factor-alpha activity compared to dogs treated with L-MTP-PE alone. G-CSF alone did not affect monocyte cytostatic activity, however, dogs receiving G-CSF had a significant increase in monocyte cytostatic activity following L-MTP-PE. The combined use of CSFs and effector cell activators deserves further evaluation in clinical trials.

In vitro and in vivo canine mononuclear cell production of tumor necrosis factor induced by muramyl peptides and lipopolysaccharide

Tumor necrosis factor (TNF) is a potent mediator of tumor cell killing by activated monocytes and macrophages. We measured TNF activity induced by muramyl peptides and lipopolysaccharide (LPS) in normal dogs. Canine adherent mononuclear cells were isolated and cultured in either medium alone or medium containing muramyl dipeptide (MDP) or MDP plus LPS. After 18 h, culture supernatants were collected and assayed for TNF activity. Sera from dogs injected with liposome-encapsulated muramyl tripeptide-phosphatidylethanolamine (L-MTP-PE) were also evaluated for TNF activity. TNF activity both in supernatants and in sera was detected in a 18 h WEHI-164 cell cytotoxicity assay and was confirmed by a monoclonal antibody directed against recombinant human TNF-alpha. Results showed a significant increase in TNF activity from mononuclear cells exposed to MDP or MDP plus LPS of 20% and 88%, respectively; P < 0.0005. Serum TNF activity rapidly increased within 2-3 h post L-MTP-PE injection and subsequently declined to pretreatment level at 4 h post administration. This study demonstrates that MDP +/- LPS can stimulate canine adherent mononuclear cells to release TNF and intravenous injection of L-MTP-PE is capable of rendering the in vivo release of TNF in normal dogs.

In vitro and in vivo effect of doxorubicin combined with liposome-encapsulated muramyl tripeptide on canine monocyte activation

Chemotherapeutic agents have been shown to enhance the antitumor activity of biological response modifiers and cytokines in rodents and humans. The purpose of this study was 2-fold: (a) to determine whether doxorubicin (DOX) would enhance or interfere with the effect of muramyl dipeptide and lipopolysaccharide on canine monocyte activation as measured by an in vitro WEHI-164 cell cytotoxicity assay; and (b) to evaluate the in vivo effect of DOX alone and combined with liposome-encapsulated muramyl tripeptide-phosphatidylethanolamine (L-MTP-PE) on monocyte activation and serum tumor necrosis factor activity. The in vitro results showed that increasing concentrations of DOX for either 1 or 24 h incubation did not directly enhance or inhibit spontaneous or activated monocyte supernatant-mediated cytotoxicity. The in vivo study showed that monocyte supernatant-mediated cytotoxicity was increased on day 3 and significantly elevated on day 7 (P = 0.016) post-DOX (30 mg/m2, single injection) administration. When DOX was given in combination with L-MTP-PE (2 mg/m2, twice weekly for 3 weeks), monocyte-mediated cytotoxicity was enhanced on days 3 through 10 with a significant increase on day 10 (P < 0.001). In vivo monocyte supernatant-mediated cytotoxicity was significantly elevated in dogs receiving L-MTP-PE alone at 2 h after day 0, 7, and 14 treatment, and this response was further enhanced by DOX. Serum tumor necrosis factor activity at 2 h post-L-MTP-PE was enhanced and sustained for a longer period of time in dogs that also received DOX. We conclude that DOX administered with L-MTP-PE will enhance canine monocyte activation induced by DOX or L-MTP-PE alone, and suggest that DOX may be combined with L-MTP-PE early in the treatment of cancer patients.

Muramyl peptides augment the in vitro and in vivo cytostatic activity of canine plastic-adherent mononuclear cells against canine osteosarcoma cells

A tumor cytostasis assay was developed that measured the effect of the immunomodulator muramyl dipeptide (MDP) on the in vitro cytostatic activity of canine plastic-adherent mononuclear cells. Mononuclear cells were isolated from the peripheral blood of healthy Beagle donors and allowed to adhere to a 96-well microtiter plate. The adherent cell population was characterized by cell morphology, non-specific esterase staining, and flow microfluorometry to be approximately 42% monocytes, 49% lymphocytes, and 8% eosinophils. Canine plastic-adherent mononuclear cells spontaneously caused cytostasis of D-17 canine osteosarcoma target cell proliferation. The spontaneous cytostatic activity of adherent mononuclear cells was significantly augmented by exposure to MDP or to lipopolysaccharide (LPS), with maximal cytostatic activity being observed after combined exposure to MDP and LPS. Mononuclear cell cytostasis toward D-17 canine osteosarcoma and A375 human melanoma cells was enhanced (P < 0.05) when normal dogs were administered liposome-encapsulated muramyl tripeptide phosphatidylethanolamine, a lipophilic derivative of MDP, by intravenous injection.

Risk factors, clinical signs, and survival in cats with a clinical diagnosis of idiopathic hypertrophic cardiomyopathy: 74 cases (1985-1989)

Population characteristics, risk factors, and survival characteristics were evaluated in 74 cats with hypertrophic cardiomyopathy (HC) seen at North Carolina State University veterinary teaching hospital from 1985 to 1989, and compared with 82 clinically normal cats. The mean (+/- SD) age of cats with HC was 6.5 (4.0) years. Neutered males were at significantly greater risk (odds ratio 3.1) than neutered females. Breed, body weight, or coat color were not determined to be risk factors for HC. Tricolor cats were significantly underrepresented, probably reflecting the male predisposition for HC and not a true risk reduction associated with coat color. Forty-one cats were without clinical signs of heart disease (murmur and/or gallop sound only), 24 were in congestive heart failure, and 9 had systemic arterial embolism, 3 of which had concomitant congestive heart failure. The median survival time for 61 cats with HC, for which survival information could be obtained and that were not euthanatized on day 1, was 732 days. Survival was not affected by age at diagnosis, breed, body weight, or sex. However, clinical signs were important in determining prognosis; cats with heart rates greater than 200 beats/min survived significantly longer (median survival greater than 1,830 days) than those with heart rates greater than or equal to 200 beats/min (median survival = 152 days). Cats without clinical signs (median survival greater than 1,830 days) survived longer than those with clinical signs, and cats in heart failure survived a median of 92 days, compared with 61 days for those with systemic arterial embolism. Analysis of survival revealed no significant difference between the 2 groups of cats with clinical signs; however, all cats with embolism and only 60% of cats with heart failure were dead 6 months after diagnosis.

Evaluation of L-asparaginase: polyethylene glycol conjugate versus native L-asparaginase combined with chemotherapy. A randomized double-blind study in canine lymphoma

L-asparaginase is an enzyme that inhibits protein synthesis by the depletion of sources of L-asparagine, which is necessary for transformed lymphoid cells to proliferate. L-asparaginase is used in the treatment of childhood acute lymphoblastic leukemia. A problem with L-asparaginase therapy is the immunogenicity of the enzyme and the development of anaphylactic reactions. Canine lymphoma is a predominantly B-cell tumor with widespread disease; without treatment, dogs with lymphoma usually survive 1-2 months. Canine lymphoma will respond to L-asparaginase therapy. A randomized double-blind study evaluated a polyethylene glycol (PEG) conjugate L-asparaginase combined with chemotherapy (vincristine, cyclophosphamide, doxorubicin, and prednisone). Thirty-five dogs were randomized to the PEG L-asparaginase group, and 34 dogs were randomized to the native L-asparaginase group. Thirty dogs (85.7%) achieved a complete remission (CR) with a median time to relapse of 217 days, and 32 (94.1%) dogs in the native L-asparaginase group achieved a CR with a median time to relapse of 214 days (P greater than 0.05). The asparaginase was well tolerated in both groups. Two dogs in the native L-asparaginase group had severe allergic reactions, and one dog in the PEG asparaginase group had a generalized urticarial reaction after repeated injections. This study indicates that PEG L-asparaginase has equal therapeutic efficacy to native L-asparaginase.

Effect of colony-stimulating factors on number and function of circulating monocytes in normal dogs

Recombinant human granulocyte-macrophage colony-stimulating factor (rhuGM-CSF) and recombinant canine granulocyte colony-stimulating factor (rcG-CSF) were administered to normal dogs, and effect on monocyte number and function was evaluated. rhuGM-CSF, administered for 14 days, induced a 2.5-fold increase in monocyte counts on day 3. Leukocytes increased two-fold after 1 day. Counts peaked on day 11, then declined, approaching pretreatment counts by day 15. On day 7, in vivo monocyte cytostasis activity was significantly enhanced, and declined on day 14. rcG-CSF induced a 4.5-fold increase in monocyte counts on day 3. Leukocyte counts increased three-fold after 1 day. Increased counts were maintained for 69 days, at which time treatment was discontinued. There was no effect of rcG-CSF on in vivo monocyte cytostasis activity on days 7 and 14.

Evaluation of two applanation tonometers in cats

Comparisons of the MacKay-Marg and Tono-Pen applanation tonometers in open and closed in vitro systems were made for the eyes of cats. Both instruments significantly underestimated intraocular pressure (IOP) vs direct manometry (P less than 0.001), but in readily predictable manner, with high coefficients of determination (r2 = 0.99). For tonometer 1 (MacKay-Marg), calculated actual IOP = 1.36 x (MacKay-Marg measurement) - 1.67 mm of Hg; and for tonometer 2 (Tono-Pen), calculated actual IOP = 1.37 x (Tono-Pen measurement) + 0.8 mm of HG, using measurements from 11 enucleated eyes. In vivo comparisons were initially made in 81 clinically normal eyes (n = 41 cats) by applying the Tono-Pen first followed by the MacKay-Marg. Compared with the MacKay-Marg, the Tono-Pen significantly (P less than 0.001) underestimated IOP in these cats. When the order of tonometer applanation was subsequently reversed in 73 clinically normal eyes (n = 37 cats) the Tono-Pen again significantly (P less than 0.001) underestimated IOP, compared with the MacKay-Marg. Alterations in tonometer order did not result in significant differences in measured IOP for the MacKay-Marg when compared with itself, but Tono-Pen measurements were significantly (P less than 0.05) less when its use followed, rather than preceded, that of the MacKay-Marg. Mean (+/- SD) IOP in clinically normal cats when each tonometer was used first was 22.6 +/- 4.0 mm of Hg (range, 14 to 32 mm of Hg) for the MacKay-Marg and 19.7 +/- 5.6 mm of Hg (9 to 31 mm of Hg) for the Tono-Pen.(ABSTRACT TRUNCATED AT 250 WORDS)

Obesity in the dog: role of the adrenal steroid dehydroepiandrosterone (DHEA)

It is estimated that 25-50% of pet dogs are overweight. In rodents and humans the adrenal steroid dehydroepiandrosterone (DHEA) has been associated with loss of body weight and reduction in total body fat content. We have shown that administration of DHEA results in weight loss in spontaneously obese dogs. DHEA also lowered serum cholesterol, in particular, the low density lipoprotein component of the plasma cholesterol. We hypothesize that treatment of obese dogs with DHEA in combination with a low energy, high fiber diet will result in greater weight loss when compared with dogs on the same diet, without DHEA. In the current study, spontaneously obese dogs were fed a uniform low energy, high fiber diet and then randomized to receive DHEA or placebo. Preliminary results show that the mean total body weight lost for dogs receiving DHEA was 3.59 kg compared with 2.38 kg for dogs receiving placebo (P greater than 0.05). The percent excess body weight (above ideal body weight) lost for the DHEA group was 65.7 versus 31.4 for the placebo group (P less than 0.02). The percent excess body weight lost per month on the study for the DHEA group was 15 versus 8.2 for the placebo group (P = 0.069). Although these results are preliminary, they indicate that DHEA combined with a low energy, high fiber diet enhances the loss of excess body weight compared with diet modification alone.

Reduction in body weight and cholesterol in spontaneously obese dogs by dehydroepiandrosterone

We studied the effect(s) of exogenous dehydroepiandrosterone (DHEA) in spontaneously obese dogs. Nineteen euthyroid obese and six non-obese normal dogs were evaluated. Dogs received DHEA for three months at an escalating dose of 30-75 mg/kg p.o. daily. We found a 3 percent reduction in total body weight/month in 68 percent of the obese dogs, without reduction in food intake. The normal dogs did not lose weight or reduce food intake. Serum cholesterol in obese dogs went from 226 to 173 mg/dl post-treatment and in normal dogs from 128 to 89 mg/dl. Analysis of lipoproteins in four normal dogs revealed that the marked reduction in cholesterol most significantly affected the LDL-HDL1 fraction.

Therapy for osteosarcoma in dogs with intravenous injection of liposome-encapsulated muramyl tripeptide

Canine osteosarcoma is a spontaneous malignancy in dogs, characterized by micrometastasis to pulmonary and extrapulmonary tissues at the time of diagnosis. Standard treatment involves amputation of the affected leg, but median survival time is 3-4 months with death due to metastasis. A randomized double-blind trial was conducted to evaluate liposome-encapsulated muramyl tripeptide-phosphatidylethanolamine (liposome/MTP-PE) as a treatment for metastasis in dogs undergoing amputation for osteosarcoma. Fourteen dogs were treated with liposome/MTP-PE, and 13 were treated with empty liposomes. Median survival time was 222 days for dogs treated with liposome/MTP-PE, compared to 77 days for dogs treated with empty liposomes (P less than .002). In the liposome/MTP-PE-treated group there were still four dogs alive and free of metastasis at greater than 1 year post surgery. Treatment was well tolerated; no significant toxic effects were noted except for mild elevations in body temperature (1-2 degrees C) for 2-6 hours post injection.

Radiotherapy of malignant nasal tumors in 67 dogs

The nasal cavity of 67 dogs with malignant nasal neoplasia was treated with radiation. Preirradiation surgical cytoreduction of the tumor was done in 41 dogs. Fifty dogs were irradiated by use of 10 fractions over 22 days, and 17 dogs were given a similar total dose in 5 fractions over 35 days. The range of survival times (0.5 to 42 months), median survival time (8.5 months), and 1- and 2-year survival rates (38% and 30%, respectively) were better than those expected for other methods of treatment. Serious complications were few (4%). Survival times for dogs were determined on the basis of histologic tumor type and on the basis of megavoltage (cobalt or linear accelerator) vs softer deep radiation (cesium or orthovoltage) treatment, with or without cytoreductive surgery. Survival times of 10 dogs given softer radiation without surgery were shorter than those of 14 dogs that were given softer radiation and had cytoreductive surgery. Survival times of dogs that were given softer radiation and had surgery were similar to those of dogs that were given megavoltage radiation only. Cytoreductive surgery did not improve survival times for dogs that were given megavoltage radiation. Median survival time for 38 dogs with adenocarcinoma was 12 months, compared with 6 months for 14 dogs with squamous cell or undifferentiated carcinoma. Median survival time for 16 dogs with a variety of sarcomas was 11.2 months. Survival times of dogs with adenocarcinoma or sarcoma were significantly better (P less than 0.02 or 0.03) than for dogs with squamous cell or undifferentiated carcinoma. Necropsies were performed on 27 of 58 dogs that died or were euthanatized.(ABSTRACT TRUNCATED AT 250 WORDS)

Canine mammary epithelial neoplasms: biologic implications of morphologic characteristics assessed in 232 dogs

We studied 232 dogs that underwent mastectomy for mammary epithelial neoplasms. The mastectomy specimens were evaluated according to structural parameters found to be prognostically significant in human mammary neoplasms, such as grade of atypia in non-invasive proliferations of duct epithelium, extent of malignant disease, and nuclear differentiation in malignant neoplasms. In this study, the biologic behavior of mammary lesions was assessed according to the frequency of development of de novo or recurrent invasive carcinoma within two years. Our data indicate that we can recognize structural variables which permit classification of mammary neoplasms into categories with distinct patterns of biologic behavior. In addition to normotypic proliferative lesions and invasive malignant neoplasms, we were able to identify precancerous atypic and non-invasive malignant neoplasms that are considered precursor lesions in women. Also, as in women, nuclear differentiation was found to be a prognostically significant variable. Lymphoid cellular reactions, considered to be structural correlates of host-tumor immune responses in women, were noted in 35% of dogs with precancerous or malignant neoplasms. Application of the described parameters should facilitate comparative studies of canine and human mammary carcinogenesis and use of the dog as a model for the development of new therapeutic modalities and immunoprophylaxis of human mammary cancer.

Alveolar lavage in dogs

Alveolar lavage was performed in 10 healthy dogs. After tracheal intubation was done, a sterile fiberoptic bronchoscope was wedged in a distant bronchus and the lungs were lavaged with sterile saline solution. An average of 140 ml of saline solution was flushed into the lungs of each dog, and an average of 79% of the solution was recovered. Examination of the recovered fluid revealed average total cell counts of 6.4 X 10(6) cells/dog. Average differential cell counts were as follows: macrophages, 50.5%; lymphocytes, 46.0%; and neutrophils, 3.5%. Results of bacterial culture of the recovered fluid were negative in 8 dogs and positive in 2; Bordetella bronchiseptica was isolated in 1 dog and Klebsiella pneumoniae was isolated in the other.