Feline spinal lymphosarcoma: a retrospective evaluation of 23 cats

A retrospective study of pathologically confirmed cases of feline spinal lymphosarcoma (FSL) admitted to the Colleges of Veterinary Medicine at the University of Georgia and North Carolina State University from 1973 to 1988 was conducted. Two hundred fourteen cases of feline lymphosarcoma were diagnosed histopathologically; involvement of the central nervous system (CNS) was identified in 26 (12.1%). Twenty-three of these tumors involved the spinal cord, and 22 of the 23 were solitary. A predilection for the thoracic and lumbar vertebral canal was noted. Most cats with spinal disease were young, with mean and median ages of 43 and 24 months, respectively; 67 cats were 36 months of age or younger. In most cases, affected cats had acute neurological deterioration after an initial insidious course. Extraneural abnormalities were not consistently present. Neoplastic lymphocytes diagnostic of FSL were identified on cerebrospinal fluid (CSF) analysis in 6 of 17 cats evaluated. Sixteen of 17 cats evaluated had serologically positive test results for feline leukemia virus (FeLV) p27 antigen, and all cats tested for feline immunodeficiency virus (FIV) antibodies had negative test results.

Intracellular metabolism of indium-111-DTPA-labeled receptor targeted proteins

The mechanisms of hepatic and renal accumulation and retention of 111In-labeled proteins has been the subject of many investigations. Because the lysosome is a common intracellular destination for a variety of agents including antibodies and polypeptide hormones, we studied the in vitro and in vivo metabolism of 111In-DTPA-labeled polypeptides using a series of glycoproteins that were concentrated within the lysosome by receptor mediated endocytosis. Indium-111-DTPA-labeled glycoproteins targeted to the mannose, asialoglycoprotein and mannose 6-phosphate receptors were studied in vitro using cell lines known to express these receptors and in vivo using Sprague-Dawley rats. Once internalized, the 111In label was released slowly with 60%-90% (depending on the cell type) of the activity remaining cell associated at 24 hr. Subcellular fractionation using Percoll gradients indicated that the activity remained within the lysosome. Following internalization of the 111In-DTPA-labeled glycoproteins, the label was rapidly converted to a low molecular weight species (estimated molecular weight < or = 1000 daltons). This conversion was not seen with 111In-DTPA-alpha-galactosidase. As a lysosomal enzyme, alpha-galactosidase is relatively resistant to proteolysis within the lysosome. These results suggest that following internalization, 111In-DTPA-polypeptides are delivered to the lysosome where the polypeptide backbone can be degraded to yield 111In-DTPA-amino acid(s). These metabolites remain within the lysosome and are only slowly released from the cell. The model systems used in these studies can also be used to evaluate the intracellular metabolism of polypeptides labeled by other techniques.

The effect of ascorbate on essential fatty acid composition in B16 melanoma cells

Ascorbate has been shown to be involved in essential fatty acid (EFA) metabolism, resulting in the suggestion that the effect of ascorbate on cell growth may be mediated through an influence on the metabolism of these FAs. This study examined the effect of ascorbate, supplemented over the nutritional concentration range of 0-100 micrograms/ml, on the in vitro cell growth of non-malignant LLCMK (monkey kidney) cells and malignant B16 murine melanoma cells. The effect of ascorbate on EFA composition was also investigated, and involved the determination of the levels of linoleic acid (LA), gamma-linoleic acid (GLA), dihomogammalinolenic acid (DGLA) and arachidonic acid (AA) present in the stroma and membrane of the two cell types. Ascorbate had no significant inhibitory or stimulatory effect on the growth of either the LLCMK or B16 cells. EFA levels detected in the LLCMK cells were generally higher than those detected in the B16 cells. The % composition of the various EFAs in the stroma fractions of the two cell types were higher than the level of the corresponding EFAs in the membrane fractions. GLA levels were not detectable in the membrane fractions of the B16 cells. AA % composition determined in both cell types, was greater than that of any other EFA % composition.

Semiquantitative test for Dirofilaria immitis as a predictor of thromboembolic complications associated with heartworm treatment in dogs

A semiquantitative heartworm test of antigen concentration was evaluated as a predictor of thromboembolism after adulticide treatment. Seventeen dogs with naturally acquired infections of Dirofilaria immitis (heartworms) were studied before and after thiacetarsamide treatment, using physical examinations, arterial blood gas analyses, thoracic radiography, and pulmonary hemodynamic and arteriographic tests. Eight dogs were considered to have a low burden of heartworms and 9 had a high burden. Dogs with a high worm burden had more severe pulmonary thromboembolism with pulmonary hypertension, dilated pulmonary arteries, flow obstruction of the caudal pulmonary arteries, and parenchymal lesions in the caudal lung lobes. Dogs with a low worm burden had minimal changes. Within each group of dogs, the severity of thromboembolism was less in some dogs in which all heartworms were not killed. Six of the 9 dogs with a high burden of heartworms had surviving heartworms, and 1 of these dogs had 38 live heartworms. Only 4 of the 8 dogs with a low worm burden had complete heartworm mortality, but only 1 dog had more than 3 surviving heartworms. We concluded that dogs with a high worm burden were more likely to have pulmonary thromboembolism after thiacetarsamide treatment and that dogs with a low worm burden were more likely to have minimal changes. A semiquantitative heartworm test of antigen concentration is recommended as part of the pretreatment evaluation of dogs infected with heartworms.

Pulmonary thromboembolism and hypertension after thiacetarsamide vs melarsomine dihydrochloride treatment of Dirofilaria immitis infection in dogs

The severity of pulmonary thromboembolism and pulmonary hypertension induced by heartworms dying after administration of 2 adulticides was evaluated. Because melarsomine dihydrochloride (RM340) has been shown to be more effective in killing Dirofilaria immitis (heartworms) than the traditional approved adulticide, thiacetarsamide, an attempt was made to determine whether this new adulticide induced more severe lung disease. Before adulticide treatment, 32 dogs with naturally acquired heartworm infections received physical examinations, semiquantitative antigen concentration tests, CBC, platelet counts, serum biochemistry analyses, arterial blood gas determinations, thoracic radiography, pulmonary arteriography, and pulmonary hemodynamic tests. Eight dogs with a low burden and 9 dogs with a high burden of heartworms were treated with thiacetarsamide, and 7 dogs with a low burden and 8 dogs with a high burden were treated with RM340. Except for the heartworm-burden test, tests were repeated at regular intervals during the first 7 weeks after treatment. None of the dogs coughed or had dyspnea after treatment. Six of 9 dogs with high worm burdens and 4 of 8 dogs with low worm burdens had surviving heartworms after thiacetarsamide treatment, in contrast to only 3 of 15 RM340-treated dogs. Differences between the 2 adulticide treatments were minimal as determined by thoracic radiography, pulmonary hemodynamic tests, clinical laboratory analyses, pulmonary arteriography, or necropsy. The RM340 treatment was a more effective adulticide, but it did not increase the severity of hypertension and thromboembolism.

Structural and serological specificities of Pasteurella haemolytica lipopolysaccharides

Lipopolysaccharides (LPSs) from 16 serotypes of Pasteurella haemolytica were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and examined by silver staining and immunoblotting. Silver staining of proteinase K-digested cell lysates revealed two rough LPS serotypes (serotypes 2 and 8), which lacked demonstrable O-polysaccharide, while 14 others demonstrated a ladder pattern characteristic of smooth-type LPS. Purified LPSs from several serotypes yielded O-polysaccharide in addition to low-molecular-weight core oligosaccharide components when subjected to mild acid hydrolysis. Nuclear magnetic resonance spectroscopy revealed the O-chain polysaccharides of serotypes 1, 6, and 9 to be identical. Immunoblots using hyperimmune rabbit, mouse, bovine, and ovine sera from homologous and heterologous serotypes supported this finding and suggested that most of the A biotypes share common O-chain epitopes. Immunoblotting results also supported structural data which demonstrated that the O-polysaccharides of serotypes 3 and 15 and of serotypes 4 and 10 (T biotypes) are identical. Nuclear magnetic resonance analysis indicated that the core oligosaccharides of serotypes 1, 6, 8, 9, and 12 share similar structures, but that they are distinct from those of serotypes 3, 4, 10, and 15. Immunoblots with hyperimmune antisera and monoclonal antibody having specificity for the core region of serotype 1 LPS revealed shared epitopes in the core oligosaccharides of several A biotypes. Characterization of the molecular structure and antigenic specificities of LPS has been an important consideration in the development of purity and potency assays for veterinary vaccines which contain P. haemolytica.

The effect of ascorbic acid on arachidonic acid and prostaglandin E2 metabolism in B16 murine melanoma cells

Ascorbic acid (Asc), arachidonic acid (AA) and prostaglandin E2 (PGE2) are reported to be important in maintaining the stability of the cell matrix. Asc has also been shown to influence fatty acid (FA) and PGE2 synthesis, with the result that effects of Asc on cell growth are suggested to be mediated through the metabolism of these two compounds. This study examined the effect of Asc, supplemented over the concentration range of 0-100 micrograms/ml, on the in vitro cell growth of non-malignant LLCMK (monkey kidney) cells and malignant B16 murine melanoma cells. The effects of Asc supplementation on AA and PGE2 levels in the cell stroma and membrane fractions of the two cell types was also determined. Asc had no significant inhibitory or stimulatory effect on the growth of either the B16 or LLCMK cells. The total percentage AA composition determined in the B16 control cells (combined stroma and membrane fractions), was similar to that determined in the LLCMK control cells. Asc supplementation of the B16 cells, resulted in an inverse relationship between B16 cell growth and total percentage AA composition. PGE2 concentration in the control B16 cells (combined stroma and membrane fractions) was significantly higher than that detected in the control LLCMK cells. No PGE2 was detected in the B16 stroma fraction, with all appearing to be located in the membrane fraction. However, upon the supplementation of the B16 cells with increasing Asc concentrations, PGE2 appeared to be mobilized from the membrane fraction, resulting in increasing PGE2 levels in the stroma fraction relative to the membrane fraction. This was accompanied by a significant decrease in PGE2 concentration, in the membrane fraction. B16 cell growth and total (stroma and membrane fractions) PGE2 concentration in these cells was inversely related, when cultures were supplemented with increasing levels of Asc. Asc supplementation of the LLCMK cells did not appear to have any significant effect on AA or PGE2 metabolism in these cells.

Paratuberculosis in saiga antelope (Saiga tatarica) and experimental transmission to domestic sheep

Mycobacterium paratuberculosis was isolated in low numbers from the small intestine and associated mesenteric lymph nodes of a saiga antelope (Saiga tatarica) using routine culture techniques in spite of histologic evidence of high numbers of acid-fast bacteria in these tissues. Two newborn domestic sheep were fed the ground intestinal tissue containing acid-fast bacteria and the progression of the experimental disease was followed by fecal culture, immunodiffusion (AGID) and lymphocyte stimulation (LST) tests. One experimentally infected sheep developed progressive clinical illness 1 yr postinoculation. Few M. paratuberculosis were isolated from feces or tissues although an extensive granulomatous mycobacterial enteritis, lymphadenitis and lymphangitis were observed containing large numbers of typical acid-fast organisms. No clinical illness was observed in the second inoculated sheep after 18 mo of observation, although infection was demonstrated at necropsy. Both sheep developed AGID and LST reactions indicative of paratuberculosis. This study demonstrated that a difficult to culture isolate of M. paratuberculosis was responsible for paratuberculosis in captive wild ruminants and was transmissible to domestic sheep. Diagnosis of paratuberculosis in four of eight of the imported saiga antelope and in eleven of their 18 offspring indicates the importance of this disease in management of captive wild ruminants and the ease with which this organism can be transmitted.

Effects of phosphorus/calcium-restricted and phosphorus/calcium-replete 32% protein diets in dogs with chronic renal failure

Twenty-four dogs with induced, severe chronic renal failure were allotted to 2 groups of 12 each. Group-A dogs were fed a 0.4% phosphorus (P)/0.6% calcium, 32% protein diet, and group-B dogs were fed a 1.4% P/1.9% calcium, 32% protein diet. Dogs were studied over 24 months to determine clinical status, survival, blood biochemical alterations, glomerular filtration rate (GFR), urinary excretion of P and protein, renal morphologic changes, and renal tissue concentrations of calcium, P, and magnesium. Group-A dogs developed statistically significant differences from group-B dogs in several blood biochemical values (PCV and total solids, calcium, P, potassium, sodium, chloride, total CO2 (TCO2), anion gap, and parathyroid hormone concentrations) and in urinary P excretion. Mean (+/- SEM) GFR values in group-A and group-B dogs were nearly identical when diets were initiated (group A = 0.73 +/- 0.05 ml/min/kg of body weight; group B = 0.72 +/- 0.08 ml/min/kg), but significantly (P = 0.0346) lower GFR developed in group-B than in group-A dogs over time. At 24 months, GFR in survivors was 0.83 +/- 0.08 and 0.63 +/- 0.15 ml/min/kg for dogs of groups A and B, respectively. Other measurements favored the hypothesis that P/calcium restriction was beneficial, but values failed to reach statistical significance. Survival was greater at 24 months in group-A than in group-B (7 vs 5) dogs, and renal tissue concentrations of calcium and P were higher in group-B than in group-A dogs. Differences were not detected between groups in urinary excretion of protein and in the type or severity of renal lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Perfluoroctylbromide as a gastrointestinal contrast agent for MR imaging: use with and without glucagon

The utility of perfluoroctylbromide (PFOB) as a gastrointestinal contrast agent for magnetic resonance (MR) imaging was evaluated with MR examinations performed in 30 subjects (16 healthy volunteers and 14 patients). Transaxial T1-, proton density-, and T2-weighted MR images were acquired in each subject before and after the administration of PFOB. The healthy volunteers each underwent two sets of post-PFOB MR examinations, one before and one after glucagon administration. The degree of bowel marking, clarity of bowel-wall visualization, ability to distinguish bowel from adjacent parenchymal organs, and severity of phase-encoding artifacts were independently analyzed by two reviewers. Oral administration of PFOB significantly (P less than .001) increased the percentage of bowel loops with low signal intensity. Subcutaneous administration of glucagon significantly (P less than .001) increased the clarity of bowel-wall visualization on post-PFOB MR studies. The severity of phase-encoding artifacts did not change substantially after administration of PFOB or glucagon.

Associations between dairy production indices and lipoarabinomannan enzyme-immunoassay results for paratuberculosis

Data from an epidemiological study in Ontario, involving 304 dairy herds, were used to identify associations between selected production indices and lipoarabinomannan antigen serological test results for paratuberculosis (LAM-ELISA). Analyses were conducted at both the herd and individual cow levels of organization. After analytically controlling for management and cow factors in the respective regression models, positive serological paratuberculosis status (as defined by the LAM-ELISA test), was associated with higher milk somatic cell counts at both the herd average (p less than 0.01), and individual cow levels of organization (p less than 0.0001). In contrast, LAM-ELISA test results were consistently not associated with calving intervals in either the herd average or individual cow level analyses. Associations between LAM-ELISA results and milk production were inconsistent. No associations were found at the herd level of organization, and LAM-ELISA results were not associated with a change in breed class average (BCA) for milk, between the previous and the most recent lactations of individual cattle. However, at the individual cow level, LAM-ELISA results were positively associated with higher milk production as measured by the current BCA (p less than 0.05), and individual cow average kg of milk produced per year of life since two years of age (p less than 0.0001).

An evaluation of selected screening tests for bovine paratuberculosis

The objective of this study was to evaluate the performance of the lipoarabinomannan antigen enzyme-linked immunosorbent assay (LAM-ELISA), carbohydrate antigen complement fixation (CH-CFT), and protein D antigen agar gel immunodiffusion (D-AGID) tests for bovine paratuberculosis, relative to histopathology, and to culture and isolation of Mycobacterium paratuberculosis from tissues and feces. Samples for test evaluation were collected from four sources including blood and tissues from 400 cull cows at three abattoirs in Ontario, blood and feces from a paratuberculosis survey of cattle from 120 dairy farms in Ontario, a serum bank containing samples from cattle from Ontario and Québec, and a bank of sera from cattle from Pennsylvania and the northeastern United States. The data were analyzed using receiver operator characteristic curves, estimates of relative sensitivity and specificity, and kappa statistics of agreement between tests. The LAM-ELISA performed significantly better than both the CH-CFT and the D-AGID tests. The LAM-ELISA was better at predicting fecal shedding status than tissue infection. However, the LAM-ELISA also had limitations. When interpreted as positive or negative (+/-), at a critical optical density of 0.675, its sensitivity and specificity relative to bacteriology were 49% and 87% respectively. Although the serological tests examined in this study provided some information, they did not predict well the infection status of individual animals.

An epidemiological study of paratuberculosis in dairy cattle in Ontario: study design and prevalence estimates

An observational study involving 304 dairy herds and three abattoirs was conducted between 1986 and 1989 to investigate the epidemiology of paratuberculosis in dairy cattle in Ontario. The objectives of this paper were to describe the method of data collection for the study, to present descriptive production statistics and to present estimates of the prevalence of paratuberculosis among dairy cattle in Ontario. Mycobacterium paratuberculosis was isolated from the distal ileum and/or the ileocecal lymph node of 5.5% of 400 cull cows. Based on a lipoarabinomannan antigen enzyme-linked immunosorbent assay (LAM-ELISA) on sera, the predicted true prevalence of paratuberculosis among 14,923 dairy cattle from 304 herds, was 6.1%. Nineteen percent of 2,943 fecal cultures were uninterpretable because of overgrowth with contaminating bacteria or fungi. It was concluded that the true prevalence of paratuberculosis among dairy cattle in Ontario was no greater, and may be less than the true prevalence among dairy cattle from various regions of the United States. However, at a practical level, for the purposes of trade policy, the present study suggests that the functional prevalence is very similar in the two countries.

The effect of gamma-linolenic acid and zinc supplementation on the growth of normal and tumour cells in vitro

The effects of zinc, gamma-linolenic acid (GLA) and zinc combined and GLA supplementations on the growth of a benign monkey kidney, cell line (LLCMK) and a malignant tumour murine melanoma, cell line (BL-6) cells in vitro were studied. Cell growth was indicated by both cell counts and 3H-thymidine incorporation into DNA. The addition of zinc to the cells resulted in a general trend of overall reduction in the growth of tumour cells but not in the normal cells. The addition of GLA at high concentrations resulted in a general decrease in cell growth of both the benign and malignant tumour cells while the addition of lower concentrations of GLA had less effect. The combined effect of supplementary zinc and GLA resulted in an inhibitory effect on the growth of the malignant cells while a less and variable effect on the non-malignant cells was found. Some interaction between zinc and GLA in reducing tumour cell growth is suggested by the results.

Possible involvement of delta-6-desaturase in control of melanoma growth by gamma-linolenic acid

This study examined the effects of linoleic acid (LA) and gamma-linolenic acid (GLA) on BL6 melanoma growth in cell culture and of safflower oil (SFO) which contains LA and evening primrose oil (EPO) which contains GLA, on melanoma growth when grown in mice. The delta-6-desaturase activity of the melanoma cells in the two systems was also examined and an attempt made to relate the activity of the enzyme to the effects of GLA on cell and tumour growth. LA and GLA were found to be equipotent in inhibiting growth of the in vitro cultured BL6 cells which were found to contain an appreciable level of delta-6-desaturase activity. EPO was however found to be a more potent promoter of in vivo melanoma growth in mice than SFO. Melanomas grown in mice were found to lack delta-6-desaturase activity suggesting that the EPO diet, by providing GLA, was able to compensate for the loss of enzyme activity in the melanomas. The possibility that melanomas in mice have a requirement for GLA for growth while in in vitro cultured cells excess GLA inhibits the growth of the cells through an increase in lipid peroxidation is discussed.

Protein G-based enzyme-linked immunosorbent assay for anti-MPB70 antibodies in bovine tuberculosis

MPB70 is a highly species specific protein which is secreted from Mycobacterium bovis during culture. To investigate whether antibodies against MPB70 can be used as an indicator of infection with M. bovis, an enzyme-linked immunosorbent assay was developed, based on the use of biotinylated protein G, to provide a common indicator for antibody formation in different species. During experimental infection with M. bovis in cattle, a characteristic pattern of anti-MPB70 antibody production was observed with an initial flat plateau followed by a marked rise 18 to 20 weeks after infection. Skin testing with bovine tuberculin purified protein derivative (PPD), which was shown to contain antibody-reactive MPB70, was a potent stimulator of antibody production in infected animals. In experimentally infected cattle, we observed an inverse relationship between antibody activity and delayed-type hypersensitivity skin test reactions. In natural M. bovis infections, skin testing with PPD was also a potent stimulator of anti-MPB70 formation. Comparison between the enzyme-linked immunosorbent assay for antibodies to MPB70 and that for antibodies to the widely cross-reacting M. bovis BCG antigen 85B in animals with M. bovis, Mycobacterium avium, Mycobacterium paratuberculosis, and Corynebacterium pseudotuberculosis infections showed that formation of antibody to MPB70 was highly specific for infection with M. bovis. The use of an MPB70-containing PPD preparation for skin testing followed by this anti-MPB70 assay is a highly specific indicator of M. bovis infection. Adjustment of the test conditions is expected to provide an increased sensitivity of the procedure for the diagnosis of natural M. bovis infections.

Capacity of passively administered antibody to prevent establishment of Brucella abortus infection in mice

In contrast to immunity against some other facultative intracellular parasites, protective immunity against Brucella abortus is mediated in mice by antibodies as well as by cell-mediated immune responses. It was the purpose of this study to determine whether antibody alone would prevent infection with B. abortus. The majority (82%) of CD-1 outbred mice infected with 100 CFU of virulent B. abortus 2308 preincubated with graded quantities of an O polysaccharide-specific IgG2a monoclonal antibody (MAb) were free of infection 1. 2, 4, and 6 weeks later, based on detection limits of 13 brucellae per spleen and 39 per liver. Infection was present in 95% of control animals. Similar results were obtained with a challenge dose of 500 CFU, but with a challenge dose of 5,000 CFU, infection became established even with the highest concentration of MAb used (50 micrograms of MAb per 5,000 brucellae). Pretreatment with an O polysaccharide-specific IgG1 MAb or with convalescent-phase serum diminished but did not prevent establishment of infection by 100 CFU of B. abortus. A majority of culture-negative mice tested 6 weeks after infection were serologically negative, which could have signified either the absence of previous infection or the early elimination of infection. In an in vitro test system, all of the antibody preparations were efficient in opsonizing B. abortus. Effective killing of the organism by unelicited mouse peritoneal macrophages occurred in conventional but not in endotoxin-free medium, suggesting that activated macrophages were required for killing of opsonized B. abortus. These results emphasize the potential importance of antibodies in the immunoprophylaxis of brucellosis and suggest that the design of a successful vaccine will require the induction of antibodies not only of appropriate specificity but also of the optimal isotype for mediating protective functions.

Serodiagnosis of ovine paratuberculosis, using lipoarabinomannan in an enzyme-linked immunosorbent assay

The use of lipoarabinomannan (LAM; obtained from Mycobacterium paratuberculosis) in and ELISA (LAM-ELISA) to test 75 sheep sera from a paratuberculosis-infected flock resulted in an approximate threefold increase in sensitivity (from 23.5% to 70.6%), compared with the use of Annau's polysaccharide in a complement fixation test (P-CFT). Even after manipulation of the LAM-ELISA cut-off value to produce a specificity of 100% to match that of the P-CFT, the sensitivity still was approximately twofold greater than that of the P-CFT. Anti-bovine monoclonal antiglobulin-enzyme conjugates matched commercially available anti-ovine polyclonal antiglobulin-enzyme conjugates with respect to sensitivity and specificity. False-positive results were found to be less frequent after combining 2 serodiagnostic tests, LAM-ELISA and D antigenagar gel immunodiffusion, resulting in an increase in specificity from 88.1% to 95.2%. The repeatability of true seropositive and seronegative results was found to be 89.5% and 91.1%, respectively, for sera obtained less than or equal to 1 month prior to slaughter and 91.7% and 95.5%, respectively, for reanalysis of sera obtained at the time of slaughter.

Inhibition of murine melanoma growth by sodium ascorbate

Ascorbic acid has been reported to play a role in treatment and prevention of cancer. This study was carried out to determine the effect of ascorbate on growth of normal LLCMK cells and transformed BL6 cells in cell culture and on the growth of BL6 melanomas in vivo. Ascorbic acid levels were also measured to determine the effect of tumor growth and supplementary ascorbate on cellular ascorbic acid levels. Ascorbate addition at levels of up to 200 micrograms/ml was found to inhibit the in vitro growth of BL6 cells but not of LLCMK cells. Ascorbic acid levels in both cell types were very similar. The presence of tumors was found to reduce liver ascorbic acid levels in mice. Supplementary dietary ascorbate increased liver and tumor ascorbic acid levels and also reduced the growth of BL6 melanomas transplanted in C57 mice. Ascorbate thus appears to play a role in suppression of BL6 melanoma growth.

Enzyme-linked immunosorbent assay for differentiation of the antibody response of cattle naturally infected with Brucella abortus or vaccinated with strain 19

Purified O chain of Brucella abortus was passively attached to polystyrene to differentiate antibody responses of cattle vaccinated with B abortus strain 19 from those of naturally infected cattle. In the indirect assay, using O polysaccharide as antigen, a single serum dilution was used and mouse monoclonal antibody to bovine L chain conjugated with horseradish peroxidase was the detection reagent. Measurable antibody was not found in sera of vaccinated cattle, except for 3 sera from cattle that were persistently infected with strain 19. Sera from 25 cattle infected with pathogenic strains contained antibody on the basis of results of indirect enzyme immunoassay, using smooth lipopolysaccharide or O chain as antigens, or results of competitive enzyme immunoassay, using the O-chain antigen. Results in sera from calves with experimentally induced Yersinia enterocolitica serotype 0:9 infection or inoculated with a low dose of B abortus strain 2308 were comparable with those in sera of cattle that were vaccinated with strain 19. The data correlated with those from competitive enzyme immunoassay, using one serum dilution and horseradish peroxidase-conjugated mouse monoclonal antibody to smooth lipopolysaccharide. On the basis of results of the indirect enzyme immunoassay, all sera (except those samples obtained before inoculation) contained antibody to smooth lipopolysaccharide.

Effectiveness of natural and synthetic complexes of porin and O polysaccharide as vaccines against Brucella abortus in mice

A single vaccination of mice with a complex of porin and smooth lipopolysaccharide (porin-S-LPS) extracted from virulent Brucella abortus 2308 provided significant protection (P less than 0.01 to P less than 0.001) against challenge with the same strain, equivalent to that achieved by vaccination with living attenuated B. abortus 19. The porin-S-LPS vaccine given without adjuvant or in several adjuvants (trehalose dimycolate and muramyl dipeptide; the pluronic polymer L-121 and muramyl dipeptide; or complexed with Quil A in immunostimulating complexes) provided equivalent protection. In contrast, one vaccination with porin complexed with rough LPS (porin-R-LPS) from a rough mutant of strain 2308 provided no protection with any adjuvant tested. In one experiment, two inoculations with the porin-R-LPS resulted in a low level of protection, probably owing to priming of the animals for production of O-polysaccharide-specific antibodies. However, one vaccination with rough-strain porin covalently bound to purified O polysaccharide conferred protection equal to that obtained with natural complexes of porin-S-LPS or with living strain 19. A synthetic vaccine containing long chains of O polysaccharide was more effective than one prepared with short chains. Protective vaccines caused the formation of increased concentrations of circulating O-polysaccharide-specific antibodies, although there were individual exceptions to the quantitative association between O-polysaccharide-specific antibodies and protection. Antibodies specific for porin or R-LPS were found in negligible quantities in vaccinated mice. These results provide additional evidence that the O polysaccharide will constitute an essential component of an effective subcellular vaccine against B. abortus and that O-polysaccharide-specific antibodies play an important role in protective immunity in brucellosis.

Enhanced prostaglandin synthesis as a mechanism for inhibition of melanoma cell growth by ascorbic acid

Both ascorbic acid and the 1-series prostaglandins have been reported to be important regulators of cell growth and since ascorbic acid also increases the synthesis of the 1-series prostaglandins, it is possible that the effects of ascorbic acid on cell growth might be mediated by changes in 1-series prostaglandin synthesis induced by ascorbic acid. This study attempted to examine this possible relationship. The effects of ascorbic acid, prostaglandin E1 and the essential fatty acid precursors of the prostaglandins, linoleic acid and gamma-linolenic acid on the in vitro growth of transformed BL6 murine melanoma cells and untransformed monkey kidney (LLCMK) cells was determined. The effects of ascorbic acid addition on the growth inhibitory effect of the essential fatty acids and on the activity of delta-6-desaturase, a key enzyme in 1-series prostaglandin synthesis were also examined. Addition of ascorbic acid, prostaglandin E1 and both essential fatty acids was found to reduce BL6 growth while PGE1 and to a lesser extent the essential fatty acids reduced LLCMK cell growth. The growth inhibitory effect of the essential fatty acids was enhanced by ascorbic acid which was also found to stimulate delta-6-desaturase activity in BL6 cells. The growth inhibitory effect of ascorbic acid on BL6 cells may thus be mediated by changes in prostaglandin synthesis through an association with the metabolism of the essential fatty acid precursors of the prostaglandins.

Further evidence that bovine IgM does not fix guinea pig complement

In a study of sera from cattle vaccinated with 3 X 10(10) cfu of Brucella abortus strain 19, it was found that IgG1 antibody measured by an indirect ELISA was the only isotype to correlate with standard complement fixing antibody titers using heated serum samples and guinea pig serum as a source of complement. A supplement of normal unheated bovine serum resulted in IgM fixing guinea pig complement, giving data similar to those obtained with unheated serum in the complement fixation test.