Influence of two diets on pharmacokinetic parameters of allopurinol and oxypurinol in healthy beagles

OBJECTIVES

To determine whether diet influences the metabolism of IV administered allopurinol in healthy dogs.

ANIMALS

6 healthy female Beagles, 4.9 to 5.2 years old and weighing 9.6 to 11.5 kg.

PROCEDURES

Allopurinol was administered IV (10 mg/kg) while dogs consumed a 10.4% protein (dry weight), casein-based diet or a 31.4% (dry weight), meat-based diet. After each dose, plasma samples were obtained at timed intervals, and concentrations of allopurinol and its active metabolite, oxypurinol, were determined by high-performance liquid chromatography. An iterative, nonlinear regression analytical program was used to determine the weighted least-squares, best-fit curves for plasma allopurinol and oxypurinol concentration-time data. From these data, pharmacokinetic parameters were calculated.

RESULTS

Pharmacokinetic parameters for allopurinol and oxypurinol were not different when comparing the effect of diet.

CONCLUSION

There is no influence of diet on pharmacokinetic parameters of allopurinol or oxypurinol.

CLINICAL RELEVANCE

In contrast to observations in human beings, allopurinol metabolism is not influenced by diet. Therefore, formation of xanthine-containing calculi in dogs consuming a high-protein diet and receiving allopurinol is probably not attributable to alteration of allopurinol metabolism.

Bioavailability and pharmacokinetics of intravenously and orally administered allopurinol in healthy beagles

OBJECTIVES

To determine bioavailability and pharmacokinetic parameters for allopurinol and its active metabolite, oxypurinol.

ANIMALS

6 healthy, reproductively intact female Beagles, 4.9 to 5.2 years old, and weighing 9.5 to 11.5 kg.

PROCEDURE

In the first part of the study, allopurinol was administered IV at a dosage of 10 mg/kg of body weight to 3 dogs and 5 mg/kg to 3 dogs; the sequence was then reversed. In the second part of the study, allopurinol was administered orally at a dosage of 15 mg/kg to 3 dogs and 7.5 mg/kg to 3 dogs; the sequence was then reversed. In the third part of the study, allopurinol was administered IV (10 mg/kg), orally (15 mg/kg) with food, and orally (15 mg/kg) without food. Plasma samples were obtained at timed intervals, and concentrations of allopurinol and oxypurinol were determined.

RESULTS

Maximal plasma allopurinol concentration and area under plasma allopurinol and oxypurinol concentration-time curves were 2 times greater when dogs were given 10 mg of allopurinol/kg IV, compared with 5 mg/kg, and when dogs were given 15 mg of allopurinol/kg orally, compared with 7.5 mg/kg. Allopurinol elimination half-life, time to reach maximal plasma oxypurinol concentration, and oxypurinol elimination half-life were significantly greater when dogs received 10 mg of allopurinol/kg IV, compared with 5 mg/kg, and when dogs received 15 mg of allopurinol/kg orally, compared with 7.5 mg/kg.

CONCLUSIONS

Elimination of allopurinol is dependent on nonlinear enzyme kinetics. The bioavailability of allopurinol, and pharmacokinetic parameters of allopurinol and oxypurinol after oral administration of allopurinol, are not affected by administration with food.

CLINICAL RELEVANCE

A dose threshold exists beyond which additional allopurinol would not substantially further inhibit xanthine oxidase activity. Oral administration of > 15 mg of allopurinol/kg to dogs would not be expected to result in greater reduction of plasma and urine uric acid concentrations. Also, allopurinol may be administered to dogs for dissolution or prevention of urate uroliths without regard to time of feeding.

Effects of time and dilution on concentration of xanthine in frozen urine and plasma of dogs

OBJECTIVE

To evaluate the effects of dilution on stability of xanthine in canine urine stored at -20 C, and to evaluate the effects of storage at -20 C on stability of xanthine in canine plasma.

ANIMALS

6 reproductively intact female Beagles, 3.9 to 4.2 years old and weighing 8.5 to 10.1 kg.

PROCEDURE

Dogs were fed a 31.4% protein (dry weight), meat-based diet for 21 days, and administered allopurinol (15 mg/kg of body weight, q 12 h) during days 14 to 21; urine and plasma samples were obtained on day 22. Urine samples were preserved undiluted or diluted, and divided into 1-ml aliquots for storage at -20 C for 1 to 12 weeks. Plasma samples were divided into 1-ml aliquots for storage at -20 C for 1 to 12 weeks. Urine and plasma xanthine concentrations were measured on day of collection (baseline) and after 1, 2, 4, 6, 9, and 12 weeks.

RESULTS

Dilution of urine samples did not have a significant effect on consistency of xanthine concentration measured for up to 12 weeks of storage. Although xanthine concentration did not differ significantly between undiluted and diluted urine samples, average xanthine concentration measured in diluted samples was consistently higher, compared with that in undiluted samples. Compared with baseline values, plasma xanthine concentration was significantly lower at 6, 9, and 12 weeks of storage.

CONCLUSIONS

Measurement of xanthine concentration is reproducible in undiluted or diluted urine samples for up to 12 weeks, although dilution may provide better results. Measurement of plasma xanthine concentration is reproducible in samples stored for up to 4 weeks.

CLINICAL RELEVANCE

To ensure reproducibility of measurements of xanthine concentration in urine samples collected from dogs that are affected with urate uroliths and receiving allopurinol, urine should be diluted 1:20 with deionized water. These measurements may be useful for monitoring dogs that are receiving allopurinol for dissolution or prevention of urate uroliths.

Epidural administration of bupivacaine, morphine, or their combination for postoperative analgesia in dogs

OBJECTIVE

To compare the analgesic effects of epidural administration of morphine (MOR), bupivacaine hydrochloride (BUP), their combination (COM), and 0.9% sterile NaCl solution (SAL) in dogs undergoing hind limb orthopedic surgeries.

DESIGN

Blinded, randomized clinical trial.

ANIMALS

41 healthy dogs admitted for elective orthopedic surgeries involving the pelvis or hind limbs.

PROCEDURE

Analgesic and control agents were administered postoperatively prior to recovery from isoflurane anesthesia. Ten dogs received MOR, 0.1 mg/kg of body weight; 10 received BUP, 0.5%, 1 ml/10-cm distance from the occipital protuberance to the lumbosacral space; 11 received COM; and 10 received SAL epidurally. Dogs were monitored for 24 hours after epidural injection for pain score, heart and respiratory rates, blood pressure, time to required administration of supplemental analgesic agent, total number of supplemental doses of analgesic agent required, and plasma concentrations of cortisol, MOR, and BUP.

RESULTS

Pain scores were significantly lower in dogs in the COM and BUP groups than in dogs in the SAL group. Pain scores also were significantly lower in dogs in the COM group than in dogs in the MOR group. Time to required administration of supplemental analgesic agent was longer for dogs in the COM group than for dogs in the MOR and SAL groups. Total number of supplemental doses of analgesic agent required was lower for dogs in the BUP and COM groups than for dogs in the SAL group.

CLINICAL IMPLICATIONS

Postoperative epidural administration of COM or BUP alone provides longer-lasting analgesia, compared with MOR or SAL.

Effects of various methods of preservation on the stability of uric acid in frozen canine urine

OBJECTIVE

To evaluate the effects of dilution and alkalinization, separately and together, on the stability of uric acid in canine urine stored at -20 C.

DESIGN

Prospective-controlled study.

ANIMALS

5 dogs with confirmed ammonium urate uroliths, 6 Beagles, and 6 mixed-breed dogs.

PROCEDURE

Dogs were fed a 31.4% protein (dry weight), meat-based diet for 21 days, and urine samples were collected on day 22. Urine samples were preserved, using combinations of dilution and alkalinization, and divided into 1-ml aliquots for storage at -20 C for 1 to 12 weeks. Urine uric acid concentrations were measured, using high-performance liquid chromatography, on day of collection (baseline), and after 1, 2, 4, 8, and 12 weeks.

RESULTS

Alkalinization did not have a significant effect on reproducibility of measurements of uric acid concentrations in urine; however, dilution did have a significant effect. Compared with baseline, uric acid concentrations in urine samples collected from dogs with ammonium urate uroliths and Beagles and diluted 1:10 or 1:20 with deionized water were not different after storage for 1 to 12 weeks. Uric acid concentrations in urine samples collected from mixed-breed dogs did not differ from baseline values during the 12-week storage period whether samples were undiluted or were diluted 1:10 or 1:20 with deionized water.

CONCLUSIONS

Measurements of uric acid concentration are most reproducible in canine urine samples stored at -20 C for 1 to 12 weeks when samples are diluted 1:20 with deionized water.

CLINICAL RELEVANCE

To ensure reproducibility of measurements of uric acid concentration in urine samples collected from dogs affected with urate uroliths, urine should be diluted 1:20 with deionized water. Alkalinization is not necessary, and is not recommended because of the additional step in processing and its potential to interfere with measurement of other urinary analytes.

Influence of four diets on uric acid metabolism and endogenous acid production in healthy beagles

OBJECTIVE

To evaluate the influence of 3 diets used to dissolve or prevent ammonium urate uroliths in dogs, and a diet formulated for growth, on 24-hour excretions of uric acid, ammonia, net acid, titratable acid, bicarbonate, and creatinine; 24-hour urine volumes; pH values of 24-hour urine samples; plasma uric acid concentration; serum creatinine concentration; and endogenous creatinine clearance values.

DESIGN

Randomized block.

ANIMALS

Six reproductively intact female Beagles, 3.9 to 4.2 years old, weighing 8.5 to 11.1 kg.

PROCEDURES

Four diets were evaluated for their ability to dissolve magnesium ammonium phosphate hexahydrate (struvite) uroliths (diet S); to minimize uric acid excretion (diet U); to minimize clinical signs associated with renal failure (diet K); and to promote growth in pups (diet P). Each diet was fed for 14 days; then 24-hour urine samples were collected. An adult maintenance diet was fed during a 7-day washout period.

RESULTS

Consumption of diet U was associated with lowest plasma uric acid concentration, lowest 24-hour urinary uric acid, ammonia, titratable acid, and net acid excretions, lowest endogenous creatinine clearance values, highest 24-hour urinary bicarbonate excretion and urine pH values, and highest 24-hour urine volumes. Consumption of diet P was associated with opposite results; results of consumption of diets S and K were intermediate between those for diets U and P.

CONCLUSION

Consumption of diet U by healthy Beagles is associated with reduced magnitude of urinary excretion of uric acid and ammonia, with alkaluria, and with polyuria, which may be beneficial in the management of ammonium urate uroliths in dogs.

CLINICAL RELEVANCE

Results support use of diet U for management of ammonium urate urolithiasis in dogs.

Influence of two amounts of dietary casein on uric acid, sodium urate, and ammonium urate urinary activity product ratios of healthy beagles

Casein has been used as a protein source in diets designed to dissolve canine ammonium urate uroliths and to prevent their recurrence, because it contains fewer purine precursors than do many other sources of protein. However, an important question is whether reduced quantities of dietary casein have any benefit in modifying saturation of urine with urates. To answer this question, activity product ratios of uric acid, sodium urate, and ammonium urate were determined in 24-hour urine samples produced by 6 healthy Beagles during periods of consumption of a 10.4% protein, casein-based (10.4% casein) diet and a 20.8% protein, casein-based (20.8%casein) diet. Significantly lower 24-hour urinary excretions of ammonia and phosphorus were observed when dogs consumed the 10.4% casein diet. These results suggest that use of the 10.4% casein diet in protocols designed for dissolution and prevention of uric acid, sodium urate, and ammonium urate uroliths in dogs may be beneficial.

Influence of allopurinol and two diets on 24-hour urinary excretions of uric acid, xanthine, and ammonia by healthy dogs

Hyperxanthinuria and xanthine uroliths have been recognized with increased frequency in dogs with ammonium urate uroliths that had been given allopurinol. We hypothesized that dietary modification might reduce the magnitude of uric acid and xanthine excretion in urine of dogs given allopurinol. To test this hypothesis, excretion of metabolites, volume, and pH were determined in 24-hour urine samples produced by 6 healthy Beagles during periods of allopurinol administration (15 mg/kg of body weight, PO, q 12 h) and consumption of 2 special purpose diets: a 10.4% protein (dry matter), casein-based diet and a 31.4% protein (dry matter), meat-based diet. Significantly lower values of uric acid (P = 0.004), xanthine (P = 0.003), ammonia (P = 0.0002), net acid (P = 0.0001), titratable acid (P = 0.0002), and creatinine (P = 0.01) excreted during a 24-hour period were detected when dogs consumed the casein-based diet and were given allopurinol, compared with the 24-hour period when the same dogs consumed the meat-based diet and were given allopurinol. For the same 24-hour period, urine pH values, urine volumes, and urine bicarbonate values were significantly (P = 0.0004, P = 0.04, and P = 0.002, respectively) higher during the period when the dogs were fed the casein-based diet and given allopurinol than when they were fed the meat-based diet and given allopurinol. Endogenous creatinine clearance was significantly (P = 0.006) lower when dogs were fed the casein-based diet and given allopurinol than when they were fed the meat-based diet and given allopurinol.(ABSTRACT TRUNCATED AT 250 WORDS)

Diet effect on activity product ratios of uric acid, sodium urate, and ammonium urate in urine formed by healthy beagles

Urine activity product ratios of uric acid, sodium urate, and ammonium urate and urinary excretion of metabolites were determined in 24-hour samples produced by 6 healthy Beagles during periods of consumption of a low-protein, casein-based diet (diet A) and a high-protein, meat-based diet (diet B). Comparison of effects of diet A with those of diet B revealed: significantly lower activity product ratios of uric acid (P = 0.025), sodium urate (P = 0.045), and ammonium urate (P = 0.0045); significantly lower 24-hour urinary excretion of uric acid (P = 0.002), ammonia (P = 0.0002), sodium (P = 0.01), calcium (P = 0.005), phosphorus (P = 0.0003), magnesium (P = 0.01), and oxalic acid (P = 0.004); significantly (P = 0.0001) higher 24-hour urine pH; and significantly (P = 0.01) lower endogenous creatinine clearance. These results suggest that consumption of diet A minimizes changes in urine that predispose dogs to uric acid, sodium urate, and ammonium urate urolithiasis.

Influence of four diets containing approximately 11% protein (dry weight) on uric acid, sodium urate, and ammonium urate urine activity product ratios of healthy beagles

Urine activity product ratios of uric acid (APRua), sodium urate (APRna), and ammonium urate (APRau), and urinary excretion of 10 metabolites were determined in 24-hour urine samples produced by 6 healthy Beagles during periods of consumption of 4 diets containing approximately 11% protein (dry weight) and various protein sources: a 72% moisture, casein-based diet; a 10% moisture, egg-based diet; a 72% moisture, chicken-based diet; and a 71% moisture, chicken-based, liver-flavored diet. Significantly (P < 0.05) higher APRua, APRna, and APRau were observed when dogs consumed the egg-based diet, compared with the other 3 diets; there were no differences in these ratios among the other 3 diets. Twenty-four-hour urinary excretions of chloride, potassium, phosphorus, and oxalic acid were significantly (P < 0.05) higher when dogs consumed the egg-based diet. Twenty-four-hour urinary excretions of sodium were significantly (P < 0.05) higher when dogs consumed the egg-based diet, compared with the casein-based diet and the chicken-based, liver-flavored diet, but were not significantly different between the egg-based diet and chicken-based diet. Twenty-four-hour urine volume was similar when dogs consumed the 4 diets. Twenty-four-hour endogenous creatinine clearance was significantly (P < 0.05) lower when dogs consumed the casein-based diet; there were no differences among the other 3 diets. Although consumption of all diets was associated with production of alkaline urine, the 24-hour urine pH was significantly (P < 0.05) higher when dogs consumed the egg-based diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma ferulenol concentration and activity of clotting factors in sheep with Ferula communis variety brevifolia intoxication

Dynamics of plasma ferulenol concentration and its effect on the vitamin K-dependent coagulation factors, prothrombin time (PT), and activated partial thromboplastin time (APTT) were determined in 4 sheep intoxicated individually with 600 g of powdered Ferula communis variety brevifolia (FCb) given in 8 doses at intervals of 6 hours. Ferulenol was detected in the plasma of all sheep at initial blood sample collection, 6 hours after the first dose of approximately 75 g of FCb was placed in the rumen. The last observed peak of approximately 20 micrograms/ml was detected at about 12 hours after the last of 8 doses, and the mean concentration then decreased to < 1 microgram/ml during the next 70 hours. Maximal concentration of ferulenol and time for plasma clearance varied with individual sheep. The PT increased steadily to a maximum of 6 times normal about 70 hours after the last peak plasma ferulenol concentration and about 80 hours after FCb administration was stopped. The PT then returned to almost normal (ratio of 1.12) from the maximum (ratio of 6.12) within approximately 5 days. The APTT results generally paralleled the PT results, but the change was not as marked. Maximal PT and APTT ratios were animal-dependent and not always related to plasma ferulenol concentration. The activity of all the vitamin K-dependent coagulation factors was depressed, but the variations were unique to each factor. Factor V, a vitamin K-independent coagulation factor actually had a brief period of increased plasma activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Reliability of single urine and serum samples for estimation of 24-hour urinary uric acid excretion in six healthy beagles

Urine uric acid-to-urine creatinine ratios (UUA:UC), urine uric acid concentrations, urine uric acid concentrations corrected for glomerular filtration rate, and urinary uric acid fractional excretions were compared with 24-hour urinary uric acid excretions measured in 6 healthy adult female Beagles. Comparisons, using correlation analysis, were made when dogs consumed a 10.4% protein (dry weight), casein-based diet and a 31.4% protein (dry weight), meat-based diet. The UUA:UC, urine uric acid concentrations corrected for glomerular filtration rate, and urinary uric acid fractional excretions were not reliable estimates of 24-hour urinary uric acid excretions during consumption of either diet. Urine uric acid concentrations in samples collected 2, 4, 6, and 24 hours after initiation of collection correlated with 24-hour urinary uric acid excretions when dogs consumed the casein-based diet; correlation was not found at any time interval when dogs consumed the meat-based diet. Therefore, determination of 24-hour urinary uric acid excretion is recommended because UUA:UC are unreliable.

Simultaneous determination of eight anticoagulant rodenticides in blood serum and liver

A liquid chromatographic method was developed for the analysis of indandione and 4-hydroxycoumarin anticoagulant rodenticides in blood serum and liver. The method enabled the measurement of serum and liver concentrations of eight anticoagulant rodenticides: brodifacoum, bromadiolone, chlorophacinone, coumafuryl, coumatetralyl, diphacinone, difenacoum, and warfarin. Anticoagulants were extracted from serum and liver with acetonitrile. Extracts were applied to solid-phase extraction columns, which contained mixed packings. Column eluates were evaporated to dryness, reconstituted, and subjected to reversed-phase liquid chromatography. Hydroxycoumarins were detected by fluorescence at an excitation wavelength of 318 nm and an emission wavelength of 390 nm. Indandiones were detected by UV absorption at 285 nm. Extraction efficiencies of greater than 75% for serum and greater than 69% for liver were obtained. The within-run precision (CV) ranged from 2.4 to 8.6% for serum and 2.6 to 8.7% for liver. The between-run precision (CV) ranged from 1.5 to 12.2% for serum and from 2.1 to 11.8% for liver. Hydroxycoumarin rodenticides were detected at 1 ng/mL of serum and 1 ng/g of liver. Indandiones were detected at 10 ng/mL of serum and 10 ng/g of liver.

Elevated 25-hydroxy and normal 1,25-dihydroxy cholecalciferol serum concentrations in a successfully-treated case of vitamin D3 toxicosis in a dog

A 4-y old, 27 kg spayed female German Shepherd dog was observed to ingest one 1-oz package of a rodenticide containing cholecalciferol. An initial serum calcium concentration of 15.7 mg/dl was successfully reduced to normal during 10 d using calcitonin and prednisolone. During that time, the serum 25-hydroxy and 1,25-dihydroxy cholecalciferol concentrations ranged from 637 to 315 ng/ml (normal 32 +/- 6 ng/ml) and 64 to 29 pg/ml (normal 34 +/- 19 pg/ml), respectively. Serum mid-molecule parathyroid hormone concentrations (76 to 97 pcmol/L) were within the normal range (85-140 pcmol/L). These data indicate that hypercalcemia seen in dogs following field exposures to cholecalciferol-containing rodenticides may be associated with elevated 25-hydroxy rather than 1,25-dihydroxy cholecalciferol. Consequently, serum 25-hydroxy cholecalciferol concentrations may be the most conclusive method for diagnosing hypervitaminosis D3 toxicosis in the live dog.

Relationship between the iron regulated outer membrane proteins and the outer membrane proteins of in vivo grown Pasteurella multocida

The SDS-PAGE patterns of the outer membrane protein (OMP) extracts of Pasteurella multocida strain P1059, grown under iron-restricted, iron-replete and in vivo conditions, were examined. The results showed that the iron-regulated outer membrane proteins (IROMPs) with molecular masses of 76 kDa, 84 kDa, and 94 kDa were expressed by bacteria grown in iron-restricted media. They were also expressed by in vivo grown P. multocida. Convalescent-phase sera, obtained from turkeys which had survived pasteurellosis, contained antibodies that reacted intensly with th three IROMPs. This indicated that these proteins were expressed in vivo. Bacteria expressing the IROMPs showed greater binding to Congo Red when compared to cells not expressing IROMPs. Cells expressing the IROMPs or its OMP extracts grown in iron-restricted media also showed greater binding to 59Fe-pasteurella siderophore (multocidin) when compared to bacteria or its extracts not expressing IROMPs. Convalescent-phase sera, which contained antibodies against the IROMPs, blocked this specific 59Fe-multocidin binding to IROMPs. Autoradiography was used to determine which of these IROMPs functioned as a receptor for the iron-multocidin complex. The results suggested that these three IROMPs have specific epitopes for binding to the iron multocidin complex.

Multicomponent determination of 4-hydroxycoumarin anticoagulant rodenticides in blood serum by liquid chromatography with fluorescence detection

A sensitive liquid chromatographic method was developed for the analysis of 4-hydroxycoumarin anticoagulant rodenticides in blood serum. The method can simultaneously measure the serum levels of five anticoagulant rodenticides: brodifacoum, bromadiolone, coumatetralyl, difenacoum, and warfarin. Serum proteins are precipitated with acetonitrile and the supernatant is mixed with ethyl ether. The organic phase is separated, evaporated to dryness, and the residue subjected to chromatographic analysis. The anticoagulants are separated by reversed-phase gradient chromatography with fluorescence detection at an excitation wavelength of 318 nm and emission wavelength of 390 nm. Extraction efficiencies of 68.1 to 98.2% were obtained. The within-run precision (CV) ranged from 2.19 to 3.79% and the between-run precision (CV) from 3.72 to 9.57%. The anticoagulants can be quantitated at serum levels of 10 to 20 ng/mL.

Superwarfarin ingestion and detection

Because of the emergence of warfarin resistance, new potent long-acting anticoagulants are now readily available in several over-the-counter rodenticide products. The availability of these "superwarfarin" compounds has led to accidental and purposeful human ingestions, one of which has resulted in a death. We summarize the prior case reports and report a second death. In addition, we report the availability of an assay to detect the presence of brodifacoum (a superwarfarin compound) in human plasma and tissues.

Medical dissolution and prevention of canine and feline uroliths: diagnostic and therapeutic caveats

Medical protocols designed to promote the dissolution of canine and feline struvite uroliths, the dissolution of canine ammonium urate and cystine uroliths and the prevention of all major types of canine and feline uroliths have been developed. However, because the causes of different types of uroliths vary, the medical protocols for their dissolution and prevention also vary. When the diagnosis of the underlying causes of uroliths becomes the rule rather than the exception, therapeutic failures should become the exception rather than the rule.

The determination of the anticoagulant rodenticide brodifacoum in blood serum by liquid chromatography with fluorescence detection

A sensitive method utilizing reversed-phase liquid chromatography with fluorescence detection has been developed for the analysis of the anticoagulant rodenticide brodifacoum in blood serum. The serum proteins are precipitated with acetonitrile and the supernatant mixed with ethyl ether. The organic phase is separated, evaporated to dryness, and the residue subjected to chromatographic analysis. Extraction efficiencies of brodifacoum at concentrations of 20, 60, and 300 ng/mL were 82.9, 93.4, and 93.8%, respectively, with coefficients of variation (CVs) of 3.52, 4.07, and 3.68%, respectively. The intrarun precision (CV) without an internal standard at concentrations of 20, 60, and 300 ng/mL were 1.93, 4.89, and 1.51%, respectively, and 3.56, 5.94, and 3.66% with an internal standard. The interrun precision over the concentration range of 20-1000 ng/mL ranged from 1.88-6.22% without an internal standard and from 2.07-12.6% with an internal standard. Brodifacoum was measurable to at least the 1-ng/mL level.

Characterization of outer membrane protein-enriched extracts from Pasteurella multocida isolated from turkeys

Outer membrane protein (OMP)-enriched extracts of avian strains of Pasteurella multocida were examined by use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Culture medium did not have a significant effect on the OMP profiles of strains of P multocida examined; however, in vivo propagation had an appreciable effect on the OMP profile composition of the reference strain P-1059. Such bacteria, expressed several additional OMP in the 27-kD, 48-kD, 56-kD, 60-kD, 80-kD, and 94-kD molecular mass regions. These OMP were not detected in the electrophorogram of strain P-1059 grown in vitro. The OMP profiles of reference strains of the 16 serotypes of P multocida did not identify any serotype-specific protein markers. Field strains of serotype A:3 had variation in OMP profiles and did not express OMP that all were identical to that expressed by the reference strain P-1059. The live attenuated CU and M9 bacterial vaccine strains expressed strain-specific OMP markers of 48-kD and 45-kD molecular masses, respectively. These strain-specific OMP markers may be used to differentiate these strains from virulent field strains that are of the same serotype and isolated from turkeys that have succumbed to pasteurellosis as a result of vaccine-related reactions or breakdown in immunity.

Relationship of nutritional factors to the cause, dissolution, and prevention of canine uroliths

Nutritional factors play a variable role in the etiopathogenesis of canine struvite, ammonium urate, cysteine, calcium oxalate, and silica uroliths. Knowledge of these factors allows modification of diets to promote dissolution of selected minerals within uroliths.

Optimization of high-performance liquid chromatography-radioimmunoassay protocols for the analyses of substance P and some of its metabolic fragments

A reversed-phase high-performance liquid chromatographic procedure combined with radioimmunoassay (HPLC-RIA) was developed and optimized for the concomitant quantitation of substance P (SP) and some of its C- and N-terminal fragments in the extracts of the spinal cord of mice. A selective and efficient solid-phase extraction protocol was used for preparative purification of sample homogenates prior to analyses. The sensitivity of the HPLC assay was 18.75 ng for SP and some of its fragments of interest. Recoveries of peptides were calculated from spiked aqueous standards carried through the experimental protocol and ranged from 53 to 98%. The precision of the peptide recoveries from aqueous-based standards, expressed as coefficient of variation, ranged from 2 to 28%. The sensitivities for the RIA procedure using SP antiserum were 1.5, 3.4 and 4.6 fmol SP1-11, SP2-11 and SP5-11, respectively. The percentage cross-reactivity of SP1-11 antiserum with the C-terminal fragments was complete whereas the cross-reactivities of the N-terminal fragments were essentially zero. The molar limits of detectability of SP and some of its C-terminal fragments determined by HPLC alone were several orders of magnitude greater than those determined from the same spinal cord samples using RIA after HPLC fractionation.

Toxicity of a vitamin D3 rodenticide to dogs

As a follow-up to an investigation of 2 dogs that died as a result of apparent toxicosis attributable to a cholecalciferol-containing rodenticide, we tested the toxicity of this product in dogs. Two groups of 2 dogs each were fed amounts of rodenticide that provided 20 and 10 mg of cholecalciferol/kg of body weight (approx one fourth and one eighth of the published LD50, respectively). All dogs developed hypercalcemia and hyperphosphatemia and then died. Major lesions were gastrointestinal hemorrhage, myocardial necrosis, and mineralization of vascular walls. Our data indicate that cholecalciferol-containing rodenticides pose a much greater hazard to dogs than was previously believed.

Siderophore production by Pasteurella multocida

Pasteurella multocida grown under conditions of iron deprivation secreted into the culture medium a growth-enhancing factor which functioned as a siderophore. The siderophore was found to be neither a phenolate nor a hydroxamate by chemical tests and bioassays and was given the trivial name multocidin. Multocidin was partially purified and found to be a highly polar, nonaromatic, and dialyzable compound. This is the first report demonstrating the production of a siderophore by P. multocida.

Recent developments in the clinical assessment of the metabolism of aromatics by high-performance, reversed-phase chromatography with amperometric detection

High-performance liquid chromatography with electrochemical detection has developed into a tool with excellent capability to monitor picomole amounts of individual metabolites in both tissue and body-fluid specimens. Significant technical advances in the area of microparticle chemically-bonded stationary phases have led to dramatic improvements in both sensitivity and resolution. Reversed-phase systems can be modified to include charged exchange sites by addition of detergents to the mobile phase. Adjustment of the surface charge in this manner permits capacity factors for ionic sample components to be increased or decreased. This concept is quite compatible with electrochemical detection and has provided the foundation for several clinical assays now in routine use. Examples of additional applications are presented for the determination of catecholamines in tissue, 3-methoxy-4-hydroxyphenylglycol in urine, and dopamine-beta-hydroxylase activity in human serum.

Recent developments in the clinical assessment of the metabolism of aromatics by high-performance, reversed-phase chromatography with amperometric detection

High-performance liquid chromatography with electrochemical detection has developed into a tool with excellent capability to monitor picomole amounts of individual metabolites in both tissue and body-fluid specimens. Significant technical advances in the area of microparticle chemically-bonded stationary phases have led to dramatic improvements in both sensitivity and resolution. Reversed-phase systems can be modified to include charged exchange sites by addition of detergents to the mobile phase. Adjustment of the surface charge in this manner permits capacity factors for ionic sample components to be increased or decreased. This concept is quite compatible with electrochemical detection and has provided the foundation for several clinical assays now in routine use. Examples of additional applications are presented for the determination of catecholamines in tissue, 3-methoxy-4-hydroxyphenylglycol in urine, and dopamine-beta-hydroxylase activity in human serum.

Modification of the Pisano method for vanilmandelic acid using high pressure liquid chromatography

A method for the measurement of urinary vanilmandelic acid (VMA) is described based on a modification of the colorimetric procedure of Pisano. VMA is oxidized to vanillin with subsequent measurement of the vanillin by high pressure liquid chromatography with electrochemical detection (LCEC). The technique has been successfully applied to a number of human and animal urine samples. Urinary VMA values obtained by the LCEC method are in good agreement with those determined by the method of Pisano. The new method is both more selective and more sensitive than the colorimetric procedure.