Effects of continuous venovenous hemofiltration on cardiopulmonary function in a porcine model of endotoxin-induced shock

OBJECTIVE

To determine whether continuous venovenous hemofiltration, proposed to remove inflammatory mediators from circulation, would resolve cardiopulmonary derangements in a model of established endotoxic shock.

ANIMALS

16 clinically normal pigs.

PROCEDURE

Endotoxin was infused, IV, into anesthetized pigs for a total of 50 minutes. Thirty minutes after termination of the infusion period, extracorporeal circulation was initiated through a 50-kd diafilter, or past the filter without ultrafiltrate formation. Cardiac and respiratory variables were monitored for a period of 4 hours.

RESULTS

Infusion of lipopolysaccharide resulted in a severe hypodynamic circulatory state, with significant decreases in mean arterial pressure and cardiac output concurrent with a significant increase in pulmonary arterial pressure. Hemofiltration was not associated with any correction of lipopolysaccharide-induced cardiopulmonary derangements.

CONCLUSIONS

Continuous venovenous hemofiltration, as used in this acute experiment, did not improve cardiopulmonary dysfunction during endotoxic shock.

CLINICAL RELEVANCE

Continuous venovenous hemofiltration needs further investigation before it can be recommended as a clinically effective treatment.

Piroxicam therapy in 34 dogs with transitional cell carcinoma of the urinary bladder

Thirty-four dogs with histopathologically confirmed, measurable, nonresectable transitional cell carcinoma of the urinary bladder were treated with piroxicam (0.3 mg/kg PO sid) and were evaluated for tumor response and drug toxicity. Dogs were evaluated at the Purdue University Veterinary Teaching Hospital by means of physical examination, thoracic and abdominal radiography, cystography, complete blood count, serum biochemistry profile, and urinalysis. In selected cases, prostaglandin E2 (PGE2) concentrations in plasma and in supernatants of stimulated monocytes, and natural killer cell activity were quantified. Dogs were evaluated before therapy and at 28 and 56 days after initiation of therapy. Dogs with stable disease or remission at 56 days remained on the study and were evaluated at 1 to 2 months intervals. Tumor responses were 2 complete remissions, 4 partial remissions, 18 stable diseases, and 10 progressive diseases. The median survival of all dogs was 181 days (range, 28 to 720+ days), with 2 dogs still alive. Piroxicam toxicity consisted of gastrointestinal irritation in 6 dogs and renal papillary necrosis (detected at necropsy) in 2 dogs. Monocyte production of PGE2 appeared to decrease with therapy in dogs whose tumors were decreasing in size, and increased in dogs with tumor progression. A consistent pattern in natural killer cell activity was not observed. In vitro cytotoxicity assays against 4 canine tumor cell lines revealed no direct antitumor effects of piroxicam. In summary, antitumor activity, which was not likely the result of a direct cytotoxic effect, was observed in dogs with transitional cell carcinoma of the bladder treated with piroxicam.

Ultracentrifugal and electrophoretic characteristics of the plasma lipoproteins of miniature schnauzer dogs with idiopathic hyperlipoproteinemia

To better characterize the idiopathic hyperlipoproteinemia of Miniature Schnauzer dogs, the plasma lipoproteins of 20 Miniature Schnauzers (MS) and 11 dogs of other breeds (DOB) were evaluated by ultracentrifugation, electrophoresis, and biochemical tests. Seventeen MS were healthy; 3 had diabetes mellitus. Plasma from 6 of 17 healthy and all 3 diabetic MS was visibly lipemic. Lipemia was slight to marked in healthy lipemic MS, and marked in diabetic ones. All DOB had clear plasma; 8 were healthy and 3 had diabetes. All healthy lipemic MS and diabetic lipemic MS had hypertriglyceridemia associated with excess very low density lipoproteins. Chylomicronemia was present in 4 of 6 healthy lipemic MS and all 3 diabetic lipemic MS. Lipoproteins with ultracentrifugal and electrophoretic characteristics of normal low density lipoprotein were lacking in 4 of 6 healthy lipemic MS. The lipoprotein patterns of 4 of 11 healthy nonlipemic MS were characterized by mild hypertriglyceridemia associated with increased very low density lipoproteins and a lack of lipoproteins with characteristics of normal low density lipoproteins. Lipoprotein patterns of diabetic DOB closely resembled those of healthy DOB; those of diabetic lipemic MS resembled those of markedly lipemic healthy lipemic MS. In conclusion, the hyperlipoproteinemia of Miniature Schnauzers is characterized by increased very low density lipoproteins with or without accompanying chylomicronemia; some affected dogs may have decreased low density lipoproteins.

Serum triiodothyronine, total thyroxine, and free thyroxine concentrations in horses

The objectives of this experiment were to determine serum concentrations of triiodothyronine (T3), thyroxine (T4), and free thyroxine (fT4) at rest, following thyroid-stimulating hormone (TSH) administration, and following phenylbutazone administration in healthy horses. This was done to determine which available laboratory test can best be used for diagnosis of hypothyroid conditions in horses. Serum T3, T4, and fT4 concentrations in serum samples obtained before and after TSH stimulation and following phenylbutazone administration for 7 days were determined. Baseline values ranged from 0.21 to 0.80 ng of T3/ml, 6.2 to 25.1 ng of T4/ml, and 0.07 to 0.47 ng of fT3/dl. After 5 IU of TSH was administered IV, serum T3 values increased to 6 times baseline values in 2 hours. Thyroxine values increased to 3 times baseline values at 4 hours and remained high at 6 hours. Free T4 values increased to 4 times baseline values at 4 hours and remained high at 6 hours. Administration of 4.4 mg of phenylbutazone/kg, every 12 hours for 7 days significantly decreased T4 and fT4 values, but did not significantly affect serum T3 concentrations. It was concluded that a TSH stimulation test should be performed when hypothyroidism is suspected. Measurement of serum fT4 concentrations, by the single-stage radioimmunoassay, does not provide any additional information about thyroid gland function over that gained by measuring T4 concentrations. Phenylbutazone given at a dosage of 4.4 mg/kg every 24 hours, for 7 days did significantly decrease resting T4 and fT4 concentrations, but did not significantly affect T3 concentrations in horses.

The effect of starting time on dexamethasone suppression test results in horses

This study was conducted to investigate the effect of starting time on dexamethasone suppression test results in horses. Eight adult horses were used throughout the trial. Baseline cortisol levels were established by collecting cortisol levels twice daily, at 8:00 A.M. and 8:00 P.M. for 4 consecutive days. Morning baseline cortisol levels were 46.3 +/- 5.94 ng/ml, and evening baseline cortisol levels were 32.8 +/- 5.59 ng/ml. Although lower, the evening cortisol levels were not statistically different (P = 0.154) from the morning levels. Dexamethasone suppression tests initiated at either 9:00 A.M. or 9:00 P.M. were performed by collected a control blood sample, administering either 0.044 mg/kg dexamethasone or its vehicle intravenously and then collecting additional blood samples at 6, 12, 24, 36, and 48 hr after treatment. Mean cortisol levels at hr 0, 6, 12, 24, 36, and 48 after a dexamethasone injection given at 9:00 A.M. were 55.6 +/- 3.08, 6.4 +/- 2.05, 0.73 +/- 0.48, 11.0 +/- 5.82, 12.6 +/- 4.30, and 40.5 +/- 5.38 ng/ml respectively. Mean cortisol levels at hr 0, 6, 12, 24, 36, and 48 hr after a dexamethasone injection given at 9:00 P.M. were 45.0 +/- 6.03, 4.5 +/- 1.28, 0.20 +/- 0.12, 4.5 +/- 2.49, 23.4 +/- 5.88, and 29.5 +/- 6.61 ng/ml respectively. There was no statistical difference in cortisol values between A.M. and P.M. initiated tests at any hour post dexamethasone administration. There was no decrease in cortisol level after administration of dexamethasone vehicle.

Serial thyroid hormone concentrations in healthy euthyroid dogs, dogs with hypothyroidism, and euthyroid dogs with atopic dermatitis

Serum thyroxine (T4) and 3,5,3'-triiodothyronine (T3) concentrations were determined every 3 h for 12 h beginning at 8 a.m. in 20 healthy euthyroid dogs, 19 dogs with hypothyroidism, and 18 euthyroid dogs with atopic dermatitis. Status of thyroid function was based on history, physical findings, results of thyrotropin response testing, and requirement for thyroid hormone replacement therapy. Mean serum T4 and T3 concentrations did not vary significantly between blood samplings within each of the three groups of dogs. Between groups of dogs, mean serum T4 concentration was significantly (P less than 0.05) higher at each blood sampling time in healthy euthyroid dogs and euthyroid dogs with atopic dermatitis when compared to dogs with hypothyroidism. There was no significant difference in mean serum T4 concentration at any blood sampling time between healthy euthyroid dogs and euthyroid dogs with atopic dermatitis or in mean serum T3 concentrations at any blood sampling time between any of the three groups of dogs. Random fluctuation in serum T4 and T3 concentrations was found in dogs in all three groups. Random fluctuations were more common with serum T3 versus T4 concentrations. Consequently, sensitivity (0.88 versus 0.52), specificity (0.73 versus 0.45), predictive value for a positive test (0.75 versus 0.32), predictive value for a negative test (0.87 versus 0.65), and accuracy (0.80 versus 0.47) were better for serum T4 concentration than serum T3 concentration, respectively, when all blood samples were analysed. Measurement of serum T4 concentration was more accurate than serum T3 concentration in assessing the status of thyroid gland function.

Effects of flunixin meglumine on dogs with experimental gastric dilatation-volvulus

Gastric dilatation-volvulus (GDV) was created experimentally and maintained for 90 minutes in 16 anesthetized, mixed-breed dogs. After the GDV was corrected, normal saline solution (0.044 mL/kg intravenously [IV]) was administered to eight dogs (controls), and flunixin meglumine (2.2 mg/kg IV) was administered to eight dogs. Microspheres labeled with radioactive cobalt, scandium, tin, or niobium were injected intravenously at baseline (before GDV) and minutes 90, 100, and 270, respectively, to determine tissue blood flows. Plasma endotoxin and prostacyclin were measured at the same intervals. Electrocardiogram, mean arterial pressure, portal pressure, and cardiac output were recorded continuously. Dogs were euthanatized at minute 270 and necropsied. There was no significant difference between treatment groups for any measured variable at any time. Endotoxin levels increased significantly during GDV. Prostacyclin levels were lower in dogs treated with flunixin meglumine than in controls at minutes 210 and 270. Histopathologic findings were similar for all dogs and consistent with those associated with endotoxemia. Flunixin meglumine treatment did not alter cardiac indices or tissue blood flows significantly. However, elevation of prostacyclin was inhibited by flunixin meglumine, which suggested that continued effects of endotoxic damage might be attenuated or inhibited.

Phase I trial of piroxicam in 62 dogs bearing naturally occurring tumors

Piroxicam, a nonsteroidal antiinflammatory drug, was given to 62 dogs bearing naturally occurring tumors in a phase I clinical trial. Dose escalation was performed, with oral doses ranging from 0.5 mg/kg every 48 h (q48h) to 1.5 mg/kg q48h being tested. Dose-limiting gastrointestinal irritation/ulceration occurred in all four animals that received 1.5 mg/kg q48h. The maximum tolerated dose was 1 mg/kg q48h. Subclinical renal papillary necrosis occurred in two dogs (initial dosages, 1 and 1.5 mg/kg q48h, respectively). Following dose escalation, an additional group of dogs was treated with 0.3 mg/kg piroxicam q24h per os, the accepted canine dosage prior to this trial. Inclusion of this treatment group enabled evaluation of the toxicity of and tumor response to a daily dosage regimen. No complete remissions occurred in this trial. Partial remission was documented in three of ten dogs exhibiting transitional-cell carcinoma, in three of five animals bearing squamous-cell carcinoma, in one of three dogs displaying mammary adenocarcinoma, and in the one dog that exhibited a transmissible venereal tumor. The results of this study support the additional evaluation of piroxicam in a phase II clinical trial in dogs bearing naturally occurring tumors.

Effects of dietary fiber supplementation on glycemic control in dogs with alloxan-induced diabetes mellitus

The effect of a high insoluble-fiber (IF) diet containing 15% cellulose in dry matter, high soluble-fiber (SF) diet containing 15% pectin in dry matter, and low-fiber (LF) diet on glycemic control in 6 dogs with alloxan-induced insulin-dependent diabetes mellitus was evaluated. Each diet contained greater than 50% digestible carbohydrate in dry matter. A crossover study was used with each dog randomly assigned to a predetermined diet sequence. Each dog was fed each diet for 56 days. Caloric intake was adjusted weekly as needed to maintain each dog within 1.5 kg of its body weight measured prior to induction of diabetes mellitus. All dogs were given pork lente insulin and half of their daily caloric intake at 12-hour intervals. Mean (+/- SEM) daily caloric intake was significantly (P less than 0.05) less when dogs consumed the IF diet vs the SF and LF diets (66 +/- 3 kcal/kg, 81 +/- 5 kcal/kg, and 79 +/- 4 kcal/kg, respectively). Serum alkaline phosphatase activity was significantly (P less than 0.05) higher when dogs consumed the LF diet vs the IF and SF diets (182 +/- 37 IU/L, 131 +/- 24 IU/L, and 143 +/- 24 IU/L, respectively). Mean postprandial plasma glucose concentration measured every 2 hours for 24 hours, beginning at the time of the morning insulin injection, was significantly (P less than 0.05) lower at most blood sampling times in dogs fed IF and SF diets, compared with dogs fed the LF diet.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of dietary n-3 and n-6 fatty acids on tumor necrosis factor-alpha production and leucine aminopeptidase levels in rat peritoneal macrophages

The purpose of this study was to determine the effect of dietary n-3 and n-6 fatty acids on tumor necrosis factor-alpha (TNF-alpha) production and macrophage (MO) activation state. Rats were fed diets containing 12.5% linseed oil (LO) or corn oil (CO) that are high in n-3 and n-6 fatty acids respectively. The LO diet resulted in a significant increase in basal and endotoxin (LPS)-induced levels of TNF-alpha from resident MO cultured in vitro. There was no difference between the diets in LPS-induced TNF-alpha production by complete Freund's adjuvant (CFA) elicited macrophages. Variable responses were also observed between LO and CO MO in response to prostaglandin E2, indomethacin (INDO), and the prostaglandin E receptor antagonist SC-19220. This may indicate differences in signal transducing secondary messengers due to different activation states, receptor expression or ligand binding. Fluorescence due to leucine aminopeptidase (LAP) staining was determined by flow cytometry. Resident LO MO had a 15% increase in LAP fluorescence compared to CO MO. In CFA-elicited MO, the CO MO had a 43% increase in fluorescence compared to LO MO. Resident LO MO increased in LAP fluorescence by 35% to the activated state whereas resident CO MO increased in LAP fluorescence by 93%. The smaller window of activation for the LO MO may explain some of the antiinflammatory properties of dietary n-3 fatty acids.

Serum glucose and insulin responses to an insulin-containing ophthalmic solution administered topically in clinically normal cats

Serum glucose and immunoreactive insulin concentrations were monitored after topical administration of an insulin-containing ophthalmic solution in 20 clinically normal cats. Three ophthalmic surface-acting agents, benzalkonium chloride, dimethyl sulfoxide, and proparacaine hydrochloride, were evaluated individually for their effectiveness in enhancing absorption of topically applied insulin. The ophthalmic effects of insulin-containing ophthalmic preparations were assessed by complete ophthalmic examination before and at the conclusion of each test period. Withholding of food overnight (12 hours) preceded each topical application of insulin-containing ophthalmic solution (12.25 to 26.4 U/cat), either alone or in combination with surface-acting agents, after which blood samples were drawn serially from an indwelling IV catheter over a period of 8 hours. Baseline serum insulin concentration, after food was withheld for 12 hours, in nonstressed cats was 6.0 microU/ml (geometric mean), and an exponentiation of the logarithmic quantity (mean +/- SD) yielded values of 1.5 to 23.0 microU/ml. All ophthalmic solutions tested failed to significantly lower serum glucose concentration or increase serum insulin concentration. Solutions used did not induce deleterious effect on ocular structures. Results indicate that topical administration of insulin-containing ophthalmic solution, either alone at the concentrations used or in combination with surface-acting agents, did not result in effective absorption of insulin across the conjunctival and lacrimal nasal mucosa in biologically relevant quantities. Thus, this route of insulin administration, under these specific conditions, is not an effective alternative or adjunct to SC administration of insulin for treatment of cats with insulin-dependent diabetes mellitus or severe noninsulin-dependent diabetes mellitus.

The effects of soman poisoning in combination with hypovolemic shock

Hemorrhage is a cause of death in both combat and civilian injuries. The specific objectives of this research were: (1) to determine the pathophysiologic effects of combined injuries from sublethal amounts of an organophosphate (soman) along with hypovolemic shock, and (2) to determine the efficacy of atropine sulfate and pralidoxime (2-PAM) therapy for organophosphate poisoning when combined injuries occur. Four groups of six beagle dogs/group were used: Group V/H, vehicle administration followed by hemorrhage; Group S/H, soman administration followed by hemorrhage; Group S/A/H, soman followed by antidote (atropine and 2-PAM) and then hemorrhage; and Group S, soman only. Acetylcholinesterase (AChE) activity, hemodynamic parameters, regional blood flow, plasma enzyme, and hematological changes were monitored. Soman rapidly decreased AChE activity in RBCs, plasma, and brain tissue. Treatment with atropine and 2-PAM resulted in only slight reactivation of AChE; they helped maintain blood gases, cortisol, plasma enzymes, inspiratory volume, and blood pressure nearer baseline values. The effects of combined injuries appear to be greater than those of either injury alone. This was indicated by increased plasma lactate, plasma enzymes indicative of tissue damage (aspartate amine transferase and creatine kinase), and increased lethality in dogs subjected to both soman and hemorrhage (5/12 died). All dogs subjected to only one insult survived the 6-hr experiment.

Serum free thyroxine concentration in healthy dogs, dogs with hypothyroidism, and euthyroid dogs with concurrent illness

Serum free thyroxine (fT4), thyroxine (T4), and 3,5,3'-triiodothyronine (T3) concentrations were determined in 62 healthy dogs, 51 dogs with hypothyroidism, and 59 euthyroid dogs with concurrent dermatopathy or concurrent illness for which hypothyroidism was a diagnostic consideration. Status of thyroid function was based on history, physical findings, results of thyrotropin response testing, requirement for thyroid hormone replacement therapy, and in 31 dogs, on results of histologic examination of a thyroid gland biopsy specimen. Serum fT4 concentration was determined, using a single-stage radioimmunoassay. Mean (+/- SD) serum fT4 concentration was significantly (P less than 0.05) greater in healthy dogs vs dogs with hypothyroidism (0.51 +/- 0.27 ng/dl vs 0.10 +/- 0.07 ng/dl). Significant difference in mean serum fT4 concentration was not evident between dogs with hypothyroidism and euthyroid dogs with hyperadrenocorticism (0.16 +/- 0.13 ng/dl) or peripheral neuropathy (0.19 +/- 0.10 ng/dl). Mean serum fT4 concentration in all other groups of euthyroid dogs with concurrent illness was similar to values in healthy dogs and was significantly (P less than 0.05) greater, compared with values in dogs with hypothyroidism. Similar results were found for mean serum T4 concentration. Comparison of serum fT4 vs T4 concentration revealed: sensitivity, 0.97 vs 0.98; specificity, 0.78 vs 0.73; predictive value for a positive test result, 0.79 vs 0.80; predictive value for a negative test result, 0.97 vs 0.97; and accuracy, 0.78 vs 0.86, respectively. Ten (17%) and 12 (20%) of 59 serum fT4 and T4 concentrations, respectively, were inappropriately low in euthyroid dogs with concurrent illness.(ABSTRACT TRUNCATED AT 250 WORDS)

Leukotriene C4 disposition and metabolism in the anesthetized and endotoxemic dog

The metabolism and disposition of tritiated leukotriene C4, [3H]-LTC4, were studied in control dogs and endotoxin-treated dogs. Radioactivity was monitored in plasma, bile, and urine for 4.5 hr after an IV bolus of [3H]-LTC4. A decreased recovery of radioactivity in bile and urine was observed in the endotoxin-treated dogs. Cumulative [3H]-LTC4 metabolic patterns in bile and urine were determined by reverse-phase high-performance liquid chromatography (RP-HPLC) separation. Three primary metabolites, [3H]-LTD4, [3H]-LTE4, and a polar metabolite, (0.15-0.19)LT, accounted for most of the total bile radioactivity. The same primary metabolites were found for endotoxin-treated dogs and in similar relative amounts. [3H]-LTE4 and the polar metabolite (0.15-0.21)LT were the primary metabolites found in urine, but no N-acetyl LTE4 was found in bile or urine for either group. Plasma incubation of [3H]-LTC4 revealed heat-sensitive dipeptidase and glutamyl transpeptidase activity with significant production of [3H]-LTD4 and [3H]-LTE4 after 5- and 30-min incubation. Pharmacokinetic analysis using the two-compartment open model revealed an increased distribution phase rate constant (alpha) and distribution phase half-life [t1/2(alpha)], and decreased clearance (ClB), volume of distribution [Vd(ss) and Vd(area)] and elimination rate microconstant (Kel) of tritiated leukotrienes for endotoxin-treated dogs. This analysis along with the maintained higher plasma levels of tritiated leukotrienes, [3H]-LTs, in endotoxin-treated dogs suggests that endotoxin caused a decreased body clearance and less peripheral tissue penetration of [3H]-LTs. Collectively, these results indicate that the metabolism of LTC4 to LTD4 and LTE4, but not N-acetyl LTE4, in dogs was similar to that reported for man, pig, and monkey but dissimilar to rat. Endotoxin did not affect the types or relative amounts of metabolites found in bile or urine but appears to affect the disposition of [3H]-LTs by decreasing clearance and distribution.

Plasma concentrations of endotoxin following jugular or portal injections of endotoxin and following gastrointestinal ischemia due to hemorrhage

Endotoxin (LPS) was quantitated in canine plasma using the Limulus amebocyte lysate (LAL) chromogenic testing procedure. The assay was validated for sensitivity (25 pg/ml), recovery (90-110%), intra-assay precision (CV = 5.5), interassay precision (CV = 10), and stability of diluted, heat-treated, frozen samples (greater than or equal to 60 days). Canine plasma samples were analyzed for endotoxin following sublethal IV injections (cephalic and portal, bolus and slow infusion) of LPS. Pharmacokinetic analysis using the two-compartment open model on plasma LPS levels was possible for portal bolus, cephalic bolus, and portal slow infusion dogs. The results revealed that LPS given via cephalic bolus route had a lower clearance rate than LPS given via portal bolus route. Slow infusion of LPS into the portal vein revealed an increased distribution phase t1/2 in plasma and a slower elimination kel and beta rate than observed following a portal bolus injection of LPS. During a clinical endo(to)xemia, LPS enters the circulation slowly, and is therefore probably cleared more slowly; the prolonged low level of LPS may be responsible for many pathophysiological changes observed. Low levels of endotoxin were detected in plasma following hemorrhage, indicating that intestinal ischemia results in low levels of LPS leaking into the circulation.

Effects of acute alcohol intake on tolerance to hypotension

The specific aim of this research was to test the hypothesis that intoxication with alcohol results in poor tolerance to hemorrhage. This was evaluated on the basis of blood pressure, cardiac output respiratory rate, blood flow to organs, and survival for 4 hr after hemorrhage. Four groups of six swine per group were used (control, intoxicated, hemorrhage, and intoxicated-hemorrhage). The results revealed that blood alcohol concentrations near 0.1% greatly reduced tolerance to hemorrhage. Intoxicated animals subjected to hemorrhage were unable to maintain an adequate cardiac output, blood pressure, or respiratory rate to sustain life. Pigs tolerated higher blood alcohol concentrations, up to 0.35%, when not exposed to hemorrhage. Also, unintoxicated pigs were able to compensate for severe hemorrhage. Only one of the six pigs in the intoxicated-hemorrhage group survived for 4 hr after hemorrhage. In conclusion the body's ability to compensate and recover from hemorrhage was greatly reduced during intoxication. It is logical to assume that the ability to overcome numerous other stressors may also be reduced during intoxication.

Absorption kinetics of regular insulin in dogs with alloxan-induced diabetes mellitus

The absorption kinetics of porcine regular insulin following IV, IM, and SC administration were evaluated in 10 dogs with alloxan-induced diabetes mellitus. Plasma immunoreactive insulin (IRI) concentrations were evaluated immediately prior to and at 10, 20, 30, 45, 60, 90, 120, 180, and 240 minutes following IV administration; and immediately prior to and every 30 minutes for 2 hours and then every hour for 6 hours following IM and SC administration of 0.55 U of porcine regular insulin/kg of body weight. Model-independent pharmacokinetic analysis was performed on each data set. Plasma IRI concentration declined rapidly after IV administration of regular insulin and then returned to baseline IRI concentration by 3.2 +/- 0.8 hours. The absorption kinetics following IV administration of regular insulin were similar to those found in earlier studies in healthy dogs and human beings. The IM and SC routes of regular insulin administration resulted in a pharmacologic concentration of IRI at 30 minutes. The peak mean (+/- SD) plasma IRI concentration was significantly (P less than 0.05) greater following SC administration than it was following IM administration of regular insulin (263 +/- 185 and 151 +/- 71 I microU/ml, respectively). The time of the peak plasma IRI concentration (68 +/- 31 minutes and 60 +/- 30 minutes) and the time to return to baseline plasma IRI concentration (5.8 +/- 1.2 hours and 5.8 +/- 1.3 hours) were not significantly different following SC and IM administration of regular insulin, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Glucose tolerance and insulin response in normal-weight and obese cats

Glucose tolerance and insulin response were evaluated in 9 normal-weight and 6 obese cats after IV administration of 0.5 g of glucose/kg of body weight. Blood samples for glucose and insulin determinations were collected immediately prior to and 2.5, 5, 7.5, 10, 15, 30, 45, 60, 90, and 120 minutes after glucose infusion. Baseline glucose concentrations were not significantly different between normal-weight and obese cats; however, mean +/- SEM glucose tolerance was significantly impaired in obese vs normal-weight cats after glucose infusion (half time for glucose disappearance in serum--77 +/- 7 vs 51 +/- 4 minutes, P less than 0.01; glucose disappearance coefficient--0.95 +/- 0.10 vs 1.44 +/- 0.10%/min, P less than 0.01; insulinogenic index--0.20 +/- 0.02 vs 0.12 +/- 0.01, P less than 0.005, respectively). Baseline serum insulin concentrations were not significantly different between obese and normal-weight cats. Insulin peak response after glucose infusion was significantly (P less than 0.005) greater in obese than in normal-weight cats. Insulin secretion during the first 60 minutes (P less than 0.02), second 60 minutes (P less than 0.001), and total 120 minutes (P less than 0.0003) after glucose infusion was also significantly greater in obese than in normal-weight cats. Most insulin was secreted during the first hour after glucose infusion in normal-weight cats and during the second hour in obese cats. The impaired glucose tolerance and altered insulin response to glucose infusion in the obese cats was believed to be attributable to deleterious effects of obesity on insulin action and beta-cell responsiveness to stimuli (ie, glucose).

Effects of multiple dose infections with Ascaris suum on blood gastrointestinal hormone levels in pigs

Ten consecutive daily doses of infective Ascaris suum eggs were administered to pigs in two experiments and the levels of gastrointestinal hormones in their blood were measured. The piglets in each experiment were divided into low-dose (LDI) and high-dose (HDI) infections and control groups. Infected pigs had lower feed consumption, lower weight gains, and lower feed efficiency than control pigs. Serum gastrin levels in infected pigs were significantly lower than the controls from Days 7 to 17 post first inoculation (PFI), and so were their serum glucagon levels from Days 12 to 24 PFI. Serum insulin levels in infected animals were sometimes lower than those in controls. These differences were usually more intense in the LDI pigs than in HDI pigs. The plasma cholecystokinin (CCK) levels in the LDI group were significantly higher than those in controls from Day 10 PFI to the end of the experiment, while the CCK levels in the HDI group did not differ significantly from the controls. Increased plasma CCK levels could be a satiety factor in A. suum infection since the time of occurrence of high levels of CCK matched the period of reduced feed consumption.

Characterization of release of tumor necrosis factor, interleukin-1, and superoxide anion from equine white blood cells in response to endotoxin

Direct effects of endotoxin (lipopolysaccharide [LPS]) on equine WBC are known to stimulate the release of a variety of mediators including thromboxane, prostacyclin, and leukotrienes. In this study, 0.1 microgram of LPS/ml stimulated an early increase in tumor necrosis factor, succeeded by an increase in interleukin-1, but concentrations of LPS up to 5.0 micrograms/ml caused no significant increase in superoxide anion release. The concentration of LPS (0.1 microgram/ml) used in this experiment was in the range of concentrations measured in plasma of some horses with gastrointestinal problems. These results indicate that mediators released in response to low concentrations of LPS may be responsible for many of the LPS-induced pathophysiologic effects. This is indicated because concentrations of LPS detected in plasma of some horses with severe gastrointestinal problems are approximately 0.1 microgram/ml, a concentration that will stimulate cells to produce tumor necrosis factor, but will not stimulate any other measurable cytotoxic effect.

Serum levels of gastrin, insulin and glucagon as possible factors of anorexia in pigs infected once with Ascaris suum

In order to determine possible mediators for development of anorexia in pigs infected with Ascaris suum, serum levels of gastrin, insulin and glucagon were measured. After a single high oral dose of 100,000-200,000 embryonated eggs the serum levels of gastrin and insulin in the infected pigs did not significantly differ from those in controls. Serum glucagon levels in the infected groups, however, were lower than those in controls and the difference was more evident 24 days postinoculation and later.

Serum disposition of exogenous progesterone after intramuscular administration in bitches

Progesterone was administered IM to 6 adult anestrous bitches at a dosage of 2 mg/kg of body weight. Serum progesterone concentrations were measured prior to progesterone administration and for 72 hours thereafter. The serum progesterone concentration time data were analyzed by use of a pharmacokinetics modeling computer program. The mean (+/- SD) peak serum progesterone concentration (34.3 +/- 7.8 ng/ml) was reached at 1.8 +/- 0.2 hours after progesterone administration. The mean serum progesterone concentration was 6.9 +/- 1.4 ng/ml at 24 hours and 2.0 +/- 0.4 ng/ml at 48 hours after progesterone administration. By 72 hours after administration, mean serum progesterone concentration was 0.9 +/- 0.2 ng/ml, which was comparable to serum progesterone concentrations prior to injection. The mean half-life of the absorption phase was 0.5 hours (range, 0.3 to 0.7 hours). The mean half-life of elimination was 12.1 hours (range, 9.5 to 13.8 hours). By analysis of the data, it was established that a dosage of 3 mg/kg, when the hormone was given IM to dogs once a day, would maintain serum progesterone concentration greater than 10 ng/ml.

Tumor necrosis factor-like cytotoxicity and anorexia in Ascaris suum infected pigs

Tumor Necrosis Factor-Like Cytotoxicity (TNF-LC) was examined in sera from 12 pigs experimentally infected with Ascaris suum. The difference of TNF-LC levels between eight infected and four uninfected controls was not significant. When an endotoxin challenge was intravenously administered 1 month after the first dose of A. suum, the levels of TNF-LC in the sera of infected pigs were one-third that of the controls 125 min post-challenge (PC). In a more detailed study on four infected and two uninfected control pigs, TNF-LC was monitored every 10-15 min until 125 min after endotoxin challenge. The TNF-LC levels in these pigs increased at 40 min PC, reached maximum in another 10-25 min and then decreased. This pattern was seen in all except one infected pig. The infected pigs showed milder shock symptoms and their serum TNF-LC levels returned to pre-challenge levels 30 min earlier than controls.

Effect of dry, soft moist, and canned dog foods on postprandial blood glucose and insulin concentrations in healthy dogs

The effect of dry, soft moist, and canned dog foods on immediate postprandial plasma glucose and insulin concentrations was evaluated in clinically normal dogs. Dogs were fed either dry (10 dogs; group I), soft moist (10 dogs; group II), or canned (8 dogs; group III) dog food for 5 consecutive days. On the fifth day, plasma glucose and insulin concentrations were determined in each dog prior to, during, and at 5, 10, 15, 30, 45, 60, 90, 120, 180, and 240 minutes after ingestion of the food. The alterations in plasma glucose concentrations were not significantly different from prefeeding values until 240 and 180 minutes after feeding for groups I and III, respectively. In contrast, the increments in plasma glucose were significantly (P less than 0.01) increased from basal concentrations at 30 and 45 minutes after feeding in group-II dogs. The maximal mean postprandial plasma glucose concentration was significantly (P less than 0.0001) less for group III, compared with concentrations for groups I and II, but there was no significant difference between concentrations for groups I and II. Although a biphasic insulin secretory response was found in all 3 groups of dogs, the patterns of phase-2 insulin secretion and the total amount of insulin secreted during the study were significantly different. There was a rapid increase in the plasma insulin concentration immediately after phase 1 in group II, with maximal plasma insulin concentrations occurring 30 minutes after feeding, followed by a gradual decrease in concentrations throughout the remainder of the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma endotoxin concentrations in experimental and clinical equine subjects

Endotoxin (LPS) was quantitated in experimental subjects and in horses with naturally occurring gastrointestinal strangulation obstruction and/or septicaemic diseases to establish the fate of LPS and the clinical usefulness of the Limulus amoebocyte lysate (LAL) assay. The assay was validated for sensitivity (10 pg/ml), recovery (90 to 106 per cent), intra-assay precision (CV = 5.5 per cent) inter-assay precision (CV = 11 per cent), and stability of diluted, heat treated, frozen samples (at least 90 days). Plasma concentrations of LPS after sublethal (3 micrograms/kg) jugular or portal vein bolus injections of LPS rose to 4000 pg/ml and 1500 pg/ml respectively followed by a rapid phase of clearance. Peak plasma concentrations of LPS, associated with slow portal infusion, were lower than peak values associated with bolus injections, remained elevated during the infusion (2 h), but rapidly decreased after infusion was stopped. Thirty seven horses with 38 episodes of naturally occurring gastrointestinal or septicaemic disease were assayed for LPS. Eight episodes involving gastrointestinal disease and eight involving septicaemic disease were positive for LPS. It is concluded that the LAL assay is sensitive and reliable for detecting LPS in equine plasma and it may have clinical value for establishing the severity of endotoxaemia or for distinguishing between septic and non-septic conditions. Problems of rapid clearance of LPS from plasma, low concentrations, the possibility of sample contamination, and the time and method of sample procurement remain to be addressed.

Transsphenoidal hypophysectomy in the clinically normal dog

Pituitary function and short-term clinical effects after transsphenoidal hypophysectomy were investigated in clinically normal dogs. In study I, 8 dogs were given polyionic fluids IV during the first 12 hours after surgery. In study II, 4 dogs were given polyionic fluids IV and glucocorticoid supplementation for 7 days. Pituitary function was assessed by evaluating basal ACTH concentrations and results of a growth hormone stimulation test before and 1 and 12 weeks after hypophysectomy, an ACTH stimulation test, a thyrotropin-releasing hormone-stimulation test, and a modified water deprivation/vasopressin response test before and 1, 4, 8, and 12 weeks after hypophysectomy. Gross and histologic evaluations of the surgery site, thyroid and adrenal glands, and skin were done at 12 weeks after surgery. Four dogs from study I died within 27 hours after hypophysectomy. Postmortem examinations of these dogs revealed liver and lung congestion compatible with circulatory collapse. None of the dogs in study II died. For the surviving dogs in both studies, diabetes insipidus developed immediately after hypophysectomy and resolved within 2 weeks. Hypernatremia also developed immediately after hypophysectomy and resolved by 1 week. Production of ACTH was evident at 1 and 12 weeks after hypophysectomy in all dogs, and results of ACTH stimulation tests after surgery were not notably different from results obtained before surgery. Results of thyrotropin-releasing hormone stimulation and growth hormone-stimulation tests supported the diagnosis of hypothyroidism and hyposomatotropism attributable to hypophysectomy. Histologic examination revealed thyroid atrophy, epidermal and dermal atrophy, and normal adrenal glands in all dogs and remnants of the hypophysis in 2 dogs from study I.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of flunixin meglumine in dogs following experimentally induced endotoxemia

Twelve dogs were randomly divided into three groups. Group 1 dogs were given Escherichia coli endotoxin and then treated with flunixin meglumine. Group 2 dogs were given endotoxin as group 1, but untreated. Group 3 dogs were given flunixin meglumine alone. The dogs were monitored clinically and urine and serum samples were collected at regular intervals for 72 hours. All surviving dogs were humanely killed after 72 hours and examined for gross and histologic lesions. Group 1 dogs all survived 72 hours, but showed prerenal azotemia, hepatocellular damage, hemorrhagic enteritis, and numerous gastric ulcerations. Three of the four dogs in group 2 died before 72 hours. Group 2 dogs showed many of the same chemical and hemodynamic changes as group 1. They had severe hemorrhage into the intestinal lumen; however, there were no gastric ulcerations. Group 3 dogs all survived and showed little physical or hematologic change. The study suggested the following: 1) flunixin meglumine was an effective drug in ameliorating the fatal effects of canine endotoxemia, 2) the effects of endotoxin in combination with flunixin meglumine, at 1.1 mg/kg body weight, caused gastric ulcerations, and 3) in normal dogs flunixin meglumine at 1.1 mg/kg body weight did not cause severe side effects or gross lesions.

Hemodynamics, plasma eicosanoid concentrations, and plasma biochemical changes in calves given multiple injections of Escherichia coli endotoxin

Twelve male neonatal calves (39 to 50 kg) were allotted to 3 groups of 4 calves each. All calves were anesthetized with halothane, and then Escherichia coli endotoxin was given intravenously (3 times) and intraperitoneally (3 times) during a 6-hour period. Group-1 calves were untreated, group-2 calves were pretreated with a low dose of flunixin meglumine (1.1 mg/kg of body weight), and group-3 calves were pretreated with a high dose of flunixin meglumine (4.4 mg/kg). In calves of group 1, the mean systemic arterial blood pressure (MABP) and cardiac output (CO) decreased, but pulmonary arterial pressure increased after the initial intravenous and intraperitoneal injections of endotoxin. In calves of this group, these changes were accompanied by increased plasma thromboxane B2 (TxB2) concentration. During this period, increased plasma TxB2 concentration or hemodynamic changes were not detected in calves of groups 2 and 3. Only calves of group 1 had altered hemodynamics early in the experiment; however, after 6 hours, calves of all 3 groups had similarly decreased CO and MABP. In calves of the untreated group, plasma 6-keto-prostaglandin (PG)F1 alpha concentration increased steadily from the beginning of the experiment until 3 hours later. The CO and MABP were low at the time when serum 6-keto-PGF1 alpha concentration was high; however, these 2 measurements also were low in treated calves who did not have correspondingly high plasma 6-keto-PGF1 alpha concentration. Regional blood flow analysis did not reveal correlations between prostanoid concentrations and altered blood flow to selected tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth-stimulating substances in porcine milk

Colostral and milk samples were collected from 6 primiparous sows on postpartum days 0, 9, 18, and 27. Insulin content was measured and epidermal growth factor (EGF) concentration was determined by use of radioimmunoassay and radioreceptor assay, respectively. Total milk protein concentration was measured colorimetrically. Concentrations of insulin, EGF, and protein in the colostral samples were significantly (P less than 0.01) higher than those found in the milk. Milk samples obtained from postpartum days 9, 18, and 27 did not differ significantly in insulin, EGF, or total protein content.

Ultrastructure of equine endothelial cells exposed to endotoxin and flunixin meglumine and equine neutrophils

An in vitro system of cultured equine endothelial cells was evaluated as a model for endotoxin (ET) exposure in the horse. Primary cell lines from pulmonary vessels and aortas were cultured from tissues of 6 horses. Effects of ET alone with and without serum and in combination with the cyclo-oxygenase inhibitor flunixin meglumine and isolated equine neutrophils were evaluated by transmission electron microscopy. Cells plus serum were incubated with 10, 25, 50, or 100 micrograms of ET/ml of incubation medium for 1, 3, 8, or 24 hours. Cells without serum were cultured for 1 and 3 hours. Flunixin meglumine was used at a concentration of 20 micrograms/ml. Cells also were incubated in the presence of 1,000, 5,000, or 20,000 neutrophils/ml plus ET and in the presence of a combination of ET and flunixin meglumine for 1 or 3 hours. Endotoxin alone did not cause cell damage, and the only evidence of an effect was an increased number of secondary lysosomes at incubation hour 8. At incubation hour 24, cells appeared normal. Endotoxin plus neutrophils caused cells to become round and detach from the growth substrate. Cell pathologic changes included swollen and distorted mitochondria and cytoplasmic vacuolization. Response to the ET plus neutrophil combination was variable and ranged from 5% to 50% of the cells being affected. The variability appeared to have some correlation with cell age, as well as individual preparation of neutrophils.

Equine endotoxemia: cardiovascular, eicosanoid, hematologic, blood chemical, and plasma enzyme alterations

Ponies with electromagnetic blood flow transducers implanted around the main pulmonary and left main coronary arteries, were used to evaluate effects of chronic sublethal endotoxin on cardiac output (CO), stroke volume, and left coronary blood flow (LCBF). Plasma thromboxane (TX), as indicated by TXB2, prostacyclin as indicated by 6-keto-prostaglandin (PG) F1 alpha, and hematologic and blood chemical values also were evaluated. Over 24 hours, 2 groups of ponies were given progressively increasing IV and intraperitoneal doses of Escherichia coli lipopolysaccharide (LPS) at 0, 6, 12, and 18 hours. Group 1 was not treated and group 2 was treated with flunixin meglumine, before each LPS insult. Initial LPS inoculation in group 1 led to 10-fold increases in TXB2 and 6-keto-PGF1 alpha values by 30 and 90 minutes, respectively. These eicosanoid values returned to base line by 6 hours after each insult. Although repeated LPS injections stimulated recurring high plasma concentrations of 6-keto-PGF1 alpha, TXB2 production became less with each successive LPS insult. Cardiac output decreased to 55% to 60% of base-line values in association with increased 6-keto-PGF1 alpha values. Left coronary blood flow could not be evaluated accurately. Severe lactic acidosis developed in group 1. Group-2 ponies remained clinically normal, indicating protection of cardiovascular function and peripheral perfusion with flunixin meglumine. Seemingly, flunixin meglumine helped to maintain acceptable cardiovascular function and tissue perfusion during endotoxemia. Flunixin meglumine given to healthy ponies had no effect on cardiovascular function.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro calibration and surgical implantation of electromagnetic blood flow transducers for measurement of left coronary blood flow and cardiac output in the pony

Electromagnetic flow transducers were implanted via left thoracotomy in 8 ponies (122.7 to 263.6 kg) around the main pulmonary and left main coronary arteries for continuous measurement of mean and pulsatile blood flow. Flow transducers were calibrated in vitro with a gravity flow system. The mean +/- SE pulmonary flow was 73.1 +/- 5.1 ml/kg of body weight/min. Left coronary flow was 0.95 +/- 0.07 ml/kg/min (1.3% of cardiac output) and was not believed to be an accurate measurement. This was caused by the inability to implant a zero-flow occluder, requiring the use of minimum flow during systole as zero-flow base line. However, relative changes in left coronary flow were measured. Ponies were maintained up to 5 weeks with no adverse effects. Measurement of mean pulmonary flow with chronically implanted electromagnetic flow transducers provided an accurate continuous measurement of cardiac output with a minimum of restraint.

Effect of thyrotropin storage on thyroid-stimulating hormone response testing in normal dogs

The stability of reconstituted, refrigerated thyrotropin was evaluated. Thyrotropin (TSH) was reconstituted at the start of the study and stored at 4 degrees C. A TSH stimulation test was performed in eight healthy, euthyroid dogs at weekly intervals for 1 month. In seven of eight dogs, there was no significant difference (P less than 0.05) between the post-TSH T3 concentrations and the post-TSH T4 concentrations for the duration of the study. For one dog, the post-TSH T4 concentration was below the normal post-TSH T4 range following the administration of reconstituted TSH that had been stored 4 weeks. The T3 response to the TSH, however, was normal. This dog responded normally to freshly reconstituted TSH. The results of this study suggest that reconstituted bovine TSH can be stored at 4 degrees C for at least 3 weeks without loss of biologic activity in the dog.

Models for the pharmacokinetics and pharmacodynamics of insulin in alloxan-induced diabetic dogs

A combined pharmacokinetic/pharmacodynamic model was proposed to describe the pharmacokinetics of intravenously administered regular insulin (0.55 units/kg) in alloxan-induced diabetic dogs. Serum insulin concentrations were described by either a one- or two-compartment open model, in which a hypothetical effect compartment was linked to the central pharmacokinetic compartment, or in which the effect compartment was linked to the peripheral compartment. Response, as measured by percent change in glucose concentration from adjusted basal plasma concentrations, was modeled using the sigmoidal Emax effect model, a linear effects model, a log-linear effects model, and a gamma-linear effects model, using the insulin pharmacokinetic parameters to describe the amount in the hypothetical effect compartment. The results indicated that insulin pharmacokinetics are usually described by a two-compartment open model. Response to insulin was predicted more accurately in half of the dogs using the gamma-linear effects model in which the effect compartment was linked to the central compartment. In the other half of the dogs the best model was the sigmoidal Emax model in which the effect compartment was linked to the central pharmacokinetic compartment. The parameters in the latter model were correlated with each other and the confidence limits of the parameter estimates were larger than the parameters of the gamma-linear effects model. These models should be further investigated, but may offer an alternative method for distinguishing rapid insulin metabolism from insulin resistance.

The efficacy of dexamethasone and flunixin meglumine in treating endotoxin-induced changes in calves

Eicosanoids have been implicated in the pathophysiology of endotoxic shock. Drugs which alter eicosanoid production such as corticosteroids and non-steroidal anti-inflammatory drugs (NSAID) are beneficial in treating endotoxic shock. Experiments were conducted to investigate the efficacy of dexamethasone, a corticosteroid, and/or flunixin meglumine, a NSAID, in treating endotoxin-induced changes in calves. Fourteen male calves were assigned to one of four treatment groups: group 1, endotoxin-untreated; group 2, endotoxin-flunixin meglumine treated; group 3, endotoxin-dexamethasone-treated; group 4, endotoxin-flunixin meglumine and dexamethasone-treated. Each calf was given three intravenous and intraperitoneal injections of E. coli endotoxin. Hemodynamic, blood gas, blood chemical and eicosanoid level determinations were obtained. Thirty minutes after endotoxin injection, pulmonary artery pressure (PAP) increased and cardiac output (CO) decreased compared with baseline, corresponding to increased thromboxaneB2 levels in groups 1 and 3. These groups exhibited a decreased mean arterial pressure (MAP) at three and five hours corresponding to increased 6-keto-prostaglandinF1 alpha. The MAP, PAP and CO of group 4 remained near baseline for the entire six hours, except for a late drop in MAP. Lactic acid levels were significantly increased and arterial bicarbonate levels were reduced by six hours in all groups except for group 4. These results indicate that the combination treatment of flunixin meglumine and dexamethasone prevents many of the metabolic derangements observed during endotoxic shock in calves.

Endotoxin-induced changes in plasma concentrations of thromboxane and prostacyclin in neonatal calves given antiserum to a mutant Escherichia coli (J-5)

Plasma concentrations of the stable hydrolysis products of thromboxane (Tx) A2, TxB2, and prostacyclin (6-keto-prostaglandin F1 alpha; PGF1 alpha) were evaluated in 22 neonatal calves given endotoxin (0.5 microgram/kg) by slow IV infusion over a 5-hour period. The effect of pretreatment with bovine antiserum to a mutant of Escherichia coli O111:B4 (J-5) on plasma concentrations of these eicosanoids was determined. Plasma concentrations of TxB2 and 6-keto-PGF1 alpha were increased in response to endotoxin infusion. The mean plasma concentrations of TxB2 peaked 1 hour after endotoxin infusion began and was significantly increased from base line through 8 hours. Mean plasma 6-keto-PGF1 alpha concentration increased more slowly and was increased from base line only at 2 hours after endotoxin infusion began. Administration of bovine J-5 antiserum had no significant effect on endotoxin-induced thromboxane and prostacyclin production.

Equine endothelial cells in vitro

Certain in vitro culture conditions were determined for equine endothelial cells obtained from the aorta and pulmonary arteries. Cells were enzymatically isolated from the vessel lumen, using clostridial collagenase (2.5 mg/ml of Hanks's balanced salt solution) incubated at 37 C for 30 minutes. Cells were cultured in alpha minimum essential medium supplemented with plasma-derived and nonplasma-derived bovine fetal sera, endothelial cell-growth supplement, heparin, and antibiotics. Smooth muscle cell growth was not inhibited with nonplasma-derived animal sera, plasma-derived equine serum, or heparin. Heparin and a serum replacement were toxic to the cells used in the present study. Statistically significant differences were not found between the various media supplements.

Effects of multiple intramuscular injections and doses of dexamethasone on plasma cortisol concentrations and adrenal responses to ACTH in horses

Adrenocortical function was assessed in horses given multiple IM doses of dexamethasone to determine the duration of adrenocortical suppression and insufficiency caused by 2 commonly used dosages of dexamethasone (0.044 and 0.088 mg/kg of body weight). Dexamethasone was administered at 5-day intervals for a total of 6 injections. Daily blood samples were collected. The plasma was frozen and later assayed for cortisol. An ACTH response test was determined 2 days before the first injection of dexamethasone and again 8 days after the last dexamethasone injection. Maximum suppression of plasma cortisol was observed in horses given both dosages of dexamethasone (0.044 and 0.088 mg/kg). Plasma cortisol concentrations returned to base-line values in all horses by 4 days after dexamethasone injection. Normal ACTH responses observed after 6 dexamethasone injections given at 5-day intervals indicated that measurable adrenal atrophy did not develop under the conditions of this study.

Gastric distention and gastrin in the dog

Gastric distention was induced in intact dogs by giving a wide range of volumes (11 to 111 ml/kg) of a liquid test meal resulting in a significant (P less than 0.05) increase in plasma gastrin immunoreactivity at 10 and 25 minutes after distention. There was no significant decrease in gastrin immunoreactivity from 10 to 25 minutes of gastric distention. Pretreatment with atropine abolished the distention-induced gastrin release, indicating that distention-induced gastrin release in the intact dog was partially under cholinergic control. There was no relationship between the distending volume and magnitude of gastrin increase.

Effects of flunixin meglumine on blood pressure and fluid compartment volume changes in ponies given endotoxin

A study was conducted to determine whether body fluids undergo a net shift from one compartment to another during endotoxin-induced shock in the pony, and whether flunixin meglumine alters these endotoxin-induced changes in the volumes of body fluid compartments. Total blood, RBC, and plasma volumes were determined, using 51Cr-labeled RBC and PCV that were corrected for trapped plasma. Total body water was measured by distribution of 3HOH. Arterial blood pressure was measured directly, using a blood pressure transducer. Treatment (flunixin meglumine, 1.1 mg/kg of body weight) was given to 6 of the 12 ponies 1 minute before an IV injection of Escherichia coli endotoxin (100 micrograms/kg of body weight, LD100). The PCV and RBC volume increased in both groups; however, the hemoconcentration was less in flunixin meglumine-treated ponies. In nontreated ponies, total blood volume and plasma volume decreased significantly during the first hour after endotoxin administration. In treated ponies, total blood volume did not vary significantly, and plasma volume decreased only slightly. In both groups, the increase in PCV was apparently due to splenic contraction, which increased the number of circulating RBC. Hemoconcentration was further increased in nontreated ponies by the loss of plasma into the interstitial space. Flunixin meglumine reduced plasma loss, minimized hemoconcentration, and maintained normal blood volume. Total body water remained constant in treated and nontreated ponies.

Thyrotropin-releasing hormone stimulation testing in healthy dogs

Serum triiodothyronine (T3) and thyroxine (T4) concentrations were determined after IV administration of 200 micrograms of thyrotropin-releasing hormone (TRH) to 10 healthy euthyroid dogs. Significant (P less than 0.05) changes were not found in the T3 concentration throughout an 8-hour sampling interval. All dogs had a significant increase (P less than 0.05) in the T4 concentration at 4, 5, 6, 7, and 8 hours after TRH administration. The largest increase in the serum T4 concentration occurred 4 hours after TRH injection. From 4 to 8 hours after TRH administration, the mean increase above basal T4 concentrations was 13.9 +/- 5.4 ng/ml.

Flunixin meglumine attenuation of endotoxin-induced damage to the cardiopulmonary vascular endothelium of the pony

Endotoxic shock was induced in 5 ponies by intraperitoneal injections of 20, 40, 60, 80, and 80 micrograms of Escherichia coli endotoxin (LPS)/kg of body weight at 0, 6, 12, 18, and 24 hours, respectively. At 24 hours, the ponies also were given 20 micrograms of LPS/kg via catheter in the left ventricle of the heart. A 2nd group of 4 ponies was given 1.1 mg of flunixin meglumine (FM)/kg, IV, at 6, 12, 18, and 24 hours just before the corresponding LPS injection. Two hours after the 24-hour LPS injection, the ponies in both groups were anesthetized, the lungs were perfused with fixative, and portions of the pulmonary arteries and veins and right and left ventricles were prepared for scanning and transmission electron microscopy. In ponies that were given only LPS, some areas of pulmonary vascular endothelium appeared normal when compared with untreated controls, but other areas had disoriented endothelial cells or had varying amounts of sloughing, which ranged from focal areas of a few cells to large areas of denuded endothelium. Ponies treated with FM before LPS had less severe and less extensive endothelial cell damage. In both groups, leukocytes were attached to areas of the vessel wall; endothelial cell damage was greater in these regions. Administration of FM before LPS administration attenuated the LPS-induced endothelial cell damage.

Endotoxin-induced hematologic and blood chemical changes in ponies: effects of flunixin meglumine, dexamethasone, and prednisolone

To evaluate the effect of certain drugs on hematologic changes, blood chemical values, and survival in endotoxin shock, anesthetized ponies were given (IV) endotoxin (Escherichia coli O55:B5) and then treated as follows: Group A ponies--given a saline infusion at 5 minutes and at 3 hours after they were given endotoxin; group B ponies--given flunixin meglumine at 5 minutes and at 3, 6, 9, and 24 hours after they were given endotoxin; group C ponies--treated with dexamethasone; and group D ponies--treated with prednisolone at 5 minutes and at 3, 9, and 24 hours after they were given endotoxin. Anesthesia was maintained for 4 hours, after which time the ponies were allowed to recover. Throughout the experiment, samples of blood were collected for blood gas, hematologic, and blood chemical values. The endotoxin effects were seen in the 4 groups: lactic acidosis, prolonged coagulation times, leukopenia, hemoconcentration, and elevated blood chemical values. Although none of the treatments prevented the effects of endotoxin, changes were less severe and survival times were longer in ponies treated with flunixin meglumine.

Plasma gastrin immunoreactivity in dogs with acute gastric dilatation-volvulus

Plasma gastrin immunoreactivity was measured by radioimmunoassay in 45 dogs with acute gastric dilatation-volvulus (GDV). Significant increases (P less than 0.05) were found in dogs with acute GDV and in the fasted state after surgical treatment and recovery. The data suggested that dogs that have had GDV may have preexisting high plasma gastrin immunoreactivity. In dogs with acute GDV, plasma gastrin immunoreactivity was not found to be helpful in formulating prognosis. Circumcostal gastropexy did not affect plasma gastrin immunoreactivity.

Endotoxin-induced hemodynamic changes in dogs: role of thromboxane and prostaglandin I2

Plasma concentrations of thromboxane and prostaglandin I2 (PGI2) before and after IV injection of endotoxin and resulting hemodynamic changes were evaluated. Effects of flunixin meglumine on plasma concentrations of these prostaglandins and the related hemodynamic changes were also determined. Shock was induced in 2 groups of anesthetized dogs. Four dogs were given endotoxin only and 4 dogs were given endotoxin and then were treated with flunixin meglumine. Arterial blood pressure (BP), cardiac output (CO), and heart rate were measured, and blood samples were collected at postendotoxin hours (PEH) 0, 0.1, 0.25, 0.5, 1, 2, 3, and 4. Plasma thromboxane and PGI2 concentrations were increased in canine endotoxic shock. Thromboxane concentration was highest early in shock, and appeared to be associated with an initial decrease in BP and CO. The increased concentration of PGI2 was associated with systemic hypotension at PEH 1 to 2. Treatment of dogs with flunixin meglumine at PEH 0.07 prevented further increase of thromboxane and blocked the release of PGI2, resulting in an increased CO, BP, and tissue aerobic metabolism.

Effects of naloxone on endotoxin-induced changes in ponies

The value of naloxone (1 mg/kg of body weight/hr for 4 hrs), a beta-endorphin antagonist, was assessed in the management of endotoxin-induced shock in ponies. Three groups of 5 ponies each were used: controls, ponies given Escherichia coli endotoxin put untreated, and ponies given endotoxin and then treated with naloxone. Endotoxin-induced changes in hemodynamics, blood chemical values, regional blood flow, plasma enzymes, and energy supplies were measured at selected times during the first 6 hours after endotoxin was given. There was no evidence that beta-endorphins released during shock were responsible for the hemodynamic changes, blood flow changes, plasma enzyme changes, or energy deficits, because naloxone, at this dosage level, did not prevent these endotoxin-induced changes.

Metabolism of estrogens in the gastrointestinal tract of swine. II. Orally administered estradiol-17 beta-D-glucuronide

Studies were conducted to determine the absorption and metabolic fate of orally administered 3H-estradiol-17 beta-glucuronide (3H-E2-G) in swine. Xylazine-tranquilized female pigs (5 to 6 wk old) were given .04, .4 or 4 mumol 3H-E2-G via stomach tube, and blood samples were collected from previously implanted jugular cannulas for 12 or 72 h. The entire gastrointestinal tract was removed from gilts euthanatized 12 h post-treatment, and free and conjugated estrogens were isolated from plasma and intestinal chyme by diethyl ether extraction and adsorption to Amberlite XAD-2 resin columns. After preparative thin layer chromatography of the conjugate fractions, the conjugates were cleaved by enzyme hydrolysis, solvolysis or acid hydrolysis. The freed estrogens were identified by thin layer chromatography. Plasma radioactivity peaked between 6 and 8 h after administration of the conjugate. None of the radioactivity in plasma was ether extractable. There was evidence for a decrease in absorption rate of radioactive estrogen in the high dosage group. The pattern of metabolites and urinary excretion or orally administered 3H-E2-G was similar to that reported for 14C-E2, except for the greater proportion of polar metabolites and delayed absorption, probably reflecting the need for the conjugate to be hydrolyzed first. The greater proportion of polar metabolites found in this study may have been due to the longer treatment period rather than the administration of the conjugated form of estradiol.

Metabolism of estrogens in the gastrointestinal tract of swine. III. Estradiol-17 beta-D-glucuronide instilled into sections of intestine

Studies were conducted to determine the absorption and metabolic fate of 3H-estradiol-17 beta-glucuronide (3H-E2-G) in swine. The conjugate, 3H-E2-G (48.7 x 10(6) DPM, 45.5 Ci/mmol), was injected into ligated 15-cm sections of duodenum, proximal jejunum, distal jejunum, ileum and spiral colon of 10 kg female pigs. Blood from the jugular and portal veins and urine were collected at .5-h intervals for 5 h. Absorption from the colon was rapid and radioactivity peaked in both portal and jugular plasma by .5 h postinjection. In contrast, the highest plasma estrogen concentration from most other sections was reached at 5 h, the last sampling time. The urinary excretion patterns were nearly identical to those seen in plasma, with the radioactivity peaking early (1.5 h) after instillation of 3H-E2-G into the colon, but still rising at the end of the experiment after instillation into the duodenum, distal jejunum and ileum. The proximal jejunum, which produced low plasma estrogen concentrations, also produced low urine concentrations. The slower absorption of 3H-E2-G compared to 14C-estradiol-17 beta is consistent with the view that the limiting factor for the absorption of the conjugate is hydrolysis to a free estrogen. The predominant metabolites in portal venous plasma from all sections of the intestine at the end of the experiments were the monoglucuronides of estrone and estradiol. Because the administered 3H-E2-G was conjugated at C-17, the presence of estrone glucuronide in portal plasma indicates that, at least in the duodenum, ileum and colon, 3H-E2-G undergoes cleavage, followed by the oxidation of estradiol to estrone, which is subsequently reconjugated by the intestinal mucosa.

Metabolism of estrogens in the gastrointestinal tract of swine. I. Instilled estradiol

One minute after instillation of 14C-estradiol-17 beta (14C-E2 17 beta) into selected sections of the gastrointestinal tract of swine, radioactive estradiol metabolites were present in blood collected from the portal and jugular veins. Ether was used to extract free but not conjugated estrogens. The percentage of plasma radioactivity that was ether extractable (EE) was low in portal plasma and even lower in jugular plasma following instillation of 14C-E2 17 beta into the stomach, ileum and colon. EE radioactivity was not detectable in either portal or jugular plasma when estradiol was instilled into the duodenum or jejunum. Therefore, estrogens were conjugated either in the lumen of the gastrointestinal tract or as they crossed the intestinal mucosa. The liver played only a minor role in conjugation of these steroids, since the estrogen metabolites present in portal plasma were very similar to those in jugular plasma, and metabolites in the urine were similar to those in plasma. The principal estrogen conjugate found in both portal and jugular plasma, regardless of the gastrointestinal section into which 14C-E2 17 beta was instilled, was estrone glucuronide. There was no uniform metabolic pattern observed in the metabolites of estradiol that remained in the lumen of each gastrointestinal section; however, many metabolic transformations occurred. We concluded that almost all estrogens absorbed were metabolized during the absorption process. The liver was active only in the metabolism of estrogens that escaped conjugation in the intestinal mucosa.