Estimation of antemortem serum electrolytes and urea concentrations from vitreous humor collected postmortem.

Electrolyte and urea levels of vitreous humor collected from bovine eyes at various times postmortem, were compared with serum levels in the same animals. Provided the vitreous humor was filtered immediately after collection, measured levels of total calcium (Ca), potassium ions (K+), sodium ions (Na+) and urea nitrogen were very consistent. For 24 hours postmortem the concentrations of Ca, Na+ and urea nitrogen remained stable, while K+ increased to approximately 55% more than the immediate postmortem level. A small study using anesthetized dogs indicated that urea nitrogen levels of vitreous humor take several hours to equilibrate with elevated blood levels. Analysis of vitreous humor may be a useful adjunct to diagnosis in cases where antemortem clinical chemistry is absent or inadequate.     

Equine vitreous humor chemical concentrations: correlation with serum concentrations, and postmortem changes with time and temperature.

Samples of equine vitreous humor were analyzed for urea nitrogen, creatinine, sodium, chloride, phosphorus, calcium, potassium, and magnesium concentrations. Fresh vitreous chemical concentrations were compared to corresponding serum concentrations and expressed as a vitreous to serum ratio. The effects of postmortem time and temperature on the stability of the chemical concentrations were determined by incubation of the samples at 4 degrees C, and 20 degrees C and 37 degrees C for 6, 12, 24, or 48 h. Chemical concentrations were generally more stable at lower temperatures and shorter incubation times.     

Postmortem eyefluid analysis in dogs, cats and cattle as an estimate of antemortem serum chemistry profiles.

This study was carried out to determine the diagnostic usefulness of postmortem eyefluid analysis in estimating antemortem concentrations of serochemical constituents. A total of 31 cattle, 18 dogs and 22 cats were selected from routine elective euthanasia submissions to a diagnostic laboratory. For all cases, a biochemical profile, including determinations for electrolytes, glucose, urea, creatinine, enzymes, cholesterol, bilirubin, protein and osmolality was performed on antemortem serum, and postmortem aqueous and vitreous humors at 0 and 24 h incubation periods. The association between serum and postmortem eyefluid chemistry values was examined using simple linear regression. A strong correlation between serum and postmortem eyefluid urea and creatinine concentrations was demonstrated in the three species examined over a 24 h postmortem interval. We concluded that an accurate estimate of antemortem serum urea or creatinine can be made from the analysis of aqueous or vitreous fluid at necropsy. An estimation of antemortem serum electrolytes (including calcium in cattle) cannot be made with a high degree of accuracy due to the amount of variability in the relationship between serum and eyefluid electrolyte values. For large molecules such as proteins, enzymes, cholesterol and bilirubin there was very poor correlation between serum and eyefluid values.     

Changes in vitreous humor associated with postmortem interval in rabbits.

Concentrations of serum and vitreous humor constituents at time of death, and concentrations of vitreous humor constituents at time of death and at 7 postmortem intervals were compared in 70 domestic, female New Zealand White rabbits (Oryctolagus cuniculus). Urea nitrogen concentration was significantly (P = 0.0094) different, but was linearly correlated in serum and vitreous humor at time of death and at the 4- and 8-hour postmortem intervals. Concentrations of gamma-glutamyltransferase were not significantly different in serum and vitreous humor at time of death, nor were concentrations significantly different in vitreous humor at time of death and at the 4-hour postmortem interval. The vitreous humor concentrations of glucose, triglycerides, sodium, potassium, cholesterol, total protein, albumin, lactate dehydrogenase, creatine kinase, aspartate transaminase, bilirubin, cortisol, and IgG were neither similar to nor predictive of serum constituents. Vitreous humor can be used as a source for estimates of serum urea nitrogen and gamma-glutamyltransferase up to 8 and 4 hours after death, respectively.     

Quantitative changes in serum concentration of bovine gut chitinase in Theileria infection

Bovine gut chitinase is exclusively produced in the liver and secreted into the blood. In the present study, we established a semi-quantitative method by Western blot analysis for measurement of the chitinase content in blood and examined its alteration during postnatal development and experimental infection with hemoprotozoan parasite in cattle. Its serum levels from 1 week to 1 year of age showed a significant increase only in 3-4-month-old group. The plasma concentration of the gut chitinase was not changed during acute inflammation caused by lipopolysaccharide but increased gradually after a Theileria injection and peaked at 52 days post-infection. It appears that the increase in the blood chitinase levels might be a defensive response in cattle against protozoan infection.     

Adverse effect of orally administered magnesium hydroxide on serum magnesium concentration and systemic acid-base balance in adult cattle

Two cows, 1 with diarrhea and 1 with signs of forestomach outflow obstruction, were treated in part with repeated doses of a commercially available antacid/cathartic preparation containing magnesium hydroxide. Both cows subsequently were determined to have hypermagnesemia, along with severe metabolic alkalosis. In addition, each cow was comatose at the time of death. A clinical study was initiated to investigate the causal relationship between the ingestion of magnesium hydroxide and the generation of hypermagnesemia and metabolic alkalosis in adult cows. Twelve healthy mature cross bred beef cows were allotted at random to a fed or fasted (simulated anorexia) group, with 2 untreated and 4 treated cows in each group. A single dose of magnesium hydroxide (1.5 g/kg of body weight, suspended in 3.8 L of warm water) was administered per os to each treated cow, whereas each control cow was given only water. Individual determinations of selected venous blood gas values (plasma bicarbonate ion [HCO3-] concentration, and base excess [BE]), serum magnesium (Mg) concentration, and urine magnesium fractional clearance ratio (Mg-FCR) were made immediately before drug administration, and at 2, 4, 8, 12, 24, and 36 hours after treatment. Compared with control values at the conclusion of the study, mean serum Mg concentration, urine Mg-FCR, plasma HCO3- concentration, and BE were significantly higher (P = 0.0001, P = 0.0015, P = 0.028, and P = 0.021, respectively) in treated cows.(ABSTRACT TRUNCATED AT 250 WORDS)     

Chemical analysis of bovine and porcine vitreous humors: correlation of normal values with serum chemical values and changes with time and temperature

Vitreous humors collected from cattle and swine at time of death were compared with serum samples collected before these animals were slaughtered to determine whether vitreous chemical constituents were stable after death occurred. Vitreous humor from 1 eye and serum were obtained from each of 120 cattle and 120 swine at slaughter. The second eye from each animal was enucleated and incubated at 4 C, 20 C, and 37 C for 6, 12, 24, and 48 hours, and then vitreous humor was obtained from the incubated eye. Serum and the fresh and incubated vitreous samples were analyzed for urea nitrogen, creatinine, sodium, potassium, calcium, magnesium, chloride, and phosphorus concentrations. In the incubated vitreous sample, stability varied for urea nitrogen, creatinine, sodium, calcium, magnesium, and chloride concentrations, but the values were generally more stable with samples incubated at lower temperatures and for shorter incubation periods. Potassium and phosphorus concentrations increased with time and temperature of incubation of the samples.     

Changes in serum concentration of phagocytosis-stimulating factor in experimentally induced bovine anaplasmosis: preliminary findings.

To determine whether correlation exists between serum concentration of phagocytosis-stimulating factor (PSF) and in vivo phagocytic activity, 2 splenectomized steers were inoculated with Anaplasma marginale, and their serum PSF concentrations were monitored. At the time of the anemic crisis, serum PSF concentrations were elevated five to tenfold.     

Serum and vitreous humor antibody titers in and isolation of Leptospira interrogans from horses with recurrent uveitis

OBJECTIVE: To measure antibody titers against Leptospira interrogans in serum and vitreous humor and determine the prevalence of L interrogans in vitreous humor of horses with recurrent uveitis. DESIGN: Cross-sectional study. ANIMALS: 242 horses (270 eyes) with recurrent uveitis undergoing vitrectomy and 39 control horses (54 eyes) without any history or clinical signs of recurrent uveitis undergoing euthanasia or enucleation for unrelated reasons. PROCEDURE: Serum and vitreous humor were tested for antibodies against 13 serovars of L interrogans. Vitreous humor was submitted for leptospiral culture; isolates were typed to the serogroup level. RESULTS: Leptospira interrogans was isolated from vitreous humor from 120/229 (52%) horses (126/252 [50%] eyes) with recurrent uveitis but was not isolated from vitreous humor from 36 eyes of 21 control horses. Duration of recurrent uveitis was > or = 1 year for 45 of the 120 (38%) horses from which the organism was isolated. Geometric mean antibody titers against L interrogans in the vitreous humor and serum of horses with recurrent uveitis were 1:1,332 and 1:186, respectively. Only 91 of 120 (76%) horses from which the organism was isolated had a 4-fold or greater difference between serum and vitreous humor antibody titers. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that persistent ocular infection with L interrogans is common in horses with recurrent uveitis. A 4-fold increase in vitreous humor versus serum antibody titers may not be a sensitive test for the diagnosis of L interrogans-induced recurrent uveitis. We hypothesize that the immune component of recurrent uveitis can be directly induced and maintained by persistent infection of the eye with L interrogans.     

Evaluation of biochemical analytes in vitreous humor collected after death in West Indian manatees

OBJECTIVE: To evaluate biochemical analytes in vitreous humor collected after death in West Indian manatees (Trichechus manatus latirostris). DESIGN: Prospective study. ANIMALS: 73 West Indian manatees of various ages and both sexes. PROCEDURE: The condition of manatee carcasses submitted for routine postmortem examination was categorized as fresh, moderately autolyzed, or severely autolyzed. The eyes were removed, frozen for shipping, and thawed on arrival at the laboratory. Vitreous humor was extracted, and various biochemical analytes were measured. Values for each analyte were compared with published reference ranges for corresponding biochemical analytes in serum. Values were also compared among the carcass condition groups. RESULTS: Creatinine and urea nitrogen concentrations in vitreous humor were significantly higher in severely autolyzed carcasses than in fresh carcasses. Potassium concentrations in vitreous humor were significantly higher in moderately autolyzed carcasses than in fresh carcasses but were highly variable in severely autolyzed carcasses. These data were consistent with those reported in other species. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that measurement of biochemical analytes in vitreous humor of manatees is feasible and has potential for assisting in the postmortem diagnosis of certain metabolic, renal, and nutritional diseases; determining severity of autolysis at time of necropsy; and determining the time of occurrence of human-induced trauma.     

The concentration of ionized magnesium in serum during the periparturient period of non-paretic dairy cows

Ion-selective electrodes have recently been designed for determining the ionized concentration of magnesium (Mg²⁺) in serum. This development may allow new insights into some metabolic diseases of cattle. For this report, the concentrations of Mg²⁺, total magnesium (Mg_tot), ionized calcium (Ca²⁺), total calcium (Ca_tot), and inorganic phosphate (P_i) were determined in sera from seventeen 3-to 16-year-old Brown Swiss and crossed Simmental/Red Holstein cows during the periparturient period. In each animal, a transient increase of Mg²⁺ and Mg_tot serum concentrations was observed in association with the transient decrease in serum concentrations of Ca²⁺, Ca_tot and P_i after parturition. On average, throughout the study, the serum Mg²⁺ concentrations were 68.5% of those of Mg_tot, whereas the serum Ca²⁺ concentrations were 52% of those of Ca_tot. The possible mechanisms involved in the transient increase of Mg²⁺ and Mg_tot serum concentrations are discussed.Abbreviations Ca²⁺ ionized calcium - Ca_tot total calcium - Mg²⁺ ionized magnesium - Mg_tot total magnesium - P_i inorganic phosphate - PTH parathyroid hormone - PTHrP parathyroid homrone related protein     

Changes in urea nitrogen and creatinine concentrations in the vitreous humor of cattle after death

The mean urea nitrogen concentration in vitreous humor (VUN) in 97 healthy steers after death was 15.7 mg/dl. The mean serum urea nitrogen concentration in the same cattle was 20.0 mg/dl. The mean vitreous creatinine (VC) concentration was 0.7 mg/dl, and the serum creatinine value was 1.5 mg/dl. The VUN and VC were both significantly lower than serum urea nitrogen and serum creatinine, respectively, but varied in a consistent, predictable manner. In tests with 10 cows, postmortem intervals as long as 36 hours and ambient temperatures up to 30 C had no significant effects on VUN and VC. Evaluation of 8 animals with uremia confirmed that the vitreous humor is a stable fluid compartment after death, usable as an indicator of serum urea nitrogen and creatinine.     

Postmortem titin proteolysis is influenced by sarcomere length in bovine muscle

The calpain protease system, in particular, μ-calpain is involved in the disassembly of specific myofibrillar proteins, resulting in tenderization of meat postmortem. Given the size, complexity, and integral nature of titin to the structure of the sarcomere, it is plausible that the length of a sarcomere may alter the susceptibility of various domains of titin to cleavage by the calpains. Therefore, we hypothesized titin degradation differs in a sarcomere-length-dependent manner in beef. After slaughter, beef carcasses were split and sides were either suspended by the Achilles tendon (normal suspension, NS) or by the aitchbone (hip suspension, HS). Immediately after suspension, samples were dissected from the LM, psoas major (PM), and semitendinosus (STN) muscles to serve as 0-d controls. After 24 h, 4 steaks were removed from each muscle and randomly assigned to 1-, 4-, 7-, or 10-d aging treatments. After the assigned aging period, myofibrils were purified for determination of sarcomere length. Warner-Bratzler shear force analysis was also performed to evaluate differences in tenderness. Muscle proteins were solubilized and subjected to SDS-VAGE (vertical agarose gel electrophoresis) to evaluate titin degradation. Sarcomere lengths differed (P < 0.0001) between contralateral muscles of NS and HS carcasses. Quantification of SDS-VAGE gels revealed less (P < 0.05) intact titin in the PM muscle of NS carcasses at each aging period compared with the PM of HS carcasses. No significant differences (P > 0.05) were detected in the disappearance of intact titin among suspension methods in the LM or STN. These data demonstrate that suspension method alters proteolysis of titin and suggest an increase in sarcomere length may contribute to the susceptibility of titin to postmortem proteolysis in beef.     

Evaluation of a kinetic test kit for the determination of magnesium in bovine serum or plasma

The performance of a new kinetic assay test kit for the determination of magnesium in plasma or serum has been evaluated, using bovine plasma samples. The results obtained were compared with the results from a standard atomic absorption spectrophotometry method and a commercial colorimetric test kit. The kinetic kit compared favourably with the conventional methods and generally gave results with greater precision.     

Intracellular free magnesium concentration in healthy horses

Equine metabolic syndrome (EMS) is a worldwide disease in horses that parallels human diabetes mellitus type 2. In both diseases, patients show an altered peripheral insulin sensitivity as a key feature. In humans, multiple studies have demonstrated the beneficial effect of magnesium supplementation on insulin sensitivity. However, serum magnesium levels vary and are therefore not a reliable indicator of the patients’ magnesium status. Determining the intracellular free magnesium concentration appears to be a more sensitive diagnostic indicator. In this study, the free intracellular magnesium concentration was measured using mag‐fura 2 spectrophotometry in blood lymphocytes in 12 healthy, non‐obese horses at 9 a.m., 12 a.m. and 4 p.m. to establish reference ranges according to a protocol designed for human blood lymphocytes. Additionally, the serum magnesium concentration was measured. In all horses, the total serum magnesium concentration was within the reference range. The mean free magnesium concentration in blood lymphocytes of all horses was 0.291 ± 0.067 mmol/L with no significant difference between the time points. The reference range for the free intracellular magnesium concentration in equine lymphocytes was set at 0.16–0.42 mmol/L. The established values are slightly lower than those in healthy humans. The designed protocol for the measurement of the intracellular free magnesium concentration might be an excellent research tool to assess the cellular magnesium status and to reliably diagnose an altered magnesium homeostasis in EMS. Further studies shall elucidate possible alterations in cellular magnesium status in horses with EMS.     

Reduced serum lecithin:cholesterol acyltransferase activity and cholesteryl ester concentration in calves experimentally inoculated with Pasteurella haemolytica and bovine herpes virus-1

Lecithin:cholesterol acyltransferase (LCAT), the enzyme responsible for esterification of cholesterol in plasma, is reported to be implicated in the regulation of inflammation in laboratory animals. The purpose of the present study was to elucidate the possible relevance of LCAT in the pathogenesis of calf pneumonia induced by inoculations of Pasteurella haemolytica and bovine herpes virus-1 into the calf lung. Serum LCAT activity was significantly (P < 0.01) reduced in calves inoculated with Pasteurella haemolytica. The concentration of cholesteryl esters (CE), the product of the LCAT reaction, was also decreased in the inoculated group. Decreases in LCAT activity and the CE concentration were similarly observed in calves in which bovine herpes virus-1 was inoculated. In both bacteria- and virus-inoculated calves, CE concentrations in the high-density lipoprotein fractions were distinctly decreased, whereas those in the low-density lipoprotein fractions were practically unaltered. The acute-phase proteins haptoglobin and serum amyloid A were detected in sera from the bacteria- and virus-inoculated calves; however, the two acute-phase proteins were also found in sera from the control calves. These results suggest that decreases in LCAT activity and the CE concentration are involved in the pathogenesis of pneumonia induced by inoculation of calves with Pasteurella haemolytica and bovine herpes virus-1, and also that the change in the LCAT system is more intimately related to the occurrence of calf pneumonia than the induction of acute-phase proteins such as haptoglobin.