Aqueous humour and cerebrospinal fluid collected at necropsy as indicators of ante mortem serum 3-OH butyrate concentration in pregnant sheep

[Post-mortem clinical pathology in cattle - an additional tool for the veterinary pathologist]

Clinical-pathologic examination of samples collected from more or less preserved body compartments during necropsy may provide important information and contribute to the list of differential diagnoses without corresponding patho-morphologic findings. It furthermore allows for diagnoses that otherwise may only be achieved clinically. Our review presents diagnostic approaches in examining aqueous humor, urine, ruminal fluid as well as other sample types characterized by a delayed onset of auto- and heterolytic artefacts. An overview is provided concerning post mortem (p. m.) sample types and collection methods with a special focus on cattle. Furthermore, clinical-pathologic methods and parameters are presented and their validity discussed. A summary of pre-analytical caveats relevant for the final interpretation of findings is made available. Based on long-term experience in p. m. clinical pathology as well as literature information we provide practical approaches for daily routine diagnostics as well as for specific case scenarios. Especially aqueous humor, ruminal fluid, and urine are easily accessible sample types. The collection of high-quality cerebrospinal fluid allows for electrolyte and metabolite analyses. Post-mortem clinical pathology may provide an indication concerning the cause of death in specific cases e. g., recumbency and death due to hypocalcemia or hypomagnesemia. This is especially relevant in cases in which ante mortem clinical pathology investigations are hindered by rapid death of the animal as well as in cases in which the gross pathology findings cannot explain the clinical findings. Post-mortem clinical pathology may also be helpful when a clinical examination of the diseased animal is hampered. During necropsy for example uremia and ketosis may be detected based on their characteristic smell; however, the use of clinical chemical analyses allows the verification by an assessment of the metabolites in these cases. Post-mortem clinical pathology may hence help in establishing a diagnosis, narrow down the list of differentials or even reveal relevant differential diagnoses for the first time during the diagnostic process. Our review does not claim to be exhaustive; however, it serves to encourage the pathologist to make use of the so far rarely employed ancillary analyses as well as to promote the collaboration between veterinary and clinical pathologists.

Relationships Between Concentrations of Biological Variables in Eye Fluids and Blood After Exercise in Lidia Cattle

Lidia cattle are a heterogeneous Iberian cattle population known for its natural aggressiveness and resistance to traditional handling procedures making in vivo blood sampling and biological fluid collections extremely difficult. Blood variables are influenced by physical exertion and stressful situations; consequently, post-mortem blood analysis does not reflect basal concentrations for this species. Nevertheless, ocular fluids (aqueous and vitreous humour) maintain their stable composition after death and maybe could be used to estimate ante-mortem blood concentrations. So, 15 bulls which had fought (for 15-20 minutes) and, subsequently after death, blood, aqueous and vitreous humour were sampled. Total protein, albumin, triglycerides, uric acid, urea, AST, ALT, GGT, AP, CK, LDH, cholesterol, creatinine, glucose and lactate were measured. Statistical analysis and correlation coefficients between the three fluids were carried out. All variables showed high plasma concentrations of glucose, uric acid, LDH and CK, compared with normal bovine concentrations. Apart from urea, all plasma concentrations were greater than those found in ocular fluids. The measured enzymes activities were higher in the vitreous than in the aqueous humour, but only marked differences in uric acid, lactate, AP and AST were found. There was a significant correlation between creatinine in the plasma and aqueous humour, and between albumin and GGT in the plasma and vitreous humour. Glucose, creatinine and urea exhibit a high correlation between ocular fluids. All plasma concentrations were clearly modified, however ocular fluids do not seem affected, thus establishing important correlations between the blood and intraocular fluids.

Cerebrospinal Fluid

This chapter discusses the anatomy, functions, and biochemistry of cerebrospinal fluid (CSF). CSF has four major functions: physical support of neural structures, excretion and “sink” action, intracerebral transport, and control of the chemical environment of the central nervous system. CSF provides a “water jacket” of physical support and buoyancy. The CSF is protective because its volume changes reciprocally with changes in the volume of intracranial contents, particularly blood. Thus, the CSF protects the brain from changes in arterial and central venous pressure associated with posture, respiration, and exertion. Acute or chronic pathological changes in intracranial contents can be accommodated, to a point, by changes in the CSF volume. The direct transfer of brain metabolites into the CSF provides excretory function. This capacity is important because the brain lacks a lymphatic system. The lymphatic function of the CSF is also manifested in the removal of large proteins and cells, such as bacteria or blood cells, by bulk CSF absorption. The “sink” action of the CSF arises from the restricted access of water-soluble substances to the CSF and the low concentration of these solutes in the CSF.

Diagnostic techniques and clinicopathologic findings in ruminant neurologic disease

In ruminant species, cerebrospinal fluid (CSF) collection and analysis provide rapid (in some situations, instant) information to the veterinary clinician investigating a disease problem in the living animal. CSF analysis is particularly useful with respect to confirming the presence of an inflammatory lesion involving the leptomeninges,such as bacterial meningoencephalitis, and in investigating potential compressive lesions of the spinal cord. When correctly performed under local anesthesia, lumbar CSF collection in ruminants is a safe procedure and there are no harmful sequelae. Familiarity with the technique aids high extradural injection of lidocaine or xylazine, which has many applications in farm practice. There are few indications for cisternal CSF collection in food animals.