Effect of repeated freeze-thaw cycles on routine plasma biochemical constituents in canine plasma.

BACKGROUND: The effect of repeated freeze-thaw cycles on plasma constituents has not been assessed in dogs, although such a procedure is not uncommon to use in routine laboratory practice. OBJECTIVE: To assess the effect of freeze-thaw cycles on routine plasma constituents in healthy dogs. METHODS: Six healthy adult dogs were used. Blood was sampled and placed in heparinized tubes. After centrifugation, plasma was separated into 5 aliquots. One aliquot was considered as the reference aliquot and used immediately for the assay of all of the biochemical constituents. All of the other aliquots were stored at 20 degrees C. Three aliquots underwent 1, 2, or 3 freeze-thaw cycles during a 1- to 3-day period. The last aliquot remained at 20 degrees C throughout the study and was thawed on the third day. The following biochemical constituents were assayed: glucose, urea, creatinine, total proteins, sodium, potassium, chloride, calcium, phosphates, aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine kinase (CK), and alkaline phosphatase (ALP). RESULTS: No clinically relevant change was observed between the different aliquots for all of the constituents. CONCLUSION: Repeated freeze-thaw cycles do not cause changes in the biochemical constituents studied in canine plasma.

Cardiovascular effects of dietary salt intake in aged healthy cats: a 2-year prospective randomized, blinded, and controlled study.

High salt dry expanded diets are commercially available for cats to increase water intake and urine volume, as part of the prevention or treatment of naturally occurring urinary stone formation (calcium oxalates and struvites). However, chronic high salt intake may have potential cardiovascular adverse effects in both humans, especially in aging individuals, and several animal models. The objective of this prospective, randomized, blinded, and controlled study was to assess the long-term cardiovascular effects of high salt intake in healthy aged cats. Twenty healthy neutered cats (10.1 ± 2.4 years) were randomly allocated into 2 matched groups. One group was fed a high salt diet (3.1 g/Mcal sodium, 5.5 g/Mcal chloride) and the other group a control diet of same composition except for salt content (1.0 g/Mcal sodium, 2.2 g/Mcal chloride). Clinical examination, systolic and diastolic arterial blood pressure measurements, standard transthoracic echocardiography and conventional Doppler examinations were repeatedly performed on non-sedated cats by trained observers before and over 24 months after diet implementation. Radial and longitudinal velocities of the left ventricular free wall and the interventricular septum were also assessed in systole and diastole using 2-dimensional color tissue Doppler imaging. Statistics were performed using a general linear model. No significant effect of dietary salt intake was observed on systolic and diastolic arterial blood pressure values. Out of the 33 tested imaging variables, the only one affected by dietary salt intake was the radial early on late diastolic velocity ratio assessed in the endocardium of the left ventricular free wall, statistically lower in the high salt diet group at 12 months only (P = 0.044). In conclusion, in this study involving healthy aged cats, chronic high dietary salt intake was not associated with an increased risk of systemic arterial hypertension and myocardial dysfunction, as observed in some elderly people, salt-sensitive patients and animal models.

Acute changes in muscle blood flow and concomitant muscle damage after an intramuscular administration.

PURPOSE: The intramuscular route (IM) is widely used but commonly induces injection site muscle damage. This study investigates the hemodynamic changes in an acute lesion induced by the IM administration of propylene glycol (PG) in rabbits. METHODS: Control groups received 1, 2, or 3 ml of PG (IM). Others were pretreated with pancuronium, dantrolene, indomethacin, or SR140333 and then received 2 ml of PG. The muscle blood flow (MBF) was assessed using fluorescent microspheres before and at 15, 45, 60, 90 min, 3 and 6 h after IM administration. Different areas within the muscle damage were quantified. RESULTS: Muscle contractions as well as a transient but major MBF increase were observed at the injection site. All treatments reduced hyperemia by up to 81% (dantrolene, 15 min) at 15, 45, and 90 min (p < 0.05). MBF had returned to basal values in all groups at 6 h. The central necrotic area was not modified, but peripheral damage (8.0 +/- 1.3 g) was reduced by dantrolene, indomethacin, and SR140333 (p < 0.05), but not by pancuronium. CONCLUSIONS: Muscle contraction and hyperemia are not responsible for muscle damage at the injection site, which is the multifactorial phenomenon, involving intracellular calcium and inflammation.