Daily rhythm of tear production in normal dog maintained under different Light/Dark cycles.

This study was conduced to assess the daily rhythm of tear production in clinically healthy dog. For our study eight female purebred Beagles were subjected to three different Light/Dark schedules: 12/12L/D, 24/0L/D and 0/24L/D cycles. In all subjects Schirmer tear test I was performed at 4h intervals over a 24h period. A statistical significant effect of photoperiod was observed comparing the three different L/D schedules, and a statistical significant difference was observed comparing left and right eye during the 12/12L/D schedule. We demonstrated daily variation of tear production in dogs maintained under an L/D cycle. We also provided strong evidence that the rhythm of tear production is endogenously generated because it persisted in constant darkness. Although the range of excursion of the daily/circadian oscillation in STT I (about 2mm/min) is likely too narrow to be of clinical significance, it is statistically significant and may have physiological implications not yet appreciated.

Daily pattern of some fatty acids in the athletic horse.

In the sport field, non-esterified fatty acids (NEFA) are important for the physical performance during the aerobic exercise of short intensity and long duration. In man, rat, goat and in the sedentary horse studies on the chronometabolism showed the presence of a circadian rhythm of the plasmatic concentration of NEFA while data for the athletic horse are lacking. To define a chronogram helpful for a specific planning and the differentiation of the training programmme in the athletic horse, the circadian pattern of some fatty acids (NEFA, palmitic, stearic, oleic, linoleic and linolenic acids) was studied in five Sella Italiana horses. These horses trained following a daily model of activity consisting of walk, trot, gallop and jump of obstacles of different heights. Blood samples were collected from the jugular vein every 4 h, starting at 08:00 hours, for 2 days to assess the concentrations of total NEFA (by spectrophotometry), palmitic, stearic, oleic, linoleic and linolenic acids (by gas chromatography). anova for repeated measures showed a statistical significant effect of the time of the day in NEFA, oleic and linolenic acids. The application of the periodic model showed the periodic pattern of NEFA, oleic, linoleic and linolenic acids. Acrophases were in the afternoon for all parameters. The results obtained showed a different trend of the circadian pattern of the studied parameters in the athletic horse than in the sedentary one because the physical activity and the post-prandial metabolism acted as zeitgebers.

Serum homocysteine and oxidative stress evaluation during exercise in horse.

The aim of the present work was to evaluate the influence of exercise on serum homocysteine and oxidative stress in Thoroughbreds during official races. For our study, ten Thoroughbred mares, 5 years old and clinically healthy, were used. The horses were trained to take part in an official 2100 meter race. Reactive oxygen species (dROMs), antioxidant barrier (Oxy-adsorbent), thiol antioxidant barrier (SHp) and homocysteine (sHcy) were investigated. Blood samples, collected from each horse at rest, immediately after the race, and 30 and 180 min after the end of the race, were collected by jugular venipuncture using vacutainer tubes with no additive for the assessment of dROMs, Oxy-adsorbent and SHp by means of a UV spectrophotometer, while serum total Hcy values were determined by high performance liquid chromatography with fluorimetric detection and isocratic elution. Statistical analysis, one way repeated measures analysis of variance (ANOVA), followed by Bonferroni's test, showed statistical differences (P<0.05 was considered statistically significant) for all parameters studied. Moreover, a coefficient of linear correlation (r) was computed for values of dROMs and sHcy for all sampling times but a significant linear regression (r = 0.94) was found only after the race. The variations of sHcy, dROMs, Oxy-adsorbent and SHp during the experimental period considered suggest the important role of oxidative status in the athletic horse. The systematic analysis of oxidative stress and its influence on homocysteine levels contribute to the clinical evaluation and assessment of the athletic performance of the horse.

Annual rhythmicity and maturation of physiological parameters in goats.

This study was conducted to investigate seasonal rhythmicity and maturation of physiological parameters in goats. Five kids (Capra hircus, Maltese breed) were studied for 24 months, starting at 5 months of age. Rectal temperature and various blood-borne substances (melatonin, cholesterol, urea, total bilirubin, albumin, glucose, calcium, magnesium, phosphate, and sodium) were measured once a month at dawn and dusk. Serum bilirubin concentration exhibited statistically significant 12-month rhythmicity, and melatonin concentration exhibited 6-month rhythmicity. Changes in the dusk-to-dawn difference in rectal temperature during the course of the study provided suggestive evidence that the circadian rhythm of body temperature in goats is not fully developed until the end of the second year of life. The results documented also maturational changes in cholesterol production and blood glucose regulation.

Modifications of some acute phase proteins and the white blood cell count in thoroughbreds during training.

The concentrations of plasma fibrinogen and serum haptoglobin and the white blood cell count (WBC) were assessed in 17 thoroughbreds. All horses were trained for 80 days, six days a week, with one day of rest per week. Blood samples were collected from each animal by jugular venepuncture, at 06.00, every 20 days for a period of 80 days, and the fibrinogen and haptoglobin concentrations and WBC were determined. One-way repeated measures analysis of variance, followed by the Bonferroni test, was used to determine significant differences. Training was associated with a significant increase in the concentrations of plasma fibrinogen (P<0.01) and serum haptoglobin (P<0.0005), but had no significant effect on the WBC count.

Daily rhythms of serum and salivary parameters in goats.

OBJECTIVE: Determine the daily rhythms of urea, bicarbonate, sodium, potassium, chloride, calcium, magnesium and inorganic phosphorus secretion in the serum and saliva of goats and whether there is a relationship between them. DESIGN: Ten non-gravid, non-lactating does underwent a 30-day preconditioning period (natural 24-h photoperiod, environmental temperature 19-21 degrees C, relative humidity 40-50%, the same feeding regimen, offered as a single meal at 07:00 hours, and water ad libitum), following which saliva and blood samples were collected from each subject every 4 h for 2 days (starting at 08:00 hours) for measurement of urea and electrolytes. RESULTS: Data analysis was conducted by one-way repeated measures analysis of variance (ANOVA) and by the single cosinor method. ANOVA showed a significant effect of time (0.001 < P < 0.01) on all the studied parameters in saliva and serum on both days. Cosinor analysis identified the periodic parameters and their acrophases (expressed in hours) during the 2 days of monitoring. Serum and salivary acrophases were all diurnal and were observed between 11:40 and 16:24 hours. No circadian rhythmicity was found for bicarbonate, magnesium or potassium in either saliva or serum. CONCLUSION: There was a daily rhythm of secretion for the majority of the measured parameters, suggesting the potential role of saliva as an additional, reliable index for physiological, clinical, nutritional and chronophysiological studies.

Daily rhythms of liver-function indicators in rabbits.

Serum concentrations of urea and cholesterol were used as indicators of liver function in rabbits in an investigation of the responsiveness of the daily rhythm of liver function to phase shifts in the environmental light-dark cycle. Locomotor activity was simultaneously monitored by actigraphy. Serum urea and cholesterol concentrations exhibited robust daily rhythmicity with opposite phases. Both indicators of liver function phase shifted in response to phase shifts of the light-dark cycle. The phase shifts in liver function appeared to be parallel to phase shifts in locomotor activity, but the data were not sufficiently strong to confirm that the liver relies on the secondary effect of photic phase shift on ingestive behavior in order to be phase-shifted by light as previously indicated by gene expression studies in laboratory rodents.

The influence of exercise on the daily rhythm of serum homocysteine in horses.

The aim of this study was to determine the daily rhythms in the blood serum of homocysteine in horses. Ten thoroughbred horses, five athletic (trained for 1 h, 6 days a week) and five sedentary, were used. Blood samples were collected on each subject every 4 h for two days by means of the jugular vein. On each individual sample, the serum concentration of homocysteine was assessed. The results obtained during the experimental period indicated the existence of a daily rhythm of serum homocysteine in sedentary and athletic horses. They also demonstrated that in horses, physical exercise influences the daily rhythm of serum homocysteine.

Temporal relationships of 21 physiological variables in horse and sheep.

Daily or circadian oscillation has been documented in a variety of physiological and behavioral processes. Although individual variables have been studied in great detail, very few studies have been conducted on the temporal relationships between the rhythms of different variables. It is not known whether the circadian pacemaker generates each and every rhythm individually or whether most rhythms are simply derived from a few clock-controlled rhythms. As a first step in elucidating this issue, 21 physiological variables were recorded simultaneously in horse and sheep. The results indicated that, in both species, different variables exhibit different degrees of daily rhythmicity and reach their daily peaks at different times of the day. The variables exhibiting strongest rhythmicity were locomotor activity, rectal temperature, and plasma concentrations of melatonin and glucose. Comparison of rhythmicity and acrophase in the various rhythms allowed inferences to be made about mechanisms of causation.

Daily rhythms of blood pressure, heart rate, and body temperature in fed and fasted male dogs.

Daily or circadian rhythmicity in physiological processes has been described in a large number of species of birds and mammals. However, in dogs, most studies have either failed to detect rhythmicity or have found that rhythmicity reflects merely an acute exogenous effect of feeding rather than an autonomous rhythmic process. In the present study, we investigated the rhythmicity of body temperature, blood pressure, and heart rate in dogs fed daily as well as in dogs deprived of food for 60 h. Our results document clear rhythmicity in all three parameters and demonstrate that the rhythmicity is independent of the feeding schedule. The failure of various previous investigations to document daily rhythmicity in dogs is probably due to lack of experimental rigour rather than to weakness of daily rhythmicity in dogs.

Amino acid concentrations in blood serum of horses performing long lasting low-intensity exercise.

The aim of this work was to evaluate the changes in the concentrations, after two rides different for distance covered, of different amino acids in endurance horses. Blood samples have been collected from horses just before the start, at the top of a steep slope (819 m difference in height) and just at the end of a 32-km endurance ride. A second group, competing in a 72 km endurance ride, has also been sampled immediately before and after the race. In serum samples, the concentrations of alanine, arginine, asparagine, glycine, isoleucine, histidine, leucine, lysine, methionine, ornithine, phenylalanine, tryptophan, tyrosine and valine have been measured by high-performance liquid chromatography (HPLC). anova and t-test have been used to study the differences in the concentrations of the amino acids. The pre-ride concentrations of the free amino acids were different between the two races, except for methionine and leucine. Differences between start and end race have been found for both groups for all the considered parameters except asparagine, isoleucine, leucine and lysine for the 72 km ride. Increases have been recorded for the shorter and decreases for the longer ride in the blood serum concentrations. Significant increases have also been found between the starting sampling and the second, at the top of the slope, only for alanine, arginine, asparagines, phenylalanine and lysine. The ride length has a significant impact on blood serum amino acids mobilization and uptake; in the shorter race the increases stand only for mobilization, whereas in the longer the decrease can be considered the effect of the onset of the amino acids catabolism.

Monitoring of physiological and blood parameters during perinatal and neonatal period in calves / Monitoramento de parâmetros fisiológicos e sanguíneos de bezerros durante os períodos perinatal e neonatal

Rectal temperature, heart and respiratory rates, and the course of some blood parameters were monitored in calves during perinatal and neonatal periods. The study was carried out on eight Limousine calves. From all subjects, rectal temperature, heart rate, and respiratory rate were measured. Blood samples were taken at the same hour (9am) from the external jugular vein, and then centrifuged and stored until analyses. By means of an UV spectrophotometer, the following blood parameters were assessed for each subject: total protein, total cholesterol, triglycerides, glucose, non-esterified fatty acids (NEFA), urea, creatinine, cholinesterase, lactate dehydrogenase (LDH), hydroxybutirate, glutamate pyruvate transaminases (GPT), glutamate oxalacetate transaminases (GOT), direct and total bilirubin, magnesium, iron, potassium, phosphorus, chloride and sodium. The results showed a significant effect of days of life (P<0.05) only on total cholesterol, creatinine and GOT during the first week of life and a significant effect of days of life on rectal temperature, heart rate, respiratory rate, total cholesterol, NEFA, creatinina, and GOT during the first month of life. A correlation among individual values for postnatal age (days of life) and heart rate in calves during the first month of life was observed. In conclusion, modifications of studied parameters could be attributed to functional development of calves in neonatal period and contribute to the knowledge of adaptation processes in calf during the first week and the first month of life resulting useful for the diagnosis and treatment of any neonatal diseases.

Realizou-se o monitoramento da temperatura retal das frequências cardíaca e respiratória e de alguns parâmetros sanguíneos em oito bezerros da raça Limousine, durante o período perinatal e neonatal. Paralelamente às mensurações da temperatura retal e das frequências cardíaca e respiratória (9h), foram pesquisados, por meio de espectrofotômetro de UV, proteína total, colesterol total, triglicérides, glicose, ácidos graxos não esterificados (NEFA), ureia, creatinina, colinesterose, lactato desidrogenase (LDH), hidroxibutirato, glutamato piruvato transaminases (GOT), direta e total bilirrubina, magnésio, fósforo, cloretos e sódio. Os resultados mostraram efeito significativo dos dias de vida (P<0,05) somente sobre o colesterol total, creatinina e GOT, durante a primeira semana e um significante efeito de dias de vida sobre a temperatura retal, as frequências cardíaca e respiratória, colesterol total, NEFA, creatina e GOT durante o primeiro mês de vida. Observou-se correlação entre os valores individuais para dias de vida e frequência cardíaca durante o primeiro mês de vida. Conclui-se que as modificações desses parâmetros podem ser atribuídas ao desenvolvimento dos bezerros no período neonatal, contribuindo para o conhecimento do processo de adaptação, em bezerros, durante a primeira semana e o primeiro mês de vida.

Influence of shearing on the circadian rhythm of body temperature in the sheep.

The presence of functional rhythmic variations is a well-demonstrated phenomenon at all levels of physiological organization and especially in the functioning of the cell components, of tissues and of organic systems. In domestic animals, the body temperature presents spontaneous and regular periodic oscillations over different periods of time, which are the result of complex mechanisms that witness the existence of endogenous and exogenous factors. Taking this knowledge as a starting-point, the authors studied 12 Comisana breed ewes to observe the influence of shearing on the circadian periodicity of rectal and skin temperature. The obtained results show the transient loss of body temperature rhythm by shearing, with an exogenous component, the shearing itself, and an endogenous component, the modifications of metabolic levels induced by the removal of the fleece, the external insulating layer.

Blood serum branched chain amino acids and tryptophan modifications in horses competing in long-distance rides of different length.

During long-distance exercise, branched-chain amino acid (BCAA) catabolism could lead to an increase in the blood tryptophan/BCAA ratio and an early onset of 'central fatigue'. Based on these considerations, we studied the modifications of blood serum BCAA and tryptophan (Try) levels in 30 endurance horses competing in rides varying in distance from 20 to 72 km. From all horses, blood samples were drawn just before and just after the end of the ride. Samples were analysed for their leucine (Leu), valine (Val), isoleucine (Iso) and Try levels. Data were processed by anova, using sampling moment and ride as factors, and by LSD post hoc test. Significant differences were recorded among the different distance rides for Leu, Val, Iso, Try, Try/BCAA ratio; the same trend was recorded between samples taken at the start and the end of the race for Val and Leu. The main effect observed was an increase of BCAA levels for all rides, except the 72-km ride; for Try, a significant increase was present in all races, except the 50-km ride. The Try/BCAA ratio decreased in 20- and 50-km races and increased in the others. These data confirm that long-distance exercise involves a mobilization of BCAA. The utilization of BCAA seems to be important in prolonged exercise: in the 72-km ride, we observed a decrease in BCAA blood serum levels, while a major role of Try was indicated by its increase, resulting in a rise of the Try/BCAA ratio.

Nitrogenous metabolism in Thoroughbred and Arabian foals from birth to five months of age / Metabolismo do nitrogênio em potros PSI e Arabe do nascimento aos cinco meses de idade

The maturation of nitrogen metabolism was studied in six Thoroughbred and six Arabian foals. Rectal temperature, heart and respiratory rates and serum concentration of several hematochemical parameters (total protein, urea, uric acid, creatinine, and albumine) were monitored from birth to 5 months of age. In both breeds, all the parameters except albumine showed significant differences over time (P<0.05). The two breeds did not differ from each other at any time point. Statistically significant decreases in urea and creatinine concentrations were related to the growth needs of foals during this critical period of development.

A maturação do metabolismo do nitrogênio foi estudada em seis potros da raça Puro-Sangue Inglês e seis da raça Arabe. A temperatura retal, batimento cardíaco e concentração sérica de várias características hematoquímicos (proteína total, uréia, ácido úrico, creatinina e albumina) foram investigadas do nascimento aos cinco meses de idade. Em ambas as raças, todas as características, exceto a albumina, mostraram diferenças significativas ao longo da maturação (P<0,05). As duas raças não diferiram uma da outra durante os períodos de vida equivalentes. Reduções significativas das concentrações de uréia e creatinina mostraram as necessidades de crescimento dos potros durante esse período crítico de desenvolvimento.