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Topic:Physiology
The physiology of horses encompasses the study of the biological functions and processes that occur within the equine body. This includes the examination of various systems such as the cardiovascular, respiratory, musculoskeletal, digestive, and nervous systems. Understanding equine physiology is essential for comprehending how horses adapt to different environmental conditions, perform physical activities, and respond to health challenges. Research in this field often focuses on the mechanisms of energy metabolism, thermoregulation, and muscle function during exercise, as well as the physiological responses to stress and disease. This page compiles peer-reviewed research studies and scholarly articles that explore the diverse aspects of equine physiology, providing insights into the biological processes that support the health and performance of horses.
Lymphocyte stimulation response in horses against phytohaemagglutinin and M protein of Streptococcus equi using whole blood. Lymphocyte stimulation was observed in whole equine blood in the presence of phytohaemagglutinin and M protein extracted from a typical strain of Streptococcus equi. Blood samples were collected from several healthy horses and horse and pony foals and cultured in vitro with varying concentrations of phytohaemagglutinin and M protein for several days. Phytohaemagglutinin was found to induce lymphocyte stimulation in these animals. Highest mean stimulation indices in horse foals (49.3 +/- 24.4) and pony foals (54.7 +/- 32.0) were observed with 0.625 and 1.25 micrograms/mL phytohaemagglutinin, re...
Endometrial change in the annual reproductive cycle of the mare. Cervical and endometrial swabs were taken from 7 mares at various stages of the oestrous cycle. There was no consistent pattern of cell change throughout the cycle. The dominant cell in smears from normal mares was the columnar epithelial cell, especially in smears obtained during oestrus. A ciliated columnar epithelial cell was found much less frequently but appeared more often in smears before oestrus. Endometrial biopsies were also collected from 7 mares at intervals 2-3 weeks over an 8-month period from the beginning of spring to the end of autumn. There was no obvious change in the endome...
Melatonin rhythms in Pony mares and foals. Melatonin concentrations in intact (N = 3) and sham-operated (N = 3) mares during March were greater (P less than 0 . 05) during the night than during the day, but this pattern was not seen in 3 mares from which the superior cervical ganglia had been removed bilaterally. When 4 Pony mares were exposed to a photoperiod of 10L:14D for 3 weeks and then to continuous darkness (0L:24D) for another 3 weeks, melatonin levels were greater (P less than 0 . 05) at the end of the 0L:24D period than during the earlier period and still displayed rhythmic fluctuations but were no longer co-ordinated with eq...
Termination of twin gestation by blastocyst crush in the broodmare. Manual crushing of one blastocyst performed on 181 bicornuate twin pregnancies between Days 24 and 45 has shown that the uncrushed blastocyst can either survive and develop normally to full term or may be rejected and resorbed like its crushed twin, depending mainly on the stage of pregnancy. Crushing, which causes rupture of fetal membranes, results in a rapid fall in the survival rate of the uncrushed blastocyst when performed after Day 31. In some mares rupture is not possible after Day 35 even if extreme pressure is used. Crushed, but unruptured, blastocysts mainly between Days 35 and 45 m...
Titration of antiserum to South American rattlesnake (Crotalus durissus terrificus) venom by measuring inhibition of phospholipase A2 activity. Horse antiserum to the venom of Crotalus durissus terrificus, A South American rattlesnake, inhibits the phospholipase activity of the crude venom. There is a close relationship between this inhibitory property and the neutralizing potency of the antiserum in vivo. This may provide the basis for a rigorous standardization of anticrotalid venom in vitro.
Factors affecting testis weight in normal and cryptorchid horses. Testes were collected from normal and cryptorchid horses of a variety of breeds and ages and weighed after dissection from the epididymis. Scrotal testes grow little until the second winter of life and little thereafter, although a nearly mature body weight is reached by the end of the first winter. Scrotal testes in unilateral cryptorchids tend to be larger than those of normal stallions, sometimes exceedingly so, although occasional small scrotal testes are recorded. Inguinal testes show some tendency to grow during the second winter but the data are difficult to analyse beyond that age beca...
Uterine prostaglandin F metabolite production in relation to glucose availability in late pregnancy and a possible influence of diet on time of delivery in the mare. The production of uterine PGFM during different dietary states has been investigated in pregnant mares in late gestation. Arterial and uterine venous plasma concentrations of PGFM rose when food was withdrawn for 12-30 h and the V-A difference widened significantly. There was an inverse correlation between the rise in PGFM and the fall in plasma glucose during a fast, and a significant decrease in the A-V plasma glucose differences across the uterus. Plasma PGFM and free fatty acid concentrations before and during food withdrawal were also correlated but no uterine A-V difference in free fatty...
Influence of bacterial products on the motility of stallion spermatozoa. Sterile filtrates were prepared from equine isolates of Klebsiella pneumoniae (genitalium), Proteus mirabilis, Pseudomonas aeruginosa, Escherichia coli, Streptococcus zooepidemicus, Streptococcus equisimilis, Actinobacillus equuli, and Corynebacterium equi and mixed individually with extended stallion semen. When diluted in the extended semen the filtrates represented bacterial populations of 0.5 x 10(6), 1 x 10(6), 2 x 10(6) and 4 x 10(6) cells/ml. pH values were recorded for each filtrate. Specimens were monitored for percentage motile spermatozoa at 30-min intervals until they reached 10% o...
Ovarian response, pregnancy rate, and incidence of multiple fetuses in mares treated with an equine pituitary extract. The ability of a pituitary extract to induce ovulation and the effect of multiple ovulations on pregnancy rate and incidence of multiple fetuses were studied in seasonally anovulatory mares. The extract induced ovulation in 95% of mares having a greater than or equal to 25 mm follicle at the onset of treatment and in 64% the ovulations were multiple. The extract was less effective when the largest initial follicle was less than 25 mm. Approximately 50% of the treated mares that ovulated did not become pregnant or enter prolonged dioestrus before returning to an anovulatory condition. In treate...
Electron microscopy of the ventricular lining associated with the hypothalamus and median eminence of prepubertal female horses. Scanning electron microscopy showed that cells in the infundibular recess of prepubertal female horses were devoid of cilia and sparsely covered with stubby microvilli and small blebs, whereas superior ventricular areas were covered with cilia. Ciliated ependymal cells in supraoptic-suprachiasmatic areas were associated with extensive blebbing, and folded tissue adjacent to the inferior borders of the mamillary body displayed distinct bands of cilia regularly interrupted by areas of sparsely ciliated cells which appeared to be undergoing ciliogenesis. Arcuate ependymal areas had well developed...
The optimum pH of renal adenosine triphosphatase in rats: influence of vanadate, noradrenaline and potassium. In the presence of vanadate, the optimum pH of renal (Na+, K+)-ATPase in rats is reduced and lies in the range of intracellular pH. This explains the difference in optimum pH observed with ATP extracted from equine muscle. Removal of vanadate from such ATP (with noradrenaline) raises the optimum to the accepted range obtained with synthetic ATP. Changes in the sensitivity of the enzyme to potassium concentration contribute to the alterations in optimum pH. The optimum pH of Mg-ATPase is unaffected by vanadate. Since vanadate may be an intracellular regulator of (Na+, K+)-ATPase changes of opti...
Fetal loss and the effect of stress on plasma progestagen levels in pregnant Thoroughbred mares. The depressing effect on plasma progestagen levels of pregnant mares subjected to specific stressful conditions such as severe pain, infectious diseases, emotional disturbances and exogenous corticosteroids are described. It is concluded that the detrimental effect of stress, evident from its negative influence on plasma progestagen concentrations, could play a major role in the occurrence of pregnancy failure in the Thoroughbred mare.
Preliminary characterization of equine interferons and their antiviral activities on bovine, ovine, and human cells. Equine dermal cells induced with poly I:C + DEAE-dextran produced low levels of interferon tentatively classified as equine interferon beta (EqIFN-beta). In contrast, dermal cells initially primed with EqIFN-beta and then superinduced with poly I:C + DEAE-dextran in the presence of cycloheximide and actinomycin D produced greater than 100-fold EqIFN-beta. Equine blood mononuclear cells induced with Newcastle disease virus and phytohemagglutinin produced high levels of interferons tentatively classified as equine interferon alpha (EqIFN-alpha) and equine interferon gamma (EqIFN-gamma), respecti...
Metabolism of purine nucleosides and phosphoribosylpyrophosphate in thymocytes and splenocytes of various mammalian species. 1. Activities of ADA, PNP and AK were measured in splenocytes and thymocytes of newborn children, young horses, pigs, sheep, rats and mice and compared with the activities previously found in peripheral lymphocytes. 2. With all species, except horse, the activity of ADA (per 10(6) cells) was higher in thymocytes than in lymphocytes. Activity of ADA was highest in splenocytes of pig and sheep. Activity of ADA was lowest in all lymphoid cells of the horse and only about 10% of the activity in human splenocytes and lymphocytes. 3. With all species, except horse, the activity of PNP was lower in t...
Ultrastructural study of the development of the pars distalis (anterior pituitary) in the foal. The pituitary glands of 4 horse embryos (41-55 days of gestation) were examined by light microscopy, and the pars distalis from 10 fetal foals (75-300 days) was examined by electron microscopy. At Day 41 the development of Rathke's pouch and the saccus infundibuli was advanced; the former had almost lost its connection with the stomodaeum and the latter had started to differentiate into infundibular process and infundibular stalk. By Day 43 Rathke's pouch was completely dissociated from the stomodaeum and its walls were beginning to show uneven growth. The ventral wall of the pouch, the future...
Immune recognition of Echinococcus granulosus. 1. Parasite-activated, primary transformation by normal murine lymph node cells. Culture of murine lymph node cells together with living protoscolices of Echinococcus granulosus is described. The presence of the parasite induced potent blastic transformation in lymphocytes of unimmunized mice as indicated by tritiated thymidine incorporation. The response was markedly reduced by killing the parasite immediately prior to culture. No blastogenic activity was detectable in supernatants from living parasites cultured alone. Protoscolices from artificially infected syngeneic mice were effective stimuli, as were protoscolices from naturally infected horse and sheep. Stimulation ...
Effect of the stage of the oestrous cycle on the follicular population in pony mares. In the middle of the breeding season, 16 pony mares (n = 4 per day) were slaughtered on four different days (days 6, 14, 17 and the preovulatory day) of the oestrous cycle, day 0 being the day of the last ovulation. All the ovaries were examined histologically; the number, size and atresia (defined by granulosa cell pyknosis) of all follicles larger than 1 mm in diameter were studied, using a Kryotome-video recorder-TV system. Follicular distribution of all the sizes studied (1-5 mm, 5-10 mm, greater than 10 mm in diameter) was very similar in the right and left ovaries. However, compared to t...
Effects of pituitary stalk transection on endocrine function in Pony mares. The pituitary stalk was transected in 10 Pony mares by a surgical approach that involved dorsal reflection of the brain and micro-dissection from the ventro-lateral aspect of the pituitary. Diabetes insipidus was the most immediate and marked result, requiring extensive electrolyte and antidiuretic therapy for approximately 48 h after operation. Fluid stasis then developed and no further supportive measures were necessary. Endocrine challenge tests with GnRH and TRH before and after stalk transection indicated a loss of responsiveness (GnRH) or suppressed responsiveness (TRH) after the operati...
Secretion of free and conjugated steroids by the horse testis into lymph and venous blood. In 3 testes of 2 adult Pony stallions under halothane anaesthesia, catheters were inserted into a vein and a lymphatic vessel in the spermatic cord and into a vein on the surface of the testis. Lymph and venous blood were collected from the catheters in the cord and p-aminohippurate (2% w/v, 0 . 1 ml/min) was infused into the vein on the testis to determine blood flow by dilution. After 1 h, 6000 i.u. hCG was injected i.v. and collections continued for 45 min. The testes weighed 126-176 g. Lymph flow was 20-150 microliter/min before hCG and 100-270 microliter/min after hCG; the range of blood ...
Cibacron Blue-induced modification of neutral proteinase from horse blood leukocytes. The proteolytic activity of the elastase-like proteinase from granules of horse blood leukocytes is retained on a column of Cibacron Blue-Sepharose and can be eluted with 0.5 M KSCN. During this procedure its mol. wt. is reduced from 49000 to 30000 and isoelectric point is shifted towards higher pH. The inactive protein not adsorbed on Cibacron Blue-Sepharose is strongly acidic and shows a mol. wt. of 20000. Upon mixing this protein with the modified enzyme the native proteinase is reconstituted as shown by polyacrylamide gel electrophoresis at pH 8.3 and isoelectric focusing in a sucrose grad...
Chronic obstructive pulmonary disease anatomical cardiac studies. An abattoir survey on horses diagnosed as suffering from chronic obstructive pulmonary disease (COPD) on clinical grounds showed that the right ventricular wall thickness was not significantly different from that of normal horses. However, the weight ratio between the left and right ventricles was found to be significantly (P less than 0.001) different in COPD affected, compared with control, horses in a study of 17 physiologically and pathologically confirmed COPD cases, using ventricular weight measurements. No clinical evidence of right heart failure nor post mortem evidence of right heart ...
The density profile and cholesterol concentration of serum lipoproteins in domestic and laboratory animals. 1. By means of density gradient ultracentrifugation, the density profile of the serum lipoproteins was studied in 14 species of domestic and laboratory animals: the pig, chicken, rhesus monkey, rabbit, dog, horse, sheep, cat, mouse, goat, cow, guinea-pig, trout and rat. 2. The concentration of cholesterol in whole serum and the lipoprotein fractions of these animal species was also determined. 3. There were large differences in the density profile of the serum lipoproteins among the various animals studied and the results indicate that the density limits employed for human serum lipoproteins a...
Inhibition of sperm binding to porcine ova by antibodies to equine zonae pellucidae. Sera and follicular fluid from mares previously determined as having antibodies to the zona pellucida were exposed to porcine ovarian oocytes before insemination with boar spermatozoa in vitro. There was a dramatic decline in the number of spermatozoa bound to zonae compared to treatments with sera and follicular fluid from mares negative for zona antibodies. These data suggest that antibodies reactive with the zona pellucida may be responsible for reduced or even complete infertility in some mares. In a group of 50 randomly selected mares tested for antizona antibodies, 2 pregnant mares were ...
[Gangliosides of neural and extraneural tissues of various species of mammals]. The ganglioside patterns of the forebrain, cerebellum and brain stem from horse, donkey, mule and goat have been determined by thin-layer chromatography. GM1, GD1a, GD1b and GT1b are the four major brain gangliosides. N-acetylneuraminic acid as the predominant sialic acid (congruent to 97%) and traces of N-glycolyneuraminic acid were found. The four above mentioned major gangliosides were also found in the forebrain, cerebellum and brain stem of adult rats. This pattern is not modified in rats under stress situation (at 4 degrees C for 3 months). In other extraneural organs from rats such as l...
Further observations on the innervation of the proximal sesamoidean ligament of the horse and ox. A vegetative innervation is described for the first time in this district. On the contrary, the finding of Pacini and pacini-like corpuscles, of Golgi Mazzoni's receptors, of muscle spindles and Golgi's tendon-organs testifies the existence of a sensitive innervation in this anatomical territory. According to Karamanlidis free nervous endings are not present. All the above recorded receptors show the typical structure and can be found isolated, grouped to constitute flower-sprays, organized to form opposito-polar corpuscles or associated to originate pecilomorphic fibers. These two last findin...
A random walk model for the migration of Strongylus vulgaris in the intestinal arteries of the horse. A study of the migration of fourth stage larvae of the parasite Strongylus vulgaris in the intestinal arteries of the horse is presented. It is established, that the larvae migrate along the arteries in almost straight lines. It is suggested that this is primarily due to their ability to sense the curvature of the vessel wall, and not, as might have been expected, because of an ability to sense the direction of blood flow. A larva will sometimes alter its direction of motion when encountering a small off-branching artery. This behaviour suggests, that the migration of S. vulgaris larvae can be...
Limited trypsinolysis of porcine and equine colipases. Spectroscopic and kinetic studies. Porcine and equine colipases have been submitted to mild tryptic digestion. Proteolysis occurs at the Arg5-Gly6 bond with the loss of the N-terminal pentapeptide. Studies of native and trypsin-treated colipases by circular dichroism and laser chemically induced dynamic nuclear polarization indicate that proteolysis induces conformational changes in the region of the tyrosine cluster. Experiments in the presence of phospholipid provide further evidence showing that these residues are in or close to the region of the protein interacting with aggregated lipids. Kinetic studies of the reaction of ...
Species specificity of estrogen biosynthesis in pregnancy. Immunochemical difference of placental NADPH-cytochrome c (P-450) reductase in human, baboon and horse. NADPH-cytochrome c (P-450) reductases from human placental aromatase II and from horse placental microsomes were solubilized and purified to show a single band of 83,000 daltons in SDS-polyacrylamide gel electrophoresis. Rabbits were immunized with purified human placental aromatase II NADPHcytochrome c (P-450) reductase. The resulting antibodies (Reduc-Ab) were used to examine the species specificity of estrogen biosynthesis and the reductase activity in humans, baboons, horses and rats. Rcduc-Ab suppressed androstenedione aromatase activity in human, baboon and horse placental microsomes wit...
Plasma and tissue concentrations of oxytetracycline in the horse after intravenous administration. Oxytetracycline (OTC) was administered IV to 3 clinically normal horses at a dosage of 10 mg of OTC/kg of body weight. Plasma OTC concentrations were determined at 30-minute intervals until postinjection minute (PIM) 240. At PIM 240, the mean OTC concentration in pulmonary tissue was 3.96 microgram/g of tissue (wet weight) and in renal tissue was 25.47 micrograms/g. diluted bronchial fluid had a mean concentration of 0.288 microgram of OTC/ml at PIM 240. The data demonstrated that OTC has adequate tissue distribution in horses.
Influence of prostaglandin F2 alpha on sperm production and seminal characteristics of the stallion. Six mature stallions were used to test the effect of prostaglandin F2 alpha (PGF2 alpha ) on sperm production and seminal characteristics. Semen was collected from each stallion twice weekly 1 hr following a 10 mg intramuscular injection of PGF2 alpha or a sham injection. A switchback design was used so that three stallions received PGF2 alpha and three served as controls during the first 9 weeks (period 1). Treatment regimens were reversed during the second 9 weeks (period 2). Treatment of stallions with PGF2 alpha resulted in an increase (P less than .05) in gel free seminal volume and a dec...
