Identification and the primary structure of equine alpha-lactalbumin B and C (Equus caballus, Perissodactyla)

The presence of two new alpha-lactalbumins has been demonstrated in the colostrum of a single mare (Equus caballus, Persian Arab). They have been designated equine alpha-lactalbumin B and C, and that isolated previously from the milk of Australian horses (English Thoroughbred) as alpha-lactalbumin A. The primary structures of B/C have been determined by automatic Edman degradation of enzymatic cleavage of the oxidized protein. Cyanogen bromide cleavage of S-carbamoyl-methylated protein provided necessary overlapping peptides. Comparison of the sequences of B and C with that of A indicates 3 and 4 amino-acid exchanges, respectively. The phylogenetic difference of equine alpha-lactalbumin B/C from bovine alpha-lactalbumin B is indicated by 39 and 40 amino-acid exchanges, respectively. The structure-function relationship, calcium binding sites and variants of alpha-lactalbumin are discussed.     

Plasma lipid transport in the horse (Equus caballus)

• 1.1. Equine plasma contains lipoproteins corresponding to very low density (VLDL), low density (LDL) and high density lipoproteins (HDL).
• 2.2. HDL accounts for approximately 60% of plasma lipoprotein mass and consists of a single population of particles.
• 3.3. LDL is heterogeneous comprising three discrete subfractions.
• 4.4. Two proteins are found in the region of apolipoprotein (apo) B-100 in VLDL and LDL and a third similar to apo B-48 is in VLDL.
• 5.5. Lecithin:cholesterol acyl transferase is active in plasma and hepatic lipase and lipoprotein lipase are evident in post-heparin plasma.
• 6.6. There is no significant cholesteryl ester transfer protein activity.

     

Social feeding decisions in horses (Equus caballus)

Like many other herbivores, in a natural environment equids feed on rather evenly distributed resources. However, the vegetation in their vast habitats constantly changes. If food is plentiful only little competition occurs over food, and in non-competitive situations domestic horses tend to return to the same feeding site until it is overgrazed. In contrast, they compete over limited food for which the social status of the individuals appears to be important. Especially in ruminants several studies have proved an influence of social organisations, rank, sex and the depletion of feeding sites on the feeding behaviour of individuals. However, it is not yet understood whether and how social aspects affect horses' feeding decisions. Curiosity about the influence of social rank on the horses' feeding decisions between two, equally with high-quality surplus food-filled buckets placed in different social feeding conditions, led us to create the test below. The observer horses were alternately tested with a dominant and a subordinate demonstrator placed in one of the three different positions. We conclude that domestic horses use social cognition and strategic decision making in order to decide where to feed in a social feeding situation. When possible they tend to return to the same, continuously supplied feeding site and switch to an "avoidance tendency" in the presence of dominant horses or when another horse is already feeding there. Thus, the social rank and the position of conspecifics affect the feeding strategy of horses.     

Ciliates from the intestine of Yakut horse (Equus caballus)

Endobiotic ciliates of native Yakut horse are investigated. 57 ciliate species have been found. From 17 up to 43 species of ciliates have been revealed in each host specimen. The specimens of Alloiozona trizona Hsiung, 1930 and Triadinium caudatum Fiorentini, 1890 were present in 100 % of the horses. The endemic genus and species of allantosomides, Strelkowella urunbasiensis Kornilova, 2004, has been found in 11 horses. Allantoxena japonensis (Imai, 1979) and Cycloposthium ishikawai Gassovsky, 1919 being recorded previously in Japan only were found for the first time in Russia. The species Cycloposthium ponomarevi Kornilova, 2001 peculiar to the Turkmenistan koulan has been found in the Yakut horses.     

Ectopic transplantation of equine invasive trophoblast

A system for transplanting invasive equine trophoblast (i.e., chorionic girdle) to ectopic sites has been developed as a means to study the differentiation of this tissue and to assess maternal immune responses to the conceptus tissue in a site outside the uterus. Chorionic girdle was isolated from Day 33 to 34 conceptuses and surgically placed into the vulvar mucosa or subdermal skin of recipient mares. Biopsy specimens of the graft sites for immunohistochemical staining were taken at weekly or biweekly intervals after grafting. Serum samples were collected from each recipient and tested for antibody to donor major histocompatibility complex (MHC) class I antigens using the lymphocyte microcytotoxicity assay. Transplanted trophoblast cells expressed differentiation markers associated with invading chorionic girdle and endometrial cup cells. The transplanted trophoblast cells were also labeled by an antibody to eCG. Strong cellular and humoral immune responses to the transplanted tissue were mounted by the recipients, similar to those occurring during normal equine pregnancy. Despite these responses, the invasive trophoblast transplants survived for at least 28 days after grafting and downregulated MHC class I antigens, as do the mature endometrial cup cells in equine pregnancy. These findings suggest that invasive equine trophoblast has the capacity to differentiate fully in equine nonuterine tissues, and that it can evade maternal immune responses independent of the physiological state of pregnancy and in sites other than the uterus.     

The entotympanic of Equus caballus (Perissodactyla,Mammalia)

In the majority of extant placental mammals the bulla tympanica is composed of two skeletal elements, the entotympanic and the ectotympanic. Former studies revealed that the presence of an entotympanic in the bulla tympanica of extant Perissodactyla is restricted to Rhinocerotidae. The existence of the entotympanic in Tapiridae and Equidae remained speculative. Here we present the first evidence of an entotympanic, strictly speaking rostral entotympanic, in the domestic horse, Equus caballus. The enchondrally ossified entotympanic can be easily separated from the desmal ectotympanic by its greater thickness and by its cancellous bone texture in a late fetal stage. Both elements are separated by a suture that is in the process of coalescence. The complete fusion of the two elements and the unification of bone texture are almost accomplished at birth but the entotympanic and ectotympanic assume the same thickness obviously not until early postnatal development. Based on modern phylogenetic hypotheses we can conclude that the common ancestor of Perissodactyla must have possessed a well-developed entotympanic, probably only evident in their fetal life. This must be considered as a plesiomorphic character state of this order, because the entotympanic is a neomorphic apomorphy of placental mammals. However, the prenatal fusion of the entotympanic and the ectotympanic is an apomorphy of Equus caballus and possibly of the Equidae as a whole.     

Quantitative analysis of voltage-gated potassium currents from primary equine (Equus caballus) and elephant (Loxodonta africana) articular chondrocytes

In this comparative study, we have established in vitro models of equine and elephant articular chondrocytes, examined their basic morphology, and characterized the biophysical properties of their primary voltage-gated potassium channel (Kv) currents. Using whole cell patch-clamp electrophysiological recording from first-expansion and first-passage cells, we measured a maximum Kv conductance of 0.15 +/- 0.04 pS/pF (n = 10) in equine chondrocytes, whereas that in elephant chondrocytes was significantly larger (0.8 +/- 0.4 pS/pF, n = 4, P 相似文献   

Characterization of horse (Equus caballus) immunoglobulin mu chain-encoding genes

 Horse (Equus caballus) immunoglobulin mu chain-encoding (IgM) variable, joining, and constant gene segments were cloned and characterized. Nucleotide sequence analyses of 15 cDNA clones from a mesenteric lymph node library identified 7 unique variable gene segments, 5 separate joining segments, and a single constant region. Based on comparison with human sequences, horse variable segments could be grouped into either family 1 of immunoglobulin (Ig) clan I or family 4 of Ig clan II subclan IV. All horse sequences had a relatively conserved 16 base pair (bp) segment in framework 3 which was recognized with high specificity in polymerase chain reaction by a degenerate oligonucleotide primer. Horse complementarity determining regions (CDR) had considerable variability in predicted amino acid content and length but also included the presence of relatively conserved residues and several canonical sequences that may be necessary in formation of the β chain main structure and conformation of antigen-binding sites through interaction with light chain CDR. Sequence analysis of joining regions revealed the presence of nearly invariant 3′ regions similar to those found in human and mouse genes. A single horse IgM constant region comprising 1472 bp and encoding 451 residues was also identified. Direct comparison of the horse constant region predicted amino acid sequence with those from eleven other species revealed the presence of 53 invariant residues with particularly conserved sequences within the third and fourth exons. Phylogenetic analysis using a neighbor-joining algorithm showed closest similarity of the horse mu chain-encoding constant region gene to human and dog sequences. Together, these findings provide insights into the comparative biology of IgM as well as data for additional detailed studies of the horse immune system and investigation of immune-related diseases. Received: 14 October 1996 / Revised: 10 December 1996     

An investigation of colour discrimination with horses (Equus caballus)

The ability of four horses (Equus caballus) to discriminate coloured (three shades of blue, green, red, and yellow) from grey (neutral density) stimuli, produced by back projected lighting filters, was investigated in a two response forced-choice procedure. Pushes of the lever in front of a coloured screen were occasionally reinforced, pushes of the lever in front of a grey screen were never reinforced. Each colour shade was randomly paired with a grey that was brighter, one that was dimmer, and one that approximately matched the colour in terms of brightness. Each horse experienced the colours in a different order, a new colour was started after 85% correct responses over five consecutive sessions or if accuracy showed no trend over sessions. All horses reached the 85% correct with blue versus grey, three horses did so with both yellow and green versus grey. All were above chance with red versus grey but none reached criterion. Further analysis showed the wavelengths of the green stimuli used overlapped with the yellow. The results are consistent with histological and behavioural studies that suggest that horses are dichromatic. They differ from some earlier data in that they indicate horses can discriminate yellow and blue, but that they may have deficiencies in discriminating red and green.     

Breathing strategy of the adult horse (Equus caballus) at rest

To investigate the mechanism underlying the polyphasic airflow pattern of the equine species, we recorded airflow, tidal volum, rib cage and abdominal motion, and the sequence of activation of the diaphragm, intercostal, and abdominal muscles during quiet breathing in nine adult horses standing at rest. In addition, esophageal, abdominal, and transdiaphragmatic pressures were simultaneously recorded using balloon-tipped catheters. Analysis of tidal flow-volume loops showed that, unlike humans, the horse at rest breathes around, rather than from, the relaxed volume of the respiratory system (Vrx). Analysis of the pattern of electromyographic activities and changes in generated pressures during the breathing cycle indicate that the first part of expiration is passive, as in humans, with deflation toward Vrx, but subsequent abdominal activity is responsible for a second phase of expiration: active deflation to below Vrx. From this end-expiratory volume, passive inflation occurs toward Vrx, followed by a second phase of inspiration: active inflation to above Vrx, brought about by inspiratory muscle contraction. Under these conditions the abdominal muscles appear to share the principal pumping duties with the diaphragm. Adoption of this breathing strategy by the horse may relate to its peculiar thoracoabdominal anatomic arrangement and to its very low passive chest wall compliance. We conclude that there is a passive and active phase to both inspiration and expiration due to the coordinated action of the respiratory pump muscles responsible for the resting adult horse's biphasic inspiratory and expiratory airflow pattern. This unique breathing pattern perhaps represents a strategy of minimizing the high elastic work of breathing in this species, at least at resting breathing frequencies.     

Purification of horse (Equus caballus) serum lecithin:cholesterol acyltransferase

1. A method for the purification of horse serum lecithin:cholesterol acyltransferase has been established. 2. The method involves the adsorption of the enzyme from diluted horse serum on DEAE-Sephadex A-50, (NH4)2SO4 fractionation, 1-butanol treatment, and chromatographic techniques of DEAE-Sepharose CL-6B, DEAE-Sephadex A-50, Affi-Gel blue and hydroxylapatite. 3. The resultant enzyme preparation essentially formed a single main band when subjected to polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. 4. The final purification of the enzyme was 20,000-fold with 7% yield. 5. The apparent mol. wt of the enzyme was 64,000. 6. The activity of the enzyme was stable for 3 days at 0 degree C.     

Characterization of horse (Equus caballus) T-cell receptor beta chain genes

Genes encoding the horse (Equus caballus) T-cell receptor beta chain (TCRB) were cloned and characterized. Of 33 cDNA clones isolated from the mesenteric lymph node, 30 had functionally rearranged gene segments, and three contained germline sequences. Sixteen unique variable segments (TCRBV), 14 joining genes (TCRBJ), and two constant region genes (TCRBC) were identified. Horse TCRBV were grouped into nine families based on similarity to human sequences. TCRBV2 and TCRBV12 were the most commonly represented horse families. Analysis of predicted protein structure revealed the presence of conserved regions similar to those seen in TCRB of other species. A decanucleotide promoter sequence homologous to those found in humans and mice was located in the 5 untranslated region of one horse gene. Germline sequences included the 5 region of the TCRBD2 gene with flanking heptamer/nonamer recombination signals and portions of the TCRBJ-C2 intron. Southern blot hybridizations demonstrated restriction fragment length polymorphisms at the TCRBC locus among different horse breeds.     

Elastic extension of leg tendons in the locomotion of horses (Equus caballus)

Several of the distal leg muscles of horses have such extremely short muscle fibres that their changes of length in locomotion must be due almost entirely to elastic extension of their tendons. Films of a horse have been analysed to determine these extensions, using data obtained by experiments on dissected legs. The tendons investigated experience peak strains of 3–6% in walking, 3–7% in trotting and 4–9% in galloping. These strains occur while the foot is on the ground.     

Spatial relations between mares and foals of the Welsh pony (Equus caballus)

Welsh pony mares and foals (Equus caballus) were usually found to be within 1 or 5 m of each other during the first week of the foal's life and gradually spent more time at greater distances as the foals became older. There was an overall levelling of the trend during the 9th–15th weeks of life of the foal, followed by a second period of change during weeks 16–24. Through weeks 21–24, mares and foals spent at least half of their time within 5 m of each other. Proximity was primarily due to foal activity except during foal recumbency. During the first 8 weeks of the foal's life, a mare remained close by when it was recumbent, either by grazing in a circle around it or by standing upright beside it. Mares and foals were most likely to be close together when they were resting upright with the other ponies in the herd and most likely to be far apart when the foal was playing. Similarities in patterns of spatial relationship between the foals of a given mare were demonstrated. There was no difference between colts and filies in the development of independence.