Neuromuscular blocking agents in equine anesthesia

In summary, neuromuscular blocking agents can be used safely and to advantage in equine anesthesia. Muscle-relaxant use in equine anesthesia has been helped by the development of new relaxants such as atracurium, which has a reliable and reproducible duration of action. There are certain cases that benefit particularly by the use of relaxants but their use is not limited to these cases. These cases involve horses that experience persistent movement and hypotension during anesthesia, are undergoing ophthalmic or abdominal surgery or fracture repair, or are severely ill. Horses receiving muscle relaxants during anesthesia require mechanical ventilation, and neuromuscular blockade should be monitored with a peripheral-nerve stimulator.     

Treatment of oestriasis and hypodermosis in red deer (Cervus elaphus hippelaphus) and roe deer (Capreolus c. capreolus) with ivermectin (Ivomec)

In two test areas in Austria (Burgenland, Lower Austria) ivermectin has been used to control oestrinosis and hypodermosis in red- and roe deer since many years (1985 and 1987, respectively). The results until 1992, using the injectable solution Ivomec-injection 1% only, have been reported (Kutzer, 1994). In continuation of these tests Ivomec-Praemix 0.6% was examined and it turned out that the treatment was extremely successful. In practice Ivomec-Praemix 0.6% has to be given preference due to its stability. The most favourable dosage for red- and roe deer was 2 x 0.4 mg ivermectin/kg bodyweight administered at an interval of one week, although equally good results could be obtained with 1 x 0.3-0.4 mg ivermectin/kg bodyweight. With the above mentioned dosages against Pharyngomyia picta and Cephenemyia stimulator an up to 100% and against Hypoderma actaeon a 100% success of treatment could be achieved. The administration in two doses has the advantage to eradicate intestinal and lung nematodes at the same time if there are any. Finally, it was found that the controlling measures should not be interrupted for more than one year, if no treatment was done in the neighbouring hunting grounds.     

Hypothalamic control of the thyroidal axis in the chicken: over the boundaries of the classical hormonal axes

The pituitary gland, occupying a central position in the hypothalamo-pituitary thyroidal axis, produces thyrotropin (TSH), which is known to stimulate the thyroid gland to synthetize and release its products, thyroid hormones. TSH is produced by a specific cell population in the pituitary, the so-called thyrotropes. Their secretory activity is controlled by the hypothalamus, releasing both stimulatory and inhibitory factors that reach the pituitary through a portal system of blood vessels. Based on early experiments in mammals, thyrotropin-releasing hormone (TRH) is generally mentioned as the main stimulator of the thyrotropes. During the past few decades, it has become clear that the hypophysiotropic function of the hypothalamus is more complex, with different hormonal axes interacting with each other. In the chicken, it was found that not only TRH, but also corticotropin-releasing hormone (CRH), the main stimulator of corticotropin release, is a potent stimulator of TSH secretion. Somatostatin (SRIH), a hypothalamic factor known for its inhibitory effect on growth hormone secretion, was demonstrated to blunt the TSH response to TRH and CRH. In this review we summarize the latest studies concerning the "interaxial" hypothalamic control of TSH release in the chicken, with a special emphasis on the molecular components of these control mechanisms. It remains to be demonstrated if these findings could also be extrapolated to other species or classes of vertebrates.     

The detection of transmissible gastroenteritis viral antigens by immunodiffusion.

Parathyroid (PT) glands from 20-day-old embryonic chicks cultured in a chemically defined medium secreted a stimulator of in vitro bone resorption. This stimulator was presumed to be parathyroid hormone (PTH) because: 1) the in vitro dose response curve was parallel to that obtained with bovine PTH; 2) the activity was eluted on Sephadex G-1--chromatography at a postition similar to that for PTH; and 3) the material produced hypercalcemia in vivo in chicks. The amount of PTH-activity secreted was inversely proportional to the calcium concentration of the medium over the range of 0.75-2.25 mM. The chick PT glands also secreted an inhibitor of PTH-stimulated bone resorption in vitro. This inhibitor was presumed to be calcitonin (CT) because: 1) the in vitro dose-response curve was parallel to that obtained with synthetic salmon CT; 2) the activity was eluted on Sephadex G-50 chromatography at a position similar to that for salmon CT; and 3) the material produced hypocalcemia in vivo in rats. In contrast to what would be expected for CT secretion, the CT-activity was secreted by the PT glands in response to a low, not high calcium concentration. The data suggest that the secretion of avian PTH is similar to that of the mammalian hormone, and that the ultimobranchialectomized chick with an intact parathyroid gland may not be deficient in CT.     

Use of a nerve locator to facilitate administration of mandibular nerve blocks in crocodilians.

As part of a clinical workup of dental problems in a large crocodilian collection, mandibular nerve blocks were performed in the animals. A nerve locator was used to facilitate placement of the nerve blocks in American alligators (Alligator mississippiensis), Yacare caiman (Caiman yacare), and a dwarf crocodile (Osteolaemus tetraspis). Provision of analgesia is a frequently underused aspect of patient care in reptiles. Use of a nerve stimulator provides an objective measurement of nerve conduction blockade and may be useful in exotic species in which anatomic landmarks for nerve block placement are not well established.     

Immunological parameters in goats experimentally infected with SRLV genotype E, strain Roccaverano

Genotype E of small ruminant lentivirus has been recently described in goats from different breeds in Italy. Genotype E infection may differ from known genotypes since deletions of dUTPase and VPR proteins have been confirmed in different independent areas and goat breed, and play a key role on virus replication and pathogenesis. In particular, genotype E Roccaverano strain has been described as low pathogenic since does not lead to clinical symptoms in goats. In contrast, classical CAEV infected goats of the same area and breed presented arthritis. In this study, we have used intratracheal and intra-bone marrow routes to establish genotype E persistent infections. Humoral and cellular immune responses elicited in the host against genotype E and genotype B derived antigens were evaluated until 200 days post-inoculation. Compared to genotype B antigen, seroconversion against genotype E GAG P16-25 antigen was detected at 2-3 weeks after inoculation, significantly earlier and at higher titres. Interestingly, antibody avidity did not increase in the course of the experiment neither against P16-25 nor against SU5, both derived from genotype E. T cell proliferation against P25-GST fusion protein antigens derived from genotype E was firstly detected at 15 days post-inoculation and was maintained throughout time until week 20 post-infection, while T cell proliferation against the genotype B P25 was not produced by the end of the experiment at 20 weeks post-inoculation. The strength of reaction was also higher when using P25 E as stimulator antigen. In contrast with antibody and T cell proliferation, cytotoxic-T-lymphocyte (CTL) activity in the circulating lymphocytes (effector cells) using blood-derived macrophages (BDM) as target cells, was not strain specific being surprisingly higher against genotype B infected antigen presenting cells (APCs). This is the first study reporting experimentally induced immunological changes in SRLV genotype E infection and indicates that CTL activity may be the adaptive immune response able to induce protection against heterologous infection.     

病毒感染与细胞核转录因子-κB信号转导的相互作用关系

自发现细胞核转录因子-κB(NF-κB)以来,人们对其分子生物学特征、作用机制及其与疾病的关系作了广泛的研究。近年来的研究结果发现,NF-κB在病毒感染与疾病发生的过程中发挥着重要作用。病毒感染真核细胞时能诱导NF-κB从细胞质转移到细胞核,从而诱导一些炎性基因转录产生大量炎性因子引起炎症反应,或阻碍细胞凋亡促进其自身在宿主细胞内的复制,或促进某些原癌基因的表达使细胞癌化等。不同病毒感染机体时,都会通过对NF-κB信号转导的影响,改变机体的某些性状,导致疾病的产生。目前已发现应激刺激、细菌脂多糖、病毒、氧自由基等很多因素能激活NF-κB,而后通过NF-κB信号转导通路的桥接作用影响机体的新陈代谢,文章就病毒感染与细胞NF-κB信号转导的相互作用关系作一综述。     

A mechanical stimulator for the determination of the minimum alveolar concentration (MAC) of halothane in the rabbit

The minimum alveolar concentration (MAC) of halothane was determined in New Zealand White rabbits. Tracheal anaesthetic concentrations were measured using a Siemens Servo Gas Monitor. A stimulator was used to deliver precisely controlled mechanical stimuli for the determination of MAC. Movement of the rabbit's head was recorded using a force transducer attached to the teeth. Evidence is presented that for the determination of MAC a precise nociceptive threshold is preferable to the so-called supramaximal stimulus used in clinical anaesthesia and in determinations of anaesthetic potency. We conclude that techniques for the determination of MAC which disregard either sensitization of sensory mechanisms by producing tissue inflammation or the possibility of nerve compression by severe mechanical stimuli are of questionable value. The use of the mechanical stimulator described, or a similar device, would help in the standardization of the determination of MAC in all species by facilitating the application of a force of controlled amplitude, duration and velocity, thereby removing some of the variables which confound comparative studies of MAC.Abbreviations DC direct current - ID internal diameter - MAC minimum alveolar concentration     

Congenital contraction of the gastrocnemius and superficial digital flexor muscles in a friesian calf

The red deer (Cervus elaphus) is a host for two louse species, Damalinia longicornis and Solenopotes burmeisteri. Little is known of their prevalence or population dynamics; numbers are likely to peak in winter. Numbers may increase secondarily to malnutrition or disease. Lice are unlikely to seriously affect deer health under most conditions. “Pour-on” insecticides have been used for treatment but their efficacy has not been critically assessed. Animals can be sprayed using garden spray equipment, providing that such equipment has not been used for other toxic chemicals such as weed killers. Little is known of the toxicity of insecticides for deer, so they should be used with care and not used on stressed animals. No lice have been recorded from the fallow deer (Dama dama) in New Zealand.

Dictyocaulus viviparus infects red and fallow deer and can cause high mortalities of young farmed red deer in their first autumn and winter. In clinical cases respiratory signs are seldom obvious but loss of condition and dullness of coat may be evident. Clinical evidence and lung lesions suggest that the pathogenesis of disease may differ from that in cattle. Anthelmintics effective against D. viviparus in cattle are not necessarily effective in deer. Little is known of the significance of lungworm to farmed fallow deer. Research on lungworm in deer is urgently needed.     

Combined paravertebral plexus block and parasacral sciatic block in healthy dogs

ObjectiveTo evaluate the effectiveness of paravertebral lumbar plexus block combined with parasacral sciatic block to anesthetize one hind limb in awake dogs.Study designRandomized, controlled, blinded experimental study.AnimalsEight healthy mongrel dogs weighing 12.4 ± 4.5 kg and aged 7 ± 2.33 years.MethodsAfter sedation with medetomidine, dogs received B1: bupivacaine 0.25%, 0.2 mL kg^?1, B2: bupivacaine 0.5%, 0.2 mL kg^?1, B3: bupivacaine 0.25% 0.4 mL kg^?1, P1: NaCl 0.2 mL kg^?1, P2: NaCl 0.4 mL kg^?1. The lumbosacral plexus was blocked through a paravertebral block of the fourth, fifth and sixth lumbar nerves combined with a parasacral block. The relevant nerves were located using a nerve stimulator and injections of each treatment were administered. Degree and durations of sensory blockade were determined through the response to a Halsted clamp pressure on the skin innervated by the saphenous/femoral and lateral cutaneous femoral nerves (lumbar dermatomes) and by the peroneal and tibial nerves. The degree and duration of motor blockade was assessed evaluating the ability to walk normally and proprioception.ResultsP1 and P2 treatments did not show any grade of sensory or motor blockade. The B2 treatment produced a higher degree of sensory blockade compared to B1 and B3 for both lumbar and sciatic dermatomes. There was no significant difference in the degree of sensory blockade comparing B1 to B3. The B2 treatment had greater motor blockade compared to B1 and B3. The duration of sensory and motor blockade was longer in B2 compared to B1 and B3.Conclusion and clinical relevanceWhen the nerve stimulator is used to perform the lumbosacral plexus block, the concentration of the bupivacaine has a more important role than the volume to produce a more solid and longer block.     

Assessment of brachial plexus blockade in chickens by an axillary approach

ObjectiveTo assess the brachial plexus block in chickens by an axillary approach and using a peripheral nerve stimulator.Study designProspective, randomized, double-blinded study.AnimalsSix, 84-week old, female chickens.MethodsMidazolam (1 mg kg⁻¹) and butorphanol (1 mg kg⁻¹) were administered into the pectoralis muscle. Fifteen minutes later, the birds were positioned in lateral recumbency and following palpation of the anatomic landmarks, a catheter was inserted using an axillary approach to the brachial plexus. Lidocaine or bupivacaine (1 mL kg⁻¹) was injected after plexus localization by the nerve stimulator. Sensory function was tested before and after blockade (carpus, radius/ulna, humerus and pectoralis muscle) in the blocked and unblocked wings. The latency to onset of motor and sensory block and the duration of sensory block were recorded. A Friedman nonparametric one-way repeated-measures anova was used to compare scores from baseline values over time and to compare the differences between wings at each time point.ResultsA total of 18 blocks were performed with a success rate of 66.6% (12/18). The latency for motor block was 2.8 ± 1.1 and 3.2 ± 0.4 minutes for lidocaine and bupivacaine, respectively. The latencies for and durations of the sensory block were 6.0 ± 2.5 and 64.0 ± 18.0 and 7.8 ± 5.8 and 91.6 ± 61.7 minutes for lidocaine and bupivacaine, respectively. There was no statistical difference between these times for lidocaine or bupivacaine. Sensory function was not abolished in nonblocked wings.Conclusions and clinical relevanceThe brachial plexus block was an easy technique to perform but had a high failure rate. It might be useful for providing anesthesia or postoperative analgesia of the wing in chickens and exotic avian species that have similar wing anatomy.     

Determination of angiotensin I-converting enzyme activity in equine blood: lack of agreement between methods of analysis

Angiotensin-I converting enzyme (ACE) is a key regulator of blood pressure, electrolytes and fluid homeostasis through conversion of angiotensin I into angiotensin II. Recently, a genetic polymorphism of the ACE gene, which accounts for 47% of the variation of ACE activity in blood, has been advocated as a biomarker of athletic aptitude. Different methods of analysis and determination of ACE activity in plasma have been used in human and equine research without a consensus of a "gold standard" method. Different methods have often been used interchangeably or cited as being comparable in the existing literature; however, the actual agreement between assays has not been investigated. Therefore, in this study, we evaluated the level of agreement between three different assays using equine plasma obtained from 29 horses. Two spectrophotometric assays using Furylacryloyl-phenylalanyl-glycyl-glycine as substrate and one fluorimetric assay utilizing o-aminobenzoic acid-FRK-(Dnp)P-OH were employed. The results revealed that the measurements from the different assays were not in agreement, indicating that the methods should not be used interchangeably for measurement of equine ACE activity. Rather, a single method of analysis should be adopted to achieve comparable results and critical appraisal of the literature is needed when attempting to compare results obtained from different assays.     

Bovine mixed leukocyte response: effect of selected parameters on cell responses

The bovine mixed leukocyte culture (MLC) system offers potential benefit for the study of genetic and immunologic mechanisms in this species. Selected parameters of the bovine MLC have been investigated to assess their influence. The findings indicate that maximal MLC response was present at days 5 and 6 with 2 x 10(5) responder to 2 x 10(5) stimulator cells per well or greater. Serum concentrations over a wide range effectively supported cell growth. More importantly, the source and treatment of serum influenced the level of MLC response. Serum autologous to the responder which was heat treated appeared to provide maximal MLC values compared to other sources examined. Antisera to serologically-defined lymphocyte antigens of the stimulating cell population did not affect the response. One-way MLC determinations were consistent when the stimulating cell population was irradiated at 1,000 Rads or greater. Both freshly obtained lymphocytes and lymphocytes held at room temperature for 18 hr provided good sources of MLC responder and stimulator cells; however, lymphocytes held for 18 hr consistently gave higher counts and stimulation indices than freshly obtained lymphocytes. The effect of contaminating RBCs was found to enhance MLC reactivity at lower concentrations and inhibit MLC reactivity when in excess of 7 X 10(9) RBC per well. Stimulator cells were present in both macrophage enriched and depleted populations suggesting several cell populations possess antigens which lymphocytes recognize. Consideration of these parameters were essential in providing optimal, reproducible results.     

Influence of polychlorinated biphenyls on the secretion of oxytocin from bovine luteal cells and from granulosa cells obtained from the follicles of different size

Effect of polychlorinated biphenyles (PCBs) on viability and secretory function of luteal and granulosa cells from mature cows was studied. Luteal cells from corpora lutea of different developmental stages and granulosa cells from follicles of >1 cm< in diameter were used. Neither individual congeners (PCB-126, -77, -153) nor mixture of PCBs Aroclor Ar) 1248 at the dose of 1, 10 or 100 ng/ml affected the viability of cells (P>0.05) compared to control after 72 h of incubation. PCBs markedly increased (P<0.05-0.001) oxytocin (OT) secretion from granulosa cells. This effect was the most evident when granulosa cells from follicles <1 cm diameter was treated with PCB-77 which is assumed to stimulate both arylhydrocarbon receptor (AhR) and estradiol (E2) receptor. Even the lowest dose of this compound (1 ng/ml) outranged the effect produced by cortisol (10(-5)M) used as positive control. There was marked effect (P<0.05-0.001) of PCBs on luteal cells from days 6-15 of the estrous cycle. However, influence of PCBs on OT secretion from luteal cells on day 1-5 and 16-18 of the estrous cycle was less evident. Again, PCB-77 was the most efficient stimulator of OT secretion. While the lowest effect was found after treatment of cells with PCB-126 which has dioxin-like properties. It can be assumed that diverse effect of PCBs on female reproduction largely results from the influence of these compounds on ovarian OT secretion. Since both synthesis and secretion of ovarian OT in bovine do not markedly depend on estradiol, some alternative cellular pathways of PCBs on ovary function are suggested.     

Apparent clinical resolution of pinnal actinic keratoses and squamous cell carcinoma in a cat using topical imiquimod 5% cream

Imiquimod is a topical immune response modifier and stimulator used in humans to treat a number of cutaneous neoplasms. This case report describes a cat with actinic keratoses and squamous cell carcinoma of the pinnae. The pinnal lesions were treated with topical 5% imiquimod three times per week. Treatment was discontinued after 82 days of therapy. Twelve weeks of topical imiquimod application resulted in clinical resolution of the pinnal lesions. Although no post-treatment biopsies were performed, there was no relapse of the pinnal lesions in 5 months of clinical follow-up. Expected side effects were limited to erythema, crusting, alopecia, and mild discomfort at the sites of application during the first 3 weeks of application. These results suggest that topical imiquimod, although unproven, might be a therapeutic option or adjunct to therapy for cats with actinic keratoses and squamous cell carcinoma, especially those cats for whom surgery and radiation therapy are not an option.     

Diagnosis of early pregnancy by testing the progesterone level

Measuring serum or plasma levels of progesterone can be used to determine if conception has occurred in horses. If the mare's progesterone level is below 2 ng/ml 18 days after mating has occurred, conception has not taken place. This method can be used as an addunct to genital examination, and it can be used to determine if hormonal irregularities are present in mares who have not been able to conceive.     

Meat Science and Muscle Biology Symposium: extracellular matrix regulation of skeletal muscle formation

Skeletal muscle development and growth is a complex process that involves the interaction of muscle cells with their extracellular environment. Because muscle development involves the interaction of the cell surface and extracellular matrix molecules, research focus has been placed on the proteoglycans. Proteoglycans are macromolecules containing a central core protein with attached carbohydrates, called glycosaminoglycans, that are located at both the cell surface and the extracellular matrix. Research focus has been placed on understanding the mechanisms of the membrane-associated heparan sulfate proteoglycans, syndecan-4 and glypican-1, which are both capable of regulating cellular responsiveness to fibroblast growth factor 2 (FGF2). Fibroblast growth factor 2 is a potent stimulator of muscle cell proliferation and a strong inhibitor of differentiation. Studies on syndecan-4 and glypican-1 show that these proteoglycans differentially regulate muscle cell proliferation, differentiation, and cellular responsiveness to FGF2 with syndecan-4 predominantly modulating muscle cell proliferation and glypican-1 modulating differentiation. Site-directed mutagenesis approaches were used to define the effect of the syndecan-4 and glypican-1 covalently attached side chains on their activity. In general, a functional association was found between the glycosaminoglycan and N-glycosylated chains attached to the central core proteins of syndecan-4 and glypican-1 affecting their regulation of muscle cell proliferation, differentiation, and FGF2 responsiveness. Current research efforts are directed at identifying the cellular signaling pathways modulated by syndecan-4 and glypican-1.     

不同激素处理富源本地黄牛与短本杂一代黄牛同期发情试验

为了比较不同品种的黄牛用不同激素处理后的同期发情效果,以筛选出适合本地不同牛群及环境的较优杂交方案.将137头健康空怀黄母牛(其中本地黄母牛72头,短本杂一代黄母牛65头)分为4个组,第1、2组为本地黄母牛,第3、4组为短本杂一代黄母牛,分别用2种不同的方法进行同期发情处理.第1、3组注射三合激素;第2、4组注射促排3号-氯前列烯醇-促排3号.结果表明,第1组、第2组、第3组、第4组经不同的激素处理后,发情率分别为59.38%、87.5%、58.62%、86.11%,第2组的发情率显著高于第1组(P＜0.05),第4组的发情率显著高于第3组(P＜0.05),而第1组和第3组、第2组和第4组的发情率差异不显著(P＞0.05).结果提示发情率的高低与品种的相关性不大,促排3号-氯前列烯醇-促排3号可能是较适合富源黄母牛的同期发情方案.     

The value of embryo transfer to cattle breeding in Britain

An analysis is made of the maximum expenditure which could be justified in embryo transfer in cattle is used to: increase the rate of genetic improvement of dairy or beef cattle; increase the frequency of twin-pregnancies; and expedite a change of breed. Estimates of maximum justifiable expenditure have been compared with an estimate of the cost of non-surgical transfer. Embryo transfer should be used in elite beef herds to increase selection intensity, particularly if bulls from such herds can be used for artificial insemination. Other commercial applications will not be economically justifiable until the cost of transfer has fallen by 50 to 80 per cent.     

Current Reproductive Technologies Impacting Equine Embryo Production

Numerous reproductive technologies have been developed in the past several decades, which have dramatically changed the way mares are bred. This review will focus on embryo recovery and transfer, cooled-shipped embryos, embryo freezing, oocyte freezing, oocyte collection and transfer, intracytoplasmic sperm injection (ICSI), and sexed semen. Embryo transfer procedures have been constant for many years and the costs have not changed. The major change has been the ability to store embryos at 5 C for 12–24 hours and transport them to recipient stations. Embryo freezing has become more common using the technique of vitrification of embryos >300 μm or deflating embryos >300 μm before freezing. Oocyte vitrification has resulted in poor pregnancy rates although the technique works well in women. The ability to collect oocytes from mares and fertilize them by sperm injection has revolutionized the veterinarian’s approach to infertility in the mare and/or stallion. A transvaginal approach can be used to collect oocytes from preovulatory follicles and unstimulated follicles 5–25 mm in size. Although traditional in vitro fertilization does not work well in the horse, ICSI can be used to produce blastocysts which, upon nonsurgical transfer into recipients, provide a pregnancy rate similar to fresh embryos collected from donor mares. Sorting sperm by flow cytometry into X- and Y-bearing spermatozoa has been shown to provide about a 50% pregnancy rate with freshly sorted sperm but only 12% with sorted, frozen/thawed stallion sperm. It is likely that more advanced reproductive techniques will be developed in the future. Their acceptance will depend on how well they work, perceived need, cost, and, to some extent, the breed associations.