Inbreeding in the Thoroughbred horse.

Changes in the inbreeding coefficient, F, in the Thoroughbred horse over the past 45 years have been investigated by genotyping 467 Thoroughbred horses (born between 1961 and 2006) using the Illumina Equine SNP50 bead chip, which comprises 54,602 SNPs uniformly distributed across the equine genome. The Spearman rank correlation coefficient, r, between the year of birth and F was estimated. The results indicate that inbreeding in Thoroughbreds has increased over the past 40 years, with r = 0.24, P < 0.001 demonstrating that there is a highly significant, though relatively weak correlation between the year of birth and inbreeding coefficients. Interestingly, the majority of the increase in inbreeding is post-1996 and coincides with the introduction of stallions covering larger numbers of mares.

Identification of the myostatin locus (MSTN) as having a major effect on optimum racing distance in the Thoroughbred horse in the USA.

One hundred and eighty-nine Thoroughbred horses that had won Graded Stakes races in North America were genotyped with the Illumina Equine SNP50 bead chip. Association tests using PLINK to determine whether any SNPs were associated with optimum racing distance (7 furlongs and under compared to 8-10 furlongs) identified a locus on ECA18 that was statistically significant (-log 10 EMP2=1.63) at the genome-wide level following permutation analysis (10,000 permutations). Bioinformatic analysis revealed that the two ECA18 SNPs with the highest statistical significance spanned the MSTN (myostatin) locus. Mutations in myostatin in several mammalian species have been associated with increased muscling, with a preferential increase in fast glycolytic type IIB fibres, which would increase power potential. Thoroughbred horses that race over sprint distances, which are 5-7 furlongs, are often characterized by impressive hind quarter musculature, strongly suggesting that the association observed between the ECA18 SNPs and optimum race distance is mediated through MSTN.

Influence of polyvalent cations on the activation of muscle end plate receptors.

The influence of polyvalent cations on the activation of end plate receptors has been studied in vitro on the sartorius muscle of the frog. In the absence of extracellular calcium, the sensitivity of the receptors to depolarizing quaternary ammonium salts was markedly reduced. Maximum receptor activation occurred in those fibers equilibrated in 1.8 mM calcium Ringer solution, with the response being reduced as the calcium concentration was raised or lowered. Magnesium was less efficient than calcium in regulating the sensitivity of the end plate receptors, the maximum receptor response occurring in those fibers equilibrated in 8 mM magnesium Ringer solution. In the presence of lanthanum the end plate response to carbamylcholine or acetylcholine was enhanced. Lanthanum increased the conductance change produced by carbamylcholine both in polarized and in potassium-depolarized fibers. The application of 10(-2) mM lanthanum to the end plate increased MEPP's amplitude, rise time, and half-fall time by 19, 54, and 45%, respectively. The results suggest that polyvalent cations influence postjunctional membrane receptor processes in addition to their well-documented prejunctional action.

Steroid treatment for experimental autoimmune myasthenia gravis.

Short-term, high-dose steroids (prednisolone sodium succinate) were given to female Lewis rats in the chronic stage of experimental autoimmune myasthenia gravis (EAMG). Abnormally low amplitude miniature endplate potentials (MEPPs) persisted, and were even slightly lower than those seen in saline-treated animals with chronic EAMG. The MEPPs were also studied in normal female Lewis rats treated with short-term, high-dose steroids, and no significant change was noted when compared with normal controls. Previous investigators have reported normalization of the abnormally low amplitude MEPPs within 24 hours of high-dose steroid treatment. Our different results might be explained by our higher dose of receptor, addition of pertussis to the inoculum, and study of a different muscle. A survey of endplate ultrastructure revealed some definite postsynaptic membrane abnormalities in both steroid-treated and saline-treated rats with EAMG, but clear distinction among the groups studied was not possible by direct visualization.

First Report of Potato mop-top virus on Potato from the United States.

Potato mop-top virus (PMTV) is a tripartite pomovirus vectored by the powdery scab plasmodiophoromycete Spongospora subterranea pv. subterranea (1). PMTV occurs on potato (Solanum tuberosum) in Europe, the Andes, Asia, and Canada. Internal necrotic arc and fleck tuber symptoms ("spraing") may reduce commercial acceptance of some cultivars (3). PMTV symptoms were discovered in 'Shepody' tubers at the Aroostook Research Farm, Presque Isle, ME in May 2002 and subsequently in 'Russet Burbank' tubers in commercial storage from the 2001 Maine crop. Symptomatic tubers exhibited single or multiple concentric necrotic arcs that were partial or complete, but exhibited no distinct external symptoms. The presence of PMTV in eight 'Shepody' tubers was indicated by positive enzyme-linked immunosorbent assay (ELISA; Adgen, Ltd., Auchincruive, Ayr, Scotland) and confirmed by reverse transcription polymerase chain reaction (RT-PCR). 'Russet Burbank' potatoes were visually diagnosed, and the corresponding halves of 128 symptomatic tubers were forwarded to the University of Maine and APHIS (Beltsville, MD). Of these, ELISA readings in Maine were strongly positive (>3 × background) for 88, ambiguous (1.5-3 × background) for 13, and negative for 27. Subsamples from these three categories were positive by PCR in 17 of 17, 9 of 9, and 12 of 14 cases, respectively. A similar rating, positive or ambiguous, in ELISA testing was identical for all but one case at Beltsville. Confirmation of PMTV required PCR testing, resulting in a characteristic PCR product of 401 bp that was generated from the coat protein coding region on RNA 2 (2) using the primer pair PMTV 1 5'-GCAGCCGTCGAGAATAGATA-3' (RNA nucleotides 316-335) and PMTV 4 5'-GCGAGTTGATGTGCC ACATT-3' (complementary to RNA 2 nucleotides 716-697). An immunocapture RT-PCR using this primer set and the coating antibody from the Adgen ELISA kit was also successful in detecting PMTV. In separate reactions, a second product of 646 bp was generated from the triple gene block on RNA 3 (4) using the primer pair PMTV 5 5'-GGTGAACACGAGGACAAGGT-3' (RNA 3 nucleotides 1417-1436) and PMTV 7 5'-AACAGTCCGGTCTTGTGAAC-3' (complementary to RNA 3 nucleotides 2063-2044). The sequence of these products was 98 to 100% identical to PMTV published sequences. The discovery of this virus will result in adjustments to U.S. and Canadian seed potato certification standards and symptom characterization for common North American cultivars. References: (1) R. A. C. Jones and B. D. Harrison. Ann. Appl. Biol 63:1, 1969. (2) S. Kashiwazak et al. Virology 206:701, 1995. (3) M. Sandgren et al. Am. J. Potato Res. 79:205, 2002. (4) K. P. Scott et al. J. Gen. Virol.75:3561, 1994.

First Report of White Mold (Sclerotinia sclerotiorum) on Soybean in Maine.

White mold or Sclerotinia stem rot (Sclerotinia sclerotiorum (Lib) de-Bary) was first observed on soybean varieties in a variety trial at the Maine Agricultural and Forest Experiment Station, Presque Isle, and in commercial soybean fields in late July and August 1997. Symptoms and signs included stem bleaching, fluffy white mycelial growth on soybean stems and foliage, and presence of sclerotia typical of white mold. Disease assessment, based on symptoms, was conducted on the varieties in the trial in the experiment station. Field observations on disease occurrence were also conducted in commercial soybean fields in northern Maine. In the variety trial experiment, mean incidence (%) of white mold ranged from 0 to 6.8% on Lambert, APK007, P9092, P9132, and Stine varieties. No white mold was detected on P9071, P9007, Korada, Bravor, Ugo, APK020, and Aquillon varieties. Of the infected varieties, incidence of white mold was detected in 10 of 33 fields examined. This is the first report of the occurrence of white mold on soybean in Maine. Because of large-scale commercial potato production in the region, and previous occurrence of white mold on potato, it is likely that the pathogen is present in soils of various commercial potato fields in Maine. Precautions should, therefore, be taken in introducing resistant varieties and ensuring proper rotation and cropping sequences as soybean production increases in Maine.

Recommendation for the conservation of the name Streptomyces scabies. Request for an Opinion.

The primary streptomycete inciting common scab of potato was first legitimately described by Thaxter in 1892 as 'Oospora scabies', preserving the spelling of an epithet in use since 1846. The name Streptomyces scabies, dating to 1948, was revived in 1989, but changed to Streptomyces scabiei in 1997 to follow grammatical convention. Considering the long-established use and general recognition of 'scabies', it is proposed that the original epithet be conserved.

Warming 0.5% bupivacaine to 37 degrees C increases duration of spinal anesthesia.

The effect of warming glucose-free 0.5% bupivacaine to 37 degrees C before injection for spinal anesthesia was studied in 20 patients having total knee replacement. Twenty additional patients having spinal anesthesia for the same procedure were given glucose-free 0.5% bupivacaine at room temperature (approximately 20 degrees C). Onset, maximum cephalad spread, quality of sensory anesthesia, and duration and degree of motor blockade were the same in both groups. However, the duration of sensory anesthesia was significantly prolonged in patients who received bupivacaine at 37 degrees C. The mechanism by which warming bupivacaine prolongs the duration of sensory spinal anesthesia is uncertain. However, a decrease in the dissociation constant (pKa) of bupivacaine owing to increasing the temperature to 37 degrees C may account for some of this effect.

Photoheterotrophic growth of Agmenellum quadruplicatum PR-6.

The unicellular cyanobacterium Agmenellum quadruplicatum PR-6 grows in the presence of light on agar containing 10 microM 3-(3,4 dichlorophenyl)-1,1-dimethylurea and 1 to 30 mM glycerol. A derivative strain, PR-6G2, was tolerant of 100 mM glycerol. Photoheterotrophic growth conditions had little effect on transformation competence but did decrease the viability of single cells plated onto agar, particularly cells of the parent strain.

The search for an optimal interval between pretreatment dose of d-tubocurarine and succinylcholine.

A study was conducted to determine the optimal interval between the administration of d-tubocurarine (dTc) and succinylcholine (SCh) with regard to onset and duration of neuromuscular block and presence of fasciculations and postoperative myalgias. Forty female patients received dTc 3 mg X 70 kg-1 prior to SCh 1.5 mg X kg-1. The interval between drugs was 0, 1, 3, 5, or 7 minutes. Transduced thumb adduction recorded block onset and recovery. Fasciculations were visually detected. Myalgias were assessed on postoperative interview. Pretreatment interval did not affect the onset or recovery of neuromuscular block. Postoperative myalgias were also independent of pretreatment timing. Fasciculations were blocked with 3, 5, or 7 minute intervals, but not with 0 or 1 minute intervals. Therefore, three minutes appear to be the optimal time interval between administration of dTc and SCh since shorter intervals do not inhibit fasciculations and longer intervals do not afford any additional advantages.

Anesthesia and the control of blood pressure in patients with spinal cord injury.

The medical records of 78 procedures performed on 50 spinal cord injured patients at risk for developing autonomic hyperreflexia were evaluated for blood pressure changes during anesthesia and surgery. Hypertension was arbitrarily defined as a systolic blood pressure of greater than 140 torr. The 78 procedures were divided into three groups: group A, 19 procedures in which the patient received topical anesthesia, sedation, or no anesthesia; group B, 13 procedures conducted under general anesthesia; and group C, 46 procedures carried out under spinal anesthesia. Hypertension occurred in 15 of 19 procedures (79%) in group A, in three of 13 procedures (23%) in group B, and in three of 46 procedures (7%) in group C. Group A differed significantly from group B (p = 0.011) and group C (p = 1.2 X 10(-8)). There was no significant difference between groups B and C (p = 0.114). Results indicate that patients at risk for autonomic hyperreflexia are protected from developing intraoperative hypertension by either general or spinal anesthesia.

Irreversible conduction block in isolated nerve by high concentrations of local anesthetics.

BACKGROUND: Delivery of large doses of local anesthetics for spinal anesthesia by repeated injections or continuous infusion could expose the cauda equina to concentrations of drug that may be neurotoxic per se. We studied this possible neurotoxic effect by assessing recovery from conduction blockade of desheathed peripheral nerves after exposure to some of the local anesthetic solutions commonly used for spinal anesthesia. METHODS: The reversibility of conduction blockade was studied in desheathed bullfrog sciatic nerves, using the sucrose-gap method for recording compound action potentials, before and during exposure to local anesthetics and during drug washout. The nerves were exposed for 15 min to 5% or 1.5% lidocaine, with or without 7.5% dextrose; 0.5% tetracaine; or 0.75% bupivacaine (the latter two without dextrose). Some nerves were also bathed in 7.5% dextrose (without local anesthetic) or in 0.06% tetracaine, which in this preparation is equipotent to 5% lidocaine. After 15 min in the drug, the nerves were washed for 2-3 h and soaked in Ringer's solution overnight. Nerves exposed only to Ringer's solution served as controls. We also studied neuronal uptake and washout of radiolabeled lidocaine. RESULTS: Exposure of nerves to 5% lidocaine, with or without 7.5% dextrose, or to 0.5% tetracaine resulted in irreversible total conduction blockade, whereas 1.5% lidocaine or 0.75% bupivacaine caused 25-50% residual block after the 2-3 h wash. Nerves exposed to Ringer's solution, 7.5% dextrose or 0.06% tetracaine had 0-10% residual block after 2-3 h wash. The action potential of all nerves declined after overnight soak to between 30-60% of the control value, except for those nerves exposed to 5% lidocaine or 0.5% tetracaine, which showed no activity. Exposure to 5% lidocaine for periods of only 4-5 min produced total, irreversible loss of conduction. The uptake by and washout of radiolabeled lidocaine from the nerves indicate that the maximum amount of residual drug after 2-4 min of exposure to 5% lidocaine and a 3-h wash should cause at most only 50% conduction block. CONCLUSIONS: Solutions of 5% lidocaine and 0.5% tetracaine that have been associated with clinical cases of cauda equina syndrome after continuous spinal anesthesia caused irreversible conduction block in desheathed amphibian nerve. Whether these in vitro actions also occur in mammalian nerves in vivo is an important, clinically relevant question now under investigation in our laboratory.

Effect of pregnancy on bupivacaine-induced conduction blockade in the isolated rabbit vagus nerve.

Bupivacaine-induced conduction blockade of A, B, and C fibers of the isolated vagus nerve was compared in fourteen pregnant and fourteen nonpregnant rabbits. After a control period in HEPES-Liley solution, the isolated nerves were exposed to bupivacaine concentrations of 0.1 mM to 1.0 mM. After 30 min exposure, the nerves were stimulated supramaximally and the percent reduction in amplitude of A, B, and C fiber compound action potentials was recorded. Linear regressions were fitted by the least squares method. The A fiber conduction blockade was consistently greater in the nerves from pregnant rabbits (P less than 0.001). The slope of the C fiber dose-response curves was also significantly greater in nerves from pregnant rabbits (P less than 0.01). The results indicate that the response of isolated nerves from pregnant animals to local anesthetic-induced conduction blockade differs from that of nerves from nonpregnant animals. However, it is not certain whether the difference is related simply to a more rapid diffusion and shorter onset of block or an enhanced sensitivity of the nerve membrane during pregnancy.

Tourniquet pain during spinal anesthesia: a comparison of plain solutions of tetracaine and bupivacaine.

The incidence of tourniquet pain was evaluated in 40 patients having orthopedic surgery of the lower extremities during spinal anesthesia using 15 mg of a plain solution of either 0.5% tetracaine or 0.5% bupivacaine. The drugs were administered in a randomized fashion, and measurement of the levels of sensory anesthesia to pinprick and motor blockade as well as the occurrence of tourniquet pain were made by an independent blinded observer. The onset and maximum cephalad spread of sensory anesthesia and the onset and degree of motor block were similar in both groups of patients. However, the duration of sensory anesthesia was significantly longer in patients in whom tetracaine was used. The incidence of tourniquet pain was significantly greater in patients given tetracaine (60%) than in patients given bupivacaine (25%). The occurrence of tourniquet pain was not related to the level of sensory anesthesia, because patients in the tetracaine group had a higher level of sensory anesthesia (mean T6) than did patients in the bupivacaine group (mean T10) at the onset of tourniquet pain. It is speculated that during spinal anesthesia both A and C fibers (mediating fast and slow pain, respectively) are initially equally inhibited. However, as the concentration of local anesthetic in the cerebrospinal fluid declines, C fibers may become unblocked earlier with tetracaine than A fibers, resulting in tourniquet pain in the presence of an otherwise satisfactory spinal anesthetic.

Role of needle gauge and tip configuration in the production of lumbar puncture headache.

BACKGROUND AND OBJECTIVES: Postdural puncture headache (PDPH) is a morbidity that occurs frequently after lumbar puncture. The purpose of this study was to evaluate the role of needle diameter and tip configuration in causing PDPH. The incidence of PDPH was evaluated in parturients because this group of patients is at high risk for developing PDPH and because they often undergo lumbar puncture for spinal anesthesia. METHODS: The incidence of PDPH after spinal anesthesia with 26- and 27-gauge Quincke and 25-gauge Whitacre needles was studied in a series of 4,125 parturients undergoing spinal anesthesia over a 4-year period. Data were also collected on the incidence of PDPH with 17-gauge Huber-tipped Weiss needles in 21,578 parturients receiving lumbar epidural analgesia and/or anesthesia over the same interval. Additionally, the need to treat PDPH with epidural blood patch in all of these patients was studied. RESULTS: The incidence of PDPH was 5.2% with 26-gauge Quincke needles (1987-1989), 2.7% with 27-gauge Quincke needles (1989-1990), and 1.2% with 25-gauge Whitacre needles (1990-1991). During the same periods, the incidence of PDPH with 17-gauge Weiss needles averaged 1.1%, 1.7% and 1.2%, respectively. As compared with the 26-gauge Quincke needle, there was a lower incidence of PDPH with the 27-gauge Quincke (P < .006) and 25-gauge Whitacre spinal needles (P < .001). The incidence of PDPH with the 25-gauge Whitacre needle was less than that with the 27-gauge Quincke needle (P < .05), and it was similar to the overall rate of headache, which occurs occasionally from accidental dural puncture during the performance of lumbar epidural analgesia/anesthesia for labor and cesarean delivery (P = .974). The need for treating PDPH with epidural blood patching was greatest with the 17-gauge Weiss epidural needle (75.3% of cases), but was similar with the various spinal needles (13-39%). However, because the Whitacre needle produced the fewest PDPHs, it was associated with the lowest absolute requirement for epidural blood patching. CONCLUSIONS: The morbidity associated with lumbar puncture can be decreased by selecting the proper needle gauge and tip configuration. Use of the smallest gauge needle and one that has a noncutting Whitacre tip produces the lowest incidence of PDPH in parturients, a group of patients at increased risk for developing PDPH.

Sensory analgesia for vaginal deliveries: a preliminary report of continuous spinal anesthesia with a 32-gauge catheter.

Our initial experience in providing pain relief during labor and delivery for 20 parturients using a 32-gauge continuous spinal microcatheter using 1% lidocaine is described. The technique significantly reduced the pain of labor, which was assessed as severe by 18 of the patients, and provided adequate perineal anesthesia for vaginal delivery with 18 patients indicating pain during delivery to be minimal. The major advantage of continuous spinal anesthesia is the ability to rapidly establish sensory anesthesia with the flexibility to reinject additional local anesthetic should a complete sensory or sensory and motor block be required for forceps or cesarean delivery. Technical difficulty was the main disadvantage with the use of the 32-gauge microcatheter. An inability to thread the catheter (two patients) through the 26-gauge spinal needle or kinking of the catheter (two patients) making injection impossible, and unintentional catheter removal (one patient) resulted in a 25% failure rate with this technique.

Effects of oral caffeine on postdural puncture headache. A double-blind, placebo-controlled trial.

Forty postpartum patients with postdural puncture headache (PDPH) were randomly assigned to receive oral caffeine (300 mg) or a placebo. Intensity of headache, quantitated using a visual analogue pain scale (VAS), was assessed immediately before drug administration and 4 and 24 h later. Relief of PDPH measured as delta VAS (initial VAS - VAS at 4 h) was significantly better in the caffeine than in the placebo group (P = 0.014). Six patients (30%) whose PDPH was relieved by caffeine at 4 h had recurrence of symptoms the following day. Our study demonstrates that caffeine administered orally provides relief, albeit if sometimes transient, from PDPH with minimal side effects.