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.

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.

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.

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.

Spinal anesthesia. Volume or concentration--what matters?

BACKGROUND AND OBJECTIVES: An investigation was made of the effects of volume and concentration of a constant dose of subarachnoid lidocaine on the extent and duration of sensory and motor anesthesia produced, as well as of the lidocaine concentration of the cerebrospinal fluid (CSF) as a function of time. METHODS: In a prospective study, 40 American Society of Anesthesiologists (ASA) status 2 or 3 patients were assigned to one of five groups, who received a 70-mg subarachnoid dose of lidocaine hydrochloride as a 0.5, 1, 2, 5, or 10% solution. Dural puncture was performed at the L3-L4 interspace with a 19.5-gauge Periquick needle (Pajunk, Germany), and a 24-gauge catheter was inserted 3-4 cm into the subarachnoid space. The patient remained in the lateral position during injection of the local anesthetic and was then turned to the supine horizontal position. The level of anesthesia and the motor block were measured at 5, 10, 15, 20, 30, 40, 50, and 60 minutes and then at 15-minute intervals until the effect of the anesthesia had ceased. Samples of CSF were collected at the same times that the pinprick and motor block measurements were made. RESULTS: Five minutes after injection, a median sensory block height of T4 or T5 was observed in all groups. The range of mean total times to complete recovery of the sensory blocks was 139-152 minutes, while that for the motor blocks of the lower extremities was 100-122 minutes. The values were similar in all groups (P > .05). The motor block was complete in all patients 10 minutes after the lidocaine injection. Five minutes after injection, the mean CSF lidocaine concentration was highest in the 10% group (P < .001 vs. the other four groups). At 15 minutes, the only statistical difference was found between the 0.5% and the 10% group (P = .026). At 20 minutes, the CSF lidocaine concentrations were similar in all groups (P > .05). CONCLUSIONS: A constant 70-mg dose of subarachnoid lidocaine produced the same pinprick level of analgesia, degree of motor block, and duration of spinal anesthesia in spite of being injected over an extremely broad range of concentrations and volumes. Despite the fact that all patients received the same dose of lidocaine, the CSF concentrations at 5, 10, and 15 minutes were different and directly related to the concentration of the solution injected. at 20 minutes, the CSF concentrations were similar in all groups. These results indicate a relatively uniform distribution of lidocaine in the CSF for all solutions tested.

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.

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.

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.