The rectus abdominis muscle advancement flap as a salvage option for chest wall reconstruction

We describe a previously unreported technique of advancing the rectus abdominis muscle superiorly, based on the deep inferior epigastric artery, to cover a lower anterior chest wall defect. This technique represents an important salvage option for chest wall reconstruction and affords a great deal of intra-operative flexibility.

Relationship of thyroid transcription factor 1 to EGFR status in non-small-cell lung cancer

BACKGROUND

Activating mutations of the epidermal growth factor receptor (EGFR) gene are known to drive a proportion of non-small-cell lung cancers. Identification of lung cancers harbouring such mutations can lead to effective treatment using one of the agents that targets and blocks egfr-mediated signalling.

METHODS

All specimens received at the BC Cancer Agency (Vancouver) for EGFR testing were prospectively identified and catalogued, together with clinical information and EGFR status, over a 14-month period.

RESULTS

Specimens from 586 patients were received for EGFR testing, and EGFR status was reported for 509 patients. No relationship between specimen type or site of origin and EGFR test failure rate was identified. Concurrent immunohistochemical (ihc) status for thyroid transcription factor 1 (ttf1) was available for 309 patients. The negative predictive value of ttf1-negative status by ihc was 94.2% for predicting negative EGFR status.

CONCLUSIONS

In patients with limited tissue available for testing, a surrogate for EGFR status would aid in timely management. Immunohistochemistry for ttf1 is readily available and correlates highly with EGFR status. In conjunction with genetic assays, ttf1 could be used to optimize an EGFR testing strategy.

Adverse outcome analyses of observational data: assessing cardiovascular risk in HIV disease

Clinical decisions are ideally based on randomized trials but must often rely on observational data analyses, which are less straightforward and more influenced by methodology. The authors, from a series of expert roundtables convened by the Forum for Collaborative HIV Research on the use of observational studies to assess cardiovascular disease risk in human immunodeficiency virus infection, recommend that clinicians who review or interpret epidemiological publications consider 7 key statistical issues: (1) clear explanation of confounding and adjustment; (2) handling and impact of missing data; (3) consistency and clinical relevance of outcome measurements and covariate risk factors; (4) multivariate modeling techniques including time-dependent variables; (5) how multiple testing is addressed; (6) distinction between statistical and clinical significance; and (7) need for confirmation from independent databases. Recommendations to permit better understanding of potential methodological limitations include both responsible public access to de-identified source data, where permitted, and exploration of novel statistical methods.

The association of folate, zinc and antioxidant intake with sperm aneuploidy in healthy non-smoking men

BACKGROUND

Little is known about the effect of paternal nutrition on aneuploidy in sperm. We investigated the association of normal dietary and supplement intake of folate, zinc and antioxidants (vitamin C, vitamin E and beta-carotene) with the frequency of aneuploidy in human sperm.

METHODS

Sperm samples from 89 healthy, non-smoking men from a non-clinical setting were analysed for aneuploidy using fluorescent in situ hybridization with probes for chromosomes X, Y and 21. Daily total intake (diet and supplements) for zinc, folate, vitamin C, vitamin E and beta-carotene was derived from a food frequency questionnaire. Potential confounders were obtained from a self-administered questionnaire.

RESULTS

After adjusting for covariates, men with high folate intake (>75th percentile) had lower frequencies of sperm with disomies X, 21, sex nullisomy, and a lower aggregate measure of sperm aneuploidy (P <or= 0.04) compared with men with lower intake. In adjusted continuous analyses, total folate intake was inversely associated with aggregate sperm aneuploidy (-3.6% change/100 microg folate; 95% CI: -6.3, -0. 8) and results were similar for disomies X, 21 and sex nullisomy. No consistent associations were found between antioxidant or zinc intakes and sperm aneuploidy.

CONCLUSIONS

Men with high folate intake had lower overall frequencies of several types of aneuploid sperm.

Life and death decisions: the role of the IAPs in modulating programmed cell death

Multicellular organisms have evolved elaborate signal transduction pathways for maintaining homeostasis through the control of cell proliferation and death. The recent surge of interest in the regulation of programmed cell death has led to the rapid identification of many proteins involved in controlling and executing apoptosis. The inhibitors of apoptosis proteins (IAPs) constitute a family of highly conserved death suppressing proteins that were first identified in baculoviruses, and that has recently expanded to include at least two homologues in Drosophila melanogaster and four in rodents and humans. In this article we review the current state of IAP research. Two of the IAPs, HIAP-1 and HIAP-2, have been placed within the TNFalpha induced cell death pathway which involves two receptors for TNFalpha and multiple, overlapping signal transduction proteins. A third, X-linked gene termed XIAP, is ubiquitously expressed and appears to have a broad range of suppressor activity to a variety of apoptotic triggers. The fourth member, NAIP, has been identified as the protein product of a candidate gene for the inherited neuromuscular disorder, spinal muscular atrophy (SMA). The neuroprotective activity of NAIP in an in vivo model of cerebral ischemia has also been demonstrated.

The effects of body fat on pulmonary function and gas exchange in cynomolgus monkeys

Obesity adversely affects lung function in humans often reducing arterial blood oxygenation. To determine if obesity adversely affects lung function in cynomolgus monkeys, which is a species that is often used for pulmonary research, pulmonary mechanics, ventilation, functional residual capacity (FRC), and arterial blood gases were measured using spontaneous respiration and on mechanical ventilation with room air or 100% O(2). Body fat percentage was measured by dual energy X-ray absorption. Blood leptin levels were measured by radioimmune assay. Obese monkeys breathed faster with lower tidal volume, but pulmonary resistance and dynamic lung compliance did not change with body fat. FRC and blood leptin were, respectively, negatively and positively correlated with percent body fat. FRC correlated moderately with ventilatory parameters and strongly with arterial oxygen tension, alveolar-arterial oxygen difference and venous admixture. Therefore, obesity in cynomolgus monkeys had marked, deleterious effects on FRC, ventilation and arterial oxygenation. Obesity may be an important confounding variable in lung function studies in primates.

Cystic fibrosis screening in newborns: results from existing programs

Newborn screening for cystic fibrosis (CF) provides early identification and initiation of treatment to infants with this fatal and often misdiagnosed genetic disease. Although reports of health benefits continue to mount from decade-old screening programs in Wisconsin, France, and Australia, newborn screening for CF is still a highly debated topic in genetic policy development. This article summarizes the literature published between May 2000 and April 2001 regarding the health benefits, risks, cost-effectiveness, and programmatic issues of newborn screening for CF. The literature consistently shows evidence of benefits and lack of harm from newborn screening for CF.

Genomic organization of the X-linked inhibitor of apoptosis and identification of a novel testis-specific transcript

Here we report the genomic organization and mapping of the X-linked inhibitor of apoptosis gene (BIRC4, also known as XIAP and hILP) and the identification of a closely related transcript. BIRC4 is located on Xq25 and is composed of seven exons. The intron/exon structure is highly conserved between the mouse homologue and its human counterpart. Four bands cross-react with a BIRC4 coding region probe on a genomic Southern blot. One of these cross-reactive bands encodes an intronless gene that expresses a 2.2-kb transcript solely in the testis. This testis-specific transcript contains a putative open reading frame (ORF) that is homologous to the carboxy-terminal end of BIRC4; overexpression of this ORF shows protective effects against BAX-induced apoptosis.

Statistical decoding of potent pools based on chemical structure

Pooling experiments are used as a cost-effective approach for screening chemical compounds as part of the drug discovery process in pharmaceutical companies. When a biologically potent pool is found, the goal is to decode the pool, i.e., to determine which of the individual compounds are potent. We propose augmenting the data on pooled testing with information on the chemical structure of compounds in order to complete the decoding process. This proposal is based on the well-known relationship between biological potency of a compound and its chemical structure. Application to real data from a drug discovery process at GlaxoSmithKline reveals a 100% increase in hit rate, namely, the number of potent compounds identified divided by the number of tests required.

Assessment of visually lossless irreversible image compression: comparison of three methods by using an image-comparison workstation

PURPOSE

To determine the degree of irreversible image compression detectable in conservative viewing conditions.

MATERIALS AND METHODS

An image-comparison workstation, which alternately displayed two registered and magnified versions of an image, was used to study observer detection of image degradation introduced by irreversible compression. Five observers evaluated 20 16-bit posteroanterior digital chest radiographs compressed with Joint Photographic Experts Group (JPEG) or wavelet-based trellis-coded quantization (WTCQ) algorithms at compression ratios of 8:1-128:1 and x2 magnification by using (a) traditional two-alternative forced choice; (b) original-revealed two-alternative forced choice, in which the noncompressed image is identified to the observer; and (c) a resolution-metric method of matching test images to degraded reference images.

RESULTS

The visually lossless threshold was between 8:1 and 16:1 for four observers. JPEG compression resulted in performance as good as that with WTCQ compression at these ratios. The original-revealed forced-choice method was faster and as sensitive as the two-alternative forced-choice method. The resolution-metric results were robust and provided information on performance above visually lossless levels.

CONCLUSION

The image-comparison workstation is a versatile tool for comparative assessment of image quality. At x2 magnification, images compressed with either JPEG or WTCQ algorithms were indistinguishable from unaltered original images for most observers at compression ratios between 8:1 and 16:1, indicating that 10:1 compression is acceptable for primary image interpretation.

Use of recursive partitioning in the sequential screening of G-protein-coupled receptors

High-throughput screening (HTS) is changing as more compounds and better assay techniques become available. HTS is also generating a large amount of data. There is a need to rationalize the HTS process, because, in some cases, the screening of all available compounds is not economically feasible. In addition to the selection of promising compounds, there is a need to learn from the data that we collect. In this paper, we use a data-mining method, recursive partitioning, to help uncover and understand structure-activity relations and to help biology and chemistry experts make better decisions on which compounds to screen next and better characterize. The sequential-screening process is presented and the results of applying that process to 14 G-protein-coupled receptor assays are reported.

Eotaxin and nitric oxide production as markers of inflammation in allergic cynomolgus monkeys

BACKGROUND

Cynomolgus monkeys have a natural hypersensitivity to Ascaris suum antigen. Inhalation of antigen produces immediate and delayed allergic reactions and an influx of inflammatory cells into the lungs. This study investigated the production of nitric oxide (NO) and the chemokine eotaxin during this allergic response. The effect of bronchoscopy alone on lung inflammatory cells was also investigated along with the time course of the eosinophil influx into the lung.

METHODS

Allergic cynomolgus monkeys were challenged with antigen. Bronchoalveolar lavage (BAL) was performed before and after challenge, and end-tidal NO was measured before and 24 h after challenge. Eotaxin was measured in the BAL fluid 6, 24 and 72 h after challenge. One group of animals was treated with dexamethasone before challenge to block the influx of cells into the lung.

RESULTS

BLA alone induced an influx of neutrophils, but not eosinophils, into the lung 24 h later. A single antigen challenge produced a marked increase in BAL eosinophils that was apparent at 6 h but increased at 72 h after challenge. The increase at 6 h was largely blocked by dexamethasone. Three antigen challenges produced elevated BAL eosinophil levels that persisted for at least 8 weeks. Eotaxin levels rose dramatically 6 h after challenge and remained the same after 24 h. By 72 h, the eotaxin levels had returned to baseline. The increase in eotaxin at 6 h was nonsignificantly reduced by dexamethasone. Exhaled NO levels doubled 24 h after challenge and were not affected by dexamethasone.

CONCLUSIONS

Eotaxin and NO production were increased after airway challenge in allergic monkeys. The rise in NO was not blocked by dexamethasone. The effects of bronchoscopy on the BAL can be avoided by using alternate lungs on consecutive occasions. Eosinophils persist in the BAL for many weeks after antigen challenge.

Analysis of a large structure/biological activity data set using recursive partitioning

Combinatorial chemistry and high-throughput screening are revolutionizing the process of lead discovery in the pharmaceutical industry. Large numbers of structures and vast quantities of biological assay data are quickly being accumulated, overwhelming traditional structure/activity relationship (SAR) analysis technologies. Recursive partitioning is a method for statistically determining rules that classify objects into similar categories or, in this case, structures into groups of molecules with similar potencies. SCAM is a computer program implemented to make extremely efficient use of this methodology. Depending on the size of the data set, rules explaining biological data can be determined interactively. An example data set of 1650 monoamine oxidase inhibitors exemplifies the method, yielding substructural rules and leading to general classifications of these inhibitors. The method scales linearly with the number of descriptors, so hundreds of thousands of structures can be analyzed utilizing thousands to millions of molecular descriptors. There are currently no methods to deal with statistical analysis problems of this size. An important aspect of this analysis is the ability to deal with mixtures, i.e., identify SAR rules for classes of compounds in the same data set that might be binding in different ways. Most current quantitative structure/activity relationship methods require that the compounds follow a single mechanism. Advantages and limitations of this methodology are presented.

Automated pharmacophore identification for large chemical data sets

The identification of three-dimensional pharmacophores from large, heterogeneous data sets is still an unsolved problem. We developed a novel program, SCAMPI (statistical classification of activities of molecules for pharmacophore identification), for this purpose by combining a fast conformation search with recursive partitioning, a data-mining technique, which can easily handle large data sets. The pharmacophore identification process is designed to run recursively, and the conformation spaces are resampled under the constraints of the evolving pharmacophore model. This program is capable of deriving pharmacophores from a data set of 1000-2000 compounds, with thousands of conformations generated for each compound and in less than 1 day of computational time. For two test data sets, the identified pharmacophores are consistent with the known results from the literature.

Discovery 99: accelerate and improve the drug discovery process. 26-29 April 1999, San Diego, CA, USA

The stated purpose of this conference was the examination of emerging technologies for drug discovery. The meeting was divided into numerous pre- and post-conferences and tracks. A pre-conference workshop examined enabling software and business strategies. Nine tracks covered natural products, high-throughput screening, bioinformatics, proteomics/functional genomics, pharmacogenomics, combichem, chemoinformatics and assay methods. A post-conference symposium covered ADME-toxicology screening. In short, the gamut of drug discovery.

Short duration anaesthesia with medetomidine and ketamine in cynomolgus monkeys

Cynomolgus monkeys were anaesthetized with either intramuscular ketamine (10 mg/kg or intramuscular ketamine 2 mg/kg and medetomidine 50 microg/kg. Various physiological measurements were made once the animals were safe to handle and again 10 min later. Cardiovascular and respiratory function were well maintained with both regimens but the heart rate was lower and arterial-alveolar carbon dioxide gradient was higher in the animals that received medetomidine. In those animals that received medetomidine, atipamezole was given to reverse the medetomidine but there was no difference in recovery times between the two regimens. Anaesthesia was not entirely reliable with medetomidine/ketamine and we recommend caution when using this mixture.

Genomic organization and physical map of the human inhibitors of apoptosis: HIAP1 and HIAP2

We report the genomic organization, mapping, and tissue distribution of the human inhibitors of apoptosis, HIAP1 and HIAP2. HIAP1 is 8.7 kb in length and is contained within eight coding and two non-coding (5'UTR) exons. The 4.5-kb HIAP2 message is contained within eight coding region exons and a single 5'UTR exon. The HIAP1 and HIAP2 genes lie in tandem on Chromosome (Chr) 11 (q22-23) with the intergenic distance being approximately 7 kb. The tissue distributions of HIAP1 and HIAP2 appear similar although the relative expression of HIAP1 is generally higher. Expression is highest in the kidney, small intestine, liver, and lung and lowest in tissues of the central nervous system.

Using prior information to allocate significance levels for multiple endpoints

We maximize power in a replicated clinical trial involving multiple endpoints by adjusting the individual significance levels for each hypothesis, using preliminary data to obtain the optimal adjustments. The levels are constrained to control the familywise error rate. Power is defined as the expected number of significances, where expectations are taken with respect to the posterior distributions of the non-centrality parameters under non-informative priors. Sample size requirements for the replicate study are given. Intuitive principles such as downweighting insignificant variables from a preliminary study and giving primary endpoints more emphasis are justifiable within the conceptual framework.

Foveal automatic target recognition using a multiresolution neural network

This paper presents a method for detecting and classifying a target from its foveal (graded resolution) imagery using a multiresolution neural network. Target identification decisions are based on minimizing an energy function. This energy function is evaluated by comparing a candidate blob with a library of target models at several levels of resolution simultaneously available in the current foveal image. For this purpose, a concurrent (top-down-and-bottom-up) matching procedure is implemented via a novel multilayer Hopfield neural network. The associated energy function supports not only interactions between cells at the same resolution level, but also between sets of nodes at distinct resolution levels. This permits features at different resolution levels to corroborate or refute one another contributing to an efficient evaluation of potential matches. Gaze control, refoveation to more salient regions of the available image space, is implemented as a search for high resolution features which will disambiguate the candidate blob. Tests using real two-dimensional (2-D) objects and their simulated foveal imagery are provided.

Cardiopulmonary effects of clonidine, diazepam and the peripheral alpha 2 adrenoceptor agonist ST-91 in conscious sheep

The cardiopulmonary effects of the intravenous administration of clonidine (15 micrograms/kg), ST-91 (30 micrograms/kg) and diazepam (0.4 mg/kg) were compared in five healthy sheep using a randomized cross-over design, to determine whether the hypoxaemic effects of alpha 2 adrenoceptor agonists are due to sedation, or to peripheral alpha 2 adrenoceptor stimulation. All three drugs significantly lowered arterial oxygen tension (PaO2) levels within 2 min of their administration; however, clonidine and ST-91 produced long lasting and severe hypoxaemia with mean PaO2 levels of approximately equal to 40 mm Hg and 50 mm Hg (5.3 kPa and 6.6 kPa), respectively. The fall in PaO2 was considerably less with diazepam (63 mm Hg or 8.4 kPa at 2 min) and by 15 min the values did not differ from placebo treated animals. None of the drugs increased arterial carbon dioxide tension (PaCO2) levels when compared to saline treatment and the acid base variables did not show any significant change. A significant increase was recorded in the packed cell volume of the ST-91 treated group throughout the study. Within 2 min of their administration, all drugs caused a significant increase in mean arterial pressure (MAP) as compared to the placebo treated group. The MAP remained significantly increased for 5 and 60 min after clonidine and ST-91 treatment, respectively. The study shows that ST-91 and clonidine produce a greater degree of hypoxaemia than occurs with diazepam sedation, and that the hypoxaemic effect of alpha 2 adrenoceptor agonists in sheep are mainly mediated by peripheral alpha 2 adrenoceptors.

The comparative hypoxaemic effect of four alpha 2 adrenoceptor agonists (xylazine, romifidine, detomidine and medetomidine) in sheep

In the present study, the hypoxaemic potential of four alpha 2 agonists possessing different selectivity for alpha 2 adrenoceptors and of a saline placebo was studied in five clinically healthy sheep using a randomized Latin square design and equipotent sedative doses. Baseline values for heart rate (HR), mean arterial pressure (MAP), arterial oxygen (PaO2)f and carbon dioxide (PaCO2) tensions, respiration rate and maximum change in pleural pressure (delta Ppl) were obtained, followed by the intravenous administration of either: xylazine (150 micrograms/kg); romifidine (50 micrograms/kg); detomidine (30 micrograms/kg); medetomidine (10 micrograms/kg) or placebo. Subsequent recordings were made up to 60 min after drug administration. No significant (P < or = 0.05) alterations in any variable occurred with placebo. All the alpha 2 agonists significantly (P < or = 0.05) decreased PaO2 levels without a significant (P < or = 0.05) change in PaCO2. The lowest PaO2 values were 29-42 mm Hg (3.9-5.5 kPa) with no significant difference between drugs. Respiratory rate and delta Ppl increased significantly within 2 min of drug administration; the duration of this effect varied with the alpha 2 agonist, lasting longest with romifidine. As compared to the saline treated group, a significant increase in MAP was observed up to 10 min after administration of romifidine and detomidine, however, a significant decrease was seen at 10 and 45 min after xylazine and medetomidine, respectively. The alpha 2 agonists studied induced a similar change in PaO2 at peak effect, despite their reported variable selectivity for alpha 2 vs. alpha 1 adrenoceptors.

Modification of cardiopulmonary and intestinal motility effects of xylazine with glycopyrrolate in horses

Xylazine (XYL) administration in horses is accompanied by significant cardiovascular depression characterized by a 25-35% decrease in cardiac output (CO) which is likely to compromise tissue oxygen delivery (DO2), and usually vagally mediated bradycardia is an important cause of this reduced cardiovascular performance. To examine the possible benefit of preventing the bradycardiac response, 6 healthy horses were treated with intravenous (IV) saline (SAL) or 2.5 micrograms/kg glycopyrrolate (GLY) in a blinded, randomized, crossover trial. Fifteen minutes later, 1 mg/kg XYL was administered IV and systolic, diastolic and mean blood pressures (SBP, DBP, and MBP, respectively), central venous pressure (CVP), mean pulmonary artery pressure, heart rate (HR), CO, and arterial and mixed venous blood gases were measured at the following times: baseline, 2, 5, and 10 min post-SAL or GLY; and 2, 5, 10, 15, 30, 45 and 60 min post-XYL. Determination of cardiac index (CI), stroke index (SI), left ventricular work, systemic vascular resistance (SVR), DO2, oxygen uptake, and oxygen extraction ratio were made at the same time. Gastrointestinal (GI) motility was evaluated by four-quadrant auscultation for 24 h post-XYL. Statistical analysis of continuous variables was carried out using ANOVA for repeated measures and Wilcoxon's rank-sum test for non-parametric data. In GLY treated horses, HR, SBP, MBP, DBP, CI, DO2 and mixed venous oxygen tension were significantly higher up to 30 min after XYL (P < or = 0.02) while CVP and SI were significantly lower 2 and 5 min post-XYL, respectively. In both groups, GI motility as assessed by auscultation was virtually abolished for an hour, with a non-significant tendency for the decrease in motility to last longer in the GLY/XYL group. None of the treated horses developed abdominal discomfort. No significant difference was observed in the other variables. The study shows that 2.5 micrograms/kg GLY premedication reduces the cardiovascular depression caused by 1 mg/kg XYL, without adversely affecting GI motility.

Frequency dependence of forced oscillatory respiratory mechanics in horses with heaves

The effect of measurement frequency on respiratory mechanics was investigated in six horses with reversible allergic airway disease. Total respiratory impedance was measured at 1.5, 2.0, 3.0, and 5.0 Hz by using the forced oscillation technique with the horses in remission, after acute antigenic challenge producing clinical heaves, and with heaves but after the administration of 2 mg fenoterol by inhalation. The slopes of the magnitude (magnitude of Zrs) and real part (R) of total respiratory impedance over the frequency range 1.5-3 Hz changed significantly after antigenic challenge and fenoterol. The ratio of R at 2 Hz to R at 3 Hz, however, discriminated better among the three conditions. Compliance and resonant frequency (calculated by using a three-element model) changed significantly after antigenic challenge and fenoterol, but inertance did not. We concluded that horses with heaves showed frequency dependence of R and (magnitude of Zrs) at frequencies up to 3 Hz and that parameters derived from a three-element model were useful indicators of small airway obstruction in the horse.

Object recognition using multilayer Hopfield neural network

An object recognition approach based on concurrent coarse-and-fine matching using a multilayer Hopfield neural network is presented. The proposed network consists of several cascaded single-layer Hopfield networks, each encoding object features at a distinct resolution, with bidirectional interconnections linking adjacent layers. The interconnection weights between nodes associating adjacent layers are structured to favor node pairs for which model translation and rotation, when viewed at the two corresponding resolutions, are consistent. This interlayer feedback feature of the algorithm reinforces the usual intralayer matching process in the conventional single-layer Hopfield network in order to compute the most consistent model-object match across several resolution levels. The performance of the algorithm is demonstrated for test images containing single objects, and multiple occluded objects. These results are compared with recognition results obtained using a single-layer Hopfield network.

EMLA cream as a topical anesthetic before office phlebotomy in children

We studied the effectiveness of EMLA cream (2.5% lidocaine, 2.5% prilocaine) in reducing distress, anxiety, and pain associated with phlebotomy in pediatric outpatients. This was a randomized, double-blind, placebo-controlled study using EMLA cream or placebo 1 hour before phlebotomy. Distress, anticipatory anxiety, pain, and adverse reactions were measured. Measurements of distress and ease of procedure, as well as changes in heart rate, showed significant improvement with EMLA cream as compared with placebo. Pain was decreased with use of EMLA cream. Anticipatory anxiety levels were equal within both groups. Ratings of cream efficacy by parent/observer scales were in favor of EMLA cream.

Cardiopulmonary and gastrointestinal motility effects of xylazine/ketamine-induced anesthesia in horses previously treated with glycopyrrolate

OBJECTIVE

To assess the usefulness of glycopyrrolate (GLY) in preventing the decrease in cardiac index (CI) usually caused by xylazine (XYL)/ketamine (KET)-induced anesthesia in horses.

ANIMALS

6 healthy horses.

PROCEDURE

Horses were treated with saline solution or 2.5 micrograms of GLY/kg of body weight, administered i.v. 15 minutes later, XYL (1 mg/kg) was administered i.v., followed 5 minutes later by KET (2 mg/kg) administration. The horses were positioned in left lateral recumbency, insufflated with 15 L of oxygen/min, and maintained for 30 minutes on the infusion of 0.05 mg of XYL and 0.1 mg of KET/kg/min. Mean, systolic, and diastolic arterial blood pressures, mean pulmonary arterial and central venous pressures, heart rate, CI, and arterial and mixed venous blood gas tensions were recorded up to 40 minutes after anesthesia induction. Intestinal motility was assessed by auscultation of 4 abdominal quadrants for 24 hours after induction. Data were analyzed by Wilcoxon's rank-sum test for nonparametric observations, and by ANOVA for repeated measures and Scheffé's test for continuous parametric variables.

RESULTS

Horses given GLY had significantly higher heart rate; mean, systolic, and diastolic arterial blood pressures; CI; oxygen delivery; and mixed venous oxygen tensions, with significantly less tissue oxygen extraction, compared with saline-treated horses. Both groups had complete loss of intestinal motility associated with general anesthesia.

CONCLUSIONS

GLY significantly reduced the cardiovascular dysfunction attributable to general anesthesia with XYL and KET. The return of intestinal motility was delayed by 3 to 6 hours without causing any serious side effects.

A comparison of romifidine and xylazine when used with diazepam/ketamine for short duration anesthesia in the horse

The purpose of this study was to compare and evaluate sedation with intravenous xylazine (1.1 mg/kg bodyweight [BW]) versus intravenous romifidine (100 micrograms/kg BW) followed by induction of anesthesia with intravenous diazepam (0.04 mg/kg BW) and ketamine (2.2 mg/kg BW). Twelve healthy horses were used in a blinded, randomized, cross-over design. Heart rate, presence of 2nd degree atrioventricular heart blocks (2 degrees AVB), respiratory rate, arterial blood pressures, blood gases, packed cell volume, total serum proteins, and duration of anesthesia and recumbency were recorded. Induction and recovery quality was evaluated using a 0 to 4 score. Response to stimulation with noise, pressure, and cutaneous electrical stimulation was assessed at 5 minute intervals during recumbency to evaluate the depth of anesthesia. Heart rate was lower and 2 degrees AVB more frequent in the romifidine group, while blood pressure was lower in the xylazine group. Duration of anesthesia was longer in the romifidine group (mean 20.8, s mean 2.3 min) versus the xylazine group (mean 15.8, s mean 1.6 min), while induction and recovery were excellent in both groups. Respiratory rates, blood gas values, packed cell volumes, and total protein levels did not differ between groups. The results indicate that romifidine premedication followed by diazepam and ketamine is a very satisfactory regime for short duration intravenous anesthesia in horses.

Optimized target localization in stereotactic radiosurgery using real-time digital portal images

This paper presents a method for optimized estimation of target localization in stereotactic radiosurgery using real-time digital portal images. The positions of the two radiation sources and the two projection planes in radiosurgery can be chosen arbitrarily. The reconstruction of the target is characterized as a non-linear multi-variable optimization problem, which minimizes the difference between the actual target and the reconstructed target. This optimization problem is solved by the Gaussian least square differential correction (GLSDC) method. Due to the digitized errors and input data errors, the algorithm defines an indirect reference factor (the shortest distance between two x-rays pointing onto the target) as an indication of the accuracy of the method. Our experimental results show that the reference factor is less than 1.0 mm for the correct data entry. The proposed algorithm provides a method that supports on-line target localization which can be done directly on the digital portal imaging device.

A comparison of ketorolac with flunixin, butorphanol, and oxymorphone in controlling postoperative pain in dogs

Ketorolac tromethamine, a nonsteroidal anti-inflammatory analgesic, was compared with flunixin and butorphanol for its analgesic efficacy and potential side effects after laparotomy or shoulder arthrotomy in dogs. Sixty-four dogs were randomly assigned to receive butorphanol 0.4 mg/kg body weight (BW) (n = 21), flunixin 1.0 mg/kg BW (n = 21), or ketorolac 0.5 mg/kg BW (n = 22), in a double blind fashion. The analgesic efficacy was rated from 1 to 4 (1 = inadequate, 4 = excellent) for each dog. The average scores after laparotomy were ketorolac, 3.4; flunixin, 2.7; and butorphanol, 1.6. After shoulder arthrotomy, the average scores were ketorolac, 3.5; flunixin, 3.0; and butorphanol, 1.4 (5/11 dogs). As butorphanol was unable to control pain after shoulder arthrotomy, oxymorphone, 0.05 mg/kg BW, replaced butorphanol in a subsequent group of dogs and had a score of 2.0 (6/11 dogs). Serum alanine aminotransferase and creatinine were significantly elevated above baseline at 24 hours postoperatively in dogs receiving flunixin. One dog in each group developed melena or hematochezia. One dog receiving ketorolac had histological evidence of gastric ulceration. We concluded that ketorolac is a good analgesic for postoperative pain in dogs.

The relationship between respiratory exchange ratio, plasma lactate and muscle lactate concentrations in exercising horses using a valved gas collection system

A valved gas collection system for horses was validated, then used to examine the relationship between the respiratory exchange ratio (RER), and plasma and muscle lactate in exercising horses. Four healthy Standardbred horses were trained to breathe through the apparatus while exercising on a treadmill. Comparisons of arterial blood gas tensions were made at 3 work levels for each horse, without (control), and with the gas collection system present. At the highest work level, the arterial oxygen tension (PaO2) was significantly lower (P < 0.05), and the arterial carbon dioxide tension (PaCO2) was significantly higher (P < 0.05), than control levels when the apparatus was present; however arterial oxygen content remained unchanged. The horses completed a standardized incremental treadmill test on 4 occasions to determine the repeatability of measurements of oxygen consumption (VO2), carbon dioxide production (VCO2), inspired minute ventilation (VI), respiratory exchange ratio (RER), ventilatory equivalent for oxygen (VI/VO2), tidal volume (VT), and ventilatory frequency (VF). All gas exchange and respiratory measurements showed good reproducibility with the mean coefficient of variation of the 4 horses ranging from 3.8 to 12%. We examined the relationship between 3 indices of energy metabolism in horses performing treadmill exercise: respiratory exchange ratio (RER), central venous plasma and muscle lactate concentrations. A relationship between RER and plasma lactate concentration was established. To compare muscle and plasma lactate concentrations, the horses completed a discontinuous exercise test without the gas collection apparatus present. Significant relationships (P < 0.05), between plasma lactate concentration and RER, and between plasma and muscle lactate concentration, were described for each horse. The valved gas collection system produced a measurable but tolerable degree of interference to respiration, and provided reproducible measurements of gas exchange and ventilatory measurements. It was concluded that measurements of both gas exchange and blood lactate may be used to indicate increased glycolytic activity within exercising skeletal muscle.

Oxygen cost of ventilation in the resting horse

The purpose of this study was to develop a technique to measure the oxygen cost of ventilation and the values of ventilatory parameters in seven normal horses rebreathing carbon dioxide (CO2). All the horses responded to increased inspiratory levels of CO2 by increasing their tidal volume (VT) and frequency of breathing (Vf). The mean (SE) oxygen cost litre-1 of ventilation, measured at rates of ventilation greater than 200 litres min-1 was 1.7 (0.04) ml litre-1, similar to that of normal human subjects ventilating submaximally. It was concluded that the CO2 rebreathing test is a practical, non-invasive means of measuring the oxygen cost of breathing and the ventilatory response to CO2 in horses.

Analysis of a 2(9) full factorial chemical library

Robotic synthesis is making possible the synthesis of large, systematically designed sets of compounds. We analyze a 512-compound set that is a 2(9) full factorial experimental design using a recursive partitioning algorithm, FIRM, and a high-dimension visualization tool, TempleMVV. These techniques are used to quickly and easily identify the main trends in the data set and also identify unusual observations. We show that analytical and visualization methods can be used synergistically to analyze a large, complex, high-dimensional data set. We also show that a fractional factorial design of 128 compounds would give essentially the same information.

Comparison of aerobic capacity between racing standardbred horses

A standardized treadmill test was used to compare metabolic and ventilatory measurements between 10 standardbred racehorses. The horses were divided into two groups: group A (n = 5) had mean racing speeds of 4.4 s faster than group B (n = 5) over a 1-mi. distance. Each horse was fitted with a venous catheter and connected to a valved gas-collection system. The exercise test consisted of 1-min incremental workloads ranging from 4.0 to 12.0 m/s at a treadmill incline of 3 degrees. Group A had significantly higher (P < 0.05) measurements of maximal O2 consumption (VO2max), O2 pulse, and tidal volume. Venous lactate concentration and respiratory exchange ratio measured at VO2max were also significantly higher (P < 0.05) in group A. Similar treadmill velocities were required to achieve a respiratory exchange ratio of > 1 and venous blood lactate concentration of > 4 mmol/l; however, group A was able to complete a significantly higher (P < 0.01) number of workloads before fatigue. The high aerobic and anaerobic capacity of group A horses may be a major contributor to a faster racing performance.

An urgent technique of applying high frequency jet ventilation in patients with extreme periglottic stenosis

Applying high frequency jet ventilation (HFJV) to patients with extreme periglottic stenosis (EPS) carries high risk of barotrauma or severe circulatory depression, since the stenotic airway will result in inadequate outflow tract obstructing the passage of the expired gas. We encountered with emergent obstruction of the outflow tract in 13 patients with EPS during HFJV in endolaryngeal microsurgery (ELM) procedures. The phenomenon of progressive gas trapping occurred within seconds in all patients. Barotrauma and disastrous circulatory depression would occur if we had not recognized them and then taken some measures immediately. We surmounted these potentially lethal events without interrupting the surgical procedures and found neither hypoxia nor barotrauma in all these patients. This may attribute to an urgent technique, i.e., intermittent disconnecting the jet conduit at the junction of the proximal end of the insufflation catheter and the distal end of the patient connecting tube of jet ventilator during HFJV.

Respiratory mechanics of horses measured by conventional and forced oscillation techniques

Respiratory mechanics were compared using conventional and forced oscillation techniques in six conscious horses and a mechanical model of the equine respiratory system. The parameters calculated from conventional airflow and esophageal pressure measurements were pulmonary resistance and dynamic compliance. The impedance of the respiratory system was measured at 1, 2, and 3 Hz with the forced oscillation technique, and respiratory system resistance, compliance, inertance, and resonant frequency were calculated. Pulmonary resistance was 1.0 +/- 0.3 cmH2O.l-1.s, and pulmonary dynamic compliance was 2.4 +/- 0.6 l/cmH2O. With the use of the forced oscillation system, respiratory resistance was 1.61 +/- 0.50 cmH2O.l-1.s at 1 Hz, compliance was 0.195 +/- 0.075 l/cmH2O, inertance was 0.026 +/- 0.0095 cmH2O.l-1.s2, and resonant frequency was 2.40 +/- 0.25 Hz. Data collected from a model of the respiratory system showed a close correlation between resistance and compliance measured with the two systems. This study demonstrates that the forced oscillation technique is a useful method for noninvasive measurement of respiratory mechanics in horses.

Analysis of the frequency spectrum of the equine electroencephalogram during halothane anaesthesia

The electroencephalogram (EEG) has been used in human clinical anaesthesia as an indicator of cortical activity and as an indicator of the depth of anaesthesia. It would be useful if it provided a reliable indication of the depth of anaesthesia of horses. In this study anaesthesia was induced with thiopentone and maintained with halothane in nine ponies. The end tidal halothane concentration (PE-Hal) was monitored and 20 seconds of EEG were recorded at 0.8 per cent, 1.0 per cent and 1.2 per cent halothane, equivalent to the minimum alveolar concentration (MAC), 1.25 MAC and 1.5 MAC. Each 20 second block of data was divided into one second segments and averaged to give one second of averaged EEG from which a frequency spectrum was obtained by using a fast Fourier transformation. The power of the waveform at low frequency (1 to 3 Hz) was compared with that at higher frequency (9 to 11 Hz). The median frequency and 95th percentile (spectral edge) were also calculated. The spectral edge frequency had the best correlation with PE-Hal.

Postoperative analgesia using phenylbutazone, flunixin or carprofen in horses

Horses undergoing surgery were randomly assigned to one of three groups to receive phenylbutazone at 4 mg/kg (n = 72), flunixin at 1 mg/kg (n = 68) or carprofen at 0.7 mg/kg (n = 63) by slow intravenous injection at the end of surgery, just before they were disconnected from halothane. Pain was assessed by either of two resident surgical clinicians (who did not know which non-steroidal anti-inflammatory drug had been given) when the horses first stood up, two and four hours later and the next morning. If repeated doses of analgesic drugs were given the time was recorded and taken as an end point for the study. The presence or absence of side effects was also recorded. In the three groups there was no significant difference between the types of surgery performed, the numbers of horses requiring further analgesia or the pain scores at any time. In the horses needing further analgesia there was a significant difference in the time after surgery at which the further analgesia was given between those in the flunixin group, 12.8 +/- 4.3 hours (mean +/- sd) and those in the phenylbutazone group, 8.4 +/- 4.6 hours; the carprofen group had an intermediate interval of 11.7 +/- 6.9 hours. Significantly fewer of the horses that received butorphanol during surgery needed further analgesia than of those that did not receive any opioid.

Factors influencing the outcome of equine anaesthesia: a review of 1,314 cases

Patient data, physiological variables and recovery quality were extracted from 1,314 records of equine anaesthetics covering a 7-year period and analysed retrospectively. Better recovery quality was significantly associated with shorter duration of anaesthesia, longer recovery times, less invasive surgery, a lower pulse rate at induction and higher pulse and respiratory rates during anaesthesia. Nineteen animals suffered serious anaesthetic-related problems (1.4% incidence) and 9 died (0.68% incidence). Clinical treatment of hypotension during anaesthesia significantly reduced the hypotensive index but did not significantly alter the recovery quality or incidence of post-anaesthetic myopathy. The severity of the myopathy was, however, markedly reduced in the animals treated for hypotension.

Effect of inhalation anaesthetics on total respiratory resistance in conscious ponies

Total respiratory resistance was measured rapidly and non-invasively in 6 conscious ponies before and after they inhaled approximately 25% of the minimal anaesthetic concentration (0.25 MAC) of either enflurane, halothane, or isoflurane, over a 10 min period. The forced random noise (FRN) method was used to measure the impedance over the frequency range of 5 to 40 Hz and its real part, the resistance, was extracted from these impedance measurements. At the concentrations used, halothane appeared to have no effect on the total respiratory resistance; enflurane and isoflurane seemed to increase it but the changes were not statistically significant.

Technique for continuous stride analysis of horses exercising on a treadmill

A technique for continuous computerised recording and analysis of the stride of horses on a treadmill is described. Advantages of the system are low cost, the use of normal shoes and the calculation of stride parameters in real time.

Cardiorespiratory responses to electrical stimulation of the buccal mucosa in ponies

The cardiovascular and respiratory responses to electrical stimulation of the buccal mucosa under general anaesthesia in ponies were measured in order to provide some insight into the cardiorespiratory effects of anaesthesia in equidae. This knowledge may be useful for reducing morbidity during clinical anaesthesia in horses. Anaesthesia was induced with intravenous thiopentone and maintained with 1.3 per cent inspired halothane in oxygen. Arterial blood pressure, heart rate, minute volume, tidal volume, respiratory rate, arterial blood gas tensions and clinical signs of anaesthetic depth were recorded while the buccal mucous membrane was stimulated electrically. A rise in arterial blood pressure was the most consistent response detected along with clinical signs. The response of individual animals varied considerably. Alterations of respiratory pattern sometimes occurred during stimulation but there was no consistent pattern of change in any animal.