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Biomedical subjects

W D Smith

Publications and source records attributed to W D Smith.

At least 55 records · Page 3Linked to original sources
PubMed1998

IgE responses in the serum and gastric lymph of sheep infected with Teladorsagia circumcincta.

The IgE response of naive or previously infected sheep to 50,000 infective larvae of Teladorsagia circumcincta was monitored in serum and gastric lymph using a monoclonal antibody generated to recombinant ovine IgE in a dot blot assay. In 4/5 naive sheep, lymph and serum IgE concentrations increased from days 8 and 14 after infection, respectively. In most previously infected sheep, the IgE response to challenge was more rapid, although not necessarily greater than that following a primary infection. IgE concentrations in lymph were some 4-fold higher than in serum indicating that its source was the mucosa or draining nodes.

Animals↗
PubMed1998

IgE antibody during infection with the ovine abomasal nematode, Teladorsagia circumcincta: primary and secondary responses in serum and gastric lymph of sheep.

A monoclonal antibody to ovine IgE was employed in an ELISA to investigate the IgE antibody responses in serum and gastric lymph to a primary infection of Teladorsagia circumcincta, and following challenge in previously infected sheep. During a primary response, IgE antibody to antigens derived from the infective third stage (L3) and adult (L5) worms were negligible, with low levels of IgE antibody detected in serum and lymph. In contrast, there was a pronounced IgE antibody response in 2/4 sheep to L3 antigens during 2-8 days after challenge of previously infected animals but low levels of IgE antibody to L5 antigens. This response was confirmed in a second but similar experiment, where relatively high levels of IgE antibody was detected to antigens from L3. Antibody levels were higher in lymph than in serum from the same animals, and Western blots of L3 antigen following SDS-PAGE under reducing conditions revealed several bands of MW26-96KD which reacted with the IgE antibody from gastric lymph. Immunohistochemical staining indicated that these IgE antibodies may be reacting with allergens associated with the surface cuticle of the worms.

Animals↗
PubMed1998

The Virtual Instrumentation (VI) Laboratory facilitates customized on-site ergonomic analysis of minimally invasive surgery.

Ergonomic studies are needed to understand and improve the visual and physical interface that minimally invasive surgery methods interpose between the surgeon and the operating field. We used the Virtual Instrumentation (VI) Laboratory of the Biomedical Engineering Program at California State University, Sacramento to develop a portable ergonomic analysis system to compare the physical workloads imposed on the surgeon by tradition open and laparoscopic surgery techniques. We used the system at a national surgery conference to measure electromyogram (EMG) activity from thumb and forearm muscles of volunteer subjects as they performed simulated surgical tasks using open and laparoscopic techniques. We found that EMG activity was significantly greater for the laparoscopic than for the open surgery technique, suggesting that the laparoscopic technique was more physically demanding. The portable ergonomic analysis VI system was quick to set up and convenient to use. We are using the rapid prototyping and modular design capabilities of the VI Lab to develop additional ergonomic analysis VI systems.

Electromyography↗
PubMed1998

Virtual ergonomic studies in endoscopic intervention.

Virtual instrumentation provides a strong platform for the rapid design and prototyping of biomedical instruments. Virtual instrument software written using a block diagram approach familiar to instrument designers quickly turns a personal computer into a custom biomedical instrument. The portable VIs we have developed for ergonomic analysis of video-endoscopic surgery are quick to set up and convenient to use. We have collected a large amount of ergonomic data in a short time with these VIs because of their custom design and because we can take them to sites where there are many willing surgeon-subjects. We are preparing to use these VIs in studies of actual surgery.

Endoscopes↗
PubMed1997

Cloning and characterization of a microsomal aminopeptidase from the intestine of the nematode Haemonchus contortus.

In order to characterise the integral membrane glycoprotein H11 from the intestinal microvilli of the nematode Haemonchus contortus, cDNA libraries prepared using mRNA from adult worms from the UK and Australia were immunoscreened with anti-H11 sera. Antibodies affinity purified on the protein expressed by insert DNA (295 bp) of a positive clone from a UK library bound specifically to H11. A longer clone (948 bp) was obtained from the Australian library by hybridisation. Using a primer based on sequence common to these, a polymerase chain reaction product of 3.3 kb was generated from cDNA from UK H. contortus. The sequences from the UK and Australian nematodes were essentially identical over the 929 bp region in which both were represented. All three cloned DNAs hybridised to mRNA of about 3.5 kb. Analysis of the deduced amino acid sequence, which showed 32% identity with those of mammalian microsomal aminopeptidases, indicated that H11 has a short N-terminal cytoplasmic tail, a single transmembrane region and a long extracellular region with putative N-linked glycosylation sites and the HEXXHXW motif characteristic of microsomal aminopeptidases. Microsomal aminopeptidase activity co-purifies with H11. It is inhibited by bestatin, phenanthroline and amastatin. The recombinant protein has been expressed in active form in insect cells.

Amino Acid Sequence↗
PubMed1997

Molecular cloning and characterisation of a developmentally regulated putative metallopeptidase present in a host protective extract of Haemonchus contortus.

Antisera from lambs immunised with the Haemonchus contortus integral membrane protein complex, Haemonchus galactose-containing glycoprotein (H-gal-GP), the lambs being refractory to subsequent challenge, were used to identify several clones from an adult H. contortus lambda gt11 cDNA library. Using gene-specific oligonucleotide primers in conjunction with primers directed to a conserved nematode Spliced Leader (SL) sequence and to the polyA+ tail of mRNA, the remaining 5' and 3' sequences of one of these clones, metallopeptidase-1 (MEP1), were amplified. The 2.4 kb full-length coding sequences was subsequently amplified in a single reaction. Sequence analysis identified MEP1 as encoding a putative zinc metallopeptidase, which shared limited homology with the mammalian type II integral membrane protein neutral endopeptidase (NEP). Southern blotting indicated that MEP1 belonged to a multigene family. MEP1 was expressed in bacteria as a glutathione-S-transferase (GST) fusion protein, and a specific antiserum raised in sheep. This antiserum recognised several polypeptide components of H-gal-GP. Immunolocalisation studies showed that MEP1 encoded a protein located on the luminal surface of the nematode gut. Both MEP1 mRNA and protein are developmentally regulated with expression being limited to the blood-feeding stages of H. contortus.

Amino Acid Sequence↗
PubMed1997

Molecular cloning and characterisation of a putative aspartate proteinase associated with a gut membrane protein complex from adult Haemonchus contortus.

A cDNA was isolated from an adult Haemonchus contortus cDNA expression library the deduced amino acid sequence of which showed significant homology to mammalian pepsinogen sequences. The library was screened with antisera raised against Haemonchus galactose-containing glycoprotein complex, a gut membrane protein complex with aspartyl proteinase activity which has shown considerable potential as a protective antigen. The amino acid sequence obtained corresponded very closely in part to the N-terminal amino acid sequences of two polypetides within the complex. The enzyme was shown to be almost exclusively expressed by the blood-feeding parasite stages. The cDNA was expressed in E. coli, and antibody produced to the recombinant protein bound to the luminal surface of the gut in the adult parasite. The proteinase may play a central role in digesting the blood meal and is considered a potential sub-unit vaccine candidate.

Amino Acid Sequence↗
PubMed1997

Use of the virtual instrumentation laboratory for the assessment of human factors in surgery and anesthesia.

There is a growing consensus that human factors issues for anesthesiologists, surgeons, and other operating room personnel require serious attention. We have established a program of collaboration between the University of California Davis Medical Center Departments of Anesthesiology and Surgery and the California State University Sacramento Biomedical Engineering Program to address ergonomic problems in anesthesiology and surgery using a Virtual Instrumentation Laboratory. A 17-workstation Virtual Instrument Laboratory using LabVIEW software on Power Macintosh platforms permits rapid prototyping of medical monitor displays as well as rapid development of data acquisition and processing circuits for physiologic data collection. The Virtual Instrument Lab has been used for three Master's thesis projects and a BME course titled Human Factors in the Design of Medical and Assistive Technology. Course projects have included: 1) The design of novel physiologic data displays for potential use in anesthesia workstations, and 2) The measurement of surface electromyographic signals and heart rate variability to investigate the physical and mental workload of performing laparoscopic surgery. The Virtual Instrument Lab allows BME students to investigate relatively complex human factors issues in anesthesiology and surgery in a short time span.

Anesthesiology↗
PubMed1996

A measure of association for assessing prediction accuracy that is a generalization of non-parametric ROC area.

There is a need for a measure of prediction accuracy that generalizes non-parametric receiver operating characteristic (ROC) area to polytomous ordinal patient state. We describe such a measure, prediction probability PK derived from Kim's measure of association. We show that the value of PK equals the value of non-parametric ROC area for dichotomous patient state and is a meaningful generalization of non-parametric ROC area for polytomous state.

Anesthesia↗
PubMed1996

EEG Predicts movement response to surgical stimuli during general anesthesia with combinations of isoflurane, 70% N2O, and fentanyl.

OBJECTIVE: Our objective was to evaluate the performance of the EEG as an indicator of anesthetic depth by measuring EEG prediction of movement response to surgical stimuli. METHODS: While using 5 different combinations of isoflurane, 70% N2O, and fentanyl, we measured the EEG of 246 patients during pelvic laparoscopy and observed their movement responses to opening stimuli (defined as skin incision, CO2 needle insertion, or trocar insertion) and also to closing stimuli (defined as sutures during incision closure). The EEG was expressed as F95, the frequency in hertz below which resides 95% of the power in the EEG frequency spectrum. The relations between F95 and movement response were expressed as logistic regression curves. F95-response logistic regression curves, which are analogous to dose-response curves, were calculated for each of the 2 stimuli administered during each of the 5 anesthetic techniques. The prediction of patient responsiveness by F95 was tested using beta (beta), a measure of the slope of an F95-response logistic curve. The presence of shifts among the F95-response logistic curves was tested using the differences in F95 values between curves. Hypothesis tests used a level of significance of P = 0.05. MAIN RESULTS: The slopes of the F95-response logistic regression curves showed a statistically significant ability to predict movement response to stimuli for 9 of the 10 combinations of stimuli and anesthetic techniques. We did not calculate an F95-response logistic curve for the tenth combination because it contained burst suppression, which our EEG analysis method was not designed to process. The F95-response logistic curves were shifted relative to each other, and the shifts were affected by the type of stimulus and the combination of anesthetic agents. Referenced to opening curves, the mean shift of the closing curves was +4.2 +/- 0.3 Hz (mean +/- SD). With increasing doses of fentanyl, the use of 70% N2O, or both, the curves shifted to higher values of F95; the range in shifts was 0.2 to 8.1 Hz. The slope beta values of the F95-response logistic curves and the shifts among the curves were similar to the beta values and shifts that might be expected from changes in anesthetic agent doses. CONCLUSIONS: The EEG, expressed as F95, predicted movement response to surgical stimuli during combinations of isoflurane, 70% N2O, and fentanyl. The F95-response curves shifted upward on the frequency scale for the less intense stimuli and for anesthetic techniques using 70% N2O, fentanyl, or both. F95 prediction of movement response appeared to be related to anesthetic agent doses. Our F95-response curves may provide helpful guidelines for using F95 to titrate the administration of anesthetic agents and for assessing the depth of general anesthesia.

Adult↗
PubMed1996

Immunisation of sheep with an integral membrane glycoprotein complex of Haemonchus contortus and with its major polypeptide components.

Sheep were immunised against Haemonchus contortus with an integral membrane glycoprotein complex isolated from the intestines of the parasite as antigen. This antigen has been termed Haemonchus galactose-containing glycoprotein complex. Sodium dodecyl sulphate (SDS) polyacrylamide gel analysis has shown that it is composed of several polypeptides but so far these have proved refractory to separation when in the native state. However when dissociated by SDS, it was found to be as efficacious as in its native state, although it was less consistently protective when tested after being dissociated and reduced. An attempt was therefore made to identify the protective ingredient(s) of the dissociated complex by testing its major polypeptides individually after they had been separated on SDS polyacrylamide gels under non-reducing conditions. Partial protection was induced by protein bands with molecular weights of about 200 kD and less than 50 kD, but none of the individual fractions tested was as efficacious as the unseparated complex, suggesting that either more than one component was essential for a consistent effect or that the separation technique had damaged crucial protective epitopes.

Animals↗
PubMed1996

Measuring the performance of anesthetic depth indicators.

BACKGROUND: An appropriate measure of performance is needed to identify anesthetic depth indicators that are promising for use in clinical monitoring. To avoid misleading results, the measure must take into account both desired indicator performance and the nature of available performance data. Ideally, anesthetic depth indicator value should correlate perfectly with anesthetic depth along a lighter-deeper anesthesia continuum. Experimentally, however, a candidate anesthetic depth indicator is judged against a "gold standard" indicator that provides only quantal observations of anesthetic depth. The standard anesthetic depth indicator is the patient's response to a specified stimulus. The resulting observed anesthetic depth scale may consist only of patient "response" versus "no response," or it may have multiple levels. The measurement scales for both the candidate anesthetic depth indicator and observed anesthetic depth are no more than ordinal; that is, only the relative rankings of values on these scales are meaningful. METHODS: Criteria were established for a measure of anesthetic depth indicator performance and the performance measure that best met these criteria was found. RESULTS: The performance measure recommended by the authors is prediction probability PK, a rescaled variant of Kim's dy.x measure of association. This performance measure shows the correlation between anesthetic depth indicator value and observed anesthetic depth, taking into account both desired performance and the limitations of the data. Prediction probability has a value of 1 when the indicator predicts observed anesthetic depth perfectly, and a value of 0.5 when the indicator predicts no better than a 50:50 chance. Prediction probability avoids the shortcomings of other measures. For example, as a nonparametric measure, PK is independent of scale units and does not require knowledge of underlying distributions or efforts to linearize or to otherwise transform scales. Furthermore, PK can be computed for any degree of coarseness or fineness of the scales for anesthetic depth indicator value and observed anesthetic depth; thus, PK fully uses the available data without imposing additional arbitrary constraints, such as the dichotomization of either scale. And finally, PK can be used to perform both grouped- and paired-data statistical comparisons of anesthetic depth indicator performance. Data for comparing depth indicators, however, must be gathered via the same response-to-stimulus test procedure and over the same distribution of anesthetic depths. CONCLUSIONS: Prediction probability PK is an appropriate measure for evaluating and comparing the performance of anesthetic depth indicators.

Anesthesia↗
PubMed1996

Prediction of movement during propofol/nitrous oxide anesthesia. Performance of concentration, electroencephalographic, pupillary, and hemodynamic indicators.

BACKGROUND: Movement in response to painful stimulation is the end point classically used to assess the potency of anesthetic agents. In this study, the ability of modeled propofol effect-site concentration to predict movement in volunteers during propofol/nitrous oxide anesthesia was tested, then it was compared with the predictive abilities of the Bispectral Index and 95% spectral edge frequency of the electroencephalogram, pupillary reflex amplitude, and systolic arterial blood pressure. In addition, the relationships between simple end points of loss and recovery of consciousness, and pupillary, hemodynamic, and propofol concentration indicators were studied. METHODS: Ten healthy volunteers were anesthetized with an infusion of propofol, which was increased in three equal steps to 21 mg.kg lean body mass-1.h-1. After loss of the ability to hold a syringe and of the eyelash reflex, 60% nitrous oxide was introduced and the trachea was intubated without the use of muscle relaxants. The propofol infusion rate then was decreased to 15.4 mg.kg lean body mass-1.h-1. Ten minutes later, tetanic electrical stimulation was administered to the thigh via needle electrodes: if movement was observed within 1 min, the propofol infusion rate was increased by 1.75 mg.kg lean body mass-1.h-1 5 min after the stimulus; if not, it was similarly decreased. This 15-min sequence was repeated until volunteers "crossed over" from movement to no movement (or vice versa) four times. The propofol infusion rate then was increased to 21 mg.kg lean body mass-1.h-1, nitrous oxide was discontinued, the trachea was extubated, and the infusion rate was decreased in five equal steps over 50 min. The times at which the eyelash reflex returned and the birth date was recalled were recorded. The electroencephalogram was monitored continuously (FP1, FP2, ref: nasion, ground: mastoid). Measurements of the pupillary response, arterial blood pressure, and heart rate were recorded during induction and awakening, just before and for 5 min after each stimulation. Arterial blood samples were obtained for propofol assay, and propofol effect-site concentrations were calculated at each time. The predictive value of indicators was compared using a new static, the prediction probability (PK). RESULTS: Loss and return of the eyelash reflex occurred at greater propofol effect-site concentrations than either dropping the syringe or recall of the birthday. The propofol effect-site concentration (in the presence of 60% nitrous oxide) predicted to prevent movement after a supramaximal stimulus in 50% of volunteers was 1.80 micrograms/ml (95% confidence limits: 1.40-2.34 micrograms/ml). The Bispectral Index (PK = 0.86), 95% spectral edge frequency (PK = 0.81), pupillary reflex amplitude (PK = 0.74), and systolic arterial blood pressure (PK = 0.78) did not differ significantly from modeled propofol effect-site concentration (PK = 0.76) in their ability to predict movement. CONCLUSIONS: Indicators of pharmacodynamic effect, such as the electroencephalogram, pupillary light reflex, and systolic arterial blood pressure, predict movement as well as effect-site concentration during propofol/nitrous oxide anesthesia. Loss and return of the eyelash reflex correspond to a deeper level of anesthesia than syringe-dropping or recall of the birth date.

Adult↗
PubMed1996

Cardiorespiratory kinetics during exercise of different muscle groups and mass in old and young.

The purpose was to compare cardiorespiratory kinetics during exercise of different muscle groups (double-leg cycling vs treadmill walking and single-leg ankle plantar flexion) in old and young subjects. Oxygen uptake (VO2) during exercise transitions was measured breath by breath, and the phase 2 portion of the response was fit by a monoexponential for determination of the time constant (tau) of VO2. Two separate studies were performed: in study 1, 12 old (age 66.7 yr) and 16 young (aged 26.3 yr) subjects were compared during cycling and ankle plantar flexion exercise, and in the study 2, five old (aged 69.6 yr) and five young (24.4 yr) subjects were compared during cycling and treadmill walking. VO2 transients during square-wave cycling exercise were significantly slower in the old compared with the young groups. In contrast, VO2 kinetics did not differ between old and young groups during plantar flexion exercise. Heart rate (HR) kinetics followed the same pattern, with tau HR being significantly slower in the old vs young groups during transitions to cycling but not to plantar flexion. In study 2 tau VO2 and tau HR during on-transients to treadmill square-wave exercise were significantly slower in the old group compared with the young group, but tau VO2 was significantly faster during treadmill exercise than during cycling in the old group. The differences with aging between the modes of exercise may be related to the muscle mass involved and the circulatory demands. On the other hand, slowed VO2 kinetics with age appear to occur in a mode (cycling) in which the muscles are not accustomed to the activity, whereas in a mode of normal activity (walking) and with the muscle groups (plantar flexors) accustomed to the activity, VO2 kinetics are not slowed to the same degree with age.

Adult↗
PubMed1995

Wakeful response to command indicates memory potential during emergence from general anesthesia.

OBJECTIVE: An important aspect of assessing anesthetic depth is determining whether a patient will remember events during surgery. We looked for a clinical sign that would indicate a patient's potential for memory formation during emergence from anesthesia. A clinical sign indicating memory potential could be a useful endpoint for measuring the performance of anesthetic depth monitors and for titrating administration of anesthetic agents. METHODS: We evaluated patients' responses to commands to open the eyes, squeeze the hand four times, and count 20 numbers. These responses were correlated with results on recall, cued recall, and multiple-choice memory tests. MAIN RESULTS: Patients did not have evidence of memory formation until they sustained wakefulness sufficiently long to complete at least four hand squeezes or count four numbers. Of 28 patients, 13 (46%) with this sustained wakeful response had memory. Of 22 patients, 0 (0%) had evidence of memory formation when they demonstrated a brief wakeful response, defined as being responsive to command but unable to complete more than one hand squeeze or count, or an intermediate response, defined as two or three hand squeezes or counts. CONCLUSIONS: We conclude that a brief wakeful response to command indicates that a patient is unlikely to form memories, while a sustained wakeful response indicates that a patient may form memories. Thus, a patient's wakeful response to command could be a useful indicator of potential for memory.

Adult↗
PubMed1995

Brief wakeful response to command indicates wakefulness with suppression of memory formation during surgical anesthesia.

OBJECTIVE: In a previous study of patients emerging from anesthesia following surgery, we found that a brief wakeful response to command of an eye opening or single hand squeeze or count was not associated with memory formation, while the response of four hand squeezes or counts was associated with memory. We wanted to determine the anesthetic requirements for obtaining this brief wakeful response endpoint during surgery and to determine if memory occurred at this endpoint during surgical anesthesia. METHODS: Six different combinations of isoflurane, 70% N2O, and fentanyl were administered to 326 patients undergoing pelvic laparoscopy. After insertion of the trocar, anesthesia was reduced while patients were given verbal commands, and they were observed for movement responses to surgery and to command. Patients were classified as either not arousing, arousing with a movement response to surgery, or arousing with a wakeful response to command. For the patients who aroused, we calculated the percentage of arousal responses that were wakeful responses to command. The effect of fentanyl dosage upon the percentage of arousal responses that were wakeful responses to command was determined by using a Mann-Whitney test to compare a group of patients receiving fentanyl 2 micrograms/kg or less, with a group receiving fentanyl 4 micrograms/kg. In a subset of 39 patients, the potential for memory formation was evaluated by presenting a target sound to 29 patients during a period of either no arousal, movement response to surgery, or wakeful response to command; for a control group of 10 patients, no target sound was presented. All 39 patients were tested for memory of the target sound; the results from each group receiving a target sound were compared with the results of the control group, using a Mann-Whitney test. MAIN RESULTS: A total of 68 patients aroused with either a movement response or a wakeful response to command. Wakeful responses occurred with only 1 of 39 patients (3%) receiving fentanyl 2 micrograms/kg or less; but, wakeful responses occurred with 17 of 29 patients (59%) receiving fentanyl 4 micrograms/kg. The difference between the groups was significant at p = 0.01. None of the 68 patients had recall of intraoperative events or unpleasant dreams. None of these patients who were in the multiple-choice memory subset recalled the target sound. There were no statistically significant differences on the multiple-choice memory test between the groups presented with the target sound and the control group. Patient anecdotes suggested that some patients may have had memory of the target sound; but, memory was no more likely in patients with a brief wakeful response to command than in those who responded with a movement to surgical stimulation or those who did not have an arousal response. CONCLUSIONS: A brief wakeful response to a command of opening the eyes or squeezing the hand was not associated with increased memory formation during surgery. A brief wakeful response to command was found during surgery when patients received fentanyl 4 micrograms/kg; but it was rarely found at fentanyl dosages of 2 micrograms/kg or less.

Adolescent↗
PubMed1995

Effect of dietary protein supplementation on the development of immunity to Ostertagia circumcincta in growing lambs.

Thirty four-and-a-half-month-old worm-free lambs were used to determine whether the rate of development of immunity to Ostertagia circumcincta infection in growing lambs could be influenced by the addition of a by-pass protein supplement. Sixteen lambs (groups 1 and 2) were fitted with an abomasal catheter and infected daily with 2000 O circumcincta L3 for eight weeks. Group 1 lambs received 45 g of crude protein day-1 (sodium caseinate) as a continuous infusion into the abomasum from week-1 to week 8. At week 9, groups 1 and 2, together with eight naive controls (group 3), were treated with anthelmintic and challenged one week later with 50,000 O circumcincta L3 and killed after a further 10 days. An additional six worm-free lambs provided feed intake and growth rate data. All the lambs were offered a complete ruminant ration (167 g crude protein kg-1) ad libitum. The cumulative liveweight gain of both the trickle-infected groups was less than that of the controls. The mean faecal egg counts were lower in group 1 from day 39 after infection and the mean worm burdens were significantly lower than in group 2. Total Ostertagia populations did not differ significantly between group 3 and either group 1 or 2 lambs. Early L4 stages constituted a greater percentage of the total worm population in group 1 (79.5) and group 2 (48.5) than in the challenge controls (group 3) (20.4). The trickle-infected lambs also had higher concentrations of gastric mast cell protease which correlated positively with the proportion of early L4 stages and negatively with the total worm burden. The provision of by-pass protein supplement accelerated the development of immunity to O circumcincta in these lambs.

Animals↗