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Biomedical subjects

G Smith

Publications and source records attributed to G Smith.

At least 199 records · Page 11Linked to original sources
PubMed1999

Dorsal lumbotomy incision for pediatric pyeloplasty--a good alternative.

This study reviews the value and benefits of the dorsal lumbotomy incision (DL) for exposure of the pelviureteric junction (PUJ) in infantile and paediatric pyeloplasty. Ninety-one children underwent pyeloplasty for confirmed PUJ obstruction between January 1993 and December 1997. The conventional loin incision (CL) (n = 60) was used as the standard, to which DL (n = 31) was compared. Information on the duration of surgery, length of hospital stay, length of time to return to full oral intake, and complications was obtained retrospectively from the hospital chart. The results were analysed using a non-parametrical statistical analysis. Follow-up was between 6 months and 5 years (median 2.4 years). The median age at surgery was 1.5 years (1 month-14 years). The median operating time was similar in both groups (95 min). The median length of stay was 3 days for the DL group compared to 7 days for the CL group (P < 0.001). The length of hospital stay had no correlation to the patient's age at surgery or the type of postoperative analgesia used. The median time to return to full oral intake and unrestricted activity in the DL group was 43 h compared to 83 h for the CL group (P < 0.001). The surgeons found that there was better exposure of the PUJ in infants in the DL group compared to the DL incision. There were no operative complications related to the DL itself. At the time of last follow-up 3 children required re-operation for a failed pyeloplasty, 2 in the DL group. The results suggest that DL is a safe and reasonable alternative to CL in paediatric pyeloplasty and probably the incision of choice in infantile pyeloplasty.

Adolescent↗
PubMed1999

Anthelmintic resistance revisited: under-dosing, chemoprophylactic strategies, and mating probabilities.

Deterministic and stochastic models are used to examine the evolution of anthelmintic resistance among trichostrongylid parasites of domestic ruminants. We find that the relative selection pressures exerted by chemoprophylactic (preventive) control strategies, chemotherapeutic (salvage) control strategies, and regimens involving "under-dosing" are critically dependent on a variety of host and parasite parameters (particularly host immunity and grazing behaviour, parasite fecundity, and the survival of the free-living stages on the pasture). Chemoprophylactic strategies are not necessarily more likely to exert a stronger selection pressure than chemotherapeutic strategies. Similarly, as one reduces dosage levels, there is a range of dose levels where under-dosing promotes resistance and a range of dose levels where under-dosing impedes resistance. The most dangerous dose is either that necessary to kill all the susceptible homozygotes, or that necessary to kill all the susceptible homozygotes and all the heterozygotes. Which one prevails depends upon model parameters. The stochastic formulation indicates that spatial heterogeneity in transmission may be a significant force in promoting the spread of resistant genotypes--at least when infection is at low levels.

Animals↗
PubMed1999

Herpesvirus genome mapping: a rapid generic approach.

A protocol for mapping the genome of the alphaherpesvirus macropodid herpesvirus 1 is described. This protocol greatly simplifies a similar protocol that was used to map the genome of the poxvirus molluscum contagiosum virus. A single restriction digestion is carried out on the viral DNA, and the fragments cloned into a plasmid vector. The ends of each cloned fragment are sequenced, translated, and used to search peptide sequence databases. Putative genomic maps are constructed by assembling contiguous fragments identified by the sharing of common open reading frames and through the demonstrated colinearity of herpesvirus genomes belonging to the same subfamily. Oligonucleotide primers designed from the nucleotide sequence at the ends of each cloned fragment enable confirmation of putative contiguous fragments by PCR. Fragments not identified by searches of peptide databases are subcloned using a rapid subcloning method. This approach involves restriction digestion of the cloned fragment with restriction enzymes present in both the multiple cloning site of the vector, and within the fragment. Digested fragments larger than the vector are recircularised and transformed into bacteria to generate subclones for sequence analysis. This subcloning method can also be used to order rapidly genes within large clones.

Alphaherpesvirinae↗
PubMed1999

Accuracy of burn size estimation and subsequent fluid resuscitation prior to arrival at the Yorkshire Regional Burns Unit. A three year retrospective study.

The accuracy of burn size estimation and subsequent fluid administration by referring hospitals prior to arrival at the Yorkshire Regional Burns Unit over a three-year period was assessed retrospectively. Burns around 20% body surface area were most accurately assessed, with smaller burns being overestimated and larger burns underestimated. Inaccuracies in fluid resuscitation result in, on average, patients receiving twice the appropriate volume of fluid for the burn size. The possible causes, implications and solutions to these problems are discussed.

Adolescent↗
PubMed1999

Research potential of a unique xenograft model of human proliferative breast disease.

A workshop on the 'Research potential of a unique xenograft model of human proliferative breast disease' was held at the Karmanos Cancer Institute, Wayne State University, Detroit, Michigan, in November of 1998. The accumulated information and current experimental findings on the MCF10AT model of preneoplastic, proliferative breast disease were reviewed. Discussions focused on the relevance of the model to clinical breast cancer and on the most profitable lines of further research to strengthen its utility.

Animals↗
PubMed1999

A fatal case of autoimmune thrombocytopenia with an IgM anti-GPIb/IX following one antigen mismatched unrelated donor bone marrow transplantation.

We report the case of a 32-year-old patient with ALL who developed autoimmune thrombocytopenia 2 months following allogeneic bone marrow transplantation. An IgM autoantibody against the platelet glycoprotein Ib/IX complex was observed. Treatment with high-dose steroids and intravenous immunoglobulin G failed to produce any benefit and the thrombocytopenia led to fatal gastrointestinal haemorrhage. The possible factors contributing to post-allograft thrombocytopenia and potential management strategies are discussed.

Adult↗
PubMed1999

Electrokinetic lithotripsy: safety, efficacy and limitations of a new form of ballistic lithotripsy.

OBJECTIVE: To investigate the safety and efficacy of electrokinetic lithotripsy (EKL), a ballistic lithotripter which uses high-energy magnetic fields to propel an impactor to fragment calculi. PATIENTS AND METHODS: The records and radiographs of 121 patients who underwent ureteroscopy using the EKL for stones in the upper (26), mid (28) or lower (67) ureter were reviewed retrospectively. Ureteroscopy was performed with an 8.5 F semi-rigid ureteroscope, through which a 3 F EKL probe was passed. RESULTS: A total of 148 stones (mean stone size 11.5 mm, range 6-40) in 121 patients were treated using the EKL. One patient was lost to follow-up. Of 148 stones, 147 (99.3%) were fragmented, including five that had resisted fragmentation with either pulsed-dye laser or electrohydraulic lithotripsy. Despite this, only 45 of 56 patients (80%) with a single stone in the lower ureter were rendered stone-free after a single ureteroscopic procedure. Seven patients in this group (12%) required shock-wave lithotripsy for fragments that had been propelled into the kidney, while four patients (7%) required repeat ureteroscopy for retained ureteric fragments. Complications were limited to minor ureteric perforations in two patients, both of which were treated with a stent. CONCLUSION: EKL is an inexpensive and reliable endoscopic method which fragments nearly all urinary calculi. Its limitations include the propulsion of fragments and the need to use an offset, semi-rigid ureteroscope. We recommend the use of a basket or graspers to remove fragments of >/=4 mm after EKL.

Adolescent↗
PubMed1999

Cardiovascular and catecholamine responses during endovascular and conventional abdominal aortic aneurysm repair.

OBJECTIVES: To compare changes in plasma catecholamines, acid-base status and cardiovascular dynamics in patients undergoing endovascular or conventional infrarenal abdominal aortic aneurysm (AAA) repair under standard general anaesthesia. DESIGN: Prospective cohort study. MATERIALS: 30 patients scheduled for elective infrarenal AAA repair. METHODS: Plasma epinephrine and norepinephrine concentrations, acid-base status and cardiovascular measurement were compared before surgery, and 5 min after aortic clamping and clamp release (conventional group) or occlusion and release (endovascular group) in patients undergoing endovascular (n = 15) or conventional AAA repair (n = 15). RESULTS: Arterial pH (p < 0.005) and base deficit (p < 0.05) increased, and plasma bicarbonate decreased (p < 0.005) during aortic cross-clamping in the conventional group. pH decreased further (p < 0.005), and base deficit and pCO2 increased (both p < 0.005) after clamp release. These changes were significantly greater than during endovascular repair, in whom within-group changes were not statistically significant. Values were similar in the two groups 30 min after reperfusion. Plasma epinephrine concentrations increased during conventional surgery (p < 0.05) and were greater than in the endovascular group (p < 0.05). Plasma norepinephrine concentrations increased during surgery in both groups but the changes were not statistically significant. CONCLUSIONS: Plasma catecholamine concentrations, changes in cardiovascular variables and acid-base status were increased during conventional compared with endovascular AAA repair.

Acid-Base Equilibrium↗
PubMed1999

Developing a video-mediated communication system for hospitalized children.

When a student is away from school for an extended time due to illness, he/she is provided with a tutor or access to in-hospital classrooms to keep up with his/her studies. This isolates the child from normal classroom experiences. A remote-control videoconferencing system (VCS), P.E.B.B.L.E.S.trade mark (Providing Education by Bringing Learning Environments to Students), was developed to allow a student access to his/her regular classroom from the hospital. Remote control is provided by a game pad, which allows the student to direct the system. The first iteration, P.E.B. B.L.E.S. I, tested feasibility. The design of P.E.B.B.L.E.S. II provides an integrated version of the system with user interface aimed at children. Four studies examined its efficacy in allowing a student to participate in typical classroom activities and in providing him/her a sense of presence in the classroom. Results indicate that the system can be used with relatively few errors when set to perform the majority of required activities. The study-participants reported positive experiences using the system, and remote users appeared to have a sense of presence in the classroom.

Attitude↗
PubMed1999

Optimizing results of lithotripsy using robust electromagnetic probe.

BACKGROUND AND OBJECTIVE: A significant impediment to the measurement of the pressures and forces created by lithotripter shockwaves has been their destructive properties, which have rendered most measuring devices impractical. We have developed and tested a robust electromagnetic probe to measure cavitational forces in vitro in the focal zones of extracorporeal lithotripters. The probe responds to the pressure gradient generated by the radial motion of cavitation bubbles. MATERIALS AND METHODS: The effects of shockwaves from the Dornier MPL 9000 electrohydraulic lithotripter were measured over the lifetime of multiple electrodes. RESULTS: The pulse energy from the electrodes dropped off rapidly after approximately 50% of the lifetime quoted by the manufacturer. The electrodes were more efficient at higher power settings. As a result, we altered our protocol for the treatment of ureteral stones to use a higher kilovoltage and a second electrode whenever necessary. Stone-free rates after shockwave lithotripsy (SWL) in situ for stones < 11 mm have increased from 68.2% to 83.3%, and the retreatment rate has dropped from 23% to 15%. Despite significantly higher power settings (23.7 kV v 18.7 kV; P < 0.0001), the need for sedoanalgesia has remained relatively constant (26% v 31%). CONCLUSIONS: Measurement of cavitational forces from lithotripters using a robust electromagnetic probe is useful in planning treatment strategy. We have demonstrated a clinically measurable improvement since implementing our new treatment protocol. Because the probe responds directly to cavitational forces, it should also prove useful for the objective comparison of different SWL machines.

Electromagnetic Phenomena↗
PubMed1999

Endourological management of severely encrusted ureteral stents.

BACKGROUND: Encrustion of ureteral stents is a well-known phenomenon which can be treated easily if recognized promptly. Severe encrustation, however, which leads to renal impairment, presents a challenge in management. PATIENTS AND METHODS: Four patients with encrusted stents were referred to our institution for management. All had impaired function of the affected kidney. Each was managed by either retrograde ureteroscopy or a combination of percutaneous and ureteroscopic procedures. RESULTS: All four of the patients were rendered stone free following an average of 2.5 (range 1-3) procedures. Renal function improved in all patients postoperatively. CONCLUSIONS: Encrustation is a potentially serious complication of the use of ureteral stents, as it can lead to renal impairment. Timely endourologic intervention can result in recovery of renal function.

Adult↗
PubMed1999

Nocturnal hypoxaemia and respiratory function after endovascular and conventional abdominal aortic aneurysm repair.

Respiratory function, assessed by pre- and postoperative spirometry, and overnight pulse oximetry recordings, was compared prospectively in patients undergoing infrarenal abdominal aortic aneurysm repair by endovascular or conventional surgery. Episodic hypoxaemia was common in both groups before operation and up to the fifth night after operation. The frequency and severity of hypoxaemia were greater in the conventional group (P < 0.05). FEV1 and FVC decreased significantly on the third and fifth days after operation in both groups (P < 0.05); decreases in FVC were greater in patients undergoing conventional surgery. On the fifth day after operation, FVC had recovered to 86% and 64% of preoperative values in the endovascular and conventional groups, respectively (P < 0.05). Duration of surgery was greater (P < 0.05) and duration of postoperative artificial ventilation significantly less (P < 0.05) after endovascular repair. Postoperative PCA morphine consumption and duration of use were significantly greater (P < 0.05) in patients undergoing conventional abdominal aortic aneurysm surgery.

Aged↗
PubMed1999

Upper airway reactivity and upper respiratory tract infection: effect of nebulized lidocaine.

Patients presenting for elective anaesthesia and surgery may be suffering with, or recovering from, a recent upper respiratory tract infection. Airway reflexes are heightened and these individuals may be more likely to suffer airway complications on administration of general anaesthesia. We have examined the effect of nebulized lidocaine on upper airway reflexes in such subjects. Using dilute ammonia as a chemical stimulus to the upper airway, we measured upper airway reactivity in 15 volunteers (aged 22-43 yr) with symptoms of an upper respiratory tract infection for 4 days or less. The threshold concentration of ammonia producing a brief reduction in inspiratory flow was determined. Measurements were made before and after administration of a nebulized solution of 4% lidocaine 4 ml or saline. After a 2-h interval the procedure was repeated with the alternative solution. The order of administration was randomized. The observer was blind to the solution given. Ammonia threshold was found to increase in subjects after nebulized lidocaine, from a median value of 327 (range 76-878) ppm to 878 (251-1620) ppm (P = 0.0007, Wilcoxon); there was no significant change after nebulized saline. After a convalescence period of at least 4 weeks, with no return of symptoms in the preceding 2 weeks, ammonia threshold was reassessed. It was found to be increased in all 15 subjects. Comparison of the five different times of measurement showed a highly significant difference (P < 0.001, Friedman). Subsequent analysis showed significant differences (P < 0.05, Wilcoxon) between convalescent ammonia threshold and both baseline and post-saline nebulizer values. There was no significant difference between convalescent and post-lidocaine ammonia threshold. We conclude that in adult subjects, nebulized lidocaine attenuated the heightened airway reflex sensitivity associated with symptoms and signs of upper respiratory tract infection.

Adult↗
PubMed1999

Repeatability and validity of an upper limb and neck discomfort questionnaire: the utility of the standardized Nordic questionnaire.

The repeatability and validity of a questionnaire for upper limb and neck complaints were assessed in a population of 105 hospital outpatients with a range of upper limb and neck disorders (including cervical spondylosis, adhesive capsulitis, lateral epicondylitis, carpal tunnel syndrome and Raynaud's phenomenon). Subjects were asked to complete a modified Nordic-style upper limb and neck discomfort questionnaire on two occasions closely spaced in time. The repeatability of their responses was assessed by calculating a kappa coefficient (kappa), and the sensitivity and specificity of component items in the questionnaire were determined for specific diagnostic categories of upper limb and neck disorder. Symptom reports for pain in the upper limb and neck, pain interfering with physical activities, neurological symptoms and blanching were all found to be highly repeatable (kappa = 0.63-0.90). A number of regional pain reports proved to be very sensitive in relation to specific upper limb disorders, but, with the exception of reported finger blanching in patients with Raynaud's phenomenon, none proved to have a good specificity (range = 0.33-0.38). We conclude that a modified Nordic-style questionnaire is repeatable and sensitive, and is likely to have a high utility in screening and surveillance. However a complementary examination schedule of adequate specificity and repeatability is essential to establish a clinical diagnosis.

Adult↗
PubMed1999

Crystal structure of the FMN-binding domain of human cytochrome P450 reductase at 1.93 A resolution.

The crystal structure of the FMN-binding domain of human NADPH-cytochrome P450 reductase (P450R-FMN), a key component in the cytochrome P450 monooxygenase system, has been determined to 1.93 A resolution and shown to be very similar both to the global fold in solution (Barsukov I et al., 1997, J Biomol NMR 10:63-75) and to the corresponding domain in the 2.6 A crystal structure of intact rat P450R (Wang M et al., 1997, Proc Nat Acad Sci USA 94:8411-8416). The crystal structure of P450R-FMN reported here confirms the overall similarity of its alpha-beta-alpha architecture to that of the bacterial flavodoxins, but reveals differences in the position, number, and length of the helices relative to the central beta-sheet. The marked similarity between P450R-FMN and flavodoxins in the interactions between the FMN and the protein, indicate a striking evolutionary conservation of the FMN binding site. The P450R-FMN molecule has an unusual surface charge distribution, leading to a very strong dipole, which may be involved in docking cytochrome P450 into place for electron transfer near the FMN. Several acidic residues near the FMN are identified by mutagenesis experiments to be important for electron transfer to P4502D6 and to cytochrome c, a clear indication of the part of the molecular surface that is likely to be involved in substrate binding. Somewhat different parts are found to be involved in binding cytochrome P450 and cytochrome c.

Animals↗