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Biomedical subjects

S A Webb

Publications and source records attributed to S A Webb.

At least 19 recordsLinked to original sources
PubMed2005

Patterns of speciation in endemic Mexican Goodeid fish: sexual conflict or early radiation?

Currently there is much interest in the potential for sexual selection or conflict to drive speciation. Theory proposes that speciation will be accelerated where sexual conflict is strong, particularly if females are ahead because mate choice will accentuate divergence by limiting gene flow. The Goodeinae are a monophyletic group of endemic Mexican fishes with an origin at least as old as the Miocene. Sexual selection is important in the Goodeinae and there is substantial interspecific variability in body morphology, which influences mate choice, allowing inference of the importance of female mate choice. We therefore used this group to test the relationship between sexual dimorphism and speciation rate. We quantified interspecific variation in sexual dimorphism amongst 25 species using a multivariate measure of total morphological differentiation between the sexes that accurately reflects sexual dimorphism driven by female mate choice and also used a mtDNA-based phylogeny to examine speciation rates. Comparative analyses failed to support a significant association between sexual dimorphism and speciation rate. In addition, variation in the time course of speciation throughout the whole clade was also examined using a similar tree containing 34 extant species. A constant rates model for the growth of this clade was rejected, but analyses instead indicated a decline in the rate of speciation over time. These results support the hypothesis of an early expansion of the group, perhaps due to an early radiation influenced by the key innovation of live bearing, or the prevalence of Miocene volcanism. In general, support for the role of sexual selection in generating patterns of speciation is proving equivocal and we argue that vicariance biogeography and adaptive radiations remain the most likely determinants of major patterns of diversification of continental organisms.

Animals↗
PubMed2003

Cementum engineering with three-dimensional polymer scaffolds.

Cloned cementoblasts (OCCMs), periodontal ligament fibroblasts (SV-PDLs), and dental follicle (SV-F) cells obtained from mice were used as a tool to study periodontal tissue engineering. OCCM, SV-PDL, and SV-F cells were seeded onto three-dimensional poly lactic-co-glycolic acid (PLGA) scaffolds and cultured with the use of bioreactors or implanted subcutaneously in severe combined immune deficiency (SCID) mice for up to 6 weeks. We explored the behavior of these cells in porous PLGA sponges by cell growth, expression of mineral-associated genes using reverse transcriptase polymerase chain reaction, and mineralization by histologic analysis in vitro and in vivo. Results indicated that cells attached to PLGA scaffolds under either static or dynamic conditions in vitro. Only OCCM implants, retrieved from both in vitro bioreactors and SCID mice at 3-and 6-weeks post-cell implantation exhibited mineral formation. Types I and XII collagens, osteocalcin, and bone sialoprotein genes were detected in all implants retrieved from SCID mice. These results suggest that delivery of selected cells via PLGA scaffolds may serve as a viable approach for promoting periodontal tissue regeneration.

Animals↗
PubMed2003

Gene therapy of bone morphogenetic protein for periodontal tissue engineering.

BACKGROUND: The reconstruction of lost periodontal support including bone, ligament, and cementum is a major goal of therapy. Bone morphogenetic proteins (BMPs) have shown much potential in the regeneration of the periodontium. Limitations of BMP administration to periodontal lesions include need for high-dose bolus delivery, BMP transient biological activity, and low bioavailability of factors at the wound site. Gene transfer offers promise as an alternative treatment strategy to deliver BMPs to periodontal tissues. METHODS: This study utilized ex vivo BMP-7 gene transfer to stimulate tissue engineering of alveolar bone wounds. Syngeneic dermal fibroblasts (SDFs) were transduced ex vivo with adenoviruses encoding either green fluorescent protein (Ad-GFP or control virus), BMP-7 (Ad-BMP-7), or an antagonist of BMP bioactivity, noggin (Ad-noggin). Transduced cells were seeded onto gelatin carriers and then transplanted to large mandibular alveolar bone defects in a rat wound repair model. RESULTS: Ad-noggin treatment tended to inhibit osteogenesis as compared to the control-treated and Ad-BMP-7-treated specimens. The osseous lesions treated by Ad-BMP-7 gene delivery demonstrated rapid chrondrogenesis, with subsequent osteogenesis, cementogenesis and predictable bridging of the periodontal bone defects. CONCLUSION: These results demonstrate the first successful evidence of periodontal tissue engineering using ex vivo gene transfer of BMPs and offers a new approach for repairing periodontal defects.

Adenoviridae↗
PubMed1999

Evaluation of the BOD POD for assessing body fat in collegiate football players.

PURPOSE: The purpose of this investigation was to evaluate the accuracy of a new air displacement plethysmograph, BOD POD Body Composition System, for determining %fat in collegiate football players. METHODS: Body fatness was estimated from body density (Db), which was measured on the same day using the BOD POD and hydrostatic weighing (HW) in 69 Division IA football players. In addition, 20 subjects were whole body scanned using dual-energy x-ray absorptiometry, DXA (Lunar DPX-L) to assess total body mineral content and %fat. Mineral content and HW determined Db were used to compute %fat from a three-component model (3C; fat, mineral, and residual). RESULTS: Test-retest reliability for assessing %fat using the BOD POD (N = 15) was 0.994 with a technical error of measurement of 0.448%. Mean (+/- SEM) Db measured with the BOD POD (1.064 +/- 0.002 g x cc(-1) was significantly greater (P < 0.05) than HW (1.060 +/- 0.002 g x cc(-1)), thus resulting in a lower %fat for the BOD POD (15.1 +/- 0.8%) compared with HW (17.0 +/- 0.8%). Similar results (N = 20) were found for DXA (12.9 +/- 1.2%) and the 3C (12.7 +/- 0.8%) where %fat scores were significantly higher (P < 0.05) than scores determined using the BOD POD (10.9 +/- 1.0%). CONCLUSIONS: Db measured with the BOD POD was higher than the criterion HW, thus yielding lower %fat scores for the BOD POD. In addition, BOD POD determined %fat was lower than DXA and 3C determined values in a subgroup of subjects. Assessment of %fat using the BOD POD is reliable and requires minimal technical expertise; however, in this study of collegiate football players, %fat values were underpredicted when compared to HW, DXA, and the 3C model.

Absorptiometry, Photon↗
PubMed1998

Contamination of propofol infusions in the intensive care unit: incidence and clinical significance.

Epidemics of bacteraemia and wound infection have been associated with the infusion of bacterially contaminated propofol administered during anaesthesia. We conducted an observational study to determine the incidence and clinical significance of administration of potentially contaminated propofol to patients in an ICU setting. One hundred patients received a total of 302 infusions of propofol. Eighteen episodes of possible contamination of propofol syringes were identified, but in all cases contamination was by a low-grade virulence pathogen. There were no episodes of clinical infection or colonization which could be attributed to the administration of contaminated propofol. During the routine use of propofol to provide sedation in ICU patients the risk of nosocomial infection secondary to contamination of propofol is extremely low.

APACHE↗
PubMed1997

Pediatric ECMO for severe quinidine cardiotoxicity.

We report the use of extracorporeal membrane oxygenation (ECMO) to establish and maintain cardiovascular stability in a 16 month old with refractory bradydysrrhythmias and hypotension after an acute overdose of quinidine. He underwent an 11-day course of ECMO and was discharged with normal neurologic function. This case illustrates the role ECMO can play in the treatment of profound cardiovascular collapse caused by toxic ingestions. To be optimally effective, management of such patients must be anticipatory.

Anti-Arrhythmia Agents↗
PubMed1996

The use of inhaled aerosolized prostacyclin (IAP) in the treatment of pulmonary hypertension secondary to pulmonary embolism.

OBJECTIVE: To describe the use of inhaled aerosolized prostacyclin (IAP) in a patient with life-threatening pulmonary hypertension secondary to pulmonary embolism and to discuss the possible use of inhaled prostacyclin in the management of pulmonary embolism. DESIGN: Case report. SETTING: Intensive care unit of a university teaching hospital. PATIENTS: One patient with severe pulmonary hypertension secondary to acute-on-chronic pulmonary embolism. INTERVENTIONS: Conventional medical management of massive pulmonary embolism and inhaled aerosolized prostacyclin (IAP). MEASUREMENTS AND RESULTS: Description of clinical course, haemodynamic data and gas exchange data. CONCLUSIONS: We describe a patient with massive pulmonary embolism for whom the addition of IAP to his therapy appeared to result in a transient improvement in pulmonary haemodynamics and gas exchange.

Administration, Inhalation↗
PubMed1996

Outbreak of gentamicin-resistant Acinetobacter baumanii in an intensive care unit: clinical, epidemiological and microbiological features.

The clinical, epidemiological and microbiological features of an outbreak of infection and colonisation caused by gentamicin-resistant Acinetobacter baumanii (GRAB) in an 18-bed intensive care unit (ICU) of a 680-bed adult teaching hospital are described. A retrospective review of medical, laboratory and infection control records was followed by prospective surveillance. Typing of isolates was performed by restriction enzyme analysis (REA) of chromosomal DNA. The incidence of GRAB in the ICU increased from 1.26 cases per 1000 occupied bed days (OBDs) for January to June 1993, to 6.62 per 1000 OBDs for July to December 1993 (Chi square = 4.8, P < 0.05), confirming the existence of an outbreak. For the two year period, 1993 and 1994, a total of 45 cases of GRAB infection or colonisation was identified. Males and females were equally represented, with an age range of 16-79 years and a mean age of 51 years. Admitting diagnoses varied, with multiple trauma and head injury predominating (ten cases). For 35 of the 45 cases the initial site of GRAB isolation was sputum or other respiratory tract specimen. Specific treatment for GRAB was initiated in 23 patients, however no deaths were directly attributable to GRAB infection. The period of time between admission to the ICU and first isolation of GRAB ranged from three to 70 days with a median of nine days. Overall, ten (11%) of 91 staff hand samples and one of 37 (3%) environmental samples yielded GRAB. All GRAB isolates produced similar biochemical profiles and antibiotic resistance patterns, except for a group of five which were ciprofloxacin resistant. Thirty patient isolates, all ten staff hand isolates and the environmental isolate produced identical REA patterns. The remaining five patient isolates (all ciprofloxacin resistant) which were available for typing produced a different REA pattern. Our study has documented a moderate-sized outbreak of GRAB in an ICU setting. Typing of isolates using REA was useful in delineating outbreak strains. Carriage of GRAB on staff hands was demonstrated as the most likely source of infection. Despite institution of infection control measures GRAB now appears endemic in the ICU.

Acinetobacter↗
PubMed1996

Prediction of childhood drowning and near-drowning morbidity and mortality.

OBJECTIVES: (a) Evaluate the presenting hemodynamic status and neurologic function of a series of warm water submersion injuries. (b) To ascertain the importance of the timing of the neurologic examination. (c) To identify risk factors that predict which patients will not return to presubmersion status. DESIGN: Retrospective review of all patients with a diagnosis of drowning/near-drowning responded to by the Children's Hospital pediatric transport service. Data were collected over a 24-month period regarding patient characteristics, submersion medium, rescue efforts, time out of sight, elapsed times to emergency department (ED) and pediatric intensive care unit (PICU) arrival, neurologic and hemodynamic status on arrival at the ED and PICU, reconstructed Conn-Modell category, and neurologic outcome. SETTING: EDs of the referring hospitals and PICU of the Children's Hospital of Orange County (CHOC), California. PATIENTS: Ninety-three submersion victims at an average age of 31 months. All patients were provided intensive care support. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Twenty-three percent (21/ 93) of patients died or survived vegetative. No patient arriving comatose and asystolic in the ED survived neurologically intact (n = 21, three patients expired in the ED). This group of patients had a mean duration of documented asystole = 41 minutes, range of 18 to 107 minutes, and time to ED arrival = 21 minutes. All patients with a detectable pulse and blood pressure (n = 72) on arrival to the ED, regardless of their neurologic status, recovered to their presubmersion status. Patients arriving comatose (decorticate, decerebrate, or flaccid posture) in the PICU (n = 18, mean arrival = 192 minutes) all died or were vegetative. All patients with non-coma (n = 72, Conn-Modell category A or B) on arrival to the PICU recovered normally. CONCLUSIONS: Hemodynamic status in the ED and neurologic status in the PICU are highly predictive of outcome. On arrival to the ED, the cardiovascular status is more predictive of abnormal outcome than neurologic status. Poor neurologic outcome appears inevitable for warm water submersion victims who are asystolic at ED arrival and remain comatose for more than 200 minutes.

Child, Preschool↗
PubMed1996

Percutaneous dilational tracheostomy--a clinical study evaluating two systems.

Percutaneous dilational tracheostomy (PDT), first described in the 1950s, has become a common bedside technique in the Intensive Care Unit (ICU). This study compares the early complications associated with the use of the Ciaglia PDT (Cook Critical Care, Bloomington, USA) technique, with the newly available Portex PDT technique (Portex Ltd., UK). The Ciaglia technique was adopted in this ICU in July 1994 and twenty-nine patients had a tracheostomy using this set until January 1995. Complications during the procedure were collected prospectively. When the Portex PDT set became available in January 1995, it was decided to assess the complication rate of this technique and compare them to the previously-collected data using the Ciaglia PDT set. Twenty-five patients have had a tracheostomy using the Portex PDT set. There has been no mortality associated with either PDT set. Bleeding requiring intervention occurred in two patients in the Ciaglia group and three patients in the Portex Group. All these patients had a bleeding diathesis. Loss of airway control occurred on one occasion in the Ciaglia group due to premature removal of the endotracheal tube. The first routine tracheostomy tube change at day 7 was complicated in four cases in the Ciaglia group. One infected stoma was noted in the Ciaglia group at day 7. Both techniques result in rapid, safe placement of a tracheostomy tube in critically ill patients in the ICU, obviating the need for surgical referral and transport to the operating room.

Adolescent↗
PubMed1996

Inhaled aerosolized prostacyclin as a selective pulmonary vasodilator for the treatment of severe hypoxaemia.

Two case reports are presented where inhaled aerosolized prostacyclin (IAP) was used to good effect as a selective pulmonary vasodilator. It was used in the treatment of a patient with severe hypoxaemia secondary to amniotic fluid embolism and for hypoxaemia secondary to the acute respiratory distress syndrome (ARDS) in a patient with acute on chronic liver failure and intra-abdominal sepsis. An apparent dose-response curve is demonstrated in the second case. A dose of IAP of 30-40 ng/kg/min produced an effect on oxygenation in the patient with liver failure equal to that seen at the maximal dose of (50 ng/kg/min). Reduction in dose below 30 ng/kg/min resulted in a deterioration in oxygenation towards baseline/pre-treatment levels. Inhaled aerosolized prostacyclin is a potent pulmonary vasodilator with little or no systemic hypotensive effect. It is simple to administer and would appear to be a viable alternative to inhaled nitric oxide.

Administration, Inhalation↗
PubMed1996

Central venous catheters revisited--infection rates and an assessment of the new Fibrin Analysing System brush.

Sixty-one consecutive patients in the Intensive Care Unit requiring central venous lines (CVC) for five or more days were randomized to receive either a standard triple lumen CVC (STD/CVC) or a silver sulphadiazine and chlorhexidine impregnated CVC (SSD/CVC). Data from the 54 patients who completed the trial show a reduced infection rate (positive tip culture) in the SSD/CVC group (4 out of 28) compared to the STD/CVC group (10 out of 26) (P < 0.05). In addition, the new Fibrin Analysing System (FAS) brush was evaluated and used to determine the presence of infection in all the CVCs (STD/CVC and SSD/CVC combined, n = 54) at day 3 (i.e. early warning of CVC colonization/infection) and at the time of removal of the CVC. The FAS brush was able to detect an infected CVC on only one occasion on day 3 out of the 14 CVC tips which were later found to be colonized/infected at the time of removal. The sensitivity of the FAS brush in detecting colonized/infected CVCs at the time of CVC removal compared with CVC tip culture was 21% with a specificity of 100%. These findings would currently not support the routine use of the FAS brush in determining CVC infection/colonization.

Acinetobacter↗
PubMed1996

Inhaled aerosolized prostacyclin and nitric oxide as selective pulmonary vasodilators in ARDS--a pilot study.

Nitric oxide 10 ppm and inhaled aerosolized prostacyclin 50 ng/kg/min were compared as selective pulmonary vasodilators in five patients with hypoxaemia secondary to acute respiratory distress syndrome. Neither agent resulted in systemic haemodynamic changes, indicating true pulmonary selectivity. Inhaled aerolized prostacyclin improved oxygenation to a degree comparable to nitric oxide, as measured by the arterial alveolar oxygen partial pressure gradient and shunt fraction.

Administration, Inhalation↗