Biomedical subjects

Sean M Johnston

Publications and source records attributed to Sean M Johnston.

4 recordsLinked to original sources

PubMed2006

Training in laparoscopic appendectomy.

BACKGROUND: The role of laparoscopic appendectomy (LA) in surgical training is unclear. Although LA as a therapeutic modality is potentially superior to open surgery, it has failed to become established as standard in training hospitals. The aim of the present study was to evaluate the outcome of LA performed by inexperienced surgeons in a training environment. MATERIALS AND METHODS: A retrospective analysis of all attempted LA performed over a 12-month period was undertaken. Data collected included operator grade (experienced and inexperienced), conversion rate and duration of surgery, complications, and postoperative stay. RESULTS: During the study period, 169 appendectomies were performed. The conversion rate to open surgery declined significantly from 28% in the first quarter to 9% in the last quarter, with no difference in the conversion rate between experienced and inexperienced surgeons. Operative time shortened significantly in the inexperienced group. Postoperative complications occurred in 8% of patients, independent of operative grade. CONCLUSIONS: Our findings demonstrate that LA may be safely introduced as a teaching procedure. Time-to-train should not preclude institutions from adopting the laparoscopic approach in the treatment of acute appendicitis.

Adult↗

PubMed2004

Quantitative analysis of squalamine, a self-ionization-suppressing aminosterol sulfate, in human plasma by LC-MS/MS.

The special physico-chemical property of squalamine enables the formation of intra- or inter-molecular non-volatile strong salt, which is difficult to ionize in a mass spectrometer's interface. A sensitive, accurate, precise, and specific method for the quantitative determination of this self ion-suppressing compound in human plasma has been developed and validated using high performance liquid chromatography (HPLC) coupled with positive electrospray tandem mass spectrometry (MS/MS). Solid phase extraction (SPE) technique was utilized to extract human plasma samples using the Waters Oasis HLB cartridges. Deuterated squalamine was used as the internal standard (IS). Positive multiple reaction monitoring (MRM) mode was used to achieve both sensitivity and selectivity. A quadratic linearity range over 5-1000 ng/ml, R > 0.999 was achieved. Performance of the method has been validated and met all the specifications set forth in the US Food and Drug Administration's May 2001 "Bioanalytical Method Validation Guidance for Industry". Different sample reconstitution solutions were found to have dramatic impact on sensitivity of mass spectrometer used to squalamine. This is the first quantitation method using a positive and true multiple reaction monitoring mode detection for squalamine.

Cholestanols↗

PubMed2004

Dynamic magnetic resonance imaging of the pelvic floor in patients with idiopathic combined fecal and urinary incontinence.

The etiologies of combined fecal and urinary incontinence may be interrelated but remain poorly understood. A potential variable in this process is global pelvic floor dysfunction. The aim of this study was to prospectively assess the use of phased-array, body coil dynamic MRI in identifying pelvic floor abnormalities in patients with combined incontinence symptoms. Symptomatic patients were compared to asymptomatic control subjects and were selected from those referred to the pelvic physiology laboratory with complaints of combined urinary and fecal incontinence. All patients underwent standard urodynamic studies and anorectal physiologic assessment. Colonoscopy and endoanal ultrasonography were also performed. A standardized protocol was used for dynamic MRI, and the parameters were measured using workstation software (callipers, compass, and densitometer). In the incontinent group there was a significant difference, when compared to control subjects, in the angle of the levator ani muscle arch of the levator plate complex (3.0+/-5 degrees vs. 14+/-10 degrees; P=0.004), the width of the levator hiatus (58.3+/-8 mm vs. 46.5+/-8 mm; P=0.001), the area and tissue density of the levator ani muscle (19.5+/-1 mm(2) vs. 26.9+/-1 mm(2); P=0.001, and 157.3+/-47 pixels vs. 126.1+/-23 pixels; P=0.025, respectively), and in the length of the external anal sphincter (20.0+/-5 mm vs. 26.6+/-13 mm; P=0.03). Body coil dynamic MRI is a noninvasive and well-tolerated imaging modality. Our data show that it can identify changes in pelvic muscle morphology in patients with disorders of incontinence, and this may help in planning better management strategies.

Adult↗

PubMed2003

Determination of degradation products of squalamine lactate using LC/MS.

Heat, acid and base stress methods were applied to study the stability of squalamine lactate. Liquid chromatography coupled with mass spectrometry was used to analyze the degraded samples and tentative structural identifications were assigned based on their molecular weight measurements, reactivity and MS/MS fragmentation. Solid squalamine lactate generated a new amide, namely lactyl squalamide, when heated to 80 degrees C. Chemical structure for this new compound has been established by NMR and MS data interpretation and confirmed by direct comparison between the degradant and the synthesized compound. Squalamine lactate in pH 4 acetate buffer solution produced more degradants under stressed conditions. These degradants are formed due to the loss of the sulfate functionality. Squalamine lactate is stable in refrigerated conditions as well as in basic solution.

Cholestanols↗