Determination of succinylcholine in plasma by high-pressure liquid chromatography with electrochemical detection

The plasma concentration of the neuromuscular blocking drug,succinylcholine, is difficult to measure. We have measured concentrationsof the breakdown product of succinylcholine, choline, to assesswhether choline concentration gives an accurate measure of succinylcholineconcentration. Choline concentration was measured by HPLC andelectrochemical detection in two blood or plasma samples, onein which succinylcholine hydrolysis was inhibited by 10^–5M physostigmine and another in which succinylcholine was completelyhydrolysed in 20 min by 200 mU butyrylcholinesterase at 37°C.The difference in choline content between the two samples givesthe succinylcholine concentration. Ninety-five per cent recoveryof choline was achieved. Choline standard curves were linearfrom 156 pmol ml^–1 to 200 nmol ml^–1. Within-dayand between-day mean coefficients of variation for succinylcholinehydrolysis were small (mean (SD) 3.7% (1.2%) and 3.8% (1.6%),respectively). We conclude that this method of measuring succinylcholineconcentration in blood is accurate, repeatable and relativelyeasy. Br J Anaesth 2000; 85: 592–8 ^* Corresponding author     

Determinants of bone density and prevalence of osteopenia among female runners in their second to seventh decades of age

This is a cross-sectional study of spine and hip bone density (BMD) in 124 female athletes, aged 16–68 years, who trained for at least 3 hs/week. The aim was to document the effects of competitive running on BMD in women over a broad age range. Thirty-three subjects, aged <35 years, were currently oligo- or amenorrheic and, of the 50 who were >40 years, and who were now menstruating normally, 13 had previously been oligo- or amenorrheic. Fifty-two women <50 years of age had never had disturbed menses. Twenty-four older women were postmenopausal. Women who had never had menstrual disturbance had significantly increased bone density at the lumbar spine, femoral neck, and femoral trochanter, as compared with young normal European reference data (range from +0.4 population SD or T-score units to +1.2 units according to measurement site and age group). In contrast, young amenorrheic or oligomenorrheic runners had reduced bone density, particularly at the spine (mean T score < −1.1), whereas older runners who previously had disturbed menses, but were now menstruating normally, had bone densities that were similar to sedentary young controls. Postmenopausal runners had bone density values that differed little from sedentary postmenopausal controls matched for time since menopause, after adjusting for the runners’ lower body weight. Bone density outcomes were related to candidate explanatory variables. After taking into account the other variables, age, per se, influenced only the femoral neck and Ward’s area. Years since last exposure to estrogen (at premenopausal levels) was an important determinant of bone loss at both hip and spine. Body weight had a beneficial influence on the femoral neck region, whereas (in contrast) height had a positive influence on the lumbar spine. Months of breastfeeding (totaled for all children) had a modest, positive influence, which was larger in the femoral measurement sites. There was no evidence of an effect of calcium intake or percent body fat on BMD at any site independent of these other effects. It is concluded that, with the consistent presence of normal premenopausal estrogen levels, running at least 3 hs/week substantially improves bone density, particularly at the proximal femur. This beneficial effect is reversed in the absence of the consistent past and current presence of normal menstrual function. There was no clear benefit of running seen on BMD in postmenopausal women, but premenopausal veteran athletes who started running after the age of 30 years were not disadvantaged compared with early starters.     

Antibody response to IR6, a conserved immunodominant region of the VlsE lipoprotein, wanes rapidly after antibiotic treatment of Borrelia burgdorferi infection in experimental animals and in humans

Invariable region (IR)(6), an immunodominant conserved region of VlsE, the antigenic variation protein of Borrelia burgdorferi, is currently used for the serologic diagnosis of Lyme disease in humans and canines. A longitudinal assessment of anti-IR(6) antibody levels in B. burgdorferi-infected rhesus monkeys revealed that this level diminished sharply after antibiotic treatment (within 25 weeks). In contrast, antibody levels to P39 and to whole-cell antigen extracts of B. burgdorferi either remained unchanged or diminished less. A longitudinal analysis in dogs yielded similar results. In humans, the anti-IR(6) antibody titer diminished by a factor of > or =4 in successfully treated patients and by a factor of <4 in treatment-resistant patients. This result suggests that the quantification of anti-IR(6) antibody titer as a function of time should be investigated further as a test to assess response to Lyme disease therapy or to determine whether a B. burgdorferi infection has been eliminated.     

Comparative distribution of mRNA encoding the growth hormone secretagogue-receptor (GHS-R) in Microcebus murinus (Primate, lemurian) and rat forebrain and pituitary

The forebrain and pituitary sites of synthesis of growth hormone secretagogue-receptor mRNA were identified in four adult lemurs (Microcebus murinus) by in situ hybridisation performed with a radiolabeled cRNA probe transcribed from human Growth Hormone Secretagogue-Receptor cDNA. The cRNA sense and antisense probes were hybridised to cryostat sections containing structures extending from the rostral hypothalamus to its caudal limit as defined by the mammillary bodies. The pituitary gland and areas adjacent to the hypothalamus were also analyzed. For comparative purposes, sections from five adult rats containing these structures were hybridised with the same probes. The results point to a widespread distribution of Growth Hormone Secretagogue-Receptor mRNA in the hypothalamus, hippocampal formation, and cerebellar cortex of both lemurs and rats. As in the rat, specific hybridisation was particularly dense in the arcuate nucleus. Significant species differences were observed in the periventricular nucleus, the ventromedial nucleus, the lateral hypothalamic area, and the pituitary gland. In contrast to the rat, the lemur exhibited marked labelling in the infundibular nucleus, the periventricular nucleus and the pars tuberalis of the pituitary gland, whereas no labeling was detectable in the ventromedial nucleus and the lateral hypothalamic area. These results are discussed in terms of difference between the control of growth hormone secretion, feeding behaviour and seasonal rhythmicity among murine species and primates.     

Detection of subarachnoid haemorrhage with magnetic resonance imaging

OBJECTIVES: To measure the sensitivity and specificity of five MRI sequences to subarachnoid haemorrhage. METHODS: Forty one patients presenting with histories suspicious of subarachnoid haemorrhage (SAH) were investigated with MRI using T1 weighted, T2 weighted, single shot fast spin echo (express), fluid attenuation inversion recovery (FLAIR), and gradient echo T2* sequences, and also by CT. Lumbar puncture was performed in cases where CT was negative for SAH. Cases were divided into acute (scanned within 4 days of the haemorrhage) and subacute (scanned after 4 days) groups. RESULTS: The gradient echo T2* was the most sensitive sequence, with sensitivities of 94% in the acute phase and 100% in the subacute phase. Next most sensitive was FLAIR with values of 81% and 87% for the acute and subacute phases respectively. Other sequences were considerably less sensitive. CONCLUSIONS: MRI can be used to detect subacute and acute subarachnoid haemorrhage and has significant advantages over CT in the detection of subacute subarachnoid haemorrhage. The most sensitive sequence was the gradient echo T2*.     

A role for hormone-sensitive lipase in glucose-stimulated insulin secretion: a study in hormone-sensitive lipase-deficient mice

Endogenous lipid stores are thought to be involved in the mechanism whereby the beta-cell adapts its secretory capacity in obesity and diabetes. In addition, hormone-sensitive lipase (HSL) is expressed in beta-cells and may provide fatty acids necessary for the generation of coupling factors linking glucose metabolism to insulin release. We have recently created HSL-deficient mice that were used to directly assess the role of HSL in insulin secretion and action. HSL(-/-) mice were normoglycemic and normoinsulinemic under basal conditions, but showed an approximately 30% reduction of circulating free fatty acids (FFAs) with respect to control and heterozygous animals after an overnight fast. An intraperitoneal glucose tolerance test revealed that HSL-null mice were glucose-intolerant and displayed a lack of a rise in plasma insulin after a glucose challenge. Examination of plasma glucose during an insulin tolerance test suggested that HSL-null mice were insulin-resistant, because plasma glucose was barely lowered after the injection of insulin. Freshly isolated islets from HSL-deficient mice displayed elevated secretion at low (3 mmol/l) glucose, failed to release insulin in response to high (20 mmol/l) glucose, but had a normal secretion when challenged with elevated KCl. The phenotype of heterozygous mice with respect to the measured parameters in vitro was similar to that of wild type. Finally, the islet triglyceride content of HSL(-/-) mice was 2-2.5 fold that in HSL(-/+) and HSL(+/+) animals. The results demonstrate an important role of HSL and endogenous beta-cell lipolysis in the coupling mechanism of glucose-stimulated insulin secretion. The data also provide direct support for the concept that some lipid molecule(s), such as FFAs, fatty acyl-CoA or their derivatives, are implicated in beta-cell glucose signaling.     

Resection for bronchogenic carcinoma involving the carina: long-term results and effect of nodal status on outcome

OBJECTIVE: Bronchogenic carcinoma in close proximity to or involving the carina remains a challenging problem for thoracic surgeons. The operative procedures to allow complete resection are technically demanding and can be associated with significant morbidity and mortality. Little is known about long-term survival data to guide therapy in these patients. METHODS: We conducted a single-institution retrospective review. RESULTS: We have performed 60 carinal resections for bronchogenic carcinoma: 18 isolated carinal resections for tumor confined to the carinal or proximal main stem bronchus; 35 carinal pneumonectomies; 5 carinal plus lobar resections, and 2 carinal resections for stump recurrence after prior pneumonectomy. Thirteen patients (22%) had a history of lung or airway surgery. The overall operative mortality was 15%, improved from the first half of the series (20%) to the second half (10%), and varied according to the type of resection performed. Adult respiratory distress syndrome was responsible for 5 early deaths, and all late deaths were related to anastomotic complications. In 34 patients, all lymph nodes were negative for metastatic disease; 15 patients had positive N1 nodes, and 11 patients had positive N2/N3 nodes. Complete follow-up was accomplished in 90%, with a mean follow-up of 59 months. The overall 5-year survival including operative mortality was 42%, with 19 absolute 5-year survivors. Survival was highest after isolated carinal resection (51%). Lymph node involvement had a strong influence on survival: patients without nodal involvement had a 5-year survival of 51%, compared with 32% for patients with N1 disease and 12% for those with N2/N3 disease. CONCLUSIONS: This constitutes one of the largest single-institution reports on carinal resection for bronchogenic carcinoma involving the carina. Morbidity and mortality rates are acceptable. The overall survival including operative mortality is 42%. Positive N2/N3 lymph nodes may be a contraindication to surgery because of poor prognosis.     

Emergency pulmonary autograft mitral valve replacement in a child

Mitral valve replacement in small children imposes significant clinical difficulties because of the relatively small mechanical prosthetic valves required and the need for lifelong anticoagulation therapy. A child weighing 10.4 kg presented with thrombosis of her 19-mm mechanical mitral prosthesis 4 weeks after implantation despite appropriate oral anticoagulation therapy. An emergency mitral valve replacement with a pulmonary autograft was successfully performed with encouraging short-term results.