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Biomedical subjects

A Sharman

Publications and source records attributed to A Sharman.

18 recordsLinked to original sources
PubMed2003

Thermoenergetics of pre-moulting and moulting kookaburras (Dacelo novaeguineae): they're laughing.

We examined the effect of temperature on resting metabolic rate in seven field-captured laughing kookaburras (Dacelo novaeguineae) during late winter and early spring. Basal metabolic rate averaged 201+/-3.4 ml O(2) h(-1) (0.603 ml O(2) g(-1) h(-1)). Overall thermal conductance (K(o)) declined with ambient temperature ( T(a)) and averaged 0.026 ml O(2) g(-1) h(-1) degrees C(-1) at T(a)s<10 degrees C. Day-night differences in body temperatures (2.6 degrees C) and in alpha-phase versus rho-phase minimum metabolic rates were much greater (33%) than predicted for 340-g nonpasserine birds and suggest that these animals operate as low-metabolic intensity animals in their rest phase, but normal-metabolic intensity animals during their active phase. Metabolic rate was measured in four of the same birds undergoing moult. Thermal conductance increased to 60% above pre-moult values about 6 weeks after moult began. Basal metabolic rate of moulting birds showing peak thermal conductance readings averaged 17 ml O(2) h(-1) higher than pre-moult measurements. Although this increase was not statistically significant, we believe the moult costs of kookaburras are too low to overcome the inherent variability of BMR determination. We suggest that moult costs of kookaburras are only somewhat higher than the measured costs of protein synthesis of other endotherms.

Animals↗
PubMed2001

A method to estimate urinary electrolyte excretion in patients at risk for developing cerebral salt wasting.

OBJECT: Two major criteria are necessary to diagnose cerebral salt wasting (CSW): a cerebral lesion and a large urinary excretion of Na+ and Cl- at a time when the extracellular fluid (ECF) volume is contracted. Nevertheless, it is difficult for the physician to confirm from bedside observation that a patient has a contracted ECF volume. Hyponatremia, although frequently present, should not be a criterion for a diagnosis of salt wasting. A contracted ECF volume is unlikely if there are positive balances of Na+ and Cl-. The goal of this study was to assess the accuracy of calculating balances for Na+ plus K+ and of Cl- over 1 to 10 days in an intensive care unit (ICU) setting. METHODS: A prospective comparison of measured and estimated quantities of Na+ plus K+ and of Cl- excreted over 1 to 10 days in 10 children and 12 adults who had recently received a traumatic brain injury or undergone recent neurosurgery. Plasma concentrations of electrolytes were recorded at the beginning and end of the study period. The total volumes infused and excreted and the concentrations of Na+, K+, and Cl- in the infusate were obtained from each patient's ICU chart. The electrolytes in the patients' urine were measured and calculated. Correlations between measured and calculated values for excretions of Cl- and of Na+ plus K+ were excellent. CONCLUSIONS: Mass balances for Na+ plus K+ and for Cl- can be accurately estimated. These data provide information to support or refute a clinical diagnosis of CSW. The danger of relying on balances for these electrolytes measured within a single day to diagnose CSW is illustrated.

Adolescent↗
PubMed2000

Crab stomach pyloric muscles display not only excitatory but inhibitory and neuromodulatory nerve terminals.

Movements of the foregut in crustaceans are produced by striated muscles that are innervated by motor neurons in the stomatogastric ganglion (STG). Firing of the STG motor neurons generates excitatory junctional potentials (EJPs) in the stomach muscles. We now provide evidence for the existence of separate inhibitory and neuromodulatory innervations of some pyloric muscles in the foregut of several crabs, Callinectes sapidus, Cancer magister, and Cancer borealis. Electron microscopic examination of several pyloric muscles revealed three distinct types of nerve terminals. Excitatory terminals were readily identified by the spherical shape of their small, clear synaptic vesicles. These terminals also housed a few large dense core vesicles. Inhibitory nerve terminals were recognized by the elliptical shape of their small, clear synaptic vesicles, and contacted the muscles at well-defined synapses equipped with dense bar active zones. Bath application of GABA reduced the amplitudes of EJPs in a pyloric muscle of C. borealis, consistent with the presence of GABAergic inhibitory innervation. Neuromodulatory terminals were characterized by their predominant population of large dense and dense core vesicles. These terminals formed synapses with presynaptic dense bars on the muscle, as well as on the excitatory and inhibitory nerve terminals. The presence of the inhibitory and neuromodulatory terminals creates a functional context for previously described reports of neuromodulatory actions on stomach muscles and suggests that the transfer function from STG motor patterns to pyloric movement may be orchestrated by a complex innervation from sources outside of the STG itself.

Animals↗
PubMed2000

Endoscopic third ventriculocisternostomies In the infant: pre- & post-operative magnetic resonance imaging EvaluationElective project

PURPOSE: To determine whether it is possible to select patients with obstructive hydrocephalus, in the under 1 age group for endoscopic third ventriculocisternostomy (ETV) using pre-operative T2 weighted turbo spin echo (T2W-TSE) sagittal sequence Magnetic Resonance (MR) imaging; and to assess ventriculocisternostomy patency using post-operative T2W-TSE MR.PATIENTS AND METHODS: A retrospective review of MR examinations and clinical notes of 11 patients under 1 year of age who had ETV, was performed. The post-operative flow MR images were divided into the presence or absence of flow-related signal changes.RESULTS: In 6 of the 11 patients, ETV was successful (54.5%) i.e. no VP shunt or revision of the ETV was required. 9 patients had post-operative T2W-TSE MR examinations - 8 of these 9 MR studies correlated to the clinical situation (89%). The remaining MR examination showed a CSF flow void but the ETV failed at 3 weeks. CONCLUSION: Pre-operative MR using T2W-TSE to select suitable candidates for ETV improves the success rate from < 40% to 54.5%. Post-operatively MRI is a good predictor of whether the ETV has been successful or not.Sharman, A. (2000). Clinical Radiology55, 989. Copyright 2000 The Royal College of Radiologists.

Journal Article↗
PubMed2000

Determinants of successful direct current cardioversion for atrial fibrillation and flutter: the importance of rapid referral.

Direct current (DC) cardioversion is an effective means of restoring sinus rhythm in patients with atrial fibrillation or flutter; however, the existing literature contains conflicting evidence on which factors are useful predictors of success. In a study of 171 patients undergoing DC cardioversion, we found that duration of arrhythmia prior to DC cardioversion was the only significant predictor of both successful cardioversion and subsequent maintenance of sinus rhythm (P < 0.001). Rapid DC cardioversion after the onset of atrial fibrillation or flutter significantly increases the likelihood of a successful outcome in both the short-term and long-term.

Aged↗