Esophageal source measurement of Tc-99m attenuation coefficients for use in left ventricular volume determinations

A linear attenuation coefficient for water (mu = .15 cm-1) at 140 keV has been used in the determination of left ventricular volumes (LVV) by attenuation-corrected equilibrium methods. This theoretical value ignores the effect of Compton scatter and thus may be too high for human LVV determinations. The effective attenuation coefficient, mu', of the human chest was determined in ten normal volunteers using a Tc-99m esophageal source imaged with a gamma camera. Values for mu' at 30 degrees LAO in end-expiration, quiet breathing, and end-inspiration were .125 +/- .006 cm-1, .125 +/- .005 cm-1, and .113 +/- .007 cm-1, respectively (95% confidence interval). Values of mu' at 45 degrees LAO were .122 +/- .006 cm-1, .119 +/- .007 cm-1, and .099 +/- .009 cm-1, respectively, for the same conditions. The measured value of mu' for the source in a water phantom was .127 +/- .001 cm-1. This suggests that a value of mu' of .125 cm-1 may be appropriate for use in determining LVV in patients.     

Electrical stimulation of the auditory brain stem structure in deafened adults

Electrical stimulation of the cochlear nuclear complex in the brain stem was first accomplished in a female adult deafened by bilateral acoustic tumors. The central electroauditory prosthesis (CEP) was surgically placed at the time of the second tumor removal. The patient has now been receiving electrical stimulation for 5 years. Six more adults have received the CEP at the time of tumor surgery. Clinical results indicate fluctuations in electrical measurements over time, particularly in the first weeks following surgery. Patients are able to sustain tone perception for one minute at all frequencies tested. Auditory discrimination test results reveal above-chance performance on suprasegmental measures, similar to scores achieved by cochlear implant users. No serious complications have occurred to date.     

Results and patterns of perioperative myocardial infarction.

Myocardial injury during a variety of cardiac surgical operations was determined in 57 patients by serial electrocardiograms (ECG's), serial determinations of serum creatine phosphokinase (CPK), and perioperative and postoperative technetium-99m stannous pyrophosphate (PYP) scans. ECG evidence of injury developed in four patients, whereas positive localized injury by PYP scan developed in ten. Twenty-one patients had elevated CPK enzymes postoperatively. The localization of injury by PYP scan correlated with ECG evidence of infarction in only one of four patients. Localized left ventricular injury by PYP scan without new Q waves on the ECG was common (5/12) in patients undergoing aortic valve replacement with perfusion of the coronary arteries. The injury in patients with congenital heart disease occurred at sites of ventricular incision or suggested possible air embolization of the coronary arteries. Perioperative infarction is frequently segmental and nontransmural and occurs in patients with coronary, valvular, and congenital heart disease.     

Effects of localized intracerebral injections of nerve growth factor on the regenerative growth of lesioned central noradrenergic neurones

In the adult rat, the growth of new axonal sprouts from lesioned central catecholamine and indolamine neurones into a denervated iris transplanted to the caudal diencephalon was previously shown to be markedly stimulated by an intraventricular injection of NGF. In the present study a similar stimulatory effect on the regrowth of lesioned central noradrenergic axons has been obtained with 100 times lower doses of the protein, injected locally into the brain tissue close to the cell bodies and axons of the locus coeruleus neurone system. The ingrowth of fibres into the transplant increased similarly when different parts of the noradrenergic neurones (i.e. the cell bodies or the proximal or distal parts of the surviving portions of the lesioned axons) were exposed to NGF, suggesting that the NGF sensitivity is not restricted to any specific part of the neurones. Moreover, experiments with iris transplants incubated in an NGF solution prior to the transplantation suggest a role for the NGF contained in the iris in the process of ‘reinnervation’ of the transplant by central noradrenaline neurones. The possibility of a difference in sensitivity to NGF between different central noradrenaline neurone systems, and between central noradrenaline, dopamine, and indolamine neurone systems is discussed. It was further clarified that the regenerating central neurones — similar to adult peripheral noradrenaline neurones — are most sensitive to the action of NGF during the very early stages of regeneration.