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Biomedical subjects

J E McLennan

Publications and source records attributed to J E McLennan.

At least 19 recordsLinked to original sources
PubMed1999

Determination of saleable product in finished cattle and beef carcasses utilizing bioelectrical impedance technology.

Two experiments were performed to develop prediction equations of saleable beef and to validate the prediction equations. In Exp. 1, 50 beef cattle were finished to typical slaughter weights, and multiple linear regression equations were developed to predict kilograms of trimmed boneless, retail product of live cattle, and hot and cold carcasses. A four-terminal bioelectrical impedance analyzer (BIA) was used to measure resistance (Rs) and reactance (Xc) on each animal and processed carcass. The IMPS cuts plus trim were weighed and recorded. Distance between detector terminals (Lg) and carcass temperature (Tp) at time of BIA readings were recorded. Other variables included live weight (BW), hot carcass weight (HCW), cold carcass weight (CCW), and volume (Lg2/Rs). Regression equations for predicting kilograms of saleable product were [11.87 + (.409 x BW) - (.335 x Lg) + (.0518 x volume)] for live (R2 = .80); [-58.83 + (.589 x HCW) - (.846 x Rs) + (1.152 x Xc) + (.142 x Lg) + (2.608 x Tp)] for hot carcass (R2 = .95); and [32.15 + (.633 x CCW) + (.33 x Xc) - (.83 x Lg) + (.677 x volume)] for cold carcass (R2 = .93). In Exp. 2, 27 beef cattle were finished in a manner similar to Exp. 1, and the prediction equations from Exp. 1 were used to predict the saleable product of these animals. The Pearson correlations between actual saleable product and the predictions based on live and cold carcass data were .91 and .95, respectively. The Spearman and Kendall rank correlations were .95 and .83, respectively, for the cold carcass data. These results provide a practical application of bioelectrical impedance for market-based pricing. They complement previous studies that assessed fat-free mass.

Animals↗
PubMed1984

Acetazolamide and cerebral oxygenation in dogs.

Acetazolamide could theoretically impair oxygen delivery to cerebral tissue by inhibiting local acidification of capillary blood. There is considerable evidence, however, that acetazolamide improves cerebral oxygen tension. This experiment was designed to demonstrate increased deep cerebral oxygen tension after acetazolamide. Three groups of dogs were anesthetized with pentobarbital and ventilated with a respirator. A Teflon-coated stainless steel catheter was placed through a craniotomy into the parietal lobe and advanced into the corona radiata to monitor cerebral pO2 and pCO2 with a mass spectrometer. Group one dogs were normoxic and eucapneic. Group two dogs were hypoxemic, and Group three dogs were hypocapneic. After control cerebral and arterial gas tensions had been recorded, acetazolamide (30 mg kg-1) was injected intravenously. Cerebral gas tensions were monitored continuously and arterial gases were analyzed at 30, 60, 90 and 120 min. Cerebral oxygen tension was not decreased by acetazolamide in any of the dogs. Cerebral carbon dioxide tension was increased by acetazolamide in all dogs. We conclude that acetazolamide does not deplete cerebral oxygen tension even in the face of hypoxemia or acute hypocapnea.

Acetazolamide↗
PubMed1981

Cerebral abscess in children.

We reviewed 94 consecutive episodes of pyogenic brain abscess seen at Children's Hospital Medical Center, Boston, between 1945 and 1980. After 1970, the mortality as reduced from 36% to 14%. Predisposing factors included congenital heart disease, otitic and sinus infections, closed head injuries, and cystic fibrosis. There were seven patients younger than 5 months of age. In one patient with Fallot's tetralogy, an abscess recurred at the site of retained thorium dioxide (Thorotrast) after an 11-year interval. The continuing substantial mortality is attributed to the presence of coma at the time of treatment, hemorrhagic complications of tapping abscesses, and the location of abscesses in deep brain structures. The early detection and successful treatment of brain abscesses in children remains a clinical challenge.

Adolescent↗
PubMed1981

Transcranial enucleation for optic nerve tumor.

Tumors involving both the eye and the optic nerve present a special surgical problem. Conventional enucleation techniques neither permit the surgical exploration of the optic nerve nor assure the complete removal of tumor within the orbit, and they often involve transection through tumor-containing tissue. Transcranial enucleation permits the inspection of the tumor from the back of the globe to the chiasm and its en bloc removal.

Cranial Nerve Neoplasms↗
PubMed1980

Ventilatory response to transient hyperoxia in head injury hyperventilation.

We have measured breath-by-breath instantaneous minute ventilation (VIinst) before, during, and after the administration of 10 breaths of 100% oxygen to seven male patients with head injury hyperventilation. The patients were hypoxemic (PaO2 61.2 +/- 6.3) and hypocapnic (PaCO2 26.6 +/- 5.9) with a respiratory alkalosis (pH 7.53 +/- 0.06) while breathing air. Following the oxygen VIinst fell on the average by 40 +/- 12.7% from 16.06 +/- 3.75 1.min-1 to a minimum of 9.73 +/- 3.20 1.min-1 at 20.4 +/- 2.9 s after the first breath of oxygen. In the majority of our hyperventilating patients, almost all of the resting hyperventilation could be abolished transiently by 100% oxygen. This fall in ventilation represents the peripheral chemoreceptor contribution to resting ventilation and is increased in the head injury patients in comparison with normal subjects breathing air or hypoxic gas mixtures, altitude-acclimatized subjects and patients who are hypoxic because of chronic bronchitis or interstitial lung disease. We suggest that the increased reflex hypoxic drive to ventilation found in our patients is secondary to their cerebral injury, resulting in a reduction of descending cortical inhibitory influences on the medullary respiratory control centers.

Adolescent↗
PubMed1980

Hyperventilation-induced cerebral hypoxia.

Acute respiratory alkalosis decreases cerebral blood flow, increases the affinity of hemoglobin for oxygen, and can result in cerebral hypoxia. This experiment was designed to study this phenomenon in dogs, and to demonstrate the effect of an increased concentration of inspired oxygen. Seven mongrel dogs were anesthetized with pentobarbital and ventilated with a constant volume respirator. A Telfon-coated stainless steel catheter was placed through a craniotomy into the parietal lobe and advanced through the corona radiata to monitor cerebral PO2 and PCO2 with a mass spectrometer. Steady state cerebral and arterial gas tensions were recorded during eucapnic ventilation with air, eucapnic ventilation with 100% oxygen, hypocapnic ventilation with air, and hypocapnic ventilation with 100% oxygen. Decreased cerebral tissue oxygen tension was demonstrated in hypocapnic dogs ventilated with air. When the concentration of inspired oxygen was increased, the relatively small increase in artrial oxygen content was associated with a marked increase in PO2 at the cerebral tissue level. This may be of clinical importance in therapeutic or centrally mediated hyperventilation.

Animals↗
PubMed1979

Intracranial blood clot volume and geometric parameters determined from CT images.

A method of determining intracranial blood vlot volumes from CT images data is presented. This technique avoids dependence on regular geometric volume approximations. Studies are presented on phantoms of known volume (ranging from 3.5 to 108 cm3) but with varying size, shape, and density relative to the surrounding medium. For a wide range of differential densities across the boundary, these phantom results indicate that volumes may be calculated to an accuracy generally better than +/- 2 cm3. A series of clinical cases, principally hypertensive intracranial hemorrhages, have been studied to demonstrate the technique. Three-dimensional axes, which allow clot localization relative to cerebral anatomy, are defined using the anterior/posterior falx attachment points and the dorsum sellae. Clot volume, center of mass, vector of clot expansion, and shift of anatomical structures are determined. Correlation of these data with clinical outcome and surgery is discussed.

Cerebral Hemorrhage↗
PubMed1979

Mechanisms of hyperventilation in head injury: case report and review.

We report the case of a head-injured patient with spontaneous hyperventilation who had recurrent episodes of relative hypoventilation associated with increases in intracranial pressure. Detailed ventilatory studies were performed during the 2nd week after injury. Our findings in this patient prompted us to review the possible mechanisms underlying the observed changes. We suggest that spontaneous hyperventilation in head injury is secondary to a decrease in cortical inhibitory influences on respiratory control mechanisms and that the transient episodes of relative hypoventilation observed in our patient may reflect modified ventilatory responses dependent on the altered state of consciousness. (Neurosurgery, 5: 701--707, 1979).

Adult↗
PubMed1978

Pericollicular syndromes.

Five cases of pericollicular focal hemorrhages are presented with a description of their effect on vision and consciousness. Loss of vision, loss of consciousness, extraocular muscle dysfunction, mutism, and dyslexia may result from expansive lesions near the collicular plate.

Adolescent↗
PubMed1978

Sequelae of metrizamide myelography in 200 examinations.

Twenty pediatric and 180 adult patients underwent myelography using metrizamide (Amipaque). All patients were examined and interviewed before and after the studies. New or exacerbated symptoms attributed to metrizamide myelography were graded according to severity. After the procedure, 51 of 200 patients were unchanged from baseline. Headache was the most common complaint, with an overall incidence of 62%. Nausea and/or vomiting occurred in 38%. Back or leg pain, neck stiffness, temperature elevation, and a variety of less common manifestations were also observed. The incidence of sequelae was higher than in comparable Scandinavian studies with this contrast medium.

Adolescent↗
PubMed1977

Acute neonatal subdural hematoma following breech delivery.

We describe two term infants born by complicated breech deliveries, each of whom suffered an acute subdural hematoma. Both infants required repeated subdural taps; in one case a parietal burr hole was needed. Despite stormy neonatal courses, follow-up examination of the first infant at 26 months showed him to be normal, and in the other only a mild left esotropia was found at 22 months. Acute neonatal subdural hematoma is rare, but symptoms and signs are distinctive and the condition is remediable; immediate recognition and treatment is important.

Acute Disease↗
PubMed1977

Acute posterior fossa epidural hematomas in children.

Epidural hematoma in the posterior fossa is a rare clinical entity requiring immediate surgical intervention to prevent rapid and fatal deterioration. This diagnosis should be considered in children with occipital head trauma who have altered sensorium and evidence of compression of structures within the posterior fossa. Such a clinical setting demands close neurologic observation in a facility where contrast studies and neurosurgical intervention are available. The absence of an occipital skull fracture or the presence of normal pulse rate and blood pressure should not influence the decision. Lumbar puncture is absolutely contraindicated.

Acute Disease↗
PubMed1977

Cortical vein thrombosis in Wegener's granulomatosis. Case report.

A patient with Wegener's granulomatosis is reported in whom a life-threatening cortical vein thrombosis was identified as the process causing acute neurological deterioration. The literature dealing with the neurological and neuropathological manifestations in Wegener's granulomatosis is reviewed.

Adolescent↗
PubMed1976

Rib anomalies in myelodysplasia. An approach to embryologic inference.

An embryologic teratogenic mechanism is reconstructed by utilizing the distribution of anomalous ribs in children with lumbosacral myelomeningocele. This methodology may help to coalesce information from experimental models of teratogenesis and from descriptive human embryology. It provides an approach to deductive reasoning about human structural anomalies based on dynamic embryonic models of teratogenesis. Availability of a developmental time scale, based for example on the distribution of defective ribs, may be useful in the study of other teratogenic and developmental processes.

Abnormalities, Multiple↗