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Biomedical subjects

P Mayo

Publications and source records attributed to P Mayo.

At least 19 recordsLinked to original sources
PubMed2001

Remote substituent effects on the oxymercuration of 2-substituted norbornenes: an experimental and theoretical study.

The effect of a remote substituent on regioselectivity in the oxymercuration of 2-substituted norbornenes has been investigated experimentally and theoretically using density functional theory (DFT). Regioselectivities of 1:1 to 14:1 were observed with various 2-substituted norbornenes. Exo-2-substituted norbornenes always gave greater regioselectivities compared to the corresponding endo-2-substituted norbornenes. The effects of solvents on the regioselectivity have also been examined, and ethereal solvents were found to be the best choice giving the optimal yield and regioselectivity. The relative rate of oxymercuration was estimated by competition experiments. The least reactive substrate (X = OAc) gave the highest regioselectivity. According to DFT predictions, the increased difference between the reaction barriers that results in the greater regioselectivity is correlated directly with the larger polarity of the C=C double bond, which is attacked by the mercury and oxygen. A number of stable exo and endo conformers were predicted. All exo conformers show the same polarity of the double bond, while some endo conformers have a reversal of this polarity. All the conformers except those with the OAc substituent are very close in energy and thus should react. The existence of a mixture of endo conformers with the C=C double bond of opposite polarity clearly explains a decrease in regioselectivity for the endo species. The origin of the greatest regioselectivity for the OAc-2-norbornenes lies in the fact that the conformer with the largest polarity is notably lower in energy than others due to an internal C-H-O hydrogen bond.

Journal Article↗
PubMed1987

Protective effect of BCG in Ahmednagar, India.

As part of a series of investigations to determine the effect of sensitisation by environmental mycobacteria on the efficacy of BCG vaccination in India, this study was carried out in Ahmednagar in Maharashtra. A preliminary skin test survey showed that the rate of sensitisation with age was much lower than in Agra, the site of a previous study, and BCG vaccination scars were associated with considerable enhancement in sensitisation to Tuberculin and other reagents. It was possible to set up prospective BCG vaccination studies in pre-school and primary and secondary school children. Follow up with skin tests were carried out 1 and 2 years later. By the second year, results were obtained almost identical with those 10 years after BCG administration in the UK. On this basis it is proposed that the vaccine is likely to provide a considerable level of protection in Ahmednagar. The results of this study also resemble those obtained in the very youngest age group studied in Agra. The marked differences between Indian towns strongly suggest the influence of exposure to mycobacteria in the environment.

Adolescent↗
PubMed1985

Early thoracotomy and decortication for nontuberculous empyema in adults with and without underlying disease. A twenty-five year review.

The present review deals with 63 adult patients having acute nontuberculous empyema treated by early thoracotomy and decortication, during the period from 1955 through 1979. Group I (38 patients) had postpneumonic empyema, but no underlying disease. Group II (25 patients) had acute empyema and one or more serious associated diseases. Positive cultures were present in 45 of 63 patients (71.4%). Most surgeons have customarily recommended conservative management, especially for patients in Group II, because of the supposedly "high risk" involved in decortication. Consequently, the mortality is extremely high. The empyema must be cured; a "well drained" or "controlled" empyema will not suffice. The severely ill patient can better withstand the ordeal of a major operation than the deleterious effects of a lingering empyema. The critically ill patient is best managed by the primary procedure of open thoracotomy and decortication. The author's experience confirms that such patients can expect an outlook (8% mortality) approaching the zero mortality of Group I patients.

Adolescent↗
PubMed1984

Spontaneous rupture of the spleen presenting as acute thoracic empyema.

Splenic rupture heralded by acute thoracic empyema is rare. A review of 420 cases of spontaneous and delayed splenic rupture failed to list a single such instance. I have reported two unusual cases of spontaneous rupture of the spleen presenting in each instance an acute thoracic empyema without history of trauma.

Acute Disease↗
PubMed1983

Spontaneous pneumothorax in the newborn.

Spontaneous pneumothorax is more frequent during the newborn period than at any other time in childhood. Intubation, vigorous resuscitation, aspiration of meconium-stained amniotic fluid, and hyaline membrane disease have been associated most often with the occurrence of spontaneous pneumothorax; however, it may occur in the absence of any of these precursors. Most pneumothoraces occur in term babies (64%); however, the premature infant is more susceptible. Signs and symptoms are due chiefly to lung compression and include grunting, tachypnea, cyanosis, and retraction. The accumulation of air serves as an intrathoracic space-occupying lesion, an emergency condition that demands prompt diagnosis and treatment.

Female↗
PubMed1982

Acute empyema in children treated by open thoracotomy and decortication.

Acute nontuberculous empyema treated conventionally by thoracentesis, thoracostomy drainage, and antibiotics has an unacceptably high rate of morbidity and mortality. Early open thoracotomy to eliminate the empyema with decortication of the fibrinous peel and reexpansion of the lung has proven safe and effective for 25 years. The goals of treatment of acute nontuberculous empyema are: (1) to save life, (2) to eliminate the empyema, (3) to reexpand the trapped lung, (4) to restore mobility of the chest wall and diaphragm, (5) to return respiratory function to normal, (6) to eliminate complications or chronicity, and (7) to reduce the duration of hospital stay. Our studies confirm the normal values to be expected in patients who have had complete recovery from the acute empyema, and we lay to rest any concern that decortication might, in time, limit pulmonary function. We present the cases of 21 children who had acute and mature empyemas that were treated by open thoracotomy and decortication, with an average follow-up of 18 years, among whom there were no deaths or complications.

Acute Disease↗
PubMed1982

Middle lobe syndrome: diagnosis and management.

Ninety-eight patients with middle lobe syndrome were reviewed. There were 31 male and 67 female patients ranging in age from 4 to 80 years. The most common presenting symptoms were cough, dyspnea, fever, hemoptysis, and chest pain. Diagnostic studies included chest roentgenogram, bronchoscopy, and bronchography. Sixty-five patients had full recovery following intensive medical therapy. Thirty-one patients underwent surgical resection for persistent disease. There were five post-operative complications and 1 death in this series.

Adolescent↗
PubMed1982

Surgical treatment of anterior diaphragmatic hernia.

Of ten patients with anterior diaphragmatic hernia treated by operation, only three had shortness of breath and chest pain. The remainder of the patients were referred to us because of a roentgenographic abnormality. All patients have had follow-up of between six months and 11 years without recurrence. Surgical repair is recommended to prevent incarceration and strangulation.

Adult↗