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Biomedical subjects

J A Alexander

Publications and source records attributed to J A Alexander.

At least 163 records · Page 9Linked to original sources
PubMed1980

Pulmonary metastases in childhood sarcoma.

A retrospective analysis of 56 patients less than 19 years old with pulmonary metastases from previously diagnosed sarcomas was performed. Thirty patients had primary osteogenic sarcoma. Eighteen of them underwent a total of 37 thoracotomies. Overall survival was 20%. Twelve patients were noted to have metastatic Wilms' tumor, and 5 of them underwent 7 thoracotomies. This group had a 25% overall survival. Six patients had pulmonary metastases from Ewing's sarcoma. Four of these required pulmonary resection. The overall survival in these patients was 50%. The remaining 8 patients had pulmonary resection for various soft tissue malignancies, with an overll survival of 50%. The results of this review indicate a role for aggressive pulmonary resection in patients in whom the primary tumor is controlled and there is no other evidence of metastatic disease. The frequency of bilaterality and multicentric implants in patients with osteogenic sarcoma and Wilms' tumor suggest the efficacy of a median sternotomy approach in these patients.

Adolescent↗
PubMed1980

Effects of N,N'-bis(2-chloroethyl)-N-nitrosourea and 2-[3-(2-chloroethyl)-3-nitrosoureido]-2-deoxy-D-glucopyranose upon the proliferation, DNA synthesis, and viability of cultured sensitive and resistant L1210 cells.

The effects of N,N'-bis(2-chloroethyl)-N-nitrosourea and chlorozotocin upon the proliferation, DNA synthesis, and viability of cultured cells of a sensitive line of L1210 leukemia, a line partially resistant to N,N'-bis(2-chloroethyl)-N-nitrosourea, and a line resistant to cyclophosphamide were determined. The results indicate that neither the effect upon proliferation nor the effect upon DNA synthesis is a good predictor of the extent of cell kill. The similarity of the effects of N,N'-bis(2-chloroethyl)-N-nitrosourea upon these two parameters for the three cell lines indicates that the sensitive and resistant cells are affected to approximately the same extent, but more of the resistant cells survive. Additional studies are required to seek the reasons for this differential survival.

Animals↗
PubMed1979

The mechanism of apparent right bundle branch block after transatrial repair of tetralogy of Fallot.

The electrocardiographic pattern of right bundle branch block (RBBB) is routinely observed after transatrial repair of tetralogy of Fallot even though no ventriculotomy has been performed. The mechanism of this conduction disturbance was studied in 16 patients with tetralogy of Fallot and one patient with infundibular pulmonic stenosis. Preoperative ECGs and vectorcardiograms showed right ventricular hypertrophy and no RBBB. Epicardial activation maps were obtained before and after total surgical repair in all patients and after infundibular resection but before closure of ventricular septal defect (VSD) in four of these patients. After infundibular resection, RBBB appeared and activation was markedly delayed (greater than 30 msec) over the pulmonary outflow tract, but was unchanged over the body of the right ventricle. No further changes in ventricular activation occurred after closure of the VSD. This study shows that RBBB after transatrial repair of tetralogy of Fallot is usually produced by infundibular resection, but not by VSD closure, and is associated with delayed activation of the pulmonary outflow tract and base of the right ventricle which results from damage to portions of the right ventricular conduction system.

Adolescent↗
PubMed1979

Apperceptive signals demonstrating the dynamic disturbance of myocardial ischemia.

Analog pressure signals (catheter-tip manometers) from the left atrium, left ventricle, and aorta and a flow signal from the arota were obtained in 25, open-chest, anesthetized dogs in which 115 episodes of ischemia were produced in an area of the left ventricle subtended by the distal left anterior descending coronary artery and its last major diagonal branch. The left ventricular pressure and its first derivative (dP/dt) were displayed as an X-Y loop. The character of this loop went through a unique series of dynamic changes in 110 of the 115 ischemic episodes, indicating that this is a useful tool for monitoring myocardial ischemia. Spectrum pairs of the above signals were analyzed with digital computational transfer functions in 14 ischemic episodes of three experiments and preliminary assessment reveals unique pole and zero changes in many pairs during each episode which also may prove to be a useful indicator of the hemodynamic disturbance incurred during myocardial ischemia.

Analog-Digital Conversion↗
PubMed1978

Rate of DNA synthesis as an indication of drug toxicity and as a guide for scheduling cancer therapy.

The rates of incorporation of [C3H3]thymidine into the DNA of tissues of normal mice at various times after single doses of several drugs (adriamycin, vincristine, methotrexate, 5-fluorouracil [5-FU], melphalan, CCNU, and chlorozotocin) that have some clinical activity against cancer have been determined and are considered to be indicative of the "degree of normalcy" of the respective tissues at those times. These experiments show that there are some differences and some similarities in the effects of the agents upon the various tissues of the mouse. Each of the agents caused early inhibition of incorporation of [C3H3]thymidine followed by stimulation of such incorporation by intestinal mucosa and marrow, but the timing and the extents of inhibition and stimulation differed for the various agents. Except for CCNU, the preceding description would also apply to the effects upon liver and lungs, but the stimulation was delayed in comparison to that of intestinal mucosa and marrow. Early inhibition with little subsequent stimulation occurred in the spleen, kidneys, and heart. For all tissues, recovery was slower and less extensive after CCNU than after the other agents. The data obtained with the single agents were used for setting up experiments in which a single dose of one agent was followed after selected intervals of time with a single dose of a second agent. The combination of adriamycin plus 5-FU was less toxic when the two agents were given simultaneously than when the 5-FU was given 24-96 hours after the adriamycin, while for the combination of adriamycin plus CCNU there was less toxicity if the CCNU was administered 24 hours after the adriamycin rather than simultaneously with it. When a combination of a single dose of methotrexate and a single dose of 5-FU was administered to mice, the lethality was greater when the two agents were administered 120 hours apart than when the two agents were given simultaneously or were separated by 24 or 48 hours; this was true regardless of which agent was administered first. These results are consistent with what might be predicted upon the basis of the data obtained for the single agents in this study and of what is known about the mechanisms of action of these agents and of the effects of the agents in relation to cell and tissue kinetics. These results indicate that patterns of thymidine fixation by tissues following single doses of agents might be useful in scheduling multiple-drug therapy to minimize host toxicity.

Animals↗
PubMed1977

One hundred kidney transplants in the Belfast city hospital.

100 kidney transplants have been carried out on 91 patients (7 had 2 transplants and 2 had 3 transplants). 4 transplants were from living related donors and 96 from cadavers. 76 patients survive, all but one with functioning kidneys. The cumulative survival of patients was 82% at 2 years and 80-7% at 5 years. 8 patients died with functioning grafts, and 2 of the other deaths took place more than 3 months after removal of a rejected kidney and resumption of haemodialysis. There were no deaths from sepsis in the first 60 days after transplantation. The cumulative survival of all grafts was 82-1% at 2 and 5 years. The cumulative survival of first grafts was 82-5% at 2 and 5 years.

Adolescent↗
PubMed1977

Thromboembolic phenomena in patients with prosthetic aortic valves who did not receive anticoagulants.

Seventy-two patients with Starr-Edwards aortic prostheses of the 2300 series were followed for 1 to 73 months (average, 22 months) without receiving anticoagulants. Nine patients had clinical evidence of an embolic episode (12.5%). One of these patients died, and 5 were left with a significant residual neurological deficit. Two other patients had hemiparesis but recovered fully. Only 1 episode could be considered minor. The reported lower incidence of thromboembolism in patients receiving this prosthesis with adequate anticoagulation has now led us to reverse our previous position and recommend anticoagulation for patients receiving Starr-Edwards aortic prostheses.

Adult↗
PubMed1977

The locus of unique green in deuteranomalous trichromats.

A method of color naming was used to determine the spectral locus for unique green (UG) as it was perceived by 20 color normals and 24 deuteranomalous trichromats. The loci for the normal group were distributed bimodally, as earlier investigators had reported, and a bimodal distribution was also found for the deuteranomalous group. In the latter group, UG was located at long wavelengths only by those who had been classified as mild deuteranomals according to several clinical criteria. Those who located UG at shorter wavelengths included individuals whose defects ranged from mild to severe. This result is discussed in the context of theories of deuteranomaly and is presented as further evidence for the existence of 2 types of deuteranomaly.

Adolescent↗
PubMed1976

Dissociation and delayed conduction in the canine right bundle branch.

Bipolar electrograms were recorded from five to six sites on the septal right bundle branch (RBB) using a multielectrode patch in ten mongrel dogs. Antegrade activation was recorded along the right bundle during sinus rhythm and during right atrial pacing at varying heart rates. Retrograde activation was produced by pacing from right ventricular epicardium. Right bundle conduction velocities varied from 1.4 to 3.3 m/sec (mean 2.0 m/sec) for antegrade conduction and from 1.8 to 2.7 m/sec (mean 2.1 m/sec) for retrograde activation. Varying degrees of conduction delay were elicited by premature stimulation and mechanical pressure to the right bundle. The conduction delays occurred over small segments of the right bundle branch with regeneration of normal propagation velocity distal to the region of block. The conduction delays were associated with fragmentation of the RBB electograms with initiation of delayed activation waves which traveled variable distances antegrade and retrograde. These data show that stress-induced longitudinal dissociation may produce delayed activation waves within the right bundle branch which may simulate re-entrant arrhythmias.

Animals↗
PubMed1976

Results of treatment of primary carcinoma of the lung. Analysis of 3,000 cases.

Three thousand patients with primary carcinoma of the lung entered in the Armed Forces Central Medical Registry are reported. Forty-one per cent had squamous cell, 28.5 per cent adenocarcinoma, 25.2 per cent small cell/undifferentiated, and 4.9 per cent miscellaneous cell types. When first seen, 71.1 per cent had no organ metastases and 50.6 per cent no lymph node metastases. Over-all survival rate was 18.2 per cent at 5 years and 14.5 per cent at 10 years. Survival following definitive resection, palliative resection, definitive radiation, palliative radiation, and chemotherapy was determined both in the presence of mediastinal nodal involvement and in the absence of mediatinal nodal involvement. Where resection for cure could be carried out, 5 year survival rates of 48.8 per cent were possible. The factors affecting this improved outlook in our military population are discussed and, in general, appear to be related to a ready accessibility of medical care and the necessity, because of global commitments, of establishing an early diagnosis. Cell type ecerted some influence on survival, but the major determinant appeared to be the absence of involved nodes at the time of the operation.

Adenocarcinoma↗
PubMed1976

Paecilomyces varioti endocarditis on a prosthetic aortic valve.

Fungal endocarditis following prosthetic valve surgery has assumed increased importance as a cause of postoperative death. We present, to our knowledge, the first case of the fungus Paecilomyces varioti producing endocarditis on a prosthetic aortic valve. This seems to be an extremely indolent organism which exhibits an apparent response to antibiotic therapyl. In vitro evidence suggests that this fungus is sensitive to attainable serum levels of both 5-fluorocytosine and amphotericin B. However, after viewing the extracted valve and the devastating embolic phenomenon in our patient, we believe that medical therapy alone would not suffice. Thus we suggest that prompt valve replacement be performed in future cases.

Aortic Valve↗
PubMed1976

Doppler ultrasonic flow detection as an adjunct in the diagnosis of patent ductus arteriosus in premature infants.

Since ligation of a patent ductus arteriosus in the neonate with idiopathic respiratory distress syndrome seems to improve the clinical condition of the infant, we have attempted to identify those neonates earlier with the noninvasive Doppler ultrasonic technique, recording brachial arterial flow signals. Sixteen patients were studied. In the 5 with reversed brachial flow who were operated upon, ligation of a PDA resulted in improvement and postoperative correction of brachial flow reversal as evidenced by the Doppler ultrasonic technique.

Doppler Effect↗
PubMed1975

Shunt dynamics in experimental atrial septal defects.

Inorder to study the hemodynamic variables involving the magnitude, direction, and timing of phasic shunt flow, both the interatrial pressure gradient and blood flow along with other pertinent hemodynamic variables were measured instantaneously across a surgically created atrial septal defect (ASD) in seven awake dogs. Atrial and ventricular pacing and infusion of phenylephrine and isoproterenol were used to alter hemodynamic conditions. The wave form of phasic ASD flow was similar both in configuration and timing to the interatrial pressure gradient. During the cardiac cycle, both left-to-right (L-R) and right-to-left (R-L) shunting occurred: atrial contraction augmented L-R flow; the onset of ventricular contraction was associated with R-L flow; during the latter part of ventricular contraction, flow returned to L-R with the maximum L-R shunting occurring in early diastole. Tachycardia, infusion of phenylephrine and isoproterenol did not alter the phasic flow pattern. Both spontaneous and positive pressure respiration decreased net L-R shunting.

Animals↗