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Biomedical subjects

W Chan

Publications and source records attributed to W Chan.

At least 145 records · Page 8Linked to original sources
PubMed1984

Count-based left ventricular volume determination utilizing a left posterior oblique view for attenuation correction.

This study aimed to determine the inherent error of the left ventricular volume measurement from the gated equilibrium blood pool scintigram utilizing the count-based technique. The study population consisted of 26 patients who had undergone biplane contrast ventriculography. The patients were imaged with a parallel-hole collimator in the left anterior oblique position showing the septum to best advantage. A reference blood sample was counted and radionuclide volumes calculated without correction for attenuation. Attenuation corrected volumes were derived with the factor 1/e-mud, where d = distance from skin marker to center of the left ventricle in the orthogonal left posterior oblique view and mu = linear attenuation coefficient. A series of mu values from 0.08 to 0.15 cm-1 was evaluated. There was a trend toward improvement in the r value and lowering of the SEE with attenuation correction. The tightest 95% confidence limits achieved for an end-diastolic 150-ml ventricle were +/- 44 ml, and for an end-systolic 75-ml ventricle +/- 32 ml. In view of the magnitude of inherent error, the count-based volume measurement may be more suitable for group analyses and in cases in which an individual patient serves as his own control.

Adult↗
PubMed1984

The echocardiographic features of an aneurysm of the inter-atrial septum.

The echocardiographic features of a surgically confirmed case of an aneurysm of the inter-atrial septum presenting as a persistent right atrial lesion were described. The lesion appeared cystic and could be differentiated from solid tumours. In contrast to other reported cases of smaller aneurysms, the lesion in this patient remained in the right atrium and did not show any phasic variation during the respiratory cycle because of its larger size. A review of the reported echocardiographic features of intra-cavitary right atrial tumours and pseudotumours was made. This highlighted distinguishing features that could be used in the differential diagnosis of space-occupying lesion within the right atrium.

Adult↗
PubMed1984

Effects of three feeding schedules on tumor and host of Lewis lung carcinoma-bearing mice.

The effect of three feeding schedules on tumor and host were examined in Lewis Lung bearing (TB) and nontumor bearing (NTB) C57/B1 mice. Both NTB and TB animals were divided into three groups: the control groups which were fed ad libitum; the intermittent fed (IMF) groups were fed for 32 hr and fasted for 16 hr in each 48-hr cycle, and the alternate day fed (ADF) groups were fed for a 24-hr interval in each 48-hr cycle. The animals were killed at the end of the fifteenth day, following a fed day for all groups. In the NTB groups, only the ADF group showed decreased food intake and lower body weight gain as compared to their control group. In the TB mice, as compared to their control group, the IMF group showed a significant reduction in the mean tumor weight with no change in the mean host weight, even though the daily food intakes of these two groups were the same over the experimental interval. In contrast, the ADF group showed reductions in both host and tumor weights as compared to their control group. The tumor to host weight ratios were significantly reduced for both the IMF and ADF groups as compared to the ratios found for the control groups, which suggests a differential effect on the tumor and on the host due to the feeding schedule. As assessed by the protein, RNA, and DNA concentrations, no compositional differences were noted for the tumors obtained from the animals that were maintained on each of the three different feeding schedules. In the NTB mice, no differences in tissue leucine (Leu) oxidation occurred between the groups for liver and skeletal muscle, whereas in the TB animals in vitro Leu oxidation capability by skeletal muscle specimens was markedly enhanced in the ADF group, but no difference was noted for the IMF group of the TB mice when compared to the control group. Taken together, these results suggest that the 32-hr fed:16-hr fast schedule (IMF) was beneficial and the 24-hr fed:24-hr fast schedule was detrimental compared to the ad libitum feeding schedule with respect to tumor and host relationships.

Animals↗
PubMed1983

Changes in plasma biochemistry in horses competing in a 160 km endurance ride.

Plasma biochemical values were measured in 14 horses, before a 160 km endurance ride, immediately after 85 km, immediately after 160 km, after 30 min recovery period and the day after the ride. For statistical analysis, a group of 7 horses that completed the ride at a mean speed of 234 metres per min (m/min) (Fast Group) was compared with 7 horses that completed the ride at a mean speed of 144 m/min (Slow Group). Estimations were made of sodium, potassium, chloride, bicarbonate, glucose, creatinine, urea, bilirubin, iron, total protein, albumin, calcium, phosphate, cholesterol, alkaline phosphate, gammaglutamyl transferase, lactate dehydrogenase, alpha hydroxybutyrate dehydrogenase, asparate amino transferase, alanine amino transferase, cortisol and insulin. Disturbances in biochemical values associated with endurance exercise reflected dehydration, hepatic dysfunction, reduced renal function and muscle damage. The faster the speed of exercise, the greater was the stress as reflected by cortisol values. The Fast Group of horses also demonstrated lower glucose and higher CK and LD values than the Slow Group of horses. However, biochemical values the day after the ride were similar to values before the ride.

Animals↗
PubMed1982

Rapid loss of delta-aminolevulinic acid dehydratase activity in primary cultures of adult rat hepatocytes: a new model of zinc deficiency.

Nonproliferating cultures of adult rat hepatocytes were found to lose 60-70% of cell-associated zinc during their first 24 h of incubation in standard, serum-free medium. The loss of zinc was accompanied by a profound loss (greater than 95%) in the activity of the zinc metalloenzyme, delta-aminolevulinic acid dehydratase, as well as a loss (greater than 85%) in the cellular content of immunoreactive delta-aminolevulinic acid dehydratase protein. Restoration of cellular zinc content by the addition of zinc to the culture medium partially prevented the losses of both delta-aminolevulinic acid dehydratase activity and immunoreactive protein. Since the spontaneous, selective loss of cellular zinc appears to have specific effects on a relevant hepatic function, this culture system constitutes a novel in vitro model of zinc deficiency in mature liver.

Animals↗
PubMed1982

Radionuclide evaluation of postextrasystolic potentiation of left ventricular function induced by atrial and ventricular stimulation.

Postextrasystolic potentiation of left ventricular function induced by ventricular and atrial stimulation was compared in 10 patients using radionuclide ventriculography. After insertion of pacing wires, a preliminary radionuclide ventriculogram was obtained and then ventricular and atrial trigeminy was induced in random order, each with identical R-R coupling intervals, each for 6 to 10 minutes. During the stimulation studies, radionuclide data were acquired in electrocardiographic gated list mode format. Left ventricular ejection fraction and relative end-diastolic and end-systolic volume changes were measured for each reformatted composite sinus, atrial and ventricular premature beat and potentiated beat. The volume changes were normalized to the count-based values obtained for the sinus beat of the appropriate study. Postextrasystolic potentiation induced by either ventricular or atrial stimulation was characterized by similar significant increases in left ventricular ejection fraction (mean +/- standard deviation 7 +/- 3 percent, p less than 0.01 versus 7 +/- 5 percent, p less than 0.01; difference not significant [NS]) and decreases in relative end-systolic volume (-12 +/- 12 percent, p less than 0.01 versus -12 +/- 8 percent, p less than 0.01; NS) but little change in relative end-diastolic volume (+5 +/- 10 percent, NS versus +4 +/- 7 percent, NS; NS). This was despite a longer compensatory pause (1,120 +/- 220 versus 1,050 +/- 190 ms, p less than 0.01) after the ventricular premature beat. It is concluded that there is no difference in the postextrasystolic potentiation induced by atrial or ventricular premature stimulation.

Adult↗
PubMed1982

Comparison of the osteoblastoma in gnathic and extragnathic sites.

A comparative analysis of extragnathic and gnathic osteoblastomas showed that the lesion was similar clinical, radiologic, and histologic features in these two sites. Osteoblastomas in both areas most commonly present as painful swellings and appear radiographically as lucent or sclerotic lesions, depending on the degree of calcification. The typical histologic appearance is of a highly vascularized stroma with osteoblasts and abundant trabeculae of osteoid and immature bone in various degrees of calcification. These lesions are most often treated conservatively by curettage or local excision. The results of this comparison indicate that oral and maxillofacial surgeons can draw on the wider experience of other types of surgeons when treating this rare lesion.

Adolescent↗
PubMed1982

Scintigraphic demonstration of ventriculo atrial conduction in the ventricular pacemaker syndrome.

A patient with the sick-sinus syndrome was evaluated because of symptomatic deterioration after insertion of a ventricular demand pacemaker. Clinical features of the ventricular pacemaker syndrome were recognized and confirmed by electrophysiological and hemodynamic studies. Phase analysis--a new technique for detecting patterns of cardiac emptying from gated cardiac blood-pool scintigrams--demonstrated a pattern consistent with 1:1 ventriculo-atrial conduction. Phase analysis of the gated cardiac blood-pool scintigram may be useful in the assessment of patients with ventricular demand pacemakers who complain of fatigue and effort intolerance.

Aged↗
PubMed1980

Haemodynamic and hormone responses to acute and chronic frusemide therapy in congestive heart failure.

1. Since important interrelationships between haemodynamic and hormone indices are possible in cardiac failure, measurements of cardiac output, mean pulmonary artery pressure, plasma renin activity, angiotensin II and aldosterone were carried out before and during acute and chronic frusemide therapy in patients with oedematous heart failure who had been given digoxin. 2. Cardiac output fell significantly 90 min after acute frusemide infection, then returned to baseline. Mean pulmonary artery pressure declined steadily throughout the 4 h of observation. 3. These haemodynamic changes occurred in the absence of major hormonal fluctuations and related presumably to direct vascular and diuretic actions of frusemide. 4. With more chronic (8-10 days) oral frusemide therapy, reciprocal changes between haemodynamic and hormone indices were observed. As the diuretic response to frusemide diminished, cardiac output and pulmonary artery pressure declined whereas the renin-angiotensin system was activated. Statistically significant inverse correlations were observed between these haemodynamic and hormone indices. 5. In both acute and chronic phases of the study, fluctuations in aldosterone levels were regulated by the renin-angiotensin system whereas ACTH, plasma potassium and plasma sodium played, at best, supportive roles.

Adult↗
PubMed1980

Myeloproliferative and lymphoproliferative disorders in the same patient.

A 67-year-old man developed a Philadelphia-negative myeloproliferative disorder which initially manifested as marked thrombocytosis, followed two years later by marked leucocytosis. He subsequently developed an IgG lambda plasma cell dyscrasia together with a monoclonal proliferation of circulating lymphocytes with IgM kappa surface immunoglobulin. The lymphoid neoplasm was associated with a rapidly progressive and fatal course.

Aged↗
PubMed1980

Effects of hypotensive anesthesia in anterior maxillary osteotomy.

Deliberate hypotension, as a means of reducing loss of blood, providing a more ideal operative field, and shortening operating time, has been used in other surgical disciplines, such as neurosurgery, vascular surgery, and orthopedic surgery. This controlled study compared the effects of hypotensive and normotensive anesthesia on loss of blood, quality of surgical field, and length of surgery in one type of orthognathic surgical procedure--the anterior maxillary osteotomy.

Anesthesia, Dental↗
PubMed1979

Haemodynamic effects of acute beta-adrenergic receptor blockade in congestive cardiomyopathy.

Acebutolol ('Sectral'), a cardioselective beta-blocking drug, was administered intravenously in a dose of 25 mg to 10 patients with congestive cardiomyopathy. All of them were in a stable condition on antifailure regimens. The drug resulted in a statistically significant decline in left ventricular contractility as judged by peak left ventricular dP/dT and the contractility index. The mean aortic blood pressure also fell. There was a significant increase in end-diastolic and end-systolic left ventricular volumes. Mean values for heart rate, ejection fraction, left ventricular stroke work index, and cardiac output also fell, but the results were not statistically significant. Left ventricular distensibility as judged by the slope of the diastolic pressure-volume relation also improved significantly. A reduction in myocardial energy requirements, improved compliance, and lowering of arterial pressure would be haemodynamically advantageous. However, further cardiac dilatation and reduction contractility--the basic defects in congestive cardiomyopathy--could lead to further deterioration.

Acebutolol↗