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Biomedical subjects

J C Leonard

Publications and source records attributed to J C Leonard.

At least 19 recordsLinked to original sources
PubMed1992

Clastogenicity of lead chromate particles in hamster and human cells.

Several insoluble compounds of chromium, such as lead chromate, are respiratory carcinogens in experimental animals and suspected to be so in humans. Lead chromate induces neoplastic transformation in cultured cells but the mechanism of genotoxicity is unknown. We examined the effect of lead chromate on the integrity of chromosomes of Chinese hamster ovary (CHO) and human foreskin fibroblasts (HFF) after a 24-h exposure. At 0.4 microgram/cm2, 0.8 microgram/cm2, 2 microgram/cm2 and 8 microgram/cm2 lead chromate particles reduced survival of CHO cells to 86%, 62%, 2% and less than 1% respectively. These concentrations induced a dose-dependent 4-19-fold increase in the percent metaphases with damage. The HFF cells exhibited higher sensitivity in both cytotoxicity and clastogenicity. The spectrum of damage observed for both cell types was primarily achromatic lesions affecting one or both chromatids. To test for particle dissolution effects, CHO cells were treated for 24 h with either clarified medium that had been incubated for 24 h with lead chromate particles, or clarified medium that had been pre-conditioned by CHO cells treated with lead chromate particles for 24 h. No damage was detected in these cells, indicating that extracellular dissolution into ionic lead and chromate did not contribute to the genotoxicity. This is consistent with a previous study in which scanning electron micrographs illustrated internalization of the particles. These results suggest that clastogenesis may be a mechanism for lead chromate induced carcinogenesis.

Animals↗
PubMed1992

Rapid determination of glomerular filtration rate in infants using Tc-99m DTPA.

Glomerular filtration rate obtained by using Tc-99m DTPA was compared with that obtained from Schwartz's formula using serum creatinine and length in 21 infants (age range, 3 to 348 days). The GFR (mean +/- SD) obtained by Tc-99m DTPA was 76 +/- 37 ml/min per 1.73m2 and by the Schwartz formula was 83 +/- 49 ml/min per 1.73m2. GFR by Tc-99m DTPA method overestimated GFR by 3.6% compared to the Schwartz method. The imaging technique and the advantages are discussed.

Glomerular Filtration Rate↗
PubMed1991

Baseline sister chromatid exchange in human cell lines with different levels of poly(ADP-ribose) polymerase.

Poly(ADP-ribose) polymerase is a chromatin enzyme which adds long chains of ADP-ribose to various acceptor proteins in response to DNA strand breaks. Its primary function is unknown; however, a role in DNA repair and radiation resistance has been postulated based largely on experiments with enzyme inhibitors. Recent reports of mutant cell lines, deficient in poly(ADP-ribose) polymerase activity, have supported previous studies with inhibitors, which suggests the involvement of poly(ADP-ribose) polymerase in maintaining baseline levels of sister chromatid exchanges. Mutant cells with even slightly depressed enzyme levels show large elevation of baseline sister chromatid exchanges. Since intracellular poly(ADP-ribose) polymerase levels can vary greatly between different nonmutant cell lines, we surveyed levels of baseline sister chromatid exchange in normal and tumor human cell lines and compared them with endogenous levels of poly(ADP-ribose) polymerase. Despite 10-fold differences in poly(ADP-ribose) polymerase, the baseline level of sister chromatid exchanges remained relatively constant in the different cell lines (0.13 +/- 0.03 SCE/chromosome), with no indication of a protective effect for cells with high levels of the enzyme.

Humans↗
PubMed1990

Neuroimaging findings in Alexander's disease.

We present the findings from magnetic resonance imaging, computed tomographic scan, and single photon emission computed tomography of the brain in a 2-year-old girl with Alexander's disease. Computed tomographic scans showed prominent low-density white matter throughout the cerebral hemispheres. Magnetic resonance imaging showed increased T2 signal from the cerebral white matter but not the cerebellum or brain stem. Single photon emission computed tomography revealed diminished cerebral metabolism, particularly in the frontal regions, as compared with the cerebellum.

Astrocytes↗
PubMed1989

Absorption of Tc-99m pertechnetate from the augmented bladder during direct nuclear cystography.

A retrospective review comparing bladder absorption of pertechnetate and Tc-99m sulfur colloid from the augmented bladder was performed. Based upon the author's findings, the routine use of Tc-99m sulfur colloid in this patient population is recommended to prevent the erroneous diagnosis of vesicoureteral reflux and miscalculation of GFR due to the presence of background soft-tissue and blood activity.

Glomerular Filtration Rate↗
PubMed1979

Anorexia nervosa in males.

Five cases of anorexia nervosa in males aged 13--23 years are described. Four patients presented to a general medical outpatient clinic with emaciation, and the fifth was diagnosed retrospectively. Sinus bradycardia was a useful pointer to the diagnosis, which was confirmed by the finding of characteristic psychopathological features of a relentless "pursuit of thinness", along with a fear of becoming obese.

Adolescent↗
PubMed1979

Pulmonary cytomegalovirus infection: detection by Gallium 67 imaging in the transplant patient.

Cytomegalovirus (CMV) infeciton is a frequent complication during the first few months following renal transplantation. The diagnosis is sometimes difficult but may be made by viral culture, a fourfold rise in the CMV antibody titer, or by demonstration of the CMV inclusions in the affected tissue. An increased pulmonary uptake of galliulm citrate Ga 67 has been demonstrated following renal transplantation in two patients, each of whom had a fourfold rise in CMV complement fixing antibody titer, one of whom additionally had CMV inclusion bodies in a lung biopsy specimen prior to clinical or radiological demonstration of the pulmonary involvement. Gallium imaging, therefore, appears to be a valuable noninvasive test for early diagnosis of CMV pulmonary infections.

Adolescent↗
PubMed1979

Dissecting aortic aneurysms: a clinicopathological study. I. Clinical and gross pathological findings.

One hundred and seventy-one patients with dissecting aneurysm seen between 1951 and 1976 at three hospitals in Manchester were studied. There were 60 proximal dissections, 80 distal dissections, 10 abdominal dissections and in 21 the site of origin was uncertain. Pain was the major symptom in 88 per cent of patients; radiation of pain to the interscapular region was much more common in distal dissections. Systemic hypertension was present in 77 per cent, being commoner in distal dissections (83 per cent) than in proximal dissections (70 per cent). Aortic incompetence, hemiplegia and shock were all more common in proximal dissections. Post-mortem examination was performed in 125 patients. Eighty-four per cent of proximal dissections had ruptured, 74 per cent into the pericardium and five per cent into the left pleural cavity. Seventy per cent of distal dissections had ruptured, 11 per cent into the pericardium and 41 per cent into the left pleural cavity. The extent of the dissection was analysed, and it was shown that 25 per cent of distal dissections had extended proximally into the ascending aorta and arch. This implies that diagnosis of the site of origin of dissection from clinical signs and the plain chest-radiograph is inaccurate. Aortography is required for precise assessment. Since treatment often varies with the site of dissection, aortography should be performed in most patients surviving the first few hours. Attention is drawn to the frequency (10.4 per cent) of multiple aortic lesions, and to the occasional aetiological significance of giant-cell arteritis, and, possibly, hypothyroidism.

Adult↗
PubMed1979

Dissecting aortic aneurysms: a clinicopathological study. II. Histopathology of the aorta.

The aortas from 83 patients with dissecting aneurysm were studied histologically. There were two examples of giant-cell arteritis, one of non-specific arteritis and one of syphilis. Apart from these, no constant feature was found in the cases of dissection when compared with 20 controls. In particular there was no difference in the grades of cystic medial necrosis, medionecrosis and fibrosis. Focal fragmentation of elastica was present in the majority of dissections (63 per cent) but similar abnormalities were seen in most controls (85 per cent). The vasa vasorum showed no special features in dissection. Intimal fibrosis and intimal longitudinal muscle were present in both groups studied. Sixteen cases showed 'old' dissections as manifest by either granulation tissue or fibrosis. The histopathological features of the four cases diagnosed clinically as having Marfan's syndrome did not differ from controls.

Adult↗
PubMed1979

Renal cortical imaging and the detection of renal mass lesions.

Tc-99m gluceptate renal imaging was compared with the intravenous urogram in 41 patients. While the specificity of the examination was essentially the same for both techniques, the sensitivity for the detection of renal mass lesions was better with gluceptate imaging. The study suggests the desirability of a shift in emphasis from the IVU to the Tc-99m gluceptate scintigram in the early evaluation of suspected renal mass lesions, and merits further clinical evaluation.

Adolescent↗
PubMed1978

Ultrasound and nuclear medicine in evaluation of renal disease.

Multiple diagnostic imaging techniques are currently available to the clinician but the complementary nature of these techniques is frequently overlooked. A case is presented to illustrate the contributions of ultrasound, radiology, and nuclear medicine in evaluating renal disease.

Adult↗