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Biomedical subjects

M E Billingham

Publications and source records attributed to M E Billingham.

At least 127 records · Page 7Linked to original sources
PubMed1988

6-Hydroxydopamine mediated cardiotoxicity in rabbits.

Weekly injections of the catecholamine depleting agent 6-hydroxydopamine (6-OHDA) were used to denervate rabbit hearts chemically. Analyses of morphology and beta-adrenergic receptor density were made at 1, 2, and 4 weeks. Changes resulting from subacute and chronic inflammatory processes were evident by light microscopy after 1 week. At that time, electron microscopy revealed marked increases in collagen, large myocytic vacuolizations in myocytes, widened gap junctions, and myofibrillar degeneration and dropout. Receptor density was marginally increased at 2 weeks but was decreased (p less than .05) at 4 weeks (maximal [3H]dihydroalprenolol (DHA) binding in fmol/mg: 69.6 +/- 5.4 in controls vs 49.2 +/- 5.1 in 6-OHDA-treated animals). Basal, isoproterenol-stimulated and F- -stimulated adenylate cyclase activities were decreased in the 6-OHDA-treated group at 4 weeks. We conclude that administration of 6-OHDA may cause severe myocardial damage, and that this process may involve loss of some functional components of the cell membrane.

Adenylyl Cyclases↗
PubMed1988

A reappraisal of the structure of normal canine articular cartilage.

It has been shown that some of the controversy over the structure of articular cartilage may be due to slight differences in the orientation of the sample that has been studied. As our decisive criterion we have used the simple physical fact that elongate proteins, such as collagen micelles, that can exhibit form-birefringence, had to show virtually straight extinction when viewed under crossed polars. The use of a variably adjustable microtome chuck facilitated small adjustments in the orientation of the cartilage to meet this criterion. Under these conditions, the collagen of the matrix has been shown to be aligned mainly perpendicularly to the surface which was bounded by a thin lamina in which the collagen showed birefringence at 90 degrees to that of the matrix. The conventionally described zonation of articular cartilage has been shown to be inadequate for that of the dog tibial plateau. The conventional Zone 2 has been shown to consist of two zones, Zones 2a and 2b, with different cell sizes, cell concentrations, and concentration of matrix components.

Animals↗
PubMed1988

Cardiomyopathy in a rat model of pheochromocytoma. Morphological and functional alterations.

To investigate the cardiac muscle damage observed in pheochromocytoma, New England Deaconness Hospital rats were implanted subcutaneously with a transplantable pheochromocytoma. The tumor was evident 4 weeks after transplantation. Approximately 5-6 weeks after transplant, systolic blood pressure was significantly increased in tumor-bearing animals (183 +/- 13 vs 119 +/- 7 in controls). At this time a cardiomyopathy with the following features was apparent in the tumor-bearing animals: multifocal lesions of enhanced interstitial and replacement fibrosis; granularity of the cytoplasm and contraction band necrosis; and mixed inflammatory infiltrates. Using a morphological scoring system from 0 (no cardiac damage) to 3 (complete involvement of the ventricular cross section studied), the pheochromocytoma animals had a cardiomyopathy score of 1.8 +/- 0.1, which is significantly greater than that found in age- and sex-matched controls: 0.4 +/- 0.1, p less than .001. A significant increase in the wet heart weights (1.28 +/- 0.07 vs. 1.12 +/- 0.04 in controls) was also observed in these animals, indicating the possibility of cardiac hypertrophy in the pheochromocytoma rats. There was a marked decrease in sensitivity to isoproterenol in isolated, electrically driven left atrial strips from pheochromocytoma rats. Isoproterenol's EC50 increased eightfold from 1.5 +/- 0.6 x 10(-8) M in controls to 1.3 +/- 0.4 x 10(-7) M in left atrial strips from the pheochromocytoma rats. However, there was no difference in maximal contractile response to isoproterenol in either the left atrial strips or in right or left ventricular papillary muscle strips. Also, there was no change in responsiveness of either left atrial or right ventricular muscle strips from pheochromocytoma hearts to contraction induced by 3.75 mM calcium chloride. However, the contractile response to calcium was enhanced in left ventricular papillary muscle from tumor-bearing animals (808 +/- 195 vs 372 +/- 101 mg tension in controls, p less than 0.05). These results demonstrate a catecholamine-induced cardiomyopathy in hearts from pheochromocytoma-bearing rats. Furthermore, the results demonstrate a functional beta-adrenergic receptor desensitization in isolated left atrial strips from tumor-bearing rats, whereas maximal contraction of heart muscle, induced by either isoproterenol or calcium chloride, remains intact.

Animals↗
PubMed1988

Cardiac transplantation.

Cardiac transplantation offers an excellent chance of long-term survival and functional rehabilitation for the carefully selected patient with end-stage heart disease. The part played by the pathologist in the care of these patients is crucial. It is vital to make the diagnosis of acute rejection before it becomes irreversible and also before it causes chronic damage to the coronary arteries. It is also vital that the pathologist does not either miss the diagnosis of an infectious myocarditis in the immunosuppressed patient or misdiagnose myocarditis as rejection, because the treatments for each one of these conditions are diametrically opposed. The role of the pathologist has become one of an important clinical colleague in the management and survival of patients with cardiac allografts.

Follow-Up Studies↗
PubMed1988

The pathology and etiology of cocaine-induced heart disease.

During the last two years, reports have appeared linking cocaine use to virtually every type of heart disease. Ischemic events have been reported regularly, and there appears to be a strong relationship between cocaine use, contraction bands, and sudden arrhythmic death. The evidence concerning cocaine-induced myocarditis, cardiomyopathy, and valvular heart disease is less clear. In this article, we review the currently known morphological changes induced by cocaine and discuss the possible mechanisms of action leading to these changes.

Adult↗
PubMed1987

Cocaine and the heart.

There is increasing evidence that cocaine can have serious adverse effects on the heart. Angina, myocardial infarction, coronary artery spasm, arrhythmia, and sudden death have been reported in association with its use. There have been only two reports of actual myocardial pathology. In an attempt to clarify the pathophysiology of cocaine-associated cardiotoxicity and to search for pathologic changes that might be useful forensically, we reviewed random microscopic sections of hearts from 30 cases of cocaine-associated death seen by the San Francisco Medical Examiner. The age of the patients at death ranged from 25 to 74 years (mean 33.9 years). Pathologic findings included the presence of mild atherosclerotic coronary artery disease without evidence of thrombosis in three cases, associated with mild interstitial fibrosis in one case as well as mild focal myocardial fibrosis without coronary disease in four other cases. The most notable abnormality was the presence of myocardial contraction bands in 28 (93 per cent) cases. In comparison to 20 control cases of death secondary to sedative-hypnotic overdose, the hearts from the cases of cocaine-associated contained significantly more myocardial contraction bands (P less than .001; two-sided). The diffuseness of the contraction bands correlated directly with the level of cocaine found in the urine and blood at autopsy during routine screening. The presence and number of contraction bands in these cases was independent of other drugs found in the urine and blood, the number of sections of myocardium examined, and a history of attempted resuscitation. Contraction bands may act to supply the anatomic substrate for the arrhythmias associated with cocaine use. They may also provide a morphologic marker that can be sought in suspected cases of lethal cocaine overdose. Their presence may also suggest a cause of death in cases of sudden and unexpected death in which autopsy reveals no other pathology, and a drug screen is positive for cocaine.

Cocaine↗
PubMed1987

An assessment of Nva2-cyclosporine in primate cardiac transplantation.

The immunosuppressive potency, hepatotoxicity, and nephrotoxicity of Norvaline2-cyclosporine (Nva2-CsA), an analog of cyclosporine (CsA), were tested in a primate cardiac transplant model. After orthotopic cardiac transplantation in cynomolgus monkeys, immunosuppression was maintained with 16 mg/kg/day of either CsA or Nva2-CsA given intramuscularly in two divided daily doses. Immunosuppression was augmented with i.m. methyl-prednisolone, 1.0 mg/kg/day, which was tapered weekly by .1 mg/kg/day to a maintenance dose of .1 mg/kg/day. A group of 6 untransplanted monkeys were treated for a year with this dose of either CsA or Nva2-CsA and steroids. Renal biopsies were performed at one year. Among the transplanted monkeys, mean survival was 77.3 +/- 73 days for the CsA group and 16 +/- 8 days for the Nva2-CsA group. All 11 animals in the Nva2-CsA group died of cardiac rejection, but only 7 of 10 treated with CsA died of rejection. There was mild hepatic and renal dysfunction in both treatment groups, but no significant difference between groups as judged by blood urea nitrogen, creatinine, total bilirubin, serum glutamic oxaloacetic transaminate, and alkaline phosphatase. Cyclosporine levels were significantly higher in the CsA group. There were important morphological changes in both groups on histological examination of the kidneys, with proximal tubular vacuolation and enlargement of the juxtaglomerular apparatus predominating. It is concluded that Nva2-CsA is a less effective immunosuppressant than CsA when given parenterally in equal doses.

Animals↗
PubMed1987

Combined heart-lung transplantation in the rat. Comparison of thoracic and abdominal operation techniques.

Recently, we developed two techniques for the combined transplantation of heart and the left lung into the left hemithorax of rats. One technique, with two vessel anastomoses, comprised the microsurgical repair of aorta, anterior vena cava, and left main bronchus. With the other, single vessel technique, only the aorta and bronchus were anastomosed. In this study, we determined the function and histology of syngeneic and cyclosporine (CsA)-treated allogeneic grafts transplanted with both techniques, and compared the results with those of heterotopic heart-lung grafts transplanted with a previously described technique for transplantation into the rat's abdomen. The survival rate of rats operated with either of the thoracic transplantation techniques was high (83%). Lungs and hearts of the grafts functioned well for over two months and had normal morphology when the double vessel technique was used. With the single vessel technique, the function of the lungs started to deteriorate from the third postoperative week onward, probably secondary to congestion. The results of thoracic grafts were superior to those of abdominal transplants, where the nonventilated lungs--especially during immunosuppression--were frequently infected. We conclude that these new techniques for thoracic transplantation are most suitable for research of combined heart-lung transplantation.

Abdomen↗
PubMed1987

Interobserver variability in the pathologic interpretation of endomyocardial biopsy results.

Controversy exists over the role of endomyocardial biopsy in evaluating patients with dilated cardiomyopathy, particularly in detecting myocarditis and in assessing prognosis. Interobserver variability, if high, could explain conflicting reports. To assess this possibility, we submitted biopsy specimens from 16 patients with dilated cardiomyopathy to seven cardiac pathologists. The same slides were independently reviewed by each and assessed for fibrosis, hypertrophy, nuclear changes on a 0 to 3+ scale, mean lymphocyte count per high-power field, and myocarditis. The prevalance of significant fibrosis ranged from 25% to 69%, hypertrophy from 19% to 88%, nuclear changes from 31% to 94%, and abnormal lymphocyte count from 0 to 38%. One or more pathologists diagnosed definite or possible myocarditis in 11 of the 16 patients. Of these 11 patients, three pathologists agreed about three and two pathologists agreed about five. Myocarditis was diagnosed by a single pathologist in three cases. We conclude that interobserver variability is high in interpreting biopsy specimens from patients with dilated cardiomyopathy and that quantitative and standardized methods are needed to increase diagnostic consistency.

Adult↗
PubMed1987

Effects of adrenergic receptor antagonists on cardiac morphological and functional alterations in rats harboring pheochromocytoma.

New England Deaconness Hospital rats harboring a transplantable pheochromocytoma exhibit plasma norepinephrine concentrations 20-fold higher than controls. A cardiomyopathy (CM) characterized by multifocal areas of interstitial and replacement fibrosis, mixed inflammatory infiltrates and contraction band necrosis is evident 35 to 45 days after tumor implantation. Using a morphological scoring system of 0 (no cardiac damage) to 3 (involvement of almost the complete ventricular cross-section sampled), a CM score of 1.8 +/- 0.1 was found in rats harboring pheochromocytoma, a significant increase over that in age- and sex-matched controls (0.4 +/- 0.1, P less than .001). The pheochromocytoma rats also had hypertension (systolic blood pressure = 182 +/- 4 vs. 131 +/- 2 mm Hg in controls, P less than .001). In an effort to prevent the CM, rats harboring pheochromocytoma were treated with either the beta receptor antagonist timolol, the alpha receptor antagonists phentolamine or phenoxybenzamine or the nonspecific vasodilator hydralazine. Hydralazine normalized systolic blood pressure (135 +/- 6 mm Hg), whereas timolol (144 +/- 5 mm Hg), phenoxybenzamine (166 +/- 5 mm Hg) or phentolamine (154 +/- 10 mm Hg) only moderately decreased blood pressure in rats harboring pheochromocytoma. Hydralazine had no effect on CM score (1.8 +/- 0.1). Timolol markedly attenuated the CM score (0.6 +/- 0.1), whereas the alpha adrenergic antagonists were not as effective (phenoxybenzamine CM score = 1.3 +/- 0.2; phentolamine CM score = 1.7 +/- 0.2). Furthermore, timolol prevented desensitization of beta adrenergic receptor-mediated contraction in the hearts of rats harboring pheochromocytoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Gland Neoplasms↗
PubMed1987

Myocyte hypertrophy in the transplanted heart. A morphometric analysis.

In order to better define long-term changes in the transplanted heart with respect to the effects of cyclosporine and the ischemic time of the donor heart, endomyocardial biopsies were examined ultrastructurally from 20 cardiac transplant recipients three years posttransplantation. The biopsies were divided into four groups of five based on the donor heart ischemic time in "on-site" versus "distantly procured" hearts and on the immunosuppression protocol: group A: "on site" donor hearts and cyclosporine-based immunosuppression; group B: "on site" donor hearts with conventional immunosuppression (azathioprine-based immunosuppression without cyclosporine); group C: distantly procured donor hearts treated with cyclosporine; and group D: distantly procured donor hearts treated with conventional immunosuppression. All four groups showed a significant increase in the average width of myocytes when compared with normal myocardium, (group A, P less than 0.05; groups B, C, D, P less than 0.01). Also, there was a significant difference between the average widths of myocytes from on-site donor hearts and distantly procured donor hearts (P less than 0.04). There was no significant difference between the average myocyte widths of groups treated with cyclosporine and those with conventional immunosuppression. This study shows that despite the hypertension induced by cyclosporine, myocyte hypertrophy at 3 years posttransplantation does not appear to be significantly greater than in patients treated with conventional immunosuppression. Distantly procured donor hearts have more hypertrophy. Due to the increasing evidence that cardiac hypertrophy per se may predispose to serious ventricular arrhythmias, this study supports the use of on-site as opposed to distantly procured donor hearts.

Cardiomegaly↗
PubMed1987

Rejection of combined heart-lung transplants in rats. Function and pathology.

Clinical experience with combined heart-lung transplantation has made it clear that several aspects of the rejection of combined organ transplants need further investigation. In this study, the rejection process of combined heart-lung allografts was examined for determining whether it affects the lung and heart synchronously and whether it differs from rejection when these organs are transplanted alone. The lungs of the combined allografts were functionally rejected prior to the heart (6 and 11 days, respectively). Accordingly, the pathologic changes were most severe in the lungs. The rejection pathology of these combinedly transplanted organs was similar to that described for lungs and hearts transplanted separately, except that the airways were found to be more extensively involved than had been appreciated in previous studies. It is concluded that after combined transplantation the lung is more prone to rejection than the heart. On the basis of the present observations, the definition of sequential rejection phases in the lung was slightly altered.

Animals↗