We report an unusual case of "arrhythmic" sudden cardiac death in a 3-year-old child who died of ischemic myocardial lesions as a result of intimal fibroplasia of the coronary arteries. Also affected were the aorta and its major branches, whereas renal and mesenteric arteries, celiac trunk, and systemic veins were normal. Histopathologic examination showed severe concentric thickening of intima because of a proliferation of spindle-shaped cells (mesenchymal cells) set in an abundant extracellular matrix. In some vascular segments the intima was densely fibrotic and hyalinized. No significant inflammation, foam cells, cholesterol clefts, or other evidence of atheroma were present. The intimal lesions did not involve the media and/or the adventitia. Immunohistochemical staining of intima showed the proliferating mesenchimal cells to be myofibroblastic. Reactions for vimentin and smooth muscle actin were positive, while those for desmin, myosin, CD34, and Factor VIII were negative.

Actins↗

PubMedDate not supplied

Effects of environmental antiandrogens on reproductive development in experimental animals.

Chemicals that act as androgen receptor (AR) agonists and antagonists or inhibit fetal steroidogenesis can induce reproductive malformations in humans and laboratory animals. Several environmental chemicals disrupt development in rats and/or rabbits at fetal concentrations at, or near, exposure levels seen in some segments of the human population. In rats, fetal tissues concentrations of 10-20 p.p.m. of the DDT metabolite, p,p'-DDE, are correlated with reproductive abnormalities in male offspring. These concentrations are similar to those measured in first-trimester human fetal tissues in the late 1960s. The pesticides vinclozolin, procymidone, linuron and DDT are AR antagonists. They reduce male rat anogenital distance, and induce areolas at relatively low dosages. Hypospadias, agenesis of the sex accessory tissues and retained nipples are seen in the middle dosages, while undescended testes and epididymal agenesis are seen in the highest doses. Phthalate esters (PE) inhibit testosterone synthesis during fetal life, but do not appear to be AR antagonists. Prenatal administration of a single low dose of dioxin (50-1,000 ng TCDD/kg) alters the differentiation of androgen-dependent tissues at p.p.t. concentrations, but the mechanism of action likely involves interaction with a hormone-like nuclear transcription factor, the hormone-like receptor AhR, rather than AR. p,p'-DDT and p,p'-DDE, vinclozolin and di-n-butyl phthalate affect reproductive function in rabbits when administered during prenatal and/or neonatal life. Cryptorchidism and carcinoma in situ-like (CIS) testicular lesions were seen in male rabbits treated during development with p,p'-DDT or p,p'-DDE. Extrapolation of effects from rodents to humans would be enhanced if future studies incorporate determination of tissue concentrations of the active metabolites. Knowledge of the tissue concentrations of the active toxicants also would provide an important link to in-vitro studies, which provide more useful mechanistic information when they are executed at relevant concentrations.

Androgen Antagonists↗

PubMedDate not supplied

Platelet adhesion to vascular cells. The role of exogenous von Willebrand factor in platelet adhesion.

Platelet deposition on cultured fibroblasts and on their extracellular matrix (FBM) was investigated in a flow system with citrated blood and was compared with platelet deposition on cultured endothelial cells, smooth muscle cells, and their extracellular matrices. Platelet deposition was present at all surfaces except on intact endothelial cells. Deposition on FBM consisted of contact platelets, spread platelets, and a few small aggregates. On intact fibroblasts cells, the surface coverage was lower, and platelets formed aggregates. Factors involved in primary hemostasis, particularly the wall shear rate, von Willebrand factor (vWF), and fibronectin, were investigated on FBM. The reactivity of FBM was determined by the passage number of the cultured cells. The vWF was involved in platelet adhesion on FBM at only the high shear rate (greater than 800 s-1). Platelet deposition was independent of plasma fibronectin at all shear rates tested. Matrix-associated fibronectin was involved in adhesion at low and high wall shear rates. We conclude that FBM can be used as a platelet adhesive surface especially to study the contribution of exogenous vWF to platelet adhesion because FBM does not contain vWF.

Blood Platelets↗

PubMedDate not supplied