Ultrastructure of the full-term shark yolk sac placenta. II. The smooth, proximal segment

The smooth, proximal portion of the yolk sac placenta of the sandbar shark, Carcharhinus plumbeus is comprised of: (1) An outermost epithelial ectoderm; (2) an intervening collagenous stroma; and (3) an inner mesothelium. The surface epithelium may be one to three cell layers thick. The surface epithelium comprises two cell types. A cuboidal cell that has a dome-like apical surface covered with microvilli and an ovoid nucleus predominate. These cells contain lipid inclusions, many cytoplasmic filaments, and are joined by desmosomes. The second cell type has a convoluted nucleus and a flattened cell apex with microvilli, cilia, and paddle cilia. Golgi complexes and elements of the endoplasmic reticulum are relatively uncommon in the cytoplasm of both cell types. Microplicae also occur on the surface of some cells. The smooth, proximal portion of the placenta is sparsely vascularized. The innermost cellular elements of the surface epithelium rest on a prominent basal lamina. A collagenous zone separates the epithelial basal lamina from the basal lamina of the mesothelium. The mesothelial cells are squamous with a fusiform nucleus, many pinocytotic pits and vesicles, and a large number of cytoplasmic filaments. The endoplasmic reticulum, except for occasional patches of the rough type, and the Golgi complex are poorly developed. Ultrastructural tracer studies show that this portion of the placenta does not absorb horseradish peroxidase (HRP) and trypan blue.     

Ineffective erythropoiesis in acute human P. falciparum malaria

An analysis of erythroblast cell kinetics utilizing quantitative 14C-autoradiography has been performed in five cases of acute Plasmodium falciparum malaria prior to and, in four patients, 3 or 6 days after the onset of antimalarial therapy. Associated with no or only moderate anemia were changes of erythroblast morphology, a considerable shift in the frequency of red and white blood cell precursors in the bone marrow, and a reduced rate of erythroblast proliferation. There was a marked loss of polychromatic erythroblasts, which was smaller but still detectable during the therapeutic phase. The results provide some quantitative data on the extent of "parenchymal damage" of bone marrow and stress the impact of ineffective erythropoiesis and reduced rate of erythropoietic proliferation on the emergence of anemia in Plasmodium falciparum malaria.     

Induction of 7-ethoxycoumarin o-deethylase activity in cultured human epithelial cells by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD): evidence for TCDD receptor

The responsiveness of 5 human squamous cell carcinoma (SCC) lines derived from tumors of the epidermis and tongue to 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) was assessed by measuring the induction of the cytochrome P1-450-mediated monooxygenase activity, 7-ethoxycoumarin O-deethylase (ECOD). In 4 of the SCC lines the EC50 for this response was approximately 10(-9)M, whereas in one line the EC50 was 10(-10)M. In each of the less sensitive lines a concentration of 10(-10)M TCDD elicited less than 5% of the maximal enzyme activity. Specific binding of radiolabeled TCDD was detected in the cytosol fraction from all the SCC lines. The relative amount of receptor measured in each line correlated with maximally-induced ECOD activity. The data indicate that human cell lines derived from a target tissue for TCDD toxicity contain the TCDD receptor and show differential sensitivity to TCDD analogous to the murine strain differences in sensitivity regulated by the Ah locus.     

Properties of a neutral allele model with intragenic recombination

An infinite-site neutral allele model with crossing-over possible at any of an infinite number of sites is studied. A formula for the variance of the number of segregating sites in a sample of gametes is obtained. An approximate expression for the expected homozygosity is also derived. Simulation results are presented to indicate the accuracy of the approximations. The results concerning the number of segregating sites and the expected homozygosity indicate that a two-locus model and the infinite-site model behave similarly for 4Nu less than or equal to 2 and r less than or equal to 5u, where N is the population size, u is the neutral mutation rate, and r is the recombination rate. Simulations of a two-locus model and a four-locus model were also carried out to determine the effect of intragenic recombination on the homozygosity test of Watterson (Genetics 85, 789-814; 88, 405-417) and on the number of unique alleles in a sample. The results indicate that for 4Nu less than or equal to 2 and r less than or equal to 10u, the effect of recombination is quite small.     

Comparative Evaluation of Rheumatic Activity—A Study of Relationship Between Histologic Changes and Serologic Test Results in Cardiac Surgical Patients

Atrial or ventricular myocardium from patients with surgically corrected rheumatic valvular disease was studied for rheumatic lesions in 86 cases. Histologically active Aschoff bodies were found in 20 per cent of the cases. A slight, but statistically not significant relationship was demonstrated in comparison of elevated serologic tests for rheumatic activity with the presence of Aschoff bodies.