Fabricating fixed partial dentures using existing restorations

A technique has been described for utilizing an existing fixed splint in the fabrication of a fixed partial denture to replace splinted teeth that are extracted.     

The morphogenesis of testicular degeneration induced in rats by orally administered 2,5-hexanedione

The neurotoxic hexacarbon 2,5-hexanedione (2,5-HD) produces testicular atrophy in experimental animals. To examine the morphogenesis of the testicular lesion, 1.0% 2,5-HD was provided in the drinking water of adult F-344 rats for up to 6 weeks. After 3 weeks of administration, there were occasional large vacuoles in the basal region of the germinal epithelium. At 4 weeks, these vacuoles were much larger and more numerous; electron microscopy demonstrated that they were derived from the smooth endoplasmic reticulum. The vacuoles were preferentially associated with stages 12, 13, 14, and 1 of the spermatogenic cycle. Additionally, at 4 weeks there was a significant decrease in the number of tubules in stages 7 and 13, and a concomitant increase in the percentage of tubules in stages 3, 5, and 6. By Week 5, most Golgi-phase and cap-phase spermatids were visibly affected, showing margination of nuclear chromatin, and were becoming dissociated from Sertoli cells. Frequent multinucleated giant cells were seen and electron microscopy of these cells suggested that they were derived from fused spermatocytes or spermatids. After 6 weeks, fewer giant cells were present, most tubules contained cellular debris, and many showed empty lumina encircled by a thin ring of cytoplasm near the basement membrane. Interstitial tissue appeared unaffected. These studies indicate that the Sertoli cell is probably an initial target for 2,5-HD action in the testis.     

A portable device for the rapid concentration of viruses from large volumes of natural freshwater

A portable device for the rapid concentration of viruses from natural freshwaters described and its performance in field use is evaluated. The system handled up to 500 litres of water in less than 90 min at a cost of only 2 pounds per sample. Where the samples contained sufficient bacteriophages for detection by direct plating the apparent phage recoveries were greater than 75%. Plant and animal viruses were also concentrated from waters with this system.     

Serum IgG, IgA, IgM, and IgE levels and allergy in Filipino children in the United States

The serum levels of IgE, IgG, IgA, and IgM of 27 American-born Filipino children 5 to 17 years of age were measured and found to be significantly higher than those of a control group of 24 Caucasian children of similar age distribution and attending the same general pediatric clinics. The geometric mean of serum IgE of the Filipinos was 227 U. per milliliter and of the Caucasians, 69 U. per milliliter (p < 0.01). The geometric means of other serum immunoglobulin levels of the Filipinos by comparison with the Caucasians were: IgG, 1,303 and 1,010 mg. per 100 ml. (p < 0.01); IgA, 195 and 120 mg. per 100 ml. (p < 0.001); and IgM, 141 and 92 mg. per 100 ml. (p < 0.02), respectively. The incidence of atopic disease was higher in the Filipino study group (48 per cent) than in the Caucasian control group (25 per cent); eczema was especially prevalent in the Filipino group. Elevated serum IgE levels were associated with atopic disease in both racial groups; however, there was no correlation between serum level of IgG, IgA, or IgM and atopy.     

Double nondisjunction during karyotypic progression of chemically induced Syrian hamster cell lines

The karyotypic evolution of three chemically induced cell lines of Syrian hamster embryo in culture are described. The only karyotypic alteration of one clone was a trisomy of chromosome #11, which presumably arose by nondisjunction after carcinogen treatment. A pure population of cells with the trisomy was observed repeatedly upon karyotyping of cells at the first three passages after cloning. However, at a late passage, apparently normal diploid cells appeared in the culture, which we propose resulted from a second nondisjunction of one chromosome #11, reverting the cells from trisomy 11 to disomy 11. The karyotypic evolution of two other cell lines also involved double nondisjunction, which resulted in duplication of a translocated chromosome and concurrent loss of the normal nonrearranged chromosome. Taken together with the reported findings of others, the results indicate that double nondisjunction is a mechanism in karyotypic progression during neoplastic development.     

Does hyperimmunoglobulinemia-E protect tropical populations from allergic disease?

The Waorani Indians of eastern Ecuador have the highest blood concentration of IgE reported in a human population. Evidence obtained by medical history, physical examination, and immediate hypersensitivity skin tests suggests that pollen allergy and other atopic diseases are rare among the Waorani. A similar association between parasite-induced hyperimmunoglobulinemia-E and a low prevalence of conventional atopic disease has been reported in numerous other tropical populations. Saturation of mast cell IgE receptors with antibodies directed to the parasite and/or other antigens and competitive inhibition of passive binding of pollen allergen-specific IgE is one hypothetical cause of this association. We have tested this interesting conjecture by passively sensitizing the skin of Waorani Indians with serum containing pollen allergen-specific IgE antibodies. Waorani Indians with hyperimmunoglobulinemia-E can be adoptively sensitized with human ragweed or rye grass hyperimmune IgE antisera. This suggests that the cutaneous mast cells of healthy Waorani have active IgE receptors. The high circulating plasma concentrations of IgE in the Waorani do not prevent adoptive cutaneous sensitization with pollen-specific IgE antibodies.     

Bulimia in male patients

Bulimia is not exclusively a disorder of women. Twelve men with bulimia were evaluated and found to have demographic variables and eating behaviors similar to those of female bulimia patients. Eleven of the 12 men were binge eating more than once a day, and ten of the 12 also self-induced vomiting on a regular basis. Three patients had initiated bulimic behavior in association with athletic training. Eight patients followed through with treatment referrals and responded favorably to therapy.     

Ultrastructural studies on the localization of IgG in the aortic endothelium and subendothelial intima of atherosclerotic and nonatherosclerotic rabbits

Immunoelectron microscopy with peroxidase-conjugated Fab fragments of anti-IgG was used for studying the localization of IgG in the aortic endothelium and subendothelial intima of atherosclerotic and nonatherosclerotic rabbits. Small amounts of IgG were found in the cell coat, in caveolae and vesicles, and also in intercellular clefts of endothelial cells from normocholesterolemic rabbits. Injured endothelial cells exhibited prominent accumulations of IgG in the cytoplasmic matrix, possibly due to leakage through plasma membrane defects. In atherosclerotic lesions from hypercholesterolemic rabbits, there was a striking increase in the amount of IgG-reactive material in the cell coat and vesicles of intact endothelial cells. Also in these animals, injured endothelial cells were characterized by a cytoplasmic IgG accumulation. There were prominent IgG depositions in the subendothelial zone of the lesions. IgG was adhering to collagen fibers, and also coating the surfaces of subendothelial foam cells. The pathophysiological significance of an interaction between such intimal IgG and phagocytes is discussed.