The proteolytic substructure of light meromyosin. Localization of a region responsible for the low ionic strength insolubility of myosin

Light meromyosin (LMM), prepared by limited tryptic digestion of myosin, usually contains several polypeptide chains, LMM-A, LMM-B, and LMM-C in decreasing order of molecular weight estimated from sodium dodecyl sulfate-gel electrophoresis. Further limited tryptic digestion of LMM produces well defined fragments (Balint, M., Szilagyi, L., Fekete, Gy., Blazso, M., and Biro, E. N. A. J. Mol. Biol. (1968) 37, 317-330). Fragments LF-1, LMM-D, LF-2, and LF-3, with chain masses equal to 63, 56, 47, and 30 kDa, respectively, have been isolated by column chromatography. Based on the time course of the changes in the sodium dodecyl sulfate-gel pattern of the digests, chain masses estimated from sodium dodecyl sulfate-gel electrophoresis, and the NH2- and COOH-terminal sequences of the isolated peptides, the following scheme can be deduced. Formula; see text. C and N over the arrows indicate removal of residues from the COOH and NH2 terminus, respectively. The positions of the peptides along the myosin heavy chain have been established by comparison with the published primary structures of rabbit skeletal (Elzinga, M., Behar, K., Walton, G., and Trus, B. L. (1980) Fed. Proc. 33, 1579) and nematode myosin (McLachlan, A. D., and Karn, J. (1982) Nature (Lond.) 299, 226-231). LMM and fragment LMM-D are insoluble, whereas LF-1, LF-2, and LF-3 are soluble at low ionic strength. Their solubility properties, in conjunction with their locations along the myosin heavy chain, suggest that a relatively small stretch of peptide (chain weight, 5,000 Da) located about 100 residues from the COOH terminus of myosin heavy chain is responsible for the insolubility of LMM at low ionic strength.

Effect of adsorbed protein on hydroxyapatite zeta potential and Streptococcus mutans adherence

The adherence of Streptococcus mutans PK1 to hydroxyapatite disks pretreated with various acidic and basic proteins in imidazole buffer was studied. Adsorption of a basic protein onto an hydroxyapatite disk enhanced or had no effect on bacterial adherence, whereas adsorption of an acidic protein reduced adherence. The effect of adsorbed protein on bacterial adherence was of both short and long range. The long-range effect of the acidic proteins in reducing the number of bacteria adhering to hydroxyapatite was related to protein adsorption causing an increase in surface net negative charge, as shown by zeta potential measurement. Basic protein produced a net positive surface charge which facilitated adherence. Within the acidic protein group, the acidic residue percentage of the adsorbed protein was negatively correlated with the number of bacteria adhering, whereas the nonpolar residue percentage was positively correlated with bacterial adherence. Within the basic protein group, the basic residue percentage was correlated with the number of cells adhering. These results indicate the involvement of short-range hydrophobic and ionic interactions in bacterial adherence to protein-coated hydroxyapatite.

Involvement of prostaglandin synthetase in the peroxidative metabolism of diethylstilbestrol in Syrian hamster embryo fibroblast cell cultures

The mechanism for induction of tumors by estrogens is still unresolved. Neoplastic transformation of Syrian hamster embryo fibroblasts by diethylstilbestrol (DES) suggests that established principles of chemical carcinogenesis may be involved. The Syrian hamster embryo fibroblast cells provide a system in which now the question can be asked whether the metabolic activation of DES is a prerequisite for its biological activity in this system. In this study, Syrian hamster embryo fibroblast cell cultures were shown to oxidatively metabolize DES to cis,cisdienestrol (Z,Z-DIES) which is a DES metabolite commonly found in vivo. The only other metabolic conversion of DES detectable in these cell cultures was the formation of the glucuronides of DES and Z,Z-DIES. Z,Z-DIES is formed more efficiently in incubations with rapidly growing cells than in cultures approaching confluence. When arachidonic acid was added to the medium, Z,Z-DIES formation was enhanced, whereas indomethacin added to the cell cultures inhibited the formation of this metabolite. These data suggest the involvement of prostaglandin synthetase in the oxidative metabolism of DES by Syrian hamster embryo fibroblast cells in culture and suggest that cooxidation may play a role for its biotransformation in whole cells. Moreover, since many competing metabolic pathways are available to DES in vivo, this present study adds important additional support to the hypothesis that metabolism of DES via a peroxidative route plays a role in its carcinogenicity.

Morphologic and neoplastic transformation of Syrian hamster embryo fibroblasts by diethylstilbestrol and its analogs

A mammalian cell culture system using normal, diploid Syrian hamster embryo fibroblasts was used as a model to study the ability of diethylstilbestrol (DES) and related compounds to induce neoplastic transformation. Like benzo(a)pyrene, a known chemical carcinogen, DES (0.01 to 10 micrograms/ml) induces morphological transformation of Syrian hamster embryo fibroblasts in vitro; the transformed colonies were indistinguishable from colonies of benzo(a)pyrene-transformed cells. The morphologically transformed colonies derived from either benzo(a)pyrene- or DES-treated cells were tumorigenic when injected into newborn hamsters. At doses of 0.01 to 1 microgram/ml for 48 hr, DES did not inhibit or stimulate cell proliferation. Structural analogs of DES were also tested in the Syrian hamster embryo transformation system. Like DES, tetrafluorodiethylstilbestrol, dimethylstilbestrol, and cis,cis-dienestrol morphologically transformed Syrian hamster embryo cells. The transformation frequency of dimethylstilbestrol was much less than that of DES, tetrafluorodiethylstilbestrol, or cis,cis-dienestrol. Hexestrol, dimethoxydiethylstilbestrol, and trans,trans-dienestrol did not transform these cells. No correlation could be demonstrated between reported estrogenic potency of the compounds and their cell-transforming capacity. Structure-activity relationships developed for these chemicals suggest that metabolism via specific pathways plays a role in DES-induced cell transformation.

Diethylstilbestrol induces neoplastic transformation without measurable gene mutation at two loci

The frequency with which diethylstilbestrol induces neoplastic transformation and somatic mutation was measured concomitantly in Syrian hamster embryo cells. While diethylstilbestrol was as active as benzo[a]pyrene in inducing transformation, it failed to induce mutations at two conventionally studied loci. These results suggest that diethylstilbestrol may transform cells in the absence of gene mutations.

Hereditary generalized juvenile polyposis associated with pulmonary arteriovenous malformation

A 28-yr-old mother and her 10-year-old daughter with generalized juvenile gastrointestinal polypsis, arteriovenous (AV) malformations of the lung and severe digital clubbing are described. The AV malformations were documented by pulmonary angiography in both subjects, and generalized juvenile polyposis was confirmed histologically and radiographically. Since pulmonary AV malformations associated with juvenile polyposis has not been previously reported, a new hereditary syndrome is proposed.

The historical development of federal involvement in health care

In this historical summary of the federal role in health care, three time periods are described: 1) the late 1700's to 1940; 2) 1941 to 1964; and, 3) 1965 to the present. Significant legislation and federal programs are reviewed. The purpose of this overview is to provide health professionals with an historical perspective and to increase their knowledge of current and future events in the rapidly changing health care delivery system in the United States.

The metabolically mediated DNA damage and subsequent DNA repair by 4-chlorobiphenyl in Chinese hamster ovary cells

The metabolism of [3H]-4-chlorobiphenyl (CB) by Chinese hamster ovary cell cultures resulted in the formation of lipophilic hydroxylated metabolites, trichloroacetic acid soluble conjugates and covalent macromolecular adducts. The major lipophilic metabolite was chromatographically similar to 4'-chloro-4-biphenylol. The intracellular macromolecules were fractionated into protein, RNA and DNA. Although protein was the major target of covalent interaction with [3H]-CB and contributes 85% of the macromolecular binding, the specific binding of [3H]-CB to DNA was 3.5 and 1.4 times higher than that observed for protein and RNA respectively. Incubation of the CHO cells with 10 mM CB, [3H]-thymidine and 10 mM hydroxyurea for 2.5 hr resulted in a 1.6 fold increase in unscheduled DNA synthesis. The data demonstrated that the readily metabolized CB congener not only reacts with mammalian cell macromolecules, including DNA, but the DNA damage can also be demonstrated by its subsequent repair.

The association of obesity with infertility and related menstural abnormalities in women

Historical data from 26 638 20-to 40-year women were used to study the association between obesity and menstrual abnormalities including evidence of infertility. It was found that women with evidence of anovulatory cycles, ie, irregular cycles greater than 36 days, and hirsutism, were more than 30 lb (13.6 kg) heavier than women with no menstrual abnormalities after adjusting for height and age. The percentage of women with evidence of anovulatory cycles was 2.6 per cent for women less than 20 per cent overweight, 4.0 per cent for women 20-49 per cent overweight, 5.8 per cent for women 50-74 per cent overweight., and 8.4 per cent for women more than 74 per cent overweight Women with a single menstrual abnormality including cycles greater than 36 days, irregular cycles, virile hair growth with facial hair, or heavy flow were also significantly heavier than women with normal values for these factors. A longer duration of obesity was associated with facial hair. Another analysis found that teenage obesity was greater for never-pregnant married women than for previously pregnant married women and for women having ovarian surgery for polycystic ovaries than for women having ovarian surgery for other reasons. This also supports an association of obesity with anovulatory cycles. These findings showing evidence of abnormal ovulation, menstrual abnormalities and excess hair growth in obese women may be explained by the recent studies of others demonstrating an association between obesity and hormonal imbalances.

Variation in susceptibility of chick embryo tissues to infection with Rous sarcoma virus in vitro

Second-generation whole chick embryo cultures were compared with second-generation limb bud, somite, and kidney cultures of various ages in their ability to support Rous Sarcoma virus infection. Limb bud cells yielded the highest proportion of infected cells and kidney cells the lowest 48 hours after infection in vitro. Cultures prepared from 9-day embryos were more susceptible to infection than those from younger or older embryos. When tissues from 9-day embryos were used for the in vitro assay of three strains of Rous Sarcoma virus, limb bud cells yielded slightly higher focus counts in each case than whole embryo, approximately 0.5 log higher than somite and approximately 2.0 logs higher than kidney cells. Limb bud cultures also showed less tendency to clump and foci were more easily counted than in cultures from the other tissues.