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Biomedical subjects

C Cohen

Publications and source records attributed to C Cohen.

At least 271 records · Page 15Linked to original sources
PubMed1988

Immunohistochemical basic and acidic isoferritins in hepatocellular carcinoma.

Normal liver ferritin is composed of basic isoferritins with a greater proportion of liver (L) type. Hepatocellular carcinoma (HCC) contains, in addition, acidic isoferritin with H heart myocardium (H) type similar to that in normal adult heart myocardium, early gestation fetal liver, early placenta, HeLa cells, and tumors. Using antisera to liver and myocardial ferritin, immunohistochemical basic and acidic isoferritins, respectively, were studied in 36 HCCs. There was no significant difference in the frequencies of liver ferritin in 17 (47%) tumors and of myocardial ferritin in 22 (61%) (P = 0.3). Ten (28%) tumors showed neither basic nor acidic isoferritin, and nine (25%) had acidic but not basic isoferritin. Raised serum ferritin levels in HCC patients probably, in part, reflect ferritin secretion by the tumor. The actual serum level would then consist of a mixture of basic and acidic (possibly tumor-specific) isoferritins. Thus, diagnostic use of a serum assay which utilizes antiserum to liver ferritin will demonstrate only basic isoferritins and probably will not detect raised serum levels in approximately half of HCC patients.

Carcinoma, Hepatocellular↗
PubMed1987

Tumor-associated antigens in breast carcinomas. Prognostic significance.

In an attempt to identify biologic markers that might predict prognosis in breast cancer patients, the presence or absence of seven tumor-associated antigens in 54 infiltrating breast carcinomas was correlated with tumor recurrence rates (minimum five-year follow-up), axillary lymph node metastases and tumor volume. Immunohistochemical kappa-casein was present in 30 (56%) tumors, alpha-lactalbumin in 39 (72%) tumors, secretory component of IgA in 26 (48%) tumors, carcinoembryonic antigen in 34 (63%) tumors, pregnancy-specific beta-1-glycoprotein in 7 (13%) tumors, beta subunit of human chorionic gonadotrophin in 1 (2%) tumor and human placental lactogen in 0 (0%) tumors. There was no significant correlation between the presence or absence in tumor of any of the antigens, and prognosis as assessed either by 5-year recurrence rates (P greater than 0.18) or by the presence of axillary lymph node metastases (P greater than 0.20). No significant difference was noted in mean tumor volume (cm3) +/- SEM, between tumors with or without antigen immunoreactivity (P greater than 0.05).

Antigens, Neoplasm↗
PubMed1987

Myosin binding to actin. Structural analysis using myosin fragments.

The actin-binding property of the myosin head 20 K (K = 10(3) Mr) fragment has been examined by a structural assay. A new fragment is produced by digestion of scallop myosin synthetic filaments with a lysine-specific protease. This fragment consists of the rod together with two "nubs" corresponding to the 20 K fragment, which retain both the regulatory and essential light chains. Myosin filaments, digested for different lengths of time, were mixed with F-actin and visualized by electron microscopy after negative staining. When the head is cleaved, but the head fragments remain associated, the filaments bind actin in an ATP-sensitive manner. Filaments made primarily of the nub-containing fragments, however, bind actin very poorly. In addition, electron microscopic characterization of actin-binding by the isolated tryptic 20 K fragment from chicken myosin indicates that binding of this fragment to actin is probably non-specific. These results suggest that interactions between the 20 K region and the other peptides in the head are essential for actin-binding.

Actins↗
PubMed1987

Structure of microtubules with reduced hydration. Comparison of results from X-ray diffraction and electron microscopy.

A recent model for the structure of microtubules is used to interpret X-ray fiber diffraction patterns from microtubules, obtained under various conditions. The results suggest that tubulin may undergo conformational changes under conditions of reduced water-activity. Such changes could account for some of the differences in the structure of tubulin as determined by electron microscopy and X-ray diffraction.

Microscopy, Electron↗
PubMed1987

A new crystal form of tropomyosin. Preliminary X-ray diffraction analysis.

A new crystalline form of tropomyosin has been produced that diffracts to about 4 A resolution. The crystals are grown at room temperature by slowly lowering the concentration of spermine. This polyamine apparently neutralizes the acidic amino acid side-chains of tropomyosin and allows close side-by-side packing of molecules. The space group is C2, with unit cell dimensions a = 259.7 A, b = 55.3 A, c = 135.6 A, and beta = 97.2 degrees. The tropomyosin molecules appear to be bonded head-to-tail to form straight filaments that run along the crystallographic (332) direction in an arrangement closely related to thin crystalline sheets previously described.

Crystallization↗
PubMed1987

Microtubule structure at 18 A resolution.

A model for the structure of microtubules at a resolution of 18 A (1 A = 0.1 nm) is described, based on X-ray fiber diffraction data from hydrated reassembled calf brain microtubules. The model was derived by an iterative solvent flattening refinement procedure, with initial phases based on those determined by electron microscopy. The major microtubule surface grooves are those defining the protofilaments, which form a hollow cylinder of maximum diameter 300 A. Strong electron density fluctuations in the microtubule wall are interpreted as evidence for a domain structure within the tubulin subunit. The arrangement of domains is such that the tubulin molecule could be quite flexible at the domain connections; thus, slight changes in this arrangement could account for the unusual polymorphism of tubulin assemblies.

Animals↗
PubMed1987

Myosin rod phosphorylation and the catch state of molluscan muscles.

"Catch" is a prolonged state of tension in molluscan smooth muscles shown by mechanical measurements to be associated with the level of protein phosphorylation. Myosin isolated from these muscles is unusual in being phosphorylated in the rod portion by an endogenous kinase, like certain nonmuscle myosins. These findings suggest that the myosin rod is a target for phosphorylation and that this reaction may control the transition from catch to relaxation.

Adenosine Triphosphate↗
PubMed1987

Ethical and legal considerations in the care of the infant with end-stage renal disease whose parents elect conservative therapy. An American perspective.

When parents elect conservative treatment for infants with end-stage renal disease (ESRD), their choice is medically, ethically, and legally acceptable, since dialysis and transplantation for young infants are still in the range of innovative and experimental treatments. Pediatric nephrologists have been reluctant to view these treatments as standard for very young infants because of doubts about their efficacy, technical difficulties in providing them for tiny patients, uncertainty about their short-term and long-term risks, and the suffering that they can create. Because these renal replacement therapies are not yet established, it is the responsibility of parents to determine whether the benefits of treatment outweigh its burdens for their infants. Physicians have an obligation to ensure that parents make a well-considered decision, and to provide them with counsel and support.

Ethics Committees, Clinical↗
PubMed1987

Amino acid sequence and structural repeats in schistosome paramyosin match those of myosin.

The cDNA encoding about half of an antigenic non-surface schistosome parasite protein of Mr 97 K has recently been cloned and sequenced (Lanar, Pearce, James and Sher (1986) Science 234:593-596). Analysis of this sequence, together with the properties of the native protein, reveals that this protein is paramyosin, the hitherto unsequenced core protein of myosin filaments in invertebrate muscle. In this report we analyze in more detail the partial amino acid sequence of schistosome paramyosin and describe electron microscope studies of the native protein and its aggregates. We show a close correspondence between the structures of paramyosin and the myosin rod that is required for these proteins to assemble together in muscle thick filaments.

Amino Acid Sequence↗
PubMed1987

Serum copper level in gynecologic malignancies.

Serum copper level was determined before operation in 179 patients with various histologically proved gynecologic tumors: malignant, benign, or metastases to the ovary. Serum copper level was significantly higher (p less than 0.01) in all groups of patients with cancer and in the benign group when compared with control subjects. Serum copper level correlated well with stage of cancer disease (r = 0.70 to 0.79) except for ovarian carcinoma, in which serum copper level was already significantly elevated in Stages I and II. The sensitivity of serum copper level greater than 150 micrograms/dl in detecting malignancy was 87% to 100% in late cancer stages in all malignancies. Our data imply that the addition of serum copper level determination to other screening tests could increase their sensitivity.

Copper↗
PubMed1987

Rod phosphorylation favors folding in a catch muscle myosin.

Myosin from a molluscan catch muscle is unusual in being phosphorylated in the rod by an endogenous heavy chain kinase. The overall structure of the molecule resembles that of other muscle myosins, although the tail is somewhat longer (approximately equal to 1700 A). At low ionic strength the unphosphorylated molecules associate in filaments that display a striking axial repeat of 145 A. Phosphorylation of the rod enhances myosin solubility in the range of NaCl between 0.05 and 0.15 M. Depending on the ionic strength and the counterions present, the soluble species corresponds to an antiparallel folded dimer (15 S) or to a folded monomer (10 S). Unphosphorylated myosin can also be partially solubilized into folded monomers by addition of ATP in 0.15 M NaCl. A similar molecular folding has also been observed in smooth muscle and nonmuscle myosins that depends, however, on the state of phosphorylation of the light chains in the myosin head. We discuss these results in relation to possible mechanisms for control of catch contraction.

Animals↗
PubMed1987

Combined chemotherapy and radiation therapy for advanced carcinoma of the cervix.

Ten patients with advanced squamous cell carcinoma of the uterine cervix received induction chemotherapy with cis-platinum, mitomycin-C, vincristine, and bleomycin (BOMP) over a 5 week period, followed by radiotherapy with concomitant weekly cisplatinum. Two patients were FIGO stage I-B barrel-shaped, five were stage II-B, and three were III-B. All patients responded to induction chemotherapy with five complete and five partial responses. At the completion of radiation therapy, nine patients had negative biopsies. One patient never reached a complete response and died of distant metastasis. Another underwent total exenteration for a central recurrence and was found to have microscopic paraaortic lymph node involvement. A third recurred in the parametrium. Two patients with barrel-shaped tumors underwent extrafascial hysterectomies; both had negative specimens and tolerated surgery well. Although follow-up is short, this new approach for advanced carcinoma of the cervix yielded excellent results and was well tolerated.

Adult↗
PubMed1987

Simple laboratory test of neuroendocrine disturbance in depression: 11 p.m. saliva cortisol.

Saliva cortisol was measured at 11 p.m. in a sample of 74 psychiatric inpatients composed of 24 primary endogenous depressives, 40 secondary depressives and 20 nondepressives (DSM III and Saint-Louis criteria). Primary depressives had significantly higher 11 p.m. saliva cortisol levels than nondepressives (p less than 0.02) and secondary depressives (p less than 0.05). In contrast, there were no significant differences between secondary depressive and nondepressive saliva cortisol levels. A saliva cortisol cutoff limit of 3.45 nmol/l identified primary depressives with a sensitivity of 62.5% and with a specificity of 75% in the depressive group, and 90% in the nondepressive group. The measurement of saliva cortisol at 11 p.m. could be used alone as a reliable and practical index of hypothalamic-pituitary-adrenal axis activity in depression, especially in outpatients.

Adolescent↗
PubMed1987

Effect of a low-fat diet on hormone levels in women with cystic breast disease. I. Serum steroids and gonadotropins.

For examination of the effect of a low-fat diet on serum estrogen, progesterone, and gonadotropin levels, 16 patients with cystic breast disease and cyclic mastalgia were studied before dietary intervention and at 2 and 3 months thereafter. Four-day food diaries indicated that total fat intake was reduced from a prediet average of 69 g (35% of total kilocalories/day) to an average of 32 g (21% of total kilocalories) after 3 months. Highly significant reductions (P less than .001) occurred in dietary cholesterol and less changes occurred in protein and total kilocalorie consumption (P less than .05); fiber intakes were not affected. After 3 months on this low-fat diet, there were significant reductions in luteal-phase serum total estrogens (P less than .001), estrone (P less than .005), and estradiol (P less than .01); progesterone, luteinizing hormone, and follicle-stimulating hormone levels were unchanged. Two of the 16 patients were excluded from the hormone statistical analyses because the serum progesterone levels were not consistent with sampling in the luteal phase of the menstrual cycle. It is concluded that a reduction of dietary fat intake to 20% of the total kilocalories will result in significant decreases in circulating estrogens in benign breast disease patients and that this effect is achievable without increasing dietary fiber consumption. Absence of changes in serum progesterone and gonadotropins during the dietary intervention is consistent with altered enterohepatic circulation of estrogens rather than with effects on the pituitary-ovarian axis.

Adult↗
PubMed1986

Tropomyosin crystal structure and muscle regulation.

The crystal structure of tropomyosin filaments has been solved to 15 A resolution by refinement of models against the diffraction data and heavy atom labeling of cysteine residues. These results confirm and extend earlier findings. The improved maps reveal the pitch of the coiled coil, the location of the cysteine residues, and the location and features of the overlapping molecular ends in the filaments. A correlation can now be made between regions of the amino acid sequence and key features of the molecule, such as contact sites in the lattice and departures from regularity along the coiled coil. The crystal shows remarkable dynamic features and the relative flexibility of different parts of the molecule as well as its anisotropic character have been determined. The structure and motions of tropomyosin in the crystal provide information on the structure of tropomyosin in muscle and its possible role in regulation. An atomic model of the molecule has been constructed, based on the low resolution X-ray results, together with the stereochemistry of alpha-helical coiled coils. In contrast to previous views, the molecule appears to display but one set of seven alpha-sites that permit weak linkages of the flexible tropomyosin filament to the actin helix. Correspondingly, we picture that in the "off" state of ATPase activity, the alpha-sites are not occupied; in the "on" state, they are only partly occupied; and in the "potentiated" state, they are more completely saturated. Control of contraction is therefore seen as a statistical mechanism requiring at least three distinct average conformations for the tropomyosin molecule on the actin helix.

Amino Acid Sequence↗