Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transplantable mouse melanomas possess a melanotropin-sensitive adenylate cyclase system which is responsive to alpha-melanotropin, beta-melanotropin, adrenocorticotropin (ACTH) and prostaglandin E1. It was found that sensitivity to ACTH was not directed towards the ACTH activity but to the intrinsic melanotropin activity of the ACTH molecule. Therefore, the melanotropin-sensitive adenylate cyclase system is hormonally specific to the intrinsic melanotropin activity of peptide hormones and is unique in the melanoma tissue. The significance of the sensitivity to prostaglandin E1 is obscure at present. The melanotropin-sensitive adenylate cyclase requires the presence of Mg2+ or Mn2+, for its enzymic activity. Ca2+ inhibit the enzyme in the presence of a wide range of concentrations of Mg2+. The enzymic activity is ATP concentration-dependent and the saturation concentration appears to be 1 mM. The enzyme is very labile in the unfractionated tumor homogenates. A washed 11000 X g particulate fraction, representing about 30-60% of the total enzymic activity, was found to be more stable and could be stored at 5 degrees C for 2 h without appreciable loss of the activity. This fraction retained sensitivity to melanotropin, prostaglandin E1 and NaF. About 20% of the activity of the tumor homogenate could not be sedimented by centrifugation at 105000 X g for 60 min. This "soluble" fraction was not responsive to melanotropin, prostaglandin E1 and NaF and might be a degradative product produced by the fractionation. Cyclic AMP and alpha-melanotropin were able to increase the tyrosinase activity of isolated mouse melanoma-cells in vitro under the same conditions.
 ...
PMID:PHrmonal specificity of the melanotropin-sensitive adenylate cyclase of mouse melanoma and effect of cyclic AMP on the tyrosinase activity of mouse melanoma cells, in vitro. 0 31

Tyrosine hydroxylase, dopa oxidase, and peroxidase activities were studied in soluble fractions of B16 melanoma tumor homogenates by polyacrylamide gel disc electrophoresis. Stained gels were scanned photometrically and gel slices were assayed radiometrically. In these preparations, the two bands of tyrosine hydroxylating activity were completely separated from the peroxidase activity but coincided with two major bands of dopa oxidase activity. The third dopa oxidase band coincided with the single band of peroxidase activity. The soluble fraction of cultured cell homogenates had no peroxidase activity, but the two tyrosine hydroxylase bands coincided exactly with the two dopa oxidase bands. Therefore, in the soluble fraction of the murine melanoma bifunctional tyrosinase does exist as two electrophoretically separable forms which are independent of peroxidase.
 ...
PMID:Characteristics of tyrosinase in B16 melanoma. 1 62

The tyrosinase activity in two sucrose gradient isolated melanosome fractions from a melanotic hamster melanoma was found to increase after alpha-chymotrypsin treatment. The enhancement in tyrosinase activity had its maximum at a concentration of 1 mg/ml alpha-chymotrypsin after 120 min incubation at 37 degrees C. No direct activating effect of alpha-chymotrypsin was found either on the soluble tyrosinase fraction from freshly prepared untreaed whole-tumor homogenate or on purified mushroom tyrosinase. The activating effect of alpha-chymotrypsin upon the melanosome tyrosinase is believed to be due to the endopeptidic hydrolysis of the--CO--NH--bound existing between tyrosinase and tyrosine and phenylalanine residues in the melanin molecule. Although alternative interpretations are not excluded, the observed enhancement in tyrosinase activity after alpha-chymotrypsin treatment of melanosomes might indicate the existence of an "enzyme liberating" mechanism in the melanosomes.
 ...
PMID:Chymotrypsin activation of melanosome tyrosinase in hamster melanotic melanoma. 11 73

In the genetically determined pigment cell tumors of platyfish and platyfish-swordtail hybrids, the degree of malignancy of pigment cells which have been neoplastically transformed by a tumor gene (Tu) depends on the type and number of certain regulating genes (R). In the present study, the tyrosinase activities in tumors of different degrees of malignancy (black spots, premelanomas, melanomas) have been determined. The results demonstrate a close correlation between the level of tyrosinase activity and the degree of malignancy. Spot patterns consisting of completely differentiated (benign) Tu-transformed cells show no tyrosinase activity. Premelanomas containing a few incompletely differentiated (malignant) Tu-transformed cells in addition to many differentiated ones show moderate tyrosinase activities. Melanomas which contain increasing numbers of incompletely differentiated cells with increasing growth rates show high to extremely high tyrosinase activities. Thus, the tyrosinase levels present in these tumors can be used as an indicator for the degree of differentiation and, thereby, for the degree of malignancy of the neoplastically transformed pigment cells.
 ...
PMID:Melanogenesis in genetically determined pigment cell tumors of platyfish and platyfish-swordtail hybrids: correlation between tyrosine activity and degree of malignancy. 14 30

Three cases of metastatic malignant lesions are presented. By conventional pathologic examination these lesions were diagnosed as undifferentiated carcinomas. They were studied using a chimpanzee antiserum specific for human melanoma-associated antigens. In each case, cells from the tumor were reactive with the anti-melanoma antiserum. The tumors were also studied using the DOPA test. All three tumors were positive in the DOPA test, suggesting the presence of tyrosinase within the tumor cells. The results suggest that serologic identification of melanoma may provide a rapid, inexpensive means for tumor diagnosis.
 ...
PMID:Immunodiagnosis of melanoma using chimpanzee antihuman melanoma antiserum. 32 27

Conley et al., in 1971, described a special type of melanoma characterized by a superficial melanic lesion at the onset; repeated local relapses as subcutaneous tumorations with an histological picture closely resembling an atypical fibroxantoma or fibrosarcoma. After a review of all the published material the autors presents a personal case with the clinical, histological and evolutive characteristics of this disease. The most interesting findings of the published case are the following: The special stains for the melanocytes (silver stain, Dopa, tyrosinase and cholinesterase) were all negative. There was an intense positivity for the lisosomal enzymes (non specific sterases, and acid phosphatases). The ultrastructural study of the tumoral tissues as well as the cells of cultures showed abundant cells with tumoral aspects, with prominent nucleoli somewhat dilated granular endoplasmic reticulum, myelin-like figures, lipidic vacuoles and abundant lisosomes. No melanosomes or premelanosomes were observed. Beside these tumoral cells abundant typical fibroblastic elements were found. There was a great amount of collagen fibers with periodicity superior to the normal. The conclusion is that the desmoplastic melanoma must be considered as a tumor of mesenchimatous origin intervening in its development multiple local and general factors.
 ...
PMID:[Desmoplastic melanoma]. 34 19

Alteration in DOPA-oxidase activity of Harding-Passey melanoma microsomal fraction tyrosinase, activation of tyrosinase after partial delipidization of the microsome, phospholipid composition of both native microsomes and the ones after delipidization have been studied. In the course of tumor growth (starting on the 14th day after tumor transplantation) the tyrosinase activity has been shown to decrease monotonously both in native microsomes and in the ones after delipidization. The phospholipid composition alters both in the process of tumor growth and after delipidization. Alteration in the tyrosinase activity in native microsomes as well as after their delipidization has been found to depend on the relative composition of certain phospholipids. In those cases a linear correlation between the enzyme activity and the phosphatydylethanolamine of phosphatydylcholine ratio has been found. This interrelationship may be accounted for by either simultenous presence of inhibitors and activators of the enzyme activity in the lipids or by changes in the membrane structure depending on the relative phospholipid composition.
 ...
PMID:[Investigation of tyrosinase activity and phospholipid composition in Harding-Passey melanoma microsomal fraction]. 41 89

Asparaginase [EC 3.5.1.1.] of Escherichia coli, an anti-tumor enzyme, was inactivated in a time-dependent fashion by mushroom tyrosinase [EC1.14.18.1.]. The inactivation did not proceed, however, when heat-inactivated tyrosinase was used. Exculusion of the atmospheric oxygen or addition of diethyldithiocarbamate, a copper selective chelating agent, prevented the inactivation. The difference absorption spectrum of tyrosinase-inactivated asparaginase versus intact asparaginase exhibited the appearance of marked absorption peaks at 300 and 350 nm. These results indicate that the tyrosyl residue(s) of asparaginase, which is essential for the activity is enzymatically modified by tyrosianes.
 ...
PMID:Studies of enzyme-catalyzed modification of proteins. I. Tyrosinase-catalyzed modification of asparaginase. 81 77

In certain fish hybrids, malignant transformation of pigment cells is due to the presence of a tumor gene (Tu), the action of which is controlled by several regulatory elements. Absence of these controlling genes causes rapid proliferation of the Tu-transformed cells and ultimately results in melanoma formation. One of these genes has been identified as a differentiation gene (Diff), since it seems to control the differentiation of the transformed pigment cells. Light and electron microscopy of Tu-transformed cells of fish differing in the dosage of Diff, and the determination of tyrosinase activity in homogenates of the respective tissues revealed that the degree of cellular differentiation depends on the dosage of Diff present in the genome. It is concluded that the gene Diff promotes the differentiation of malignant melanoma cells into benign melanophores.
 ...
PMID:Genetic control of cell differentiation in platyfish-swordtail melanomas. 81 38

The eye of a 47 year old man with tyrosinase-positive oculocutaneous albinism, photophobia, nystagmus and visual acuity 0, 4-0, 5 was histologically examined after orbital exenteration for neoplasia. Histologic serial sections of the centre of the retina showed a continuous 6-8 cell-layer of ganglion cells, without any suggestion of a foveolar pit. The outer layers of the macular retina were altered secondarily by tumor-impression-folds; they were unremarkable at the periphery as were the acid mucopolysaccharides in the receptor region. Electron microscopy of the uvea and the retinal pigment epithelium showed a normal number of pigment granules but a deficiency of melanin, as well as structural anomalies. The absence of the foveolar pit and the decrease of visual acuity in tyrosinase-positive albinism is caused by definite morphologic alteration in the arrangement of ganglion cells in the macular region in the sense of a foveolar aplasia. The etiology is discussed. An identic anomaly has been described in aniridia, similar ones in other congenital ocular diseases.
 ...
PMID:[Foveolar aplasia in tyrosinase-positive oculocutaneous albinisim (author's transl)]. 82 41


1 2 3 4 5 6 7 8 9 10 Next >>