Heterogeneity of peritoneal macrophages in hamsters-bearing transplantable melanomas in relation to their transglutaminase.

The level of transglutaminase activity has been investigated by the fluorescence method in peritoneal macrophages of control and transplantable melanomas bearing hamsters. If the transglutaminase activity is concerned the macrophages in no one of the groups examined were a homogenous population. Differences in macrophage heterogeneity in hamsters bearing two melanoma lines of the same origin but showing changed biological properties were observed.     

Heterogeneity of neural crest-derived melanocytes

The majority of melanocytes originate from the neural crest cells (NCC) that migrate, spread on the whole embryo’s body to form elements of the nervous system and skeleton, endocrinal glands, muscles and melanocytes. Human melanocytes differentiate mainly from the cranial and trunk NCC. Although melanocyte development has traditionally been associated with the dorsally migrating trunk NCC, there is evidence that a part of melanocytes arise from cells migrating ventrally. The ventral NCC differentiate into neurons and glia of the ganglia or Schwann cells. It has been suggested that the precursors for Schwann cells differentiate into melanocytes. As melanoblasts travel through the dermis, they multiply, follow the process of differentiation and invade the forming human fetal epidermis up to third month. After birth, melanocytes lose the ability to proliferate, except the hair melanocytes that renew during the hair cycle. The localization of neural crest-derived melanocytes in non-cutaneous places e.g. eye (the choroid and stroma of the iris and the ciliary body), ear (cells of the vestibular organ, cochlear stria vascularis), meninges of the brain, heart seems to indicate that repertoire of melanocyte functions is much wider than we expected e.g. the protection of tissues from potentially harmful factors (e.g. free radicals, binding toxins), storage ions, and anti-inflammatory action.     

Crystal structure of the YffB protein from <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> suggests a glutathione-dependent thiol reductase function

Background  

The yffB (PA3664) gene of Pseudomonas aeruginosa encodes an uncharacterized protein of 13 kDa molecular weight with a marginal sequence similarity to arsenate reductase from Escherichia coli. The crystal structure determination of YffB was undertaken as part of a structural genomics effort in order to assist with the functional assignment of the protein.     

Analysis of 5-methylcytosine in DNA of breast and colon cancer tissues

5-methylcytosine (m(5)C) can be used as a sensitive marker of progress of the tumor formation induced by the oxidative damage reactions. We have analyzed the amount of m(5)C in DNA of patients with breast and colon cancers. Two dimensional thin layer chromatography (TLC) has been used to monitor 5-methylcytosine level in DNA extracted from cancer tissues. The level of methylation of cytosine at C-5 position in DNA from breast cancer patients correlates well with the malignancy of tumors. Interestingly higher amount of m(5)C in DNA for the breast cancer patients treated with different chemotherapeutics was observed. It suggests an activation of DNA methyltransferase as well as a genomic suppression of the DNA repair genes expression. These differences clearly reflect the health condition of patients and support the global analysis of m(5)C in DNA as a good marker for diagnosis of neoplasia in clinical practice.     

The effect of aromatase inhibitor, fadrozole, on sGnRHa stimulated LH secretion in goldfish (Carassius auratus) and common carp (Cyprinus carpio)

The aromatase inhibitor, fadrozole, was applied to common carp and goldfish in order to examine its ability to increase the spontaneous and sGnRHa stimulated LH secretion. First, trials in goldfish in 2003 showed fadrozole's moderate ability to potentiate sGnRHa-stimulated LH secretion. However, this ability was much weaker than that obtained with dopamine antagonist, pimozide. There was no ovulation in fadrozole-treated fish. Several experiments on goldfish and carp during the two consecutive years with the different treatment regimes and doses of fadrozole did not confirm the optimistic results obtained in 2003. This shows that fadrozole is unable to replace the antidopaminergic drugs being used in fisheries practice.     

Spontaneous apoptosis of melanotic and amelanotic melanoma cells in different phases of cell cycle: relation to tumor growth

Since the spontaneous alteration of native melanotic (Ma) into amelanotic (Ab) transplantable melanoma line it has been observed that this alteration is accompanied by the acceleration of growth of Ab line. The aim of the present study was to check and estimate spontaneous apoptosis of cells from cell cycle phases. Cytometric cell cycle analysis was performed by staining cells with propidium iodide (PI). Apoptosis estimated by the TUNEL method, alterations in the plasma membrane structure (annexin V staining), changes in the mitochondrial transmembrane potential--delta psi m (JC-1 staining) showed that amelanotic melanoma cells have decreased ability to undergo spontaneous apoptosis. The obtained results showing that in the native melanotic line about 30% of cells are in S+G2/M phases and that 33% of these cells undergo apoptosis could lead to the conclusion that the slower growth of this melanoma line is the result of lower proliferation activity and higher rate of apoptosis of these tumor cells. The number of cells in S+G2/M phases in amelanotic melanoma line increases up to 40% and only 7% of them undergo apoptosis. This observation seems to suggest that the expansive growth of this melanoma line depends mainly on the decreased ability to undergo spontaneous apoptosis, especially in case of cells from S+G2/M phases. Moreover, the obtained results indicate that alteration of melanotic line into amelanotic one, accompanied by differences in many biological features also concerns basic cell processes such as cell cycle and cell death.     

Diversity of the plasma membrane properties of transplantable hamster melanomas with regard to the expression of P-glycoprotein.

A comparison of the expression of P-glycoprotein (Pgp) was performed in two forms of hamster transplantable melanomas of common origin, but differing in growth rates and levels of differentiation. The expression of P-glycoprotein in plasma membranes of these two forms of melanomas was estimated by the western blot analysis and the transport activity of the Pgp compared by flow cytometry. It was observed that a spontaneous alteration in the original melanotic melanoma leading to a formation of the amelanotic form characterized by higher growth rate, greater anaplasticity and leading to the animals' death after a shorter time from inoculation, was accompanied by a decrease in the Pgp expression and activity, due to simultaneous appearance of a small population of amelanotic cells with high Pgp expression and activity, and disappearance of this activity from the major population. It is possible, that the activity of Pgp in the melanoma cell membranes reflects the degree of cell differentiation.     

Construction and preliminary characterisation of mini-derivatives of a large (107-kb) cryptic plasmid of the sulfur bacterium Thiobacillus versutus

Abstract Several mini-replicons, derivatives of a large (107-kb) cryptic Thiobacillus versutus pTAV1 plasmid, were obtained. The pTAV1 derivatives confer all functions sufficient for autonomous replication in T. versutus but they cannot be maintained in Escherichia coli . The fragment of pTAV1 (4-kb) included in the smallest mini-replicon, pTAV202, encodes for two proteins of approximately 26 and 45 kDa. The region responsible for stable maintenance of pTAV1 derivatives (and presumably entire pTAV1) was located in defined 14-kb fragment of pTAV1 genome. Hybrid plasmids composed of E. coli vectors (pBGS18 or pWSK29) and pTAV202 replicon were constructed and their activity in both hosts tested.