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N Galanti

Publications and source records attributed to N Galanti.

At least 19 recordsLinked to original sources
PubMed1992

Extremely divergent histone H4 sequence from Trypanosoma cruzi: evolutionary implications.

Trypanosoma cruzi presents six histones electrophoretically resolved in three gel systems. Indirect evidence shows that one of these histones, named e, corresponds to H4 in other species. We present evidence that histone e is H4 by sequencing its amino terminal end. The amino terminal of T. cruzi histone H4, unlike that of other H4s examined thus far is not blocked. Moreover, this protein presents two variants. This partial amino acid sequence of T. cruzi histone H4 differs greatly from homologous sequences of human, yeast, or Tetrahymena. Since the conservatism of the core histones (H2A, H2B, H3, and H4) is clearly illustrated by comparative sequence analyses, the data shown here demonstrates that T. cruzi histone H4 is the most divergent reported. Quantitative analysis of the data suggests that the rate of substitutions in the histone H4 amino terminal sequence varies among different lineages. We postulate a slow-down in the evolutionary rate of histone H4 amino terminal domain in the metazoa branch related perhaps to the appearance of a novel function for this domain.

Amino Acid Sequence↗
PubMed1992

HMG-like chromosomal proteins in Trypanosoma cruzi.

HMG-like chromosomal proteins from Trypanosoma cruzi were studied. Four HMG-like proteins, designated HMG A, HMG-B, HMG-C, and HMG-E, were isolated and found to have molecular weights of 35.5 kd, 27.5 kd, 21.8 kd and 10.4 kd, respectively. Immunological relatedness was demonstrated between the mammalian HMG 1,2 and the HMG-A and HMG-B from T. cruzi. The relative amounts of HMG-C and HMG-E proteins vary in T. cruzi depending to the proliferative stage of the cells. HMG-E protein is increased in proliferating cells when compared to its level in non-proliferating cells. HMG-C is increased in the non-proliferating cells. Probably, the shifts observed in the relative amounts of HMG-like proteins are related to the proliferating cells of this flagellate. The results are consistent with those described for other lower eukaryotes where the HMG-like proteins isolated are similar but not identical to HMG proteins from vertebrates.

Animals↗
PubMed1991

Relationship between DNA methylation and cell proliferation in Trypanosoma cruzi.

5-Azacytidine treatment of T. cruzi epimastigotes in culture induces active cell proliferation. This effect was detected as an increase in the cell number and [3H-methyl]thymidine incorporation into DNA. 5-Azacytidine does not alter other metabolic parameters. We have previously demonstrated that 5-azacytidine induces DNA hypomethylation in T. cruzi. Accordingly, we suggest that this chemical modification may be related to the control of T. cruzi cell division.

Animals↗
PubMed1990

DNA methylation in Trypanosoma cruzi.

DNA isolated from the protozoan Trypanosoma cruzi has been found to contain 5-methylcytosine. Analysis of T. cruzi DNA by both HpaII and MspI restriction endonucleases suggests that the sequence -CCGG- is not methylated. Probably T. cruzi DNA also contains N6-methyladenine. This report constitutes the first clear demonstration of the presence of methylated bases in the nuclear DNA from trypanosomes.

Adenine↗
PubMed1990

[University and creativity].

The University is a natural environment for the development of the creative aspects of man. Professional training and the solution of specific problems, though important, are secondary objectives. For those working in the University, freedom must be turned into a way of living; thus, creativity becomes possible. The University belongs to the nation and not to governments. This is the origin of the autonomous nature of the University and more than a privilege, it must be viewed as a basic requirement for creativity. The University is basically democratic since creativity is not related to race, religion, or politics. Finally, it is hierarchical since credit must be given to talent, training and experience.

Creativity↗
PubMed1990

Trypanosoma cruzi histones. Further characterization and comparison with higher eukaryotes.

Histones extracted from T. cruzi chromatin were analyzed in three electrophoretic systems. Our results show that a basic protein with some properties similar to those of histone H1 from higher eukaryotes is present in T. cruzi. However this protein presents different electrophoretic mobilities than H1 histone from higher eukaryotes in all three electrophoretic systems tested. Considering the marked differences observed in the electrophoretic mobilities of T. cruzi histones as compared with those from higher eukaryotes, it is proposed that histones are conservative proteins primarily with regard to their function.

Animals↗
PubMed1989

Changes in the content and distribution of sialic acid on the basal surface of isoproterenol-stimulated mouse parotid acinar cells.

The presence, distribution and content of sialic acid on the cell surface in collagenase-dispersed acini obtained both from unstimulated as well as from in vivo isoproterenol-stimulated mouse parotid have been studied. To this end, sialic acid residues have been qualitatively and quantitatively analyzed by 1) cytochemical labeling by wheat germ agglutinin (WGA), 2) biochemical procedures and 3) isotopic labeling by [3H]WGA (WGA-N-[acetyl-3H]-acetylated). Electron microscopy revealed striking differences in the binding of ferritin-conjugated WGA at the basal, lateral and apical cell surface. Unstimulated acinar cells showed a heavy patch-distributed binding of ferritin-conjugate on the basal cell surface while it was homogeneous and very scarce on the lateral one and absent on the apical cell surface. During the first few hours after isoproterenol, the WGA binding sites at the basal cell surface became homogeneously distributed. This fact was coincident with a loss of about 60 to 70% both in the content of neuraminidase-releasable sialic acid and in the binding of [3H]WGA to the acinar surface. These findings suggest that the release of sialic acid as free residues, which has been involved in the isoproterenol-triggered cell proliferation-inducing mechanism in the mouse parotid, would occur at the glycocalyx corresponding to the basal plasma membrane of the acinar cells.

Animals↗
PubMed1988

H 1 histone and histone variants in Trypanosoma cruzi.

Trypanosoma cruzi chromatin is not condensed in chromosomes during mitosis. In previous studies a characteristic H 1 was not found in SDS or in acid-urea-PAGE. Consequently, it was proposed that the particular behavior of T. cruzi chromatin in dividing cells was due to the absence of an H 1 histone. In the present work, histones from this parasite were systematically characterized by spectrofluorometric analysis, amino acid composition, PAGE in one and in two dimensions, differential extraction with PCA and TCA, immunological cross-reactivity with antisera, and immunoblotting. We conclude that T. cruzi contains all five histones, H 1 presenting solubility and immunological properties similar to those in other species, but with a particular electrophoretic mobility in Triton-PAGE. Thus an explanation other than the absence of H 1 should be offered in order to understand the behavior of T. cruzi chromatin during mitosis. Moreover, histone variants were described by two-dimensional PAGE. The presence of histone variants suggests that they may participate in the regulation of cell proliferation and differentiation of this parasite, as it has been postulated for higher eukaryotes.

Amino Acids↗
PubMed1979

Cell proliferation in the mouse parotid gland after unilateral parotidectomy.

Unilateral parotidectomy with or without total submandibulectomy has been used to induce cell proliferation in mouse parotid gland. Maximum DNA synthesis and mitosis were recorded four and five days after the operation. The double operation increased the proliferative response. Such proliferative stimulii was not accompanied by secretion and was sex independent. On the other hand, the response decreased with age. RNA and protein synthesis inhibitors showed that the stimulation of DNA synthesis depends on early protein synthesis, which seems to be synthesized on a preexisting template.

Animals↗
PubMed1976

The effect of isoproterenol upon the chemical composition of plasma membranes in the mouse parotid gland.

A single intraperitoneal injection of isoproterenol induces resting cells from the acini of the mouse parotid gland to enter the proliferative cycle. Parotid plasma membrane from non-stimulated and isoproterenol-treated mice were prepared by differential centrifugation of the homogenates. Comparing the chemical composition of plasma membranes from non-stimulated and isoproterenol-treated mice, no variation in the phospholipid/protein ratio was observed. However, the levels of neutral sugars, hexosamines and sialic acid falls drastically in the early prereplicative phase. The decrease in neutral sugars and hexosamines in plasma membranes caused by isoproterenol is imitated by pilocarpine, which induces secretion but little or no increase in DNA synthesis. However, pilocarpine does not mobilize sialic acid from the plasma membrane. Moreover, dosis of isoproterenol that elicits secretion but not mitosis in the acinar cells, does not induce the movement of sialic acid from the plasma membrane. The mobilization of sialic acid from plasma membranes caused by isoproterenol was also demonstrated in an in vitro system. Treatment of the plasma membrane with chloroform/methanol shows that around 60% of the sialic acid is present in the less polar phase. We conclude that the separation of sialic acid from the plasma membrane is one of the early steps in the sequence of events leading to DNA synthesis and cell division in the isoproterenol-stimulated parotid gland of mice.

Animals↗
PubMed1976

Changes in plasma membranes during the prereplicative phase of the isoproterenol-stimulated parotid glands of mice.

A single intraperitoneal injection of isoproterenol induces resting cells from the acini of the mouse parotid gland to enter the proliferative cycle. Parotid plasma membrane from non-stimulated and isoproterenol-treated mice were prepared by differential centrifugation of the homogenates. Comparing the chemical composition of plasma membranes from non-stimulated and isoproterenol-treated mice, no variation in the phospholipid/protein ratio was observed. However, the levels of neutral sugars, hexosamines and sialic acid fall drastically in the early prereplicative phase. The decrease in neutral sugars and hexosamines in plasma membranes caused by isoproterenol is imitated by pilocarpine, which induces secretion but little or no increase in DNA synthesis. However, pilocarpine does not mobilize sialic acid from the plasma membrane. Moreover, dosis of isoproterenol that elicits secretion but not mitosis in the acinar cells, does not induce the movement of sialic acid from the plasma membrane. The mobilization of sialic acid from plasma membranes caused by isoproterenol was also demonstrated in an in vitro system. Treatment of the plasma membrane with chloroform/methanol shows that around 60% of the sialic acid is present in the less polar phase. We conclude that the separation of sialic acid from the plasma membrane is one of the early steps in the sequence of events leading to DNA synthesis and cell division in the isoproterenol-stimulated parotid gland of mice.

Animals↗
PubMed1976

(3H)-isoproterenol binding to subcellular fractions of mouse parotid: relationship to cyclic nucleotide formation and the stimulation of DNA synthesis.

(3H) Isoproterenol binding to subcellular fractions of mouse parotid: Relationship to cyclic nucleotide formation and the stimulation of DNA synthesis. (Unión the (3H) Isoproterenol a fracciones subcelulares de parótida de ratón y su relacón con la formacón de nucleótidos cíclicos y la estimulación de la síntesis de DNA). Arch. Biol. Med. Exper. 10: 105-114, 1976. Tritiated isoproterenol binds to all subcellular fractions of mouse parotid but 70% of the binding is to the nuclear fraction. Binding to other mouse tissues was less than to the parotid. The patterns of binding did not correlate with the distribution of adenylate cyclase, guanylate cyclase or catechol-O-methyl transferase among the fractions or tissues nor with the extent of response in stimulation of DNA synthesis among the tissues. Inhibition of (3H) Isoproterenol binding to parotid fractions by catecholamine analogs was studied. There was no correlation between their ability to inhibit binding and the ability of the analogs themselves to raise cyclic AMP levels or stimulate DNA synthesis.

Adenosine Monophosphate↗
PubMed1975

The purification and characterization of plasma membranes and the subcellular distribution of adenylate cyclase in mouse parotid gland.

1. Plasma membranes have been purified 17-fold from mouse parotid gland homogenates prepared in hypertonic sucrose media using differential centrifugation. The method is fast and simple. The membranes were characterised by electron microscopy, enzyme composition and chemical composition. Further purification was achieved by isopycnic centrifugation in discontinuous sucrose gradients. 2. The purified membranes contain an adenylate cyclase activity which is stimulated by isoproterenol and fluoride. Only 50% of the total adenylate cyclase activity sedimented in the plasma membrane fraction. The rest of the activity resided in the crude nuclear and mitochondrial pellets. However, this adenylate cyclase activity was not associated with these organelles but with membrane fragments in the pellets. Purified nuclei did not contain adenylate cyclase activity. 3. Adenylate cyclase activity was also localised by electron microscopic cytochemistry. Besides being found at the plasma membrane, large amounts of adenylate cyclase were found in a small proportion of the vesicles within the acinar cells, which appeared to be secondary lysosomes. 4. Adenylate cyclase activities, under standard assay conditions, are proportional to the time of incubation and the concentration of enzyme. The enzyme requires both Mg-2+ and CA-2+ for activity. Isoproterenol increased activity 2-fold and this increase is abolished by beta-adrenergic blocking agents.

Adenosine Triphosphate↗