PubMed Health⌕ Search

Biomedical subjects

R Lucchini

Publications and source records attributed to R Lucchini.

At least 37 records · Page 2Linked to original sources
PubMed1994

Chromatin structure and transcriptional activity around the replication forks arrested at the 3' end of the yeast rRNA genes.

Replication intermediates containing forks arrested at the replication fork barrier near the 3' end of the yeast rRNA genes were analyzed at the chromatin level by using in vivo psoralen cross-linking as a probe for chromatin structure. These specific intermediates were purified from preparative two-dimensional agarose gels, and the extent of cross-linking in the different portions of the branched molecules was examined by electron microscopy and by using a psoralen gel retardation assay. The unreplicated section corresponding to the rRNA coding region upstream of the arrested forks appeared mostly heavily cross-linked, characteristic of transcriptionally active rRNA genes devoid of nucleosomes, whereas the replicated daughter strands representing newly synthesized spacer sequences showed a nucleosomal organization typical for bulk chromatin. The failure to detect replication forks arrested at the 3' end of inactive rRNA gene copies and the fact that most DNA encoding rRNA (rDNA) is replicated in the same direction as transcription suggest that replication forks seldom originate from origins of replication located immediately downstream of inactive genes.

Chromatin↗
PubMed1993

Chromatin structures and transcription of rDNA in yeast Saccharomyces cerevisiae.

The chromatin structure of yeast ribosomal DNA was analyzed in vivo by crosslinking intact cells with psoralen. We found that in exponentially growing cultures the regions coding for the 35S rRNA precursor fall into two distinct classes. One class was highly accessible to psoralen and associated with nascent RNAs, characteristic for transcriptionally active rRNA genes devoid of nucleosomes, whereas the other class showed a crosslinking pattern indistinguishable from that of bulk chromatin and was interpreted to represent the inactive rRNA gene copies. By crosslinking the same strain growing in complex or minimal medium, we have shown that yeast cells can modulate the proportion of active (non-nucleosomal) and inactive (nucleosomal) rRNA gene copies in response to variations in environmental conditions which suggests that yeast can regulate rRNA synthesis by varying the number of active gene copies, in contrast to the vertebrate cells studied so far. Whereas intergenic spacers flanking inactive rRNA gene copies are packaged in a regular nucleosomal array, spacers flanking active genes show an unusual crosslinking pattern suggesting a complex interaction of regulatory factors and histones with DNA.

Chromatin↗
PubMed1992

Different chromatin structures along the spacers flanking active and inactive Xenopus rRNA genes.

The accessibility of DNA in chromatin to psoralen was assayed to compare the chromatin structure of the rRNA coding and spacer regions of the two related frog species Xenopus laevis and Xenopus borealis. Isolated nuclei from tissue culture cells were photoreacted with psoralen, and the extent of cross-linking in the different rDNA regions was analyzed by using a gel retardation assay. In both species, restriction fragments from the coding regions showed two distinct extents of cross-linking, indicating the presence of two types of chromatin, one that contains nucleosomes and represents the inactive gene copies, and the other one which is more cross-linked and corresponds to the transcribed genes. A similar cross-linking pattern was obtained with restriction fragments from the enhancer region. Analysis of fragments including these sequences and the upstream portions of the genes suggests that active genes are preceded by nonnucleosomal enhancer regions. The spacer regions flanking the 3' end of the genes gave different results in the two frog species. In X. borealis, all these sequences are packaged in nucleosomes, whereas in X. laevis a distinct fraction, presumably those flanking the active genes, show a heterogeneous chromatin structure. This disturbed nucleosomal organization correlates with the presence of a weaker terminator at the 3' end of the X. laevis genes compared with those of X. borealis, which allows polymerases to transcribe into the downstream spacer.

Animals↗
PubMed1989

A test of 'polymerase handover' as a mechanism for stimulating initiation by RNA polymerase I.

On the tandemly linked ribosomal genes of Xenopus laevis, the RNA polymerase transcribes past the 3' end of the 40S coding region and terminates at T3 just upstream of the gene promoter. The close proximity of T3 to the gene promoter, and the functional interdependence of these two elements, has led to the suggestion that polymerase terminating at T3 might be passed directly to the gene promoter. Such a mechanism might be necessary to maintain the characteristic high rate of transcription initiation seen on the ribosomal genes. We have performed a direct test of this model by introducing chain-terminating psoralen adducts into a circular plasmid containing a single gene promoter with its attendant T3 region upstream. We find that the psoralen adducts can completely prevent polymerase from traveling around the template circle (and thus prevent polymerase from approaching the promoter from upstream) without affecting the rate of transcription initiation at the gene promoter. This result suggests that recycling of polymerase from T3 to the promoter is not a significant mechanism in maintaining high initiation rates.

Animals↗
PubMed1987

Structure of the extrachromosomal ribosomal RNA chromatin of Physarum polycephalum.

Isolated nucleoli from exponentially growing microplasmodia of Physarum polycephalum were digested with micrococcal nuclease or DNAase I, or were photoreacted with trimethyl psoralen. In the coding region for the precursor of the ribosomal RNA, micrococcal nuclease and DNAase I digestions show predominantly a smear, and treatment with psoralen leads to a fairly continuous crosslinking of the DNA. All three assays are compatible with the absence of a typical nucleosomal array in most of the gene copies. In contrast, in the central non-transcribed spacer, except in the immediate 5'-flanking region, micrococcal nuclease and DNAase I digestions yield fragments that are multiples of a basic repeat, compatible with a nucleosomal packing of this region. The crosslinking pattern with psoralen confirms this conclusion. In addition, there are three sites over 400 base-pairs long that are inaccessible for psoralen crosslinking. Two of these sites have been mapped to the putative origins of replication. In the terminal non-transcribed spacer, except in the immediate 3'-flanking region, digestions with micrococcal nuclease and DNAase I give a smeared repeat. The crosslinking pattern after treatment with psoralen suggests that this region is packed in nucleosomes, except for about 900 base-pairs constituting the telomere regions of the linear extrachromosomal palindromic rDNA. Micrococcal nuclease digestion of the immediate 5'-flanking region shows a complete absence of any nucleosomal repeat, but digestion with DNAase I leads to a faint ten base-pair repeat. In contrast, in the 3'-flanking regions both nuclease assays indicate a chromatin structure similar to the coding region. Both flanking regions are unusual with respect to psoralen crosslinking, in that crosslinking is reduced both in chromatin and deproteinized DNA. On the basis of the known sequence-dependent psoralen crosslinking and the established sequences in these regions, crosslinking should be expected to occur. However, it does not and we therefore propose the presence of an unusual DNA conformation in these regions.

Chromatin↗
PubMed1985

Adenosine deaminase and terminal deoxynucleotidyl transferase in human lymphomas: an aid to the diagnosis and subclassification of lymphoblastic lymphomas.

Adenosine deaminase (ADA) and terminal deoxynucleotidyl transferase (TdT) activities were determined on 97 biopsy specimens obtained from patients with non-neoplastic diseases (12 cases), Hodgkin (30 cases), and non-Hodgkin lymphomas (55 cases). Thirty additional cases were tested only for TdT. TdT was positive in 10 out of 13 lymphoblastic lymphomas (LL) examined and negative in all the other specimens, including the ten cases of the immunoblastic type. Levels of ADA above 350 U/mg of protein were found in 10 out of 12 LL tested, but not in any other specimen. The 3 TdT- LL had high contents of ADA. Therefore, all LL can be detected using both ADA and TdT markers. The 3 TdT- LL had a heterogeneous phenotype and their possible origin is discussed in view of the possibility that they constitute a rare entity distinct from the more common TdT+ LL. Very low levels of ADA (below 100 U/mg of protein) were found in chronic lymphocytic leukemia and immunocytoma, and in Burkitt's lymphoma. In other B-cell non-Hodgkin lymphomas, intermediate values between 100 and 350 U were often found, and this finding could be relevant to the different cellular origin of the various B-cell neoplasias. We conclude that ADA distribution is solid lymphoid tumors reflects the cellular origin of these neoplasias. Adenosine deaminase alone and in combination with TdT can be useful in the diagnosis and classification of childhood lymphomas in which the immature hystotypes predominate.

Adenosine Deaminase↗
PubMed1985

Relation between enzymatic activities and the degree of malignancy of human lymphomas.

The relationship between the intracellular levels of DNA polymerase alpha (DP-alpha), adenosine deaminase (ADA) and lactate dehydrogenase (LDH) and the degree of malignancy of human lymphomas was investigated. Twelve non-neoplastic lymph nodes and 88 malignant lymphomas were examined. For non-Hodgkin's lymphomas (NHL) the low or high grade of malignancy was established according to three classifications: the Rappaport, the Kiel and the Working Formulation for Clinical Usage, with the latter also recognizing an intermediate grade group. Non-neoplastic lymph nodes had significantly lower levels of all the three enzymes than those found in high-grade malignant NHL (the P value ranged from less than 0.02 to less than 0.001). Hodgkin's disease, a slowly evolving neoplasia, showed lower levels of DP-alpha (P less than 0.001) and ADA (P less than 0.001), but not of LDH, than high-grade NHL. Among NHL, whatever classification was used, the low-grade malignant lymphomas had significantly lower levels than the high-grade ones for all the three enzymes (P less than 0.005 or P less than 0.001). The intermediate-grade group of the Working Formulation differed from the high-grade group for DP-alpha (P less than 0.01) and ADA (P less than 0.02) but not for LDH. It differed from the low-grade group only for ADA (P less than 0.005). Lymphoblastic and Burkitt's lymphomas were the groups with the highest levels of the three enzymes. Among low-grade lymphomas very low values were found in the histological entities defined as DLWD in the Rappaport classification, CLL and lymphoplasmacytoid immunocytoma in the Kiel classification and small lymphocytic (group A) in the WF. The levels of all enzymes in these histotypes were always significantly different from the other low-grade histotypes, and from the intermediate-grade ones of the WF. In the Kiel classification polymorphous lymphoplasmacytoid lymphoma, recently recognized as a group with a quite aggressive clinical course, was characterized by high levels of all three enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Deaminase↗
PubMed1984

Multienzymatic analyses of human malignant lymphomas. Correlation of enzymatic data with pathologic and ultrastructural findings in Burkitt's and lymphoblastic lymphomas.

Enzyme activity measurements are of great relevance to the classification and biochemical characterization of the various types of leukemias, but they have been much less studied in solid lymphoid tumors. The authors report investigations in human lymphomas. The levels of the following enzymes were determined: terminal deoxynucleotidyl transferase (TdT), deoxyribonucleic acid polymerase alpha (DP alpha), adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP), thymidine and uridine kinases (TK and UK, respectively), and thymidine phosphorylase (ThPh). Moreover, cytochemical investigations were done in the group of Burkitt's lymphoma (BL) and lymphoblastic lymphoma (LL), and ultrastructural studies were performed in seven of the nine LL of this series. These results were obtained: (1) TdT (90 cases) was highly specific for LL; eight of nine LL were positive, and all other histologic types were negative; the only TdT-, acid esterase (AcE) positive, nonconvoluted LL was probably related to TdT- normal medullary thymocytes, and had an unfavorable clinical course with resistance to a vincristine-and-prednisone-including treatment; (2) ADA (61 cases) could distinguish clearly between the high levels of LL and the low levels found in any other group of lymphomas; among LL, the highest values were found in T-cell-derived neoplasias, and the lowest value in a periodic acid-Schiff (PAS) positive, acid phosphatase negative case that showed the presence of large nucleoli at the ultrastructural analysis, a finding that is unusual for LL and possibly related to a more immature differentiation stage; (3) PNP (39 cases) values alone were not clinically relevant, but together with ADA levels, a subset of T-LL with high ADA:PNP ratio could be selected among LL; (4) DP alpha (61 cases), and TK and UK (37 cases) were found in concentrations reflecting the malignancy of the non-Hodgkin's lymphoma, and were more elevated in the high-grade malignant lymphomas; (5) ThPh (34 cases) was always elevated in Hodgkin's disease, but low in Burkitt's lymphoma and LL; thus, they had a high TK:ThPh ratio that could be useful in predicting clinical response to thymidine treatment. The authors think that taken together, multiple enzyme determinations could be useful in the characterization of human lymphomas.

Adenosine Deaminase↗
PubMed1984

Poly(A) polymerase distribution in normal and malignant lymphoid cells.

The incorporation of ATP on poly(A) primers catalyzed by poly(A) polymerase was investigated in normal and neoplastic lymphoid cells from animal and human sources. High levels of the enzyme were found in mouse thymus, in chicken bursa and thymus, as well as in neoplastic cells from patients affected by lymphoblastic and Burkitt's lymphomas. Low or very low quantities were found in peripheral blood lymphocytes, chronic lymphocytic leukemia cells, normal lymph nodes and solid lymphoid tissues of Hodgkin's disease. In general, the enzymatic content of neoplastic lymphoid cells reflected those of their normal counterpart. No effect of fasting or cortisone treatment on poly(A) polymerase in mouse spleen, thymus or liver was found. No particular relationships with B, T or non-T, non-B lineages were observed, but some relationship with DNA polymerase alpha was found. Therefore, it may be that poly(A) polymerase levels are related to the proliferative activity of the cellular populations.

Animals↗
PubMed1984

Chromatin structure of a hyperactive secretory protein gene (in Balbiani ring 2) of Chironomus.

We examined the chromatin structure of a Balbiani ring (secretory protein gene) in the salivary glands of Chironomus larvae in its hyperactive state after stimulation with pilocarpine. For the inactive state of the gene an established tissue culture cell line, not expressing the gene, was used. Electron microscopy showed an RNA polymerase density of approximately 38/microns. Micrococcal nuclease digestion of purified nuclei followed by DNA transfer and hybridization revealed a smear with no recognizable discrete DNA fragments. Without pilocarpine stimulation a faint nucleosomal repeat was superimposed upon the smear, and in tissue culture cells a clear nucleosomal repeat was revealed. The restriction enzyme XbaI, which has a 6-bp recognition sequence, cut the gene in the hyperactive chromatin state, but not in its inactive conformation. The combined results are best explained by the absence of most of the nucleosomes in this hyperactive RNA polymerase II transcribed gene.

Animals↗
PubMed1983

Lactate dehydrogenase levels in cellular extracts of human malignant lymphomas.

Serum lactate dehydrogenase (LDH) levels have been claimed as an independent prognostic factor in non-Hodgkin's lymphomas (NHL). In the present study, the intracellular and serum LDH levels in Hodgkin's (HD) and NHL were investigated. We found that among NHL, the histologic types of high-grade malignancy (lymphoblastic, immunoblastic and centroblastic), according to the Kiel classification, have a significantly higher intracellular (p less than 0.01) and serum (p less than 0.05) content of this enzyme than those of low-grade malignancy. This finding could explain in part the relation between high serum LDH levels and poor prognosis. It is also possible that the stage of the disease at the moment of the serum determination could be related to the serum LDH level, because a large tumor burden is likely to release more enzyme than a smaller one. However, we could not test this hypothesis because in our series there was ony one NHL patient with stage I or II. Serum LDH level could be a predictor of prognosis in NHL because of its relationship with more malignant histological types, and possibly with more advanced diseases.

Biopsy↗
PubMedDate not supplied

Studies on terminal deoxynucleotidyl transferase and adenosine deaminase in myasthenic thymus.

Thymic function in myasthenic patients was examined using two biochemical markers which specifically define a population of cortisone-sensitive cortical thymocytes. The enzymatic activities of terminal deoxynucleotidyl transferase (TdT) and adenosine deaminase (ADA) were determined in 13 samples. High contents of both enzymes were found in young patients. The enzymatic activities were easily detectable also in the oldest patients, despite the morphological involution and the decrease in TdT which are known to occur with age in the normal thymus. TdT and ADA-containing cells were almost completely depleted in all the 3 treated patients by the corticosteroid treatment which provides a non-surgical alternative to the elimination of this lymphoid population by thymectomy. The persistence of TdT and ADA activity in old age, and their inhibition by the corticosteroid treatment.

Adenosine Deaminase↗
PubMedDate not supplied

Lack of TdT and immunoglobulin and T-cell receptor gene rearrangements in Hodgkin's disease.

To study the pathogenesis of Hodgkin's disease (HD), which today remains obscure, we have undertaken a combined experimental approach: determination of TdT and molecular analysis of rearrangements of immunoglobulin heavy chain (IgH), T-cell receptor (TCR) beta chain and the T-cell rearranging gamma (TRG) genes. TdT determination indicate would the presence of immature cells that are not detected in the normal lymphnode; molecular analysis of the rearrangements of these genes would reveal the presence of even a small monoclonal population of both T and B lineages in the lymphnodes. We believe that the combination of these two types of analysis can indicate whether an expanding lymphoid clone is responsible for this disease. TdT determination was negative in all 41 cases tested. Gene rearrangements were studied in 10 cases for IgH and TCR beta genes and in 5 cases for the TRG gene. No abnormal band beside the germ-line ones was detected in any of our cases, ruling out the presence of a minor neoplastic population. We can explain these results in at least three ways: first, the neoplastic population could represent less than 1% of the total, thus escaping detection by current techniques; second, the neoplastic population is not lymphoid in nature or is composed of mature cells that do not rearrange Ig and TCR genes and therefore belongs to a true non-B, non-T lineage; third, the pathogenesis of HD is completely different from that of non-Hodgkin's lymphomas (NHL) and does not involve the clonal expansion of a cell frozen at a particular maturative stage as is thought to happen in most NHL.

DNA Nucleotidylexotransferase↗
PubMedDate not supplied

Long-term exposure to "low levels" of manganese oxides and neurofunctional changes in ferroalloy workers.

Occupational exposure to manganese can cause early neurobehavioral effects in low- or a-symptomatic workers. A battery of neuropsychological tests was administered to a group of 61 ferroalloy male workers and 87 controls. The average (geometric mean) manganese concentrations in total dust at the plant have changed from 1981 to 1997 respectively from 1597.03 micrograms/m3 to 239 micrograms/m3 at the furnace area; from 151.53 to 255.76 micrograms/m3 at the casting area; from 167 to 54.7 micrograms/m3 at the maintenance (welding operations), yielding a current overall value of 54.25 micrograms/m3. A cumulative exposure index was calculated for each alloy worker and the average value (geometric mean) resulted to be 1204.87 micrograms/m3 x years, which divided by the average length of exposure (15.17 years), showed the concentration of 70.83 micrograms/m3 of manganese in total dust. Blood and urinary manganese geometric means resulted significantly higher in the exposed workers (9.18 micrograms/l and 1.53 micrograms/g creatinine, respectively) than in controls (5.74 micrograms/l and 0.40 microgram/g creatinine, respectively). A positive correlation was observed between the airborne manganese concentrations in total dust and blood manganese (n = 55; R = 0.36; R2 = 0.13; p = 0.0068), whereas no association resulted between cumulative exposure index and both blood manganese and urinary manganese. Higher prevalence of symptoms reporting was observed in the alloy workers concerning irritability, loss of equilibrium and rigidity. Tremor parameters including the central frequency and its dispersion, resulted to be statistically different in the exposed workers compared to the controls. Motor functions exploring the coordination of rapid and alternating movements and memory functions resulted to be impaired in the manganese workers. Dose-effect relationships were observed between the cumulative exposure index and some of the test results, whereas no relationship was found with the airborne manganese concentrations and the biological indicators of exposure. These findings are consistent with the existing knowledge of a cumulative mechanism of action of manganese, which must be carefully considered when setting safe exposure levels. In order to be protective for the entire working life, the average annual exposure level should be lower than 100 micrograms/m3.

Adult↗
PubMedDate not supplied

[Prevalence of carpal tunnel syndrome in workers executing complex tasks with the upper extremities].

In 50 female workers of a manufacturing plant employed on the assembly line of metal and plastic products with cloth covering, we found a high prevalence of Carpal Tunnel Syndrome (16 cases, 32%, 5 of whom had already undergone surgical treatment). The subjects with positive diagnosis of Carpal Tunnel Syndrome also had a longer occupational exposure to repetitive movements, compared to the other subjects. Among the subjects with this disorder, the length of exposure was also significantly associated with the reported symptoms and the extension threshold measured on the 2nd finger of the dominant hand. Ergonomic assessment of the assembly lines revealed high-frequency repetitive movements and application of force, with insufficient rest intervals.

Adult↗
PubMedDate not supplied

[Medical surveillance and occupational identification of workers exposed to repeated movements of the upper limbs].

Repetitive motions of the upper limb at work can induce muskulo-skeletal alterations, therefore a specific medical surveillance is needed, according to the intensity of risk. In low risk conditions, the medical surveillance is aimed at the identification of hyper-susceptible individuals and the administration of specific information programs. When the risk intensity is higher, medical surveillance should add the recognition of early symptoms and signs of muskulo-skeletal disturbances, in order to remove workers showing early alterations from the exposure and allow medical rehabilitation. The diagnostic protocols with the adequate instrumental evaluation are provided, and the required legal reporting is discussed.

Arm↗