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A Lamberti

Publications and source records attributed to A Lamberti.

At least 55 records · Page 3Linked to original sources
PubMed1992

Activation of the Rhizobium leguminosarum glnII gene by NtrC is dependent on upstream DNA sequences.

The cloning and sequence determination is reported of the DNA region of Rhizobium leguminosarum coding for glutamine synthetase II (GSII). An open reading frame (ORF) encoding 326 amino acids was defined as the glnII gene on the basis of its similarity to other glnII genes and the ability of a DNA fragment carrying this ORF to complement the glutamine auxotrophy of a Klebsiella pneumoniae glnA mutant. We find that the glnII gene in R. leguminosarum is transcribed as a monocistronic unit from a single promoter, which shows structural features characteristic of rpoN (ntrA)-dependent promoters. In K. pneumoniae, such promoters require the ntrC and rpoN (ntrA) gene products for transcription. The intracellular level of glnII mRNA changes when R. leguminosarum is grown on different nitrogen sources, as expected for regulation by the nitrogen regulatory system. Promoter deletion analysis has shown that an extensive upstream DNA sequence (316 bp) is essential for in vivo activation of the glnII promoter in different biovars of R. leguminosarum. This DNA region requires a wild-type ntrC gene for activity and includes two conserved putative NtrC-binding site sequences. The results conclusively show that transcription from the R. leguminosarum glnII promoter is fully dependent on positive control by NtrC protein and on an upstream activator sequence (UAS).

Amino Acid Sequence↗
PubMed1992

Phenotype of a Rhizobium leguminosarum ntrC mutant.

A Tn5 insertion mutant, strain CFN2012, of Rhizobium leguminosarum biovar phaseoli devoid of glutamine synthetase II (GSII) activity was analysed. It was shown to contain Tn5 within an 11-kb BamHI DNA fragment, which was isolated (pSM261) from the wild-type strain and, when introduced into strain CFN2012, was shown to complement the absence of GSII activity. The DNA sequence of the corresponding region from the wild-type allele revealed the presence of an ntrC regulatory gene, and restriction analysis indicated that the mutant allele carried the Tn5 insertion within it. Further analysis of strain CFN2012 indicated that this mutant has reduced levels of the PII regulatory protein and that, in contrast to ntrC mutants of other Rhizobiaceae, it grows on nitrate as the sole nitrogen source.

Bacterial Proteins↗
PubMed1992

UN-1, a murine monoclonal antibody recognizing a human thymocyte undescribed antigen.

A monoclonal antibody (MoAb), UN-1, specific for a human thymocyte cell surface antigen was produced. The same MoAb recognized in immunofluorescence also cells of the human T line HPB-ALL, while did not bind human peripheral blood cells and cells of some T, B and myeloid lines. Western blotting analysis of thymocyte membranes with MoAb UN-1 revealed a structure with a molecular weight of 150 kDa. Therefore both the pattern of expression and the size of the antigen recognized by MoAb UN-1 did not correspond to any previously described cell surface molecule.

Animals↗
PubMed1992

Dissociation by NH4Cl treatment of the enzymic activities of glutamine synthetase II from Rhizobium leguminosarum biovar viceae.

Glutamine synthetase II (GSII) was purified to homogeneity from Rhizobium leguminosarum biovar viceae and characterized. The sequence of 26 amino acid residues from the amino-terminal end of the protein showed high similarity with the sequence of GSII from Bradyrhizobium japonicum or from Rhizobium meliloti. Non-denaturing PAGE showed that GSII, either in crude extracts or in the pure state, was a mixture of an octamer and a tetramer and that under specific conditions the octamer/tetramer ratio could be modified in either direction. The pure enzyme was used to raise an antiserum which was highly specific. Addition of NH4Cl to a bacterial culture derepressed for GSII caused a specific decrease in transferase activity, faster than the one observed when the amount of immunoreactive material was measured by different methods. On the other hand, biosynthetic activity, measured as the rate of ADP or glutamine formation, paralleled the rate of decrease in immunoreactive material. A partially purified enzyme preparation retained this dissociation of kinetic parameters, strongly suggesting a post-translational modification. These findings are discussed with respect to the possible role of GSII in the Rhizobium-legume symbiosis.

Amino Acid Sequence↗
PubMed1991

T-cell malignancies with mature phenotypes: altered cell cycle regulation by HLA class I molecules.

Soluble anti-HLA class I monoclonal antibodies (MoAbs) modulate normal T-lymphocyte proliferation induced via the CD3/Ti and the CD2 pathway, but do not induce proliferation of normal T lymphocytes in the absence of additional mitogenic stimuli. In this report, we show that anti-HLA class I MoAbs induce DNA synthesis in peripheral blood mononuclear cells from a patient with a CD4+CD8+T-prolymphocytic leukemia (T-PLL) and from a patient with a CD4-CD8+ T-chronic lymphocytic leukemia (T-CLL), in the absence of detectable additional mitogenic stimuli. Proliferation of leukemic T cells is induced by both whole Igs and Fab' fragments of anti-HLA class I MoAbs, arguing in favor of their direct interactions with the proliferating cells as the mechanism underlying the mitogenic effect. This interpretation is also supported by the ability of anti-HLA class I MoAbs to induce proliferation of leukemic T-cell preparations, depleted of accessory cells. DNA synthesis in T-CLL and T-PLL cells is preceded by expression of G1-specific messenger RNAs, ie. c-myc, 2F1, Tac, and interferon-gamma, in activated cells. Cell proliferation is inhibited by the protein kinase C inhibitor H7, indicating that activation of this enzyme is required for the mitogenic effect of anti-HLA class I MoAbs. The latter inhibit the proliferation of T-CLL cells as well as that of normal T cells stimulated with anti-CD3 MoAbs and enhance that of both types of cells stimulated with anti-CD2 MoAbs. In addition, anti-HLA class I MoAb Q6/64 in combination with anti-CD2 MoAb 9.6 or MoAb 9-1 induces proliferation of leukemic T cells to a greater extent than the individual MoAbs, but is not mitogenic for normal T cells. Anti-HLA class I MoAbs restore the cytolytic activity of T-CLL cells that is lost after 5 days of incubation of control medium, suggesting that HLA class I antigens may mediate a signal contributing to the activation state. The present results indicate that leukemic T-cell proliferation can be triggered via HLA class I molecules and suggest a potential role for these antigens in the in vivo growth of malignant clones.

Antibodies, Monoclonal↗
PubMed1991

Identification and characterization of a T cell growth inhibitory factor produced by K562 erythromyeloid cells.

Cells of the human erythroleukemia cell line K562 constitutively secrete a factor that inhibits human T lymphocyte proliferation induced via CD3/Ti. The factor, termed K-TIF (K562-derived T cell inhibitory factor) is produced in either the presence or absence of fetal calf serum in cultures of K562 cells and can be precipitated by 70% NH4SO4. Gel filtration chromatography on Superose 12 resin by FPLC showed that the inhibitory factor has a molecular weight of approximately 30-35 kDa. A protein of this size, metabolically labeled with [35S]methionine, specifically bound human peripheral blood mononuclear cells. Chromatofocusing with Mono P by FPLC (pH gradient 7.2-5) indicates that the inhibitory factor has an isoelectric point of 6.0-6.4.

Humans↗
PubMed1991

Intra-operative transoesophageal echocardiography after mitral repair--specific conditions and pitfalls.

The aim of this study was to determine the specific conditions and pitfalls of immediate assessment of the reconstructed mitral valve in open chest patients. Sixty-two patients had a mitral reconstruction controlled by transoesophageal echocardiography and colour Doppler (TEE) from the moment when cardiac activity restarted under extracorporeal circulation (ECC), until complete rewarming of the patient and weaning off the by-pass. The following conditions altered the imaging quality: (1) dried probe in the oesophagus or air bubbles, (2) non-aspirated air from the stomach, (3) small or empty left atria, (4) invagination of the left atrial appendage, (5) trapped air in the posterior pericardium, (6) spontaneous contrast. Transient mitral regurgitation disappeared completely in 12/62 patients: five had temporary impairment of LV function, two had reduced filling of the heart, one had left ventricular outflow obstruction exacerbated by isoproterenol and nitroglycerin, two had ventricular ectopic rhythms, and two epicardial pacing. Only one of the 62 patients had persistent significant MR which required a second run of ECC. We conclude that mitral regurgitation after mitral valve repair is closely related to the quality of LV function. A decision to reoperate should eliminate the possible pitfalls, and take into consideration the specific conditions of immediate postoperative cardiac function.

Echocardiography, Doppler↗
PubMed1991

[Interrupted aortic arch. A series of 15 patients].

Between 1983 and 1989, 15 children underwent surgical repair of interrupted aortic arch at 1 to 20 days of age. The anatomical form was a Celoria and Patton type B in all patients with an associated perimembranous ventricular septal defect in all but one who had multiple ventricular septal defects, and patent ductus arteriosus. Six children had a retro-esophageal right subclavian artery, two had subaortic stenosis and two had a right-sided descending thoracic aorta. In two children with severe hypoplasia of the ascending aorta the repair was performed in one stage with two deaths due to left ventricular failure. In the other B cases, a two-stage repair was carried out. The reconstruction of the aortic arch varied according to the individual case. All children had pulmonary artery banding. Seven children survived longer than 30 days. Six of them later underwent a complete repair. The only survivors were those patients in whom the neo-aortic arch grew harmoniously. The authors conclude that: a two-stage repair gave disappointing results in this series of consecutive patients, mainly because of the poor quality of the reconstruction of the aortic arch by thoracotomy.

Anastomosis, Surgical↗
PubMed1990

Mitogenic activity of anti-CD28 MoAb CLB-CD28/1 on peripheral blood mononuclear cells and its cooperation with other anti-T cells MoAb in the activation of purified T lymphocytes.

Human T lymphocyte proliferative response induced via CD28 molecule is analyzed. An anti CD28 MoAb, CLB-CD28/1, induces the proliferation of human peripheral blood mononuclear cells in the absence of other stimuli, indicating that CD28 molecule can directly mediate a mitogenic signal in this system. The mitogenic activity of MoAb CLB-CD28/1 on PBMC does not require MoAb interaction with monocyte Fc receptors, since F(ab')2 fragments from the MoAb are mitogenic to the same extent as whole IgG. Nevertheless, the activity depends on the presence of accessory cells, since purified T lymphocytes require addition of irradiated monocytes and interleukin 2 to proliferate when incubated with MoAb CLB-CD28/1. On the other hand, MoAb CLB-CD28/1 induces response to IL-2 in thymocytes in the absence of accessory cells. Cooperation of MoAb CLB-CD28/1 with three other MoAbs, recognizing CD3, CD5 and HLA Class I antigens, respectively, induces Tac antigen expression and IL-2 responsiveness in purified T lymphocytes. This effect is obtained without cross-linking of the MoAb. It does not rely on a physical association between CD28 and CD3, CD5 or HLA Class I molecules, as demonstrated by co-modulation experiments. These data indicate that expression of IL-2 receptor on T lymphocytes can result from interaction of multiple activation pathways and that some of them, such as those mediated by CD5 and HLA Class I antigens, previously reported to serve as modulatory circuits, can instead act as essential elements in the onset of T lymphocyte proliferation.

Antibodies, Monoclonal↗
PubMed1989

Lack of a role of monocytes in the inhibition by monoclonal antibodies to monomorphic and polymorphic determinants of HLA class I antigens of PHA-P-induced peripheral blood mononuclear cell proliferation.

This study aimed at characterizing the mechanism(s) underlying the regulatory role of distinct determinants of HLA Class I antigens in PHA-P-induced T cell proliferation and the involvement of monocytes in this phenomenon. The anti-HLA-A2,A28 monoclonal antibodies (MoAb) CR11-351, the MoAb Q6/64 to a determinant restricted to the gene products of the I antigens HLA-B locus, and the MoAb CR10-215 and W6/32 to distinct monomorphic determinants of HLA Class I antigens were found to inhibit PHA-P-induced peripheral blood mononuclear cell (PBMC) proliferation in a dose-dependent fashion. The inhibition is specific and reflects neither inhibition of PHA-P binding to cells nor a toxic effect of the anti-HLA Class I MoAb. The latter differed in the concentration required to induce inhibition, in the influence of the concentration of PHA-P used as mitogen, in the differential effect on the donors used as a source of PBMC, and/or in the requirement of the Fc portion to induce inhibition. At variance with the information in the literature, the inhibitory effect of anti-HLA Class I MoAb on PHA-P-induced PBMC proliferation neither reflected their interaction with accessory cells nor was mediated by suppressor factors released by monocytes stimulated with PHA-P in the presence of anti-HLA Class I MoAb. Therefore, the regulatory role of HLA Class I antigens in T cell proliferation is not likely to be mediated by monocytes and/or factors released from them, but may reflect an involvement of these molecules in T cell activation pathways.

Antibodies, Monoclonal↗
PubMed1989

[Subaortic fibromuscular tunnel following resection of accessory mitral tissue. Surgical treatment].

When accessory mitral valve tissue obstructs the left ventricular outflow tract resection is considered a sufficient and definitive procedure. We report the unusual case of a child who had undergone such resection at the age of 4 years and who developed, over a few years, a recurrent subvalvular aortic obstacle consisting, this time, in a fibromuscular tunnel. In a second operation performed at the age of 12, a septal patch was inserted to widen the subaortic channel which was approached through a trans-septal infundibular route. Control examination showed a satisfactory pressure gradient and a sinus rhythm.

Child, Preschool↗
PubMed1989

Proliferative pathways in CD1- CD3+ CD4+ CD8+ T-prolymphocytic leukemic cells: analysis with monoclonal antibodies and cytokines.

The antigenic profile and the proliferative pathways in leukemic cells from the patient TRT with T-prolymphocytic leukemia (T-PLL) were analyzed using monoclonal antibodies (MoAbs) and cytokines. T-PLL cells expressed the phenotype CD1- CD3+ CD4+ CD8+. Incubation with the differentiating agent phorbol-12-myristate-13-acetate markedly increased the percentage of cells with the CD4- CD8+ phenotype, suggesting that leukemic cells were already committed towards a differentiated element with the CD4- CD8+ phenotype. T-PLL cells were induced to proliferate by anti-CD2 MoAb 9-1 + 9.6 and by anti-CD3 MoAb OKT3. The two pathways exhibited normal functional interactions and were susceptible to modulation by anti-HLA class I MoAbs. These results indicate that regulation of cell proliferation was preserved to a significant extent in the T-PLL cells analyzed. At variance with normal resting T cells that require previous activation to proliferate when incubated with interleukin-1 (IL-1) or interleukin-2 (IL-2), T-PLL cells proliferated vigorously when incubated with either interleukin. Furthermore, T-PLL cells proliferated when incubated with immune interferon (IFN-gamma). The latter finding parallels the enhancement by IFN-gamma of the proliferative response of lectin-activated murine T lymphocytes. These results suggest that T-PLL cells, which express a high constitutive level of c-myc mRNA, may be in an activated state. The antigenic phenotype and the characteristics of the proliferative pathways of T-PLL cells from the patient TRT are compatible with the possibility that they may be derived from an intermediate thymocyte.

Antibodies, Monoclonal↗
PubMed1987

Tight linkage of glnA and a putative regulatory gene in Rhizobium leguminosarum.

Rhizobium leguminosarum, biovar viceae, strain RCC1001 contains two glutamine synthetase activities, GSI and GSII. We report here the identification of glnA, the structural gene for GSI. A 2 kb fragment of DNA was shown to complement the Gln- phenotype of Klebsiella pneumoniae glnA mutant strains. DNA sequence analysis revealed an open reading frame (ORF) of 469 codons specifying a polypeptide of 52,040 daltons. Its deduced amino acid sequence was found to be highly homologous to other glutamine synthetase sequences. This ORF was expressed in Escherichia coli minicells and the corresponding polypeptide reacted with an antiserum raised against GSI. Upstream of glnA we found an ORF of 111 codons (ORF111) preceded by the consensus sequence for an ntrA-dependent promoter. Minicells experiments showed a protein band, with a molecular weight in good agreement with that (10,469) deduced from the nucleotide sequence. On the basis of homology studies we discuss the possibility that the product of ORF111 is equivalent to the PII protein of E. coli and plays a similar role in regulation of nitrogen metabolism.

DNA Restriction Enzymes↗
PubMed1986

Characterization and cloning of two Rhizobium leguminosarum genes coding for glutamine synthetase activities.

We have demonstrated that Rhizobium leguminosarum strain LPR1105 contains a heat stable and a heat labile glutamine synthetase (EC 6.3.1.2) activity similar to those described for other Rhizobiaceae. Most of the activity is heat stable when this strain is grown on glutamine as sole nitrogen source, but most is heat labile when grown on nitrate. Using a gene bank of R. leguminosarum DNA we have isolated two clones, which code for heat stable (p7D9) and heat labile (p4F7) glutamine synthetase activity, by complementing the glutamine auxotrophy of Klebsiella pneumoniae glnA mutants. Cross-hybridization of p7D9 with a fragment of the glnA gene of K. pneumoniae was observed, but no cross-hybridization between p7D9 and p4F7 was found. Since these two regions hybridize to genomic DNA of R. leguminosarum they are probably the structural genes for GSI and GSII, and the availability of these genes will make it possible to test this hypothesis. Clone p4F7 complements an ntrC+ but not an ntrC K. pneumoniae glnA mutant, suggesting that the ntrC gene is required for the complementation of the glutamine auxotrophy by this plasmid.

Cloning, Molecular↗
PubMed1986

[Repair of rheumatic mitral lesions by transfer of a segment of the posterior valve with its chordae onto the anterior valve].

Since 1981, 100 patients have undergone mitral valve repair alone or in association with aortic or tricuspid valve surgery. The basic technique used was that described by Carpentier. However, in 13 of these patients, the repair was performed by a technical innovation consisting in transferring a one to two centimetres segment of the posterior leaflet with its chordae to the anterior leaflet. The lesions in which this particular technique was required were extensive chordal rupture of the anterior leaflet (5 cases), localised retraction of the surface of the anterior leaflet (2 cases), and perforation near the valve free edge due to endocarditis (1 case). The valvular disease was due to rheumatic fever in all cases. None of the patients had active endocarditis. The age of the patients varied from 4 to 60 years. Eight patients were under 15 years of age. Postoperative echocardiography and pulsed Doppler studies showed results comparable to the other patients who had undergone mitral valve repair although the valvular lesions were more severe in this particular group of patients. Only one patient had a poor operative result and had to be reoperated.

Adolescent↗
PubMed1985

Echocardiographic ventricular shape analysis in congenital heart disease with right ventricular volume or pressure overload.

In this 2-dimensional (2-D) echocardiographic study, a computerized Fourier analysis technique refined from one that allows quantification of changes in septal shapes in normal fetuses, newborns and infants allowed analysis of left ventricular (LV) shapes in 14 patients with right ventricular (RV) volume overload (atrial septal defects), 5 with volume and pressure overload (total anomalous pulmonary venous connection), and 10 with pressure overload (complete transposition of the great arteries [TGA] with intact ventricular septum). Diastolic shape factors in the 3 groups were significantly different from those of normal subjects (p less than 0.01). Highest diastolic values were found in patients with TGA (mean 4.59 +/- 1.28). Systolic shape factors were similar in patients with atrial septal defect and normal subjects. Significant differences existed between normal subjects and patients with total anomalous pulmonary venous connection, with the greatest differences in systolic shape factor being 5.61 for TGA vs 1.87 (p less than 0.005) for normal subjects. Shape factor correlated well with hemodynamic data for RV/LV systolic pressure ratios (r = 0.93, p less than 0.001) for normalized interventricular pressure differences (r = -0.95, p less than 0.001). The lower the normalized systolic pressure difference or the higher the RV/LV ratio, the more the septum encroached into the LV cavity. Significant but weaker correlations were noted for values during diastole. Quantitative application of Fourier shape factor analysis to LV shapes allows numerical expression of visually interpreted distortions over a wide range of geometric alterations.

Cardiac Volume↗