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Biomedical subjects

F Lonardo

Publications and source records attributed to F Lonardo.

At least 37 records · Page 2Linked to original sources
PubMed1993

Paternal mosaicism for a COL1A1 dominant mutation (alpha 1 Ser-415) causes recurrent osteogenesis imperfecta.

We describe a dominant point mutation in the COL1A1 gene causing extremely severe osteogenesis imperfecta (OI type II/III) which was detected in the dermal fibroblasts of a proband, diagnosed by ultrasonography at 24 weeks of gestation. Type I collagen secretion was reduced and pro alpha 1(I) chains were overmodified. The mutation was localised in one COL1A1 allele by chemical cleavage of mismatched bases in normal cDNA/proband's mRNA heteroduplexes, and identified by cloning and sequencing. A G-to-A transition which causes the substitution of Gly-415 with serine in the alpha 1(I) triple helical domain was found. The same mutation was detected in the father's spermatozoa and lymphocytes. Mosaicism in the father's germline explains the occurrence in the family of two additional OI pregnancies, which were documented by X-ray and ultrasound investigations.

Adult↗
PubMed1992

Right colon adenocarcinoma presenting as Bacteroides fragilis liver abscesses.

Pyogenic abscesses of the liver occur in association with a variety of diseases. Sometimes they are caused by anaerobic infections of liver metastases. Uncommonly, however, multiple hepatic abscesses caused by anaerobic bacteria are the presenting signs of unsuspected colonic cancer in the absence of liver metastases. We report a 60-year-old man who presented with febrile cholestatic liver disease initially thought to be metastases. Repeated ultrasound-directed liver biopsies yielded a diagnosis of multiple abscesses. Bacteroides fragilis was grown from the liver specimen and the patient responded well to metronidazole treatment. Two months later, however, overt symptoms of large bowel disease led to the diagnosis of colonic adenocarcinoma. After a 6-month postoperative follow-up, the patient is free of liver metastases. Anaerobic liver abscesses should always alert the clinician to possible silent colonic cancer.

Adenocarcinoma↗
PubMed1992

erbB-2 autophosphorylation is required for mitogenic action and high-affinity substrate coupling.

Autophosphorylation of gp185erbB-2 in vivo is confined to its carboxy terminus and is required for optimal erbB-2 transforming activity under conditions of receptor overexpression. It remains unresolved, however, to what extent autophosphorylation regulates erbB-2 mitogenic signaling in normal cells, nor is the biochemical basis for such a regulatory function known. To address these issues, we utilized a chimeric molecule encompassing the extracellular domain of the epidermal growth factor (EGF) receptor (EGFR) fused to the transmembrane and intracellular domains of the erbB-2 product. In this EGFR/erbB-2 chimera, erbB-2 kinase activity is regulated by EGF binding. An EGFR/erbB-2 mutant bearing multiple Tyr----Phe substitutions at erbB-2 autophosphorylation sites (EGFR/erbB-2 5P) displayed markedly reduced phosphotyrosine content following EGF stimulation in comparison with the non-mutated chimera. When expressed in NR6 cells, the EGFR/erbB-2 5P mutant was unable to deliver a sizeable mitogenic signal when activated by EGF at physiological levels. In intact cells, the 5P mutant was still able to stimulate phosphorylation of the gamma isozyme of phospholipase C (PLC-gamma), a prototype erbB-2 substrate, although with a delayed time course, indicating that the 5P mutation decreased the affinity of the erbB-2 kinase for this substrate. This conclusion was further supported by the inability of the 5P mutant to associate with PLC-gamma in co-immunoprecipitation experiments. We infer that a major role of autophosphorylation is to increase the affinity of the erbB-2 kinase for its cellular substrates, so that, under physiological conditions, autophosphorylation is absolutely required for erbB-2 mitogenic signaling.

Amino Acid Sequence↗
PubMed1991

The juxtamembrane regions of the epidermal growth factor receptor and gp185erbB-2 determine the specificity of signal transduction.

The epidermal growth factor receptor (EGFR) and gp185erbB-2 are closely related tyrosine kinases. Despite extensive sequence and structural homology, these two receptors display quantitative and qualitative differences in their ability to couple with mitogenic signalling pathways. By using chimeric molecules between EGFR and erbB-2, we found that the determinants responsible for the specificity of mitogenic signal transduction are located in the amino-terminal half of the tyrosine kinase domain of either receptor. In the EGFR, mutational analysis within this subdomain revealed that deletion of residues 660 to 667 impaired receptor mitogenic activity without affecting its tyrosine kinase properties. This sequence is therefore likely to contribute to the specificity of substrate recognition by the EGFR kinase.

Amino Acid Sequence↗
PubMed1991

Oncogenic potential of erbB-2 in human mammary epithelial cells.

Introduction of the normal erbB-2 gene into immortalized human mammary epithelial cells (184B5) by transfection conferred a growth advantage to these cells both in vitro and in vivo. The 184B5 cells overexpressing erbB-2 formed colonies in semi-solid medium, frequently induced transient nodules in athymic mice and produced progressive tumors in vivo at a low frequency. Those tumors which did arise from erbB-2-transfected cells displayed substantially higher levels of normal gp185erb-2 protein when compared to the original transfectants, consistent with their selection for increased erbB-2 expression. Introduction of genes encoding genetically altered erbB-2 molecules into 184B5 cells increased their colony-forming efficiency and converted the cells to a tumorigenic phenotype at a high frequency. When the biological and biochemical properties of human mammary carcinoma cell lines known to overexpress erbB-2 were compared to the transfected 184B5 lines, they behaved most like those overexpressing the normal erbB-2 protein. Results indicate that overexpression of normal erbB-2 may directly contribute to the transformation of human mammary epithelium if sufficient levels of erbB-2 protein are expressed or if the erbB-2 gene is genetically altered.

Animals↗
PubMed1990

The carboxy-terminal domains of erbB-2 and epidermal growth factor receptor exert different regulatory effects on intrinsic receptor tyrosine kinase function and transforming activity.

The erbB-2 gene product, gp185erbB-2, displays a potent transforming effect when overexpressed in NIH 3T3 cells. In addition, it possesses constitutively high levels of tyrosine kinase activity in the absence of exogenously added ligand. In this study, we demonstrate that its carboxy-terminal domain exerts an enhancing effect on erbB-2 kinase and transforming activities. A premature termination mutant of the erbB-2 protein, lacking the entire carboxy-terminal domain (erbB-2 delta 1050), showed a 40-fold reduction in transforming ability and a lowered in vivo kinase activity for intracellular substrates. When the carboxy-terminal domain of erbB-2 was substituted for its analogous region in the epidermal growth factor receptor (EGFR) (EGFR/erbB-2COOH chimera), it conferred erbB-2-like properties to the EGFR, including transforming ability in the absence of epidermal growth factor, elevated constitutive autokinase activity in vivo and in vitro, and constitutive ability to phosphorylate phospholipase C-gamma. Conversely, a chimeric erbB-2 molecule bearing an EGFR carboxy-terminal domain (erbB-2/EGFRCOOH chimera) showed reduced transforming and kinase activity with respect to the wild-type erbB-2 and was only slightly more efficient than the erbB-2 delta 1050 mutant. Thus, we conclude that the carboxy-terminal domains of erbB-2 and EGFR exert different regulatory effects on receptor kinase function and biological activity. The up regulation of gp185erbB-2 enzymatic activity exerted by its carboxy-terminal domain can explain, at least in part, its constitutive level of kinase activity.

Animals↗
PubMed1990

The role of autophosphorylation in modulation of erbB-2 transforming function.

The product of the erbB-2 gene is a 185-kD receptor-like glycoprotein. erbB-2 gp185 displays constitutive tyrosine kinase activity and transforms NIH 3T3 cells when expressed 100-fold over the normal levels. We have analyzed the role of tyrosine kinase function and of receptor autophosphorylation in the regulation of erbB-2 biological activity. Abolition of erbB-2 gp185 tyrosine kinase function resulted in complete loss of its transforming activity and the absence of in vivo tyrosine phosphorylation. The steady-state content of phosphotyrosine in erbB-2 gp185 was found to be solely dependent on receptor autophosphorylation and to be dependent on the specific enzymatic activity of the erbB-2 protein. The major sites of erbB-2 autophosphorylation were shown to be in its COOH-terminal domain. Biological analysis of erbB-2 mutants containing either individual or multiple Tyr----Phe substitutions at the potential sites of autophosphorylation revealed that autophosphorylation upregulates erbB-2 gp185 transforming activity. Autophosphorylation did not modulate receptor turnover. A Tyr----Phe substitution of erbB-2 Tyr-877 homologous to pp60c-src Tyr-416 did not alter erbB-2 biological and biochemical properties, thus excluding the possibility that phosphorylation of this residue, located in the kinase domain, modulates erbB-2 gp185 catalytic function. Hence, autophosphorylation of tyrosine residues localized in its COOH terminus appears to be required for optimal coupling of erbB-2 gp185 with its mitogenic pathway.

Animals↗
PubMed1990

The normal erbB-2 product is an atypical receptor-like tyrosine kinase with constitutive activity in the absence of ligand.

Overexpression of the erbB-2/neu gene is frequently detected in human cancers. When overexpressed in NIH 3T3 cells, the normal erbB-2 product, gp185erbB-2, displays potent transforming ability as well as constitutively elevated levels of tyrosine kinase activity in the absence of exogenously added ligand. To investigate the basis for its chronic activation we sought evidence of a ligand for gp185erbB-2 either in serum or produced by NIH 3T3 cells in an autocrine manner. We demonstrate that a putative ligand for gp185erbB-2 is not contained in serum. Chimeric molecules composed of the extracellular domain of gp185erbB-2 and the intracellular portion of the epidermal growth factor receptor (EGFR) did not show any transforming ability or constitutive autophosphorylation when they were expressed in NIH 3T3 cells. However, they were able to transduce a mitogenic signal when triggered by a monoclonal antibody directed against the extracellular domain of erbB-2. These results provide evidence against the idea that an erbB-2 ligand is produced by NIH 3T3 cells. Furthermore, we obtained direct evidence of the constitutive enzymative activity of gp185erbB-2 by demonstrating that the erbB-2 kinase remained active in a chimeric configuration with the extracellular domain of the EGFR, in the absence of any detectable ligand for the EGFR. Thus, under conditions of overexpression, the normal gp185erbB-2 is a constitutively active kinase able to transform NIH 3T3 cells in the absence of ligand.

Animals↗
PubMed1988

A malformed girl with a de novo proximal 6q deletion.

An additional case of interstitial deletion of chromosome 6, the first with breakpoints in q12 and q14, is reported. The female infant was the malformed first child of young, healthy parents. A review of proximal 6q deletions is made.

Abnormalities, Multiple↗
PubMed1987

Cytogenetic study of a cell line of human penile cancer.

A cell line of penile cancer from a 60-year-old Ugandan black patient has been studied by the authors. Transmission and scanning electron microscopy showed a large number of blebs and microvilli at cell surface; desmosomes were evident at TEM. Cytogenetic investigation (R-, C-, Nor-banding) showed the frequent presence of some markers: del(1p),del(1q),iso(3q),der(4),del(8p),11q+, t rob(13;14), 14p+, t rob(21;21). The epidemiology, geographical distribution, and aetiological role of human papilloma virus type 16 and herpes simplex type 2 are discussed.

Carcinoma, Squamous Cell↗
PubMed1986

Expression of the autosomal folate-sensitive fragile sites in ten kindreds with Martin-Bell syndrome.

The authors analyse the expression of all the folate-sensitive fra sites in a sample of 24 male patients with Martin-Bell syndrome (MBS) and their 12 mothers distributed in 10 kindreds. The cytogenetic results are compared with that of a control group, constituted by 8 unrelated normal subjects. Except for the fra Xq27, there was no autosomal folate-sensitive fra site significantly more expressed in patients with MBS than in the control group. On the basis of the present cytogenetic sample of about 6 500 R-banded mitoses, a list of all the in vitro folate-sensitive fra sites and their relative frequencies is given.

Chromosome Fragile Sites↗
PubMedDate not supplied

Prenatal diagnosis of Mohr syndrome by ultrasonography.

A case of prenatal diagnosis of Mohr syndrome is presented. The ultrasound examination was indicated by the previous birth of an affected brother. The need for genetic counselling is stressed, when polydactyly is observed accidentally at ultrasound examination during pregnancy.

Abnormalities, Multiple↗