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Biomedical subjects

B Guerra

Publications and source records attributed to B Guerra.

At least 73 records · Page 4Linked to original sources
PubMed1996

The spleen protein-tyrosine kinase TPK-IIB is highly similar to the catalytic domain of p72syk.

TPK-IIB is a protein kinase that is predominant in the cytosol of spleen and is characterized by a high specific activity toward acidic peptide substrates and a low auto-phosphorylation activity. A prominent 52-kDa component purifies with the kinase [Marin, O., Donella-Deana, A., Brunati, A. M., Fischer, S. & Pinna, L. A. (1991) J. Biol. Chem. 266, 17798-17803]. Here we demonstrate that the 52-kDa protein displays sequence identity with the Miller-Dieker lissencephaly protein (LIS 1). The protein is not related to any known protein kinase and lacks an ATP-binding motif. The ATP binding and phosphotransferase activities of TPK-IIB can be fully accounted for by a minor 38-kDa protein band (p38/TPK-IIB) which can be separated from the 52-kDa protein by Mono-Q/FPLC in the presence of EDTA. Sequence analysis of p38/TPK-IIB reveals a high level of similarity, if not identity, with the catalytic domain of p72syk, a protein-tyrosine kinase implicated in the activation of hematopoietic cells. Antibodies raised against the catalytic domain of p72syk, but not antibodies raised against its N-terminal segment, cross-react with p38/TPK-IIB. The peptide substrate specificity of p72syk is almost identical to that of p38/TPK-IIB, which also supports the classification of TPK-IIB as a close relative (possibly a proteolytic or alternative spliced form) of p72syk. p38/TPK-IIB, however, exhibits a specific activity which is sixfold higher than that of p72syk and appears to be 50-fold more sensitive to inhibition by heparin. Thus, the observation that Ca(2+)-dependent degradation of p72syk by particulate fraction of rat spleen is accompanied by increased catalytic activity and increased sensitivity to heparin would be consistent with the possibility that hyperactive p38/TPK-IIB might be proteolytically generated from p72syk in response to an increase of intracellular Ca2+.

Affinity Labels↗
PubMed1996

Microcolposcopic topographic endocervical assessment before excisional treatment of cervical intraepithelial neoplasia.

OBJECTIVE: To evaluate whether microcolposcopic topographic endocervical assessment reduces the failures of excisional treatment of cervical intraepithelial neoplasia (CIN). METHODS: Three hundred fifty patients with colposcopic and histopathologic findings of endocervical CIN were recruited for excisional treatment. Three hundred forty-eight of these were randomized to have or not have microcolposcopy before excisional treatment. Measurement of endocervical lesion was the only aim of microcolposcopic evaluation. When an endocervical extension was available, the cone biopsy was cut according to microcolposcopic measurement. Excision status was evaluated and related to presurgical management on operative specimens. After excision, patients were followed-up for at least 5 years after treatment. Three hundred thirty (171 and 159 with and without preoperative microcolposcopy, respectively) patients completed the study. Disease persistences were defined by cytologic, colposcopic, and histologic results. Microcolposcopic value was defined as completeness of excision and/or lack of persistent disease. RESULTS. On surgical specimens, involved margins were detected in 19 (5.4%) cases. Presurgical microcolposcopy was performed in only one of these cases. The difference of incomplete excision between cases with or without microcolposcopy was statistically significant (P < .001). In patients who were followed-up, persistent disease was detected in one (0.6%) woman in the microcolposcopy group and in 16 (10%) women in the control group. Comparison between the two groups showed a significantly lower risk of persistent disease when presurgical microcolposcopy was performed (P < .001). CONCLUSION: By measuring endocervical extension of the lesion, preoperative microcolposcopy allows individualized cones, thus improving the prognosis after excisional treatment of CIN.

Adolescent↗
PubMed1995

Different susceptibility of protein kinases to staurosporine inhibition. Kinetic studies and molecular bases for the resistance of protein kinase CK2.

A systematic analysis reveals that out of 20 protein kinases examined, specific for either Ser/Thr or Tyr, the majority are extremely sensitive to staurosporine, with IC50 values in the low nanomolar range. A few of them however, notably protein kinases CK1 and CK2, mitogen-activated protein (MAP) kinase and protein-tyrosine kinase CSK, are relatively refractory to staurosporine inhibition, exhibiting IC50 values in the micromolar range. With all protein kinases tested, namely PKA, CK1, CK2, MAP kinase (ERK-1), c-Fgr, Lyn, CSK and TPK-IIB/p38Syk, staurosporine inhibition was competitive with respect to ATP, regardless of its inhibitory power. In contrast, either uncompetitive or noncompetitive kinetics of inhibition with respect to the phosphoacceptor substrate were exhibited by Ser/Thr and Tyr-specific protein kinases, respectively, consistent with a different mechanism of catalysis by these two sub-families of kinases. Computer modeling based on PKA crystal structure in conjunction with sequence analysis suggest that the low sensitivity to staurosporine of CK2 may be accounted for by the bulky nature of three residues, Val66, Phe113 and Ile174 which are homologous to PKA Ala70, Met120 and Thr183, respectively. In contrast these PKA residues are either conserved or replaced by smaller ones in protein kinases highly sensitive to staurosporine inhibition. On the other hand, His160 which is homologous to PKA Glu170, appears to be responsible for the unique behaviour of CK2 with respect to a staurosporine derivative (CGP44171A) bearing a negatively charged benzoyl substituent: while CGP44171A is 10- 100-fold less effective than staurosporine against PKA and most of the other protein kinases tested, it is actually more effective than staurosporine for CK2 inhibition, but it looses part of its efficacy if it is tested on a CK2 mutant (H160D) in which His160 has been replaced by Asp. It can be concluded from these data that the catalytic sites of protein kinases are divergent enough as to allow a competitive inhibitor like staurosporine to be fairly selective, a feature that can be enhanced by suitable modifications designed based on the structure of the catalytic site of the kinase.

Alkaloids↗
PubMed1995

Hierarchical phosphorylation of a 50-kDa protein by protein tyrosine kinases TPK-IIB and C-Fgr, and its identification as HS1 hematopoietic-lineage cell-specific protein.

TPK-IIB is an acidophilic protein tyrosine kinase devoid of autophosphorylation activity and unrelated to the Src family kinases [Marin, O., Donella-Deana, A., Brunati, A.M., Fischer, S. & Pinna, L. A. (1991) J. Biol. Chem. 266, 17798-17803]. Here, we describe the purification to homogeneity of a 50-kDa prominent substrate (p50) of TPK-IIB from rat spleen homogenates. Microsequence analysis of fragments from purified p50 discloses its homology to HS1, a hematopoietic-lineage cell-specific protein implicated in B-cell-antigen receptor-mediated signalling [Yamanashi, Y., Okada, M., Semba, T., Yamori, T., Umemori, H., Tsunasawa, S., Toyoshima, K., Kitamura, D., Watanabe, T. & Yamamoto, T. (1993) Proc. Natl Acad. Sci. USA 90, 3631-3635]. p50 is an excellent substrate for TPK-IIB, exhibiting very favourable kinetic constants (Km = 0.07 microM, kcat = 1.5) and incorporating up to 4 mol P/mol protein. p50 is, however, a weak substrate for the Src-related protein kinases Lyn and c-Fgr. Once phosphorylated by TPK-IIB, however, p50 is converted into a good substrate for c-Fgr and, to a lesser extent, for Lyn. p50 phosphorylated by TPK-IIB associates with c-Fgr and Lyn, as judged by co-immunoprecipitation with anti-Fgr IgG and anti-Lyn IgG, respectively. These data suggest the involvement of TPK-IIB in B-cell-antigen receptor-mediated signalling, and support the idea that phosphorylation by TPK-IIB might be a prerequisite for the recruitment of certain protein substrates by Src-related protein tyrosine kinases.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Mapping the residues of protein kinase CK2 implicated in substrate recognition: mutagenesis of conserved basic residues in the alpha-subunit.

Six mutants of protein kinase CK2 alpha subunit in which basic residues have been mutated into alanines were assayed for their capability to phosphorylate the peptide RRRADDSDDDDD. Two mutants (R228A and R278K279R280A) behaved more or less as alpha wild type and one (H160,166A) was nearly inactive, hampering the calculation of kinetic parameters. In contrast 3 mutants (K74-77A, K79R80K83A and R191,195K198A) phosphorylated the peptide with reduced efficiency accounted for by increased Km and decreased Vmax values. By using derivatives of the RRRADDSDDDDD peptide in which individual aspartyl residues were variably replaced by alanine(s) and two peptide substrates derived from I-2 (KYRIREQESSGEEDSDL and RRKDLHDDEEDEEMSETADGE) it was shown that mutations in the 191-198, 74-77 and 79-83 regions were the least detrimental whenever the acidic determinants were lacking at positions +1, +4/+5 and +3, respectively. These data support the conclusion that the basic residues present in the p+1 loop of CK2 alpha specifically recognize the acidic determinant adjacent to the C-terminal side of serine, while the specificity determinants located more down-stream are variably recognized by different residues of the unique basic cluster spanning between Lys74 and Lys83.

Amino Acid Sequence↗
PubMed1995

Presurgical assessment and therapy of microinvasive carcinoma of the cervix.

Retrievable pathological specimens and clinical data on 70 patients with microinvasive carcinoma diagnosed on surgical specimens from cone biopsy or hysterectomy (Stage IA) were reviewed and compared to pertinent findings in the literature with the intent of evaluating diagnostic criteria and defining pathological features that may influence the outcome by therapy. Emphasis was given to the preoperative assessment emphasizing that both an accurate colposcopic evaluation and a detailed pathological analysis may reliably point to a conservative therapeutic approach. Increasing depth of stromal invasion was associated with lesion width as well as with endocervical extension, as measured on colposcopy, microcolpohisteroscopy, and histology. Lymph-vascular space involvement was significantly related to depth of invasion. Two patients of 28 with dissected nodes had node metastases as well as lymph-vascular space involvement. Both developed a pelvic recurrence. One had a > 1- to < or = 3-mm invasion depth, the other a > 3- to < or = 5-mm lesion invasion. While advocating a conservative procedure for Stage IA1, we suggest discrimination with regard to Stage IA2 because we believe that lymph-vascular involvement should be meticulously evaluated. In fact, > 1- to < or = 3-mm lesions without lymph-vascular space involvement can be conservatively treated, while for any other lesion falling within the Stage IA2 category a modified radical histerectomy plus pelvic lymphadenectomy should be recommended.

Adult↗
PubMed1995

The incidence of complications after caesarean section in 156 HIV-positive women.

OBJECTIVE: To investigate the risks of post-operative complications in HIV-positive mothers who undergo a caesarean section (CS) because the delivery cannot be safely accomplished by the vaginal route or to protect the infant from viral infection. DESIGN: In a multicentre study, we reviewed the incidence and type of post-operative complications in 156 HIV-positive women who underwent a CS. These results were compared with those observed in an equal number of HIV-uninfected women who matched for the indication requiring a caesarean delivery, the stage of labour, the integrity or rupture of membranes, and the use of antibiotic prophylaxis. SETTING: Seven teaching hospitals providing obstetrical care for mothers infected with HIV. RESULTS: We found that six HIV-infected mothers suffered a major complication (two cases of pneumonia, one pleural effusion, two severe anaemia and one sepsis) compared with only one HIV-negative woman who required blood transfusion after surgery. Minor complications like post-operative fever, endometritis, wound and urinary tract infections were significantly more frequent in HIV-positive women than controls. Multivariate analysis revealed that in HIV-infected women the only factor associated with a significant increase in the rate of complications was a CD4 lymphocyte count < 200 x 10(6)/l. CONCLUSIONS: The results of our study indicate that HIV-positive mothers are at an increased risk of post-operative complications when delivered by CS. The risk of post-operative complications is higher in HIV-infected women who are severely immunodepressed.

CD4 Lymphocyte Count↗
PubMed1994

Psoralen-fatty acid cycloadducts activate protein kinase C (PKC) in human platelets.

The C4-photocycloadduct psoralen-linolenic acid activates protein kinase C (PKC), in human platelets, which in turn phosphorylates 47 kDa protein, representing its major substrate in these cells. This behaviour is similar to that shown by diacylglycerol, a main second messenger responsible of various biological effects, e.g. of melanogenesis.

Aspirin↗
PubMed1994

The middle hepatitis B virus envelope protein is not necessary for infectivity of hepatitis delta virus.

The hepatitis delta virus (HDV) envelope contains the large (L), middle (M), and small (S) surface proteins encoded by coinfecting hepatitis B virus. Although HDV-like particles can be assembled with only the S protein in the envelope, the L protein is essential for infectivity in vitro (C. Sureau, B. Guerra, and R. Lanford, J. Virol. 67:366-372, 1993). Here, we demonstrate that the M protein, previously described as carrying a site for binding to polymerized human albumin, is not necessary for infectivity. HDV-like particles coated with the S plus L or the S plus M plus L proteins are infectious in primary cultures of chimpanzee hepatocytes. We conclude that the S and L proteins serve two essential functions in the HDV replication cycle; the S protein ensures the export of the HDV genome from an infected cell by forming a particle, and the L protein ensures its import into a human hepatocyte.

Animals↗
PubMed1994

[Discrepancy between histopathological diagnosis based on guided biopsy and cone biopsy of the cervix uteri: analysis of 346 cases of laser conization].

The conservative management of cervical intraepithelial neoplasia (CIN) essentially depended on the introduction and improvement of colposcopy. This technique, allowing to locate the lesion, to estimate its extension and to perform multiple punch biopsies, becomes discriminant in therapeutic choice. Whether colposcopy reveals endocervical involvement or abnormal transformation zone (ANTZ) may be only partially explored, excisional conization should be preferred to ablative therapy since the former advantageously can verify histopathologic diagnosis, confirm completely excision of lesion and rule out invasive carcinoma. The literature shows that cases of invasive lesions can be underestimated and therefore inadequately treated by ablative therapy, emphasizing colposcopy and punch biopsy limitations about suspect and diagnosis of microinvasion. We analyzed data concerning preliminary diagnostic investigations and results of 346 CO2 laser excisional conizations performed between 1984 and 1993. Histopathologic diagnosis on punch biopsy, performed in 111 cases of ANTZ1 and in 235 cases of ANTZ2, shows an agreement with cone biopsy in 30.8% of the cases of CIN1, of 40.9% in cases of CIN2 and of 66.3% in cases of CIN3. Whereas the lesion is overestimated in 30.6% of cases, in which it is likely that punch biopsy has removed the epicenter of the lesion or the lesion in toto, we had an underestimation in 15% of cases, particularly in 4 cases of CIN2, in 38 cases of CIN3 and in all microinvasive processes. The rate of invasive lesions previously ignored and detected only by histopathologic diagnosis on cone biopsy is 2.9%. In only one of these cases colposcopy, even if attributing to each of these the higher grading, shows the suspicion of invasion, whereas the detection of invasive processes is missed in every case by punch biopsy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Symptomatic parvovirus B19 infection of one fetus in a twin pregnancy.

Twin pregnancies complicated by infection due to parvovirus B19 are uncommon. We report a case in which only one fetus developed a symptomatic infection, which presented at first as ascites and pleural effusion; later, meconium peritonitis developed. Hydrops spontaneously resolved, and at birth meconium peritonitis was successfully treated with surgery. However, even with the positive outcome of this pregnancy, a long-term follow-up is needed to exclude damage other than injury to the erythropoietic system.

Adult↗
PubMed1993

Role of the large hepatitis B virus envelope protein in infectivity of the hepatitis delta virion.

The hepatitis delta virus (HDV) is coated with large (L), middle (M), and small (S) envelope proteins encoded by coinfecting hepatitis B virus (HBV). To study the role of the HBV envelope proteins in the assembly and infectivity of HDV, we produced three types of recombinant particles in Huh7 cells by transfection with HBV DNA and HDV cDNA: (i) particles with an envelope containing the S HBV envelope protein only, (ii) particles with an envelope containing S and M proteins, and (iii) particles with an envelope containing S, M, and L proteins. Although the resulting S-, SM-, and SML-HDV particles contained both hepatitis delta antigen and HDV RNA, only particles coated with all three envelope proteins (SML) showed evidence of infectivity in an in vitro culture system susceptible to HDV infection. We concluded that the L HBV envelope protein, and more specifically the pre-S1 domain, is important for infectivity of HDV particles and that the M protein, which has been reported to bear a site for binding to polymerized albumin in the pre-S2 domain, is not sufficient for infectivity. Our data also show that the helper HBV is not required for initiation of HDV infection. The mechanism by which the L protein may affect HDV infectivity is discussed herein.

Animals↗
PubMed1992

Vertical transmission of human immunodeficiency virus type 1. Prognostic value of IgA antibody to HIV-1 polypeptides during pregnancy.

In a retrospective study of 31 pregnant women infected with human immunodeficiency virus type 1 (HIV-1), nine (29%) infants presented unequivocal signs of HIV-1 infection (persistent p24 antigenemia and/or positive virus isolation). All serum samples obtained from the others, during pregnancy and on delivery, were studied for specific antibody (IgA) production by immunoblotting analysis to establish a possible link between the presence of a defined antibody class and mother-to-child viral transmission. The majority (16 of 22) of HIV-1-seropositive mothers who delivered uninfected children showed IgA antibody to low-molecular-weight HIV-1 polypeptides during pregnancy. Among those who delivered infected babies, only one showed a weak IgA reactivity to HIV-1 during pregnancy. Thus, our results suggest that immunoblotting study of IgA may be a diagnostic adjunct to predict the risk of mother-to-child HIV-1 transmission.

Child, Preschool↗
PubMed1981

Cytological and histopathological abnormalities of the cervix in genital Chlamydia trachomatis infections.

Since genital infection with Chlamydia trachomatis may be associated with cervical abnormalities 160 patients with grandular ectopia attending a gynaecological outpatient clinic were examined for antibodies against C trachomatis, the presence of C trachomatis infection, and cytological and histopathological abnormalities of the cervix.A significantly higher incidence of histological dysplasia was found in women with glandular ectopia who had antichlamydial antibodies than in those without.

Adult↗