Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “MALT”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed2004

Oligomeric assemblies of the Escherichia coli MalT transcriptional activator revealed by cryo-electron microscopy and image processing.

MalT, the dedicated transcriptional activator of the maltose regulon in Escherichia coli, is the prototype for a family of large (approximately 100 kDa) transcriptional activators. MalT self-association plays a key role in recognition of the target promoters, which contain several MalT sites that are cooperatively bound by the activator. The unliganded form of MalT is monomeric. The protein self-associates only in the presence of both ATP (or AMP-PNP, a non-hydrolysable analog of ATP) and maltotriose, the inducer. Here, we report cryo-electron microscopy analyses of MalT multimeric forms. We show that, in the presence of maltotriose and AMP-PNP, MalT associates into novel, polydisperse, curved homopolymers. The building block, corresponding to a MalT monomer, comprises an outer globular domain connected by a peduncle to an inner domain that mediates self-association. Image analyses highlight the significant conformational flexibility of these polymeric forms. In the presence of a DNA fragment containing a MalT-controlled promoter, malPp500, MalT forms homopolymers with a much smaller radius of curvature and a different conformation. We propose that MalT binding to the target promoters involves the assembly of a MalT homo-oligomer that is governed by the array of MalT sites present.

Cryoelectron Microscopy↗
PubMed1997

t(11;18)(q21;q21) is the most common translocation in MALT lymphomas.

BACKGROUND: Low grade malignant lymphomas arising from mucosa associated lymphoid tissue (MALT) represent a distinct clinicopathological entity. The cytogenetic findings and molecular genetics of MALT lymphomas remain minimally defined. Cytogenetic studies infrequently constitute part of the diagnostic work-up of MALT lymphomas, most commonly due to small biopsy size and their extranodal localization. Only 28 MALT cases with a clonal karyotype have been published to date. A number of chromosomal abnormalities have been observed with the majority of the cases featuring trisomy of chromosome 3 which is present in up to 78% of the cases. MATERIALS AND METHODS: A total of 116 cases of MALT lymphoma were diagnosed at BCCA between 1988 and 1997. Eleven cases of pathologically confirmed MALT lymphomas were subjected to cytogenetic analysis at the time of the initial evaluation. Eight of 11 cases yielded successful cultures and the presence of a clonal karyotype using standard cytogenetic methodology. In addition, a single case of orbital MALT lymphoma with a clonal karyotype has been obtained through our consultative practice from University of Nebraska Medical Center. These nine cases of MALT lymphoma with a clonal karyotype are the subject of this report. RESULTS AND CONCLUSION: In this study we report nine cytogenetically studied MALT lymphomas, three of which feature a novel t(11;18)(q21;q21) translocation which has also been observed in five other MALT cases described in the literature. This recurrent translocation is the most common translocation associated with MALT lymphomas being present in 33% (three of nine) of our cases and 18% (five of 28) of the previously published cases. The results suggest that a potentially important gene located at one of these breakpoints may be involved in the pathogenesis of MALT lymphomas.

Adult↗
PubMed1999

The role of Helicobacter pylori in primary gastric MALT lymphoma.

AIMS: Helicobacter pylori has been claimed to be an important aetiological factor which raises the risk of mucosa-associated tissue lymphoid (MALT) lymphoma. However, some studies on gastric MALT lymphoma revealed a low rate of H. pylori infection suggesting that not all gastric lymphomas are related to H. pylori infection. The aim of this study was to verify the H. pylori infection frequency in a series of patients with primary gastric MALT lymphomas and to examine the relationship between H. pylori and the pathological features of those lymphomas. METHODS AND RESULTS: Thirty-one cases of resected gastric lymphoma were analysed: 10 cases (32%) were low-grade MALT lymphomas and 21 cases (68%) were high-grade MALT lymphomas. Helicobacter pylori was found in only 18 of 31 (58%) cases. Helicobacter pylori infection was significantly correlated with the grade and depth of invasion of MALT lymphoma since 63% of superficial low-grade MALT lymphomas were positive for H. pylori compared with 38% of advanced high-grade MALT lymphomas (P = 0.02). CONCLUSION: We confirmed the relationship between H. pylori infection and a subset of gastric MALT lymphoma. Our results also showed that not all low- and high-grade gastric MALT lymphomas are H. pylori-dependent. This suggests that H. pylori infection may play a promoter role in the development of MALT lymphoma, but its presence is not mandatory for the progression of the lymphoma in view of its low frequency in advanced high-grade MALT lymphoma.

Adult↗
PubMed2000

Importance of extensive staging in patients with mucosa-associated lymphoid tissue (MALT)-type lymphoma.

Lymphoma of the mucosa-associated lymphoid tissue (MALT) type usually arises in MALT acquired through chronic antigenic stimulation triggered by persistent infection and/or autoimmune processes. Due to specific ligand-receptor interactions between lymphoid cells and high-endothelial venules of MALT, both normal and neoplastic lymphoid cells display a pronounced homing tendency to MALT throughout the body. In the case of neoplastic disease these homing properties may be responsible for lymphoma dissemination among various MALT-sites. According to this concept, we have standardized staging procedures in all patients diagnosed with MALT-type lymphoma. All patients with MALT-type lymphoma underwent standardized staging procedures before treatment. Staging included ophthalmologic examination, otolaryngologic investigation, gastroscopy with multiple biopsies, endosonography of the upper gastrointestinal tract, enteroclysis, colonoscopy, computed tomography of thorax and abdomen and bone marrow biopsy. Biopsy was performed in all lesions suggestive for lymphomatous involvement, and evaluation of all biopsy specimens was performed by a reference pathologist. 35 consecutive patients with histologically verified MALT-type lymphoma were admitted to our department. Twenty-four patients (68%) had primary involvement of the stomach, five (15%) had lymphoma of the ocular adnexa, three (8.5%) had lymphoma of the parotid, and three (8,5%) of the lung. Lymph-node involvement corresponding to stage EII disease was found in 13 patients (37%), only one patient with primary gastric lymphoma had local and supradiaphragmatic lymph-node involvement (stage EIII). Bone marrow biopsies were negative in all patients. Overall, eight of 35 patients (23%) had simultaneous biopsy-proven involvement of two MALT-sites: one patient each had lymphoma of parotid and lacrimal gland, conjunctiva and hypopharynx, conjunctiva and skin, lacrimal gland and lung, stomach and colon, and stomach and lung. The remaining two patients had bilateral parotideal lymphoma. Staging work-up was negative for lymph-node involvement in all of these eight patients. The importance of extensive staging in MALT-type lymphoma is emphasized by the demonstration of multiorgan involvement in almost a quarter of patients. In addition, our data suggest that extra-gastrointestinal MALT-type lymphoma more frequently occurs simultaneously at different anatomic sites than MALT-type lymphoma involving the GI-tract.

Eye Neoplasms↗
PubMed2001

Bcl10 expression, rearrangement and mutation in MALT lymphoma: correlation with expression of nuclear factor-kappaB.

Mucosa-associated lymphoid tissue (MALT) lymphomas usually involve extranodal sites, especially the stomach, lung and salivary glands. The Bcl10 gene was recently isolated from the breakpoint region of t(1;14) (p22;q32) in MALT lymphomas, and considered to be an apoptosis-associated gene, and involves a caspase recruitment domain (CARD)-containing protein that activates NF-kappaB. We investigated the role of Bcl10 in MALT lymphoma by analyzing its expression, rearrangement and somatic mutation, by immunostaining, reverse transcriptase-polymerase chain reaction (RT-PCR), Southern blot and PCR in 20 cases of MALT lymphoma. Expression of NF-kappaB was studied by immunostaining. Five cases of reactive lymphadenitis (RLA) were used as the control. Bcl10 rearrangement was detected in 8 of 20 (40%) MALT lymphomas, but in none of RLA. Significant Bcl10 mutation was detected only in 1 case (5%) with MALT, but not in RLA. RT-PCR showed higher density bands of Bcl10 in MALT lymphomas than in RLA. Immunostaining showed a weak Bcl10 expression in the germinal center and very weak expression in the marginal zone B-cells in RLA, which was limited to the cytoplasm. In contrast, Bcl10 was strongly expressed in MALT lymphomas, and was mainly detected in the cytoplasm, as well as in the nuclei. Bcl10 expression did not correlate with Bcl10 mutation and re-arrangements. NF-kappaB was expressed in nuclei of MALT lymphoma cells, but not in RLA. Bcl10 expression in MALT lymphoma correlated closely with NF-kappaB expression. Our results suggest that activation of Bcl10 and NF-kappaB may be important in MALT lymphomagenesis, and that nuclear localization of Bcl10 may be important in the progression of MALT.

Adaptor Proteins, Signal Transducing↗
PubMed2005

CXCR3-positive B cells found at elevated frequency in the peripheral blood of patients with MALT lymphoma are attracted by MIG and belong to the lymphoma clone.

Chemokine receptors mediate the migration of lymphocytes through binding of their ligands. CXCR3 is expressed in Th1 T cells; however, CXCR3 was recently reported in B-cell mucosa-associated lymphoid tissue (MALT)-type lymphoma and splenic marginal zone lymphoma. To investigate whether CXCR3-positive B lymphocytes in peripheral blood (PB) migrate to MALT and spleen, and whether the lymphoma clone is present in PB, we studied 16 cases of MALT lymphoma. In MALT cases, CXCR3-positive B lymphocytes in PB could migrate to MIG, the CXCR3 ligand. Immunohistochemical analysis showed that MALT lymphoma cells expressed CXCR3, whereas epithelial glands and/or stromal cells expressed MIG. In the PCR analysis for VH gene rearrangements, MALT lymphoma showed monoclonal or oligoclonal bands. In addition, in 8 of 16 MALT cases, the VH gene rearrangement of MALT lymphoma had the same bands as the CXCR3-positive B lymphocytes in PB. In 4 cases, the same clones of DNA sequences were confirmed in MALT lymphoma and CXCR3-positive B lymphocytes of PB. The findings support the theory that CXCR3-positive B lymphocytes in PB of MALT patients belong to the lymphoma clone and migrate to MIG-expressing mucosa-associated lymphoid tissue. It seemed to be associated with the dissemination of MALT lymphoma.

Adult↗
PubMed2001

Crystal structure of transcription factor MalT domain III: a novel helix repeat fold implicated in regulated oligomerization.

BACKGROUND: MalT from Escherichia coli, the best-studied member of the MalT family of ATP-dependent transcriptional activators, regulates the genes for malto-oligosaccharide utilization. The active form of this 4 domain protein is a homooligomer, and its multimerization is induced by the binding of maltotriose. Domains II and III of MalT were suggested to mediate the oligomerization process, but its molecular mechanism and the specific functions of these domains remain to be identified. RESULTS: We solved the crystal structure of MalT domain III at 1.45 A resolution by multiple isomorphous replacement phasing. The structure reveals eight copies of a two-helix bundle motif arranged in a novel, right-handed superhelix fold with closed walls, followed by a small C-terminal subdomain. The MalT superhelix contains a potential maltotriose binding site and forms a large hydrophobic protein-protein interaction interface that mediates the contact between two MalT domain III molecules. Structure-based analysis of the two-helix bundle motifs revealed a novel degenerated sequence pattern, and repeats of this pattern could be identified in other regulator proteins. CONCLUSIONS: MalT domain III contains a novel superhelix fold. Its protein-protein interaction interface, however, resembles protein binding sites of other superhelical proteins, suggesting a model with domain III mediating MalT oligomerization. Maltotriose seems to modulate the interaction interface and MalT oligomerization by occupying the ligand binding site inside the superhelix. Similar structural and mechanistic features in other MalT protein-family members and unrelated regulator proteins are indicated by the reappearance of a novel sequence motif derived from the MalT domain III structure.

Amino Acid Motifs↗
PubMed2000

A reassessment of primary thyroid lymphoma: high-grade MALT-type lymphoma as a distinct subtype of diffuse large B-cell lymphoma.

AIMS: Primary lymphoma of the thyroid gland (PTL) is a relatively rare disease. During an 18-year period, 53 cases of primary non-Hodgkin's lymphoma involving this extranodal site were seen at our institutions. The aims of this study were to evaluate the spectrum of PTLs using current lymphoma classification concepts and immunocytochemical markers, determine whether features of MALT-type lymphoma were evident in PTL, and if there was any clinical significance of such a finding. METHODS AND RESULTS: The cases were retrospectively studied clinically, histologically and immunohistochemically. The tumours were classified according to the Revised European-American Lymphoma Classification of lymphoid malignancies (REAL classification). Thirty-eight patients were females, 15 were males and mean age at diagnosis was 66.3 years (range 38-90). Three cases were low-grade marginal zone lymphomas (low-grade MALT-type lymphomas). There were 45 diffuse large B-cell lymphomas (DLBCL) of which there were 27 DLBCL-NOS and 18 high-grade MALT-type lymphomas. Within the diffuse large B-cell lymphoma (DLBCL) category, cases were subdivided into those without (DLBCL-NOS) and those with features of 'high-grade' MALT-type lymphoma based on presence of a low-grade component or large cell lymphoepithelial lesions (HG MALT-type lymphoma). In addition there were three follicle centre lymphomas, one anaplastic large cell lymphoma and one peripheral T-cell lymphoma. Twenty cases were stage IE, 18 stage IIE, and four stage IV. All patients with low-grade MALT-type lymphoma are alive without disease. The 5-year survivals for DLBCL-NOS and HG MALT-type lymphoma were 75% and 25%, respectively. Univariate analysis (log rank) among the DLBCLs showed stage (P < 0.001) and subtype (P = 0.005) were associated with survival. Stage was associated with type of DLBCL, 65% of DLBCL-NOS being stage IE compared to 20% of HG MALT-type lymphomas. CONCLUSIONS: We conclude that primary thyroid lymphomas occur most commonly in elderly women and are frequently present in clinical stage IE and IIE. Low-grade MALT-type lymphomas are relatively uncommon but appear to have a favourable prognosis. DLBCL is the most common lymphoma and features of MALT can be seen in over one-third of cases. As a group, HG MALT-type lymphomas had a worse outcome than DLBCL-NOS, primarily due to higher clinical stage at diagnosis. These two subtypes of DLBCL appear to be distinct clinical and histological entities.

Adult↗
PubMed2001

Somatostatin-receptor scintigraphy for staging and follow-up of patients with extraintestinal marginal zone B-cell lymphoma of the mucosa associated lymphoid tissue (MALT)-type.

The majority of lymphomas of the mucosa-associated lymphoid tissue (MALT)-type arise in the stomach, but extragastric locations are also frequently encountered. Due to previous results indicating that somatostatin receptor (SSTR)-expression distinguishes between gastric and extragastric MALT-type lymphoma, we have initiated a study to evaluate the role of SSTR-scintigraphy for staging and follow-up of patients with extragastric manifestations of MALT-type lymphoma. A total of 30 consecutive patients, including 24 with primary extragastric MALT-type lymphoma, 5 patients with dissemination to extragastric sites (including colon, lung, parotid, ocular adnexa and breast) following an initial gastric MALT-lymphoma and one patient with spread to stomach, lung and lymph nodes following parotid lymphoma were prospectively studied. All patients had histologically verified MALT-type lymphoma: 2 patients had lymphoma presenting in the lung, 9 in the ocular adnexa, 7 had lymphomas in the parotid, 2 patients had disease located in the breast, 3 patients had lymph-node relapse following MALT-type lymphoma of the parotid, the lacrimal gland and the thyroid, and 1 had primary MALT-lymphoma of the liver. All patients underwent SSTR-scintigraphy using (111)In-DTPA-D-Phe(1)-Octreotide ((111)In-OCT) before initiation of therapy, while 13 also had a second scan after treatment. The results of gamma camera imaging were compared to conventional staging. No positive scans could be obtained in patients with dissemination following gastric lymphoma, while all patients with primary extragastric lymphoma had positive scans at the site of histologically documented involvement before initiation of therapy. In addition, also the patient with secondary spread to stomach, lung and lymph nodes was positive in all documented lymphoma sites. In one patient, focal tracer uptake in projection to the maxillary sinus was documented, which was bioptically verified as inflammation. In the scans performed after therapy, focal tracer accumulation in the left orbit indicated persistence of disease following irradiation in one patient with otherwise negative work-up, which was verified by MRI and biopsy 6 months later. In another patient, a positive scan indicated disease relapse in the lacrimal gland 9 months before clinical verification by means of ultrasound. In one patient, a focus not present in the pretherapeutic scan was found in the ethmoidal sinus, corresponding to a hyperplastic polyp. Both SST-scan as well as CT indicated disease persistence in one case, while negative scans corresponding to complete remission as judged by conventional staging were obtained following therapy in the remaining patients, and absence of relapse has been confirmed for a median follow-up of 2 years. These results indicate that (111)In-OCT is an excellent tool for staging and non-invasive therapy-monitoring in extragastric MALT-type lymphomas. These data further confirm our initial finding that gastric MALT-type lymphomas do not express relevant amounts of respective SSTR, and that SSTR-scanning is able to distinguish between gastric vs extragastric origin of MALT-type lymphoma irrespective of the site of presentation.

Adult↗
PubMed1999

CDR3 sequences of MALT lymphoma show homology with those of autoreactive B-cell lines.

We have examined the CDR3 sequence and adjacent regions of immunoglobulin genes from B-cell lymphoma of mucosa-associated lymphoid tissue (MALT). Twenty-nine sequences (15 sequences from 13 low-grade MALT lymphomas, marginal zone B-cell lymphomas; 7 sequences from 6 high-grade MALT lymphomas; 7 sequences from 7 diffuse large cell lymphomas) were obtained after cloning of the polymerase chain reaction-amplified segments. In the low-grade MALT, high-grade MALT and diffuse large cell lymphomas, the mean length of the CDR3 region was 47.6+/-10.31 (range 21 to 60), 38.71+/-10.37 (range 27 to 57) and 40.86+/-3.34 (range 39 to 48) nucleotides, respectively. The length of the CDR3 region was significantly greater in the low-grade MALT lymphoma group than in the other two groups. CDR3 sequences in lymphoma cell clones of 14 cases showed 60 to 81% homology with autoantibody-associated lymphocyte clones including rheumatoid factor. The incidences of these autoantibody-associated lymphocyte clones were higher in the high-grade MALT (4/6) and diffuse large lymphomas (5/7) than in the low-grade MALT lymphoma (5/13). Cases with more than 70% homology at the nucleotide level were found to have 71 to 82% homology with autoantibodies at the protein level in the low-grade MALT lymphomas (2/13), and 67% homology in the high-grade MALT lymphomas (2/7). These results indicate that MALT lymphomas may be derived from the malignant transformation of autoreactive B-cells.

Amino Acid Sequence↗
PubMed2006

Comparison of localized gastric mucosa-associated lymphoid tissue (MALT) lymphoma with and without Helicobacter pylori infection.

BACKGROUND: The clinical features and clinical course of Helicobacter pylori-negative gastric mucosa-associated lymphoid tissue (MALT) lymphoma are unclear and a treatment strategy has not yet been established. AIM: To clarify the clinical differences between H. pylori-positive and H. pylori-negative gastric MALT lymphoma, we compared these two types of gastric MALT lymphoma. MATERIALS AND METHODS: Fifty-seven patients with localized gastric MALT lymphoma were studied. H. pylori infection was present in 41 and absent in 16. Treatment consisted of antibiotic therapy and/or 30 Gy radiation therapy. Response assessment was performed every 3-6 months by esophagogastroduodenoscopy including gathering biopsy samples, endoscopic ultrasonography, clinical examination, and various imaging procedures. The median follow-up period was 37 months. RESULTS: There were no significant differences between H. pylori-positive and H. pylori-negative gastric MALT lymphoma patients in terms of sex, age, stage, gross phenotype, affected area of the stomach, or the presence of monoclonality. Complete regression was achieved with antibiotic therapy against H. pylori-negative gastric MALT lymphoma in one of nine patients (11.1%), compared to 28 of 38 patients (73.7%) with H. pylori-positive gastric MALT lymphoma (p < .001). Radiation therapy showed high effectiveness for the local control of H. pylori-negative or antibiotic-resistant gastric MALT lymphoma (92.9%), although distant recurrence was recognized in three of 14 patients (21.4%). Two of 16 patients (12.5%) with H. pylori-negative gastric MALT lymphoma died because of the transformation of the disease into diffuse large B-cell lymphoma. There was a significant difference in both the overall and cause-specific survival rate between the two groups (p = .038). CONCLUSION: Radiation therapy is the effective treatment for H. pylori-negative or antibiotic-resistant localized gastric MALT lymphoma. However, careful systemic follow-up for distant involvement should be required. Transformation into diffuse large B-cell lymphoma is thought to be the important cause of death in patients with gastric MALT lymphoma.

Adult↗
PubMed2006

p27(Kip1) is detected on most gastric MALT lymphomas, but not large cell lymphomas.

We investigated the relationship of gastric mucosa-associated lymphoid tissue (MALT) lymphoma tumorigenesis to Helicobacter pylori infection, the t (11;18) translocation, and alterations in cell cycle regulators. We sought to assess the implications of altered expression of p27(Kip1), a cyclin-dependent kinase inhibitor, on high-grade transformation and responsiveness to eradication therapy. We used immunohistochemistry to examine p27(Kip1), p53, and Ki-67 expression in 23 MALT lymphomas, five diffuse large B-cell lymphomas (DLBCLs), and four DLBCLs with associated MALT lymphoma. All of the MALT lymphomas were positive for p27(Kip1) expression and negative for p53 with a low Ki-67 index, regardless of the sensitivity of these cells to eradication. All DLBCLs were negative for p27(Kip1) and positive for p53, exhibiting a high Ki-67 index. In DLBCLs with MALT lymphoma, p27(Kip1) expression was absent from both the MALT and large cells components. In all of these lymphomas, the MALT components were negative for p53 and displayed a low Ki-67 index, while the large cell components were positive for p53 with a high Ki-67 index. The expression patterns of the DLBCLs differed significantly from those of the MALT lymphomas. p27(Kip1) was not detected in either component of DLBCL with MALT lymphoma, suggesting that decreased expression of p27(Kip1) in the MALT component may be related to high-grade transformation. Thus, p27(Kip1) expression in morphological MALT lymphomas could be useful tool to predict high-grade transformation to DLBCL.

Aged↗
PubMed1992

Extranodal lymphomas: the MALT concept.

Extranodal lymphomas account for as many as 40% of non-Hodgkin's lymphomas and most arise in the gastro-intestinal tract which is a major lymphoid organ in its own right. Gastrointestinal (gut) associated lymphoid tissue (GALT) and that of other mucosae (MALT), differs both structurally and functionally from nodal lymphoid tissue and low grade B cell lymphomas arising in the gastrointestinal tract and other mucosae have been found to recapitulate the structure and cytological features of MALT. Moreover, these lymphomas are clinically indolent which could be explained by the restricted homing patterns of MALT. Curiously, however, most MALT lymphomas arise in sites, such as the stomach, where MALT is not normally present. Several chronic inflammatory conditions, most of which have an autoimmune component, result in the acquisition of MALT-like lymphoid tissue, and have been identified as necessary precursors for the development of MALT lymphoma. These include Helicobacter pylori induced chronic gastritis, Sjögren's syndrome and Hashimoto's thyroiditis. Histologically, low grade MALT lymphomas are characterized by centrocyte-like (CCL) B cells which surround reactive follicles and form characteristic lympho-epithelial lesions with adjacent epithelium; they frequently show plasma cell differentiation. Specific colonization of reactive follicles by CCL cells often occurs and transformation into a high grade lymphoma may occur. The phenotype of MALT lymphoma CCL-cells is similar to that of marginal zone B cells; no characteristic genotypic features have yet been identified. When lymph nodes are involved by MALT lymphoma their appearance may be indistinguishable from those of so-called monocytid B cell lymphoma, a primary lymph node tumour which, unlike MALT lymphoma, shares the clinical features of other low grade nodal B cell lymphomas.

Gastric Mucosa↗
PubMedDate not supplied

Expression of p53, p21, mdm2, Rb, bax and Ki67 proteins in lymphomas of the mucosa-associated lymphoid (MALT) tissue.

We have investigated by immunohistochemistry 38 cases of B-cell MALT-NHL comprising 23 high grade (HG) and 15 low grade-(LG) tumours for the expression of p53, mdm2, p21, Rb, Ki67, bcl2 and Bax proteins. P53, mdm2 and p21 proteins were found in at least 5% of the tumour cells in 13/23, 2/23 and 11/23 HG tumours, respectively. These proteins were detected in very rare tumour cells in LG tumours. The following patterns were recorded in HG tumours: p53+/p21+/mdm2+ (2 cases), p53+/p21+/mdm2- (7 cases), p53+/p21-/mdm2- (4 cases), p53-/p21-/mdm2- (18 cases) and p53-/p21+/mdm2-(2 cases). Proliferative Ki67 index and Rb protein expression were higher in HG than in LG MALT-NHL. Bcl2 protein was expressed in all LG MALT-NHL, whereas only 2/23 HG MALT-NHL were bcl2 positive in most tumour cells. Bax protein was expressed in all MALT-NHL with HG tumours being positive in higher proportion of tumour cells than LG tumours. These findings show that significant expression of p53, mdm2, p21,Ki67 and Rb proteins occurs more frequently in aggressive histotypes of MALT-NHL. The parallel Rb/Ki67 expression suggests that Rb protein expression in MALT-NHL is normally regulated in relation to the proliferative growth fraction of the tumours. The pattern p53+/p21+/mdm2 +/- may represent MALT-NHL with wild type (wt) p53 gene since mdm2 and p21 proteins are inducible by wt p53 gene. The pattern p53+/mdm2-/p21-may represent MALT-NHL with p53 gene mutations unable to activate expression of mdm2 and p21 proteins. MALT-NHL with the p53-/mdm2-/p21 + pattern may be consistent with p53-independent p21 expression. Bax protein expression in all MALT-NHL suggests a role for this protein in the pathogenesis of these tumours.

Cell Nucleus↗
PubMed1996

Two amino acid residues from the DNA-binding domain of MalT play a crucial role in transcriptional activation.

MalT is the transcriptional activator of the Escherichia coli maltose regulon. Several lines of evidence suggest that MalT might act by interacting with RNA polymerase. Here, we show that 'MalT, the DNA-binding domain of MalT, activates transcription. In order to identify amino acids of 'MalT playing a specific role in activation, and therefore possibly involved in the putative contact(s) with RNA polymerase, we developed a double screen to isolate mutations of the 'malT gene affecting activation by 'MalT without impairing its DNA-binding affinity. The effect of the mutations thus obtained on activation was assessed in vivo. This strategy essentially pointed to serine 834 and glutamine 876 of the MalT amino acid sequence as specifically involved in activation. Various 'MalT derivatives substituted at positions 834 or 876 were purified and tested in vitro for their DNA-binding affinity, as well as for their activation ability. Together, the results obtained clearly show that serine 834 and glutamine 876 are important for activation by 'MalT but not for DNA-binding. We argue that these amino acid residues are possibly solvent-exposed and propose that they act by contacting RNA polymerase.

Amino Acid Sequence↗
PubMed2005

Motives for malt liquor consumption in a sample of community college students.

Health and community advocates have raised concerns about consumption of malt liquor, a high alcohol content beverage, among youth. Research on malt liquor use is, however, very limited, leaving unanswered questions about what strategies may effectively prevent this use. This study employed qualitative and quantitative research methods with ethnically diverse college samples to explore and identify motives associated with consumption of malt liquor. Of the motives examined, those representing social facilitation and mood enhancement were the most important predictors of malt liquor use. Anticipation of quick intoxication and economic considerations were also uniquely associated with increased consumption of malt liquor after controlling for other motives and background variables. Coping motives and availability of malt liquor, although being significantly related to malt liquor use in bivariate analyses, were not significantly associated with increased consumption of malt liquor in multivariate analyses. Conformity motives were endorsed by few malt liquor drinkers. Study findings suggest that raising the price and lowering the alcohol content of malt liquor may help reduce consumption of this beverage by young people.

Adolescent↗
PubMed2005

Antioxidant properties of kilned and roasted malts.

Compounds possessing antioxidant activity play a crucial role in delaying or preventing lipid oxidation in foods and beverages during processing and storage. Such reactions lead to loss of product quality, especially as a consequence of off-flavor formation. The aim of this study was to determine the antioxidant activity of kilned (standard) and roasted (speciality) malts in relation to phenolic compounds, sugars, amino acids, and color [assessed as European Brewing Convention units (degrees EBC) and absorbance at 420 nm]. The concentrations of sugars and amino acids decreased with the intensity of the applied heat treatment, and this was attributed to the extent of the Maillard reaction, as well as sugar caramelization, in the highly roasted malts. Proline, followed by glutamine, was the most abundant free amino/imino acid in the malt samples, except those that were highly roasted, and maltose was the most abundant sugar in all malts. Levels of total phenolic compounds decreased with heat treatment. Catechin and ferulic acid were the most abundant phenolic compounds in the majority of the malts, and amounts were highest in the kilned samples. In highly roasted malts, degradation products of ferulic acid were identified. Antioxidant activity increased with the intensity of heating, in parallel with color formation, and was significantly higher for roasted malts compared to kilned malts. In kilned malts, phenolic compounds were the main identified contributors to antioxidant activity, with Maillard reaction products also playing a role. In roasted malts, Maillard reaction products were responsible for the majority of the antioxidant activity.

Amino Acids↗
PubMed2003

T(11;18)(q21;q21) in gastric MALT lymphoma and diffuse large B-cell lymphoma of Chinese patients.

T(11;18)(q21;q21) occurs at variable frequencies in mucosa-associated lymphoid tissue (MALT) lymphomas of different sites. In gastric MALT lymphoma, it occurs in 30% cases and the translocation positive tumours are frequently at advanced stages and do not respond to Helicobacter pylori eradication. Intriguingly, t(11;18)(q21;q21) has been observed only rarely in mucosal diffuse large B-cell lymphomas (DLBCL), despite that at least a proportion of these tumours are believed to be the result of transformation of an MALT lymphoma. We previously examined t(11;18)(q21;q21) in gastric MALT lymphoma of Chinese in Taiwan and found the translocation in one of the three transformed MALT lymphomas studied. To extend this observation, we have examined t(11;18)(q21;q21) in a large cohort of gastric lymphomas of Chinese in China including 39 MALT lymphomas (12 with high-grade components) and 53 DLBCL by reverse transcription and PCR. Of these cases, RNA samples extracted from 36 MALT lymphomas including 10 cases with high-grade component and 46 DLBCL were adequate for detection of the translocation as judged by control RT-PCR of a house-keeping gene. T(11;18)(q21;q21) was found in 8/36 (22%) MALT lymphomas and 1/46 (2%) DLBCL. None of the MALT lymphoma with high-grade component showed t(11;18)(q21;q21). Our results suggest that t(11;18)(q21;q21) occurs only occasionally in transformed MALT lymphoma.

Adaptor Proteins, Signal Transducing↗