Biomedical subjects

K H Ramesh

Publications and source records attributed to K H Ramesh.

At least 19 recordsLinked to original sources

PubMed2006

AIDS and non-AIDS diffuse large B-cell lymphomas express different antigen profiles.

Based on gene expression profiling, diffuse large B-cell lymphomas arising in immunocompetent patients can be divided into germinal center and activated B-cell types. Since little is known about acquired immunodeficiency syndrome associated diffuse large B-cell lymphomas, we tested whether the protein expression of germinal center and activated B-cell markers differed between acquired immunodeficiency syndrome (AIDS) vs non-AIDS diffuse large B-cell lymphomas. We immunohistochemically stained tissue microarrays of 39 de novo diffuse large B-cell lymphomas: 12 AIDS associated and 27 non-AIDS, with germinal center (BCL6, CD10, CyclinH) and activated B-cell markers (MUM1, CD138, PAK1, CD44, BCL2). We scored each case for percent positive cells (0-19%=0; 20-49%=1; 50-100%=2). The activated B-cell and germinal center summation scores of each case were used as (x, y) coordinate data points to construct two-dimensional contour-frequency plots. The contour plot of non-AIDS diffuse large B-cell lymphomas showed two distinct clusters: a cluster with a high germinal center phenotype (cluster 1) and a cluster with a high activated B-cell phenotype (cluster 3). In contrast, the AIDS-related diffuse large B-cell lymphomas formed a single aggregate (cluster 2) (P=0.02, Fisher exact test). When the contour plots of the AIDS-related and the non-AIDS cases were superimposed, cluster 2 of the AIDS cases expressed an intermediate germinal center/activated B-cell phenotype compared to clusters 1 and 3 of the non-AIDS diffuse large B-cell lymphomas. Our results confirm that non-AIDS diffuse large B-cell lymphomas segregate into two groups with either germinal center or activated B-cell phenotype. We report the new finding that the AIDS status of the patient predicts the immunophenotype of the diffuse large B-cell lymphomas.

Adult↗

PubMed2005

Germinal center and activated b-cell profiles separate Burkitt lymphoma and diffuse large B-cell lymphoma in AIDS and non-AIDS cases.

Morphologic features of Burkitt lymphoma (BL) and diffuse large B-cell lymphoma (DLBCL) overlap. No single phenotypic marker or molecular abnormality is pathognomonic. We tested a panel of 8 germinal center (GC) and activated B-cell (ABC) markers for their ability to separate BL and DLBCL. We diagnosed 16 BL and 39 DLBCL cases from 21 patients with AIDS and 34 without AIDS based on traditional morphologic criteria, Ki-67 proliferative index, and c-myc rearrangement (fluorescence in situ hybridization). After immunohistochemically staining tissue microarrays of BL and DLBCL for markers of GC (bcl-6, CD10, cyclin H) and ABC (MUM1, CD138, PAK1, CD44, bcl-2), we scored each case for the percentage of positive cells. Hierarchical clustering yielded 2 major clusters significantly associated with morphologic diagnosis (P < .001). For comparison, we plotted the sum of the GC scores and ABC scores for each case as x and y data points. This revealed a high-GC/low-ABC group and a low-GC/high-ABC group that were associated significantly with morphologic diagnosis (P < .001). Protein expression of multiple GC and ABC markers can separate BL and DLBCL.

Adolescent↗

PubMed2004

Acute promyelocytic leukemia cell line AP-1060 established as a cytokine-dependent culture from a patient clinically resistant to all-trans retinoic acid and arsenic trioxide.

AP-1060 is a newly established acute promyelocytic leukemia (APL) cell line from a multiple-relapse patient clinically resistant to both all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). The line was initially derived as a granulocyte colony-stimulating factor-dependent strain that underwent replicative senescence and, following ethylnitrosourea treatment, as a phenotypically similar immortalized line. Immortalization was associated with broadened cytokine sensitivity but not growth autonomy, in contrast to three previously derived APL lines. Both the AP-1060 strain and line had shortened telomeres and low telomerase activity, while the line had higher expression of many genes associated with macromolecular synthesis. The karyotype was 46,XY,t(3;14)(p21.1;q11.2),t(15;17)(q22;q11)[100%]; the unique t(3;14) was observed in 4/9 t(15;17)-positive metaphase cells at previous relapse on ATRA therapy. The PML-RARalpha mRNA harbored a missense mutation in the RARalpha-region ligand-binding domain (Pro900Ser). This was associated with a right-shift and sharpening of the ATRA-induced maturation response compared to ATRA-sensitive NB4 cells, which corresponded to the transcriptional activation by PML-RARalphaPro900Ser of a cotransfected ATRA-targeted reporter vector in COS-1 cells. AP-1060 also manifested relative resistance to ATO-induced apoptosis at >/=1 microM, while 0.25 microM ATO stimulated limited atypical maturation. These findings suggest that AP-1060 will be useful for further assessing molecular elements involved in APL progression and drug response/resistance.

Arsenic Trioxide↗

PubMed2003

Evidence for expression of early myeloid antigens in mature, non-blast myeloid cells in myelodysplasia.

Myelodysplastic syndromes (MDS) are clonal hematopoietic stem cell disorders with frequent cytogenetic abnormalities. They can arise de novo or be related to therapy. Although blasts in MDS have been studied extensively, there is little information available on the mature, non-blast myeloid cells (NBMCs). We used a retrospective case-control study design. NBMC populations in MDS (48 cases) and in tumor-free control (12 cases) bone marrow samples were analyzed using multiparameter flow cytometry for mean side scatter (SSC) channel number and for expression of aberrant cell surface antigens. MDS cases were stratified on the basis of cytogenetic abnormalities. We report that NBMCs in MDS with normal karyotype expressed significantly higher HLA-DR than controls (P = 0.034). NBMCs in MDS cases with cytogenetic abnormalities and with > or =5% marrow blasts, compared with controls, had significantly higher CD34 and higher HLA-DR but lower CD10 and lower SSC mean channel number. CD34 expression in NBMCs was significantly greater in therapy-related MDS compared with de novo MDS ( P = 0.01), although the presence of cytogenetic abnormalities was not different ( P > 0.05). These data suggest that bone marrow, mature, NBMCs have phenotypic changes in MDS that are not seen in normal controls.

Adult↗

PubMed2001

Characterization of t(11;19)(q23;p13.3) by fluorescence in situ hybridization analysis in a pediatric patient with therapy-related acute myelogenous leukemia.

This case presents a Caucasian girl diagnosed with early pre-B cell acute lymphoblastic leukemia at age 2 years. The only chromosomal anomaly detected in her bone marrow cells at this time was an add(12p). By age 4 years, she had a bone marrow and central nervous system (CNS) relapse of ALL and was treated with chemotherapy that included etoposide. She was in complete remission for 2 years following chemotherapy with etoposide, but later developed therapy-related acute myeloid leukemia (t-AML). At this time, a t(11;19)(q23;p13.3) rearrangement was detected in her bone marrow cells. The AML relapsed again 1 year after allogeneic bone marrow transplant (BMT). The presence of a chromosome 11 abnormality involving band 11q23 in this patient suggests that the transformation from ALL to t-AML was a consequence of etoposide included in her chemotherapy. Studies have shown that the 11q23 breakpoint in the t(11;19) rearrangement is consistent, and involves the MLL gene in t-AML patients. However, the breakpoint in 19p is variable in that it could be located either at 19p13.1 or 19p13.3 and thus could involve either of two genes: ELL (11-19 lysine-rich leukemia gene) on 19p13.1 or ENL (11-19 leukemia gene) on 19p13.3. In this study, the t(11;19)(q23;p13.3) was further characterized and the breakpoint regions were defined by fluorescence in situ hybridization (FISH) analysis.

Child, Preschool↗

PubMed1998

FHIT gene transcript alterations occur frequently in myeloproliferative and myelodysplastic diseases.

Twenty-five primary biopsy samples, obtained from patients diagnosed with chronic/acute myeloproliferative disorders, myelodysplastic disorders, in addition to seven cell lines established from patients with leukemias arrested at different stages of myeloid differentiation, were examined for alterations in an alternatively spliced form of the FHIT gene. Transcript alterations of this gene were detected in 80% of the primary biopsies and in two of the cell lines. Reverse transcription PCR (RT-PCR) detected deletions of one or more specific exons in the translated or untranslated portion of the FHIT gene. Point mutations in exons 3, 4, and 5 of the FHIT gene were also detected in 4 patients by single stranded conformational PCR analysis. Transcript alterations were detected in all primary hematopoietic samples which contained chromosome abnormalities, as well as, in hematopoietic disorders which did not show alterations of the 3p14 region. These findings suggest FHIT gene involvement in the transformation of hematopoietic stem cells to leukemia.

Acid Anhydride Hydrolases↗

PubMed1997

Direct insertion of euchromatic material from chromosome Y in the X-chromosome in hypogonadotropic hypogonadisms with Crohn's disease.

The relationship between chromosomal abnormalities and Crohn's disease has not been established. Crohn's disease is associated with inflammation of the bowel, severe abdominal pain and chronic diarrhea. Its etiology is not known at present. A recessive gene with incomplete penetrance is thought to be a factor which does not follow simple mendelian inheritance. We report a case, where the euchromatin material of Y chromosome (p11.1 p11.2) has been directly inserted into the long arm of the X chromosome (q21.2), and is assumed to be the most likely cause of hypogonadotropic hypogonadism in this patients. It could also be that the function of the testis-determining factor (SRY) has been disrupted due to the insertion, causing loss of testicular development.

Adolescent↗

PubMed1997

Clonal chromosome aberrations with monosomy of chromosome 8 in a case of grade III chondrosarcoma.

We report cytogenetic findings in a case of grade III chondrosarcoma. Complex clonal chromosome aberrations including monosomy of chromosomes 4, 8, 13, and a consistent t(5;14)(q23;p12) were observed in all cells. There were no structural or numerical anomalies involving chromosome 12. The complexity of the chromosome aberrations reflect the advanced stage of this chondrosarcoma; we suggest a possible involvement of the EXT1 gene located on chromosome 8.

Aged↗

PubMed1997

Comparative mapping of human alphoid satellite DNA repeat sequences in the great apes.

Heterochromatic regions of chromosomes contain highly repetitive, tandemly arranged DNA sequences that undergo very rapid variation compared to unique DNA sequences that are predominantly conserved. In this study the chromosomal basis of speciation has been looked at in terms of repeat sequences. We have hybridized twenty-one chromosome-specific human alphoid satellite DNA probes to metaphase spreads of the chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla), and orangutan (Pongo pygmaeus) to investigate the evolutionary relationship of heterochromatic regions among such hominoid species. The majority of the probes did not hybridize to their corresponding equivalent chromosome but presented hybridization signals on non-corresponding chromosomes. Such observations suggest that rapid changes may have occurred in the ancestral alphoid satellite DNA sequence, resulting in divergence among the great ape species.

Animals↗

PubMed1997

Rapid denaturation improves chromosome morphology and permits multiple hybridizations during fluorescence in situ hybridization.

Denaturation of chromosomal DNA for fluorescence in situ hybridization (FISH) is an essential step in a procedure associated with a number of variables. In our experience, shorter denaturation time in 70% formamide/2 x SSC at 72 C provides sufficient denaturation, where the hydrogen bonds are broken between the purines and pyrimidines of the double helix. This shortened exposure improves retention of morphology of human chromosomes from lymphocytes, aminocytes, fibroblasts and bone marrow, and allows the same metaphases to be denatured repeatedly and rehybridized with different probes. This approach is useful in investigations where sample volume is limited.

Chromosomes, Human↗

PubMed1996

Assignment of human MYCN proto-oncogene to chromosome band 12q24 in higher primates.

Controversies concerning the reduction of chromosome number from 48 to 46 in humans by putative fusion of two ape chromosomes still persist. Nevertheless, abundant evidence suggests that human chromosome 2 was derived by fusion. Consequently, the recent availability of the human MYCN gene probe which was localized to 2p24.3 facilitated our search for its location in the human equivalent chromosome(s) of chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla) and orangutan (Pongo pygmaeus). In all three species, the human MYCN gene was localized to the long arm of chromosome 12 band 12q24 which is the corresponding band equivalent of the short arm of human chromosome 2. The conservation of MYCN gene in higher primates at the equivalent chromosome locus that corresponds to that of the human provides additional prevailing view towards tracing the evolutionary pathways concerning the origin of chromosome 2, though we recognize that there are conceptual problems concerning human descent.

Animals↗

PubMed1996

Regional localization of human M-BCR gene to chromosome 23 band q11 in the great apes.

We hybridized a human M-BCR DNA probe to the chromosomes of chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla) and orangutan (Pongo pygmaeus) by FISH-technique. The human M-BCR gene was localized to chromosome 23 band q11 (23q11), which is equivalent to the human chromosome 22 band q11 in all three species. The conservation of M-BCR gene in higher primates at the corresponding human chromosome locus provides phylogenetic clues concerning the evolution of genes.

Animals↗

PubMed1996

Mapping the homolog of the human Rb1 gene to chromosome 14 of higher primates.

The Rb1 gene has been implicated with retinoblastoma and is located on human Chromosome (Chr) 13q14.2. A unique sequence human Rb1 cosmid DNA probe has been used to localize this region on apes' Chr 14 by the FISH technique. The conservation of the Rb1 gene in higher primates at the corresponding equivalent chromosome locus (14q14) of the human may serve as a phylogenetic marker to further trace the evolutionary pathway of human descent.

Animals↗

PubMed1996

Molecular cytogenetic characterization of breakpoints involving pericentric inversions of human chromosome 9.

Pericentric inversions involving the secondary constriction (qh) region of chromosome 9 are considered to be normal variants. The evolutionary mechanisms and conservation of these inversions via Mendelian fashion have been investigated since the advent of banding techniques. Routine cytogenetic techniques cannot provide the fine characterization necessary to determine the type of genetic material involved in these rearrangements. Therefore, the fluorescence in situ hybridization technique with the human centromere-specific alpha satellite and the beta satellite (D9Z5) and classical satellite (D9Z1) human DNA probes were used to identify the breakpoints of chromosome 9 pericentric inversions. Four unique types of pericentric inversions involving the 9qh region were observed, and the mechanism may be due to breakage and reunion at the proposed breakpoints. They are: type A inversions consist of breakpoints within the alpha and beta satellite DNA regions; type B consist of breakpoints within the beta satellite DNA region and band 9q13; type C involve breakage within the beta and classical satellite DNA regions, and type D have breakpoints within the alpha and classical satellite DNA regions. Obviously, reshuffling of satellite DNA sequences has occurred, which has given rise to a variety of heteromorphisms whose clinical significance remains obscure.

Chromosome Breakage↗

PubMed1996

A de novo interstitial deletion of chromosome 15 band q25 as revealed by FISH-technique.

We report a new chromosomal finding in a 20 month-old girl. The minor clinical features included: moderate mental retardation, microcephaly, mild hypotonia and hypertelorism. Initially, what appeared to be a terminal deletion of the long arm of one chromosome 15 [15q26-->qter] was determined to be an interstitial deletion involving band 15q25 as revealed by FISH-technique, showing the presence of intact telomeric hybridization signals. The cytogenetic diagnosis was thus modified to 46,XX, del (15) (pter-->q24::q26--> qter). Nevertheless, the function of the enzyme telomerase should not be ignored, as healing could occur following such terminal deletions. Consequently, it will remain a difficult task to distinguish terminal deletions from those that are interstitial.

Chromosome Banding↗

PubMed1996

Breakpoints in alpha, beta, and satellite III DNA sequences of chromosome 9 result in a variety of pericentric inversions.

Human chromosome 9 with a pericentric inversion involving the qh region is considered normal. It has probably evolved through breakage and reunion and is retained through mendelian inheritance without any apparent phenotypic consequences. Fluorescent in situ hybridisation (FISH) technique using alpha, beta, and satellite III DNA probes showed that the breakpoints are variable and can be localised in the alpha or in the satellite III and beta DNA regions or both. Three types of inversions are proposed which appear similar by CBG banding: pericentric inversions with two alphoid, one beta, and one satellite III hybridisation signals were classified as type A. Type B were those with two beta, one alpha, and one satellite III hybridisation signals, while type C was complex, and most likely involved two inversions, since two separate hybridisation signals were detected in each of the alphoid, beta satellite, and satellite III DNA regions. Based on eight cases, type A is likely to be the most frequent, but the frequencies, which at present appear non-random for these different types of inversions in the population, can only be estimated by studying a larger sample size. Inversion heteromorphisms may promote reshuffling of tandem arrays of DNA repeat sequences, thereby giving rise to new heteromorphic domains. Alternatively, the repetitive nature of the sequences lends to the structural variations observed within the inv(9) chromosomes (or any other abnormal chromosome that is the result of recombination between, or breakage within, repetitive DNA).

Chromosome Inversion↗

PubMed1996

Parental origin of the extra chromosome 18 in Edwards syndrome.

Trisomy 18 (Edwards syndrome) is the second most common trisomy in human. The parental origin of the additional chromosome leading to meiotic errors is imperative to understand the etiology of trisomy 18. We compiled the data on 171 cases (table I) where meiotic error is provided. The paternal meiotic error occurred in 7% of the cases while in 93% of the cases nondisjunction took place in the mother. There were 28 cases (16%) where nondisjunction took place in meiosis I(MI), 53 cases (31%) in meiosis II (MII) and in 90 cases (53%) either the error was postzygotic mitosis or the dysfunctional stages could not be determined. The age distribution could be found in 119 cases (table II) and a conclusion could not be drawn as there were only 11 cases where paternal nondisjunction was noted.

Adolescent↗

PubMed1996

Characterization of a derivative chromosome 17 by fish-technique.

We report a case with derivative chromosome 17 which could not be characterized by routine G-banding, since the additional material on 17q overlapped with chromosome bands 2q35 -->qter, 3p25-->pter, 4p15-->pter, 5q33-->qter, 7p15-->pter, 12p11.2-->pter, 14q24-->qter and 16q22-->qter. Therefore, whole chromosome paint and region specific probes were used to identify the abnormality by FISH-technique which revealed a 46,XY, der (17) t (4;17) (p15.2;q25) karyotype. The proband was partially trisomic for 4p15.2-->pter and monosomic for the distal 17q25-->qter regions. The major clinical features included: anti-mongoloid slanted palpebrae, coloboma of right iris, depressed nasal bridge, high arched palate, protruding tongue, micrognathia and small penis. The MRI of the brain revealed midly hypoplastic cerebellar vermis, and a normal septum pellucidum. The infant responded to therapy for hypoglycemia and was discharged under stable condition. Prior to cytogenetic evaluation the infant was not recognized as either "trisomy 4p syndrome" or "monosomy 17q syndrome".

Abnormalities, Multiple↗