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R S Verma

Publications and source records attributed to R S Verma.

At least 91 records · Page 5Linked to original sources
PubMed1995

Molecular characterization of trisomic segment 3p24.1-->3pter: a case with review of the literature.

A 1-year-old male infant was found to have a de novo unbalanced translocation, resulting in trisomy for a portion of the short arm of chromosome 3, i.e. 46,XY,der(7)t(3;7) (p24.1;p22). Previous cases with a so-called "trisomy 3p syndrome" were evaluated by GTG banding, while we attempted to characterize the present case by the FISH-technique. The major clinical features included: dysmorphic ears, decreased muscle tone and seizure episodes associated with fever, which are concordant with "trisomy 3p syndrome". The most common malformations of trisomy 3p syndrome are: psychomotor and mental retardation, short neck, hypertelorism/telecanthus and congenital heart defects. Predominantly, the 3p trisomies have been maternally derived and the major mechanism of inheritance is due to a malsegregation of the chromosomes that are involved in a parental balanced translocation. A review of 44 cases from 35 studies revealed that the clinical manifestations have been quite varied, depending upon the amount of 3p2 material in the trisomic state, but interestingly a recognizable pattern of features was obvious in those cases whose cytogenetic findings and clinical histories were known.

Chromosomes, Human, Pair 3↗
PubMed1995

Characterization of a ring chromosome 21 by FISH-technique.

Ring chromosomes 21 that contain two copies of the Down syndrome critical region (DCR1), thereby contributing to trisomic dosage, have not been fully characterized by routine cytogenetic methods in the past. We therefore employed the fluorescence in situ hybridization (FISH) technique, using a battery of chromosome 21 probes and conclude that the ring resulted from a centromere to centromere and long arm to long arm fusion that contains alpha-satellite DNA and two copies of the D21S65 locus, but lacks beta-satellite DNA and telomeric DNA. Consequently, we suggest that the origin of the ring may be due to the misdivision of the centromere following the duplication of the long arm, forming a monocentric isochromosome followed by breakage in a region distal to the D21S65 locus and proximal to the telomeric sequences followed by reunion of the broken ends resulting in a monocentric ring. Different ring configurations or fragments were not detected, suggesting that the ring chromosome was highly stable. Apparently, the presence of two copies of Down syndrome loci within the ring chromosome, along with one copy on the normal homologue, caused the clinical consequences of Down syndrome.

Centromere↗
PubMed1995

Enumeration of semen leucocytes by fluorescence in situ hybridisation technique.

Aim-To determine whether the fluorescent in situ hybridisation technique (FISH) using a total human DNA genomic probe can be used to enumerate semen leucocytes.Methods-Semen samples from five donors were subjected to a mild KC1 solution. These samples were then biotin labelled under FISH conditions using a total human DNA genomic probe and the leucocyte counts were determined. To check the accuracy of the technique a monoclonal antibody against the common leucocyte antigen CD45 [KC56(T-200)] served as a control. An isotypic control for [KC56(T-200)], the immunoglobulin [MsIgG1], served as a secondary control.Results-Semen leucocytes stained by the FISH technique were easily detected because of their distinct bright yellow colour, while the sperm cells were red. The leucocyte count ranged from 0.5 to 4.9 x 10(6) per ml of semen. KC56(T-200) and its isotypic control MsIgG1, which served as control for the FISH technique, accurately identified 94% and 97% of the semen leucocytes of a control donor, respectively.Conclusions-The FISH technique using a total human DNA probe can accurately and effectively enumerate the overall leucocyte population in semen.

Journal Article↗
PubMed1995

Mechanisms of the origin of a G-positive band within the secondary constriction region of human chromosome 9.

We report on a so-called rare variant where a G-positive band was sandwiched within the secondary constriction (qh) region of chromosome 9 and is apparently different from previous cases when characterized by the fluorescence in situ hybridization technique. The major differences included duplication of beta-satellite and satellite III DNA sequences and bands 9q13-->q21.1, without duplication or inversion of the alphoid sequences. Based on the reported cases, at least four types of variations can be accounted for. A variety of mechanisms have been proposed to describe the origin of a G-positive band within the 9qh region, which appears to be similar when studied by routine cytogenetic techniques but differs by molecular methods. It is hypothesized that the clinical consequences depend upon the size of the G-positive band(s) duplicated, and a genetic inactivation mechanism might have some sort of influence during the so-called heterochromatinization process. It appears that heterochromatin, once thought to be composed of junk DNA, may have some role after all in suppression of gene(s) and/or spreading of inactivation, if genes are embedded within the heterochromatic region. Apparently, the mixture of different types of DNA creating patches of genetic debris have become a fundamental hidden treasure, where genetically active chromatin could be inactivated without dire consequences. The variable nature of heterochromatin has resulted in cytogenetic heteromorphisms of a number of human chromosomes. Their characterization by molecular techniques is becoming imperative, because fetal wastage have occurred in many situations where variant chromosomes were wrongly identified as chromosomal abnormalities.

Chromosome Banding↗
PubMed1995

Characterization of chromosome 11 with a complex inversion and deletion in an AML [M2] using fluorescence in situ hybridization.

We report on a new case of AML [M2] where chromosome 11 was rearranged in a highly complex manner involving band 11q23. Routine G banding failed to identify the nature of this aberration which later was accomplished using whole chromosome 11-specific painting probe by the FISH technique. Chromosome 11 band q23 is frequently involved in reciprocal translocations with various chromosomes, but to have sole morbidity of such a complex nature is an atypical finding in AML [M2]. The band q23 of chromosome 11 involves the mixed lineage leukemia gene and rearrangement of this chromosomal region has been found in a variety of neoplasias. Henceforth, its precise identification has become imperative for classification of hematological malignancies and in turn to devise therapeutic strategies.

Bone Marrow↗
PubMed1994

Two Prader-Willi/Angelman syndrome loci present in an isodicentric marker chromosome.

We found an abnormal 47,XX,+mar karyotype in a patient with developmental delay, hypotonia, microcephaly, failure to thrive, and cognitive delay. When metaphases were hybridized with Prader-Willi and Angelman loci-specific probes by the FISH technique, two sites were noted at opposite positions on the marker chromosome. The alphoid satellite DNA probe documented the isodicentric nature while retention of the p arms on both sides of the marker chromosome was demonstrated by beta satellite probe. The patient does not exhibit manifestations of either syndrome despite the presence of these loci in tetrasomic dose. The present investigation suggests that other marker chromosomes be reevaluated, as their clinical manifestations are quite variable.

Abnormalities, Multiple↗
PubMed1994

Evolutionary divergence of human chromosome 9 as revealed by the position of the ABL protooncogene in higher primates.

Attempts to solve the fundamental questions regarding the descent of man are dogged by superstitions and unexamined orthodoxies. The origin of humans, established a decade ago based upon cytological analysis of ape chromosomes, continues to be called into question. Although molecular methods have provided a framework for tracing the paths of human evolution, conclusive evidence remains elusive. We have used a single ABL gene probe derived from human chromosome 9 to assess the direction of change in the equivalent ape chromosomes. This approach has resulted in a few surprises which again challenge the prevailing view of early primate evolution based solely on chromosome banding patterns. The ABL proto-oncogene is present on human chromosome 9 at band q34. Similar DNA sequences presumed to represent an ABL gene, are present on chromosome 11 in chimpanzee (Pan troglodytes) but at a different relative location, indicating that the mechanism of the origin of human chromosome 9 is far more complex than has previously been suggested. Nevertheless, in gorilla (Gorilla gorilla) and orangutan (Pongo pygmaeus), the equivalent to human chromosome band 9 q34 is apparently located on chromosome 13 at a putative telomeric position and no discernible differences could be established. Despite the presence of the ABL protooncogene on human equivalent ape chromosomes, molecular systematics will continue to generate enigmas in the evolutionary context until the entire genome is sequenced.

Animals↗
PubMed1994

Counterstained enhancement of TaqI resistant sites after distamycin A/diamidinophenylindole treatment.

Numerous selective and differential staining techniques have been used to investigate the hierarchical organisation of the human genome. This investigation demonstrates the unique characteristics that are produced on fixed human chromosomes when sequential procedures involving restriction endonuclease TaqI. distamycin A (DA) and 4',6-diamidino-2-phenylindole (DAPI) are employed. TaqI produces extensive gaps in the heterochromatic regions associated with satellite II and III DNAs of human chromosomes 1, 9, 15, 16 and Y. DA/DAPI selectively highlights, as brightly fluorescent C-bands, the heterochromatin associated with the alpha, beta, satellite II and III DNAs of these chromosomes. When DA and DAPI are used on chromosomes before TaqI digestion, and then stained with Giemsa, the centromeric regions appear to be more resistant, producing a distinct C-banding pattern and gaps in the heterochromatin regions. Sequential use of the DA/DAPI technique after TaqI treatment produces a bright fluorescence on the remaining pericentromeric regions of chromosomes 1, 9, 16 and Y, which also displayed a cytochemically unique banding pattern. This approach has produced specific enhanced chromosomal bands, which may serve as tools to characterize genomic heterochromatin at a fundamental level.

Azure Stains↗
PubMed1994

Alphoid DNA diversity of a so-called monocentric Robertsonian fusion.

The centromeric heterochromatin of a Robertsonian translocation with t(13q14q), thought to be monocentric by conventional staining methods, was found to be dicentric using molecular techniques. The breakpoints were confined within the alphoid DNA subfamilies and fusion resulted in a compound centromere. The fragile nature of alphoid DNA sequences during Robertsonian translocation has opened new avenues in understanding other chromosomal aberrations involving centric fusion.

Chromosomes, Human, Pair 13↗
PubMed1994

New translocations [t(6;15)(p25;q22) and t(6;19)(q16;q13.3)] with t(9;22)(q34;q11) in a Ph-positive chronic myelogenous leukemia.

A case with typical features of chronic myelogenous leukemia (CML) with two complex aberrations in addition to the standard t(9;22) is reported. Cytogenetic evaluation of the patient's bone marrow cells (BMC) showed 46,XX,t(6;19)(q16;p13.3),t(9;22)(q34;q11) in 60% of the mitotic cells and 46,XX,idem, t(6;15)(p25;q22) in the remaining 40% dividing cells. The patient's peripheral blood smear exhibited the usual differential observed in chronic-phase CML and was clinically indistinguishable from patients with the t(9;22) as the only translocation. We performed Southern blotting on BglII-digested DNA with the Trans-Probe (OSI) and in addition to the 4.8-, 2.3-, and 1.1-kilobase (kb) germline fragments, we detected an additional fragment at 7 kb. This probe spans the entire 5.8-kb M-breakpoint cluster region (BCR), and a single breakpoint in this region will appear as either one or two additional fragments. Because only one additional fragment was observed, both cell lines apparently share the same breakpoint in the ABL/BCR gene. Apparently the second aberrant cell line with the additional t(6;15) represents clonal evolution of the original abnormal clone.

Adult↗
PubMed1994

Centromeric and telomeric repeats are stable in nonagenarians as revealed by the double hybridization fluorescent in situ technique.

We report a simple method for simultaneous identification of centromeric and telomeric repeat sequences of human chromosomes. Employing this technique, we investigated the stability of centromeres and telomeres in individuals over 90 years of age and compared them with younger controls (< 40 years). Our findings suggest that centromeric and telomeric repeats remain apparently stable in nonagenarians. These findings are enigmatic because it has been suggested that centromeres are lost in older individuals. Furthermore, telomeric shortening has been observed in aged lymphocytes and cellular senescence. However, stability of telomeric repeats noted in nonagenarians may be masked by loss followed by compensation by a process called telomeric elongation.

Adult↗
PubMed1994

Identification of a non-fluorescent isodicentric Y chromosome by molecular cytogenetic techniques.

A 12 1/2-month-old girl was referred because of short stature, short neck, large internipple distance and simian crease on her right hand. By routine cytogenetic techniques the presence of an unidentifiable marker chromosome and loss of one X chromosome was noted (i.e. 45, X/46, X, mar/47, X, mar, +mar). By fluorescence in situ hybridization (FISH) technique, the marker chromosome was identified as an isodicentric non-fluorescent Y chromosome ((45, X/46, X, idic (Ynf)/47, X, idic (Ynf), +idic (Ynf)). Although the clinical significance of this finding cannot be assessed at present, possible development of gonadoblastoma in such cases is a major concern and warrants follow-up evaluations.

Chromosome Banding↗