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Biomedical subjects

R S Verma

Publications and source records attributed to R S Verma.

At least 19 recordsLinked to original sources
PubMed1992

Immunoreactive folate-binding proteins from human saliva. Isolation and comparison of two distinct species.

Human saliva contains a single 72,000-M(r) species which specifically reacted with rabbit anti-[human placental folate receptor (PFR)] serum on SDS/PAGE and Western blots. Although a specific radioimmunoassay for human PFR and related folate-binding proteins (FBPs) identified 55 ng of cross-reacting material (CRM) per mg of crude salivary proteins, only a minor fraction (1.6 ng) specifically bound radiolabelled folate. The major fraction of CRM did not contain bound endogenous folate and did not bind radiolabelled folates. On the basis of folate binding, salivary CRM species to PFR were designated as either functional (f-FBP) or non-functional (nf-FBP) species respectively. nf-FBPs and f-FBPs were isolated by different purification schemes. Both purified f-FBPs and nf-FBPs migrated as a single apparent 72,000-M(r) species on SDS/PAGE, but on Sephacryl S-200 gel filtration and sucrose-density-gradient ultracentrifugation they were eluted/sedimented with 40,000-M(r) markers. Each microgram of purified f-FBP and nf-FBP was measured in the radioimmunoassay for PFR as being equivalent to 18 ng and 24 ng of CRM respectively, indicating low epitope-relatedness to PFR. The Kd of f-FBPs was 50 pM and 0.94 mol of folate was bound/mol of protein. f-FBPs exhibited an unusual dependence on Triton X-100 for optimal ligand binding, despite the fact that Triton X-100 micelle binding was not demonstrated. The relative order of affinity of f-FBPs for pteroylglutamate greater than methotrexate greater than 5-formyltetrahydrofolate greater than 5-methyltetrahydrofolate was also distinct from that of purified PFR. Whereas amino acid and carbohydrate analysis revealed that nf-FBP (M(r) 51,400) and f-FBP (M(r) 39,200) were distinct glycoproteins with 8 and 13% carbohydrate respectively, isoelectric focusing and immunological studies suggested some structural identity. The presence of f-FBP and nf-FBP in normal saliva raises new questions about their possible role in vivo.

Adult↗
PubMed1992

Detection of the heteromorphic spectrum of heterochromatin in the human genome by in situ digestion using restriction endonuclease AluI.

A battery of selective banding techniques has been utilized to identify the heteromorphic markers in the human genome. The recent addition of the AluI/Giemsa (G)-technique has helped not only in identifying the variable sites, but in characterizing their heteromorphic spectra. In the present investigation, we classified the pericentromeric heterochromatin by the AluI/G-technique by its size and position using 50 normal individuals and suggested the potential uses of this banding technique over earlier methods.

Chromosome Banding↗
PubMed1992

Evidence that the hydrophobicity of isolated, in situ, and de novo-synthesized native human placental folate receptors is a function of glycosyl-phosphatidylinositol anchoring to membranes.

Although normal human chorionic villi-associated hydrophobic placental folate receptors (PFR) are converted to hydrophilic forms by an endogenous, EDTA-sensitive, Mg(2+)-dependent protease under serum-free conditions (Verma, R. S., and Antony, A. C. (1991) J. Biol. Chem. 266, 12522-12535), it is not known whether hydrophobic PFR are also susceptible to conversion by endogenous phospholipases. We isolated and characterized hydrophobic PFR, and tested the hypothesis that purified, in situ, and de novo-synthesized native PFR were covalently linked to glycosyl-phosphatidylinositol (GPI) anchors. 125I-hydrophobic PFR, but not 125I-hydrophilic PFR, (i) separated into the Triton X-114 micellar phase at 30 degrees C, (ii) efficiently incorporated into phosphatidylcholine-cholesterol liposomes, and (iii) were covalently labeled by the hydrophobic probe 3-(trifluoromethyl)-3-(meta[125I]iodophenyl)diazirine, [125I]TID. (iv) [125I]TID-labeled- and [phenyl-3H]Triton X-100-bound hydrophobic PFR, as well as native PFR in situ, were released as hydrophilic forms by recombinant (r) GPI-specific phospholipase(PL) C (GPI-PLC), and GPI-PLD (but not by PLC), in the absence and presence of a concentration of EDTA known to inhibit endogenous Mg(2+)-dependent protease. (v) Nitrous acid deamination of [125I]TID-labeled hydrophobic PFR as well as (r)GPI-PLC cleavage of [phenyl-3H]Triton-X-100- and [125I] TID-labeled hydrophobic PFR, released hydrophobic radiolabeled moieties which comigrated on thin layer chromatography distinct from free radiolabel. Finally, (vi) biosynthetic studies on chorionic villi cultured in vitro revealed incorporation of radiolabeled precursors into the GPI anchor of hydrophobic PFR. We conclude that native hydrophobic PFR are linked to GPI anchors and are therefore potential substrates for three distinct endogenous enzymes (GPI-PLC, GPI-PLD, and specific Mg(2+)-dependent metalloprotease) in maternal serum and placenta in vivo.

Affinity Labels↗
PubMed1992

Evolution of pericentromeric heterochromatin of human X chromosome.

An unusual large heterochromatic segment around the pericentromeric region of the X-chromosome is reported. In normal circumstances, the pericentromeric region of the X-chromosome is negative by the restriction endonuclease AluI/Giemsa technique. However, this unusual X-chromosome was found to have AluI resistant (positive) chromatin. The evolution of extra heterochromatin is a postzygotic event as substantiated by the presence of a normal cell line.

Biological Evolution↗
PubMed1992

Molecular characterization of "inverted" pericentromeric heterochromatin of chromosome 3.

Inversion of the pericentromeric region of human chromosome 3 [inv (3) (p11q11.2)] is a rare event. Initially, this inversion was identified with staining for Q-bands by fluorescence using quinacrine (QFQ) and later characterized with staining for C-bands by CBG technique. The molecular methods of fluorescence in situ hybridization (FISH) and AluI/Giemsa and TaqI/Giemsa techniques were utilized. The findings suggest that the variable band q11.2 on chromosome 3 contains alphoid DNA sequences, which appear to be similar to those identified by conventional methods in the centromeric region (band p11).

Adolescent↗
PubMed1992

Chromosomal localization of HTLV-1 viral integration sites using in situ hybridization: detection of a novel IL2R fragment.

The presence of human T-cell leukemia virus (HTLV-1) in patients with adult T-cell leukemia (ATL) was investigated by Southern blotting and in situ hybridization. In all seven patients, HTLV-1 provirus was detected. A large and variable number of labeled restriction fragments were observed, indicating multiple integrations. Two of the patients analyzed by in situ hybridization had two, while the third patient had three, sites of viral integration on six different chromosomes, suggesting random integration. A single site of integration was shared by two patients, which was on chromosome 10 at bands p11-->p15. One of these sites was on an apparently normal chromosome 10 and the other was on a derivative chromosome 10,t(10;14)(p12;q32). The interleukin 2 receptor (IL2R) has previously been localized to this region (10p14-->p15). The alpha-chain of the IL2R is continuously expressed on affected T-cells in this disease. Southern blotting with pIL2R showed the presence of a novel 3.5 kb fragment in five out of the seven patients. This novel fragment has not been previously reported. No direct correlation was found between the novel 3.5 kb fragment, present in patients both cytogenetically normal and abnormal, and viral integration in the 10p11-->p15 region in two patients. Therefore, it is suggested that the presence of the 3.5 kb fragment and the numerous chromosomal breaks associated with this disease may not be direct results of viral integration.

Blotting, Southern↗
PubMed1992

Disappearance of a highly unusual clone, 46,XY,del(7)(p12),t(9;22)(q34;q11) in chronic myeloid leukemia after treatment with recombinant interferon and cytosine arabinoside.

A patient with the typical features of the stable phase of chronic myeloid leukemia (CML) displayed two karyotypically related subclones. In addition to the t(9;22), cells from one clone contained a deletion of the short arm of chromosome 7, del(7)(p12), [46,XY,del(7)(p12),t(9;22)(q34;q11)]; the other contained only the standard translocation [46,XY,t(9;22)(q34;q11)]. Cells with a deletion of the short arm of chromosome 7 at band p12 as the only additional abnormality have not been observed previously in CML. Conventional chemotherapy with hydroxyurea and then with recombinant interferon-alpha (rIFN-alpha) did not reduce the population of either subclone. However, after treatment with a combination of rIFN-alpha and low-dose cytosine arabinoside (LoDac) continuously infused subcutaneously (s.c.), cells from the clone with the deleted chromosome 7 disappeared and normal metaphases were demonstrable.

Adult↗
PubMed1992

Localization of the gene coding for ventricular myosin regulatory light chain (MYL2) to human chromosome 12q23-q24.3.

Human myosin light chain-2 (MYL2) is an important protein involved in the regulation of myosin ATPase activity in smooth muscle. In cardiac muscle, the precise role of MYL2 is not well understood; however, an increase in ventricular MYL2 is observed during myocardial hypertrophy in cardiac patients with valve stenosis. The chromosomal location of the gene coding for MYL2 was identified using a cloned cDNA for human MYL2. Southern blot analysis of DNA from a human/rodent somatic cell hybrid mapping panel showed that the BamHI fragment that hybridized with this cDNA probe was concordant with chromosome 12. The 768-bp cDNA was hybridized to human metaphase chromosomes. The results revealed a significant clustering of silver grains over chromosome 12 bands q23-q24.3, indicating that the gene coding for MYL2 is located in this region.

Cardiomegaly↗
PubMed1992

Variations in alphoid DNA sequences escape detection of aneuploidy at interphase by FISH technique.

The advent of a new staining technique, termed fluorescence in situ hybridization (FISH), allows the rapid identification of the genomic constitution of an individual with aneuploidy even in interphase nuclei through the use of a series of chromosome-specific DNA probes, an approach termed "interphase cytogenetics." However, alphoid DNA sequences of every centromere are polymorphic (heteromorphic), and the number of targeted sequences may be below the detection level of a specific DNA probe, thus escaping detection and resulting in the imprecise identification of the chromosomal constitution at interphase. The limitations associated with the FISH technique have dire consequences which are emphasized here with an example in which the presence of an additional chromosome 21 in two siblings born consecutively with trisomy 21 (Down syndrome) was not detected by "interphase cytogenetics." The copy number of alphoid DNA sequences of one of the paternal chromosomes 21 was low and resulted in discordance between domain numbers at interphase and actual chromosome numbers at metaphase in both children. This is an isolated incident that could have led to a misdiagnosis if FISH were the only test employed. Although the advantages of this technology are undeniably enormous, the present finding has made it apparent that precise standards and reliability of the procedure must be established prior to its routine application.

DNA Probes↗
PubMed1992

Deciphering the fluorescent variability of human genomic heterochromatin by DA/DAPI technique.

A number of selective staining techniques have been utilized to decipher the variability of pericentromeric heterochromatin. One such technique is called DA/DAPI and it is believed to be stain specific. However, we demonstrate otherwise and suggest that pericentromeric regions of all human chromosomes stain positive by DA/DAPI-technique. It must be emphasized that the incidence of DA/DAPI positive stained chromosomes, other than 1, 9, 15, 16 and Y, is a rare occurrence and only a small portion of the pericentromeric region is DA/DAPI positive, as reported here using 50 normal individuals.

Distamycins↗
PubMed1992

The interstitial deletion of bands q33-35 of long arm of chromosome 7: a review with a new case report.

Interstitial or terminal deletion resulting in partial monosomy of various segments of the long arm of chromosome 7 was first recorded over two decades ago. Since then, a number of reports have correlated the severity of clinical manifestations with the length of the deletion involved. However, difficulty remains in defining a so-called "distinct syndrome". We present a new case with the shortest interstitial deletion of the long arm of chromosome 7 bands q33-35, i.e. 46,XX,del(7)(pter----q33::q35----qter). A 4-year-old black female was referred for cytogenetic evaluation due to neurodevelopmental delay. Pertinent physical examination at birth was cleft lip and cleft palate which required corrective surgery. At 2 years of age, a myringotomy tube was inserted for repeated ear infection and a hearing aid was required for conductive deafness. Neurological examination revealed poor eye contact, and severe mental and motor retardation. We reviewed 21 cases of a partial interstitial deletion of varied segments of the long arm of chromosome 7, but we were unable to establish a definite relationship with the deletion of various 7q segments with any specific clinical manifestations.

Adult↗
PubMed1992

Pericentric inversion of chromosome 7 (inv(7) (p22q11.2)) and ring chromosome 8 (r(8) (p23q24.3)) in a girl with minor anomalies.

A 13 year old girl was referred with congenital microcephaly, developmental delay, a prominent nose, highly arched palate, and an apparently low set left ear. She was found to have a pericentric inversion of one chromosome 7 and a ring chromosome 8, 46,XX,inv(7) (pter----p22::q11.23----p22::q11.23----qter), r(8) (p23q24.3). The concurrence of these two abnormalities is a rare event and has not been reported previously.

Abnormalities, Multiple↗
PubMed1992

Tandem duplication of the terminal band of the long arm of chromosome 7 (dir dup (7)(q36----qter)).

We report on a new case of a single band duplication of the long arm of chromosome 7, dir dup (7)(q36----qter). The major manifestations are developmental delay (particularly speech), frontal bossing, macrocrania, and constant drooling. When compared with other cases involving a 7q duplication of various segments, our patient has a few minor anomalies. This case illustrates the genotype/phenotype correlation in a child with a single band duplication which has resulted in duplication of 7q36----qter. A tabulation of reported cases with duplication of various segments of 7q is provided, which may serve as an aid for clinicians.

Abnormalities, Multiple↗
PubMed1992

New dysmorphic features in Rubinstein-Taybi syndrome.

We report a new case of Rubinstein-Taybi syndrome with a hypoplastic right kidney, persistent pulmonary hypertension, and mitral valve regurgitation. Other pertinent features included broad thumbs, broad big toes, syndactyly of the third and fourth fingers bilaterally, beaked nose, broad columella of the nose, patent ductus arteriosus, and motor and mental retardation. The testes were descended. The 3 month old patient had delayed motor and mental development corresponding to a 1 month old infant.

Humans↗
PubMed1992

Cytogenetic evidence for extramedullary blast crisis with t(8;13)(q11;p11) in chronic myelomonocytic leukemia.

A 27-year-old male developed massive generalized lymphadenopathy with chronic myelomonocytic leukemia (CMML) presenting as extramedullary blast crisis mimicking a lymphocytic lymphoma. On presentation, a consistent chromosomal abnormality involving chromosomes 8 and 13, i.e. 46,XY,t(8;13) (q11;p11), was present in lymph node tissue, bone marrow and unstimulated peripheral blood. The appearance of trisomy 21 in addition to the presence of the original cytogenetic abnormality is simply regarded as clonal evolution, i.e. 47,XY,t(8;13)(q11;p11),+21. The importance of the cytogenetics lies in finding the same abnormality in bone marrow and lymph node, adding evidence that the immunologically similar cells in the two sites have arisen from a common progenitor cell. To our knowledge, this novel chromosomal abnormality has not been reported in association with a unique case.

Adult↗