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Biomedical subjects

K Madan

Publications and source records attributed to K Madan.

At least 19 recordsLinked to original sources
PubMed1995

Paracentric inversions: a review.

This review of paracentric inversions in man includes what we know of the behaviour and reproductive consequences of paracentric inversions from other species. Observations of naturally occurring inversions in several species of plants and animals and results of experiments with mutagenically induced inversions in the mouse are discussed. From a review of 184 cases, it is concluded that most of the paracentric inversions in man are harmless and that the risk of heterozygotes having a child with an unbalanced karyotype is low. However, in some cases, it is difficult, if not impossible, to distinguish between a paracentric inversion and a paracentric insertion, the risk in the latter case being about 15%. Caution is also necessary in interpreting the results of prenatal diagnosis for heterozygotes of paracentric inversions, because of the possibility of a variety of unpredictable unbalanced chromosome products.

Chromosome Inversion↗
PubMed1992

Intrachromosomal insertions: a case report and a review.

We describe the phenotype of a child having a recombinant chromosome 3 with a duplication 3q13.2----q25 derived from a paternal inv ins(3)(p25.3q25q13.2). A review of 27 reported cases of intrachromosomal insertions has revealed that for a carrier of intrachromosomal insertion the risk of a child with an unbalanced karyotype is 15%. This risk may be higher for particular insertions. The recombinant chromosome can have a duplication or a deletion of different segments depending on whether the insertion is direct or inverted, paracentric or pericentric, and whether there is meiotic crossing over in the inserted or the interstitial non-inserted segment. Several of the insertions have been difficult to interpret and some of them have been mistaken for paracentric inversions. Caution is therefore indicated in interpreting parental karyotypes of a child with a deletion or a duplication, particularly if it is interstitial. This is because, whereas a risk of recurrence of a child with an unbalanced karyotype is low in de novo cases and for carriers of paracentric inversions, it is high for carriers of insertions.

Abnormalities, Multiple↗
PubMed1990

Paracentric inversion inv(11)(q21q23) in The Netherlands.

We report the result of investigations from 20 families with 72 carriers of the paracentric inversion inv(11)(q21q23) in the Netherlands. There is no increase in the rate of spontaneous abortions among carriers of the inversion or their partners. Also, so far, there are no children with recombinant chromosomes arising from the inversion. It is doubtful whether prenatal diagnosis would be helpful to carriers of this inversion. The results of the genealogy study and geographical distribution are discussed; it is suggested that all the families have arisen from a single mutation.

Abortion, Spontaneous↗
PubMed1987

Premature centromere division (PCD): a dominantly inherited cytogenetic anomaly.

We describe a family with an increased frequency of cells with premature centromere division (PCD) of all chromosomes in four phenotypically normal individuals. This familial PCD phenomenon is apparently different from the well-described PCD of the X chromosome and from the centromere splitting in cells of patients with Roberts syndrome. Implications for genetic counseling are discussed.

Centromere↗
PubMed1987

Human alpha-globin maps to pter-p13.3 in chromosome 16 distal to PGP.

Fibroblasts from a fetus with an unbalanced karyotype 46(XY), -16,+(16qter-16p13.3::4q31.1-4qter) were found to possess only one allele at the 3' hypervariable region (3'HVR) close to the alpha-globin locus and two alleles at the PGP locus. This places the alpha-globin locus at the very tip of 16p, distal to PGP.

Chromosome Banding↗
PubMed1987

Double-minute chromatin bodies in HL-60 leukemia cells sensitive and resistant to differentiation inducing agents.

We studied the chromosome characteristics of HL-60 promyelocytic leukemia cells sensitive and resistant to differentiation inducing agents (DI). The karyotypic analysis of sensitive (HL-60 S) and resistant (HL-60 R) cells revealed the presence of identical chromosome abnormalities such as loss of chromosomes 5, 9, 10, 14, 16, 17 and X; and gain of chromosome 18. HL-60 S and HL-60 R cells also share five common markers. The difference between the two cell lines consisted essentially of the loss of an unidentifiable chromosome segment in the HL-60 R cell line. In addition, the two sublines showed marked differences in the content of double-minute chromatin bodies (DM), which were abundant in HL-60 S but rarely found in HL-60 R cells. Contrary to a previous report by others, there was no evidence of chromosome rearrangement of the DM as homogeneously stained regions (HSR) or abnormally banding regions (ABR) in the resistant HL-60 R cells. The presence of DM as an expression of gene amplification may be of relevance in the determination of susceptibility of HL-60 cells to DI.

Cell Differentiation↗
PubMed1987

[Phenotypically a boy, genotypically a girl; the 46,XX male syndrome].

A three and a half years old boy with obesity, a small penis, and cryptorchism appeared to have a 46,XX karyotype in cultured peripheral lymphocytes. The clinical features of this rare syndrome and theories of etiology of 46,XX male subjects are discussed. Furthermore we stress the importance of thorough investigation in case of non-palpable testicles in an individual having a penis.

Child, Preschool↗
PubMed1984

Familial benign hypercalcaemia (FBH; McK. No. 14598, 1983): linkage studies in a large Dutch family.

By screening 27 hypercalcaemic and 21 normocalcaemic subjects in a large Dutch pedigree with familial benign hypercalcaemia (FBH; McK. No. 14598) (McKusick 1983) for more than 35 genetic markers, it was found that linkage of FBH can be excluded at about 25 centimorgans (cM) from GM, 20 cM from ABO, 15 cM from MNS and HLA, 10 cM from JK and PI, and 5 cM each from ACP1, AK1, ADA, GPT1, and PGP.

Female↗
PubMed1984

Mosaic tetrasomy 21 in a male child.

We report a three-year-old male child with dysmorphy, severe mental retardation and a mosaic tetrasomy 21 caused by an extra F-like chromosome composed of two long arms of chromosome 21. We have compared this unusual case with two other similar published case reports. Hypotheses to account for the origin of the abnormal chromosome and the mosaicism are presented and discussed.

Abnormalities, Multiple↗
PubMed1984

Paracentric inversions in man.

We have reviewed 50 cases of paracentric inversions. Of these 34 were familial with 62 phenotypically normal carrier relatives. Twenty of the 50 were discovered fortuitously. There were two reports of children with easily recognised unbalanced karyotypes resulting from a paracentric inversion in one of the parents. The vast majority of paracentric inversions are harmless. The risk of abnormal children for paracentric inversion heterozygotes is low but increases with the finding of recurrent abortions or abnormal children or both in other carriers in the family. We emphasise the need for caution in interpreting the results of antenatal diagnosis because of the variety of unexpected unbalanced chromosome types that can result from a paracentric inversion, and the difficulty in recognising, with confidence, minute differences (for the detection of which very high resolution banding is required) between apparently similar parental and fetal inversions.

Abortion, Habitual↗
PubMed1983

Balanced structural changes involving the human X: effect on sexual phenotype.

Reports of 107 cases (89 females and 18 males) with balanced X-autosome translocations and 11 cases with pericentric inversions (and their families) have been reviewed. Of the 78 informative females, 36 were infertile and had an X-breakpoint in the segment Xq13-26. Thus the existence of the critical segment has been amply confirmed by this review. However the finding of three normal fertile females with deletion of a part or the whole of this segment suggests that it is not the break in the critical segment, as was first thought, but rather the contact between loci in the critical segment and loci external to it that is responsible for the abnormal sexual phenotype. Six females were exceptions to the critical region hypothesis. The X-breakpoints in these were in the critical region and yet each had had one or more children. Three of the six women (two inversions and one translocation carriers) were not wholly normal as they suffered from menstrual cycle disorder, secondary sterility and/or early menopause. Four of the six (including the three true exceptions) had a breakpoint in band Xq22. It is possible that there are two critical segments within Xq13-26 separated by a small segment in band Xq22. Seven of the nine adult male carriers of the balanced X-autosome translocations were infertile. Even from this limited number of cases it appears that male carriers of X-autosome translocations are likely to suffer from a disturbance of spermatogenesis as is the case in mouse and drosophila. Male carriers of X-inversions do not necessarily suffer from infertility. Results from one family with X-inversion suggest that some sort of a position effect in the X affecting the sexual phenotype may also be operating in the male.

Chromosome Aberrations↗
PubMed1981

X-autosome translocation with a breakpoint in Xq22 in a fertile woman and her 47,XXX infertile daughter.

An unusual case is presented of a fertile woman heterozygous for a balanced X-autosome translocation t(X;12)(q22;p12) with a break-point (Xq22) in the critical region of the X chromosome. The karyotypes of her daughter, who is infertile, and one of her two sons are 47,XXX,t(X;12)(q22;p12) and 46,XY,t(X;12)(q22;p12) respectively. The literature on balanced X-autosome translocations in males and females involving both arms of the X chromosome is reviewed. All 23 of the 36 cases of females with balanced Xq-autosome translocation, that exhibited gonadal failure have a break-point between bands Xq13 and Xq26.U

Adult↗
PubMed1981

Ring-18 and isopseudodicentric-18 in the same child: a hypothesis to account for common origin.

A child with two cell lines, one with a ring 18 and the other with an isodicentric 18 with a suppressed centromere is described. A hypothesis that could account for a common origin of the two cell lines is presented and discussed. The clinical features of this child were compatible with some of the features for each of the syndromes of 18p-, 18q-, and trisomy 18 as described in the literature.

Brain Diseases↗
PubMed1979

Three cases of sex chromosome mosaicism with a nonfluorescent Y.

Clinical and cytogenetic findings in three patients mosaic for sex chromosomes (45,X0/46,XY; 45,X0/46,XY/46,XYq-, and 45,X0/46,XY/46,XYY), each with a nonfluorescent Y, are presented. Hypotheses for the origin and effect of these chromosome constitutions are discussed.

Adult↗