Biomedical subjects
Publications and source records attributed to K Chowdhury.
Malignant peripheral neuroectodermal tumors are rare neoplasms of the head and neck. We describe a case of a teenage girl presenting with this neoplasm in the head and neck. The clinical histological and ultrastructural features are reviewed and presented, along with guidelines for the management of this highly aggressive neoplasm.
Two murine homologs of the Drosophila Krüppel gene, a member of the gap class of developmental control genes that encode a protein with zinc fingers, were mapped to mouse chromosomes 8 and 11 by using somatic cell hybrids and an interspecific backcross. Surprisingly, both genes were closely linked to two previously mapped, Krüppel-related zinc finger protein genes, suggesting that they are part of gene complexes.
The murine genome contains multiple genes with protein domains homologous to the Drosophila paired box, present in certain segmentation genes. At least one of these murine paired box (Pax) genes is associated with a developmental mutation. This report, in conjunction with the accompanying paper, describes a second member of this gene family, Pax2, that is also expressed during embryogenesis. Two overlapping cDNA clones were isolated and sequenced. At least two forms of the Pax2 protein can be deduced from the cDNA sequence. In addition to the highly conserved paired domain, an octapeptide sequence is located downstream. Expression of Pax2 is primarily restricted to the developing embryo in the excretory and central nervous systems. The transient nature of Pax2 expression during kidney organogenesis correlates with polarization and induction of epithelial structures and may indicate an important morphogenetic role for this gene.
Several mouse genes designated 'Pax genes' contain a highly conserved DNA sequence homologous to the paired box of Drosophila. Here we describe the isolation of Pax8, a novel paired box containing clone from an 8.5 day p.c. mouse embryo cDNA library. An open reading frame of 457 amino acids (aa) contains the 128 aa paired domain near the amino terminus. Another conserved region present in some other paired box genes, the octapeptide Tyr-Ser-Ile-Asn-Gly-Leu-Leu-Gly, is located 43 aa C-terminal to the paired domain. Using an interspecies backcross system, we have mapped the Pax8 gene within the proximal portion of mouse chromosome 2 in a close linkage to the surf locus. Several developmental mutations are located in this region. In situ hybridization was used to determine the pattern of Pax8 expression during mouse embryogenesis. Pax8 is expressed transiently between 11.5 and 12.5 days of gestation along the rostrocaudal axis extending from the myelencephalon throughout the length of the neural tube, predominantly in two parallel regions on either side of the basal plate. We also detected Pax8 expression in the developing thyroid gland beginning at 10.5 days of gestation, during the thyroid evagination. In the mesonephros and metanephros the expression of Pax8 was localized to the mesenchymal condensations, which are induced by the nephric duct and ureter, respectively. These condensations develop to functional units, the nephrons, of the kidney. These data are consistent with a role for Pax8 in the induction of kidney epithelium. The embryonic expression pattern of Pax8 is compared with that of Pax2, another recently described paired box gene expressed in the developing excretory system.
Zinc finger proteins (Zfp) are encoded by a large family of genes present in many organisms including yeast and human. Some of them are transcriptional activators and bind specifically to DNA by zinc mediated folded structures commonly known as zinc fingers. The Drosophila Krüppel (Kr) is a segmentation gene and encodes a zinc finger protein. Using a probe from the finger domain of Kr, we have isolated a structurally related gene Zfp-1 from the mouse. In this paper, we report the complete nucleotide sequence of two cDNA clones and the amino acid sequence deduced from them. The putative Zfp-1 protein contains in addition to 7 zinc fingers, two helix-turn-helix motifs. During murine embryogenesis, the Zfp-1 was found to express at a peak level in day 12 embryos. The ubiquitously expressed Zfp-1 gene is located in the 16q region on mouse chromosome 8, between the uvomorulin and the tyrosine amino transferase genes.
Zinc finger proteins (Zfp) are members of a multigene family encoding Zn mediated nucleic acid binding proteins. They have been isolated from various organisms including yeast, Drosophila, Xenopus mouse and human. All Zfp share the 28-30 amino acid long finger repeats containing conserved residues at specific positions. Some of these proteins have been identified as transcriptional regulatory factors. In this paper, we describe the isolation, DNA sequence determination and the expression pattern in developing embryos and adult tissues of 3 new members of the mouse Zfp. All of them are expressed as multiple transcripts. Unaltered level of mkr5 expression could be detected in 10-15 day whole embryo RNAs but its level started to decrease from day 16. In the adult animal, predominant expression was detected only in the ovary. In contrast, mkr3 and 4 were expressed at a constant level in all embryos and tissues tested. These data suggest the presence of both tissue specific and ubiquitious Zfp in the mouse.
The complete amino acid sequence of the murine finger-containing gene mKr2 was determined. On the basis of sequence similarities in the repeated finger domain, mKr2 belongs to the same class of developmentally expressed genes as Drosophila Krüppel and hunchback. The presence of metal ion and DNA-binding finger domains similar to those identified in TFIIIA supports the hypothesis that these genes regulate transcription. mKr2 transcripts are restricted to neurons in the central and peripheral nervous system of adult animals. Furthermore, mKr2 transcripts can be detected in all the major structures of the developing nervous system during embryogenesis. The data are consistent with the hypothesis that mKr2 is a regulatory factor required for the differentiation and/or phenotypic maintenance of neurons.
A mouse gene, Cdx-1, was isolated from an embryonic cDNA library using a Drosophila caudal gene probe. The deduced amino acid sequence of Cdx-1 contains conserved sequence domains along the entire gene, as well as a highly conserved caudal-type homeo box. A structural comparison suggests a common ancestral origin of mouse Cdx-1 and Drosophila caudal. The expression of Cdx-1 during embryogenesis was analyzed by Northern blotting and in situ hybridization. Cdx-1-specific transcripts are localized in the epithelial lining of the intestines beginning at 14 days' gestation. The expression of Cdx-1 in the intestine continues into adulthood, but cannot be detected in any other tissues. The Cdx-1 gene is the first homeo-box-containing gene expressed in cells derived from the embryonic endoderm.
This is a retrospective review of 6842 tonsillectomies and adenoidectomies performed over a seven-year period at the Montreal Children's Hospital. The total incidence of postoperative bleeding was 2.5%. The incidence of primary post-tonsillectomy hemorrhage was 1.0%, with 78% of these children having developed bleeding within 12 hours of surgery. The overall incidence of secondary post-tonsillectomy hemorrhage was 1.2%. Twenty-nine percent of children with primary hemorrhage required a second general anesthetic, and 40% required blood component transfusion. Eight percent of children with secondary hemorrhage required a second general anesthetic and 24% received transfusions. Based on these findings, primary and secondary hemorrhage can be classified further into major and minor. The criteria for a major post-tonsillectomy hemorrhage are: requirements of a general anesthetic to control and repair the bleeding, or blood loss that is sufficient to require blood component transfusion therapy. The relevance of these findings with regard to outpatient adenotonsillectomies is discussed.
Mouse genomic DNA contains multiple copies of sequences homologous to the Drosophila "Krüppel," a member of the "gap" class of developmental control genes of the fruit fly. The most interesting aspect of the homologous region is that, like Xenopus TFIIIA, it contains multiple finger-like folded domains capable of binding to nucleic acids. We have isolated six individual phages from a mouse genomic library on the basis of their DNA homology to Krüppel finger-coding probes, and describe here the DNA sequence and expression of two such clones containing finger-like structures. Upon differentiation of mouse teratocarcinoma cell line F9 with retinoic acid and cAMP, the expression of both genes was drastically reduced, and in one instance was undetectable. Each of the several other eukaryotic DNAs analyzed contained multiple copies of homologous genes with putative finger structures, indicating the presence of a finger-containing multigene family in higher organisms.
In an attempt to identify novel promoter/enhancer elements in cellular genomes, an experimental "shotgun" system was designed and tested. Fragments of mouse cellular DNA were cloned into various plasmid vectors whose common reporter gene facilitates the identification of regulatory sequences. Of 120 clones analyzed, we identified one whose insert markedly increases transcriptional activity of the constructions. This genomic fragment contains a promoter element and exhibits enhancer-like properties in fibroblast cell lines of different species. Genomic analysis shows the fragment is a member of a middle repetitive sequence family, containing a 170-bp sequence with extreme purine/pyrimidine asymmetry. This stretch of cellular DNA is very sensitive to S1 nuclease digestion when present in superhelical plasmids. Isolation and characterization of sequences homologous to this fragment suggest a relationship between transcriptional activity and S1 sensitivity.
In order to gain insight into the function of the Hox 1.1 gene, we studied the expression of the murine homeo box gene product, the Hox 1.1 protein. Monoclonal antibodies were raised against synthetic peptides of the Hox 1.1 protein to study the localization and expression pattern of this protein under various culture conditions. By means of indirect immunofluorescence we localized the Hox 1.1 protein to the nucleus in differentiated F9 and NIH 3T3 cells. During mitosis the protein was found to be associated with chromatin. Confluent NIH 3T3 cells harbored little if any Hox 1.1 protein. After "wounding" the cells in this confluent monolayer, we observed an induction of the expression of the Hox 1.1 protein. However, addition of insulin to F9 and contact-inhibited NIH 3T3 cells led to an increase of the Hox 1.1 RNA and protein expression. Thus, the induction of the Hox 1.1 protein is associated not only with the differentiation of embryonal carcinoma (EC) cells, but may also correlate with stages of cell growth.
The telangiectatic variant of osteogenic sarcoma is rare. Its biologic behaviour, treatment and prognosis are controversial. The case of a 15-year-old girl with this tumour is described. Both the location and clinical behaviour of the tumour were unusual. The tumour, which involved the distal ulna, was initially treated by a limited resection of the distal 8 cm of ulna. Sixty-nine months later the tumour recurred locally; there was no evidence of metastases. The forearm was amputated and the patient was then treated aggressively by chemotherapy. She was well 42 months later. This case illustrates the tendency for telangiectatic osteosarcoma to recur locally if it is not radically excised.
Explore the source record for details and available documents.
Functional analysis of the transcriptional control region of the polyoma (Py) mutant F9-1 reveals that the mutation is located in a region of Py DNA required for at least two functions. First, an enhancer element which includes the F9-1 mutation was characterized by deletion analysis. This element, described previously as enhancer B is essential for viral early gene expression in F9 stem cells whereas enhancer A is unnecessary for transcriptional activity in embryonal carcinoma (EC) cells. Second, a CCACCC motif, present twice in the 3' part of enhancer B is also required in cis for the response to a heterologous enhancer. This suggests that a promoter element is present in this region of the polyoma genome which overlaps Py enhancer B. We also demonstrate the enhancement of the polyoma early promoter activity in F9 stem cells by MSV sequences. The significance of these observations is discussed.
A murine homeo box (m6-12) known to be expressed during differentiation of embryonal carcinoma cells lies within a cluster of homeo boxes located in 30 kilobase pairs of genomic DNA. We have established the organization of the boxes within this complex, as well as the nucleotide sequence of a second box, m5-4. Similar to the m6-12 box, expression of novel m5-4 transcripts is induced upon differentiation of embryonal carcinoma cells. Transcripts of genes containing m6-12 were found in embryonic tissue during almost all stages of prenatal development studied, whereas expression of m5-4 was detected only in 12 day embryonic tissue. Finally, we have described the differential expression of these homeo-box-containing regions in various adult tissues.
We have identified a strain of polyomavirus, Py(L), which is unusual in causing acute morbidity and early death after inoculation of newborn mice. We determined that these animals died of kidney failure associated with extensive, virus-mediated destruction of renal tissue. Interestingly, the Py(L) strain infects baby mouse kidney cell cultures more efficiently than do other strains.