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Biomedical subjects

K Chowdhury

Publications and source records attributed to K Chowdhury.

At least 19 recordsLinked to original sources
PubMed1992

Classification and treatment of zygomatic fractures: a review of 1,025 cases.

The treatment of zygomatic fractures varies among surgeons, and the cosmetic and functional results are frequently less than optimal. A treatment guideline based on a simple classification of zygomatic fractures is presented. The emphasis is placed on the indications for closed and open reduction, consistent methods of three-dimensional alignment and fixation, and the management of concomitant infraorbital rim and orbital floor fractures. Postoperative results with regard to infraorbital nerve and maxillary sinus dysfunction, malar asymmetry, and orbital complications in the treatment of 1,025 consecutive zygomatic fractures are presented.

Adolescent↗
PubMed1992

The ubiquitous transactivator Zfp-38 is upregulated during spermatogenesis with differential transcription.

We describe the complete nucleotide sequence of a full length cDNA clone encoding a new mouse zinc finger protein gene, Zfp-38 and localize it on chromosome 5 by the interspecific backcross analysis. The N-terminal domain of the Zfp-38 protein (64 kDa) contains 358 amino acids and the C-terminal domain of 197 residues encodes 7 zinc fingers. We also present evidence that Zfp-38 is a strong transcriptional activator. The transactivation domain was localized in the non finger region and a fusion protein containing 112 amino acid residues from this region of the Zfp-38 and the DNA binding domain of the yeast Gal 4 protein, very efficiently transactivated the expression of a reporter CAT plasmid, harboring the Gal4 target site. By in situ hybridization and northern blotting technique, the Zfp-38 transcript can be detected at a highly elevated level during spermatogenesis. Its expression accompanies the progression from pachytene spermatocytes to round spermatids. The undifferentiated spermatogonia or the haploid elongated spermatid and the spermatozoa do not show any detectable level of the transcript. Interestingly, other tissues express low levels of a slightly shorter transcript with a different 5' end as determined by RNase protection. The presence of both a transcriptional activating domain and 7 DNA binding zinc fingers, coupled with the cell type(s) specific expression pattern, suggests that Zfp-38 has the potential to regulate transcription during spermatogenesis.

Amino Acid Sequence↗
PubMed1992

Free radicals induce gene expression of NGF and bFGF in rat astrocyte culture.

Hydrogen peroxide (H2O2) is a type of active oxygen species produced mainly in blood by inflammation, ischemia or anoxia. Treatment of rat neonatal cortical astrocytes in culture with 0.2-1.0 mM H2O2 which is lethal for hippocampal neurons, increases nerve growth factor (NGF) and basic fibroblast growth factor (bFGF) mRNA content in a time dependent manner. H2O2 also increases c-fos mRNA expression, which is probably involved in the gene regulation of both NGF and bFGF. Maximal induction was reached after 6 h of incubation (5.7-fold increase in NGF and 2.4-fold induction of bFGF mRNA). Hydrogen peroxide induced bFGF and NGF gene expression suggests that neurotrophic factors in astrocytes could be induced by lesion, consistent with their protective function in the CNS.

Animals↗
PubMed1991

Treatment of 813 zygoma-lateral orbital complex fractures. New aspects.

A 10-year experience with surgical treatment of 813 zygomalateral orbital complex fractures is reviewed. Regardless of the type or severity of the fracture pattern, concomitant fractures of the orbital floor and rim were approached exclusively through the transconjunctival approach without a lateral canthotomy. The advantages of this approach compared with the subciliary access are the avoidance of a visible scar and markedly reduced incidence of postoperative lower eyelid complications such as ectropion and edema. Implants of lyophilized dura or cartilage and autogenous bone were used to reconstruct orbital floor defects. Malar asymmetry is a frequent complication of zygoma fractures resulting from inadequate three-dimensional reduction. Methods for accurate reduction and stabilization, indications for closed and open reduction, and management of the fractured infraorbital rim are emphasized. The indications for miniplates vs wire ligatures for the infraorbital rim are discussed. Long-term follow up and evaluation of the results with regard to the fracture pattern, complications, maxillary sinus dysfunction, and facial and orbital symmetry are presented.

Bone Plates↗
PubMed1990

New type of POU domain in germ line-specific protein Oct-4.

Members of a family of murine octamer-binding proteins interact specifically with the octamer motif, a transcription regulatory element found in the promoter and enhancer regions of many genes. Oct-4 is a maternally expressed protein that is also present in the pre-implantation mouse embryo. Although many regulatory proteins are expressed in post-implantation embryos, transcription factors regulating pre-implantation processes have remained elusive. The Oct-4 gene is therefore a prime candidate for an early developmental control gene. Here we report the complementary DNA cloning of the mouse Oct-4 gene, and the characterization of the encoded protein(s) by sequential in vitro transcription, translation, DNA-binding and protease-clipping analysis. Deletion analysis shows that the DNA-binding activity is mediated by a POU domain encoded in an open reading frame corresponding to a 324-amino-acid protein. Sequence comparison with known POU domains reveals that Oct-4 is a novel member of the POU-family.

Animals↗
PubMed1990

Extracranial primitive neuroectodermal tumor of the head and neck.

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.

Adolescent↗
PubMed1990

Zinc finger protein gene complexes on mouse chromosomes 8 and 11.

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.

Animals↗
PubMed1990

Pax2, a new murine paired-box-containing gene and its expression in the developing excretory system.

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.

Amino Acid Sequence↗
PubMed1990

Pax8, a murine paired box gene expressed in the developing excretory system and thyroid gland.

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.

Amino Acid Sequence↗
PubMed1989

Structure, expression and chromosomal localization of Zfp-1, a murine zinc finger protein gene.

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.

Amino Acid Sequence↗
PubMed1988

Specific and ubiquitous expression of different Zn finger protein genes in the mouse.

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.

Amino Acid Sequence↗
PubMed1988

Moratorium call.

Explore the source record for details and available documents.

Base Sequence↗
PubMed1988

The primary structure of the murine multifinger gene mKr2 and its specific expression in developing and adult neurons.

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.

Amino Acid Sequence↗
PubMed1988

A mouse gene homologous to the Drosophila gene caudal is expressed in epithelial cells from the embryonic intestine.

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.

Amino Acid Sequence↗
PubMed1988

Post-tonsillectomy and adenoidectomy hemorrhage.

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.

Adenoidectomy↗
PubMed1987

A multigene family encoding several "finger" structures is present and differentially active in mammalian genomes.

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.

Amino Acid Sequence↗
PubMed1987

Isolation and characterization of murine transcriptional control elements using a "shotgun" method.

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.

Acetyltransferases↗