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Biomedical subjects

C Nguyen

Publications and source records attributed to C Nguyen.

At least 145 records · Page 8Linked to original sources
PubMed1990

Composite affinity sorbents and their cleaning in place.

Making large-scale affinity sorbents that are reusable under acceptable hygienic conditions implies specific treatments for cleaning in place with known aqueous solutions of chemical agents. However, common agents such as sodium hydroxide are frequently considered too drastic for the stability of macromolecular biologically active immobilized ligands. According to a large series of trials, it was found that only a mixture of sodium hydroxide and ethanol was actually effective in sterilizing a sorbent in a single step. When hydroxide or an ethanol-acetic acid mixture were used alone, they were not totally efficient in the inactivation of sporulated Bacillus subtilis. Conversely, they were efficient when used sequentially. All these solutions were able to remove pyrogens from chromatographic sorbents. As the sterilizing solutions contained a certain amount of ethanol, the most suitable chromatographic affinity sorbents had to be based on an incompressible matrix. When washing an affinity silica sorbent that had proteins as ligands with solutions such as sodium hydroxide, ethanol-acetic acid or ethanol-sodium hydroxide, it was found that certain sorbents were able to tolerate the treatments without a noticeable decrease in their biochemical activity.

Acetates↗
PubMed1990

The 11q13 amplicon of a mammary carcinoma cell line.

Fifteen to 20% of breast carcinomas show amplification of genes located at 11q13. The HST/FGFK and INT2 fibroblast growth factor (FGF)-related genes and the BCL1 locus are usually present in the amplification units. We have investigated the structure and chromosomal location of the 11q13 amplicon of the MDA-MB-134 mammary carcinoma cell line by using in situ chromosomal and pulsed field gel hybridizations. The results indicate that a limited number of amplification units are involved in the constitution of an extended chromosomal region located on 11q. These units do not show any important rearrangement over rather large distances around the HST/INT2 and BCL1 loci.

Blotting, Northern↗
PubMed1990

The gene encoding L1, a neural adhesion molecule of the immunoglobulin family, is located on the X chromosome in mouse and man.

The murine and human genes for the L1 neural adhesion molecule were shown to lie on conserved regions of the X chromosome to which genes responsible for several neuromuscular diseases have been mapped and which are adjacent to the fragile site (FRAXA) associated with mental retardation. By pulsed-field gel mapping we have demonstrated physical linkage between the L1 gene and other genes located in Xq28: L1 lies between the eye pigment RCP, GCP locus and the glucose-6-phosphate dehydrogenase (G6PD) gene. This location is compatible with the implication of the L1 molecule in one of the X-linked neuromuscular diseases mapped to this region.

Amino Acid Sequence↗
PubMed1990

Canine intervertebral disks: correlation of anatomy and MR imaging.

Because the structure, maturation, and degeneration of canine intervertebral disks resemble those of humans, the authors developed a model of acute intervertebral disk degeneration in dogs. Herniated disks of 18 dogs were examined with magnetic resonance (MR) imaging and then sectioned with a freezing microtome. On the basis of their morphologic appearance in the freezing microtome sections, most of the lumbar intervertebral disks could be categorized as one of six types. Each type has characteristic features and a distinctive appearance on MR images. Findings of this study--including decreased signal intensity from the intervertebral disk, altered signal intensity in contiguous bone marrow, bulging of the anulus fibrosus, herniation of the nucleus pulposus, and contrast enhancement after intravenous administration of gadolinium diethylenetriaminepentaacetic acid (DTPA)--resemble observations from human clinical studies. Classification of degenerating disks and identification of MR imaging characteristics of each type may improve the interpretation of MR images and recognition of early disk degeneration in humans.

Animals↗
PubMed1990

The inguinal sarcoma: a review of five cases.

A review of five patients who presented during a 3-year period with sarcoma arising in the inguinal canal demonstrated that the lesion is frequently mistaken for a hernia. In three of the patients incomplete excision of the inguinal mass resulted in spread of the lesion beyond the inguinal canal. The authors suggest that neoplastic lesions discovered in the inguinal canal should be evaluated by a small incisional biopsy followed by wide resection if sarcoma is confirmed on pathological examination. Preoperative irradiation and re-excision should be considered if widespread microscopic disease remains after excisional biopsy.

Adult↗
PubMed1989

Molecular mapping of the human T cell receptor gamma (TRG) genes and linkage of the variable and constant regions.

In the human T cell receptor gamma (TRG) locus, fourteen variable (TRGV) genes belonging to four subgroups have been identified upstream of two constant region (TRGC) genes. Three joining segments, JP1, JP and J1, have been localized upstream of TRGC1, and two others, JP2 and J2, upstream of TRGC2. In this report, we demonstrate that a unique Xho I fragment of 120 kilobases (kb) contains the fourteen TRGV genes and that the hybridization of that fragment in pulsed-field gel electrophoresis (PFGE) allows linkage of the variable region to the constant region locus. We also show that the variable and the constant regions are remarkably close to each other since the distance between V11, the most 3' V gamma gene, and JP1, the most 5' J gamma segment, is only 16 kb. With its 14 V gamma genes, spanning 100 kb, the two C gamma genes and 5 joining segments covering less than 40 kb and only 16 kb separating the most 3' V gene from the most 5' J segment, the human TRG locus spans 160 kb of genomic DNA and represents a particularly condensed locus compared to the other rearranging gene loci.

Amino Acid Sequence↗
PubMed1989

Large-scale mapping and chromosome jumping in the q27 region of the human X chromosome.

We have used pulsed field gel electrophoresis for further physical mapping studies in the q27 region of the human X chromosome. We show that the DXS 102 locus and the F9 gene are separated by only 300 kb despite a genetic distance of 1.4 cM; this linkage orients our large-scale map and shows that the mcf.2 transforming sequence is telomeric to F9. A BssHII complete-digest jumping library was used to jump toward the DXS 105 locus; a 130-kb jump was achieved and the corresponding "linking clone" was obtained.

Blotting, Southern↗
PubMed1989

In situ hybridization and pulsed-field gel analysis define two major minisatellite loci: 1q23 for minisatellite 33.6 and 7q35-q36 for minisatellite 33.15.

The two classical minisatellite probes, 33.6 and 33.15, were used for in situ hybridization to human metaphase chromosomes. Surprisingly, a single major hybridization peak was observed with each probe, respectively at 1q23 for 33.6 and 7q35-q36 for 33.15. Hybridization to human DNA cleaved with "rare-cutter" enzymes and fractionated on pulsed-field gels also showed a fairly simple, largely monomorphic pattern which allows chromosomal assignment using somatic cell hybrids. Differences in hybridization stringency and degree of resolution account for most of the discrepancy between these results and the accepted view of minisatellites, i.e., a large number of unlinked loci spread over the genome. Our results nevertheless indicate the existence of particularly large and homologous loci on a particular chromosome for each of these probes.

Blotting, Southern↗
PubMed1989

High tibial osteotomy compared with high tibial and Maquet procedures in medial and patellofemoral compartment osteoarthritis.

The effect of adding the Maquet tibial tubercle elevating procedure to a valgus high tibial osteotomy (HTO) in combined medial and patellofemoral disease had not been established. This prospective study evaluates clinically and roentgenographically the use of this osteotomy combination versus HTO alone in dual-compartment arthritis. Forty-four patients (46 knees) with dual-compartment disease from 1979 to 1984 were evaluated. Twenty-two patients were treated with 23 HTOs by a senior surgeon, and 22 were treated with 23 combined procedures by another surgeon. The two groups were matched according to age, sex, and preoperative clinical and roentgenographic disability. The minimum follow-up period was two years. All had more than 5 degrees valgus alignment at the follow-up evaluation, with an average of 11.2 degrees in the HTO group and 10.2 degrees in the combined osteotomy group. A modified Hospital for Special Surgery assessment (maximum, 100 points) was used with an optimum pain score of 30 points. All were followed roentgenographically with grading of the three knee compartments. In both groups, the total and pain scores improved significantly postoperatively. There was no statistical difference between the two groups in terms of mean postoperative femorotibial shaft alignment or clinical and roentgenologic outcome. Although HTO was a good procedure for pain relief for dual-compartment disease, the addition of Maquet procedure did not improve the results.

Aged↗
PubMed1988

CpG islands and HTF islands in the HLA class I region: investigation of the methylation status of class I genes leads to precise physical mapping of the HLA-B and -C genes.

We have investigated the accessibility of the 5' CpG rich sequences (CpG islands) present in the 5' region of most if not all HLA class I genes to methylation sensitive rare cutter enzymes. We show that for HLA-A, -B, -C genes and a few other (but not all) class I sequences these CpG islands are unmethylated and therefore constitute HTF islands (CpG rich, unmethylated regions of DNA, usually associated with expressed genes). We then map precisely the HTF islands of the HLA-B and HLA-C genes and determine that they are separated by 130 Kb (in agreement with genetic data) and that these two genes are in the same transcriptional orientation on the chromosome.

Chromosome Mapping↗
PubMed1988

The chromosome region containing the highly polymorphic HLA class I genes displays limited large scale variability in the human population.

The large-scale organization and polymorphism of the HLA class I region was investigated by pulsed field gel (PFG) fractionation of DNA from various HLA-typed cell lines cleaved by different 'rare cutter' restriction enzymes, followed by hybridization with 'general' and locus-specific HLA probes. Results indicate that (i) most HLA class I sequences are contained in a 340 kb MluI DNA fragment which also carries the HLA-A gene; (ii) HLA-A, -B and -C genes are present on different fragments bounded by 'HTF islands' (CpG-rich, unmethylated DNA regions containing multiple sites for 'rare cutter' enzymes) which generally coincide with the 5' regions of expressed genes; and (iii) very little fragment size polymorphism is seen, implying that expansion/contraction events in the HLA class I region due to unequal crossing over (as documented in the mouse class I system) are infrequently found in the human population.

Chromosome Mapping↗
PubMed1988

The FGF-related oncogenes hst and int.2, and the bcl.1 locus are contained within one megabase in band q13 of chromosome 11, while the fgf.5 oncogene maps to 4q21.

Prompted by the observed co-amplification at the DNA level of the int.2 and hst fibroblast growth factor-related oncogenes in some tumor cells, we have investigated the precise localization of these two loci known to reside in band q13 of chromosome 11. We demonstrate by pulsed field gel analysis that these two genes are separated by only 40 kb, locate three HTF islands in their neighbourhood, and show that the bcl.1 locus (translocation breakpoint in B-cell proliferative malignancies) is not more than 1050 kb away. We also show that the fgf.5 gene which belongs to the same family is not part of this cluster and is located in band q21 of chromosome 4.

Cell Line↗
PubMed1987

Large scale physical mapping in the q27 region of the human X chromosome: the coagulation factor IX gene and the mcf.2 transforming sequence are separated by at most 270 kilobase pairs and are surrounded by several 'HTF islands'.

In spite of the large amount of genetic data obtained on the X chromosome and of the availability of many cloned sequences little is known about the physical map of this chromosome. The construction of large-scale restriction maps is now possible with pulsed field gel methods and data has recently been obtained in the region of band Xq28. We present here results of physical mapping in the Xq27 region, i.e. proximal to the fragile site at Xq27.3 associated with mental retardation, and show physical linkage between the coagulation factor IX gene and the mcf.2 transforming sequence recently localized to Xq27. Our data also indicate partial methylation of some sites in this region, and locate several 'HTF islands', i.e. CpG-rich, unmethylated sequences, containing several sites for 'rare cutter' enzymes, which are believed to be associated with expressed 'housekeeping' genes.

Base Composition↗