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Biomedical subjects

G A Brown

Publications and source records attributed to G A Brown.

At least 19 recordsLinked to original sources
PubMed1998

Prostatic adenocarcinoma diagnosed by prostate-specific antigen analysis of pleural fluid.

Adenocarcinoma of the prostate may result in a malignant pleural effusion. However, most of these cases involve patients with either a known primary prostate cancer or radiographic evidence of pulmonary metastases. Occasionally, the initial diagnosis of prostate cancer is made because of prostate-specific antigen (PSA) staining cells in the pleural fluid. We report a case of adenocarcinoma of the prostate that was suspected only because of an elevated PSA in the pleural fluid in a patient who lacked malignant cytology, a history of prostate cancer, and radiographic evidence of pulmonary disease.

Adenocarcinoma↗
PubMed1997

Enx (Hox11L1)-deficient mice develop myenteric neuronal hyperplasia and megacolon.

The isolated homeobox gene Enx (Hox11L1) is expressed in enteric neurons innervating distal ileum, and proximal and distal colon. Enx-deficient mice develop megacolon with massive distension of the proximal colon. The number of myenteric ganglia, total neurons per ganglion, and NADPH diaphorase presumptive inhibitory neurons per ganglion are increased in the proximal and distal colon, but decreased in the distal ileum of all Enx-/- mice. Enx-/- mice provide a model for human neuronal intestinal dysplasia (NID), in which myenteric neuronal hyperplasia and megacolon are seen. These results suggest that Enx is required for the proper positional specification and differentiative cell fate of enteric neurons.

Animals↗
PubMed1996

Retinoic acid-mediated decrease of G (alpha S) protein expression: involvement of G (alpha S) in the differentiation of HL-60 myeloid cells.

The amount of the heterotrimeric G protein subunit G (alpha S) decreases after the induction of human myeloblastic leukemia HL-60 cells to become granulocyte-like cells in the presence of retinoic acid (RA). Compared to untreated control cells, HL-60 cells expressed decreased levels of G (alpha S) protein and mRNA levels after addition of RA to the cultures as shown by immunoblot and Northern blot analysis. The reduction of the G (alpha S) protein in HL-60 cells by antisense RNA expression was associated with (i) decreased cell doubling time; (ii) induction of a granulocyte-like phenotype; (iii) and expression of a surface marker characteristic of myeloid differentiation. Expression of a constitutively active mutant G (alpha S) (Q227L) in HL-60 cells blocked RA-induced differentiation. In contrast, treatment with forskolin, prostaglandin E2, or 8-bromo-cyclic AMP, which increase intracellular cyclic AMP (cAMP) levels, did not inhibit the RA-mediated differentiation process. No changes in cAMP levels occurred in response to RA. The present study provides insights into the involvement of G (alpha S) protein in growth regulation during differentiation of the human myeloid cell line HL-60. These data suggest that in HL-60 human myeloid cells RA-mediated decrease of G (alpha S) plays a critical role in the regulation of differentiation which is independent of intracellular cAMP.

Adenylyl Cyclases↗
PubMed1996

Fixation strength of interference screw fixation in bovine, young human, and elderly human cadaver knees: influence of insertion torque, tunnel-bone block gap, and interference.

A failure analysis of interference screw fixation was performed to test the hypothesis that bovine and/or elderly human cadavers are appropriate models for bone-patellar tendon-bone anterior cruciate ligament (ACL) reconstruction fixation studies. Failure mode is an important criterion for validating experimental models. The bovine, young human, and elderly human failure loads were 799 +/- 261 N, 655 +/- 186 N, and 382 +/- 118 N, respectively, and the failure modes were 75%, 69%, and 30% tissue failures, respectively. The similarities between the bovine and young human models in failure loads and failure modes indicate that bovine models are appropriate for ACL reconstruction fixation studies. The statistically significant differences between the young human and elderly human models in failure loads and failure modes indicate that elderly human cadavers are not an appropriate model for ACL reconstruction fixation studies. The differences in failure modes are consistent with previous studies using elderly human cadavers in which the predominant failure mode was bone block pullout. The tissue failures observed in the bovine and young human models contradict previous studies suggesting fixation strength is the weakest link in bone-patellar tendon-bone ACL reconstruction. Results of linear regression modeling showed statistically significant correlations between insertion torque and failure load (R2 = 0.44, P < 0.0001) and interference (defined as the screw outer thread diameter minus the tunnel-bone block gap) and insertion torque (R2 = 0.18, P = 0.003) when data from all models was combined. Results for the bovine model multiple regression showed a statistically significant regression of insertion torque (linear) and interference (quadritic) versus failure load (R2 = 0.56, P = 0.02). Regression slopes for screw diameter (P = 0.52) and gap size (P = 1.00) were not statistically significant. These results indicate that insertion torque and interference are independent predictors of failure load and should be included in future interference screw studies in addition to bone block dimensions, tunnel size, gap size, and screw diameter. Clinicians may consider using insertion torque and interference as indicators of postoperative graft fixation regarding rehabilitation decisions.

Adult↗
PubMed1995

Altered Hox expression and segmental identity in Mll-mutant mice.

The mixed-lineage leukaemia gene (MLL/HRX/ALL-1) is disrupted by chromosomal translocation in human acute leukaemias that often display mixed lymphoid-myeloid phenotypes and present in infancy. MLL possesses a highly conserved SET domain also found in Drosophila trithorax (trx) and Polycomb group (Pc-G) genes, which are known to regulate homeotic genes (HOM-C) in a positive or negative fashion, respectively. Mll was targeted in mice by homologous recombination in embryonic stem (ES) cells to assess its role in pattern development. Mll heterozygous (+/-) mice had retarded growth, displayed haematopoietic abnormalities, and demonstrated bidirectional homeotic transformations of the axial skeleton as well as sternal malformations. Mll deficiency (-/-) was embryonic lethal. Anterior boundaries of Hoxa-7 and Hoxc-9 expression were shifted posteriorly in Mll +/- embryos, but their expression was abolished in Mll -/- embryos. Thus Mll is required for proper segment identity in mammals, displays haplo-insufficiency, and positively regulates Hox gene expression.

Animals↗
PubMed1995

Bax-deficient mice with lymphoid hyperplasia and male germ cell death.

BAX, a heterodimeric partner of BCL2, counters BCL2 and promotes apoptosis in gain-of-function experiments. A Bax knockout mouse was generated that proved viable but displayed lineage-specific aberrations in cell death. Thymocytes and B cells in this mouse displayed hyperplasia, and Bax-deficient ovaries contained unusual atretic follicles with excess granulosa cells. In contrast, Bax-deficient males were infertile as a result of disordered seminiferous tubules with an accumulation of atypical premeiotic germ cells, but no mature haploid sperm. Multinucleated giant cells and dysplastic cells accompanied massive cell death. Thus, the loss of Bax results in hyperplasia or hypoplasia, depending on the cellular context.

Animals↗
PubMed1995

Relationship of DNA topoisomerase II alpha and beta expression to cytotoxicity of antineoplastic agents in human acute lymphoblastic leukemia cell lines.

The levels of expression of topoisomerase II alpha and topoisomerase II beta were investigated in six established cell lines of human childhood acute lymphoblastic leukemia (ALL) as a function of doubling time, cell cycle distribution, and of sensitivity to the antineoplastic agents Adriamycin and etoposide. The slowest growing cell line, ALL-G, was most sensitive to both drugs, whereas the fastest growing cell line, ALL-C, was 15.3- and 6.4-fold more resistant than ALL-G to Adriamycin and etoposide, respectively. Furthermore, ALL-W, the second most rapidly dividing cell line, was most resistant to both Adriamycin (22.8-fold) and etoposide (14.1-fold). Expression of topoisomerase II alpha varied inversely with doubling time, whereas no correlation was found between topoisomerase II beta levels and doubling time. Expression of topoisomerase II beta varied inversely with that of topoisomerase II alpha. The level of topoisomerase II alpha correlated directly with the percentage of cells in S and G2-M phases, whereas topoisomerase II beta expression varied directly with the number of cells in G1. An inverse correlation was found between the level of expression of topoisomerase II beta and resistance to Adriamycin, whereas a direct correlation was observed between the level of expression of topoisomerase II alpha and resistance to Adriamycin. Studies with etoposide, although not statistically significant, were consistent with the pattern observed with Adriamycin. These findings suggest that in ALL cells, cytocidal activity of Adriamycin and etoposide may be mediated, at least in part, by topoisomerase II beta.

Antineoplastic Agents↗
PubMed1995

Remission following an elemental diet or prednisolone in Crohn's disease.

The short- and long-term effects of an elemental diet in children with acute Crohn's disease were compared with those of prednisolone in historical controls. Clinical remission was induced in 25 of 30 and in 18 of 28 episodes treated for six weeks with an elemental diet and prednisolone. Patients with proximal disease had longer remission after treatment with an elemental diet (p < 0.05) than did patients with colonic disease after treatment with prednisolone (p < 0.01). Disease activity index score improved in both groups compared with the pretreatment scores (p < 0.05). However, the improvement in the elemental diet group was significantly better than in the prednisolone group (p < 0.001). Changes in linear growth were better after treatment with an elemental diet compared with steroids (p < 0.001). Serum albumin and haematocrit concentrations all improved significantly in the children treated with an elemental diet (p < 0.001) but not in those treated with steroids. Thus an elemental diet was better than prednisolone in proximal disease and confirmed improved growth and nutritional status.

Adolescent↗
PubMed1994

Chondroid chordoma--a variant of chordoma. A morphologic and immunohistochemical study.

In 1973, Heffelfinger and coworkers described a variant of chordoma that contained cartilaginous areas indistinguishable from hyaline type chondrosarcoma. They designated these tumors chondroid chordomas and found that they had a better prognosis than classic (nonchondroid) chordomas. Since that time, there has been an ongoing debate over whether chondroid chordoma is best considered a distinct clinicopathologic entity separable from chondrosarcoma or a misdiagnosed chondrosarcoma whose concept developed from the erroneous interpretation of morphology. In an attempt to clarify the issue, the authors used light microscopy and immunohistochemistry to study 12 chondroid chordomas, 38 classic chordomas, and 28 chondrosarcomas that arose in the base of the skull or spine. As a reference, they also analyzed the immunohistochemical profile of fetal notochord, ecchordosis physaliphora, and fetal hyaline cartilage. They found that all chondroid and nonchondroid chordomas were positive for cytokeratin, and the majority were also positive for epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA). In contrast, none of the chondrosarcomas stained for cytokeratin, EMA or CEA. Vimentin and S-100 were positive in more than 95% of both classic and chondroid chordomas and chondrosarcomas. The immunohistochemical profile of these tumors was similar to the pattern of immunoreactivity of their nonneoplastic counterparts. The authors conclude that chondroid chordomas is a variant of chordoma and should not be confused with chondrosarcoma. Because chondroid chordomas have been reported to have a better prognosis, they felt that this nosologic term should be preserved and that chondroid chordoma should continue to be a focus of clinical and pathologic study.

Adolescent↗
PubMed1993

Pancreatic exocrine function and necrotising enterocolitis.

Pancreatic protease deficiency may be an aetiological factor in enteritis necroticans, a disease sharing some features of necrotising enterocolitis (NEC). Using faecal chymotrypsin measurement we have prospectively studied pancreatic exocrine function in infants at risk of NEC. No significant difference was found comparing those infants who subsequently developed NEC and those who did not.

Chymotrypsin↗
PubMed1993

Characterization of a DNA topoisomerase IIalpha gene rearrangement in adriamycin-resistant P388 leukemia: expression of a fusion messenger RNA transcript encoding topoisomerase IIalpha and the retinoic acid receptor alpha locus.

Previous studies using cloned lines of Adriamycin-sensitive and -resistant P388 murine leukemia cells have suggested that a reduction in DNA topoisomerase II alpha (topo II alpha) enzyme activity and protein levels in drug-resistant cell lines (A. M. Deffie, J. K. Batra, and G. J. Goldenberg, Cancer Res., 49: 58-62, 1989) may be due to an allelic mutation in the topo II alpha gene (A. M. Deffie, D. J. Bosman, and G. J. Goldenberg, Cancer Res., 49: 6879-6882, 1989). The drug-resistant cell lines P388/ADR/3 and P388/ADR/7 express a shortened topo II alpha mRNA transcript in addition to the native transcript present in the drug-sensitive P388/4 cell line. Using complementary DNA probes derived from the coding sequence and 3' untranslated region of the native mouse topo II alpha transcript, we have determined that the shorter 4.5-kilobase topo II alpha transcript expressed in the drug-resistant cell lines contains only 3.5-kilobases of topo II sequence from the 5'-terminus onwards. Using a 3'-rapid amplification of cDNA ends strategy, we have cloned cDNAs representing the 3'-termini of both the native and mutant transcripts from both P388/ADR/3 and P388/ADR/7 cells. DNA sequence analysis revealed that the shorter 4.5-kilobase transcript: (a) encodes topoisomerase II alpha until nucleotide position 3494, at which point the sequence diverges for the remaining 956 bases; (b) contains a polyadenylation signal distinct from the native transcript; and (c) contains an open reading frame predicting a truncated topo II alpha fusion protein. Of great interest was the finding that the non-topo II alpha 956-base sequence in the shorter transcript encodes the promoter, exon I, and part of the first intron of the murine retinoic acid receptor alpha gene locus in the antisense orientation, suggesting that a rearrangement on chromosome 11 in the drug-resistant cells led to a gene fusion event between the loci encoding topo II alpha and retinoic acid receptor alpha.

Amino Acid Sequence↗
PubMed1993

The pathogenesis of wild type and drug resistant mutant strains of bovine herpesvirus-1 (BHV-1) in the natural host.

An experimental infection with bovine herpesvirus-1 was established in calves by means of intranasal inoculation. Three calves were infected with the parental strain BHV-1 w/t, three with the TK-defective strain, B 1 and four with the HPMPA-resistant strain, 3 A. Inoculation with w/t virus resulted in a reproducible clinical disease characterised by respiratory distress, fever and the presence of virus in nasal mucus. Following the acute infection, w/t-inoculated animals became seropositive for BHV-1 specific antibody. The TK-defective mutant (BHV-1 B 1) produced an acute infection similar to the parental virus in all three calves inoculated. The HPMPA-resistant mutant (BHV-1 3 A), however, showed a reduced pattern of infection and virus of lower titre was isolated from three of four calves; the antibody responses were generally lower, and one calf remained seronegative until reactivation. Following stimulation with dexamethasone 72 days after the primary inoculation, virus was re-isolated from all wild type-inoculated calves. In contrast, no evidence of reactivation was obtained from the three B 1-inoculated animals. However, all four animals inoculated with the mutant 3 A showed virus reactivation including the calf which had remained seronegative following primary virus inoculation. Previous studies have suggested that drug-resistance mutations in herpesviruses frequently are associated with reduced pathogenicity on the basis of experiments in laboratory models. The importance of the present study is the demonstration that two different drug-resistant variants of an alpha herpesvirus both have altered pathogenicity in the natural host for that infection. These results also have implications for the design and use of attenuated vaccine strains.

Adenine↗
PubMed1993

New method for determining faecal fat excretion in infancy.

Collecting complete, timed stool samples for the estimation of faecal fat from infants wearing nappies is difficult. A gravimetric method has been adapted by applying a chloroform/methanol homophasic solvent system to extract lipids from whole soiled nappies. In a study of 22 collections in six infants, no stools were lost and the recovery of lipids was 96%, with results similar to a reference titrimetric method. In addition to total fat, individual lipids were measured using gas-liquid chromatography. The method simplifies stool collection and analysis, is aesthetically more acceptable, and leads to reduced microbial hazards. It also allows the detailed study of excreted lipid species enabling the coefficient of absorption of dietary lipids of various chain lengths to be determined individually.

Chemistry, Clinical↗
PubMed1992

Elevated short chain fatty acid concentrations in anaerobic small bowel contamination.

Viable bacteria were identified and counted, and short chain fatty acid concentrations measured in small intestinal fluid from 74 fasting children. In nine children with anaerobic small bowel contamination, individual and total short chain fatty acid concentrations were significantly higher than the remainder of the group (p less than 0.01). Using 100 mumol/l as the upper reference limit for total short chain fatty acid concentration, the sensitivity and specificity as a test for anaerobic small bowel contamination was 89% and 98%, respectively. Measuring luminal short chain fatty acid concentrations in proximal small intestinal fluid is an accurate method for detecting anaerobic small bowel contamination in children.

Adolescent↗
PubMed1992

Using the steatocrit to determine optimal fat content in modular feeds.

The steatocrit was measured in infants with protracted diarrhoea who were receiving intragastric modular feeds. Measurements were made when fat intake was constant to determine steatocrit variability and during increases in fat intake to determine fat tolerance limits. Steatocrit variability was expressed as the range between a subject's lowest and highest steatocrit value. The median between-stool and between-day variabilities were 2% and 11% respectively. Variability was also measured in seven healthy breast fed infants. In the five still displaying appreciable physiological steatorrhoea, the between-day variability (median 8%) and between-stool variability (median 9%) were not significantly different from the protracted diarrhoea group. In the fat tolerance investigations in the protracted diarrhoea group, the steatocrit increased with increases in the module fat content. Fat intake and steatocrit were significantly positively related. A significant negative correlation was seen between steatocrit and weight gain, the latter becoming negligible at steatocrit values around 30%.

Breast Feeding↗
PubMed1992

The steatocrit: an improved procedure.

The steatocrit is a simple and easily repeated assay for measuring the fat content of infants' stools. However, we and others have experienced technical difficulties in its use. Three modifications were therefore made to the original procedure: incorporation of a lipid-soluble dye, improved homogenization and a heating step. The modified method was used to measure the stool fat content of young children with and without clinical steatorrhoea. Validation of the modified steatocrit is presented, together with examples of its application to both clinical research and clinical practice.

Celiac Disease↗