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Biomedical subjects

C Barlow

Publications and source records attributed to C Barlow.

At least 19 recordsLinked to original sources
PubMed2005

Chlorambucil and lomustine (CL56) in absolute hormone refractory prostate cancer: re-induction of endocrine sensitivity an unexpected finding.

The management of androgen independent prostate cancer is increasingly disputed. Diethylstilbestrol and steroids have useful second-line activity in its management. The value of chemotherapy still remains contentious. This paper reports a phase 2 study of two orally active chemotherapy drugs in patients who are absolutely hormone refractory having failed primary androgen blockade and combined oestrogens and corticosteroids. In total, 37 patients who were biochemically castrate with absolute hormone refractory prostate cancer and performance status of 0-3 were enrolled. Therapy consisted of chlorambucil 1 mg kg(-1) given as 6 mg a day until the total dose was reached and lomustine 2 mg kg(-1) given every 56 days (CL56). During this time all hormone therapy was stopped. One patient normalised his PSA with a further two having a greater than 50% decline leading to an objective response rate of 10%. The median time to progression was 3.6 months with an overall survival of 7.1 months. The median survival of this group of patients from first becoming androgen independent was 23.5 months. Eight of 17 (47%) patients who were subsequently re-challenged with hormonal therapy following failure of chemotherapy had a further PSA reduction, three (17%) of which were >50%. The median progression-free interval for the eight patients was 4 months. In conclusion, CL56 has a low objective response rate in the management of absolute hormone refractory prostate cancer. Toxicity was mild. Re-induction of hormone sensitivity following failure of chemotherapy was an unexpected finding that requires further study.

Aged↗
PubMed2004

Dose intense triplet chemotherapy with gemcitabine, carboplatin, paclitaxel with peripheral blood progenitor cell support for six cycles in advanced epithelial ovarian cancer.

The interval required for haematological reconstitution following myelosuppressive chemotherapy can be reduced by the infusion of autologous peripheral blood progenitor cells (PBPCs). When carboplatin (C) and paclitaxel (P) are followed by granulocyte colony-stimulating factor (GCSF), multiple courses can be given at 10-day intervals with the autologous PBPCs from a unit of whole blood with each cycle. We extended this approach and defined the dose-limiting toxicity and maximum-tolerated dose for the addition of gemcitabine (G) to CP for patients (pts) with EOC in a phase I-II study of increasing doses of G (0, 800, 1000 and 1250 mg x m(-2)) over four cohorts with C at area under curve (AUC) 6, plus P at 175 mg x m(-2) 3 h(-1) every 10 days for six cycles. Granulocyte colony-stimulating factor 5 microg x kg(-1) day(-1) was given s.c. days 1-10 and 450 ml whole blood was venesected before each treatment, stored untreated at 4 degrees C and reinfused 24 h later. In all, 17 patients with EOC either bulky stage IV or recurrent after treatment-free interval >12 months were treated over 30 months. Of the 17 patients, 13 completed six cycles (one patient stopped early with PD, three with toxicity), interdose interval 9-28 (median 10) days. Delays occurred in four patients due to infection or malaise, and there were no dose reductions. Haematological toxicity was not considered to be dose limiting. Febrile neutropenia was uncommon (2 patients), but grade III/IV thrombocytopenia was seen across all cohorts. Treatment was not delayed for thrombocytopenia and no bleeding complications occurred. Grade III transaminitis was seen in all patients in cohort 4 and grade IV toxicity, considered to be dose limiting, occurred in one. Responses were observed at all dose levels with six CR, seven PR, three SD and one PD. Dose intense GCP was deliverable over six cycles with manageable haematological toxicity, but with dose-limiting hepatic toxicity in cohort 4. The MTD was gemcitabine 1000 mg x m(-2), carboplatin AUC 6, paclitaxel 175 mg x m(-2) given every 10 days for six cycles.

Adolescent↗
PubMed2004

From disease genes to cellular pathways: a progress report.

Mutations in a large number of retinal and retinal pigment epithelium (RPE) expressed genes can lead to the degeneration of photoreceptors and consequently the loss of vision. The genetic and phenotypic heterogeneity of retinal dystrophies poses a complex problem with respect to rational development of therapeutic strategies. Delineation of physiological functions of disease genes and identification of pathways that lead to disease pathogenesis represent essential goals towards developing a systematic and global approach to gene-based treatments. We are interested in identifying cellular pathways that are involved in photoreceptor differentiation, function and degeneration. We are, therefore, generating comprehensive gene expression profiles of retina and RPE of humans and mice using both cDNA- and oligonucleotide-based (Affymetrix) microarrays. Because of the under-representation of retinal/RPE genes in the public databases, we have constructed several unamplified cDNA libraries and produced almost twenty thousand expressed sequence tags (ESTs) that are being printed onto glass slides ('I-Gene' microarrays). In this presentation, we will report the microarray analysis of the rodless (and cone-enhanced) retina from the Nrl-knockout mouse as a paradigm to initiate the identification of cellular pathways involved in photoreceptor differentiation and function.

DNA-Binding Proteins↗
PubMed2003

Histologic characteristics of laparoscopic saline-enhanced electrosurgery of liver and splenic injuries.

BACKGROUND: Hemostasis is crucial during laparoscopic surgery. Unlike conventional electrosurgery, saline-enhanced electrosurgery (SEE) improves the electrode-to-tissue interface. This study investigated SEE as a means of achieving hemostasis in liver and splenic injuries and assessed the associated histologic changes. METHODS: Nine anesthetized pigs underwent laparoscopic liver tip and splenic wedge amputations. Injuries were treated with SEE (25-35 and 35-45 W, respectively). Animals were sacrificed postprocedure and at 1 and 4 weeks. Depth of necrosis was analyzed using a mixed model analysis of variance. RESULTS: Liver mean depth of necrosis was 5.3 mm (acute), 6.0 mm (1 week), and 5.3 mm (4 weeks) ( p = not significant). Splenic mean depth of necrosis was 7.0 mm (acute), 7.0 mm (1 week), and 2.7 mm (4 weeks). ( p < 0.01) Acute injuries demonstrated thermal coagulation necrosis that healed with well-defined bands of collagen at 1 and 4 weeks. CONCLUSIONS: SEE provides effective hemostasis and results in an acceptable depth of necrosis with satisfactory wound healing in a porcine model of solid organ injury.

Animals↗
PubMed2001

A targeted dominant negative mutation of the thyroid hormone alpha 1 receptor causes increased mortality, infertility, and dwarfism in mice.

Mutations in the thyroid hormone receptor beta (TRbeta) gene result in resistance to thyroid hormone. However, it is unknown whether mutations in the TRalpha gene could lead to a similar disease. To address this question, we prepared mutant mice by targeting mutant thyroid hormone receptor kindred PV (PV) mutation to the TRalpha gene locus by means of homologous recombination (TRalpha1PV mice). The PV mutation was derived from a patient with severe resistance to thyroid hormone that has a frameshift of the C-terminal 14 aa of TRbeta1. We knocked in the same PV mutation to the corresponding TRalpha gene locus to compare the phenotypes of TRalpha1(PV/+) mice with those of TRbeta(PV/+) mice. TRalpha1(PV/+) mice were viable, indicating that the mutation of the TRalpha gene is not embryonic lethal. In drastic contrast to the TRbeta(PV/+) mice, which do not exhibit a growth abnormality, TRalpha1(PV/+) mice were dwarfs. These dwarfs exhibited increased mortality and reduced fertility. In contrast to TRbeta(PV/+) mice, which have a hyperactive thyroid, TRalpha1(PV/+) mice exhibited mild thyroid failure. The in vivo pattern of abnormal regulation of T3 target genes in TRalpha1(PV/+) mice was unique from those of TRbeta(PV/+) mice. The distinct phenotypes exhibited by TRalpha1(PV/+) and TRbeta(PV/+) mice indicate that the in vivo functions of TR mutants are isoform-dependent. The TRalpha1(PV/+) mice may be used as a tool to uncover human diseases associated with mutations in the TRalpha gene and, furthermore, to understand the molecular mechanisms by which TR isoforms exert their biological activities.

Animals↗
PubMed2001

Localization of atherosclerosis susceptibility loci to chromosomes 4 and 6 using the Ldlr knockout mouse model.

Atherosclerosis is a complex disease resulting from the interaction of multiple genes. We have used the Ldlr knockout mouse model in an interspecific genetic cross to map atherosclerosis susceptibility loci. A total of 174 (MOLF/Ei x B6.129S7-Ldlr(tm1Her)) x C57BL/6J-Ldlr(tm1Her) backcross mice, homozygous for the Ldlr null allele, were fed a Western-type diet for 3 months and then killed for quantification of aortic lesions. A genome scan was carried out by using DNA pools and microsatellite markers spaced at approximately 18-centimorgan intervals. Quantitative trait locus analysis of individual backcross mice confirmed linkages to chromosomes 4 (Athsq1, logarithm of odds = 6.2) and 6 (Athsq2, logarithm of odds = 6.7). Athsq1 affected lesions in females only whereas Athsq2 affected both sexes. Among females, the loci accounted for approximately 50% of the total variance of lesion area. The susceptible allele at Athsq1 was derived from the MOLF/Ei genome whereas the susceptible allele at Athsq2 was derived from C57BL/6J. Inheritance of susceptible alleles at both loci conferred a 2-fold difference in lesion area, suggesting an additive effect of Athsq1 and Athsq2. No associations were observed between the quantitative trait loci and levels of plasma total cholesterol, high density lipoprotein cholesterol, non-high density lipoprotein cholesterol, insulin, or body weight. We provide strong evidence for complex inheritance of atherosclerosis in mice with elevated plasma low density lipoprotein cholesterol and show a major influence of nonlipoprotein-related factors on disease susceptibility. Athsq1 and Athsq2 represent candidate susceptibility loci for human atherosclerosis, most likely residing on chromosomes 1p36--32 and 12p13--12, respectively.

Animals↗
PubMed2001

Ataxia telangiectasia mutated is essential during adult neurogenesis.

Ataxia telangiectasia (A-T) is an autosomal recessive disease characterized by normal brain development followed by progressive neurodegeneration. The gene mutated in A-T (ATM) is a serine protein kinase implicated in cell cycle regulation and DNA repair. The role of ATM in the brain and the consequences of its loss on neuronal survival remain unclear. We studied the role of ATM in adult neural progenitor cells in vivo and in vitro to define the role of ATM in dividing and postmitotic neural cells from Atm-deficient (Atm(-/-)) mice in a physiologic context. We demonstrate that ATM is an abundant protein in dividing neural progenitor cells but is markedly down-regulated as cells differentiate. In the absence of ATM, neural progenitor cells of the dentate gyrus show abnormally high rates of proliferation and genomic instability. Atm(-/-) cells in vivo, and in cell culture, show a blunted response to environmental stimuli that promote neural progenitor cell proliferation, survival, and differentiation along a neuronal lineage. This study defines a role for ATM during the process of neurogenesis, demonstrates that ATM is required for normal cell fate determination and neuronal survival both in vitro and in vivo, and points to a mechanism for neuronal cell loss in progressive neurodegenerative diseases.

Animals↗
PubMed2001

Chipping away at complex behavior: transcriptome/phenotype correlations in the mouse brain.

Highly parallel gene expression profiling has the potential to provide new insight into the molecular mechanisms of complex brain diseases and behavioral traits. We review how gene expression profiling in various brain regions of inbred mouse strains has been used to identify genes that may contribute to strain-specific phenotypes. New data, which demonstrate the use of gene expression profiling in combination with behavioral testing to identify candidate genes involved in mediating variation in running wheel activity, are also presented. These and other studies suggest that a combination of gene expression profiling and more traditional genetic approaches, such as quantitative trait locus analysis, can be used to identify genes responsible for specific neurobehavioral phenotypes.

Animals↗
PubMed2001

Reversible posterior leukoencephalopathy syndrome following CHOP chemotherapy for diffuse large B-cell lymphoma.

A 63-year-old female with stage IE diffuse large B-cell lymphoma developed reversible posterior leukoencephalopathy syndrome (RPLS) following CHOP chemotherapy, with typical clinical and radiological findings. RPLS is a rare neurological syndrome characterised by visual disturbances, seizures, headaches and altered conscious level which has been associated with malignant hypertension, pre-eclampsia and some drugs, including ciclosporin. It has not been previously reported following CHOP chemotherapy. Alternative treatment should be considered for patients who develop this rare complication.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2001

Expressing what's on your mind: DNA arrays and the brain.

Questions about brain function and disease are being addressed with parallel genomic approaches. High-density DNA arrays make it possible to monitor the expression levels of thousands of genes at a time, and are being used to address old questions in new ways and to generate new hypotheses about the workings of the brain.

Animals↗
PubMed2001

Heterozygosity for a mutation in Brca1 or Atm does not increase susceptibility to ENU-induced mammary tumors in Apc(Min)/+ mice.

The proteins encoded by BRCA1 and ATM may be important in DNA repair and maintenance of genomic integrity. Women heterozygous for a mutation in BRCA1 have an increased incidence of breast cancer. Some evidence also suggests that female carriers of ATM mutations may be susceptible to breast cancer. However, mice carrying one mutant allele of Brca1 or ATM are not highly susceptible to breast cancer. We proposed that heterozygosity for a mutant allele of Brca1 or ATM may confer a decreased ability to repair DNA damage. Such a defect might lead to a heightened sensitivity to tumor development in susceptible animal models. Therefore, mice predispose to mammary tumor development might show an increased susceptibility if they also carry an ATM or Brca1 mutation. C57BL/6J (B6) MIN/+ mice are predisposed to mammary and intestinal tumors and exposure to the point mutagen ethylnitrosourea (ENU) markedly increases mammary tumor multiplicity and incidence. To test our hypothesis, B6.MIN/+ male mice were crossed with 129S6/SvEvTac females heterozygous for a mutant allele of either Brca1 or ATM. Female progeny from each cross were treated with ENU and followed for tumor development. Only MIN/+ F1 females developed mammary tumors and heterozygosity for a mutant Brca1 or ATM allele had no effect on mammary or intestinal tumor incidence and multiplicity. These results suggest that heterozygosity for a mutation in Brca1 or ATM: does not affect MIN-induced tumorigenesis in mice under these conditions. Additionally, exposure to a somatic point mutagen does not increase tumor development in mice carrying Brca1 or ATM mutations.

Animals↗
PubMed2001

Skeletal muscle acidosis correlates with the severity of blood volume loss during shock and resuscitation.

BACKGROUND: Continuous assessment of tissue perfusion and oxygen utilization may allow for early recognition and correction of hemorrhagic shock. We hypothesized that continuously monitoring skeletal muscle (SM) PO2, PCO2, and pH during shock would provide an easily accessible method for assessing the severity of blood loss and the efficacy of resuscitation. METHODS: Thirteen anesthetized pigs (25-35 kg) underwent laparotomy and femoral vessel cannulation. Multiparameter fiberoptic sensors were placed in the deltoid (SM) and femoral artery. Ventilation was maintained at a PaCO2 of 40-45 mm Hg. Total blood volume (TBV) was measured using an Evans blue dye technique. Animals were bled for 15 minutes, maintained at a mean arterial pressure (MAP) of 40 mm Hg for 1 hour, resuscitated (shed blood + 2 times shed volume in normal saline) and observed for 1 hour. Four animals served as controls (sham hemorrhage). Blood and tissue samples were taken at each time point. RESULTS: Blood loss ranged from 28.5-56% of TBV. SM pH and SM PO2 levels fell rapidly with shock. SM PO2 returned to normal with resuscitation; however, SM pH did not return to baseline. SM PCO2 significantly rose with shock, but returned to baseline promptly with resuscitation. There was a significant correlation between SM pH and blood volume loss at end shock (r2 = 0.73, p < 0.001) and recovery (r2 = 0.84, p < 0.001). Animals (n = 2) whose SM pH did not recover to 7.2 were found to have ongoing blood loss from biopsy sites and persistent tissue hypercarbia despite normal MAP. CONCLUSION: Continuous multiparameter monitoring of SM provides a minimally invasive method for assessing severity of shock and efficacy of resuscitation. Both PCO2 and PO2 levels change rapidly with shock and resuscitation. SM pH is directly proportional to lost blood volume. Persistent SM acidosis (pH < 7.2) and elevated PCO2 levels suggest incomplete resuscitation despite normalized hemodynamics.

Acidosis, Lactic↗
PubMed2000

Mice with a targeted mutation in the thyroid hormone beta receptor gene exhibit impaired growth and resistance to thyroid hormone.

Patients with mutations in the thyroid hormone receptor beta (TRbeta) gene manifest resistance to thyroid hormone (RTH), resulting in a constellation of variable phenotypic abnormalities. To understand the molecular basis underlying the action of mutant TRbeta in vivo, we generated mice with a targeted mutation in the TRbeta gene (TRbetaPV; PV, mutant thyroid hormone receptor kindred PV) by using homologous recombination and the Cre/loxP system. Mice expressing a single PV allele showed the typical abnormalities of thyroid function found in heterozygous humans with RTH. Homozygous PV mice exhibit severe dysfunction of the pituitary-thyroid axis, impaired weight gains, and abnormal bone development. This phenotype is distinct from that seen in mice with a null mutation in the TRbeta gene. Importantly, we identified abnormal expression patterns of several genes in tissues of TRbetaPV mice, demonstrating the interference of the mutant TR with the gene regulatory functions of the wild-type TR in vivo. These results show that the actions of mutant and wild-type TRbeta in vivo are distinct. This model allows further study of the molecular action of mutant TR in vivo, which could lead to better treatment for RTH patients.

Alleles↗
PubMed2000

Regional and strain-specific gene expression mapping in the adult mouse brain.

To determine the genetic causes and molecular mechanisms responsible for neurobehavioral differences in mice, we used highly parallel gene expression profiling to detect genes that are differentially expressed between the 129SvEv and C57BL/6 mouse strains at baseline and in response to seizure. In addition, we identified genes that are differentially expressed in specific brain regions. We found that approximately 1% of expressed genes are differentially expressed between strains in at least one region of the brain and that the gene expression response to seizure is significantly different between the two inbred strains. The results lead to the identification of differences in gene expression that may account for distinct phenotypes in inbred strains and the unique functions of specific brain regions.

Animals↗
PubMed2000

Abnormal rearrangement within the alpha/delta T-cell receptor locus in lymphomas from Atm-deficient mice.

Atm-deficient mice (Atm(-/-)) recapitulate many aspects of the ataxia telangiectasia (AT) syndrome, including the susceptibility to tumors of lymphoid origin. To investigate the mechanism of tumorigenesis, we have examined a panel of 8 thymic lymphomas from Atm(-/-) mice. All Atm(-/-) tumors are of thymic lymphoblastoid origin, display an immature CD3(-) and CD4(+)/CD8(+) phenotype, and arise coincident with V(D)J recombination. Cytogenetically, all tumors are diploid or near diploid but exhibit multiple chromosome aberrations with an average of 4 abnormal chromosomes per tumor. All the tumors revealed chromosome 14 rearrangements precisely at the T-cell receptoralpha/delta (Tcralpha/delta) locus, suggesting the involvement of V(D)J recombination in these translocations. In addition, 11.5% of Atm(-/-) peripheral T cells showed chromosome 14 translocations, suggesting that rearrangements at the Tcralpha/delta locus occur early during tumor development in the absence of ATM. However, additional genetic aberrations are required for tumorigenesis. For example, translocations involving chromosome 12, often with chromosome 14 (more than 60%), and partial or complete trisomy of chromosome 15, with copy number increases of the c-myc oncogene were frequently observed. These observations suggest that ATM is required for normal rearrangement of the Tcralpha/delta locus but not for V(D)J recombination at other loci. The mechanisms that lead to tumorigenesis may be due to the involvement of ATM in monitoring double-stranded DNA breaks. (Blood. 2000;96:1940-1946)

Animals↗
PubMed2000

Recombinase-activating gene (RAG) 2-mediated V(D)J recombination is not essential for tumorigenesis in Atm-deficient mice.

The majority of Atm-deficient mice die of malignant thymic lymphoma by 4-5 mo of age. Cytogenetic abnormalities in these tumors are consistently identified within the Tcr alpha/delta locus, suggesting that tumorigenesis is secondary to aberrant responses to double-stranded DNA breaks that occur during V(D)J recombination. Since V(D)J recombination is a recombinase-activating gene (RAG)-dependent process, we generated Rag2(-/-)Atm(-/-) mice to assess the requirement for RAG-dependent recombination in thymic lymphomagenesis. In contrast to expectation, the data presented here indicate that development of malignant thymic lymphoma in Atm(-/-) mice is not prevented by loss of RAG-2 and thus is not dependent on V(D)J recombination. Malignant thymic lymphomas in Rag2(-/-)Atm(-/-) mice occurred at a lower frequency and with a longer latency as compared with Atm(-/-) mice. Importantly, cytogenetic analysis of these tumors indicated that multiple chromosomal abnormalities occurred in each tumor, but that none of these involved the Tcr alpha/delta locus. Nonmalignant peripheral T cells from TCR-transgenic Rag2(-/-)Atm(-/-) mice also revealed a substantial increase in translocation frequency, suggesting that these translocations are early events in the process of tumorigenesis. These data are consistent with the hypothesis that the major mechanism of tumorigenesis in Atm(-/-) mice is via chromosomal translocations and other abnormalities that are secondary to aberrant responses to double-stranded DNA breaks. Furthermore, these data suggest that V(D)J recombination is a critical, but not essential, event during which Atm-deficient thymocytes are susceptible to developing chromosome aberrations that predispose to malignant transformation.

Animals↗
PubMed2000

ATM is a cytoplasmic protein in mouse brain required to prevent lysosomal accumulation.

We previously generated a mouse model with a mutation in the murine Atm gene that recapitulates many aspects of the childhood neurodegenerative disease ataxia-telangiectasia. Atm-deficient (Atm-/-) mice show neurological defects detected by motor function tests including the rota-rod, open-field tests and hind-paw footprint analysis. However, no gross histological abnormalities have been observed consistently in the cerebellum of any line of Atm-/- mice analyzed in most laboratories. Therefore, it may be that the neurologic dysfunction found in these animals is associated with predegenerative lesions. We performed a detailed analysis of the cerebellar morphology in two independently generated lines of Atm-/- mice to determine whether there was evidence of neuronal abnormality. We found a significant increase in the number of lysosomes in Atm-/- mice in the absence of any detectable signs of neuronal degeneration or other ultrastructural anomalies. In addition, we found that the ATM protein is predominantly cytoplasmic in Purkinje cells and other neurons, in contrast to the nuclear localization of ATM protein observed in cultured cells. The cytoplasmic localization of ATM in Purkinje cells is similar to that found in human cerebellum. These findings suggest that ATM may be important as a cytoplasmic protein in neurons and that its absence leads to abnormalities of cytoplasmic organelles reflected as an increase in lysosomal numbers.

Animals↗