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Biomedical subjects

J R Gilbert

Publications and source records attributed to J R Gilbert.

At least 55 records · Page 3Linked to original sources
PubMed1999

Evolving trends in liver transplantation: an outcome and charge analysis.

BACKGROUND: Due to the limited supply and increased demand for donor livers, waiting times are progressively lengthening, which may lead to transplantation at more advanced and less cost-effective stages of disease. The purpose of this study was to evaluate the outcomes and hospital charges of liver transplantation during two recent eras to identify areas for providing more cost-effective care. METHODS: A total of 144 primary liver allografts were performed from 1991 to 1996. Patient characteristics, outcome measures, and hospital charges were compared for patients receiving allografts between 1991 and 1993 (group A) versus those receiving grafts between 1994 and 1996 (group B) using unpaired Student t tests for continuous data and chi-squared tests for categorical data. RESULTS: In comparing groups A and B, no significant differences in patient demographics, relative contraindications, or indication for transplantation existed; median waiting time from date of listing until transplant increased from 88 days to 159 days; and a shift in UNOS priority status at time of transplantation occurred, as the percentage of patients requiring inpatient care increased from 58% to 75% (P=0.034). Despite this, patient hospital and 1-year survival significantly improved from 75.0% to 90.3% (P=0.016), and from 68.1% to 88.9% (P=0.002), respectively. Total hospital charges, without correction for inflation, were $174,908+/-16,388 in A and $193,525+/-14,444 in B (P=0.288). The increased charges were associated with longer inpatient length of stay (LOS) before transplant, resulting in increased pretransplant charges from $24,088+/-4134 (A) to $39,490+/-6,196 (B) (P=0.011). Room and service (54%) was the largest pretransplant contributor to charges, while blood products (23%), room and service (21%), organ acquisition (13%), and operating room charges (11%) contributed the most after transplant. CONCLUSIONS: Longer waiting times resulting in transplantation at later stages of disease have occurred, leading to longer pretransplant LOS and its associated charges. Despite more advanced disease, patient survival rates have significantly improved with fewer infection-related deaths. LOS pretransplant, blood products, and operating room services represent potential areas for providing more cost-effective care.

Adolescent↗
PubMed1999

Sialylated human apolipoprotein E (apoEs) is preferentially associated with neuron-enriched cultures from APOE transgenic mice.

Mice transgenic for human APOE2, E3, and E4 alleles express native 34-kDa human apoE and two sialylated apoE isoproteins with approximate molecular weights of 37 kDa (apoEs) and 39 kDa (apoEs2) in brain. These multiple apoE/apoEs/apoEs2 band patterns on Western blot are also observed in human brain, but are not seen in wild-type mouse brain. Both the 37-kDa apoEs and 39-kDa apoEs2 are coprecipitated with native 34-kDa apoE by antibody to human apoE. Neuraminidase digestion eliminates the 37- and 39-kDa forms and results in a downward shift in the bands to the position of the 34-kDa native form. These sialylated apoE isoproteins are found preferentially associated with neurons and contribute significantly (50-60%) to the total neuronal apoE in neuronal cultures from transgenic mice, while only 5-10% of total apoE is sialylated in cultures enriched in glial cells. In situ hybridization and immunocytochemistry demonstrate apoE mRNA and apoE immunoreactivity are predominantly located in cell soma of neurons, not in neuronal processes.

Animals↗
PubMed1999

A role for apoE in regulating the levels of alpha-1-antichymotrypsin in the aging mouse brain and in Alzheimer's disease.

This study was designed to explore the possible functional relationships between apolipoprotein E (apoE) and the protease inhibitor alpha-1-antichymotrypsin in the aging mouse brain and in Alzheimer's disease. For this purpose, levels of EB22/5 (the mouse homologue to human alpha-1-antichymotrypsin) mRNA expression was studied in apoE-deficient mice. These mice showed an age-dependent increase of EB22/5 mRNA expression in the brain. Furthermore, overexpression of allele 3 of human APOE gene in transgenic mice (in an apoE-deficient background) resulted in normalization of levels of EB22/5 mRNA expression compatible with levels found in control mice. In contrast, overexpression of human APOE4 allele or down-regulation of the apoE receptor low density lipoprotein receptor-related protein by deletion of the receptor-associated protein was associated with elevated levels of EB22/5 similar to apoE-deficient mice. Consistent with the findings in murine models, human alpha-1-antichymotrypsin protein was increased in brain homogenates from patients with Alzheimer's disease, and levels of this serpin were the highest in patients with the APOE4 allele. In summary, the present study showed evidence supporting a role for apoE in regulating alpha-1-antichymotrypsin expression. This is relevant to Alzheimer's disease because these two molecules appear to be closely associated with the pathogenesis of this disorder.

Aging↗
PubMed1999

Specific regional transcription of apolipoprotein E in human brain neurons.

In central nervous system injury and disease, apolipoprotein E (APOE, gene; apoE, protein) might be involved in neuronal injury and death indirectly through extracellular effects and/or more directly through intracellular effects on neuronal metabolism. Although intracellular effects could clearly be mediated by neuronal uptake of extracellular apoE, recent experiments in injury models in normal rodents and in mice transgenic for the human APOE gene suggest the additional possibility of intraneuronal synthesis. To examine whether APOE might be synthesized by human neurons, we performed in situ hybridization on paraffin-embedded and frozen brain sections from three nondemented controls and five Alzheimer's disease (AD) patients using digoxigenin-labeled antisense and sense cRNA probes to human APOE. Using the antisense APOE probes, we found the expected strong hybridization signal in glial cells as well as a generally fainter signal in selected neurons in cerebral cortex and hippocampus. In hippocampus, many APOE mRNA-containing neurons were observed in sectors CA1 to CA4 and the granule cell layer of the dentate gyrus. In these regions, APOE mRNA containing neurons could be observed adjacent to nonhybridizing neurons of the same cell class. APOE mRNA transcription in neurons is regionally specific. In cerebellar cortex, APOE mRNA was seen only in Bergmann glial cells and scattered astrocytes but not in Purkinje cells or granule cell neurons. ApoE immunocytochemical localization in semi-adjacent sections supported the selectivity of APOE transcription. These results demonstrate the expected result that APOE mRNA is transcribed and expressed in glial cells in human brain. The important new finding is that APOE mRNA is also transcribed and expressed in many neurons in frontal cortex and human hippocampus but not in neurons of cerebellar cortex from the same brains. This regionally specific human APOE gene expression suggests that synthesis of apoE might play a role in regional vulnerability of neurons in AD. These results also provide a direct anatomical context for hypotheses proposing a role for apoE isoforms on neuronal cytoskeletal stability and metabolism.

Adult↗
PubMed1999

Analysis of the Stargardt disease gene (ABCR) in age-related macular degeneration.

PURPOSE: Age-related macular degeneration (AMD) is a complex genetic disorder and the leading cause of severe vision loss in the elderly. The Stargardt disease gene (ABCR) has been proposed as a major genetic risk factor in AMD. The purpose of this study was to evaluate the authors' AMD population for the specific ABCR variants proposed previously as genetic risk factors for AMD. METHODS: The authors screened their AMD population (159 familial cases from 112 multiplex families and 53 sporadic cases) and 56 racially matched individuals with no known history of AMD from the same clinic population for evidence of the ABCR variants. Grading of disease severity was performed according to a standard protocol. Patients with extensive intermediate drusen or large soft drusen, drusenoid retinal pigment epithelial (RPE) detachments, geographic atrophy of the RPE, or evidence of exudative maculopathy were considered affected. Analysis for variants was performed by polymerase chain reaction amplification of individual exons of the ABCR gene with flanking primers and a combination of single-strand conformation polymorphism, heteroduplex analysis, and high-performance liquid chromatography. All abnormal conformers detected using these techniques were characterized by direct sequencing. RESULTS: The authors identified only two of the previously reported variants in their study population. Both variants occurred in sporadic cases, and none was found in familial cases or the randomly selected population. In addition, the authors identified several newly described polymorphisms and variants in both the AMD and control populations. CONCLUSIONS: Based on these initial findings, the authors suggest that ABCR is not a major genetic risk factor for AMD in their study population. Additional genetic studies are needed to more fully evaluate the role of ABCR in AMD.

ATP-Binding Cassette Transporters↗
PubMed1999

Human apolipoprotein E isoform-specific differences in neuronal sprouting in organotypic hippocampal culture.

The apolipoprotein E (ApoE) epsilon4 allele is a major risk factor for neurodegenerative conditions, including Alzheimer's disease. A role for ApoE is implicated in regeneration of synaptic circuitry after neural injury. In the in vitro mouse organotypic hippocampal slice culture system, we previously showed that cultures derived from ApoE-knockout mice are defective in mossy fiber sprouting into the dentate gyrus molecular layer. This sprouting defect was rescued in cultures from transgenic mice expressing ApoE3 under the control of the human promoter and in ApoE-knockout cultures treated with ApoE3-conditioned media. Although the ApoE3 transgene fully restored sprouting, ApoE4 restored sprouting to only 58% of ApoE3 levels. These data indicate that ApoE isoform-specific effects on neuroregeneration may contribute to its genetic risk for Alzheimer's disease.

Alzheimer Disease↗
PubMed1998

Regionally specific neuronal expression of human APOE gene in transgenic mice.

Apolipoprotein E (APOE, gene; apoE, protein) is a susceptibility gene for late-onset Alzheimer's disease (AD). To examine whether neurons can synthesize apoE, we performed in situ hybridization on brain tissue of transgenic mice carrying genomic constructs for the three major human APOE alleles. We find human APOE mRNA in glial cells of cerebellum, striatum and cerebral cortex and also in neurons of cerebral cortex, corresponding to apoE localization in humans. Synthesis of apoE by neurons implies that models of AD may need to consider intrinsic apoE production in addition to uptake. Inclusion of human regulatory sequences may result in more realistic transgenic models of human disease.

Alleles↗
PubMed1998

Bioavailability and pharmacokinetics of microencapsulated 1,3-dichloropropene in rats.

The potential oral toxicity of 1,3-dichloropropene (1,3-D) has been evaluated in a number of dietary toxicity studies. The relatively high vapor pressure of 1,3-D, its short half-life in drinking water, and its reactivity with constituents of feed necessitated the use of a microencapsulated formulation (starch-sucrose shell) of 1,3-D in these studies. The bioavailability of ingested microencapsulated 1,3-D was determined by characterizing and comparing the kinetics of 1,3-D in the blood of female F344 rats coadministered microencapsulated 1,3-D and neat 13C-1,3-D (25 mg/kg each) via gavage. Blood concentrations of total or cis- and trans-isomers of 1,3-D in treated rats were determined using gas chromatography-mass spectroscopy (GC-MS) or in situ membrane extraction MS. Urine was also collected and analyzed by GC-MS for the presence of the mercapturate excretion product of 1,3-D [N-acetyl-S-(3-chloropropenyl-2)-L-cysteine; 1,3-DMA]. Blood levels of 1,3-D and 13C-1,3-D displayed similar kinetics, peaking within 10 min of dosing followed by a rapid biphasic elimination. Higher peak blood levels and greater blood curve areas (AUC) were attained for trans- than cis-1,3-D and 13C-1,3-D and greater amounts of cis- than trans-1,3-DMA and 13C-1,3-DMA were excreted in the urine consistent with the known rapid and disproportionate glutathione conjugation of the cis-isomer in the gastric mucosa. Slightly higher cis-1,3-D than cis-13C-1,3-D blood levels and AUCs were also consistently noted while the reverse was true for urinary excretion of cis-13C-1,3-DMA and cis-1,3-DMA suggesting that 1,3-D derived from microencapsulated test material may be absorbed and/or metabolized in the stomach mucosa at a slightly slower rate than that from neat material. The latter, however, would be of no consequence during the administration of 1,3-D to animals via their diets as competing test materials would not be present and 1,3-D blood kinetics were unaffected. Overall, the results of this study demonstrate the ready bioavailability of microencapsulated 1,3-D and rapid elimination of 1,3-D from the blood of rats.

Allyl Compounds↗
PubMed1998

Mutation and polymorphism analysis in the tuberous sclerosis 2 (TSC2) gene.

Tuberous sclerosis complex (TSC) is an autosomal dominant multi-system disorder with two known disease loci on chromosomes 9q34 (TSC1) and 16p13.3 (TSC2). TSC has a prevalence of approximately 1 in 5,000-6,000, exhibits incomplete penetrance, and occurs in all racial groups. Our laboratory has undertaken the complete mutation analysis of the TSC2 gene in 42 TSC families using single-strand conformation polymorphism analysis and reverse transcription-polymerase chain reaction. Of the total of 42 families, 16 show evidence of linkage to the chromosome 16 TSC2 locus and 26 are either sporadic or too small to establish chromosome linkage. The TSC2 gene spans at least 45 kilobases of genomic DNA, has 41 known exons, and codes for a 5,474-base pair transcript. After complete gene analysis, 16 TSC2 mutations have been identified, including DNA insertions, deletions, splice site mutations, and amino acid substitutions. The majority of putative TSC2 mutations were found in sporadic rather than TSC2-linked families. We have also detected 15 polymorphisms which occur in the TSC2 gene.

Amino Acid Substitution↗
PubMed1998

Meeting report: International Childhood ALL Workshop: Memphis, TN, 3-4 December 1997.

The cure of childhood acute lymphoblastic leukemia (ALL) was a momentous achievement in the history of medicine. It demonstrated that widely disseminated cancers can be eradicated with cytotoxic drugs, and it illustrated the power of systematic laboratory studies and randomized clinical trials applied to a single disease. As ALL cure rates edge towards 80%, several key challenges are apparent. First, it will be important to devise more effective therapies for the high-risk patients who continue to relapse on contemporary protocols. Second, better methods of disease assessment and treatment are needed to avoid relapses that still occur in so-called low- and intermediate-risk groups. Third, the persistence of late adverse effects due to radiation and certain genotoxic agents, such as the anthracycline compounds and the epipodophyllotoxins, mandates the development of alternative therapies that are both safe and effective in children. The International Childhood ALL Workshop, held 3-4 December 1997, at St Jude Children's Research Hospital in Memphis, Tennessee, brought together leading experts in leukemia therapy to discuss progress in meeting these and other challenges, and to suggest directions for future studies. The participants, from 12 co-operative study groups and two individual centers, were welcomed by Dr A Nienhuis (St Jude Director), who provided the historical context for the workshop, and by Drs W Evans and C-H Pui, the meeting co-organizers.

Antineoplastic Agents↗
PubMed1997

Interferon-gamma modulates a p53-independent apoptotic pathway and apoptosis-related gene expression.

Interferon (IFN)-gamma increases the sensitivity of tumor cell lines, many of which are p53 mutants, to tumor necrosis factor-alpha-mediated and anti-Fas antibody-mediated cell death. To better understand the mechanism of IFN-gamma action in modulating the cell death response independently of p53 function, we analyzed the death of the human colon adenocarcinoma cell line, HT-29, following treatment with IFN-gamma and various cytotoxic agents. Here we show that IFN-gamma modulates cell death by sensitizing the cells to killing by numerous pro-apoptotic stimuli but not pro-necrotic stimuli. Furthermore, we show that select genes from several important apoptosis-related gene families are induced by IFN-gamma, including the apoptosis-signaling receptors CD95 (Fas/APO-1) and TNFR 1 and interleukin-1beta-converting enzyme (Ice) family members Ice, CPP32 (Yama, apopain), ICErel-II (TX, Ich-2), Mch-3 (ICE-LAP3, CMH-1), Mch-4, and Mch-5 (MACH, FLICE). Of the bcl-2 family members, IFN-gamma directly induced bak but notably not bax, which is activated by p53. The IFN-responsive transcriptional activator interferon regulatory factor-1 was also strongly induced and translocated into the nucleus following IFN-gamma treatment. We propose that IFN-gamma modulates a p53-independent apoptotic pathway by both directly and indirectly inducing select apoptosis-related genes.

Apoptosis↗
PubMed1997

Further exclusion of FSHD1B from the telomeric region of 10q.

The localization of the gene for the majority of cases of facioscapulohumeral muscular dystrophy is established as 4q35-qter (FSHD1A), although locus heterogeneity has been demonstrated with a minority of families unlinked to 4q. In FSHD1A, the disease is associated with a deletion of 3.3 kb repeats from a tandem repeat located near the as-yet-unidentified gene. This repeat cross-hybridizes with a telomeric region on 10q, making this cross-hybridizing region a feasible candidate gene for FSHD1B. We have tested the most telomeric marker on 10q (sAVA4) and excluded approximately 17 cM on either side of this marker as harboring the FSHD1B gene.

Alleles↗
PubMed1996

Human apolipoprotein E2, E3, and E4 isoform-specific transgenic mice: human-like pattern of glial and neuronal immunoreactivity in central nervous system not observed in wild-type mice.

Apolipoprotein E (apoE) and its three major alleles (APOE2, E3, and E4) have been implicated in Alzheimer's disease and other neurological disorders. Little is known of the role apoE plays in normal brain function and pathology. To create a model to study apoE in brain, we have generated APOE transgenic mice using microinjection of allele-specific human genomic fragments to establish founders which were then bred to APOE knockout mice lacking a functional mouse apoE protein. This allows the study of apoE without interference from the endogenous mouse APOE gene. Results demonstrate that transgenic lines have been established that transcribe and express apoE appropriately in brain, liver, and other tissues. High cholesterol levels found in APOE knockout mice are substantially corrected in the APOE transgenic lines. ApoE immunoreactivity has been detected in glial cells and selected classes of neurons in all three isoform-specific transgenics. This pattern of immunoreactivity is similar to that observed in nonhuman primates and man, and contrasts with the strictly glial staining pattern of normal rodents.

Alleles↗
PubMed1996

Evidence for locus heterogeneity in the Bethlem myopathy and linkage to 2q37.

The Bethlem myopathy, a childhood onset autosomal dominant myopathy with joint contractures, has recently been localized to 21q in a series of Dutch families and the alpha 1 and alpha 2 subunits of type VI collagen (COL6A1 and COL6A2) have been postulated as candidate genes. We investigate a large family of French Canadian descent (family 1489) in which the Bethlem myopathy is segregating. Family 1489 is unlinked to the region of interest on 21q, thus demonstrating locus heterogeneity within the Bethlem myopathy classification. In view of the localization of the genes coding the alpha 1 and alpha 2 subunits of type VI collagen on chromosome 21q, we carried out linkage analysis on chromosome 2q where the alpha 3 subunit of type VI collagen has been localized. We demonstrate linkage to markers in this region, define the region of disease gene localization, and confirm by FISH analysis that COL6A3 is located within the interval of interest making COL6A3 a feasible candidate gene for the Bethlem myopathy.

Chromosome Mapping↗
PubMed1995

Mutation analysis of the TSC2 gene in an African-American family.

Tuberous sclerosis complex is an autosomal dominant disorder with loci on chromosome 9q34 (TSC1) and chromosome 16p13.3 (TSC2). The TSC2 gene has been isolated. To date, only a small number of intragenic deletional and point mutations have been detected, almost exclusively in sporadic (no family history) cases. With the exception of a single parent/offspring pair, there have been no published reports of mutations in extended multigenerational chromosome 16-linked TSC2 families. For our TSC studies we ascertained and sampled a four-generation African-American TSC family that shows a high likelihood for linkage to chromosome 16 (z=1.53). Using single-strand conformation polymorphism analysis we identified a 4590/4591delC mutation in exon 34. The 4590/4591delC causes a frameshift mutation resulting in the creation of a premature stop codon. In addition, we have detected a 542del4 polymorphism in the two partially overlapping polyadenylation signals in exon 40 that segregates in the family. The polymorphism has been detected in six of 72 African-American control chromosomes examined, and has not been detected in 80 Caucasian control chromosomes examined.

Amino Acid Sequence↗