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Biomedical subjects

C Beard

Publications and source records attributed to C Beard.

At least 37 records · Page 2Linked to original sources
PubMed1995

Loss of methylation activates Xist in somatic but not in embryonic cells.

The mouse Xist gene, which is expressed only from the inactive X chromosome, is thought to play a role in the initiation of X inactivation. The 5' end of this gene is fully methylated on the active X chromosome and completely demethylated on the inactive X chromosome, suggesting that DNA methylation may be involved in controlling allele-specific transcription of this gene. To directly investigate the importance of DNA methylation in the control of Xist expression, we have examined its methylation patterns and expression in ES cells and embryos that are deficient in DNA methyltransferase activity. We report here that demethylation of the Xist locus in male mutant embryos induces Xist expression, thus establishing a direct link between demethylation and expression of the Xist gene in the postgastrulation embryo. The transcriptional activity of Xist in undifferentiated ES cells, however, appears to be independent of its methylation status. These results suggest that methylation may only become essential for Xist repression after ES cells have differentiated or after the embryo has undergone gastrulation.

Animals↗
PubMed1995

Changes in the contact system during orthotopic liver transplantation with and without aprotinin.

The main cause of nonsurgical bleeding during orthotopic liver transplantation has been attributed to be hyperfibrinolysis due to high plasma levels of tissue plasminogen activator. The aim of this study was to investigate contact activation and its possible contribution to fibrinolysis during OLT with and without aprotinin. Aprotinin or placebo was given to 20 patients undergoing OLT as part of a randomized double-blind trial. Plasma samples were collected before, during, and after OLT. There were decreased preoperative levels of prekallikrein and factor XIIa (P < 0.05), with a trend for kallikrein and factor XIIa activity to increase during OLT peaking on reperfusion (P < 0.05). Kallikrein inhibition, C1 esterase inhibitor, and alpha-2-macroglobulin levels were normal before surgery, with low normal levels of antithrombin III and alpha-2-antiplasmin; these levels decreased during OLT with no specific change on reperfusion. In the aprotinin-treated group, kallikrein inhibition levels increased (P < 0.05) from preoperative mean (+/- SD) values of 101 +/- 47% to 154 +/- 42% and antiplasmin levels increased (P < 0.05) from 72 +/- 28% to 243 +/- 53% during the anhepatic phase, reflecting the effect of aprotinin. The antifibrinolytic effect of aprotinin was demonstrated by decreased levels of D-dimer on reperfusion (P < 0.05) and at the end of OLT (P < 0.001) in the aprotinin-treated group. We have shown that contact activation during OLT is minimal and that aprotinin does not alter the pattern of contact activation, but provides an antikallikrein effect.

Adult↗
PubMed1994

Fibrinolytic activity during orthotopic liver transplantation with and without aprotinin.

Hyperfibrinolysis during orthotopic liver transplantation (OLT) has been attributed to high plasma levels of tissue plasminogen activator (t-PA). This study investigated the contribution of urokinase plasminogen activator (u-PA) to hyperfibrinolysis and the effects of high-dose perioperative aprotinin (Trasylol) on fibrinolytic activation. Plasma samples were collected before, during, and after OLT in fifty five patients receiving either high dose aprotinin or placebo in a randomized double-blind trial. t-PA antigen and u-PA antigen and activity levels were increased preoperatively compared with normal controls (P < 0.05). Hyperfibrinolysis was seen during the anhepatic phase as shown by shortened euglobulin clot lysis times (ECLT) and an increase in D-dimer titers. t-PA levels peaked on reperfusion and fell at the end of the operation, and u-PA levels did not increase during OLT, but showed a decrease at the end of the operation. With aprotinin treatment, t-PA levels were lower on graft reperfusion than the placebo group (P < 0.05), but there was no difference in u-PA antigen or activity levels between groups. Fibrinolytic inhibition during OLT by aprotinin was demonstrated by prolonged ECLT (P < 0.05), reduced D-dimer levels (P < 0.05), and an increase in antiplasmin activity (P < 0.05). This study showed that the main antifibrinolytic action of aprotinin is as an antiplasmin agent with some effect on t-PA-but not u-PA-mediated fibrinolysis.

Adult↗
PubMed1994

Phase II trial of external beam radiation with etanidazole (SR 2508) for the treatment of locally advanced prostate cancer.

PURPOSE: To evaluate the efficacy and toxicity of the addition of etanidazole (ETA) to external beam radiation. METHODS AND MATERIALS: Fifty eight previously untreated patients with locally advanced adenocarcinoma of the prostate were entered on a Phase II trial of etanidazole (ETA) combined with standard external beam radiation therapy. ETA was given concurrently with irradiation. Four patients received less than 25% of the intended dose of ETA and were ineligible for further analysis. The stage of the remaining patients were T2c-11, T3-39, T4-1, bulky local recurrence after prostatectomy-1, and T3, N1-2. RESULTS: Forty-five of 54 patients (83.3%) achieved a clinical complete response (CCR) in the prostate and seminal vesicles as judged by digital rectal exam (DRE). Responses were rapid with a median time to CCR of 3.4 months, range 0-22.8 months. Local control was maintained in 82% of the patients who achieved a CCR. Fifteen of 32 eligible patients with a normal DRE underwent prostate biopsies from 12-20 months after treatment, seven had negative biopsies (46.6%). Distant metastases occurred in 18 patients (33.3%). Pretreatment prostatic specific antigen (PSA), Gleason score, and stage were not associated with treatment outcome in a univariate analysis. CONCLUSION: While ETA plus radiation was associated with a rapid CCR, the overall treatment outcome of these patients appeared to be similar to published reports of patients receiving RT alone. The rapid response rate may imply biologic activity of the ETA. In future trials, it may be reasonable to focus on patients at lower risk for the subsequent development of distant disease.

Adenocarcinoma↗
PubMed1993

Role for DNA methylation in genomic imprinting.

The paternal and maternal genomes are not equivalent and both are required for mammalian development. The difference between the parental genomes is believed to be due to gamete-specific differential modification, a process known as genomic imprinting. The study of transgene methylation has shown that methylation patterns can be inherited in a parent-of-origin-specific manner, suggesting that DNA methylation may play a role in genomic imprinting. The functional significance of DNA methylation in genomic imprinting was strengthened by the recent finding that CpG islands (or sites) in three imprinted genes, H19, insulin-like growth factor 2 (Igf-2), and Igf-2 receptor (Igf-2r), are differentially methylated depending on their parental origin. We have examined the expression of these three imprinted genes in mutant mice that are deficient in DNA methyltransferase activity. We report here that expression of all three genes was affected in mutant embryos: the normally silent paternal allele of the H19 gene was activated, whereas the normally active paternal allele of the Igf-2 gene and the active maternal allele of the Igf-2r gene were repressed. Our results demonstrate that a normal level of DNA methylation is required for controlling differential expression of the paternal and maternal alleles of imprinted genes.

Alleles↗
PubMed1993

Germ line transmission of a yeast artificial chromosome spanning the murine alpha 1(I) collagen locus.

Molecular complementation of mutant phenotypes by transgenic technology is a potentially important tool for gene identification. A technology was developed that allows the transfer of a physically intact yeast artificial chromosome (YAC) into the germ line of the mouse. A purified 150-kilobase YAC encompassing the murine gene Col1a1 was efficiently introduced into embryonic stem (ES) cells via lipofection. Chimeric founder mice were derived from two transfected ES cell clones. These chimeras transmitted the full length transgene through the germ line, generating two transgenic mouse strains. Transgene expression was visualized as nascent transcripts in interphase nuclei and quantitated by ribonuclease protection analysis. Both assays indicated that the transgene was expressed at levels comparable to the endogenous collagen gene.

Animals↗
PubMed1991

Analysis of splice junctions and in vitro and in vivo translation potential of the small, abundant B19 parvovirus RNAs.

Two parvovirus B19 cDNA libraries have been constructed; one from COS-7 cells transfected with a B19/pSVOd hybrid vector and the other from B19-infected human erythroid leukemic cells. We have used these libraries to investigate the expression of the abundant classes of polyadenylated B19 RNAs; the 700- and 800-nt class which terminates in the middle of the genome and the 500- and 600-nt class which contains an ORF from the extreme right-hand end of the genome. The 700- and 800-nt RNA species were not found in the COS cell library, suggesting that a variant polyadenylation signal (ATTAAA or AATAAC) in the middle of the genome is not efficiently recognized in these cells. In contrast, the 700- and 800-nt class was highly represented in the human library, confirming the use of this variant polyadenylation signal in the normal host cell of the virus. In COS cells the middle exon of the 500- and 600-nt class of RNA exhibited variability in both splice donor and acceptor sites. However, in human cells there were only two splice acceptor sites nt 1910 and 2030, and a single splice donor site nt 2183 for this exon. Antisera, prepared against a peptide derived from the 94-aa potential protein encoded by the 500- and 600-nt class of RNA, recognized, on a Western blot, a polypeptide of approximately 11 kDa that was translated in vitro from these cDNAs and in vivo in pSVOd/B19 transfected COS cells. Immunoprecipitation revealed that two proteins were made from this ORF, suggesting the use of internal translation initiation site(s). Another antisera, raised against a second peptide corresponding to an antigenic region of the potential protein encoded by the 700- and 800-nt class of RNA, failed to detect a 15-kDa protein by Western blotting or immunoprecipitation of labeled proteins both in vitro and in vivo in COS cells.

Amino Acid Sequence↗
PubMed1990

Dermolipoma surgery, or, "an ounce of prevention is worth a pound of cure".

The surgery of dermolipoma is fraught with dangers. It too often is followed by damage to the lacrimal secretory system, intractable diplopia, blepharoptosis, and perhaps other undesirable complications. Since these tumors are benign, the smallest amount of surgery that debulks the tumor and leads to a cosmetically acceptable result is the best surgery for the patient's satisfaction and for the surgeon's peace of mind. By being aware of these factors, the surgeon can avoid most complications. Some methods of preventing and relieving the symptoms of potential complications of dermolipoma surgery are briefly considered.

Blepharoptosis↗
PubMed1989

Transient expression of B19 parvovirus gene products in COS-7 cells transfected with B19-SV40 hybrid vectors.

Hybrid B19 parvovirus-SV40 origin vectors were transfected into COS-7 cells and replication of these plasmids studied. Plasmids that have a frameshift mutation within the nonstructural gene region replicated to high level (copy number approximately 10,000/transfected cell) although somewhat lower than pSVOd, the SV40 origin vector without B19 sequence (copy number approximately 100,000/transfected cell). However, hybrid B19 parvovirus-SV40 origin vectors that do not contain these frameshift mutations replicated to a much lower level (copy number approximately 1000/transfected cell). Although the hybrid vectors studied replicated at different efficiencies in COS-7 cells, they are transcribed at approximately the same level, resulting in RNA species that are indistinguishable from those seen in B19 virus-infected erythroid bone marrow cells. Western blot analysis demonstrated that the mRNAs are translated into polypeptides of the same size and, in the case of viral structural proteins, in same relative abundance as seen in a B19-infected clinical sample.

Blotting, Northern↗
PubMed1989

Segmental spinal instrumentation for neuromuscular spinal deformity.

Seventy-six consecutive surgical cases of paralytic neuromuscular spinal deformity were retrospectively analyzed. Posterior arthrodesis with segmental spinal stabilization with Luque L-rods, sometimes preceded by anterior release, was done in all cases. The infection rate of 14.5% was observed to be markedly higher in patients with myelodysplasia. Deep placement of the rods lateral to the spine and well beneath full-thickness skin is recommended to reduce the incidence of this complication.

Adolescent↗
PubMed1988

Full-thickness unipedicle flap for lower eyelid reconstruction.

We developed a technique for lower eyelid reconstruction using a full-thickness unipedicle flap from the upper tarsal portion of the upper eyelid. The lost tissue is replaced with identical tissue from the ipsilateral upper eyelid. The technique is best suited to shallow defects of the temporal lower eyelid. The levator aponeurosis and Müller's muscle are recessed to avoid upper eyelid retraction. The key to performing this operation is a thorough knowledge of eyelid anatomy and preservation of its microvascular supply. This procedure has produced satisfactory to excellent results in 17 patients and offers the reconstructive surgeon several advantages over other techniques.

Eyelid Neoplasms↗
PubMed1987

In vitro identification of a B19 parvovirus promoter.

The nucleotide sequence of the B19-Wi isolate of human parvovirus was determined and compared throughout the open reading frames and putative transcription signals with the sequence of the closely related B19-Au isolate. In vitro run off transcription assays, using B19-Wi DNA as the template, indicated that there is a strong promoter between m.u. 5 and 7. Deletion clones show that a region between nt 258 and 321 is necessary for in vitro transcriptional activity. Primer extension studies identified the start site at 31-32 nucleotides downstream of the sequence TATATATA. The strength of this left-hand promoter is unusual among parvovirus promoters characterized to date, and the possibility of an upstream enhancer element is discussed.

Base Sequence↗