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Biomedical subjects

P A Norton

Publications and source records attributed to P A Norton.

At least 19 recordsLinked to original sources
PubMed2000

Roles of tissue transglutaminase in ethanol-induced inhibition of hepatocyte proliferation and alpha 1-adrenergic signal transduction.

The mechanisms by which ethanol inhibits hepatocyte proliferation have been a source of some considerable investigation. Our studies have suggested a possible role for tissue transglutaminase (tTG) in this process. Others have shown that tTG has two distinctly different functions: it catalyzes protein cross-linking, which can lead to apoptosis and enhancement of extracellular matrix stability, and it can function as a G protein (Galpha(h)). Under that circumstance, we speculated that the cross-linking activity would be decreased and that it would function to enhance hepatocyte proliferation in response to adrenergic stimulation. Ethanol treatment inhibited hepatocyte proliferation and led to enhanced tTG cross-linking activity, whereas treatment of hepatocytes with an alpha1 adrenergic agonist, phenylephrine, enhanced hepatocyte proliferation while decreasing tTG cross-linking. However, phenylephrine treatment of several hepatoma cell lines had no effect on cellular proliferation or tTG cross-linking activity, and of note, Northern blot analysis demonstrated that whereas primary hepatocytes had high levels of the alpha1beta adrenergic receptor (alpha1BAR) mRNA, the hepatoma cell lines did not have this mRNA. When the Hep G(2) cell line was stably transduced with an expression vector containing the alpha1BR cDNA, the cell line responded to phenylephrine treatment with enhanced proliferation and with decreased tTG cross-linking activity. Ethanol treatment of the alpha1BAR-transfected cells suppressed the phospholipase C-mediated signaling pathways, as detected in the phenylephrine-induced Ca(2+) response. These results suggest that phenylephrine stimulation of hepatocyte proliferation appears to be occurring through the alpha1BAR, which is known to be coupled with the tTG G protein moiety, Galpha(h), and that tTG appears to play a significant role in either enhancing or inhibiting hepatocyte proliferation, depending on its cellular location and on whether it functions as a cross-linking enzyme or a G protein.

Animals↗
PubMed2000

The role of vaginal apex excision in the management of persistent posthysterectomy dyspareunia.

OBJECTIVE: The purpose of this study was to evaluate the effectiveness of vaginal apex excision in the treatment of patients with posthysterectomy dyspareunia. STUDY DESIGN: This was a case series with an independent third-party survey of patients with posthysterectomy dyspareunia managed at the University of Utah Pelvic Pain Clinic. Thirteen patients were first treated with local injections of anesthetics into localized vaginal pain foci. Further evaluation included formal psychometric testing and a diagnostic spinal block. Nine patients underwent surgical excision of the vaginal apex. An independent interviewer who did not know the patients assessed the effects of this procedure on dyspareunia and coital frequency at a mean of 36.4 +/- 3.7 months after the operation. RESULTS: The mean coital verbal analog pain score (1-10 scale) decreased from 9.22 +/- 0.27 before excision of the vaginal apex to 3.11 +/- 0.84 after the operation (P <.001), and coital frequency improved from 5.22 +/- 2.02 episodes per month before surgery to 11.11 +/- 1.82 episodes per month after surgery (P =.02). Of the 9 patients, 5 essentially had the dyspareunia cured. Dyspareunia was decreased and coital frequency was markedly increased in all but 1 of the other 4 cases. CONCLUSION: Excision of the vaginal apex is an effective treatment for carefully selected patients with posthysterectomy dyspareunia.

Adult↗
PubMed2000

Dyspareunia and recurrent stress urinary incontinence after laparoscopic colposuspension with mesh and staples. A case report.

BACKGROUND: A laparoscopic colposuspension technique using hernia staples and polypropylene mesh has been introduced for the treatment of stress urinary incontinence but is not without hazards. CASE: A 32-year-old woman developed recurrent stress urinary incontinence and dyspareunia approximately one year after undergoing laparoscopic colposuspension with hernia staples and polypropylene mesh. Metal staples palpated vaginally corresponded with the area of maximal tenderness, and the bladder neck was hypermobile. Upon surgical exploration of the space of Retzius, four staples were found in the bladder wall, and polypropylene mesh densely adherent to the bladder wall had eroded into the muscularis. CONCLUSION: Laparoscopic colposuspension with hernia staples and polypropylene mesh may be associated with early recurrence of incontinence and dyspareunia.

Adult↗
PubMed1999

Accurate selection of a 5' splice site requires sequences within fibronectin alternative exon B.

Inclusion of fibronectin alternative exon B in mRNA is developmentally regulated. Here we demonstrate that exon B contains two unique purine-rich sequence tracts, PRE1 and PRE2, that are important for proper 5' splice site selection both in vivo and in vitro. Targeted mutations of both PREs decreased the inclusion of exon B in the mRNA by 50% in vivo. Deletion or mutation of the PREs reduced removal of the downstream intron, but not the upstream intron, and induced the activation of cryptic 5' splice sites in vitro. PRE-mediated 5' splice selection activity appears sensitive to position and sequence context. A well characterized exon sequence enhancer that normally acts on the upstream 3' splice site can partially rescue proper exon B 5' splice site selection. In addition, we found that PRE 5' splice selection activity was preserved when exon B was inserted into a heterologous pre-mRNA substrate. Possible roles of these unique activities in modulating exon B splicing are considered.

5' Untranslated Regions↗
PubMed1999

Alternative splicing during chondrogenesis: cis and trans factors involved in splicing of fibronectin exon EIIIA.

Primary chicken mesenchymal cells from limb buds and vertebral chondrocytes have been used to study the changes that occur in alternative mRNA splicing of fibronectin exon EIIIA during chondrogenesis. The mesenchymal cell phenotype (exon EIIIA included) and chondrocyte phenotype (exon EIIIA excluded) were preserved in culture. Both primary cell types were transfected with an EIIIA minigene and alternative splicing was monitored by S1 protection assay. Differential cell-specific splicing of the reporter was observed. The roles of two regulatory elements, an exon splicing enhancer (ESE) and an exon splicing silencer (ESS) were examined. Both elements were required for EIIIA inclusion into mRNA in mesenchymal cells. Gel mobility shift assays revealed that both chondrocyte- and mesenchymal cell-derived nuclear extracts contained exon EIIIA binding factors, but the RNA binding factors present in the two cell types appeared to be distinct. The ESE and ESS appeared to cooperate in the formation of both cell type-specific complexes. These results suggest a model in which inhibitory factors enriched in chondrocytes compete with positive factors enriched in mesenchymal cells for binding to exon EIIIA, determining whether the exon is included.

Alternative Splicing↗
PubMed1999

Urinary incontinence in pregnancy and the puerperium: a prospective study.

OBJECTIVE: Pregnancy and childbirth are commonly thought to be associated with the development of urinary incontinence and lower urinary tract symptoms. The purpose of this study was to assess the relationship, if any, between pregnancy and the development of lower urinary tract symptoms. STUDY DESIGN: A prospective study of lower urinary tract symptoms was carried out in a cohort of pregnant women who answered a series of symptom questionnaires and kept a 24-hour bladder chart on which frequency of urination and volumes voided were recorded throughout pregnancy and for 8 weeks after birth. RESULTS: A total of 123 women participated in the study. Mean daily urine output (P =.01) and the mean number of voids per day (P =.01) increased with gestational age and declined after delivery. Episodes of urinary incontinence peaked in the third trimester and improved after birth (P =.001). White women had higher mean voided volumes and fewer voiding episodes than did black women. Ingestion of caffeine was associated with smaller voided volumes and greater frequency of urination. CONCLUSION: Pregnancy is associated with an increase in urinary incontinence. This phenomenon decreases in the puerperium. Pregnancy and childbirth trauma are important factors in the development of urinary incontinence among women. These findings warrant further investigation.

Female↗
PubMed1998

A highly conserved region upstream of the fibronectin alternative exon EIIIA 3' splice site interacts with cell-type-specific nuclear proteins.

Sequencing of chicken fibronectin genomic DNA and interspecies sequence comparisons reveal a highly conserved region upstream of the alternatively spliced exon EIIIA. UV-crosslinking of RNAs corresponding to this region from the chicken and rat genes with HeLa nuclear extract demonstrates that both RNAs interact with similar proteins. However, both RNAs crosslink to a 70 kDa protein present in nuclear extracts from cells and tissues that include exon EIIIA, but not in extracts from tissues that exclude the exon. This protein represents a candidate cell-type-specific factor involved in exon EIIIA inclusion.

Alternative Splicing↗
PubMed1998

Epidemiology and natural history of pelvic floor dysfunction.

Pelvic floor dysfunction, including urinary incontinence, anal incontinence, and pelvic organ prolapse, is extremely common, affecting at least one-third of adult women. A minority of patients sustaining these conditions volunteer their symptoms. Risk factor identification and the development of tactics for prevention are significant priorities for future research. Understanding both the specific predisposing factors that place an individual woman at risk and the precise events of the labor and delivery process that initiate injury and dysfunction is important for primary prevention. Defining the relative importance of various promoting and decompensating factors is essential for secondary prevention.

Adolescent↗
PubMed1997

Reduction in fibronectin expression and alteration in cell morphology are coincident in NIH3T3 cells expressing a mutant E2F1 transcription factor.

Fibronectin within the extracellular matrix plays a role in cell attachment, spreading, and shape, while it also affects aspects of cell proliferation. Transcription factors such as E2F1 are also known to regulate cell shape and cell proliferation. Yet, to date no linkage has been established between fibronectin expression and E2F1. We show here that cells constitutively expressing a mutant E2F1 protein (E2F1d87) produce reduced amounts of fibronectin mRNA and protein. The altered expression of fibronectin seen in the E2F1d87 expressing cells is due, in part, to a reduction in transcription from the fibronectin promoter. Providing exogenous fibronectin, but not Type I collagen or laminin, as a substrate for cell adhesion is sufficient to revert the altered morphology and reestablish actin-containing microfilaments lost in the mutant cell line. An additional characteristic of the cells expressing the mutant E2F1 is that they demonstrate slow growth and a doubling in S phase duration. While providing exogenous fibronectin as an adhesion substrate did not shorten the S phase duration in the mutant line, it did significantly shorten the S phase duration in the parental NIH3T3 cell line, implicating a role for the extracellular matrix in regulating S phase transit in normal cells.

3T3 Cells↗
PubMed1997

Expression of the mouse fibronectin gene and fibronectin-lacZ transgenes during somitogenesis.

Fibronectins (FNs) are essential for the proper development of embryonic mesenchymal tissues. A lacZ reporter gene has been fused to 4.9 kbp of DNA from the rat FN gene 5' flanking region, and this construct has been microinjected into fertilized mouse embryos to investigate the cis elements needed for the temporal and spatial regulation of FN in vivo. Histochemical staining of embryos for beta-galactosidase activity demonstrated that four independent lines shared a specific pattern of lacZ expression, reflecting the activity of the fibronectin sequences contained within the transgene. Specifically, somites stained positively for lacZ, but expression was spatially and temporally non-uniform, with higher levels in more caudal somites after a total of ca. 13 somite pairs had formed. This rostral-caudal gradient of lacZ expression in somites of embryos beyond this stage resembled the distribution of endogenous FN mRNA, as detected by whole mount in situ hybridization. The transgene was not expressed in the developing heart where endogenous FN mRNA was detected. Unexpectedly, highly localized staining was observed within the neural tube beginning at ca. E10-10.5, and two of the lines exhibited additional areas of staining due to the individual integration sites. Thus, the 4.9 kbp FN fragment appears to recapitulate closely the complex pattern of FN expression observed during somitogenesis. A smaller fragment of 0.9 kbp also directed lacZ expression in caudal somites at E9.5, suggesting that these sequences are sufficient to establish the spatio-temporal pattern.

Animals↗
PubMed1997

Subtotal hysterectomy in modern gynecology: a decision analysis.

OBJECTIVE: Our purpose was to compare the risks and benefits of subtotal (supracervical) hysterectomy with those of total hysterectomy in women at low risk for cervical cancer. STUDY DESIGN: A decision analysis was performed. Baseline probabilities for operative and postoperative morbidity, mortality, and long-term quality of life were established for subtotal and total hysterectomy. RESULTS: Operative complication rates and ranges for total abdominal hysterectomy were infection 3.0% (3.0% to 20.0%), hemorrhage 2.0% (2.0% to 15.4%), and adjacent organ injury 1.0% (0.7% to 2.0%). Those for subtotal hysterectomy were infection 1.4% (1.0% to 5.0%), hemorrhage 2.0% (0.7% to 4.0%), and adjacent organ injury 0.7% (0.6% to 1.0%). Operative mortality, the risk for development of cervicovaginal cancer, and long-term adverse effects on sexual or vesicourethral function were low in both groups. CONCLUSIONS: Recently proposed benefits from subtotal hysterectomy are not well proven. Total hysterectomy remains the procedure of choice for most women.

Decision Support Techniques↗
PubMed1996

Modulation of transcription of the rat fibronectin gene by cell density.

The fibronectin (FN) gene is under complex regulatory control in vitro and in vivo. Sequences from the rat FN gene directed efficient expression of a lacZ reporter gene product, beta-galactosidase, in NIH/3T3 mouse fibroblasts. Stable transfectants were generated to facilitate studies of gene regulation by cell growth state. The expression of FN-lacZ constructs increased approximately twofold when cultures attained confluence, relative to total protein. The magnitude of this increase correlates well with that observed for FN mRNA levels and protein synthesis rate. Fragments containing 4.9, 0.9, or 0.3 kbp upstream of the transcription start site are equally responsive to cell density and/or cell contact. Deletion of a cAMP-responsive element enhanced the response, suggesting a negative role for this sequence motif and demonstrating that the FN gene is regulated by cell density at the transcriptional level. The effect of high cell density is apparently different from decreased growth rate, as incubation with low serum did not result in increased expression of the lacZ reporter. Finally, conditioned medium from dense cells did not enhance reporter gene expression in sparse cells, suggesting that the density signal is not transmitted via a soluble factor.

3T3 Cells↗
PubMed1996

Characterization of mouse fibronectin alternative mRNAs reveals an unusual isoform present transiently during liver development.

Fibronectins are found in many extracellular matrices as well as being abundant plasma proteins. The plasma isoforms of fibronectin, which are synthesized in the adult by liver hepatocytes, differ from those derived from most other cells and tissues due to alternative mRNA splicing. Studies in several vertebrates have indicated that FN alternative splicing is regulated spatially and temporally during development. The mouse represents an attractive organism in which to study the regulation of fibronectin splicing during development, but the patterns of fibronectin alternative splicing were not known for this species. Mouse fibronectin cDNA clones were isolated and sequenced, revealing > 95% identity with rat fibronectin at the amino acid level; all three segments that undergo alternative splicing are well conserved. RNase protection and RT-PCR were used to determine the patterns of alternative splicing that occur in fibroblasts and adult liver, sources of cellular and plasma fibronectins. Only A-B-mRNAs were detected in liver, and three V region variants were observed, corresponding to the protein isoforms V120, V95, and V0. Fibroblasts produced mRNAs that were heterogeneous for A and B splicing, but all RNAs contained V120. These patterns contrast with the embryonic form (B+A+V120). Characterization of fibronectin mRNAs from livers of fetal and newborn mice revealed that a significant level of B+ mRNA was present throughout late gestation, declining at birth. Little A+ mRNA was present, and the adult liver V region pattern was observed at all stages. Thus, fibronectin splicing changes during liver development are noncoordinate. One consequence of this temporal regulation is the transient synthesis of B+ mRNAs, including a novel isoform, B+A-V0.

Alternative Splicing↗
PubMed1995

Genitourinary prolapse and joint hypermobility in women.

OBJECTIVE: To determine whether joint hypermobility, a clinical marker for connective tissue abnormalities, is associated with genital prolapse. METHODS: One hundred seven women were recruited from a university gynecology clinic. Subjects were examined in the standing and nonstraining positions for cystocele, rectocele, and uterine or vault prolapse. The degree of prolapse was graded 0-3. A separate investigator, blinded to the results of the gynecologic examination and using accepted criteria, evaluated each subject for joint hypermobility. RESULTS: Clinical joint hypermobility was found in 39 of 107 (36%) study patients. Subjects with joint hypermobility had a significantly higher prevalence of cystocele (33 of 37 [89%] versus 40 of 69 [58%], P = .001), rectocele (32 of 38 [84%] versus 33 of 69 [48%], P = .0002), and uterine or vault prolapse (25 of 38 [66%] versus 20 of 69 [29%], P = .0002) compared to women with normal joint mobility, respectively. No differences in the prevalence of stress incontinence were found between the two groups. CONCLUSION: Women with joint hypermobility have a significantly higher prevalence of genital prolapse compared to women with normal mobility, which suggests an underlying connective tissue abnormality as one etiology of pelvic relaxation.

Adult↗
PubMed1995

Unexpected nuclear localization of a chimeric beta-galactosidase lacZ reporter gene product in mammalian cells.

A lacZ cassette was designed to include a synthetic amino terminus optimized for translation in eukaryotic cells, as well as multiple restriction sites for the insertion of heterologous regulatory elements both 5' and 3' of the reporter. The cassette was placed under the control of the metallothionein promoter in combination with the SV40 enhancer and this plasmid was introduced into mammalian cells. High levels of beta-galactosidase were observed in several cell types, demonstrating efficient expression of the reporter. Unexpectedly, most of the chromogenic reaction product appeared to be intra- or peri-nuclear, indicating that the enzyme is similarly localized. The synthetic amino terminus does not resemble known nuclear localization signals and thus may constitute a novel signal.

Amino Acid Sequence↗
PubMed1994

Polypyrimidine tract sequences direct selection of alternative branch sites and influence protein binding.

IVS1, an intron derived from the rat fibronectin gene, is spliced inefficiently in vitro, involving the use of three alternative branch sites. Mutation of one branch point site, BP3, so as to increase complementarity to U2 snRNA resulted in exclusive use of that site and improved splicing efficiency, indicating that the wild type BP3 site is one determinant of poor IVS1 splicing. Deletions within the polypyrimidine tract had a variable effect on splicing efficiency and altered the pattern of branch site usage. Selection of each branch site was influenced negatively by purine substitutions ca. 20 nucleotides downstream. It is proposed that all three IVS1 branch sites are pyrimidine tract-dependent. Pyrimidine tract deletions also influenced the crosslinking of PTB (the polypyrimidine tract-binding protein), hnRNP C, and splicing factor U2AF65. All three proteins bound preferentially to distinct regions within the polypyrimidine tract and thus are candidates for mediating pyrimidine tract-dependent branch site selection. The findings indicate the complexity of the IVS1 polypyrimidine tract and suggest a crucial role for this region in modulating branch site selection and IVS1 splicing.

Alternative Splicing↗
PubMed1994

Evidence for a genetic influence on preference for some foods.

OBJECTIVE: The purpose of this study was to evaluate genetic influence on preference for 17 foods. The relationship between preference and use of these foods was also examined. The study focused on frequently eaten foods and on foods consumed less frequently but promoted for good health. DESIGN: Food preferences were investigated in young monozygotic and same-sex dizygotic twin pairs living at home and sharing the same environment. Subjects provided preference ratings after testing each food. A food frequency questionnaire was used to determine whether the genetic component of preference is associated with food use. SUBJECTS: Subjects were 14 pairs of monozygotic twins and 21 pairs of same-sex dizygotic twins, aged 9 to 18 years. They were recruited on a volunteer basis from public schools in Cincinnati, Ohio. MAIN OUTCOME MEASURES: We found a greater similarity in food preference between members of monozygotic twin pairs than between dizygotic twin pairs, which suggests an important role for genetics in accounting for individual differences in food preference. STATISTICAL ANALYSES PERFORMED: Food preference data were analyzed using Pearson correlation coefficients and Fischer z scores. Additional estimates of heritability were obtained by applying the Mann-Whitney nonparametric t test and the Holzinger index. Food use was correlated with preference using Pearson correlation coefficients. RESULTS: Significant differences in intrapair correlations for monozygotic and dizygotic twins were found for orange juice (z = 5.39; P < .05), broccoli (z = 2.60; P < .05), cottage cheese (z = 2.54; P < .05), chicken (z = 2.54; P < .05), sweetened cereal (z = 2.00; P < .05), and hamburger (z = 1.95; P < .10). The genetic component of preference was correlated with use for only two foods. APPLICATIONS/CONCLUSIONS: It is important for nutritionists to realize that heritable factors may influence selection of a range of foods, including some that are promoted for good health. If health-promoting foods are to be included in the diet, accessibility and exposure to these foods must be increased.

Adolescent↗