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R Parker

Publications and source records attributed to R Parker.

At least 19 recordsLinked to original sources
PubMed1992

Analysis of chimeric mRNAs derived from the STE3 mRNA identifies multiple regions within yeast mRNAs that modulate mRNA decay.

In the yeast Saccharomyces cerevisiae unstable mRNAs decay 10-20 fold more rapidly than stable mRNAs. In order to examine the basis for the differences in decay rate of the unstable STE3 mRNA and the stable PGK1 and ACT1 mRNAs we have constructed and measured the decay rates of numerous chimeric mRNAs. These experiments indicate that multiple regions within yeast mRNAs are involved in modulating mRNA decay rates. Our results suggest that at least two regions within the STE3 mRNA are involved in stimulating rapid decay. One region is located within the coding region and requires sequences between codons 13 and 179. In addition, the STE3 3' UT can also function to stimulate decay. Surprisingly, the STE3 3' UT is not sufficient to accelerate the turnover of the stable PGK1 transcript unless portions of the PGK1 coding region are first deleted. These results not only identify sequences that function within yeast to stimulate mRNA turnover but also have important implications for an understanding of the basis of differences in eukaryotic mRNA decay rates.

Base Sequence↗
PubMed1992

Postoperative radiation therapy after radical prostatectomy for prostate carcinoma.

BACKGROUND: The role and benefit of adjuvant radiation therapy after radical prostatectomy is unclear. This role was evaluated in 58 patients who, after undergoing radical prostatectomy for prostate carcinoma, had local extension of disease beyond the prostate or positive surgical margins. Thirty-nine patients treated surgically alone were compared with 19 patients who received adjuvant postoperative radiation therapy. All patients were followed for at least 5 years, and 50 patients had 10-year follow-ups. RESULTS: At 10 years, the actuarial local failure rate was 31% for patients treated with prostatectomy alone versus 6% for the group receiving postoperative radiation therapy (P less than 0.05). The actuarial survival and metastasis-free survival were similar for both groups. When patients with involved lymph nodes were excluded from analysis, the addition of radiation therapy resulted in improved recurrence-free survival (91% versus 46% at 10 years, P = 0.04) and in a trend toward improved metastasis-free survival (91% versus 55%, P = 0.08). Complications occurred in similar frequencies in both groups. CONCLUSIONS: In patients with local disease extension or positive surgical margins after radical prostatectomy, adjuvant radiation therapy improved local control and was administered with acceptable side effects.

Adult↗
PubMed1992

Multiple biological markers in germ cell tumor patients treated with platinum-based chemotherapy.

Blood samples from 36 germ cell tumor patients receiving chemotherapy with either cisplatin or carboplatin in combination with other drugs [etoposide or vinblastine, cyclophosphamide, dactinomycin, and bleomycin (VAB-6)] were analyzed for the presence of 7 different biological markers. The biomarkers included platinum-protein adducts, platinum-DNA adducts, sister chromatid exchange (SCE), micronuclei (MN), and somatic gene mutation at the hypoxanthine phosphoribosyl transferase (HPRT) locus and the glycophorin A (GPA) loci (NO and NN). Patients were asked to donate 9 serial blood samples: a pretreatment sample followed by another drawn 12-24 h after each of four cycles of treatment and a final sample provided 3-6 months after the last cycle. Most individuals gave 7-8 samples; 7 individuals donated all 9. Because of limited amounts of cells in some cases, it was not possible to carry out all 7 assays on every sample. Pt-protein adducts, Pt-DNA adducts, and SCE showed a direct and consistent effect of treatment and were very highly correlated. A significant correlation was also seen between both Pt-protein and Pt-DNA adducts and HPRT mutation. All of the posttreatment samples were significantly elevated compared to the baseline sample. These markers also remained elevated 3-6 months after the end of treatment. By contrast, MN, HPRT mutation, and GPA mutation (both NO and NN variants) showed varying patterns of dose response, probably reflective of the differing biology of these markers scored in lymphocytes (MN and HPRT) and erythrocytes (GPA). MN were significantly elevated in the posttreatment samples drawn at cycles 2 and 3. Although induction of HPRT mutation was only of marginal significance, results here are for the mutant frequency determination assay only. In progress is the potentially more informative analysis of the type of mutations by Southern blot and the sequencing of mutations to look for characteristic mutational spectra. The GPA assay showed a significant increase over baseline in samples drawn after cycles 3 and 4 (NO variants) and after cycles 2, 3, and 4 (NN variants). The level of GPA mutation (both NO and NN variants) was clearly elevated even 3-6 months after the last cycle of chemotherapy. Correlations were seen between HPRT and MN as well as between GPA NO and GPA NN variants. Analysis of biomarkers by treatment group does not reveal a consistent pattern or trend across all cycles.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1992

A rapid method for localized mutagenesis of yeast genes.

We have developed a simple procedure for the localized mutagenesis of yeast genes. In this technique the region of interest is first amplified under mutagenic polymerase chain reaction (PCR) conditions. Cotransformation of the PCR product with a gapped plasmid containing homology to both ends of the PCR product allows in vivo recombination to repair the gap with the mutagenized DNA. This procedure is efficient, allows targeting of specific regions for mutagenesis, and requires no subcloning steps in Escherichia coli.

DNA, Fungal↗
PubMed1992

Association of cervicovaginal infections with increased vaginal fluid phospholipase A2 activity.

OBJECTIVE: The purpose of this study was to determine if phospholipase A2 was detectable within vaginal fluid and to correlate its presence with the presence of common lower genital tract infection or microbial conditions. STUDY DESIGN: Pregnant women were examined at the first prenatal visit with standard clinical evaluations and microbiologic cultures or tests. Vaginal fluid samples were evaluated for phospholipase A2 activity by means of a standardized enzyme fluorometric assay. Data were stratified to control for coexisting infections. RESULTS: Phospholipase A2 activity was detected among 29.8% of women and was independently associated with the presence of bacterial vaginosis (p < 0.001), Trichomonas. vaginalis (p < 0.04), and Chlamydia trachomatis (p < 0.02). The percentage of women with phospholipase A2 activity and the level of activity was increased in the presence of more than one infection. CONCLUSIONS: Elevated reproductive tract phospholipase A2 concentrations among pregnant women may play roles in the pathogenesis of preterm labor and birth. Identification of pregnant women with increased concentrations in vaginal fluid may allow for development of effective intervention strategies to reduce the risk of preterm birth.

Animals↗
PubMed1992

Determinants of cisplatin sensitivity in non-malignant non-drug-selected human T cell lines.

We have studied molecular mechanisms of cisplatin sensitivity and resistance in 3 non-malignant, non-drug-selected human T lymphocyte cell lines. HuT 78, H9, and MOLT-4 cells were assessed for sensitivity to cisplatin, DNA damage levels following defined drug exposures, drug accumulation, and DNA repair efficiency as measured by adduct removal from cellular DNA and by host-cell reactivation of cisplatin-modified plasmid DNA. Based on 3-day continuous drug exposures, the IC50 values for the cell lines were: HuT 78, 0.83 microM; H9, 0.45 microM; and MOLT-4, 0.33 microM. These cells retained this order with respect to DNA repair capability, whether measured by platinum-DNA adduct removal from cellular DNA or by host-cell reactivation assays. DNA repair values measured by these two assays were directly related to one another with a linear correlation coefficient of 0.993. At sublethal cisplatin doses the more resistant cells showed the highest levels of drug uptake. When drug uptake levels were 'corrected' for drug-induced cell kill, there were equal levels of DNA repair efficiency for a given level of drug uptake. Absolute levels of cisplatin-DNA adduct repair increased with increasing drug dose. However, at supralethal doses of drug, efficient DNA repair could be overcome in all 3 cell lines with percentage-adduct-removal dropping from a 60-80% range to a less than 30% range. We conclude that in non-malignant non-drug-selected human T cells, DNA repair appears to be the primary determinant of cisplatin sensitivity/resistance and that enhanced DNA repair may be a biologic compensatory mechanism for cells that cannot prevent cellular uptake of DNA-damaging agents.

Cell Line↗
PubMed1992

Clindamycin vaginal cream versus oral metronidazole in the treatment of bacterial vaginosis: a prospective double-blind clinical trial.

Bacterial vaginosis is common among patients seen by gynecologists. Several types of therapy have been proposed. The purpose of this prospective, randomized, double-blind clinical trial was to examine the efficacy of clindamycin vaginal cream for the treatment of bacterial vaginosis. Sixty patients with symptoms of bacterial vaginosis were randomized into the study, and 46 completed the protocol. Twenty-three patients received 2% clindamycin vaginal cream (5 g applied intravaginally at bedtime for 7 days), with placebo oral tablets twice daily for 7 days. The other 23 patients received oral metronidazole tablets (500 mg twice a day for 7 days) and placebo vaginal cream (5 g intravaginally for 7 days). The cure rates for the two regimens were comparable. Twenty-two (97%) of the patients treated with clindamycin vaginal cream had improvement or cure at the first follow-up visit versus 19 (83%) of those taking metronidazole. There was no statistically significant difference between the two results. Side effects for both regimens were comparable. We conclude that 2% clindamycin vaginal cream offers similar efficacy and safety to standard oral metronidazole therapy for bacterial vaginosis.

Administration, Intravaginal↗
PubMed1992

Mutations affecting stability and deadenylation of the yeast MFA2 transcript.

Decay rates of individual mRNAs in the yeast Saccharomyces cerevisiae can vary by 10- to 20-fold. To determine the basis for the rapid degradation of the mRNA encoded by the yeast MFA2 gene we have used a genetic screen to isolate mutations that increase the stability of this transcript. Analysis of point mutations obtained from this screen, and of additional lesions constructed in vitro, indicated that the MFA2 3'-untranslated region (UTR) contains sequences that specify rapid mRNA decay. Moreover, the lesions that affected mRNA decay rate also affected the process of mRNA deadenylation. Mutations in one region of the 3' UTR both decreased the rate of poly(A) shortening and increased the stability of an intermediate form in the decay pathway with an oligo(A) tail (approximately 10 nucleotides). Mutations in a second region primarily increased the stability of the oligo(A) form. These results suggest that the decay of the MFA2 mRNA initiates with the shortening of the poly(A) tail and there are specific sequences within the 3' UTR that stimulate poly(A) tail shortening as well as subsequent steps in the decay pathway. Given the similarity of this decay pathway to that seen for some mammalian mRNAs, these results suggest that mRNA deadenylation may be a common mechanism of mRNA turnover.

Base Sequence↗
PubMed1992

Antimicrobial susceptibilities of a Corynebacterium CDC group I1 strain isolated from a patient with endocarditis.

We encountered a case of native valve endocarditis due to Corynebacterium CDC group I1 which was successfully controlled with antimicrobial agents alone. This organism and three other isolates of this group were susceptible to penicillin, vancomycin, and gentamicin. The combination of penicillin with subinhibitory concentrations of gentamicin resulted in a 1,000-fold decrease in CFU per milliliter at 24 h compared with penicillin alone. Augmentation of killing was noted also with vancomycin plus gentamicin but to a degree that did not meet strict criteria for bactericidal synergism.

Corynebacterium↗
PubMed1992

Increased gene-specific repair of cisplatin interstrand cross-links in cisplatin-resistant human ovarian cancer cell lines.

We have studied several aspects of DNA damage formation and repair in human ovarian cancer cell lines which have become resistant to cisplatin through continued exposure to the anticancer drug. The resistant cell lines A2780/cp70 and 2008/c13*5.25 were compared with their respective parental cell lines, A2780 and 2008. Cells in culture were treated with cisplatin, and the two main DNA lesions formed, intrastrand adducts and interstrand cross-links, were quantitated before and after repair incubation. This quantitation was done for total genomic lesions and at the level of individual genes. In the overall genome, the initial frequency of both cisplatin lesions assayed was higher in the parental than in the derivative resistant cell lines. Nonetheless, the total genomic repair of each of these lesions was not increased in the resistant cells. These differences in initial lesion frequency between parental and resistant cell lines were not observed at the gene level. Resistant and parental cells had similar initial frequencies of intrastrand adducts and interstrand cross-links in the dihydrofolate reductase (DHFR) gene and in several other genes after cisplatin treatment of the cells. There was no increase in the repair efficiency of intrastrand adducts in the DHFR gene in resistant cell lines compared with the parental partners. However, a marked and consistent repair difference between parental and resistant cells was observed for the gene-specific repair of cisplatin interstrand cross-links. DNA interstrand cross-links were removed from three genes, the DHFR, multidrug resistance (MDR1), and delta-globin genes, much more efficiently in the resistant cell lines than in the parental cell lines. Our findings suggest that acquired cellular resistance to cisplatin may be associated with increased gene-specific DNA repair efficiency of a specific lesion, the interstrand cross-link.

Blotting, Southern↗
PubMed1992

Tuberous sclerosis with gingival overgrowth.

A case of tuberous sclerosis with gingival overgrowth is presented. A brief literature review and diagnostic criteria of tuberous sclerosis are discussed. The patient had a full-mouth gingivectomy with frequent post-operative maintenance visits. After 6 months, the overgrowth in conjunction with the tuberous sclerosis returned.

Adult↗
PubMed1992

Single dose oral fluconazole vs intravaginal terconazole in treatment of Candida vaginitis. Comparison and pilot study.

Candida vaginitis develops in approximately one-fourth of women in their childbearing years. Conventional management consists of antifungal creams or tablets/suppositories administered intravaginally. Many patients have stated preferences for oral therapy. A randomized, double-blind placebo trial compared the efficacy of a single oral 200 mg dose of fluconazole with the application of terconazole 80 mg vaginal suppository daily for 3 days. Twenty-two patients (fluconazole = 12, terconazole = 10) were evaluated during a four-month period and favorable clinical responses were observed at both early and late evaluations. Mycologic cure was attained by 75% of the fluconazole group and 50% of the terconazole group at the early evaluation. At the late evaluation, mycologic cure was 75% and 100% respectively. The mean time to onset of symptom relief was 2.4 (1.7) days for the fluconazole group and 1.8 (1.8) days for the terconazole group. The mean time to complete relief of symptoms was 6.08 (2.84) and 6.6 (2.95) days respectively. A statistically significant difference did not exist for any of these measures. Seventy-three percent of the patients preferred oral therapy.

Administration, Intravaginal↗
PubMed1991

Absence of mutagenic effects of continuous and pulsed ultrasound in cultured (AL) human-hamster hybrid cells.

Mutagenic effects of continuous and pulsed ultrasound were looked for using an in vitro assay system, the AL hybrid, that is up to 100 times more sensitive for mutagens such as x-rays and neutrons than the assays used previously to evaluate ultrasound. Cells in suspension in rotated plastic test tubes were insonated with continuous wave ultrasound at 1 MHz, ISPTP = 0.62-40 W/cm2 for 0-40 min. Cells attached in the central region of culture flasks received pulsed exposures at fc = 2.5 MHz, PRF = 1 kHz, 2 and 8 cycles per pulse, with p- = 1.2 MPa (ISPTA = 31-180 mW/cm2) for 0-30 min. Although these exposures were cytotoxic (the plating efficiency was decreased to approximately 65% by the highest doses), induction of mutation, if any occurred, was less than would be expected in this test system from 10-30 cGy of x-ray.

Animals↗
PubMed1991

Ability, achievement, and adjustment in homeless children.

Homeless 3-12-year-old children residing in city shelters were compared with a matched control group of 45 inner city children in terms of cognitive functioning and emotional-behavioral adjustment. School-age children in both groups did not differ significantly on most measures. Preschool homeless children exhibited slower development and more emotional-behavioral problems than did their domiciled peers, and significantly fewer were enrolled in early childhood programs. The feasibility of evaluating this population on standardized instruments is demonstrated, and implications of the study for social policy are discussed.

Achievement↗
PubMed1991

Functional evaluation following microvascular oromandibular reconstruction of the oral cancer patient: a comparative study of reconstructed and nonreconstructed patients.

Over the past decade, the use of free flap transfers in head and neck surgery has led to remarkable advances in the reliability and the ultimate results of oromandibular reconstruction. Stable and retentive dental restorations have been achieved using enosseous implants placed directly into the vascularized bone flaps. However, the functional assessment of patients who underwent primary mandibular reconstruction with these techniques has not been previously reported. A group of 10 reconstructed and 10 nonreconstructed segmental hemimandibulectomy patients were compared using a battery of tests to assess their overall well-being, cosmesis, deglutition, oral competence, speech, length of hospitalization, and dental rehabilitation. In addition, objective measures of the masticatory apparatus (interincisal opening, bite force, chewing performance, and chewing stroke) were used to compare these two groups as well as normal healthy subjects and edentulous patients restored with conventional and implant-borne dentures. The results show a clear advantage for the reconstructed patients in almost all categories. Persistent problems and future directions in oromandibular reconstruction are discussed.

Adult↗
PubMed1991

Immunologic effects of plasmapheresis synchronized with pulse cyclophosphamide in systemic lupus erythematosus.

Extensive immunologic evaluation was made of a patient with severe systemic lupus erythematosus (SLE) undergoing 6 cycles of plasmapheresis combined with pulsed cyclophosphamide therapy. Clinical remission ensued accompanied by normalization of levels of circulating autoantibodies, immune complexes, complement proteins, interleukin 2 (IL-2) and IL-2 receptor. High spontaneous peripheral blood lymphocyte proliferation fluctuated widely with plasmapheresis, but was consistently reduced after cyclophosphamide. Circulating B cells fell by 85% and remained low at one year, despite recovery of the serum IgG level. Circulating T cells declined by 48%, chiefly in the immunologically naive CD4+CD45R+ T cell subset. This was associated with the emergence of a CD8+DR+CDw29+ T cell subset signifying immunologically mature, activated cytotoxic/suppressive T cells, which might have served to control the autoreactive B and T cell populations. Pulsed cyclophosphamide synchronized with plasmapheresis profoundly affected the immune system of our patient. The association of these immunological changes with clinical recovery warrants further investigation of this new therapeutic approach in SLE.

Adult↗