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M C Hall

Publications and source records attributed to M C Hall.

At least 37 records · Page 2Linked to original sources
PubMed1999

In vivo and in vitro expression of steroid-converting enzymes in human breast tumours: associations with interleukin-6.

Enzymes modulating local steroid availability play an important role in the progression of human breast cancer. These include isoforms of 17beta-hydroxysteroid dehydrogenase (17-HSD), aromatase and steroid sulphatase (STS). The aim of this study was to investigate the expression, by reverse transcription polymerase chain reaction, of 17-HSD types I-IV, aromatase and steroid STS in a series of 51 human breast tumour biopsies and 22 primary cultures of epithelial and stromal cells derived from these tumours, giving a profile of the steroid-regulating network for individual tumours. Correlations between enzyme expression profiles and expression of the interleukin (IL)-6 gene were also sought. All except one tumour expressed at least one isoform of 17-HSD, either alone or in combination with aromatase and STS. Expression of 17-HSD isoforms I-IV were observed in nine tumours. Of the 15 tumours which expressed three isoforms, a combination of 17-HSD II, III and IV was most common (6/15 samples). The majority of tumours (n = 17) expressed two isoforms of 17-HSD with combinations of 17-HSD II and IV predominant (7/17 samples). Eight tumours expressed a single isoform and of these, 17-HSD I was in the majority (5/8 samples). In primary epithelial cultures, enzyme expression was ranked: HSD I (86%) > STS (77%) > HSD II (59%) > HSD IV (50%) = aromatase (50%) > HSD III (32%). Incidence of enzyme expression was generally reduced in stromal cultures which were ranked: HSD I (68%) > STS (67%) > aromatase (48%) > HSD II (43%) > HSD IV (28%) > HSD III (19%). Expression of IL-6 was associated with tumours that expressed > or = 3 steroid-converting enzymes. These tumours were of higher grade and tended to come from patients with family history of breast cancer. In conclusion, we propose that these enzymes work in tandem with cytokines thereby providing sufficient quantities of bioactive oestrogen from less active precursors which stimulates tumour growth.

17-Hydroxysteroid Dehydrogenases↗
PubMed1999

Helicase motifs: the engine that powers DNA unwinding.

Helicases play essential roles in nearly all DNA metabolic transactions and have been implicated in a variety of human genetic disorders. A hallmark of these enzymes is the existence of a set of highly conserved amino acid sequences termed the 'helicase motifs' that were hypothesized to be critical for helicase function. These motifs are shared by another group of enzymes involved in chromatin remodelling. Numerous structure-function studies, targeting highly conserved residues within the helicase motifs, have been instrumental in uncovering the functional significance of these regions. Recently, the results of these mutational studies were augmented by the solution of the three-dimensional crystal structure of three different helicases. The structural model for each helicase revealed that the conserved motifs are clustered together, forming a nucleotide-binding pocket and a portion of the nucleic acid binding site. This result is gratifying, as it is consistent with structure-function studies suggesting that all the conserved motifs are involved in the nucleotide hydrolysis reaction. Here, we review helicase structure-function studies in the light of the recent crystal structure reports. The current data support a model for helicase action in which the conserved motifs define an engine that powers the unwinding of duplex nucleic acids, using energy derived from nucleotide hydrolysis and conformational changes that allow the transduction of energy between the nucleotide and nucleic acid binding sites. In addition, this ATP-hydrolysing engine is apparently also associated with proteins involved in chromatin remodelling and provides the energy required to alter protein-DNA structure, rather than duplex DNA or RNA structure.

Adenosine Triphosphate↗
PubMed1998

Site-directed mutations in motif VI of Escherichia coli DNA helicase II result in multiple biochemical defects: evidence for the involvement of motif VI in the coupling of ATPase and DNA binding activities via conformational changes.

Two site-directed mutants of Escherichia coli DNA helicase II (UvrD) were constructed to examine the functional significance of motif VI in a superfamily I helicase. Threonine 604 and arginine 605, representing two of the most highly conserved residues in motif VI, were replaced with alanine, generating the mutant alleles uvrD-T604A and uvrD-R605A. Genetic complementation studies indicated that UvrD-T604A, but not UvrD-R605A, functioned in methyl-directed mismatch repair and UvrABC-mediated nucleotide excision repair. Both mutant enzymes were purified and single-stranded DNA (ssDNA)-stimulated ATP hydrolysis, duplex DNA unwinding, and ssDNA binding were studied in the steady-state and compared to wild-type UvrD. UvrD-T604A exhibited a serious defect in ssDNA binding in the absence of nucleotide. However, in the presence of a non-hydrolyzable ATP analog, DNA binding was only slightly compromised. Limited proteolysis experiments suggested that UvrD-T604A had a "looser" conformation and could not undergo conformational changes normally associated with ATP binding/hydrolysis and DNA binding. UvrD-R605A, on the other hand, exhibited nearly normal DNA binding but had a severe defect in ATP hydrolysis (kcat=0.063 s-1 compared to 162 s-1 for UvrD). UvrD-T604A exhibited a much less severe decrease in ATPase activity (kcat=8.8 s-1). The Km for ATP for both mutants was not significantly changed. The results suggest that residues within motif VI of helicase II are essential for multiple biochemical properties associated with the enzyme and that motif VI is potentially involved in conformational changes related to the coupling of ATPase and DNA binding activities.

Adenosine Triphosphatases↗
PubMed1998

Evidence for a physical interaction between the Escherichia coli methyl-directed mismatch repair proteins MutL and UvrD.

UvrD (DNA helicase II) is an essential component of two major DNA repair pathways in Escherichia coli: methyl-directed mismatch repair and UvrABC-mediated nucleotide excision repair. In addition, it has an undefined role in the RecF recombination pathway and possibly in replication. In an effort to better understand the role of UvrD in these various aspects of DNA metabolism, a yeast two-hybrid screen was used to search for interacting protein partners. Screening of an E.coli genomic library revealed a potential interaction between UvrD and MutL, a component of the methyl-directed mismatch repair pathway. The interaction was confirmed by affinity chromatography using purified proteins. Deletion analysis demonstrated that the C-terminal 218 amino acids (residues 398-615) of MutL were sufficient to produce the two-hybrid interaction with UvrD. On the other hand, both the N- and C-termini of UvrD were required for interaction with MutL. The implications of this interaction for the mismatch repair mechanism are discussed.

Adenosine Triphosphatases↗
PubMed1998

Advanced transitional cell carcinoma of the upper urinary tract: patterns of failure, survival and impact of postoperative adjuvant radiotherapy.

PURPOSE: We review the outcome of patients with advanced stage III or IV transitional cell carcinoma of the upper urinary tract and the impact of postoperative radiotherapy. MATERIALS AND METHODS: We identified 74 patients who were treated surgically with curative intent for stage III (49) or IV (25) transitional cell carcinoma of the upper urinary tract. Median followup was 21 months (range 1 to 236) for all patients and 60 months (range 29 to 172) for those alive at last contact. A median dose of 40 Gy. adjuvant radiotherapy was delivered to the tumor bed and regional nodes of 15 patients (30%) with stage III and 13 (52%) with stage IV disease. RESULTS: The actuarial 5-year overall and disease specific survival for patients with stage III disease was 28 and 40%, respectively. Median disease specific survival was 37 months. Median overall and disease specific survival for patients with stage IV disease was 7 months. Isolated local recurrence was identified in 5 of 49 patients with stage III and only 1 of 25 with stage IV disease. The 5-year actuarial disease specific survival rate in patients with stage III disease whether or not they were treated with postoperative radiotherapy was 45 versus 40%, respectively. For patients with stage IV disease median survival was 7 and 9 months for those who were and those who were not treated with postoperative radiotherapy, respectively. CONCLUSIONS: Patients with stages III and IV transitional cell carcinoma of the upper urinary tract have a high risk of disease relapse and cancer mortality. The major clinical feature is distant failure with isolated local relapse uncommon following initial aggressive surgical therapy. There is no survival benefit with postoperative adjuvant radiotherapy. More effective systemic adjuvant therapy is necessary to improve the outcome of these patients.

Adult↗
PubMed1998

Deoxyribonucleic acid flow cytometry and traditional pathologic variables in invasive penile carcinoma: assessment of prognostic significance.

OBJECTIVES: The identification of reliable prognostic factors to guide the selection of patients at high risk of harboring subclinical metastases in penile cancer is important. We evaluated traditional pathologic variables and deoxyribonucleic acid (DNA) flow cytometry to determine the prognostic significance of these variables for the subsequent development of lymph node metastases. METHODS: Clinical data and pathologic specimens were retrospectively reviewed from patients treated surgically at university-affiliated hospitals from 1958 to 1987. Pathologic analysis (grade, depth of invasion, and pathologic stage) and DNA flow cytometry were performed on specimens from 46 patients with invasive penile carcinoma and complete medical records. Pathologic variables were compared with DNA flow cytometry results in patients who never developed lymph node metastasis (32 patients, median follow-up 121 months) and in those who presented with or developed proved lymph node metastases (14 patients, median follow-up 18 months). RESULTS: The distributions of diploid and nondiploid tumors were similar in patients with or without lymph node metastasis. In addition, there was no significant difference in the grade distributions of tumors with respect to lymph node status. Patients with positive nodes more commonly had tumors that invaded greater than 0.5 cm or that exhibited pathologic Stage T2 or greater (deep invasion). All 14 patients who presented with or subsequently developed metastasis had deep primary tumors. Thirteen of 36 patients with clinically negative nodes had superficially invasive tumors (pathologic Stage T1 and depth of invasion 0.5 cm or less), and none developed metastasis (median follow-up 124 months [range 58 to 240]). Tumor grade was significantly related to the likelihood of deep invasion but was not an independent prognostic factor for metastasis. CONCLUSIONS: DNA flow cytometry does not add prognostic information to that obtained by pathologic assessment in patients with invasive penile carcinoma. The presence of pathologic Stage T2 or greater or depth of invasion greater than 0.5 cm defines a group of patients at high risk of inguinal node metastasis. A novel finding was that patients with minimally invasive lesions (0.5 cm or less) and no evidence of corporal invasion (pathologic Stage T1) have little risk of inguinal node metastasis. Close observation of reliable patients meeting these criteria may be a safe alternative to prophylactic lymphadenectomy.

DNA, Neoplasm↗
PubMed1998

Prognostic factors, recurrence, and survival in transitional cell carcinoma of the upper urinary tract: a 30-year experience in 252 patients.

OBJECTIVES: To review a large single-center experience of patients treated for upper tract transitional cell carcinoma (TCC) with extended follow-up in order to identify patterns of recurrence, assess patient outcomes, and determine the impact of traditional prognostic factors. METHODS: We reviewed 252 patients treated surgically for upper tract TCC with a median follow-up of 64 months. Most patients (77%) underwent nephroureterectomy, whereas 17% were treated with a parenchymal sparing approach. Traditional prognostic factors including age, sex, tumor stage, grade, location, and type of surgical treatment were analyzed with respect to disease recurrence and survival. RESULTS: Disease relapse occurred in 67 patients (27%) at a median time of 12.0 months. Recurrences were local in the retroperitoneum (9%), the bladder (51%), remaining upper tract (18%), or distant in the lung, bone, or liver (22%). The 6 patients with local relapse were among the 73 patients with pT3 or pT4 tumors, and all died of TCC at a median time from diagnosis of 37 months. Significant prognostic factors for recurrence by univariate analysis were tumor grade (P = 0.0014) and stage (P = 0.0001). On multivariate analysis, only tumor stage (P = 0.017) and treatment modality (P = 0.020) were predictors of recurrence. Actuarial 5-year disease-specific survival rates by primary tumor stage were 100% for Ta/cis, 91.7% for T1, 72.6% for T2, and 40.5% for T3. Patients with primary Stage T4 tumors had a median survival of 6 months. Although tumor stage and grade correlated with disease-specific survival on univariate analysis, only patient age (P = 0.042) and stage (P = 0.0001) were significant on multivariate analysis with the type of surgical procedure performed approaching significance (P = 0.0504). CONCLUSIONS: Primary tumor stage and surgical procedure performed (radical versus parenchymal sparing) are important predictors of disease recurrence. Patient age and tumor stage were the only predictors of disease-specific survival on multivariate analysis with the type of surgical procedure approaching significance. Radical nephroureterectomy achieves excellent local control even in the setting of locally advanced (pT3 or T4) disease. The major clinical feature in this setting is distant failure, and the development of effective systemic therapy is needed to improve the outcome in these patients.

Adult↗
PubMed1998

Occult B cell malignancies can be detected by three-color flow cytometry in patients with cytopenias.

Patients with unexplained cytopenias often present a diagnostic dilemma with minimal morphologic or cytogenetic changes to identify the underlying disease process. We have used multidimensional flow cytometry in a study of patients with cytopenias and found that this technology established, changed, or refined the diagnosis in 17/121 patients. Using the flow cytometric technique of CD45 and right angle light scatter (SSC) gating with two additional markers in a three-color analysis, eight of 121 patients were found to have hairy cell leukemia (HCL), in the absence of definitive morphologic findings of HCL. Two additional patients were found to have non-Hodgkin's lymphoma (NHL). Myeloid abnormalities, myelodysplasia (MDS) or acute leukemia was detected in seven of 56 patients with unexplained pancytopenia. Six of 65 patients identified with cytopenias resulting from lymphoid neoplasms had been referred for bone marrow transplantation (BMT) with a presumptive diagnosis of MDS, with subsequent deferral of BMT upon correct diagnosis. The screening technique is incorporated into an extensive immunophenotyping scheme to identify hematopoietic abnormalities using multidimensional flow cytometry (MDF). HCL cells (detected as low as 1.3%) reside in the same position as normal monocytes in the CD45 and SSC plots but could be distinguished from monocytes based on the expression of HLA-DR without CD11b, and expression of CD19. Further phenotyping of the abnormal population confirmed immunoglobulin light chain restriction, CD11c, and CD25 expression. Non-Hodgkin's lymphoma was detected as aberrant mature lymphocytes expressing B lymphoid markers, CD5 and light chain restriction. Myeloid abnormalities were identified in the myeloblast or maturing myeloid cell fractions. The flow cytometric scheme described can be used in primary diagnosis. The technique is definitive, sensitive, and stresses the importance of distinguishing lymphoid from myeloid etiology of cytopenias.

Acute Disease↗
PubMed1998

Reproducibility of three different methods of measuring baroreflex sensitivity in normal subjects.

1. Baroreflex sensitivity is a useful tool for investigating cardiovascular reflexes in a number of clinical settings. Several different methods of measuring baroreflex sensitivity are available. In order to determine a clinically useful non-invasive method of measuring baroreflex sensitivity we compared two methods (spectral analysis and the Valsalva manoeuvre) with regard to reproducibility, agreement with a standard invasive method (phenylephrine infusion) and failure rate.2.Twenty-six healthy subjects aged 22 to 63 years attended on three separate occasions for measurement of baroreflex sensitivity using the different methods. The effect of a recent head-up tilt on baroreflex sensitivity was measured.3. Reproducibility was best for the low-frequency component of the spectral method [coefficient of variation 25.0% (range 3.5-42.4%)] and worst for the Valsalva method [coefficient of variation 29.3% (range 13.8-93.1%)]. Both non-invasive methods overestimated values compared with the phenylephrine method [bias of low-frequency component of the spectral method, 1.17 (0.38-3.6); bias of the Valsalva method, 1.13 (0.19-6.7)]. The high-frequency component of the spectral method did not agree with the phenylephrine method.4. The spectral analysis method had the fewest failures (seven subjects with a failure on at least one occasion), and the phenylephrine method the most (16 subjects with a failure on at least one occasion). A short head-up tilt did not affect the subsequent non-invasive measurement of baroreflex sensitivity.5. It was concluded that the low-frequency component of the spectral method was the most clinically useful non-invasive measurement of baroreflex sensitivity.

Adult↗
PubMed1998

The hematological responses of rats exposed to conditions of simulated microgravity and acute exercise.

BACKGROUND: Although humans have experienced microgravity since 1961, it is unknown whether PaO2 or PaCO2 will change in humans or in animals exposed to similar conditions. Reports from subjects participating in long-term head down tilt studies indicate that PAO2 will decrease and PaCO2 will increase, presumably because of impairments in oxygen delivery and carbon dioxide transport. To investigate this topic with suspended (HDS) rats, we hypothesized that 14 d of HDS would lower resting PaO2 and elevate PaCO2 pressures when compared with control rats. Since returning astronauts, previously bed rested subjects, and suspended rats had exhibited decreases in maximum aerobic capacity, we predicted after 2 weeks of HDS, rats performing maximum exercise would demonstrate significant decreases in PaO2 and elevations in hydrogen ions. RESULTS: Blood gas results during HDS indicated PaO2 and PaCO2 partial pressures were significantly decreased during the first week of suspension. Maximal exercise significantly increased PaO2 pressures in both animal groups, but during exercise the suspended rats exhibited significant increases in lactic acid and hydrogen ion concentrations when compared with control animals. CONCLUSIONS: The suspended rat model effectively characterized PaO2 changes that have been reported for humans exposed to conditions of simulated microgravity. However, the decreases in VO2max reported for exercising humans and animals could not be explained by PaO2 changes and the rat model was not effective in predicting changes in blood PaCO2. RECOMMENDATIONS: NASA should encourage and support studies that characterize PaO2 and PaCO2 change in humans and animals, in space and after they return to a 1-G environment.

Animals↗
PubMed1997

Mutation of a highly conserved arginine in motif IV of Escherichia coli DNA helicase II results in an ATP-binding defect.

A site-directed mutation in motif IV of Escherichia coli DNA helicase II (UvrD) was generated to examine the functional significance of this region. The highly conserved arginine at position 284 was replaced with alanine to construct UvrD-R284A. The ability of the mutant allele to function in methyl-directed mismatch repair and UvrABC-mediated nucleotide excision repair was examined by genetic complementation assays. The R284A substitution abolished function in both DNA repair pathways. To identify the biochemical defects responsible for the loss of biological function, UvrD-R284A was purified to apparent homogeneity, and its biochemical properties were compared with wild-type UvrD. UvrD-R284A failed to unwind a 92-base pair duplex region and was severely compromised in unwinding a 20-base pair duplex region. The Km of UvrD-R284A for ATP was significantly greater than 3 mM compared with 80 microM for UvrD. A large decrease in ATP binding was confirmed using a nitrocellulose filter binding assay. These data suggested that the R284A mutation severely reduced the affinity of helicase II for ATP. The reduced unwinding activity and loss of biological function of UvrD-R284A was probably the result of decreased affinity for ATP. These results implicate motif IV of superfamily I helicases in nucleotide binding and represent the first characterization of a helicase mutation outside motifs I and II that severely impacted the Km for ATP.

Adenosine Triphosphatases↗
PubMed1996

Complications of radical cystectomy: impact of the timing of perioperative chemotherapy.

OBJECTIVES: To evaluate the impact of timing of perioperative chemotherapy on morbidity of radical cystectomy in patients with bladder cancer. METHODS: We compared the complications in patients randomized to neoadjuvant (n = 53) or adjuvant (n = 49) MVAC (methotrexate, vinblastine, doxorubicin, and cisplatin) chemotherapy. RESULTS: In the 95 patients who underwent cystectomy, there were no significant differences in treatment compliance, surgical parameters, or postoperative recovery between the two groups. In patients who received neoadjuvant chemotherapy, there were more complications, and there was one perioperative death; however, these differences were not significant. The neoadjuvant group took longer to complete therapy (P < 0.001). Nine patients (3 neoadjuvant, 6 adjuvant) did not undergo cystectomy on time. CONCLUSIONS: Cystectomy following neoadjuvant MVAC chemotherapy is feasible. We were unable to demonstrate any difference between neoadjuvant and adjuvant chemotherapy in mortality, morbidity, or postoperative clinical course.

Adult↗
PubMed1996

A comparison of sealer placement techniques in curved canals.

Sealer placement techniques have not been examined in teeth with curved canals prepared with Lightspeed instruments. Three traditional methods of placing sealer were studied, using 45 extracted human single-rooted teeth, divided into 3 groups of 15. Root canal preparations were made with Light-speed nickel-titanium, engine-driven instruments. AH26 sealer was applied with either K-file, lentulo spiral, or master gutta-percha cone. Radiographs were taken after sealer placement and analyzed for amount of canal sealer fill. The teeth were then obturated with laterally condensed gutta-percha, chemically cleared, photographed, and analyzed for total canal wall sealer coverage. The results showed a statistically significant difference in canal sealer fill among the three groups before obturation, but there was no statistical difference in canal wall coverage among the three groups after obturation. None of the examined methods exceeded an average of 62.5% wall coverage of sealer after obturation. This suggests that complete wall coverage after obturation may not be possible.

Analysis of Variance↗
PubMed1996

Is screening for prostate cancer necessary in men with symptoms of benign prostatic hyperplasia?

In this report, we review the critical issues concerning the early detection of prostate cancer in patients presenting with symptoms of benign prostatic hyperplasia (BPH). Only with the recent introduction of serum prostate-specific antigen (PSA) testing and transrectal ultrasonography (TRUS)-guided biopsy has the question arisen to what extent the treating physician has a responsibility to rule out prostate cancer before recommending treatment-or watchful waiting-for men with clinical BPH. Uneasiness and uncertainty also result from the development of alternative therapies that do not provide tissue for pathological analysis, or alter serum PSA levels in a poorly predictable fashion. Current early detection strategies, in this clinical situation, pose unique problems, largely because of the great degree of overlap in serum PSA among men with localized prostate cancer and BPH. The underlying goal is to distinguish patients with BPH alone from those with clinically significant, but organ-confined and potentially curable prostate cancer. Treatment for prostate cancer may take precedence over BPH management strategies, while at the same time address the symptoms associated with coexistent clinical BPH. The issues discussed in this report should aid the clinician in the evaluation of patients with clinical BPH. Further studies are clearly needed that may ultimately enhance our ability to discriminate patients with clinically significant organ-confined prostate tumors from those with BPH alone.

Adult↗
PubMed1995

Femoral neuropathy complicating urologic abdominopelvic procedures.

We report on 3 cases of femoral neuropathy following radical surgery for urologic malignancy. The defect was bilateral in 2 patients. Compression from self-retaining retractors was the presumed mechanism of injury in all patients. Spontaneous improvement was observed in each case although the symptoms did not resolve completely. The pathophysiology contributing to this operative complication as well as measures for prevention and treatment are discussed.

Adult↗