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M B Martin

Publications and source records attributed to M B Martin.

At least 55 records · Page 3Linked to original sources
PubMed1993

Loss of heterozygosity detected in formalin-fixed, paraffin-embedded tissue of colorectal carcinoma using a microsatellite located within the deleted in colorectal carcinoma gene.

We determined loss of heterozygosity from formalin-fixed, paraffin-embedded tissue of colorectal carcinoma using microsatellite polymorphism. The polymorphism was assayed based on DNA amplification by the polymerase chain reaction (PCR). The PCR-analyzed microsatellite method was applied to assay degraded DNA extracted from paraffin-embedded blocks with adenocarcinoma of colon. The DNA from 26 tumors as well as their corresponding normal tissue samples were successfully amplified using a dinucleotide microsatellite located within an intron of the deleted in colorectal carcinoma gene. Allele losses on this marker were detected in 33% of informative colorectal carcinomas. This study demonstrates that microsatellites provide a powerful set of DNA markers for loss of heterozygosity on archival specimens.

Adenocarcinoma↗
PubMed1992

A modified transfusion program for prevention of stroke in sickle cell disease.

Regular red blood cell transfusions reduce the rate of recurrent cerebral infarction in sickle cell disease but lead to accumulation of excessive iron. We studied the effect on the prevention of recurrent stroke and the volume of blood transfused of a modified transfusion program in which the pretransfusion percentage of hemoglobin S (HbS) was maintained at 50%, rather than the conventional 30%. Fifteen patients with sickle cell disease and cerebral infarction who had been free of recurrent stroke for at least 4 years during which the pretransfusion HbS was maintained below 30% were assigned to a transfusion program in which the HbS was allowed to increase to 50%. Transfusion regimens included simple transfusion and manual and automated partial exchange transfusion. The duration of follow-up was 14 to 130 months with a median duration of 84 months. None of the 15 patients had a recurrent cerebral infarction during 1,023 patient-months in which the target pretransfusion HbS was 50%. Analysis of this finding, using a binomial distribution, indicates that there is less than a 5% chance that the risk per patient of recurrent stroke in the first year of the modified transfusion program is greater than 18%. One 23-year-old patient had a fatal intraventricular hemorrhage when the HbS was 30% and a 21-year-old patient had a fatal subarachnoid hemorrhage in the 40th week of pregnancy when the HbS was 29%. Blood requirements with simple transfusions decreased by 17% to 48% (mean 31%) when the target pretransfusion HbS level was increased from 30% to 50% (P less than .001). Manual or automated partial exchange transfusions and a target HbS level of 50% in eight patients reduced blood requirements by 33% to 99% (mean 67%) in comparison with simple transfusion and a target HbS level of 30% (P less than .001). This study offers evidence that a target pretransfusion HbS level of 50% affords a continuing high rate of protection against recurrent cerebral infarction in sickle cell disease after 4 years of a conventional transfusion program. Increasing the target HbS level from 30% to 50% provides a major reduction in blood requirements and lowers the rate of iron accumulation.

Adolescent↗
PubMed1991

Post-transcriptional destabilization of estrogen receptor mRNA in MCF-7 cells by 12-O-tetradecanoylphorbol-13-acetate.

The effect of 12-O-tetradecanoylphorbol-13-acetate (TPA) on the regulation of the estrogen receptor (ER) was investigated in this study. After treatment with 100 nM TPA the concentration of receptor protein was measured using an enzyme immunoassay. By 24 h the receptor protein declined by about 80% from a level of approximately 236 fmol of ER/mg of protein in control cells to 50 fmol of ER/mg of protein in cells treated with TPA. Similar results were obtained with an estrogen receptor ligand binding assay. After removal of TPA, the level of ER returned to control values. 4-alpha-Phorbol, a compound related to TPA, had no effect on ER. The effects of TPA on ER expression appear to be mediated by activation of protein kinase C as H-7, an inhibitor of protein kinase C, blocks these effects. In addition to the effect on ER protein, TPA treatment also resulted in a decrease in the steady-state level of ER mRNA as determined by a RNase protection assay. The metabolic inhibitor cycloheximide was unable to prevent the TPA-induced decrease in ER mRNA. Transcription run-off experiments demonstrated that TPA had no effect on ER gene transcription. A half-life study demonstrated that TPA decreased ER mRNA half-life by a factor of 6 from approximately 4 h in control cells to 40 min in TPA-treated cells. These data suggest that the decline in ER expression is mediated by post-transcriptional destabilization of ER mRNA.

Cycloheximide↗
PubMed1991

Beta-thalassemia major and sickle cell disease.

Beta-thalassemia major and sickle cell disease are genetic disorders of red blood cells, caused by abnormal hemoglobin. These hemoglobinopathies affect males and females equally. Both are chronic disorders requiring lifelong treatment for affected individuals and education and support for them and their families. Special nursing considerations for the care of women facing the unique challenges of these disorders will be discussed.

Anemia, Sickle Cell↗
PubMed1989

Regulation of breast cancer cells by hormones and growth factors: effects on proliferation and basement membrane invasiveness.

The current understanding of the regulation of breast cancer cell proliferation and invasiveness by hormones and growth factors is reviewed. It has been shown that polypeptide growth factors are involved in hormone-independent breast cancer, and are sometimes oestrogen-regulated in hormone-responsive models. Basement-membrane invasiveness, relating to the metastatic potential of these cells, is also stimulated by oestrogen in hormone-dependent models, elevated in hormone-independent models, and is growth factor sensitive. Further understanding of the differential effects of growth factors on breast cancer cell proliferation and invasiveness should facilitate better therapeutic exploitation of regulation at this level.

Animals↗
PubMed1989

Role of an estrogen receptor-dependent mechanism in the regulation of estrogen receptor mRNA in MCF-7 cells.

We have previously demonstrated that regulation of estrogen receptor (ER) expression in MCF-7 breast cancer cells is a complex process involving transcriptional and posttranscriptional regulation by estradiol. Treatment of MCF-7 cells with estradiol results in the down-regulation of receptor expression; posttranscriptional suppression of receptor mRNA appears to be the predominant mechanism. To determine whether posttranscriptional regulation of ER gene expression is mediated by an ER-dependent mechanism independent of protein synthesis, we have used the competitive estrogen antagonist, 4-hydroxytamoxifen, and the inhibitor of protein synthesis, cycloheximide, to study regulation of ER mRNA by estradiol. 4-Hydroxytamoxifen had no effect on the steady-state level of receptor mRNA and effectively blocked the suppression of ER mRNA by estradiol. The metabolic inhibitor, cycloheximide, was unable to prevent the estrogen induced decrease in ER mRNA. These data provide evidence that the posttranscriptional suppression of ER expression through estradiol is mediated through the ER independent of protein synthesis. A study of the effects of estradiol on the steady-state levels of nuclear and cytoplasmic receptor mRNA suggest that posttranscriptional suppression is a nuclear event.

Breast Neoplasms↗
PubMed1988

Structure-activity analysis of a class of orally active hydroxamic acid inhibitors of leukotriene biosynthesis.

The nature of the carbonyl and nitrogen substituents of hydroxamic acids has a major influence on the biological profile of these compounds. Hydroxamates with small groups such as methyl appended to the carbonyl and relatively large nitrogen substituents generally have longer duration in vivo, produce greater plasma concentrations, and often are more potent inhibitors of in vivo leukotriene biosynthesis than hydroxamic acids with the opposite arrangement. The structure-activity relationships that describe in vitro 5-lipoxygenase inhibitory activity and in vivo leukotriene biosynthesis inhibitory potency for a group of these hydroxamic acids were investigated. While most of the compounds examined were potent in vitro inhibitors of 5-lipoxygenase, their in vivo potencies varied widely. This discrepancy was usually attributable to differences in bioavailability. Substitution patterns are described that produce potent, orally active inhibitors of leukotriene biosynthesis.

Acylation↗
PubMed1988

Regulation of the estrogen receptor in MCF-7 cells by estradiol.

The role of estradiol in the regulation of its cognate receptor in MCF-7 cells was investigated in this study. After treatment with 10(-9) M estradiol, the level of receptor protein was measured using an enzymeimmunoassay. By 6 h, the receptor protein declined by about 60% from a level of approximately 3.6 to 1.2 fmol/micrograms DNA. The level of receptor remained suppressed for 24-48 h. Similar results were obtained with an estrogen receptor (ER) binding assay. The steady state level of ER mRNA was determined by an RNase protection assay. Estrogen treatment resulted in a maximum suppression of mRNA by 6 h. Receptor mRNA remained depressed for 48 h. Transcription run on experiments demonstrated a transient decrease of about 90% in ER transcription after 1 h. By 3-6 h transcription increased approximately 2-fold and remained elevated for at least 48 h. These data suggest that estrogen down-regulates ER mRNA by inhibition of ER gene transcription at early times and by a posttranscriptional effect on receptor mRNA at later times.

Breast Neoplasms↗
PubMed1987

Differential induction of hepatic estrogen receptor and vitellogenin gene transcription in Xenopus laevis.

Low levels of estrogen receptor (200-500 per cell) are present in the liver of hormonally naive male Xenopus. However, administration of estradiol results in a rapid 2- to 5-fold increase in cellular estrogen receptor content concurrent with the de novo transcriptional activation of the genes for the yolk protein precursor vitellogenin. Studies on Xenopus embryogenesis suggest that estrogen receptor induction is required for the activation of vitellogenin transcription. The purpose of the present study was to examine the mechanism of estrogen receptor induction in male Xenopus liver. The experimental protocol used 4-hydroxytamoxifen, an antiestrogen with a high affinity for the estrogen receptor, to inhibit the effects of estradiol. Changes in estrogen receptor content were then determined through the use of an exchange assay. 4-Hydroxytamoxifen alone suppressed the level of estrogen receptor from 800 sites per cell in hormonally naive animals to 250 sites per cell. Administration of estradiol 24 h after the antiestrogen resulted in the induction of estrogen receptor to a level equivalent to that found in control animals (800 sites per cell). However, under the same conditions, estradiol was unable to overcome the antiestrogen inhibition of vitellogenin gene transcription. Although 4-hydroxytamoxifen displayed a high affinity for the hepatic estrogen receptor, it did not inhibit the binding of estradiol to a middle affinity cytoplasmic estrogen-binding protein. These results suggest that different mechanisms are involved in the induction of estrogen receptor and vitellogenin gene transcription.

Adsorption↗
PubMed1987

Posttranscriptional regulation of albumin gene expression in Xenopus liver: evidence for an estrogen receptor-dependent mechanism.

We have previously shown that estrogen administration to male Xenopus laevis results in the posttranscriptional suppression of serum albumin mRNA concurrent with the transcriptional activation of the genes for the yolk protein precursor vitellogenin. To determine whether the posttranscriptional regulation of albumin gene expression is mediated through a mechanism involving the high affinity estrogen receptor protein or through a receptor-independent mechanism involving a middle affinity cytoplasmic estrogen-binding protein we examined the effects of the competitive estrogen receptor antagonist 4-hydroxytamoxifen. Administration of 4-hydroxytamoxifen 24 h before estradiol completely blocked both the suppression of albumin mRNA and the transcriptional activation of the vitellogenin genes. Albumin gene transcription remained constitutive under all treatment regimens. Competitive binding experiments demonstrated that 4-hydroxytamoxifen has an affinity for the estrogen receptor similar to that of estradiol. However, 4-hydroxytamoxifen displays little or no interaction with the middle affinity cytoplasmic estrogen-binding protein. These data indicate that the estrogen receptor occupies a key role in the posttranscriptional regulation of albumin mRNA.

Albumins↗
PubMed1987

Colon and rectal carcinoma. Forty years and 1400 cases.

One thousand four hundred cases of colorectal carcinoma were treated primarily at the Wake Forest University Medical Center between 1945 and 1985. The surgical approach was constant in all patients without obvious stage IV disease: wide resection, including at least the primary-level and intermediate-level lymph nodes. There were 812 women and 588 men in the series. Sixty-eight per cent of the 1400 cancers occurred in the rectosigmoid, but only 53 per cent of the last 300 cases were in this region. Initial staging showed 560 cases (40%) of local disease, 504 cases (36%) of regional disease, and 336 cases (24%) of distant disease. Cecal, ascending, hepatic, and transverse lesions were most often associated with stage IV disease. Among the 1115 patients with long-term follow-up, 44 per cent with stage I disease, 37 per cent with stage II disease, 24 per cent with stage III disease, and 6 per cent with stage IV disease had survived for 5 years or longer. There were no differences when 5-year survival was correlated with site. This review provided no evidence that wide resection leads to increased long-term survival.

Adult↗
PubMed1986

Differential induction of vitellogenin gene transcription and total transcriptional activity by estrogen in Xenopus laevis liver.

The effects of estrogen on liver gene expression in Xenopus laevis were examined using a nuclear transcription "run-on" assay. Vitellogenin transcription was detected 2 h after a single dose of estradiol and reached a maximum on day 4. By 12 days after hormone treatment vitellogenin transcription declined to low levels. Within 3 h after estrogen, total transcriptional activity increased 9-fold relative to control values, reaching a maximum level of 40-fold by 12 h. Total transcription remained elevated throughout the following 12-day time course. These data indicate that changes in vitellogenin transcription and total nuclear transcription are uncoupled. Steady-state levels of vitellogenin mRNA demonstrated a close correlation with the level of vitellogenin gene transcription at all time points. In another series of experiments, animals treated repeatedly with estrogen demonstrated an elevated steady-state level of vitellogenin transcription, an elevated steady-state level of vitellogenin mRNA, and a constant elevated level of total nuclear transcriptional activity. Neither hormonal treatment regimen had an effect on the transcription of actin or induced the embryonic gene DG42. Finally, the increase in total transcriptional activity is associated with increased activities of RNA polymerase I and/or III in addition to stimulation of RNA polymerase II activity.

Animals↗
PubMed1986

Transcriptional and post-transcriptional inhibition of albumin gene expression by estrogen in Xenopus liver.

The purpose of this study was to investigate the suppression of albumin mRNA by estrogen in Xenopus liver. A single dose of estradiol rapidly suppressed albumin mRNA to 30% of the control level. Albumin mRNA remained at this new steady-state level for 9 days, after which it returned to the control level. Transcription 'run-on' experiments in isolated liver nuclei demonstrated a transient decrease of 60-90% in albumin transcription after 2-6 h and approached constitutive transcription by 12 h. Albumin gene transcription then remained constant for the following 12 days. Prolonged and enhanced suppression of albumin mRNA was observed in animals treated repeatedly with estrogen for 12 days. In these animals, albumin gene transcription was decreased 80-90% from the constitutive control level. These data indicate that albumin mRNA is suppressed by both transcriptional and post-transcriptional mechanisms.

Albumins↗
PubMed1986

Pseudocalculus sign. A pitfall of static cholangiography.

The pseudocalculus formation was first noted by Caroli in 1960, and was first called a sign by Beneventano and Schein in 1968. It is a cholangiographic illusion that appears as a filling defect in the distal common bile duct when static or "spot" films are exposed during the contractile phase of choledochal sphincter activity. Although first noted and most frequently seen in T-tube cholangiography, it is seen also during intravenous and intraoperative cholangiography. Because it mimics radiographically an impacted stone in the distal common bile duct, its delineation is critical to avoid unnecessary instrumentation of the common bile duct or even reoperation. In this review the authors discuss briefly the anatomy and physiology of the distal common bile duct and the etiology, differential diagnosis, and recognition of the pseudocalculus sign.

Ampulla of Vater↗
PubMed1985

Greater curvature gastroplasty. Follow-up at 34 months.

This retrospective study analyzes the results of 198 consecutive greater curvature gastroplasties performed in 23 male and 175 female patients with morbid obesity. The gastroplasty consisted of the creation of a 30-50 cm3 proximal gastric pouch by a double application of the TA-90 stapler, modified by removing three staples near the pin and trimming the cartridge to prevent crushing of the stomach at the outlet. The outlet was calibrated to a diameter of 1 cm and reinforced with a polypropylene seromuscular suture. No deaths occurred; postoperative complications included 32 superficial wound infections (16.2%), 24 incisional hernias (12.0%), 15 staple-line disruptions (7.6%), seven gastric outlet obstructions (3.5%), five subphrenic abscesses (2.5%), three perforations (1.5%), one splenic infarction, and one enterocutaneous fistula. One hundred sixty-one (81%) patients have been followed for a mean of 34 months (range 24 to 56 months); their mean weight loss is 36.4 per cent +/- 32.9 per cent of excess body weight. Only 45.5 per cent of these patients can be considered to have had satisfactory weight loss. Because this is not as effective as other forms of surgical therapy, the authors do not recommend greater curvature gastroplasty for the treatment of morbid obesity.

Adolescent↗
PubMed1984

Comparison of suture technique on patency of polytetrafluoroethylene-microarterial anastomoses.

Polytetrafluoroethylene (PTFE) grafts, 1 mm in internal diameter, were interpositioned in the infrarenal aortas of 20 adult Sprague-Dawley rats with either continuous or interrupted sutures. The interrupted-suture (I-S) technique was used in ten rats, the continuous-suture (C-S) technique in the other ten. After followup of 90 days, the overall patency rate for the 20 rats was 95% (19/20); all grafts in the C-S group were patent; one graft in the I-S group had occluded on the day of operation. Since excellent patency rates were obtainable with these minute PTFE grafts placed in the rat aorta by either technique, the speed with which the C-S technique can be accomplished appears to make it preferable.

Animals↗