Biomedical subjects

C M Johnston

Publications and source records attributed to C M Johnston.

At least 19 recordsLinked to original sources

PubMed1999

Endoscopic spray cryotherapy: a new technique for mucosal ablation in the esophagus.

BACKGROUND: A simple and safe method for controlled ablation of esophageal mucosa is not currently available. Therefore, an endoscopic cryotherapy device was developed and its efficacy and safety were assessed in a swine model. METHODS: The device consists of a cryogenic system that delivers cold nitrogen gas via a catheter introduced into the esophagus through the accessory channel of an upper GI endoscope. Esophagoscopy was performed in 20 swine under conscious sedation, and cold nitrogen gas was sprayed on the distal 2 to 3 cm of the esophagus under direct visualization. RESULTS: Freezing of the esophageal mucosa was evidenced by the appearance of a white "cryoburn" with sharply demarcated margins. Hemicircumferential to circumferential freezing of the distal esophagus was achieved in 20 swine by varying the duration of cryoburn from 10 to 60 seconds. Mucosal ablation was noted 2 to 7 days after treatment in 95% of the swine. Complications included 3 esophageal strictures and 1 aspiration pneumonia. CONCLUSIONS: Cryotherapy performed by spraying liquid nitrogen at upper GI endoscopy is a simple technique capable of inducing controlled superficial mucosal necrosis with complete healing in the esophagus. This method warrants further evaluation as a treatment for esophageal lesions including Barrett's esophagus.

Animals↗

PubMed1999

Comparison of mutations of Ki-RAS and p53 immunoreactivity in borderline and malignant epithelial ovarian tumors.

Ovarian tumors of low malignant potential ("borderline tumors") have been proposed variably to represent a distinctive type of malignancy, precursors of frank ovarian malignancy, or a nonmalignant process. We analyzed 81 malignant and 39 borderline ovarian tumors for p53 immunoreactivity and alterations in codon 12 of Ki-RAS in order to correlate these alterations with tumor and cell type. Diffuse p53 immunoreactivity was significantly more prevalent among malignant (36 of 81, 44%) than among borderline (3 of 39, 8%) tumors and was particularly prevalent among serous invasive carcinomas (16 of 26, 62%). Conversely, mutations in codon 12 of Ki-RAS were significantly more prevalent in borderline (16 of 39, 41%) than in malignant (9 of 81, 11%) ovarian tumors and were most prevalent among mucinous tumors. This preliminary molecular analysis suggests that serous borderline tumors have some molecular features usually associated with malignancy but are unlikely to represent a precursor of invasive serous carcinoma. In contrast, mucinous borderline tumors may represent a precursor or variant of mucinous carcinoma of the ovary.

Adenocarcinoma, Mucinous↗

PubMed1999

Bromodeoxyuridine alternating with radiation for advanced uterine cervix cancer: a phase I and drug incorporation study.

PURPOSE: Preclinical studies show a significant increase in the ratio of the radiosensitizer bromodeoxyuridine (BUdR) in tumors versus the intestinal mucosa during the drug elimination period, compared with the ratio during drug infusion. We constructed a phase I study in patients with locally advanced cervix cancer, using alternating cycles of BUdR and radiation therapy (RT). PATIENTS AND METHODS: Eighteen patients with stage IIB to IVA cervix cancer participated. A treatment cycle consisted of a 4-day BUdR infusion followed by a week of pelvic RT, 15 Gy twice daily in 1.5-Gy fractions. After three cycles, additional BUdR was infused, followed by brachytherapy. The fraction of thymidine replaced by BUdR and the fraction of cells incorporating BUdR were determined in rectal mucosa and tumor biopsies at the end of the first BUdR infusion (day 5), at the middle of the first RT week (day 10), and at the time of brachytherapy. RESULTS: Dose-limiting toxicity was observed in one of 16 patients receiving 1,000 mg/m2/d x 4 days and in both patients receiving 1,333 mg/m2/d x 4 days each cycle. After a median follow-up of 39 months, 12 patients (66%) were free of pelvic disease and nine (50%) were alive and disease free. The ratio of tumor to rectum BUdR incorporation averaged 1.5 to 1.8 and did not differ significantly between day 5 and day 10. A trend toward reduced ratio was observed at brachytherapy. Drug-containing cells in rectal biopsies migrated from the crypts to the mucosal surface. CONCLUSION: In this schedule, 1,000 mg/m2/d is the maximum-tolerated dose of BUdR. BUdR incorporation levels in tumors were consistent with clinically significant radiosensitization. The migration of BUdR-containing rectal mucosa cells from the crypts to the surface at the time of RT suggests that this regimen may offer a relative sparing of the mucosa from radiosensitization.

Adenocarcinoma↗

PubMed1998

Developmentally regulated Xist promoter switch mediates initiation of X inactivation.

Developmental regulation of the mouse Xist gene at the onset of X chromosome inactivation is mediated by RNA stabilization. Here, we show that alternate promoter usage gives rise to distinct stable and unstable RNA isoforms. Unstable Xist transcript initiates at a novel upstream promoter, whereas stable Xist RNA is transcribed from the previously identified promoter and from a novel downstream promoter. Analysis of cells undergoing X inactivation indicates that a developmentally regulated promoter switch mediates stabilization and accumulation of Xist RNA on the inactive X chromosome.

Animals↗

PubMed1998

Customized gynecologic interstitial implants: CT-based planning, dose evaluation, and optimization aided by laparotomy.

PURPOSE: Interstitial perineal implants may be utilized to deliver a high local radiation dose in the treatment of advanced gynecologic malignancies. Lack of knowledge of the precise anatomic relationships between the implant and the target and critical organs may limit efficacy and increase complication risks. Computed tomography (CT)-based planning, dose evaluation, and optimization of customized interstitial implants, aided by laparotomy, have been developed to overcome these limitations. METHODS AND MATERIALS: Twenty patients with locally advanced gynecologic malignancies treated between May 1990 to October 1996 with external irradiation and one or two implants. Interstitial implants were performed when intracavitary brachytherapy was judged to be inadequate or when the response to external radiation and an intracavitary implant was not satisfactory. Customized interstitial implants were planned using preimplantation CT to determine catheter angles and paths that best implanted the target while avoiding pelvic bones and organs. Laparotomy aimed at lysing bowel adhesions, placement of omental carpet, and refining needle placement. Postimplantation CT was used for loading optimization and dose evaluation. RESULTS: Catheter angles 15-25 degrees were found to adequately implant anteriorly laying targets while avoiding pubic bones and bladder. Adhesiolysis of bowel loops from the vaginal apex was required in patients with prior hysterectomy. Small modifications in catheter placements were made during laparotomy in all implants. Postimplantation CTs showed deviations of the catheter positions compared with the planning CTs and were essential in determining target and organ doses and loading optimization. At a median follow-up of 42 months (range: 9-80 months), local control rate is 55% and disease-free survival 40%. Late complications occurred in 2 of 11 of patients without local recurrence. CONCLUSIONS: CT-based planning, loading optimization, and dose evaluation of customized implants improve radiation dose delivery. Laparotomy enhances implant accuracy and safety. Local tumor control rate is still unsatisfactory. It reflects the shortcomings of technical advances alone in poor prognosis tumors like those selected for this series.

Adenocarcinoma↗

PubMed1998

Molecular evolution of the ZFY and ZNF6 gene families.

Members of the ZFY and ZNF6 gene families have been cloned from species representing different taxa and different modes of sex determination. Comparisons of these genes show the ZFY-like and ZNF6 sequences to be strongly conserved across marsupials, birds, and lepidosaurians. Sequence analyzed by neighbor-joining indicated that both gene families are monophyletic with a high bootstrap value. Pairing of sequences from males and females of nonmammalian species showed there to be no significant difference between male and female sequences from a single species, consistent with autosomal locations. The molecular distances between murine Zfy-1, Zfy-2, and other ZFY-like sequences suggested that Zfy genes have undergone a period of rapid evolutionary change not seen in human ZFY.

Amino Acid Sequence↗

PubMed1998

Longitudinal study of inflammatory factors in serum, cerebrospinal fluid, and brain tissue in Alzheimer disease: interleukin-1beta, interleukin-6, interleukin-1 receptor antagonist, tumor necrosis factor-alpha, the soluble tumor necrosis factor receptors I and II, and alpha1-antichymotrypsin.

There is evidence consistent with the hypothesis that inflammatory and immune mechanisms are involved in the pathogenesis of Alzheimer disease (AD). We have investigated whether the levels of inflammatory associated proteins in serum or lumbar cerebrospinal fluid (CSF) reflect the progressive cognitive decline and brain atrophy of AD-patients. Levels of interleukin-1beta(IL-1beta), IL-1 receptor antagonist (IL-1ra), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), the soluble TNF receptors type I and II (sTNFR I and II), and the acute phase protein alpha1-antichymotrypsin (x1-ACT) were determined in paired serum and CSF samples taken yearly over a period of 2-5 years from pathologically confirmed AD patients (n = 8) and normal controls or non-AD subjects with other CNS pathology (n = 9). No significant differences were found between AD subjects and controls in the mean levels of the above mediators. There was also no correlation in either subject group between the levels of these inflammatory mediators in serum or CSF, and the change in cognitive status or the progression of the atrophy of the medial temporal lobe measured by X-ray computed tomography (CT). The concentrations of IL-1beta, IL-6, and TNF-alpha were determined in brain tissue specimens of five to nine different brain regions in six of the AD patients and four of the non-AD subjects. The levels of IL-1beta and IL-6 in the various brain regions were not significantly different in the AD and the non-AD group. However, in AD patients the level of TNF-alpha was significantly lower in the frontal cortex (32%, p = 0.024), the superior temporal gyrus (57%, p = 0.021), and the entorhinal cortex (49%, p = 0.009) compared with non-AD subjects. Low levels of TNF-alpha in the brain areas that showed neuropathology in AD may indicate a dysregulation of the inflammatory process in AD. Despite this finding, this study does not support the use of measurements of any of the inflammatory mediators investigated here as a diagnostic parameter for AD, due the large overlap in the levels of these factors between AD patients and other subjects, and the poor relation to clinical signs of AD.

Aged↗

PubMed1997

Stabilization of Xist RNA mediates initiation of X chromosome inactivation.

The onset of X inactivation is preceded by a marked increase in the level of Xist RNA. Here we demonstrate that increased stability of Xist RNA is the primary determinant of developmental up-regulation. Unstable transcript is produced by both alleles in XX ES cells and in XX embryos prior to the onset of random X inactivation. Following differentiation, transcription of unstable RNA from the active X chromosome allele continues for a period following stabilization and accumulation of transcript on the inactive X allele. We discuss the implications of these findings in terms of models for the initiation of random and imprinted X inactivation.

Alleles↗

PubMed1997

Molecular analysis in endometrial cancer.

The molecular events that occur during the development of endometrial carcinoma are largely uncharacterized. Carcinomas of the endometrium are associated as extracolonic malignant tumors in patients with hereditary nonpolyposis colorectal cancer syndrome. Endometrium and ovary may develop histologically homologue cancers especially endometrioid and papillary serous carcinomas. Colon and ovarian carcinoma might serve as model systems for the molecular analysis in endometrial carcinoma. We sought to analyze in endometrial carcinoma frequent molecular mechanisms of colon and ovarian carcinoma, including Ki-ras codon 12 mutations, microsatellite instability, p53 and c-erb B-2 immunohistochemical expression and allelic loss on chromosome 17q. Our results indicate that molecular mechanisms in endometrial carcinoma are different than those responsible for colorectal carcinomas and that uterine papillary serous carcinomas shares with its ovarian counterpart several molecular alterations in contrast to the histologically homologue uterine and ovarian endometrioid carcinoma. Furthermore there is a molecular basis to distinguish uterine endometrioid and papillary serous carcinoma.

Chromosome Deletion↗

PubMed1996

The practice of surgical staging and its impact on adjuvant treatment recommendations in patients with stage I endometrial carcinoma.

A survey of American gynecologic oncologists was undertaken to assess their compliance with current surgical staging criteria in patients with early endometrial carcinoma. One hundred forty-four members of the Society of Gynecologic Oncologists responded to the survey. Respondents treated an average of 22 new cases annually. Tumor grade and intraoperative determination of depth of myometrial invasion were demonstrated to influence the frequency of lymphatic dissection. In grade 1, 2, and 3 lesions, 76, 60, and 34% of responders, respectively, indicated that depth of invasion influenced their decision to perform lymphadenectomy. In addition, depth of invasion was important in determining type and extent of lymphatic resection. Further, the impact of pathologic lymph node status on postoperative adjuvant radiation therapy recommendations was evaluated for various stratifications of endometrial adenocarcinoma confined to the corpus. The greatest differences in treatment recommendations were noted in the 50-66% invasion category. For grade 1 and 2 cancers, adjuvant therapy recommendations were reduced by 23 and 16% respectively when comparing pelvic and combined therapy versus none and vaginal therapy. The effect of surgical staging data on clinical decisions is clearly evident. The knowledge of pathologically negative lymph node status reduces the recommendation for postoperative adjuvant radiotherapy in patients with adenocarcinoma otherwise confined to the uterine corpus.

Chemotherapy, Adjuvant↗

PubMed1996

LY290181, an inhibitor of diabetes-induced vascular dysfunction, blocks protein kinase C-stimulated transcriptional activation through inhibition of transcription factor binding to a phorbol response element.

Previous studies have shown that high glucose levels and diabetes induce an elevation in protein kinase C (PKC) activity in vascular cells and tissues susceptible to diabetic complications. In addition, PKC activation has been shown to modulate vascular cell growth, permeability, and gene expression, processes thought to be involved in the development of vascular complications. Using two in vivo model systems, we have identified a novel inhibitor of diabetic vascular dysfunction, LY290181. LY290181 prevented glucose-induced increases in blood flow and permeability in rat granulation tissue and corresponding vascular changes in the retina, sciatic nerve, and aorta of diabetic rats. Tested for its ability to inhibit PKC-regulated processes, LY290181 inhibited phorbol ester-stimulated plasminogen activator activity in a dose-dependent manner in bovine retinal endothelial cells and in human dermal fibroblasts. In addition, LY290181 inhibited phorbol ester-stimulated activation of the porcine urokinase plasminogen activator (uPA) promoter (-4600/+398) linked to the chloramphenicol acetyltransferase (CAT) reporter gene (p4660CAT). More detailed analysis of the uPA promoter revealed that LY290181 inhibited phorbol ester-stimulated activation of the uPA phorbol response element (-2458/-2349) located upstream of the thymidine kinase promoter (puPATKCAT). LY290181 appears to inhibit uPA promoter activation by blocking phorbol ester-stimulated binding of nuclear proteins to the uPA PEA3/12-0-tetradecanoylphorbol 13-acetate responsive element (TRE). These results suggest that LY290181 may inhibit diabetes-induced vascular dysfunction by inhibiting transcription factor binding to specific PKC-regulated genes involved in vascular function.

Animals↗

PubMed1996

Clinical and pathological significance of microsatellite instability in sporadic endometrial carcinoma.

Defective DNA mismatch repair in neoplasia is manifested by extra, aberrant bands within multiple microsatellite markers. The replication error (RER) phenotype is present in most colorectal and endometrial carcinomas in patients with the hereditary nonpolyposis colorectal carcinoma syndrome. In addition, a minority of sporadic colorectal and endometrial carcinomas are RER positive. RER in sporadic colorectal carcinomas has been associated with improved prognosis, but its clinical significance in sporadic endometrial cancer has not been characterized. We analyzed DNA extracted from 109 formalin-fixed sporadic endometrial carcinomas for microsatellite instability. The RER-positive phenotype was demonstrated by microsatellite instability in more than one of the eight dinucleotide markers tested. RER was correlated with pathological and clinical parameters as well as with immunohistochemical staining for the p53 gene product and alterations in codon 12 of Ki-ras. Nine percent of the endometrial carcinomas were RER positive, and RER was significantly associated with high grade and adverse outcome. We found no significant correlation of RER with histological subtype, stage, depth of invasion, mutations in the 12th codon of Ki-ras, or p53 immunoreactivity. We conclude that the RER phenotype is present in a minority of sporadic endometrial carcinomas and is associated with high grade and poor prognosis.

Adult↗

PubMed1995

The molecular biology of temperature-dependent sex determination.

Many reptiles do not have heteromorphic sex chromosomes and for these species sex is determined during embryogenesis by the temperature of egg incubation rather than at conception. The phenomenon of temperature-dependent sex determination (TSD) was discovered almost thirty years ago, but few advances have been made towards the elucidation of its mechanism. In the past few years substantial progress has been made in the understanding of the molecular basis of XY chromosomal (genetic) sex determination (GSD) through the discovery of SRY. It is now possible to start comparing TSD with GSD. TSD is found in some evolutionarily ancient vertebrates and has been postulated to be the ancestral process from which GSD has evolved. If this is true then the two mechanisms may share a common molecular basis. This paper details the current knowledge of TSD, our progress on the investigation of the involvement of SRY-type proteins, and finally presents some of the problems that need to be resolved to gain an understanding of the molecular basis of TSD.

Alligators and Crocodiles↗

PubMed1995

Surrogate endpoint biomarkers for cervical cancer chemopreventive trials.

Cervical intraepithelial neoplasia (CIN) represents a spectrum of epithelial changes that provide an excellent model for developing chemopreventive interventions for cervical cancer. Possible drug effect surrogate endpoint biomarkers are dependent on the agent under investigation. Published and preliminary clinical reports suggest retinoids and carotenoids are effective chemopreventive agents for CIN. Determination of plasma and tissue pharmacology of these agents and their metabolites could serve as drug effect intermediate endpoints. In addition, retinoic acid receptors could serve a both drug and biological effect intermediate endpoints. Possible biological effect surrogate endpoint biomarkers include cytomorphological parameters, proliferation markers, genomic markers, regulatory markers, and differentiation. Given the demonstrated causality of human papillomavirus (HPV) for cervical cancer, establishing the relationship to HPV will be an essential component of any biological intermediate endpoint biomarker. The pathologic effect surrogate endpoint biomarker for cervical cancer is CIN, used clinically for years. The desired effect for chemopreventive trials is complete regression or prevention progression. In planning chemoprevention trials, investigators need to consider spontaneous regression rates, the subjective nature of detecting CIN, and the impact of biopsy on regression. If intermediate endpoint biomarkers that met the above criteria were available for cervical cancer, then new chemopreventive agents could be rapidly explored. The efficacy of these new agents could be determined with a moderate number of subjects exposed to minimal risk over an acceptable amount of time. The impacts on health care for women would be significant.

Anticarcinogenic Agents↗

PubMed1995

Absence of an association between G-CSF support and clinical response in heavily pre-treated ovarian cancer patients receiving salvage chemotherapy with paclitaxel (Taxol).

This study was undertaken to determine if there was an association between the use of granulocyte colony-stimulating factor (G-CSF) and the clinical response to paclitaxel in patients with advanced ovarian cancer. Seventy-seven heavily pre-treated patients were given 135 mg/m2 paclitaxel every 21 days, with G-CSF support as necessary according to standard criteria. Patients were stratified into two subgroups according to the presence or absence of G-CSF use. The clinical response, progression-free interval (PFI) and survival were determined for each patient and analyzed relative to G-CSF use. Thirty-three patients received G-CSF support. The overall response rate was 32% (one complete and 24 partial) with similar patient numbers from each subgroup. The mean PFI and survival were not significantly different between the subgroups; 170.9 +/- 21.2 and 401 +/- 45.5 days (G-CSF) and 182.4 +/- 30.2 and 367 +/- 36 days (no G-CSF), respectively. We conclude that G-CSF use is not associated with response to paclitaxel in heavily pre-treated ovarian cancer patients.

Adult↗

PubMed1995

Mutations of the Ki-ras oncogene in carcinoma of the endometrium.

Mutations of the Ki-ras oncogene in endometrial carcinoma have been reported in Japan, but the prevalence and clinical significance of such mutations in the United States remains unclear. DNA extracted from paraffin sections of 112 carcinomas of the endometrium was amplified by the polymerase chain reaction with mismatched primers that generated a BstNI recognition site with the wild-type codon 12. Loss of this recognition site indicating Ki-ras codon 12 mutations was observed in 13 tumors (11.6%), including 11 endometrioid carcinomas, one undifferentiated carcinoma, and one carcinosarcoma. None of 17 papillary serous-clear cell carcinomas contained Ki-ras codon 12 mutations. These mutations were confirmed and characterized by direct sequencing. We found no evidence of correlation of the presence of Ki-ras mutations with stage, grade, depth of invasion, or clinical outcome. Our results indicate that Ki-ras oncogene mutations in carcinoma of the endometrium may be less prevalent in the United States than in Japan.

Adenocarcinoma↗

PubMed1995

Treatment of refractory ovarian carcinoma with paclitaxel and cisplatin after treatment failure with single-agent paclitaxel.

The clinical response to paclitaxel and cisplatin was evaluated in fifteen patients with refractory epithelial ovarian cancer who failed to respond to treatment with single agent paclitaxel. Patients received combination chemotherapy every 3 weeks with both 135 mg/m2 (9) or 175 mg/m2 (6) of paclitaxel and 50 mg/m2 (2), 75 mg/m2 (4) or 100 mg/m2 (9) of cisplatin. There was 1 complete clinical response, with 2 partial clinical responses for an overall response rate of 20%. The progression free interval was 6+ months for the complete responder and 9.5+ months for the partial responders. Overall five (33%) patients experienced an improvement in clinical response over that seen with paclitaxel alone, and 5 patients have died. Improvement in clinical response with combination chemotherapy compared to paclitaxel alone was positively associated with the cisplatin dose; while disease progression and death were inversely associated with the paclitaxel dose. Addition of cisplatin to paclitaxel may be useful in the treatment of patients who fail to respond to paclitaxel alone.

Adult↗

PubMed1994

Exponential regression of CA 125 during salvage treatment of ovarian cancer with taxol.

The role of serum CA 125 in monitoring the response of epithelial ovarian cancer to treatment has been extensively investigated. The exponential regression curve [1n(CA 125) = i+s (days after initiation of treatment)] has been reported to describe the rate of change of serum CA 125 during treatment. In this model, the y-axis intercept (i) represents the initial CA 125-secreting tumor burden, while the slope (s) is determined by the response to treatment. The exponential regression curve was calculated for 66 patients undergoing salvage chemotherapy with taxol. At a mean follow-up of 121 days, 50 (75%) patients had progressed and 35 (53%) had died. Stratification of the patients by stage, grade, or histology did not reveal any significant differences in the regression rate. When the patients were stratified by response, the mean regression rate was 0.0157 +/- 0.011 for patients with progressive disease (N = 19) vs -0.0250 +/- 0.031 for those with stable disease (N = 25) and -0.0250 +/- 0.015 for those with a partial response (N = 22) (P < 0.0001). The regression rate did not correlate with progression-free interval or survival (P > 0.05). We conclude that changes in serum CA 125 levels follow an exponential regression curve in patients undergoing salvage chemotherapy with taxol for progressive or recurrent ovarian cancer. A positive regression rate may predict which patients will progress prior to the time progression becomes clinically evident. However, a negative rate fails to provide discriminatory utility in predicting progression-free interval or survival.

Adult↗