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J A Clark

Publications and source records attributed to J A Clark.

At least 19 recordsLinked to original sources
PubMed2004

Precise mass measurement of 68Se, a waiting-point nuclide along the rp process.

Mass measurements of 68Ge, 68As, and 68Se have been obtained with the Canadian Penning Trap mass spectrometer. The results determine the mass excess of 68Se as -54 232(19) keV, the first measurement with a precision and reliability sufficient to address the light-curve and energy output of x-ray bursts as well as the abundances of the elements synthesized. Under typical conditions used for modeling x-ray bursts, 68Se is found to cause a significant delay in the rp process nucleosynthesis.

Journal Article↗
PubMed2004

Prenatal nicotine exposure increases connective tissue expression in foetal monkey pulmonary vessels.

Among the many deleterious effects of maternal smoking during pregnancy on foetal development, is a higher incidence of persistent pulmonary hypertension. The recent identification of nicotinic acetylcholine receptors (nAChR) on cells of the pulmonary vessel walls suggests that maternal smoking during pregnancy may produce morphological alterations in foetal pulmonary vasculature. Timed-pregnant rhesus monkeys were treated with nicotine (1 mg x kg(-1) x day(-1)) delivered by subcutaneous osmotic mini-pumps from days 26-134 of gestation (term: 165 days). Lung sections from 134-day foetal monkeys were used for morphometric analysis, in situ hybridisation and immunohistochemical staining. Following nicotine treatment, total wall and tunica adventitia thickness of airway associated vessels (AAV) increased significantly. Nicotine exposure significantly increased collagen I and III mRNA and protein in tunica adventitia in all AAV but not in tunica media. By contrast, levels of elastin protein were significantly decreased. alpha7 nAChR were detected in AAV fibroblasts that expressed collagen mRNA. Choline acetyltransferase, the enzyme which synthesises acetylcholine, the ligand for alpha7 nAChR was also detected in endothelium and fibroblasts. These findings suggest that with smoking during pregnancy, nicotine is transported across the placenta and directly interacts with nicotinic acetylcholine receptors in pulmonary vessels to alter connective tissue expression and therefore produce vascular structural alterations.

Animals↗
PubMed2003

Treatment of toxic epidermal necrolysis with intravenous immunoglobulin.

Toxic epidermal necrolysis (TEN) is a rare severe reaction of the skin resulting in full thickness damage to the epidermis. The condition has significant morbidity as a result of dehydration, protein loss, thermoregulatory difficulties, and renal, lung, liver and heart failure. The mortality rate approaches 30%, most commonly from bacterial sepsis. Management of this condition is cessation of the suspected causative agent and supportive care on a burns or intensive care unit. There have been recent reports of treatment using intravenous immunoglobulin (IVIG) therapy, though its efficacy is yet to be established. It has been proposed that IVIG inhibits the Fas-FasL mediated apoptosis of keratinocytes affected by TEN. We describe a case of extensive drug-induced TEN in a 33-year-old woman who showed rapid improvement with IVIG therapy at a dose of 0.75 g/kg/day given for four consecutive days.

Adult↗
PubMed2001

Changes in central steroid receptor expression, steroid synthesis, and dopaminergic activity related to the reproductive cycle of the ring dove.

This review examines possible neural mechanisms involved in the expression of parental behavior in the ring dove, Streptopelia risoria. This avian species has proved an excellent animal model for studies concerning endocrine-behavior interactions for many years. Studies were performed to localize the expression of central androgen and progesterone receptor in both sexes. Expression of androgen receptor (androgen receptor immunoreactivity, AR-ir) was widespread but increased, similarly in both sexes, with increasing day-length. Progesterone receptor-immunoreactivity (PR-ir) was more localized in several discrete areas of the hypothalamus. Similarly, no sex differences were observed in PR-ir, and expression increased in birds maintained on long days. AR-ir demonstrated dramatic changes over the breeding cycle, being greatest in courting birds and almost undetectable in parenting birds of both sexes brooding their young. PR-ir showed a differential expression over the breeding cycle relative to its hypothalamic localization. PR-ir decreased in the tuberal hypothalamic area in brooding birds of both sexes; whereas in the preoptic area, PR-ir was maintained. Significant increases in dopaminergic activity during the parenting phase of the breeding cycle occurred in specific neural regions including the PVM and DMA. Studies demonstrated the ability of the diencephalon of both sexes of the ring dove brain to synthesize progesterone, with indications that in the male brooding dove, synthesis is increased. Finally, a model is presented that proposes a mechanism whereby these central systems may interact to result in the expression of full parental behavior in both sexes of the ring dove.

Animals↗
PubMed2001

Failure of ductus arteriosus closure and remodeling in neonatal mice deficient in cyclooxygenase-1 and cyclooxygenase-2.

The transition to pulmonary respiration following birth requires rapid alterations in the structure of the mammalian cardiovascular system. One dramatic change that occurs is the closure and remodeling of the ductus arteriosus (DA), an arterial connection in the fetus that directs blood flow away from the pulmonary circulation. A role for prostaglandins in regulating the closure of this vessel has been supported by pharmacological and genetic studies. The production of prostaglandins is dependent on two cyclooxygenases (COX-1 and COX-2), which are encoded by separate genes. We report here that the absence of either or both COX isoforms in mice does not result in premature closure of the DA in utero. However, 35% of COX-2(-/-) mice die with a patent DA within 48 h of birth. In contrast, the absence of only the COX-1 isoform does not affect closure of the DA. The mortality (35%) and patent DA incidence due to absence of COX-2 is, however, significantly increased (79%) when one copy of the gene encoding COX-1 is also inactivated. Furthermore, 100% of the mice deficient in both isoforms die with a patent DA within 12 h of birth, indicating that in COX-2-deficient mice, the contribution of COX-1 to DA closure is gene dosage-dependent. Together, these data establish roles for COX-1, and especially for COX-2, in the transition of the cardiopulmonary circulation at birth.

Animals↗
PubMed2001

Living with treatment decisions: regrets and quality of life among men treated for metastatic prostate cancer.

PURPOSE: To examine variation in men's long-term regret of treatment decisions, ie, surgical versus chemical castration, for metastatic prostate cancer and its associations with quality of life. METHODS: Survey of previously treated patients to assess treatment decisions and quality of life, supplemented with focus groups. Two items addressing whether a patient wished he could change his mind and the belief that he would have been better off with the treatment not chosen were combined in classifying survey respondents as either satisfied or regretful. Chi(2) and t tests were used to test associations between regret and treatment history, complications, and quality of life. RESULTS: Survey respondents included 201 men aged 45 to 93 years (median, 71 years), who had begun treatment (71% chemical castration, 29% orchiectomy) a median of 2 years previously. Most reported complications: hot flashes (70%), nausea (34%), and erectile dysfunction (81%). Most were satisfied with the treatment decision, but 23% expressed regret. Regretful men more frequently reported surgical (43%) versus chemical (36%) castration (P: = .030) and nausea in the past week (54% v 32%; P: = .010) but less frequently reported erectile dysfunction (56% v 72%; P: = .048). Regretful men indicated poorer scores on every measure of generic and prostate cancer-related quality of life. Qualitative analyses revealed substantial uncertainty about the progress of their disease and the quality of the decisions in which patients participated. CONCLUSION: Regret was substantial and associated with treatment choice and quality of life. It may derive from underlying psychosocial distress and problematic communication with physicians when decisions are being reached and over subsequent years.

Aged↗
PubMed2001

Spontaneous adverse event signaling methods: classification and use with health care treatment products.

AE signal detection and its techniques are part of the continuum of public health surveillance, borrowing from both its theory and application (171). Like public health surveillance networks, whose major goals are to identify early signs of new outbreaks, pinpoint new organisms, and monitor designated illnesses, AE signaling and surveillance systems attempt to provide early warnings of previously unsuspected product-AE pairs, hypothesize potential drug-event relations, identify populations "at risk," and facilitate case ascertainment and definition. In both examples, definitive research is often subsequently undertaken to quantify the strength of relations that may be proposed. As with any public health surveillance effort, AE surveillance provides an infrastructure for the ongoing collection of health data and its direct integration into the health regulatory policy (172), including its keystone role in risk assessment and management. However, unlike many surveillance systems, postmarketing AE systems collect case information that is often relatively incomplete and imperfect, estimate exposure based on surrogate values (e.g., sales data), and are used by both governmental and the private sector for preventive planning. These factors make AE signaling and surveillance more ambiguous, regulatory oriented, and complex than its disease counterparts (173). Despite such issues, AE signaling methods continue to evolve in extent, complexity, and acceptance (4, 131, 174). Undoubtedly, this is largely due to the widespread practical experience that has been gained with spontaneous reporting systems over the past 4 decades and the cumulative usefulness that has been demonstrated.

Adverse Drug Reaction Reporting Systems↗
PubMed2001

Symptom indexes to assess outcomes of treatment for early prostate cancer.

BACKGROUND: Patients' perceptions of treatment outcomes are important in the management of early prostate cancer, but few studies have offered reliable and responsive measures to assess the likely side effects of the most common treatments. OBJECTIVE: To develop indexes of urinary, bowel, and sexual function, and related distress. RESEARCH DESIGN: Prospective cohort study of the outcomes of treatment for early prostate cancer, with self-administered questionnaires completed before treatment, and 3 and 12 months afterward. Hypothesized indexes, based on a clinical model of pathophysiological side effects of treatment, were defined and evaluated with respect to reliability and validity. SUBJECTS: Patients (n = 184) undergoing radical prostatectomy or external beam radiotherapy for early prostate cancer. MEASURES: Urinary and bowel items pertained to frequency or intensity of symptoms of dysfunction; parallel items assessed symptom-related distress. Sexual dysfunction items assessed the quality of erections, orgasm, and ejaculation; distress was assessed by 2 items adapted from the MOS Sexual Problems (MOS-SP) scale. HRQoL was assessed by the SF-36 and Profile of Mood States. RESULTS: Symptom and symptom-related distress indexes for urinary incontinence, urinary obstruction/irritation, bowel dysfunction, and sexual dysfunction were defined. Symptom and distress indexes in each domain were highly correlated. Responsiveness was substantial and varied by treatment in ways consistent with clinical experience. The indexes accounted for significant proportions of the variance in HRQoL measures. CONCLUSIONS: These indexes may be used in monitoring outcomes of treatment for early prostate cancer.

Aged↗
PubMed2001

Sexuality after treatment for early prostate cancer: exploring the meanings of "erectile dysfunction".

OBJECTIVE: To explore perceptions of the impact of erectile dysfunction on men who had undergone definitive treatment for early nonmetastatic prostate cancer. DESIGN: Seven focus groups of men with early prostate cancer. The groups were semistructured to explore men's experiences and quality-of-life concerns associated with prostate cancer and its treatment. SETTING: A staff model health maintenance organization, and a Veterans Affairs medical center. PATIENTS: Forty-eight men who had been treated for early prostate cancer 12 to 24 months previously. RESULTS: Men confirmed the substantial effect of sexual dysfunction on the quality of their lives. Four domains of quality of life related to men's sexuality were identified: 1) the qualities of sexual intimacy; 2) everyday interactions with women; 3) sexual imagining and fantasy life; and 4) men's perceptions of their masculinity. Erectile problems were found to affect men in both their intimate and nonintimate lives, including how they saw themselves as sexual beings. CONCLUSIONS: Erectile dysfunction, the most common side effect of treatment for early prostate cancer, has far-reaching effects upon men's lives. Assessment of quality of life related to sexual dysfunction should address these broad impacts of erectile function on men's lives. Physicians should consider these effects when advising men regarding treatment options. Physicians caring for patients who have undergone treatment should address these psychosocial issues when counseling men with erectile dysfunction.

Aged↗
PubMed2001

Transcatheter embolotherapy of maternal pulmonary arteriovenous malformations during pregnancy.

STUDY OBJECTIVES: To determine if transcatheter embolotherapy is safe and effective for the treatment of pulmonary arteriovenous malformations during pregnancy. DESIGN: Prospective study. SETTING: Specialized hereditary hemorrhagic telangiectasia centers at Yale University School of Medicine and St. Michael's Hospital, University of Toronto. PATIENTS: Seven pregnant women (age range, 24 to 34 years; gestational age range, 16 to 36 weeks) undergoing transcatheter embolotherapy. INTERVENTIONS: Transcatheter embolotherapy in all patients. MEASUREMENTS AND RESULTS: Thirteen pulmonary arteriovenous malformations in seven patients were embolized with detachable silicone balloons and/or stainless steel coils without incident. The estimated fetal radiation dose ranged from < 50 to 220 mrad. No complications of pulmonary arteriovenous malformations occurred in any of the patients after transcatheter embolotherapy. The mothers went on to deliver healthy babies in all cases. CONCLUSIONS: Transcatheter embolotherapy of maternal pulmonary arteriovenous malformations performed by an experienced radiologist appears to be safe and effective after 16 weeks of gestational age.

Adult↗
PubMed2001

Communication about prostate cancer between men and their wives.

OBJECTIVES: Metastatic prostate cancer is a serious disease that affects both men and their intimate partners. We explored the perceptions of men who have been treated for metastatic prostate cancer and the views of their wives regarding the changes that were caused by prostate cancer and its treatment. STUDY DESIGN: We conducted retrospective focus group interviews with married men and separate focus groups with their wives. POPULATION: Twenty married men (11 white and 9 African American) with an average age of 69 years (range=60-82 years) and 7 of the wives (5 white and 2 African American) participated in our study. Thirteen of the men were treated with orchiectomy, and 7 received monthly hormone ablation therapy. OUTCOMES MEASURED: We compared the accounts of husbands and wives concerning the diagnosis and treatment of prostate cancer. RESULTS: The participants' accounts indicate little spousal communication about the implications of prostate cancer on their lives. In particular, couples appear to talk little about their emotions, worries, and fears. CONCLUSIONS: Although wives have a profound interest in their husbands' prostate cancer, actual communication about the disease, its treatment, and the feelings it evokes may be less than we believe. Noncommunication in marriages might indicate that these couples are at increased risk for poor adjustment to prostrate cancer.

Adaptation, Psychological↗
PubMed2001

Long-term treatment related complications of brachytherapy for early prostate cancer: a survey of patients previously treated.

PURPOSE: We determined long-term symptoms in patients after brachytherapy (radioactive seed implantation) for early (nonmetastatic) prostate cancer. MATERIALS AND METHODS: We performed a cross-sectional survey of 105 (80% of those contacted) men treated at least 2 years 9 months (median 5.2 years) previously with brachytherapy alone (72 patients) or brachytherapy plus external beam radiation therapy (33) at a pioneering referral center for ultrasound guided brachytherapy. RESULTS: Median patient age was 70 years at treatment and 75 years when surveyed. Bowel symptoms were uncommon (range 4% to 9%) unless patient had also received external beam radiation therapy. Urinary incontinence occurred in 45% of men, although leakage of more than a few drops, daily leakage and wearing absorptive pads occurred in 11%, 11% and 16%, respectively. Men who underwent documented transurethral prostatic resection were much more likely to report incontinence (83% versus 39%, p = 0.005) and those who underwent implantation less than 5 years earlier were less likely (33% versus 53%, respectively, p = 0.04). Complete impotence was common (50%) but impaired erections were more so (73%). Patients who received combined radiation treatment had more frequent erectile dysfunction. CONCLUSIONS: Long-term bowel symptoms are infrequent after brachytherapy alone. Urinary incontinence is common, although usually only a few drops and not daily. Erectile dysfunction, prevalent in populations of older men, was found in most men. However, because our study design precluded documenting baseline symptoms before treatment and subsequent clinical interventions, the contribution of factors other than brachytherapy is unclear. The morbidity of patients receiving more recent brachytherapy may be less.

Aged↗
PubMed2000

Protein kinase C signaling mediates a program of cell cycle withdrawal in the intestinal epithelium.

Members of the protein kinase C (PKC) family of signal transduction molecules have been widely implicated in regulation of cell growth and differentiation, although the underlying molecular mechanisms involved remain poorly defined. Using combined in vitro and in vivo intestinal epithelial model systems, we demonstrate that PKC signaling can trigger a coordinated program of molecular events leading to cell cycle withdrawal into G(0). PKC activation in the IEC-18 intestinal crypt cell line resulted in rapid downregulation of D-type cyclins and differential induction of p21(waf1/cip1) and p27(kip1), thus targeting all of the major G(1)/S cyclin-dependent kinase complexes. These events were associated with coordinated alterations in expression and phosphorylation of the pocket proteins p107, pRb, and p130 that drive cells to exit the cell cycle into G(0) as indicated by concomitant downregulation of the DNA licensing factor cdc6. Manipulation of PKC isozyme levels in IEC-18 cells demonstrated that PKCalpha alone can trigger hallmark events of cell cycle withdrawal in intestinal epithelial cells. Notably, analysis of the developmental control of cell cycle regulatory molecules along the crypt-villus axis revealed that PKCalpha activation is appropriately positioned within intestinal crypts to trigger this program of cell cycle exit-specific events in situ. Together, these data point to PKCalpha as a key regulator of cell cycle withdrawal in the intestinal epithelium.

Animals↗