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Biomedical subjects

D N Young

Publications and source records attributed to D N Young.

7 recordsLinked to original sources

pH-dependent chalcogenopyrylium dyes as potential sensitizers for photodynamic therapy: selective retention in tumors by exploiting pH differences between tumor and normal tissue.

Ideal photosensitizers have long-wavelength absorption and strong tumor selectivity with rapid clearance from normal tissues. The telluroselenopyrylium dye 1 that absorbs light at 795 nm (epsilon = 285,000 M-1 cm-1) has a novel property that enhances the tumor specificity and normal tissue clearance. After intralesional injection to both tumors and surrounding skin, it disappeared from the normal skin of BALB/c mice faster than it did from subcutaneously implanted Colon 26 tumors, which resulted in therapeutic selectivity. In vivo reflectance spectroscopy showed that the half-life in tumor was about 50 min while in skin it was around 12 min. This phenomenon appears to be related to the pH differences in normal skin versus tumor, because the rates of drug hydrolysis in solution were shown to be sensitive to changes in pH. Inhibition of tumor regrowth following intratumoral photosensitizer administration depended on both light dose and drug dose, as well as the time interval between dye injection and irradiation; selectivity depended on the time interval. Although treatment parameters were not optimized efficacy was superior to systemic Photofrin under our standard conditions. We discuss how new, more optimal, photosensitizers can be designed that use rates of hydrolysis to exploit the differences in pH between normal tissue and tumor.

Animals↗

Videofluoroscopy in cervical spine trauma: an interinterpreter reliability study.

OBJECTIVE: The primary purpose of this study was to determine if, when confronted with a series of cervical videofluoroscopic (VF) studies, board certified radiologists who are trained in the interpretation of VF spinal examinations would be in agreement with one another with regard to the findings of normal, hypomobile or hypermobile intersegmental motion. As a secondary objective, we polled participating physicians regarding demographic issues such as time in practice, self-assessment of proficiency, the type of training received in VF interpretation and the number of VF studies read per year, in order to determine if any of these factors had any predictive value in terms of interexaminer agreement. DESIGN: Seven patients who had been exposed to cervical acceleration/deceleration (CAD) trauma from motor vehicle accidents were randomly selected from the practice of two of the authors (ACC and JSK). Three volunteers, who were asymptomatic and had no history of neck pain or injury to the neck, were also recruited. In all cases, informed consent was obtained in accordance with the Helsinki guidelines. Ten board qualified chiropractic radiologists were recruited to participate in this study. Blinded to the history and identity of the patients and volunteers, the participants were asked to view the 10 VF studies and, in each case, to report either "normal," "hypomobile" or "unable to determine" for all segments from OCC/C1 through C7/T1. The resulting data was analyzed for concordance using the kappa statistic. Kappa was calculated for all segments (OCC-T1) for agreement in "normal" vs. "abnormal" motion. The two possible choices for abnormal (i.e., hypermobility and hypomobility) were pooled together. We also compared the results of participants' responses to demographic questions with the results of their interpretations of the VF studies. SETTING: An urban group practice. Four of the patients were those of an orthopedist (ACC) and three were those of a general practitioner (JSK). PATIENT/OTHER PARTICIPANTS: Seven patients were randomly selected from a larger group of patients satisfying our selection criteria. Patients were chosen who had been exposed to CAD trauma and had been provided with at least 6 months of conservative chiropractic care, yet remained symptomatic as a result of their injuries. All had evidence of intersegmental instability in the cervical spine as defined by other investigators and none had any history of injury or pain in the cervical spine prior to their motor vehicle accident. Four males and three females with a mean age of 16 yr comprised the patient group. Two asymptomatic atraumatic volunteers were males and one was female. They were age matched to the patient group with a mean age of 38 yr. INTERVENTION: This study did not entail any form of intervention. MAIN OUTCOME MEASURES: Our primary outcome measure was that of concordance or agreement between our group of 10 participant radiologists in regard to their interpretations of the 10 VF studies provided to them, i.e., that of interinterpreter reliability. Higher values of kappa suggested that agreement between the radiologists was not likely due to chance alone. Our secondary outcome measure was a correlation between the results of our demographic questionnaires, completed by participating radiologists, and the overall interinterpreter reliability concordance. The hypothesis tested was that radiologists who have institutional training in VF, more years of experience, and those who read more VF studies annually and self-rank their proficiency as "high" are more likely to agree with others and/or are more likely to correctly analyze intersegmental motion than those whose training was less formal, and who have less experience, read fewer VF studies and self-rank their proficiency in reading VF as only "adequate" or lower. (ABSTRACT TRUNCATED)

Adolescent↗

Antibody to coliform antigens in urine samples from patients with symptoms of urinary tract infection.

An enzyme linked immunoadsorbent assay (ELISA) was used to detect IgG, IgM, and IgA antibody in urine to a crude antigenic mixture prepared from six arbitrarily chosen strains of common coliform urinary pathogens. In a group of patients with symptoms of urinary tract infection 24 of 80 (30%) urine samples were positive on culture by conventional methods, 58 of 80 (72.5%) were positive for polymorphs on microscopy, and 72 of 80 (90%) were positive for antibody by ELISA. Secretory component was detected in 28 of 80 (35%) samples, and this is consistent with local antibody production. The results show that antibody can be detected in a wide range of urine samples using a simple antigen mixture, and this may form the basis of a useful test to diagnose urinary tract infection.

Antibody Specificity↗

Effects of intracerebroventricular L-DOPA on caudate unit firing.

Single units were recorded bilaterally from the caudate nuclei of cats before and after 50 microliter injections of either Merlis solution or L-DOPA (200 microgram) dissolved in Merlis into the left lateral cerebral ventricle. After injection of L-DOPA, but not Merlis solution, there was a period of unit silence in both caudates with an onset of about 10 min and a duration of 30-50 min. This period of caudate silence was coincident with a significant reduction of systolic blood pressure and heart rate. Upon resumption of unit firing in caudate, it was found that the interspike intervals on the contralateral side were markedly increased from 30 min-2 hr postinjection while there was no change on the side of injection. The similarity of this response to that following lesions which interrupt the caudate to thalamus pathway unilaterally was discussed. It is suggested that L-DOPA injection may produce this lesion-like effect by altering the firing of caudate output neurons.

Action Potentials↗

Evaluating the quality of clinical practice guidelines.

OBJECTIVE: To review and identify established methods for evaluating the quality of practice guidelines and to use a selected assessment tool to assess 2 chiropractic practice guideline documents. METHODS: A search of the medical literature was performed to identify current methods and procedures for practice guideline evaluation. Two chiropractic practice guideline documents, Vertebral Subluxation in Chiropractic Practice (CCP) and Guidelines for Chiropractic Quality Assurance and Practice Parameters (Mercy) were then independently evaluated for validity by 10 appraisers using the identified appraisal tool. The appraisal scores were tabulated, and consensus appraisals were generated for the CCP and Mercy guideline documents. RESULTS: The "Appraisal Instrument for Clinical Guidelines" (Cluzeau instrument) was identified as a reliable and valid method of guideline evaluation. The result of the application of this appraisal tool in the assessment of the CCP and Mercy guideline documents was that the former scored notably lower than the latter. On the basis of the results of the guideline appraisals, the CCP document is not recommended, and its guidelines are not considered suitable for application in chiropractic practice. The Mercy guidelines are recommended for application in chiropractic practice, with the proviso that new scientific data should be considered. CONCLUSIONS: The literature reviewed suggests that professional organizations or groups should undertake a critical review of guidelines using available critical guideline appraisal tools. Guideline validity appraisal should be done before acceptance by the chiropractic profession. To avoid unwarranted utilization of poorly constructed guidelines, it is strongly recommended that all future guidelines be reviewed for validity and scientific accuracy with the findings published in a medically indexed journal before they are adopted by the chiropractic community.

Chiropractic↗