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Biomedical subjects

H J Duncan

Publications and source records attributed to H J Duncan.

At least 19 recordsLinked to original sources
PubMed2005

Effects of polycyclic aromatic hydrocarbons on germination and subsequent growth of grasses and legumes in freshly contaminated soil and soil with aged PAHs residues.

The relevance of germination trials for screening plants that may have potential for use in the phytoremediation of PAH contaminated land was evaluated. The germination and subsequent growth of 7 grass and legume species were evaluated in soil spiked with a pure PAH mixture or coal tar and soil from a former coking plant heavily contaminated with aged PAHs. None of these treatments adversely affected germination of the plants. However, apart from Lolium perenne all species exhibited reduced growth in the coking plant soil after 12 weeks growth when compared to the untreated soil. In the coal tar spiked soil 4 out of the 7 species showed reduced growth, as did 3 out of the 7 in the soil spiked with a mixture of 7 PAHs. Therefore, germination studies alone would not predict the success of subsequent growth of the species tested in the ranges of soil PAH levels studied.

Biodegradation, Environmental↗
PubMed2003

Release studies of benzalkonium chloride from hydrogel in a freshwater environment.

The use of underwater optical sensors to monitor pollution and climate change processes has led to the development of robust instruments able to be deployed in lakes and seas for months at a time. However, despite this improvement in their durability they are subject to biofouling on their optical ports resulting in erroneous readings. The use of hydrogel coatings containing the cationic surfactant benzalkonium chloride (BAC) has been shown to prevent the development of biofouling for up to 12 weeks in the marine environment. In this study the use of hydrogel coatings in the freshwater environment was less successful with fouling visible at 2 weeks. In both field and laboratory studies a rapid initial loss of BAC from the hydrogel film was observed. The loss is a combination of diffusive and mass flow but the period from 12 to 50 h appeared to fit to diffusion kinetics and a diffusion coefficient of 7.3 x 10(-8) cm2 s(-1) (13 degrees C) was calculated, an order of 10 times greater than that found in seawater. Subsequently the rate of loss of the residual BAC, for which a diffusion coefficient of 5.7 x 10(-10) cm2 s(-1) (15 degrees C) was measured, was too low to prevent the early stages of biofouling.

Benzalkonium Compounds↗
PubMed2002

Method for the measurement of the diffusion coefficient of benzalkonium chloride.

Biofilm formation on the optical ports of cameras and underwater sensors is the primary cause of their reduced useful deployment time. The use of a transparent hydrogel coating containing the cationic surfactant benzalkonium chloride has been shown to extend the deployment times for up to 12 weeks for these instruments. In order to predict the effective lifetime of these coatings it was necessary to obtain the diffusion coefficient of the benzalkonium chloride used in the coatings. Benzalkonium chloride can have different alkyl chain lengths ranging from C8H17 to C18H37 with chain length greatly affecting its chemical properties. The benzalkonium chloride materials investigated here were mixtures of C12H25 and C14H29 as well as C14H29 on its own. These materials were selected for their proven biofilm resistant qualities. The diaphragm diffusion cell technique was investigated for its applicability to the measurement of diffusion coefficients of molecules with surfactant properties and the ability to form micelles. The method was found to be satisfactory for the cationic surfactant benzalkonium chloride. The average value of the membrane cell integral diffusion coefficient D was 7.78 x 10(-6) cm2 s(-1) at 25 degrees C and there was no significant effect of alkyl chain length on the measured value of D.

Benzalkonium Compounds↗
PubMed2001

The diagnosis of a conductive olfactory loss.

OBJECTIVES/HYPOTHESIS: Two of the most common causes of olfactory loss include upper respiratory infection (URI) and nasal or sinus disease. The etiology of most URI-related losses is thought to be viral and, as yet, there is no available treatment. In contrast, nasal or sinus disease produces an obstructive or conductive loss that often responds dramatically to appropriate therapy. Therefore, the distinction is important but in many cases may be difficult because such patients often present with no other nasal symptoms, and routine physical findings may be nonspecific. The purpose of this report is to characterize those aspects of the history and physical examination that will help to substantiate the diagnosis of a conductive olfactory loss. STUDY DESIGN: A retrospective, nonrandomized study of consecutive patients presenting with a primary complaint of olfactory loss. METHODS: This study reviewed 428 patients seen at a university-based taste and smell clinic from July 1987 through December 1998. Of this total, 60 patients were determined to have a conductive olfactory loss. All patients were referred specifically because of a primary chemosensory complaint. The University of Pennsylvania Smell Identification Test (UPSIT; Sensonics, Inc., Haddon Heights, NJ) was administered in all cases. RESULTS: The most commonly diagnosed etiologies of olfactory loss were head injury (18%), upper respiratory infection (18%), and nasal or sinus disease (14%). Of the 60 patients with a conductive loss, only 30% complained of nasal obstruction, whereas 58% described a history of chronic sinusitis. Only 45% reported that their olfactory loss at times seemed to fluctuate in severity. Anterior rhinoscopy failed to diagnose pathology in 51% of cases, whereas nasal endoscopy missed the diagnosis in 9%. Systemic steroids elicited a temporary reversal of conductive olfactory loss in 83% of patients who received them, offering a useful diagnostic maneuver, whereas topical steroids did so in only 25%. CONCLUSIONS: The etiology for olfactory loss can in many cases be difficult to determine, but it is important to establish prognosis and to predict response to therapy. Diagnosis requires a thorough history, appropriate chemosensory testing, and a physical examination that should include nasal endoscopy. A trial of systemic steroids may serve to verify that the loss is indeed conductive.

Adrenal Cortex Hormones↗
PubMed1998

Identification of obstructive sleep apnea in patients who snore.

As the field of sleep medicine has evolved, the clinical implications of obstructive sleep apnea (OSA) in snoring patients have become well accepted. Recent advances in surgical therapy for snoring allow otolaryngologists to offer simple outpatient treatment to patients with this problem. However, because the incidence of OSA in snorers seeking medical attention is unknown, the appropriate pretreatment evaluation of these patients is a subject of continued debate. Ninety-four snoring patients were recruited for a study to determine the incidence of OSA in this highly selected population. Subjects answered an extensive sleep questionnaire to determine factors that might suggest a diagnosis of OSA. Level III ambulatory sleep studies were performed on each participant. The incidence of OSA in this group was 72% (42% severe and 30% mild to moderate). Twenty of the subjects with OSA also underwent formal level I sleep studies, and the diagnosis of OSA was confirmed in each instance. Although there was a relationship between body mass index and OSA and certain questions correlated with OSA, the sensitivity and specificity of these data alone or in combination were too low to recommend their use in lieu of a formal sleep study. Given the remarkably high incidence of OSA in this group, which may reflect that seen by otolaryngologists who treat snoring, a sleep study should be performed to diagnose OSA and institute therapy for this condition. Level III ambulatory monitoring devices may be the most cost-effective alternative for evaluating this high-risk population.

Adult↗
PubMed1997

Prospective assessment of incontinence after radical retropubic prostatectomy: objective and subjective analysis.

OBJECTIVES: To assess prospectively-using pad test and questionnaire-the rate and degree of incontinence after radical retropubic prostatectomy, to analyze factors that may predispose individuals to postoperative incontinence, and to assess the impact of incontinence on patient lifestyle. METHODS: Fifty-one consecutive patients were assessed at 3-month intervals for 1 year after radical retropubic prostatectomy. Patients were objectively assessed using a 1-hour pad test and subjectively assessed by questionnaire. Incontinence was graded objectively according to the change in weight of the pad at 1 hour and subjectively by the number of pads used per day. Lifestyle modifications were assessed by questionnaire at 12 months. A number of variable factors were studied to assess risk factors for postoperative incontinence. RESULTS: Continence continued to improve up to 12 months. At 12 months, pad testing revealed 84% of patients were dry, 6% were mildly incontinent. 6% were moderately incontinent, and 4% were severely incontinent. Questionnaire assessment revealed 80% wore no pad, 14% had mild incontinence, 4% had moderate incontinence, and 2% had severe incontinence. Pad testing was not as sensitive as the questionnaire for the detection of minimal incontinence but was more reliable for moderate and severe levels. Patients made lifestyle changes proportional to the level of incontinence. No predisposing factor was identified for the development of incontinence after radical retropubic prostatectomy. CONCLUSIONS: Significant incontinence after radical prostatectomy occurs in as many as 10% of patients. Pad testing provides an inexpensive and simple form of objective assessment in patients with bothersome incontinence and allows documentation of improvement over time.

Aged↗
PubMed1995

Long-term follow-up of olfactory loss secondary to head trauma and upper respiratory tract infection.

OBJECTIVE: To determine the extent to which olfactory function can improve after loss induced by head trauma or a previous upper respiratory tract infection (URI) and the time for this improvement for more effective patient counseling. DESIGN: Patients initially evaluated at the University of Cincinnati (Ohio) Taste and Smell Center were reevaluated for olfactory loss with the University of Pennsylvania (Philadelphia) Smell Identification Test 1 to 5 years after initial testing. Changes in score on this test were used to indicate improvement in sensory function. Subjective information on olfactory ability and olfactory symptoms was also collected. SETTING: University-based tertiary care center. PATIENTS AND OTHER PARTICIPANTS: Forty-one patients with olfactory loss induced by head trauma (20) or previous URI (21). RESULTS: Seven (35%) of 20 patients with head trauma improved on the smell test by 4 points or more. Fourteen of 21 (67%) patients with a previous URI had improved scores of this magnitude or more. A statistically significant correlation was noted between the amounts of improvement and length of follow-up for URI patients. Thirteen of these patients also reported improved olfactory function. CONCLUSION: These findings for patients with head trauma are consistent with other reports of recovery of (or improvement in) olfactory function after trauma-induced loss. For patients with previous URI, these data indicate that improvement in olfactory function occurs, but the improvement may take several years.

Adult↗
PubMed1995

Olfactory disturbance in pediatric tracheotomy.

Several studies have described hyposmia after laryngectomy. The most common mechanism invoked is a reduction in nasal airflow, leading to elevated olfactory detection thresholds. Children with nasal obstruction have been shown to also have elevated olfactory detection thresholds linked to reduced nasal airflow. A child with a tracheotomy is in some degree similar to a laryngectomee. These patients will have variable amounts of nasal airflow reduction proportional to the degree of suprastomal obstruction. Our concern was that this alteration in nasal airflow may cause hyposmia. Furthermore, if the olfactory system requires adequate early stimulation for normal development (as is the case with vision and hearing), tracheotomy would be suspected to cause persistent hyposmia even after decannulation. Thus decreased olfactory sensitivity, delayed olfactory experience, or both could interfere with a child's ability to recognize and identify odor stimuli. We studied children aged 4 to 16 years with upper airway obstruction requiring tracheotomy and compared their abilities to identify familiar odorants with those of a large group of normal control children. None of the children had intrinsic mucosal or olfactory pathology. Statistical analysis of the early data shows a significant reduction in olfactory identification scores in the patients with tracheotomies, both by Student's t test and by the Wilcoxon rank sum test. Analysis of covariance confirmed age as an independent prognostic variable for identification ability. We therefore conclude that tracheotomy can reduce a child's ability to identify familiar odorants.

Adolescent↗
PubMed1992

Human olfactory biopsy. The influence of age and receptor distribution.

Thirty-six mucosal specimens were obtained with a biopsy instrument from the upper nasal septum of 12 human autopsy cases before the en bloc removal of the entire olfactory area. Examination of these 36 specimens with transmission electron microscopy demonstrated olfactory epithelium in only 17. A significant negative correlation (r = -.728) was noted between the age of the subject and the probability of obtaining olfactory epithelium, supporting the idea that the olfactory mucosa is gradually replaced by respiratory epithelium with aging. Using the en bloc specimens, the distribution of olfactory epithelium was reconstructed from light microscopic examination of silver-stained sections. Multiple patches of respiratory epithelium were observed over the upper portion of the nasal septum and superior turbinates, ie, the presumptive olfactory area. On transmission electron microscopic examination, frequent respiratory metaplasia was also suggested. Within the area of respiratory metaplasia, supporting cell-like and microvillar cell-like structures often were found; these structures may be remnants of olfactory epithelium. The sampling of olfactory tissue with a biopsy procedure is hampered by the irregular and patchy distribution of olfactory epithelium. The invasion of respiratory epithelial patches into the olfactory mucosa seems to be characteristic of the human olfactory epithelium and may increase as a function of age. Thus, conclusions about the structure of the olfactory mucosa in an individual patient must be based on several tissue samples.

Adult↗
PubMed1992

Assessing odor generalization in the rat: a sensitive technique.

In investigating the ability of the rat to discriminate among urine odors from mice of different genetic strains, we developed a technique for determining the extent of odor generalization. Trained rats performed a discrete trial, go/no-go procedure, touching a bar in the presence of an S+ odor for water reward. Rats easily learned this task and restricted their responding to trials with the S+ stimulus, even though there was no penalty for responding to S-. However, when presented with test stimuli that might be more similar to S+ or S-, some rats responded only to the S+, and not at all to S- or any generalization stimuli. We then created series of stimuli composed of different levels of adulteration of the S+ stimulus with generalization stimuli. With these stimuli, rats produced graded levels of responding, allowing comparisons of similarity among odorant stimuli. This technique can be applied to other types of odorant stimuli, particularly biological compounds of unknown concentration or purity, and should be of use in an operant laboratory studying odorant perception, or odorant characteristics.

Animals↗
PubMed1992

Role of the artificial urinary sphincter in the treatment of stress incontinence in women.

The artificial urinary sphincter (AUS) is rarely indicated in the treatment of women with stress incontinence because most of these women have deficient urethral support rather than pure sphincter weakness and the AUS is a treatment specifically for pure sphincter weakness. The procedure is contraindicated after pelvic radiotherapy and after previous sling surgery because of the high incidence of cuff erosion. Otherwise the artificial sphincter gives excellent results comparable to those seen in men with post-prostatectomy incontinence and much better than in neuropathic bladder dysfunction.

Adult↗
PubMed1992

Office management of taste and smell disorders.

Chemosensory disorders have been receiving increasing clinical attention but remain a difficult diagnostic problem. With the development of several well-standardized testing methods, taste or smell loss can now be verified, and this has added to knowledge concerning the common causes of dysfunction. Diagnosis typically rests upon the history and physical examination, but, except in the case of obstructive nasal and sinus pathologic conditions, therapy usually remains elusive.

Ambulatory Care↗
PubMed1991

A comparison of Doppler ankle pressures and skin perfusion pressure in subjects with and without diabetes.

Doppler ankle pressure measurements may be misleading in some patients because medial calcification has made the arteries of the leg incompressible. This problem is especially common in diabetics. Medical calcification that is not severe enough to make an artery clinically incompressible may cause an increased stiffness of the arterial wall that will limit the accuracy of Doppler ankle pressure measurements. A comparison of skin perfusion pressure, using an isotope technique, and Doppler ankle pressures was made in 226 subjects, diabetic and non-diabetic. Patients with incompressible arteries were excluded from the study. The slopes of the regression lines relating skin perfusion pressure to Doppler ankle pressure in diabetic and non-diabetic subjects were significantly different (P = 0.03). This result was consistent with the hypothesis that diabetic subjects have arteries that are less compressible than normal arteries and may make Doppler ankle pressure measurements in diabetic subjects misleading over the whole range of pressures recorded.

Ankle↗
PubMed1990

Organization of projections from olfactory epithelium to olfactory bulb in the frog, Rana pipiens.

One hypothesis for the coding of olfactory quality is that regions of the olfactory epithelium are differentially sensitive to particular odor qualities and that this regional sensitivity is conveyed to the olfactory bulb in a topographic manner by the olfactory nerve. A corollary to this hypothesis is that there is a sufficiently orderly connection between the epithelium and the olfactory bulb to convey this topographical coding. Thus we examined topography in the projection from epithelium to bulb in the frog, which has been the subject of numerous electrophysiological studies but has not yet been examined using modern neuroanatomical techniques. The tracer WGA-HRP was applied to the ventral or to the dorsal olfactory epithelium, or both. Anterograde transport of label to the olfactory bulb was seen after as few as 2 days; label was still present in the bulb as long as 21 days postinjection. In cases where WGA-HRP was applied to the entire epithelium, there was dense anterograde labelling of the ipsilateral olfactory bulb. In addition, a small medial portion of the contralateral bulb was labelled. Injections limited to either the ventral or dorsal epithelium produced patterns of anterograde labelling in the glomerular layer of the olfactory bulb, which varied with the size and location of the injection. With very large injections in either the dorsal or ventral epithelium, label appeared to be evenly distributed in the glomerular layer. With smaller injections in the ventral epithelium, there was heavier labelling in the lateral than in the medial portions of the glomerular layer, although light labelling was found in all regions of the glomerular layer. In contrast, injection sites restricted to the dorsal epithelium produced more anterograde labelling in the medial than lateral portions of the glomerular layer. These patterns extended throughout the dorsal-ventral extent of the bulb. Within the limits of the anterograde tracing technique used, we were unable to detect any systematic relationship between the pattern of labelling in the glomerular layer and the medial-lateral or rostral-caudal location of the injection site in either the ventral or dorsal epithelium. We conclude that in the frog, as in other amphibia, there is only a limited degree of topographic order between the epithelium and the olfactory bulb.

Animals↗
PubMed1988

A survey of the pectic content of nonlignified monocot cell walls.

The primary cell walls of graminaceous monocots were known to have a low content of pectin compared to those of dicots, but it was uncertain how widespread this feature was within the monocots as a whole. Nonlignified cell walls were therefore prepared from 33 monocot species for determination of their pectin content. It was not possible to solubilize intact pectins quantitatively from the cell walls, and the pectin content was assessed from three criteria: the total uronic acid content; the content of alpha-(1,4')-D-galacturonan isolated by partial hydrolysis and characterized by electrophoresis and degradation by purified polygalacturonase; and the proportion of neutral residues in a representative pectic fraction solubilized by sequential beta-elimination and N,N,N'N'-cyclohexanediaminetetraacetic acid extraction. Low galacturonan contents were restricted to species from the Gramineae, Cyperaceae, Juncaceae, and Restionaceae. Other species related to these had intermediate galacturonan contents, and the remainder of the monocots examined had high galacturonan contents comparable with those of dicots. The other criteria of pectin content showed the same pattern.

Journal Article↗
PubMed1986

Evaluation of an isotope washout technique to measure skin vascular resistance and skin perfusion pressure: influence of age, site and arterial surgery.

A simplified isotope washout technique has been devised to calculate the skin perfusion pressure (SPP) and skin vascular resistance (SVR). This test is simple, requires inexpensive equipment and is well tolerated by patients. SPP and SVR were calculated in 20 patients less than 30 years of age, 13 patients greater than 30 years of age and in 15 patients with peripheral vascular disease (PVD). With increasing age the SPP and SVR were increased. The SPP was similar to the mean arterial pressure in normal individuals but was decreased in patients with PVD. The SPP is a useful indicator of the severity of the PVD. The SPP and SVR were higher in the calf than in the foot. This is probably related to the decrease in pressure in the distal arterial tree. SPP was increased by 110% and skin blood flow by 190% by arterial reconstructive surgery. This test may be of use in assessing the effectiveness of arterial surgery.

Adolescent↗
PubMed1986

Skin vascular resistance and skin perfusion pressure as predictors of healing of ischemic lesion of the lower limb: influences of diabetes mellitus, hypertension, and age.

An isotope washout technique that requires inexpensive equipment and is well tolerated by patients has been developed to measure skin perfusion pressure (SPP) and skin vascular resistance (SVR). The SPP is a measure of the severity of peripheral vascular disease and the SVR is an indicator of microangiopathy associated with diabetes mellitus and hypertension. This test has been applied to 87 patients who had ischemic lesions of the lower limb. Fourty-four patients had lesions that healed with local treatment while the other 43 required major surgery. The presence of diabetes, hypertension, and old age reduced the likelihood of healing. Similarly if the SPP less than 40 mm Hg, only 18% of patients' lesions healed. If the SPP lay between 40 and 50 mm Hg and the SVR less than 1000 U, 67% of lesions healed. However, if the SPP was between 40 and 50 mm Hg and the SVR greater than 1000 U, no lesions healed. If the SPP greater than 50 mm Hg and SVR less than 1000 U, 83% of lesions healed, where as if the SVR greater than 1000 U, healing occurred in only 23% of lesions. This test can be used to predict the likelihood of healing of ischemic lesions of the lower leg, thus rationalizing their management. The importance of microangiopathy is also demonstrated.

Adult↗