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Biomedical subjects

J M Harris

Publications and source records attributed to J M Harris.

At least 91 records · Page 5Linked to original sources
PubMed1998

Visual search for motion-in-depth: stereomotion does not 'pop out' from disparity noise.

In a visual search task, targets defined by motion or binocular disparity stand out effortlessly from stationary distractors ('pop-out'), suggesting that target and distractors are processed by different neural mechanisms. We used pop-out to explore whether motion directly toward or away from the observer (z-motion) is detected using binocular motion cues. A target moving laterally (x-motion) popped out amid stationary distractors with binocular disparity, but z-motion did not pop out. However, a small x-motion added to the target's z-motion caused it to pop out. We therefore suggest that the visual system may not be specifically sensitive to binocular motion differences.

Artifacts↗
PubMed1998

Malone antegrade continence enemas for autonomic dysreflexia secondary to neurogenic bowel.

A 42-year-old man with T-4 ASIA B thoracic paraplegia presented with chronic constipation, fecal incontinence, and bowel-related autonomic dysreflexia (AD) refractory to conservative bowel program. His usual toileting time lasted one to five hours. Antegrade continence enemas (ACE) were performed. The ACE technique, which requires creating a continent catheterizable appendicocecostomy, is described. Postoperatively, a daily enema was given through the stoma. The patient's toileting time was reduced to 20 minutes and his AD resolved. The role of the ACE is discussed in adult spinal cord injury (SCI).

Adult↗
PubMed1998

Risk factors for sensitisation and respiratory symptoms among workers exposed to acid anhydrides: a cohort study.

OBJECTIVES: To examine the relation between exposure to acid anhydrides and the risk of developing immediate skin prick test responses to acid anhydride human serum albumin (AA-HSA) conjugates or work related respiratory symptoms; to assess whether these relations are modified by atopy or smoking. METHODS: A cohort of 506 workers exposed to phthalic (PA), maleic (MA), and trimellitic anhydride (TMA) was defined. Workers completed questionnaires relating to employment history, respiratory symptoms, and smoking habits. Skin prick tests were done with AA-HSA conjugates and common inhalant allergens. Exposure to acid anhydrides was measured at the time of the survey and a retrospective exposure assessment was done. RESULTS: Information was obtained from 401 (79%) workers. Thirty four (8.8%) had new work related respiratory symptoms that occurred for the first time while working with acid anhydrides and 12 (3.2%) were sensitised, with an immediate skin prick test reaction to AA-HSA conjugates. Sensitisation to acid anhydrides was associated with work related respiratory symptoms and with smoking at the time of exposure to acid anhydride. When all subjects were included and all three acid anhydrides were taken into account there was no consistent evidence for an exposure-response relation, but with the analysis restricted to a factory where only TMA was in use there was an increased prevalence of sensitisation to acid anhydrides and work related respiratory symptoms with increasing full shift exposure. This relation was apparent within the current occupational exposure standard of 40 micrograms.m-3 and was not modified significantly by smoking or atopy. CONCLUSIONS: Intensity of exposure and cigarette smoking may be risk factors for sensitisation to acid anhydrides. Exposure is also a risk factor for respiratory symptoms. As there was evidence for sensitisation to TMA at full shift exposures within the occupational exposure standard this standard should be reviewed.

Adolescent↗
PubMed1998

Retrospective exposure assessment for a cohort study into respiratory effects of acid anhydrides.

OBJECTIVES: To estimate past exposure to phthalic (PA), trimellitic (TMA) and maleic anhydride (MA) in three alkyd resin and one cushioned flooring factory to estimate exposure-response relations in a retrospective cohort study. METHODS: Personal exposure measurements were carried out in 1992 and quantitative and qualitative information on past exposure and production processes were collected. Job titles were ranked by decreasing exposure and amalgamated into job categories and exposure groups. Multiplication factors for back calculating past exposure levels were estimated with past exposure data, or if no such data were available these factors were estimated by a panel of occupational hygienists. Exposure levels were back calculated starting with the exposure levels in 1992. RESULTS: High exposures to PA were estimated to have occurred among workers operating the PA melting pots in factory 1 (estimated exposure in 1960-9 was 2480 micrograms.m-3). Highest concentrations of TMA were estimated to have occurred among the ink mixers in factory 2 from 1979 to 1986 (554 micrograms.m-3). Exposure in most other job titles was thought to be fairly constant over time for PA, TMA, and MA. CONCLUSIONS: Exposure to acid anhydride at these factories has fallen during the period covered by the study. However, it is estimated that in only one job in factory 2 did past exposure to acid anhydride exceed the current occupational exposure standard. Accuracy of the estimated exposure is limited by a paucity of reliable past exposure data.

Anhydrides↗
PubMed1998

Malone antegrade continence enema for adults with neurogenic bowel disease.

PURPOSE: We describe the outcomes of adults with neurogenic bowel disease who underwent a Malone antegrade continence enema procedure with or without concomitant urinary diversion. MATERIALS AND METHODS: Consecutive adult patients with neurogenic bowel disease who underwent an antegrade continence enema procedure (continent catheterizable appendicocecostomy for fecal impaction) were retrospectively reviewed. RESULTS: Of the 7 patients who underwent an antegrade continence enema synchronous urinary procedure (ileal conduit, augmentation ileocystoplasty with continent catheterizable abdominal stoma or augmentation ileocystoplasty) was also performed in 6. Mean patient age was 32 years and mean followup was 11 months. Of the 7 patients 6 who self-administered antegrade continence enemas regularly were continent of stool per rectum and appendicocecostomy, using the appendicocecostomy as the portal for antegrade enemas. All 6 compliant patients reported decreased toileting time and improved quality of life. Preoperative autonomic dysreflexia resolved postoperatively in 3 patients. All urinary tracts were stable. In 4 patients 5 complications occurred, including antegrade continence enema stomal stenosis requiring appendicocutaneous revision (1), antegrade continence enema stomal stenosis requiring dilation (1), superficial wound infection (1), small bowel obstruction requiring lysis of adhesions (1) and urinary incontinence (1 who underwent continent urinary diversion). CONCLUSIONS: Patients with neurogenic bladder and bowel disease may benefit from antegrade continence enema performed synchronously with a urinary procedure. Antegrade continence enema may be indicated alone for neurogenic bowel. Patient selection is important.

Adult↗
PubMed1998

Demand management: another marketing tool or a way to quality care?

Demand management tools are population-based strategies used to control costs and improve utilization of services by assisting health consumers in maintaining their health and seeking appropriate health care. These tools are increasingly used by health care delivery systems and, in the US, by fiscal intermediaries, such as insurance companies. If these tools are not properly applied, there is a clear possibility that their use may lead a reduction of health care services with no improvement in clinical, humanistic, or economic outcomes. Demand management effectiveness has not been rigorously examined by the medical industry or academia. Before adopting or purchasing demand management technologies, health care systems should examine them carefully to determine how the tools were developed and who they were intended to serve. Once implemented, careful tracking of population outcomes is as necessary with these technologies as with any other technologies that can affect health care.

Cost Control↗
PubMed1997

Renin-angiotensin system genes in kidney development.

The renin-angiotensin system (RAS) plays a key role in cardiovascular homeostasis through the interactions of angiotensin II with its receptors. All components of the RAS are developmentally regulated in the kidney. The functions of the system in the maturing kidney overlap those of the adult, but higher levels of expression and novel locations of expression in the fetus suggest that the RAS has alternate functions as well. Increasing evidence suggests that the RAS may regulate renal growth and development by initiating a complex cascade of events, involving growth factors and proto-oncogenes and other unidentified factors. These same cascades may also be important in renal disease states. Recent advances in the field of molecular and cell biology are providing new tools and strategies to elucidate the intimate mechanism whereby the RAS regulates growth processes and disease states.

Angiotensinogen↗
PubMed1997

Evaluation of recurrent thrombosis and hypercoagulability.

The primary mechanisms for coagulation were described more than a century ago. However, inherited disorders of coagulation have been recognized for only a few decades. Activated protein C resistance and other related protein defects account for many cases of hypercoagulability. Primary care physicians can initiate testing in individuals for whom there is a high degree of suspicion. Testing for specific disorders is best performed before initiation of anticoagulant therapy. Management often includes long-term warfarin therapy following initial anticoagulation with heparin.

Humans↗
PubMed1997

Dietary and environmental reconstruction with stable isotope analyses of herbivore tooth enamel from the Miocene locality of Fort Ternan, Kenya.

Tooth enamel of nine Middle Miocene mammalian herbivores from Fort Ternan, Kenya, was analyzed for delta 13C and delta 18O. The delta 18O values of the tooth enamel compared with pedogenic and diagenetic carbonate confirm the use of stable isotope analysis of fossil tooth enamel as a paleoenvironmental indicator. Furthermore, the delta 18O of tooth enamel indicates differences in water sources between some of the mammals. The delta 13C values of tooth enamel ranged from -8.6(-)-13.0/1000 which is compatible with a pure C3 diet, though the possibility of a small C4 fraction in the diet of a few of the specimens sampled is not precluded. The carbon isotopic data do not support environmental reconstructions of a Serengeti-typed wooded grassland with a significant proportion of C4 grasses. This study does not preclude the presence of C3 grasses at Fort Ternan; it is possible that C3 grasses could have had a wider geographic range if atmospheric CO2 levels were higher than the present values.

Animals↗
PubMed1997

Organization and expression of human telomere repeat binding factor genes.

The ends of mammalian chromosomes terminate in structures called telomeres. Recently a human telomere repeat binding factor (TRF1) that binds the vertebrate TTAGGG telomeric repeat in situ was isolated by Chong et al. (1). TRF1 regulates telomere length (2), which is often altered in cancer cells. To understand their genetic organization, TRF1 genes were localized to human chromosomes 13cen, 21cen, and Xq13 by analysis of human monochromosomal hybrids, and by fluorescent in situ hybridization. We also confirmed the recent localization of a human TRF1 gene to chromosome 8, and provide evidence that this locus is alternatively spliced. In contrast to the TRF1 genes on chromosomes 8 and X, the chromosomes 13 and 21 TRF1 genes contained a 60 bp deletion in the coding region. The results suggest that two distinct forms of TRF1 are expressed and that the TRF1 gene family includes at least three pseudogenes whose dispersal in the human genome may have occurred via cDNA intermediates.

Alternative Splicing↗
PubMed1997

Ureteroscopic management of ureteral calculi: electrohydraulic versus holmium:YAG lithotripsy.

PURPOSE: This study compared electrohydraulic and holmium:YAG lithotripsy for ureteral calculi. MATERIALS AND METHODS: Two cohorts of consecutive patients with ureteral calculi treated with ureteroscopic electrohydraulic or holmium:YAG lithotripsy were retrospectively compared. Electrohydraulic lithotripsy was done using a 1.9F fiber at energy settings between 50 and 100 v. Holmium:YAG lithotripsy was done using a 365 microm. fiber at energy settings of 0.6 to 1.5 J. RESULTS: A total of 23 and 47 consecutive patients underwent electrohydraulic and holmium:YAG lithotripsy, respectively. For preoperative calculi less than 15 mm. mean stone size plus or minus standard deviation was 9 +/- 3 versus 9 +/- 3 mm. (p = 0.5), mean operative time was 72 +/- 21 versus 102 +/- 38 minutes (p = 0.004), stone-free rate at the end of ureteroscopy was 65 versus 97 (p < 0.01) and 3-month stone-free rate was 94 versus 97% (p = 0.4) for electrohydraulic versus holmium:YAG lithotripsy. For preoperative calculi 15 mm. or greater stone size was 19 +/- 5 versus 19 +/- 4 mm. (p = 0.9), operative time was 159 +/- 61 versus 108 +/- 27 minutes (p = 0.01), stone-free rate at the end of ureteroscopy was 33 versus 87% (p = 0.001) and 3-month stone-free rate was 67 versus 100% (p = 0.02). Complications were not significantly different in either comparison. CONCLUSIONS: The overall likelihood that a patient would be rendered stone-free at ureteroscopy and 3 months after ureteroscopy favored holmium:YAG over electrohydraulic lithotripsy. For ureteral calculi less than 15 mm. electrohydraulic lithotripsy was more rapid than the holmium:YAG procedure but for ureteral calculi 15 mm. or greater the holmium:YAG technique was more rapid than electrohydraulic lithotripsy. The outcomes differences may have resulted from the different mechanisms of electrohydraulic and holmium:YAG lithotripsy.

Adult↗
PubMed1997

Is stereopsis effective in breaking camouflage for moving targets?

It has been suggested that breaking camouflage is one of the major functions of stereopsis (Julesz, 1971). In this study, we found that stereopsis is less effective in breaking camouflage for moving targets than for static ones. Observers were asked to detect a single dot moving on a straight trajectory amidst identical noise dots in random motion. In the three-dimensional (3D) condition, the noise dots filled a cylindrical volume 5.7 cm in height and diameter; the trajectory signal dot moved on an oblique 3D trajectory through the center of the cylinder. In the two-dimensional (2D) control condition, observers viewed one half-image of the 3D cylinder binocularly. Surprisingly, trajectory detection in the 3D condition was only slightly better than in the 2D condition. Stereoscopic tuning for motion detection was also measured with a novel target configuration in which the random motion noise was presented in two depth planes that straddled the fixation plane where the trajectory target was presented. As the disparity between the noise planes and the fixation plane was increased, trajectory detection improved, reaching a peak between 6 and 12 arcmin, and then declining to the 2D level at larger disparities, where the noise became diplopic. Similar tuning measurements were made for detecting a static pattern, a string of five aligned dots presented in the fixation plane between two planes of static noise dots. Adding disparity to the noise planes produced a far greater improvement in static detection than in motion detection, for a comparable range of disparities (1.5-12 arcmin). We speculate that the temporal characteristics of the stereo system are not well suited for responding to moving targets, with the result that stereo does not greatly enhance motion detection in noise.

Depth Perception↗
PubMed1997

Holmium:yttrium-aluminum-garnet laser cystolithotripsy of large bladder calculi.

OBJECTIVES: Patients with large bladder calculi (4 cm or larger) have traditionally been managed with open cystolithotomy. Endoscopic management with cystolitholapaxy or electrohydraulic lithotripsy risks complications. In an effort to spare patients the morbidity of open cystolithotomy, the results of holmium:yttrium-aluminum-garnet (YAG) laser cystolithotripsy for bladder calculi 4 cm or larger were reviewed. METHODS: Consecutive patients with bladder calculi of 4 cm or larger were managed with holmium:YAG laser cystolithotripsy. Laser energy was delivered using either the 365-micron end-firing fiber or the 550-micron side-firing fiber. RESULTS: Fourteen consecutive patients were managed with holmium:YAG cystolithotripsy. All patients were rendered stone free, regardless of stone composition or size. Median anesthesia time was 57 minutes. Twelve of 14 patients were discharged by the first postoperative day. The procedure times normalized for stone size (mean +/- standard deviation) for the end-firing versus the side-firing fibers were 13 +/- 6 min/cm versus 6 +/- 1 min/cm, respectively; P = 0.04. CONCLUSIONS: Holmium:YAG laser cystolithotripsy of large bladder calculi is effective, technically facile, and safe. The 550-micron side-firing fiber may be better suited for large bladder calculi compared with the 365-micron end-firing fiber. Holmium:YAG cystolithotripsy may obviate open cystolithotomy in selected patients.

Adult↗
PubMed1997

Technical efficiencies of Turkish hospitals: DEA approach.

This study uses Data Envelopment Analysis to examine the technical efficiencies of 573 Turkish acute general hospitals. Inputs of number of beds, number of primary care physicians, and number of specialists, and how they are used to produce outputs of inpatient discharges, outpatient visits, and surgical operations, are examined. Results illustrate that less than ten percent of Turkish acute general hospitals operate efficiently compared to their counterparts. Inefficient, compared to efficient hospitals, on average utilize 32% more specialists, 47% more primary care physicians, and have 119% more staffed bed capacity. They also produce on average less output. Particularly, 13% less outpatient visits, 16% inpatient hospitalization, and 57% less surgical procedures. Additionally, the validity of DEA is illustrated by comparing it to the ratio analysis method; no discernible differences in the results are found.

Acute Disease↗
PubMed1997

Mucinous adenocarcinoma arising from a suprapubic cystostomy site without bladder involvement.

Carcinoma arising from a suprapubic cystostomy site in patients with spinal cord injury has been infrequently described. In all previously reported cases, they have been squamous cell carcinomas. Our patient is a 68 year old male with T10 complete thoracic paraplegia who presented with an exophytic mass extending from his suprapubic cystostomy tract. Biopsy revealed mucinous adenocarcinoma. Carcinoma of the suprapubic cystostomy tract should be considered in those patients who present with bloody drainage and/or masses arising from the suprapubic cystostomy site.

Adenocarcinoma, Mucinous↗
PubMed1997

Differential expression of angiotensin II receptors during early renal morphogenesis.

Angiotensin II (ANG II) and its receptors, AT1 and AT2, may modulate kidney development. To define the temporal and spatial distribution of AT1 and AT2 receptors and their mRNAs during nephrogenesis, fetal, newborn, and adult rat kidneys were studied using reverse transcription-polymerase chain reaction and radioligand binding autoradiography. AT1 expression was minimal at embryonic day 14 (E14), highly expressed at E20, and persisted into adulthood. Conversely, AT2 expression was easily detected from E14 through postnatal day 7 but was undetectable by postnatal day 28. At E14, 76% of the receptors were AT2, 24% were AT1, and both were found in the undifferentiated mesenchyme. By E17, AT1 comprised 40% of the receptors and localized to mature nephron segments, whereas AT2 remained within both condensed mesenchyme and differentiating epithelia. The dissociation constants for AT1 and AT2 were 0.45 +/- 0.09 nM and 0.73 +/- 0.15 nM, respectively, at E17, similar to adult values. By E20, AT1 and AT2 colocalized to the outer medullary stripe, deep nephrons, medullary rays, and blood vessels, while AT2 continued to predominate in the actively differentiating cortex. The presence of both subtypes of receptors capable of binding ANG II during early nephrogenesis and the time-dependent and structure-specific regulation of receptor localization confirm a regulated developmental program for receptor expression and suggest important roles for AT1 and AT2 in renal morphogenesis.

Aging↗