Biomedical subjects

C Cox

Publications and source records attributed to C Cox.

548 records · Page 31Linked to original sources

PubMedDate not supplied

Corneal sensation following excimer laser photorefractive keratectomy in humans.

BACKGROUND: For the correction of myopia, small amounts of corneal tissue--including corneal nerves--are removed, resulting in flattening of the central cornea. METHODS: We studied the changes in corneal sensation in five regions of the cornea following photorefractive keratectomy at varying depths. We examined and compared the recovery of sensation in 17 sighted myopic eyes, with preoperative refractive ranges from -1.00 to -7.25 D. Eyes were divided into shallow (0 to 30 microns) or deep (31 to 70 microns) ablation groups depending on the attempted laser correction. Corneal sensation was measured in the central ablated area and the temporal, inferior, nasal, and superior unablated regions preoperatively and at 1, 3, and 6 months postoperatively. RESULTS: Central and inferior sensation were significantly reduced in the deep ablations at 1 month and continued in the central cornea 6 months postoperatively. There were no overall differences in the sensations in the unablated nasal, temporal, and superior regions between either group or over time. There was a significant second order trend (p = .034) in these three regions, indicating a sharper increase in sensation from baseline in the deeper group at 1 month than the gradual upward trend of the shallow group. CONCLUSIONS: Corneal sensation of both the central ablated area and the unablated peripheral cornea is decreased after deep anterior stromal excimer laser ablations and does not recover within 1 month. Although the deeper group showed isolated areas in the periphery of significant second order trends in sensation, the overall trends were not large, indicating no significant anesthetic effect. Fluctuations in sensation can be detected in the five regions even 6 months after excimer laser keratectomy. The clinical importance of these data remain to be defined.

Adult↗

PubMedDate not supplied

Differential responses of human sperm to varying concentrations of pentoxyfylline with demonstration of toxicity.

Pentoxyfylline (PF), a methylxanthine derivative, is an inhibitor of the cAMP-phosphodiesterase enzyme, and is known to stimulate the motility of fresh and post-thaw human sperm. The purpose of this study was to examine the effects of different concentrations of PF on motility (MOT), path (curvilinear) velocity (PV), and hyperactivation (HA) of fresh sperm from patients (n = 24) and donors (n = 6) and post-thaw donor sperm (n = 5). For cryopreservation, the donor semen was frozen in liquid nitrogen using test-yolk-glycerol cryopreservative, stored for a minimum of 48 hours, then thawed at room temperature prior to assay. Aliquots of all samples to equal 10 x 10(6)/ml were diluted in 1 ml of the following: medium (human tubal fluid) only (control), or 2.5, 5, 10, or 20 mg/ml PF in medium. Specimens were incubated at 37 degrees C, and all were assessed by computer-assisted motion analysis at 0, 0.5, 1, and 2 hours. The patient specimens were divided into two groups: group 1, mean percent (standard deviation [SD]) MOT < 20% (12.8 +/- 5.8); group 2, mean percent (SD) MOT > 20% (37.8 +/- 14). For fresh donor sperm, 2.5 mg/ml PF significantly stimulated PV and HA at 0, 1, and 2 hours, and MOT at 0, 0.5, and 2 hours. PF at 5 mg/ml resulted in a decreased PV and HA, whereas MOT was decreased by 10 mg/ml. In the < 20% MOT group, 2.5 mg/ml PF significantly stimulated MOT at 0.5, 1, and 2 hours, and HA at 0 and 2 hours. There was no effect on PV.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMedDate not supplied

Public cholesterol screening in the previously diagnosed: misuse of resources or beneficial function?

The attendance of individuals with a previous diagnosis of hyperlipidemia at public cholesterol screenings is often criticized as a misuse of such programs. This study explored the post-screening actions of 811 participants in a cholesterol screening program who had previously been diagnosed with cholesterol elevations and whose blood levels at this screening required further medical referral. We also studied the responses of physicians from whom these subjects sought care. Within five months, 559 of 753 participants completing the survey (74.0%) sought medical follow-up. Physicians retested the blood cholesterol levels of 75.0% of these 559; high-risk screenees were more likely to be retested and to be informed that their levels were elevated than moderate-risk subjects (P < .0001). Physicians increased cholesterol-lowering dietary advice for high-risk subjects (P < .0001) and medication prescriptions for both risk groups (P < .0001). Participants seeking medical care after the screening program had better cholesterol-lowering dietary practices and reported increased regimen compliance (moderate-risk: P = .01; high-risk: P < .0001) than those individuals not obtaining medical follow-up. One year after screening, blood cholesterol levels were 4.5% lower (P = .001) in those complying with referral but were virtually unchanged in noncompliers. Screening program confirmation of high blood cholesterol levels combined with referral appeared to have a positive impact on previously diagnosed screenees. We conclude that there may be merit in including previously diagnosed individuals in cholesterol screening programs.

Adult↗

PubMedDate not supplied

Functional implications of postural disequilibrium due to lead exposure.

Measurement of postural equilibrium has been employed as an indirect indicator of functional status of the nervous systems of 109 children (mean age: 5.8 +/- 0.78 years) from the Cincinnati Lead Program Project. The geometric mean blood lead for the first five years of life (PbB05) was 11.9 +/- 1.5 micrograms/dL. Postural sway associated with upright balance was noninvasively quantitated with a microprocessor-based force platform and four tasks performed for 30 sec each by the subjects. A covariate-adjusted multiple regression analysis showed statistically significant associations between PbB05 and the postural sway for the task requiring primarily vestibular and/or proprioceptive systems input, implying potential functional impairment. These findings raised several new issues which are addressed here: (1) A dynamic task has been developed to further test the effect of perturbing those afferents' functional capabilities. (2) A method has been developed to quantitate the stability boundary of each subject to better characterize the limits of functionally-safe postural sway. (3) There is a need to perform the postural sway in a shorter duration than 30 sec so that children younger than five years of age can be tested for early identification of Pb-induced functional impairment of postural equilibrium.

Child↗

PubMedDate not supplied

The effects of lead exposure on learning in a multiple repeated acquisition and performance schedule.

This study sought to determine the selectivity of Pb-induced changes in learning, as distinct from non-specific or performance effects, and to explore the nature of the underlying error patterns contributing to any learning deficits. To accomplish this, rats were chronically exposed to 0, 50, or 250 ppm Pb acetate in drinking water from weaning and trained on a multiple repeated acquisition (RA) and performance (P) schedule beginning at 55 days of age. The RA component required the rat to learn a new 3-member sequence of responses during each experimental session (Center Right Left, RLC, CLR, RCL, and LRC), while the correct sequence of responses for the P component was constant across sessions (LCR). Significant decrements in accuracy on the RA component but not on the P component were found in Pb-exposed groups compared to control, effects that could not be attributed to differential rates of responding. Analyses of error patterns revealed that the effects of Pb exposure on RA accuracy levels derived from two sources. The first consisted of a perseveration of P-like sequence responding (LCR) even during the RA component. Secondly, Pb exposure increased perseverative responding on a single lever, even though the schedule itself never directly reinforced such repetitive responding. The increase in frequency of these two types of perseverative behavior was incompatible with acquisition of non P-like sequences during the RA component. Adding a 5 sec tone to the light stimuli signalling the transition between RA and P components of the multiple schedule failed to attenuate these effects of Pb, suggesting that deficits in stimulus control were not the sole behavioral mechanism of these impairments. Examination of individual data revealed the presence of both 'learners' and 'non-learners' in each group, with the prevalence of the latter being suggestively higher in Pb-exposed groups than in controls. These findings may be relevant to the classroom setting, where periods requiring learning may frequently be interspersed with periods of performance of learned skills.

Animals↗

PubMedDate not supplied

Computer database for melanoma: a clinical management and research tool to ensure continuous quality assessment.

The need for an efficient method to handle data and for chart documentation is more apparent today than at any time in the past. High volume clinics for screening, diagnosis, and treatment are the rule rather than the exception in modern practice. A papermill medical record department or tumor registry fails on a day-to-day basis because of inefficiency of data collection, filing, storage, and abstraction. Requirements of the Joint Commission for the Accreditation of Health Care Organizations (JCAHO) include the setting of standards and the ability to query data to ensure the standards are met. A PC-based software program has been developed with the following features: (1) ongoing timed queries of the data are possible on any variable collected in the database to monitor trends in the standards established for care in the clinic; (2) a daily update of the database is performed so that it may be used as a clinical management tool, acting as an electronic medical record or as a clinical research tool; (3) the software will summarize the chart by abstracting a predetermined list of key data elements to improve clinical efficiency; (4) chart documentation is improved for Medicare coding requirements to maximize physician reimbursement; and (5) clinic notes and referral letters are generated the same day as the clinic visit to allow patients to have a copy of their clinic notes or for same day FAXing to the referring doctors. To date, > 1,200 patients with melanoma have been registered and entered into the system.(ABSTRACT TRUNCATED AT 250 WORDS)

Databases, Factual↗

PubMedDate not supplied

Oxygen delivery with a single cannula tidal flow venovenous system for extracorporeal membrane oxygenation.

Venovenous tidal flow perfusion for extracorporeal membrane oxygenation via a single lumen cannula in the right atrium avoids the sacrifice of a carotid artery inherent in venoarterial systems, and eliminates the problems of two cannula venovenous perfusion. Oxygen delivery and hemodynamic effects of a single cannula, single lumen system with tidal flows directed by alternating tubing occluders were studied in six newborn lambs to define optimal system performance and possible adverse hemodynamic effects. The ratio of drainage to infusion time was fixed at 2:1 to avoid excessive reinfusion pressures. Total length of the in/out cycle was varied from 2-6 sec, resulting in a cycling frequency of 30 to 10 cycles/min and a tidal volume of 17-50 ml. Systemic arterial, mixed venous, and pre and post oxygenator partial pressure of oxygen and oxygen saturation were measured. Recirculation, oxygen delivery, and effective bypass flow (total flow--recirculated flow) were calculated. With slower cycling frequency, recirculation progressively fell, and effective flow and oxygen delivery increased (p < 0.001 for each parameter across the cycle length). In these animals, oxygen delivery was limited by low oxygen carrying capacity (mean hemoglobin, 8.1 g/dl). The authors concluded that with longer cycles, the system minimizes recirculation without apparent adverse hemodynamic consequences, achieving sufficient effective bypass flow to assure adequate oxygen delivery when hemoglobin levels are normal.

Animals↗

PubMedDate not supplied

The legacy of Allitt.

Since nurse Beverly Allitt's Munchausen's syndrome by proxy led her to kill children in her care, recruiting managers have been wary of mental illness. Now it is time for a more positive approach, say Sheelagh Brewer and Chris Cox.

Adult↗