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Biomedical subjects

S T Charles

Publications and source records attributed to S T Charles.

18 recordsLinked to original sources
PubMed2001

Age-related differences and change in positive and negative affect over 23 years.

Positive and negative affect, measured by the Bradburn Affect Balance Scale, were studied in a longitudinal sample spanning from 1971 to 1994. The sample (N = 2,804) represented 4 generations of families. Linear trend analyses compared generations over time for positive and negative affect and also examined the possible influences of neuroticism and extraversion on initial levels of affect and patterns of change in affect. Negative affect decreased with age for all generations, although the rate was attenuated among the oldest adults. Higher neuroticism scores also attenuated the decrease in negative affect across time. For positive affect, the younger and middle-aged adults showed marked stability, but the older group evidenced a small decrease over time. Higher levels of extraversion were related to more stability in positive affect.

Adolescent↗
PubMed1999

Taking time seriously. A theory of socioemotional selectivity.

Socioemotional selectivity theory claims that the perception of time plays a fundamental role in the selection and pursuit of social goals. According to the theory, social motives fall into 1 of 2 general categories--those related to the acquisition of knowledge and those related to the regulation of emotion. When time is perceived as open-ended, knowledge-related goals are prioritized. In contrast, when time is perceived as limited, emotional goals assume primacy. The inextricable association between time left in life and chronological age ensures age-related differences in social goals. Nonetheless, the authors show that the perception of time is malleable, and social goals change in both younger and older people when time constraints are imposed. The authors argue that time perception is integral to human motivation and suggest potential implications for multiple subdisciplines and research interests in social, developmental, cultural, cognitive, and clinical psychology.

Adult↗
PubMed1999

Genetic and behavioral risk factors for self-reported joint pain among a population-based sample of Swedish twins.

Self-reported joint pain, a typical manifestation of osteoarthritis, was examined using 335 twin pairs from the Swedish Adoption/Twin Study of Aging to estimate relative genetic and environmental influences on self-reported joint pain and to examine the relationships between joint pain, health behavior, and psychological variables. Findings suggest that family resemblance for self-reported joint pain represents similar environments more than genetic similarity. Data from the early 1970s, including exercise, physical activity at work, obesity, and neuroticism, were used to predict joint pain in 1993. For men, moderate amounts of exercise decreased the likelihood of joint pain, but strenuous amounts of physical activity in the workplace had the opposite effect. For women, exercise and physical activity were not significant predictors, but past obesity and higher levels of neuroticism increased the likelihood of reporting joint pain in 1993.

Aged↗
PubMed1998

Vascular endothelial growth factor increases release of gelatinase A and decreases release of tissue inhibitor of metalloproteinases by microvascular endothelial cells in vitro.

The present study was designed to determine the influences of vascular endothelial growth factor (VEGF) on cell proliferation and the release of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) from human dermal microvascular endothelial cells. Treatment of cultures with 10 ng/ml or more of VEGF significantly increased cell proliferation. The effect of VEGF treatment on the levels of specific MMPs and TIMPs in the media was subsequently examined in cultures that were treated with 10 ng/ml VEGF. Zymography and Western blot analyses demonstrated that gelatinase A levels in the media were increased by VEGF treatment. Collagenase was detected by Western blots in both VEGF-treated and untreated culture media, but the levels were not significantly increased by the VEGF treatment. An ELISA assay confirmed that VEGF treatment significantly increased gelatinase A levels but did not significantly increase collagenase levels. Western blot and ELISA data showed that VEGF treatment significantly decreased TIMP-1 and TIMP-2 levels compared to untreated cultures. The data suggest that VEGF may modulate endothelial cell-derived MMP activity by: (1) increasing the abundance of gelatinase A; (2) disinhibiting gelatinase A by decreasing the abundance of TIMP-2; and (3) disinhibiting preexisting collagenase by reducing levels of TIMP-1. These actions could contribute to the ability of VEGF to promote endothelial cell invasion of new territory.

Cell Division↗
PubMed1997

Micro-telerobotic surgical system for microsurgery.

Modern surgical methods which utilize microscopes have allowed medical professionals to visualize the surgical field on the order of microns. This new found visual capacity has created a performance gap between a surgeon's visual skills and manipulative skills that surgical robotics have the capability to remedy. Robotics can be used as an aid to the surgeon to help correct natural human dexterity problems such as tremor and resolution of motion. Devices that would benefit surgical dexterity at the micron scale are in development at Sandia National Laboratories. A six degree-of-freedom (DOF) force reflecting telerobotic manipulator has been designed and developed for use in microsurgical applications. The system utilizes a unique mechanical platform, actuation schemes, and controller that provides high positional precision while maintaining high frequency response for implementation of force feedback. Thus, the same device is used to form a master-slave telerobotic arrangement to assist the surgeon. This makes the system very intuitive to the surgeon and easier to implement for the engineer. The system utilizes high performance Digital Signal Processors (DSP) for control of both the master and slave platforms. Six dimensional force information is obtained from transducers located at the end effectors of both the master and slave. Two distinctly different types of motors are currently being evaluated, as well as several types of control algorithms. Position scaling, force scaling, and tremor filtering are being implemented in the DSP control software. Control parameters are based upon system frequency response testing. Results from our system identification and performance testing will be discussed.

Computers↗
PubMed1997

Visual results after submacular surgery for neovascularization in age-related macular degeneration.

BACKGROUND AND OBJECTIVE: Submacular membranectomy has been proposed as a treatment option for subfoveal choroidal neovascular membranes (CNVMs). The authors reviewed the visual outcomes of patients who underwent surgical removal of subfoveal CNVMs caused by age-related macular degeneration (ARMD). PATIENTS AND METHODS: Thirty-eight patients (38 eyes) were retrospectively reviewed. Selection criteria included: (1) the presence of a well-demarcated subfoveal CNVM on fluorescein angiography; (2) best-corrected Snellen visual acuity reduced to the level of 20/200 or worse; and (3) no other eye disease that could compromise visual acuity. Pars plana vitrectomy, retinotomy, and membrane removal were performed to remove the subfoveal choroidal neovascular complex with minimal disruption of the surrounding tissues. A significant change was defined as a two-line difference from best-corrected preoperative visual acuity on the Snellen chart. RESULTS: At 3 months postoperatively, 7 (18.4%) of the 38 eyes had improved, 8 (21.1%) of the eyes had worsened, and 23 (60.5%) of the eyes had remained unchanged. The final visual acuity improved in 8 (21.1%) of the eyes, worsened in 11 (28.9%) of the eyes, and remained unchanged in 19 (50%) of the eyes. The average follow-up time was 632 days. CONCLUSIONS: The authors employed a minimally invasive approach to the removal of CNVMs in ARMD. Nevertheless, the resultant visual acuity was often unsatisfactory. Therefore, the authors recommend not operating on ARMD-associated subfoveal CNVMs with the current technology.

Aged↗
PubMed1992

Diode laser photocoagulation for prethreshold, posterior retinopathy of prematurity.

Nine infants with posterior retinopathy of prematurity were treated by using the diode laser through an indirect ophthalmoscopic delivery system. Treatment was commenced as soon as plus disease (defined as tortuosity and dilation of posterior vessels) developed. We defined posterior retinopathy of prematurity as retinopathy of prematurity located in zone 1 (the limits of zone 1 are defined as twice the disk-fovea distance in all directions from the optic disk, that is, an arc of 60 degrees centered on the optic disk) or the posterior one half of zone 2 (zone 2 extends from the edge of zone 1 peripherally to a point tangential to the nasal ora serrata and around to an area near the temporal anatomic equator). Disease regressed in all eyes. These results are encouraging and represent an improvement over the results obtained by allowing these eyes to reach threshold (threshold disease is defined as 5 or more contiguous or 8 total clock hours of neovascularization in zone 1 or 2 in the presence of plus disease) before intervention.

Female↗
PubMed1988

Interphotoreceptor retinoid-binding protein levels in subretinal fluid from rhegmatogenous retinal detachment and retinopathy of prematurity.

Interphotoreceptor retinoid-binding protein (IRBP) has been detected qualitatively in subretinal fluid associated with rhegmatogenous retinal detachments. We have used a quantitative enzyme-linked immunosorbent assay to determine the IRBP concentrations in 24 fluid specimens collected at retinal reattachment surgery from 22 patients, and from 17 patients who underwent surgery for retinopathy of prematurity with traction detachment. We observed a wide range of concentrations (1 to 176 micrograms of IRBP per milligram of protein). Higher concentrations were found only in fluid from the more recent rhegmatogenous detachments. The lowest concentrations were detected among fluids drained from under rhegmatogenous detachments ranging from five days' to one year's duration. The IRBP concentration in subretinal fluid showed no correlation with visual outcome and may be influenced by IRBP turnover in the vitreous cavity. Most strikingly, none of the 17 samples from patients with retinopathy of prematurity contained detectable amounts of IRBP.

Adult↗
PubMed1987

Thrombin infusion to control bleeding during vitrectomy for stage V retinopathy of prematurity.

We prospectively studied 36 consecutive premature infants with the diagnosis of retinopathy of prematurity stage V with total traction retinal detachment who underwent lensectomy/vitrectomy and epiretinal membrane delamination. The first 26 patients underwent vitrectomy using thrombin mixed with Balanced Salt Solution Plus at a concentration of 100 U/mL and the remaining ten patients had pure Balanced Salt Solution Plus used. Intraoperative and postoperative bleeding were monitored. The overall intraoperative bleeding rate was 92% (33/36). Intraoperative bleeding (19% vs 80%) and bleeding at the time of wound closure (4% vs 30%) were both significantly reduced in the thrombin vs no thrombin group.

Eye↗
PubMed1987

Surgical instrumentation cart.

We describe the design of a surgical equipment/instrumentation cart that provides accessibility, mobility, convenience, conservation of floor space, and efficient use of vertical air space. This multiple-shelf cart allows organization and coordination of multiple pieces of equipment. The attached working shelves replace the multiple Mayo stands and free up needed floor space. This cart provides for easy storage and unnecessary movement of equipment and potential damage. The power strips on the rear of the cart eliminate the multiple electrical cords and potential injury to operating personnel and equipment malfunction.

Ophthalmology↗