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Biomedical subjects

L C Perry

Publications and source records attributed to L C Perry.

17 recordsLinked to original sources
PubMed1998

Tissue temperatures during ultrasound-assisted lipoplasty.

Removing excess subcutaneous fat with the assistance of ultrasonic energy has recently become a technique of interest in the United States after nearly a decade of use in Europe. There are a number of reported advantages of ultrasound-assisted lipoplasty over traditional liposuction, and there are also some theoretical concerns. Ultrasound-assisted lipoplasty involves the conversion of electrical energy to mechanical energy and transfer to the tissues through acoustic pressure waves, with the formation of heat as a by-product. Heat generated in this process dissipates through the body's own cooling mechanisms and conduction to the surrounding tissues, and it does not contribute to the clinical treatment of the adipose tissue. Reports of "burns" and ischemic skin injuries in the literature, and concerns for potential heat-related problems, prompted us to investigate whether significant temperature elevations occur in the clinical setting. Subcutaneous tissue temperature determinations during ultrasound-assisted lipoplasty were begun in February of 1996, and data were collected from 55 patients who had the procedure performed during a 6-month period. Intraoperatively, temperature measurements were made with a data-logging instrument and a needle microprobe inserted into the subcutaneous tissues. Temperatures were taken in the area of liposuction before the infusion of tumescent fluid, after tumescent fluid infusion, and at 5-minute intervals until the end of the procedure. The patient's core body temperature remained stable during the procedure within a narrow range (35.7 degrees C to 36.3 degrees C). There was a gradual increase in the temperature of the subcutaneous tissues over time during the application of ultrasonic energy; however, average subcutaneous temperatures remained below the core temperature (p < 0.05) at all time intervals. Room-temperature tumescent fluid further enhanced the thermal safety zone without lowering core body temperature. There were no temperature related complications in our study population and no untoward effects of performing temperature measurements. We conclude that there is no clinically significant elevation of subcutaneous temperatures during ultrasound-assisted lipoplasty. Reported ischemic skin complications are more likely the result of injury to the subdermal plexus rather than a temperature-induced thermal injury. Although heat is a natural by-product of the energy transfer involved in ultrasound-assisted lipoplasty, the risk of thermal injury is negligible when the procedure is performed by experienced operators. Complete understanding of the technique along with strict adherence to basic principles of flap vascularity will ensure safe and effective performance of ultrasound-assisted lipoplasty.

Adult↗
PubMed1995

Evaluation of silicone-gel sheeting on early wound healing of linear incisions.

Topical silicone-gel sheeting has been shown to be beneficial in the treatment of established hypertrophic and keloid scars. Certain individuals and incisions in specific body sites appear to be at increased risk for the development of such scars. A simple, inexpensive, and preventive treatment in these individuals at increased risk could potentially minimize the extended period of pressure therapy and repeated steroid injections that are often required to optimize outcome. However, the effects of applying silicone-gel sheeting in the immediate postoperative period as a preventive measure have not been investigated to date. Because silicone-gel sheeting influences the remodeling and maturation phase of collagen formation, we believed it prudent to determine whether silicone-gel sheeting had any deleterious effect on early wound healing, as demonstrated by in vivo biomechanical testing of wound strength and histological assessment. To investigate the potential effects of silicone-gel sheeting on acute wound healing and its possible application for prevention of hypertrophic scars, a study was designed in the hairless guinea pig. In phase 1 of the study, bilateral dorsolateral incisions were made, allowing each guinea pig to serve as its own control. One wound was dressed with silicone-gel sheeting, and the control site was dressed with Nu-gauze dressing. Wounds were then assessed visually and with in vivo biomechanical analysis of wound strength at days 3, 5, and 7 postoperatively (n = 7 per group). Phase 2 of the study compared identical dressings in a similar animal model using a single dorsal midline incision, in which alternate halves of each wound served as the control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

A rat transverse rectus abdominis musculocutaneous flap model: effects of pharmacological manipulation.

A study was designed to attempt to develop an experimental animal model for the transverse rectus abdominis musculocutaneous (TRAM) flap. The rat has a well-formed superior epigastric artery with musculocutaneous perforators that have been shown to support a musculocutaneous flap on a single superior pedicle. Despite the anatomical differences between the dominance of the axial longitudinal cutaneous circulation in loose-skinned animals compared with humans, as well as a dominant superior intramuscular pedicle, the rat TRAM model appears to be reproducible and has predictable zones of viability as well as areas that typically do not survive when based on a single superior pedicle. These areas of nonviability correspond to those zones at high risk of nonviability in the human clinical situation: zone 3 and 4 on the contralateral side and zone 3 on the ipsilateral side (tissue lateral to the superficial inferior epigastric supply). Once the reliability and reproducibility of this model was demonstrated (coefficient of variation 18.9%), a study was undertaken to determine whether pharmacological manipulation of this flap altered survival in those areas that are inadequately perfused. The two agents tested were allopurinol (xanthine oxidase inhibitor, antioxidant) and pentoxifylline (microcirculatory rheological agents that is a xanthine analogue and is also believed to have antioxidant potential). The study involved creating right unipedicled TRAM flaps in 30 male specific pathogen-free Sprague-Dawley rats weighing 375 to 450 gm. The transverse skin paddle was centered over the umbilical dimple and measured 5.5 x 2 cm.(ABSTRACT TRUNCATED AT 250 WORDS)

Allopurinol↗
PubMed1994

A rat model for capsular contracture: the effects of surface texturing.

There has been ongoing clinical and laboratory research to determine the role of surface morphology on capsular contracture. The purpose of this study was to develop a rat model in which capsular contracture occurred frequently and to determine whether surface texturing had any effect on the incidence or degree of capsular contracture as determined by in vivo biomechanical analysis of tissue modulus and histological examination of the tissue at the capsule-implant interface. A new sublatissimus implantation site in the rat was developed in an attempt to avoid subpannicular placement, which has been associated with inconsistent results because of contracture despite texturing, and a high rate of implant exposure secondary to trauma. Each rat (N = 43) was implanted with two devices--one smooth-surface 6-ml implant and one textured Biocell 6-ml implant--both with remote ports to allow for biomechanical analysis. Evaluation was carried out at 1, 2, and 3 months (n = 10) and 6 months (n = 5). Biomechanical evaluation of the implants was carried out in vivo and anonymously. The animals were then killed, and sectioning of the overlying capsule-implant interface from the dome of the implant was performed. Histological evaluation was carried out anonymously with regards to the implant type. Capsular contracture developed in smooth-surface devices in 95% of sites; this became evident on biomechanical analysis at 2 months and progressed to 3 months, after which it remained relatively stable.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Role of transforming growth factor-beta and epidermal growth factor in the wound-healing process: an in vivo biomechanical evaluation.

The purpose of this study was to assess and evaluate the role of transforming growth factor-beta(1), epidermal growth factor, and their respective carriers (collagen and liposomes) in the early phases of the wound-healing process in linear incision wounds; we used an in vivo biomechanical testing system. One hundred twenty specific pathogen-free male Sprague-Dawley rats were divided into five experimental groups (n = 24), including one group receiving no treatment at all. Each animal received one abdominal midline incision. At 3 and 5 days after wounding, 12 animals per group were randomly selected for in vivo biomechanical evaluation. Specimens were also randomly obtained from nondisrupted tissues for histologic analysis. Statistical analysis comparing groups revealed that transforming growth factor-beta(1) significantly increased wound strength at day 5, and liposomes decreased wound strength at day 3. There were no other significant differences among groups for each of the time intervals studied. Our results suggest that in vivo biomechanical evaluation of tissue response to injury and treatments will add new dimension to future studies of skin and wound healing.

Journal Article↗
PubMed1993

Morphologic analysis of tissue-expander shape using a biomechanical model.

Using a biomechanical model designed to reproduce the forces exerted by the soft tissues of the chest wall, the contours created by several currently available round as well as anatomically shaped tissue expanders were evaluated. Parameters that describe expander shape were defined, the most useful of which proved to be the point of maximal projection and the percentage of upper pole deformity. Direct comparison of seven different expanders with respect to these variables revealed the anatomically shaped expanders to offer improved contours over traditional round designs. Continuing modifications in expander design should focus on lowering the point of maximal projection and minimizing the upper pole deformity.

Biomechanical Phenomena↗
PubMed1992

An improved method of in vivo wound disruption and measurement.

Biomechanical studies of wound strength are important because of new investigations in growth factors, cytokines, and fetal wounds. We compared two traditional methods of wound disruption measurement with a novel computerized model designed for in vivo experiments. An Instron tensiometer (INSTS) and an air insufflated positive pressure device (AIPPD) were compared with a vacuum-controlled wound chamber device (VCWCD). The VCWCD produced vacuum at the wound site and wound disruption was monitored with two video camera/recorders. Rats were marked with a template guide for a 2.5 cm, full-thickness, abdominal incisional wound. Rats were divided into three groups and studied at 2, 7, or 14 days after wounding. The recorded images were computer digitalized to generate wound strength curves from a three-dimensional model. A comparison of the wound disruption curves demonstrated that the VCWCD was comparable to the INST or AIPPD in normal wound healing (P greater than .40). The VCWCD provided data with less standard error at 2 days after wounding (P less than 05). In separate series of experiments, VCWCD was tested in the early phases of healing and was found to be sensitive to change at intervals of 48 hr after wounding (P less than .005). The INST or AIPPD methods could not perform this task because of an unacceptable level of random error after tissue manipulation. The VCWCD system was considered superior for evaluating early wound healing because it was an in vivo method which required minimal wound manipulation.

Animals↗
PubMed1990

Peers' perceptions of the consequences that victimized children provide aggressors.

Fourth- through seventh-grade children (mean age 11.5 years) estimated the likelihood that various consequences would occur following hypothetical acts of aggression toward victimized and nonvictimized classmates. Children also indicated how much they would care if the consequences were to occur. When contemplating aggression toward victimized classmates, children were more likely to expect tangible rewards, more likely to expect signs of victim suffering, and less likely to expect retaliation than when considering aggression against nonvictimized classmates. Also, when considering aggression toward victimized classmates, children cared more about securing tangible rewards but were less disturbed by the thought of hurting their victims or by the thought of their victims retaliating than when imagining aggression toward nonvictimized classmates. The foregoing pattern was stronger for boys than for girls. Implications for theories of aggression and for intervention with aggressive and victimized children are discussed.

Aggression↗
PubMed1986

Cognitive social learning mediators of aggression.

This research explored links between aggression in elementary school children and 2 classes of social cognitions that might influence children's decisions about whether to behave aggressively. Aggressive and nonaggressive children (mean age 11.3 years) responded to 2 questionnaires. One questionnaire measured children's perceptions of their abilities to perform aggression and related behaviors (perceptions of self-efficacy), and the other measured children's beliefs about the reinforcing and punishing consequences of aggression (response-outcome expectancies). Compared to nonaggressive children, aggressive subjects reported that it is easier to perform aggression and more difficult to inhibit aggressive impulses. Aggressive children also were more confident that aggression would produce tangible rewards and would reduce aversive treatment by others. There were negligible sex differences in perceived self-efficacy for aggression but large sex differences in anticipated social and personal consequences for aggression, with girls expecting aggression to cause more suffering in the victim and to be punished more severely by the peer group and by the self. It was concluded that children's knowledge of their capabilities and children's knowledge of the consequences of their actions are factors that need to be taken into account by cognitive models of aggression.

Aggression↗
PubMed1979

Interactive effects of cognitive involvement and response topography upon differential eyelid conditioning to conceptual discriminanda.

The purpose of the experiment was to determine some cognitive differences underlying the superior differential conditioning of voluntary-form (V) over conditioned-form (C) responders. Two cognitive activities were hypothesized to be jointly necessary for the superiority of Vs: first, an active development of reinforcement contingency awareness by the subject himself, and, second, an active use of acquired contingency knowledge in predicting UCS occurrences. The first variable was manipulated by asking half of the subjects to "figure out" the contingencies, while the other half were fully informed of them at the start. The second variable was assessed by requiring half of the subjects to engage in a button-pressing US prediction task on each trial. Conditioned discrimination indicated that, as predicted, both of these cognitive activities were required for good performance by Cs, supporting the hypothesis that Cs are normally deficient in these respects. An unpredicted deterioration in discrimination for Vs when both task manipulations were imposed suggested that competition between the Vs' spontaneous cognitive activities and the experimentally imposed ones developed in the high external demand situation.

Awareness↗