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Biomedical subjects

R G Tompkins

Publications and source records attributed to R G Tompkins.

At least 181 records · Page 10Linked to original sources
PubMedDate not supplied

Rapid quantitation of recombinant retroviruses.

A method for measuring the concentration of recombinant retrovirus encoding the Escherichia coli LacZ gene is described. The assay is based on the quantitative measurement of beta-galactosidase activity in extracts of cells infected with the LacZ-encoding retrovirus. LacZ-encoded beta-galactosidase activity in transduced cells is measured using the colorimetric substrate, o-nitrophenyl beta-D-galactopyranoside (ONPG), and the results are read using an ELISA plate-reader. Because the entire assay is performed in a 96-well plate, large numbers of samples are easily measured, and the assay has the advantages of rapidity, precision, and ease of data collection. The assay was used to determine the optimal concentration of polybrene, a polycation known to enhance the infectivity of retroviruses, and can be used to evaluate other factors that affect infection, as well as the optimal conditions for production of the recombinant retrovirus.

3T3 Cells↗
PubMedDate not supplied

Hepatocytes from rat liver perfusions. Physicochemical effects on polyribosome size.

Hepatocytes have been used extensively both in vitro and in vivo for a wide variety of studies. Although isolated hepatocytes appear similar to their in vivo counterparts, they are different in some respects. One aspect in which they differ is their ability to translate proteins. The isolation process appears to inflict sufficient damage to reduce the average polyribosome size within the isolated hepatocytes and this size reduction correlates with a lower rate of protein production. Two methods of liver perfusion that better maintain the normal distribution of polyribosomes are described in this report. It is clear from these studies that new isolation methods that result in high yields of viable hepatocytes that function maximally are needed.

Animals↗
PubMedDate not supplied

Evaluation of acellular human dermis as a dermal analog in a composite skin graft.

This study evaluated the structure and function of a dermal substitute composed of de-epidermalized, acellular human dermis, and tested its performance as part of a composite skin graft with cultured human keratinocytes. The acellular dermis retained much of the complex structure of native dermis, as demonstrated by immunostaining for collagen Types IV and VII. Collagen Types IV and VII were found on the papillary surface, and collagen Type IV was found at sites throughout the acellular dermis. To further demonstrate the functionality of the acellular dermis material, we seeded the papillary surface with cultured keratinocytes. In response to the architecture of the dermal papillae, the keratinocytes formed a three-dimensional epidermal structure that was several cell layers thick, and recreated the original skin rete ridges at the interface with the dermis. When these composite grafts were transplanted to athymic mice, host fibrovascular cells repopulated the acellular dermis. Some vessels grew into the acellular dermis along the original pathways of the human blood vessels, as demonstrated by co-localization of human and mouse collagen Type IV. The skin that developed from these grafts repigmented completely via passenger melanocytes from the keratinocyte cultures, was durable, and remained stable for more than 5 months.

Animals↗
PubMedDate not supplied

Hepatic and intestinal blood flow following thermal injury.

Because cardiac output decreases after burn injuries, investigators have assumed, based upon dye clearance techniques, that hepatic and intestinal blood flow are also decreased following these injuries. Blood flow to the liver, stomach, small intestine, and kidney was determined by the uptake of 201thallium and 125I-labeled fatty acid (para-125I-phenyl-3-methyl pentanoic acid) in a 20% body surface area scald injury that also included plasma volume replacement resuscitation. Uptake of these radioisotopes was determined 15 minutes, 18 hours, and 72 hours after injury. The uptake of the 201thallium and 125I-labeled fatty acid by the gastrointestinal tissues was not statistically different at any of the time periods after comparison of the injured and control (sham-treated) animals. 201Thallium uptake by the kidney was significantly diminished 15 minutes after the burn injury (P less than 0.01). Based on these blood flow measurement techniques, the data suggest that the 20% body surface area scald injury did not alter blood flow to the liver or gastrointestinal tract within the initial 72 hours after the burn injury even though a decrease in renal blood flow was easily detected. These results suggest that the dysfunction of the gastrointestinal system or hepatic system observed after an acute burn injury is not simply the result of hypovolemic shock, which reduces both renal and mesenteric blood flow. These gastrointestinal and hepatic alterations may be related to a factor or factors other than intestinal ischemia.

Animals↗
PubMedDate not supplied

Core body temperature responses immediately after cutaneous thermal injury in rats.

Internal temperatures were continuously measured in rats that received 20% or 40% body surface area cutaneous scald injuries in 25 degrees C and 38.5 degrees C environments. In animals that received thermal injuries in the 25 degrees C environment, intraperitoneal, intraesophageal, and intrarectal temperatures rapidly rose to 40 degrees C within 5 minutes but returned to normal values within 15 minutes after injury. When 20% body surface area injuries were induced in a 25 degrees C environment, all of the animals survived. In the 25 degrees C environment, neither acute core body temperature elevations nor use of fluid resuscitation predicted survival. In contrast, in a 38.5 degrees C environment core body temperatures rapidly exceeded 41 degrees C with the 20% injury, and all of the animals died within minutes in spite of fluid resuscitation. These studies suggest that the ambient environmental temperature may significantly influence a thermally injured animal's ability to rapidly eliminate absorbed heat of injury and result in an elevated core body temperature, which may contribute to the immediate lethality of the injury.

Animals↗
PubMedDate not supplied

An effective technique of scrotal harvest.

In male patients with extensive burns, the scrotum is often spared and is potentially a very useful donor site. We describe a technique that simplifies scrotal harvest and facilitates the procurement of clinically useful amounts of split-thickness skin.

Adolescent↗
PubMedDate not supplied

Injury-induced inhibition of fat absorption.

Burn injury inhibits lipoprotein lipase, which leads to an impeded clearance of triglycerides from the plasma and an increase in serum triglycerides. Intestinal brush border lipase, which hydrolyzes triglyceride to free fatty acids and is essential for absorption of triglycerides from the gastrointestinal tract, could also be inhibited by burn injury. In thermally injured rats, the absorption and oxidation of enterally administered 14C-palmitate triglyceride, brush border lipase activity, and small-intestinal and colonic content of fat were determined. Absorption of 14C-palmitate triglyceride and production of 14CO2 were reduced 50% 18 hours after injury (p < 0.01). In addition, brush border lipase activity was reduced 50% (p < 0.01). Because brush border lipase function is essential to the proper absorption of enterally administered fat, inhibition of intestinal lipase could be an important factor in enteral diet effectiveness.

Animals↗
PubMedDate not supplied

Arterial blood pressure immediately after thermal injury: the role of anesthesia.

Mean arterial blood pressure was measured in anesthetized rats. The duration that the rats were under anesthesia with ether or methohexital was brief, and the animals were allowed to awaken early after injury. Three hemodynamic measurements were compared: (1) lowest mean arterial blood pressure, (2) duration at lowest mean arterial blood pressure, and (3) time to recover initial mean arterial blood pressure. In these studies the anesthetic agents reduced mean arterial blood pressure by 36%, recovering to normal pressures within 24 to 39 minutes. During the hemodynamic observation period, no significant additional hemodynamic effects as a result of the thermal injury were seen. Administration of resuscitation fluid did not significantly affect hemodynamics during the observation period in this study. These studies demonstrate that anesthesia dominates the short-term cardiovascular effects of thermal injury, and therefore caution is required in the interpretation of acute cardiovascular effects immediately after thermal injuries with patients under general anesthesia.

Anesthesia, General↗
PubMedDate not supplied

A quantitative model of invasive Pseudomonas infection in burn injury.

To evaluate newer therapies for wound infections, it becomes necessary to quantify bacteria that invade from the infected wounds into the adjacent tissues. For example, antibody-targeted photolysis targets the invasive Pseudomonas with antibodies carrying photochemical dyes. A full-thickness burn wound was infected with Pseudomonas aeruginosa with a modification of previous methods. In mice, a skin fold was elevated, and two preheated brass blocks at 92 degrees to 95 degrees C were applied for 5 seconds, producing a 5% total body surface area injury with discrete margins. The eschars were immediately inoculated with Pseudomonas. Survival at 10 days was 100% with burn injury alone and 60% with infected burns. Pseudomonas (10(8)/gm) were recovered from the unburned muscle by 24 hours. The method produced uniform and reproducible quantitative bacteriology within the muscle immediately beneath the burn injury (SL < 0.05). Quantitative comparisons can be used to determine the effectiveness of newer modalities to control Pseudomonas burn wound infections.

Animals↗
PubMedDate not supplied

Modified Stryker frame for intraoperative positioning of the patient with burns.

Positioning large patients with burns for prone burn procedures can be very difficult, requiring operating room personnel to use a gang-lift technique. We have used the upper portion of a Stryker frame mounted to a standard operating room table base in more than 200 burn procedures in adults to move patients from the supine to the prone position, and back, without complication.

Burns↗
PubMedDate not supplied

Midazolam infusion in pediatric patients with burns who are undergoing mechanical ventilation.

Adequate sedation is an integral component of mechanical ventilation. To document the safety and efficacy of midazolam infusion in pediatric patients with burns who were undergoing mechanical ventilation, a retrospective review was done of all patients requiring mechanical ventilation over a 22-month period. Twenty-four acutely burned pediatric patients required mechanical ventilation. The average age was 6.4 years (range 7 months to 12 years), and the average burn size was 50% of the body surface (range 40% to 95%). Midazolam infusion was initiated at an average dose of 0.045 mg/kg/hr (range 0.01 to 0.09 mg/kg/hr). The maximum dose administered averaged 0.11 mg/kg/hr (range 0.04 to 0.35 mg/kg/hr). The duration of infusion averaged 16.5 days (range 4 to 56 days). All patients received simultaneous infusions of morphine sulfate. Midazolam infusion was titrated to achieve a diminished narcotic requirement, decreased anxiety, and better tolerance of dressing changes. No hypotension or problems weaning from mechanical ventilation were seen. Two (8.3%) children experienced reversible neurologic abnormalities attributed to midazolam infusion but made full neurologic recoveries. In conclusion, our experience with midazolam infusion in pediatric patients with burns who were undergoing mechanical ventilation is favorable and supports its continued use.

Anxiety↗
PubMedDate not supplied

The burn unit as a resource for the management of acute nonburn conditions in children.

Burn units bring together resources to manage large complex wounds, organ failures, and the hypermetabolic response to injury. These resources can also facilitate management of other problems such as purpura fulminans, toxic epidermal necrolysis, staphylococcal scalded skin syndrome, and major mechanical soft-tissue injuries. During a recent 10-year interval 2.4% of all acute admissions to a regional pediatric burn facility were in this category and form the basis for this review.

Acute Disease↗
PubMedDate not supplied

Clinical experience with the use of biodegradable tacks in pediatric patients with burns.

Stainless steel staples are very popular for securing grafts and dressings on patients with burns because of the speed and security with which they can be applied and the fact that stainless steel is nonreactive. In patients with large burns hundreds of staples are used and can be difficult to visualize and remove; they are therefore retained. Although stainless steel does not cause local tissue reaction, its presence can confuse the later evaluation of local pain. A new biodegradable tack has been developed. We describe an initial experience with this device in pediatric patients with burns and make suggestions regarding their use.

Adolescent↗
PubMedDate not supplied

Accelerated healing and reduced need for grafting in pediatric patients with burns treated with arginine-glycine-aspartic acid peptide matrix. RGD Study Group.

Arginine-glycine-aspartic acid (RGD) peptide matrix is designed to promote dermal healing by providing a molecular scaffold that facilitates cell ingrowth and establishment of normal tissue architecture. This study investigated the effectiveness and safety of RGD peptide matrix in the treatment of partial-thickness scald burns in pediatric patients. Either topical RGD peptide matrix or control treatment with silver sulfadiazine was applied to matched burn sites daily for up to 21 days. With RGD peptide matrix application under synthetic occlusive dressing, the incidence of healing was nearly threefold higher, average time to healing 2.5 days shorter (regression estimation), extent burn closure at all treated sites 37% greater, and number of needed grafting procedures fourfold lower compared with control treatment. All these differences were statistically significant. RGD peptide matrix was well tolerated. RGD peptide matrix promoted and accelerated healing in this study and thus may be able to reduce morbidity and treatment costs of partial-thickness burns in pediatric patients.

Administration, Topical↗
PubMedDate not supplied

Candidemia in the pediatric patient with burns.

The incidence of candidemia in patients with burns appears to be falling. However, when it occurs it remains a significant cause of morbidity and a potential cause of death. A 5-year retrospective review revealed that 138 (14.4%) of 962 pediatric patients who had been acutely burned had Candida species isolated from one or more sites during their hospital stay, but candidemia developed in only 17 patients (12.3% of those from whom Candida species were recovered and 1.8% of all admissions). Patients from whom Candida species were recovered at one site had a 0% incidence of candidemia, those from whom Candida species were recovered at two sites had a 22.2% incidence of candidemia, and those from whom Candida species were recovered at three or more sites had a 34.4% incidence of candidemia. These differences were significant by chi-square analysis (p < 0.0001). There was a low mortality rate associated with candidemia, with only one (5.9%) of the 17 patients dying as a direct result of invasive Candida infection. Nystatin administered enterally did not prevent the development of candidemia. Our review suggests that delay in biologic wound closure and exposure to broad-spectrum antibiotics are associated with an enhanced risk of candidemia. Wound closure and systemically administered amphotericin B remain the mainstays of therapy.

Adolescent↗
PubMedDate not supplied

Burn depth estimation by use of indocyanine green fluorescence: initial human trial.

Indocyanine green dye (ICG) fluoresces when illuminated by infrared light. After successful trials in a porcine model and with approval of the Massachusetts General Hospital's human studies committee, 10 adult patients with burn injuries were given 0.2 mg/kg ICG intravenously, and 825 nm fluorescence images were obtained with 780 nm excitation at 5 minutes after injection in the initial five patients and at 1, 2, 3, 4, 5, and 10 minutes in the subsequent five patients. Fluorescence intensities at burned and unburned sites were determined and images were correlated with burn depth as determined by healing or intraoperative assessment. In the latter five patients, seven sites were imaged (six that were of partial thickness and one that was of full thickness). The burn/normal skin fluorescence ratio was greater than 1 for superficial burns and less than 1 for deep burns. Imaging within 5 minutes of injection resulted in optimal contrast between injured and uninjured tissue. In this initial pilot trial it is apparent that ICG fluorescence has potential value as an aid in the early estimation of burn depth. In subsequent trials we will attempt to refine our ability to correlate ICG fluorescence images with burn depth.

Adult↗
PubMedDate not supplied

Planimetry study of the percent of body surface represented by the hand and palm: sizing irregular burns is more accurately done with the palm.

Sizing irregular burns is commonly done with use of the patient's hand as a template representing 1% of the body surface. To verify that this is accurate over a broad range of ages or to see if the surface of the palm is a more consistent template, a planimetry study was done. This revealed that the surface area of the palm averaged 0.52% total body surface area (+/- 0.07) and the palmar surface of the hand 0.85% total body surface area (+/- 0.08). The surface of the palm was a more consistent template and represented 0.5% of the body surface over a broad range of ages.

Adolescent↗