Assessment of methotrexate as a potential immunosuppressive agent in baboons

Methotrexate is an anti-proliferative agent that affects both T-cell and B-cell immunity, and therefore might be expected to suppress antibody (Ab) production. Although it has been used in xenotransplantation studies to suppress anti-pig Ab production, it has always been used in combination with other immunosuppressants. The purpose of this study was to measure its effect as a single immunosuppressant on anti-Gal Ab production in baboons (n=4). Pharmacokinetic studies showed that methotrexate was not detected in the blood when administered per os. Prolonged daily IV or IM administration (i) reduced T-cell and B-cell numbers by 50% to 70% and modestly reduced responsiveness on mixed lymphocyte reaction (but only at toxic doses) and (ii) did not result in lowered anti-Gal Ab levels, only marginally reducing the rate of return of Ab after extracorporeal immunoadsorption. Our observations would suggest that methotrexate will not contribute significantly to immunosuppressive regimens in the baboon at non-toxic doses.     

Effects of dexmedetomidine on propofol and remifentanil infusion rates during total intravenous anesthesia for spine surgery in adolescents

Introduction: Total intravenous anesthesia with propofol and a synthetic opioid is a frequently chosen anesthetic technique for posterior spinal fusion. Despite its utility, adverse effects may occur with high or prolonged propofol dosing regimens including delayed awakening. The current study investigated the propofol‐sparing effects of the concomitant administration of the α₂‐adrenergic agonist, dexmedetomidine, during spinal fusion surgery in adolescents. Methods: The surgical database of the department of orthopedic surgery was searched and patients (12–21 years of age) were identified who had undergone spinal fusion for either idiopathic or neuromuscular scoliosis during the past 24 months. Patients were assigned to two groups. Group 1 included patients anesthetized with propofol and remifentanil and group 2 included patients anesthetized with dexmedetomidine, propofol, and remifentanil. In the latter group, dexmedetomidine was administered as a continuous infusion of 0.5 μg·kg^?1·h^?1 started after the induction of anesthesia without a loading dose. Propofol was adjusted to maintain the bispectral index (BIS) number at 40–50 and remifentanil was adjusted to maintain the mean arterial pressure (MAP) at 50–65 mmHg. Labetolol or hydralazine was used if the MAP could not be maintained at 50–65 mmHg with remifentanil up to a maximum dose of 0.6 μg/kg/min. Statistical analysis included a nonpaired t‐test for parametric data (age, weight, remifentanil/propofol infusion requirements, and heart rate/blood pressure values). A nonparametric statistical analysis (Dunn) was used to compare BIS numbers. Parametric data are presented as the mean ± sd while nonparametric data are presented as the median and the 95th percentile confidence intervals. Results: Twelve patients received propofol–remifentanil–dexmedetomidine and 24 received propofol–remifentanil. There were no differences in the demographic data, BIS numbers or hemodynamic parameters between the two groups. There was a reduction in the propofol infusion requirements in patients who also received dexmedetomidine (71 ± 11 μg·kg^?1·min^?1) compared with those receiving only propofol–remifentanil (101 ± 33 μg·kg^?1·min^?1, P = 0.0045). No difference was noted in the remifentanil infusion requirements or the use of supplemental agents (hydralazine and labetolol) to maintain controlled hypotension. Conclusion: The concomitant use of dexmedetomidine in patients undergoing spinal fusion reduces propofol infusion requirements when compared with those patients receiving only propofol and remifentanil.     

Expression of genes encoding antimicrobial proteins and members of the toll-like receptor/nuclear factor-κB pathways in engineered human skin

Skin functions as a first line of defense against microbial invasion. Tissue-engineered cultured skin substitutes (CSS) are used to aid wound closure in massively burned patients, and have been used to facilitate safe and effective wound closure in adult patients with chronic wounds. Although they contain only two cell types at grafting, they can potentially contribute to innate defense against pathogens and stimulation of adaptive immunity. Gene microarrays were used to identify expression in cultured skin of genes involved in innate and adaptive immune responses, and to evaluate the effects of cytokine stimulation on expression levels. Cultured skin expressed multiple antimicrobial protein genes, including human β defensins 1 and 2 and S100A12. In addition, the antiviral gene APOBEC3G, which was not previously identified in skin, was expressed in CSS and up-regulated by interleukin-1α and tumor necrosis factor α. Cathelicidin was not expressed in unstimulated CSS, but was induced by cytokine treatment. Further, genes encoding several proinflammatory cytokines and members of the toll-like receptor and nuclear factor κ B pathways were expressed in CSS, suggesting that cells in CSS can mediate activation of inflammatory responses. The observed expression patterns indicate that engineered human skin utilizes innate defense mechanisms similar to those reported for native skin. Therefore, regulation of these pathways by cytokine stimulation may offer a mechanism for increasing innate immunity in CSS to combat wound infection after grafting onto patients.     

Effect of a Practice Guideline for Emergency Department Care of Falls in Elder Patients on Subsequent Falls and Hospitalizations for Injuries

OBJECTIVE: To determine the effect of a practice guideline for the ED management of falls in community-dwelling elders on selected health outcomes. METHODS: The experimental design was a prepost-intervention comparison with one-year pre- and post-intervention phases. The guideline was presented to emergency physicians and nurses during a two-week interval between these two periods. The intervention also included health information provided to the subjects and a one-time educational intervention directed at primary care providers. The number of falls in the year following the ED visit was determined by telephone interview. The number of hospitalizations for falls was determined from the HMO database of all health care encounters. RESULTS: 1,899 patients were eligible for the study; 1,140 pre-intervention and 759 post-intervention patients. Of these, 1,504 (79%) were interviewed by telephone 12 to 15 months after their initial ED visits. Eighteen percent of the pre-intervention and 21% of the post-intervention subjects reported at least one fall in the 12 months following their ED visits (p = 0.162). The rate of falls per 100 patient years was 36.2 in both groups. Three percent of both groups were hospitalized at least once for a fall in the year following their ED visits. One percent in each group were hospitalized for a hip fracture. CONCLUSIONS: The attempted implementation of a practice guideline for the ED management of falls in community-dwelling elders did not result in a reduction in total falls, or in hospitalizations for falls, injuries, or fractures.     

Apoptosis in regenerating and denervated, nonregenerating urodele forelimbs

Denervated limbs of larval salamanders fail to regenerate if amputated and, unlike adult limbs, undergo regression. The cellular basis of the tissue loss is poorly understood. We used TUNEL staining of larval axolotl limbs fixed and sectioned at intervals after bilateral amputation and unilateral denervation to investigate the role of apoptosis during normal limb regeneration and denervated limb regression. In the first week after amputation a small percentage of apoptotic cells was found in both innervated and denervated limbs. During the second week the apoptotic index remained low in the mitotically active mesenchymal cells of the regenerating limbs, but increased twofold in the nondividing, dedifferentiated cells of the regressing limbs. TUNEL-positive cells resembling apoptotic bodies were restricted primarily to the dedifferentiated area beneath the wound epithelium, but were also present within the wound epithelium itself. Macrophages were identified immunohistochemically and were also found in increased numbers in distal areas of the denervated regressing limbs. The results suggest a role for apoptosis in the early phase of normal regeneration and indicate that denervated limb regression involves an increased rate of apoptosis and removal of apoptotic bodies by macrophages and the wound epithelium.     

Minimum oxygen requirements during anaesthesia with the Triservice anaesthetic apparatus A study of drawover anaesthesia in the young adult

Thirty-six servicemen were anaesthetised using the Triservice anaesthetic apparatus. They were allocated randomly into one of two groups, to breathe spontaneously or to receive artificial ventilation, and into subgroups who were given air alone, or air supplemented with 1 or 4 litres/minute of oxygen. A further 12 subjects were studied subsequently using 0.5 litres/minute of added oxygen. Intra-operative blood gases were compared with those of awake premedicated controls. Artificial ventilation was associated with an unchanged arterial oxygen tension with air alone; in the other subgroups arterial oxygen tension was higher than with spontaneous respiration when related to inspired oxygen fraction (p less than 0.05). Air anaesthesia caused significant hypoxaemia with spontaneous ventilation (p less than 0.05), and 50% of the subjects required assisted ventilation. There was also a significant respiratory acidosis (p less than 0.05). Intermittent positive pressure ventilation is the method of choice for field anaesthesia when oxygen is unavailable. Spontaneous respiration must be supplemented with at least 0.5 litres minute of oxygen.