Objective evaluation of the performance of surgical trainees on a porcine model of open colectomy.

BACKGROUND: Evaluation of surgical trainee operative performance is rarely objective. A rating system is proposed that assesses trainee performance objectively and quantifies technical improvement. METHODS: General surgery trainees were evaluated while performing porcine segmental colectomy. Initial instruction was provided for the critical operative steps. Evaluations were later repeated without additional instruction. Performance in 17 critical areas was scored. RESULTS: Twenty-three trainees were evaluated. Performance was divided into thirds, with a significant difference detected between tertiles (P < 0.001). Postgraduate year 2 trainees scored lower than those in years 3 and 4 (P < 0.001), but there was no difference between year 3 and 4 trainees (P = 0.557). Mean repeat scores were improved by 35 per cent, with most improvement at postgraduate year 2 level (71 per cent). Mean time taken to complete the operation was reduced by 23 per cent, with the largest reduction in the year 2 group. CONCLUSION: The results support the use of this rating system as a tool for the objective evaluation of trainee operative skill. Instruction in the performance of segmental colectomy using deconstructed, step-by-step direction improved the ability of junior trainees to complete the operation. This evaluation system may be useful in the assessment, instruction and technical development of surgical trainees.

The toxicology of interleukin-12: a review.

Recombinant murine interleukin (IL)-12 (rmIL-12) exhibits antitumor, antiviral, and antimicrobial activities and can modify allergic inflammatory reactions in animal models. Recombinant human IL-12 (rhIL-12) is currently in clinical trials for treatment of cancer, asthma, and viral hepatitis. Principally a phagocyte-derived cytokine, IL-12 targets natural killer cells and T lymphocytes, stimulating their activity and the secretion of interferon (IFN)-gamma. An understanding of the toxicology of IL-12, due in part to effects mediated by IFN-gamma, has emerged from preclinical safety and mechanistic studies and initial clinical trials. Target organs common to several animal species and humans include the lymphohematopoietic system, intestines, liver, and lung.

Biologic effects of recombinant human interleukin-12 in squirrel monkeys (Sciureus saimiri).

BACKGROUND: Interleukin-12 is a novel heterodimeric cytokine that stimulates the proliferation of activated T and NK cells and induces lymphokine-activated killer cell activity in vitro. To investigate the biological effects of recombinant human IL-12 (rHuIL-12) in vivo, two exploratory studies were conducted in squirrel monkeys (Sciureus saimiri), which have been shown to be pharmacologically responsive to rHuIL-12 in vitro. EXPERIMENTAL DESIGN: In the first study, 18 monkeys (3/sex/group) were given daily subcutaneous injections of 0 (vehicle control), 10, or 50 micrograms/kg/day rHuIL-12 for 14 days. In the second study, 18 monkeys were given 0, 0.1, or 1 micrograms/kg/day rHuIL-12 for 14 days The animals were monitored for clinical signs, hematology and clinical chemistry changes, and sacrificed on day 15 to evaluate gross and histopathologic changes. One monkey in the high dose group was sacrificed moribund on day 14. RESULTS: Monkeys given rHuIL-12 had dose-related hematologic changes characterized by mild to moderate anemia and leukocytosis. Serum chemistry changes included hypoproteinemia, hypoalbuminemia, hypophosphatemia, and hypocalcemia. Gross pathologic findings included generalized lymph node enlargement and splenomegaly with pulmonary edema and peritoneal effusions in two high dose monkeys. Dose-related histopathologic findings included thymic cortical atrophy, splenic lymphoid hyperplasia with histiocytic hyperplasia and extramedullary hematopoiesis of red pulp, Kupffer cell hypertrophy and hyperplasia, trilineage bone marrow hyperplasia, and reactive hyperplasia of lymph nodes. Animals in the 10 and 50 micrograms/kg/day dose groups developed high titers of anti-rHuIL-12 antibodies by day 15. CONCLUSIONS: These studies indicate that rHuIL-12 is bioactive over a wide dose range and induces prominent hyperplasia of hematopoietic and lymphohistiocytic tissues in squirrel monkeys. Moreover, positive immunomodulatory activity (enhanced lymphocyte lytic activity) was detected at a dose of rHuIL-12 that is 500-fold less than the dose causing severe toxicity.

Interleukin-12: a cytokine with therapeutic potential in oncology and infectious diseases.

IL-12 is a cytokine that promotes cell-mediated immunity by promoting Th1-type cytokine responses, enhancing the lytic activity of NK/LAK cells, augmenting specific CTL responses, and inducing the production of IFN-gamma. On the other hand, IL-12 suppresses the development of Th2-type cytokine responses and humoral immunity, particularly IgGl and IgE responses. It is likely that IL-12 normally plays an important role in the host defense against intracellular microbial pathogens. In addition, the administration of rIL-12 to mice has been shown to have potent therapeutic effects in several tumour and infectious disease models. IL-12 has been shown to be more efficacious than IL-2 in several murine tumour models, and toxicology studies suggest that it may have a substantially better therapeutic index. In addition, the long serum half-life of IL-12 relative to other cytokines will allow more flexibility in dosing schedules. However, future clinical trials are required to determine whether the efficacy of IL-12 seen in these experimental models is predictive for its use as an immunomodulatory drug in humans.

Hematological effects of 2',3'-dideoxycytidine in rabbits.

The antiviral nucleoside analogue 2',3'-dideoxycytidine (ddC) is a DNA chain terminator and/or inhibitor of human immunodeficiency virus (HIV) reverse transcriptase. We evaluated the effects of ddC in 36 New Zealand white rabbits. Three/sex were assigned to a control group and 5 treatment groups (10-250 mg/kg/day) for 13 or 18 weeks. Blood samples were taken 1 week prior to treatment and weekly thereafter to termination with the exception of the 2 highest dose groups, where blood sample collection was terminated at week 13. Selected hematological analytes were measured weekly with the exception of prothrombin time (PT) and activated partial thromboplastin time (APTT). PT and APTT and selected biochemical analytes were measured prior to treatment, at 7 weeks, and after 13 weeks of treatment. All rabbits were necropsied. Giemsa and hematoxylin and eosin sections were prepared from methacrylate-embedded marrow. Hematological effects included decreases in red blood cell count, hemoglobin, hematocrit, and white blood cell count and increases in mean corpuscular volume and red cell distribution width. Platelets, platelet volume, PT, APTT, and mean corpuscular hemoglobin concentration values were variable or unchanged. Effects were dose-related, most were seen at 1 week, and they persisted to term. Bone marrow histopathologic changes included megalocytosis, erythroid hypoplasia, bizarre erythroid nuclear morphology, nuclear-cytoplasmic asynchrony, and increased mitotic figures. Lymphopenia caused by ddC plateaued at 2 weeks and persisted until termination. Heteropenia (neutropenia) was sporadic. Biochemical values for serum analytes were unchanged by treatment. The principal hematological effect of ddC upon the erythron was characterized as a nonregenerative macrocytic anemia with erythroid hypoplasia and megaloblastic erythropoiesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Antiproliferative effect of interleukin-1 on human ovarian carcinoma cell line (NIH:OVCAR-3).

The human ovarian carcinoma cell line, NIH:OVCAR-3, possesses high affinity receptors for interleukin-1 (IL-1). Binding experiments with 125I-IL-1 alpha indicate a dissociation constant of approximately 55 pM and the presence of approximately 7800 receptors/cell. These receptors bind both IL-1 alpha and IL-1 beta and internalize IL-1. Proliferation is NIH:OVCAR-3 cells is inhibited by IL-1. Half-maximal inhibition is observed with 2-3 units/ml of IL-1 alpha or IL-1 beta. A maximal effect (80% inhibition of cell proliferation) is achieved by treatment of cells with greater than or equal to 10 units/ml of IL-1 for 3 days. The antiproliferative effect of IL-1 is blocked by IL-1 receptor antagonist. Light and electron microscopy studies show that IL-1 treatment causes cytopathological changes and a reduction in the number of mitotic figures in NIH:OVCAR-3. IL-1 stimulates prostaglandin E2 release by NIH:OVCAR-3 cells, but this response is unrelated to the antiproliferative effect of IL-1. Interferon-alpha A (IFN-alpha A) also inhibits growth of NIH:OVCAR-3 cells in a concentration-dependent manner. Combination of IFN-alpha A and IL-1 gives synergistic inhibition of NIH:OVCAR-3 cell proliferation. IL-1 alone or in combination with IFN-alpha A or other agents may be useful for treatment of human ovarian cancer.

DNA repair by articular chondrocytes. V. O6 methylguanine-acceptor protein activity in resting and cultured rabbit and human chondrocytes.

The level of O6-methylguanine acceptor protein activity was examined in rabbit and human articular chondrocytes of different ages. The activity per microgram of DNA in rabbit chondrocytes was 5-fold lower than in humans. There was no age-dependent decrease in the activity of resting or cultured chondrocytes of either species. The values for resting cells were comparable to those of cultured cells. The lack of age-related differences in methyltransferase activity, in contrast to nucleotide excision repair [Mech. Ageing Dev. 32 (1985) 39-55], indicates that separate repair systems behave differently with respect to chronological aging. The methyl transferase activity may be more essential for survival of articular chondrocytes and therefore more highly conserved with age.

Effect of purified growth factors on rabbit articular chondrocytes in monolayer culture. II. Sulfated proteoglycan synthesis.

The effect of 3 purified peptide growth factors--platelet-derived growth factor (PDGF), epidermal growth factor (EGF), pituitary fibroblast growth factor (FGF)--heat-inactivated fetal bovine serum (FBS), insulin, and 0.2 mM ascorbate on synthesis of sulfated proteoglycan by rabbit articular chondrocytes was studied in monolayer culture. Growth of the cells increased linearly as the concentration of heat-inactivated FBS rose from 0 to 30%. Glycosaminoglycan (GAG) synthesis (35SO4/micrograms DNA) was enhanced as the concentration of heat-inactivated FBS went from 0 to 5%. At higher levels of serum, radiosulfate incorporation declined progressively. Two modes of study of the test factors were used: 1) the dose of the factor was increased while the serum concentration was fixed at a low basal level (1% heat-inactivated FBS); 2) the dose of the test factor was kept constant but the level of heat-inactivated FBS varied from 0 to 10%. There was an inverse relationship between GAG and DNA synthesis when proliferation of cells was increased by EGF and platelet lysate. PDGF (1 U/ml) stimulated radiosulfate incorporation as well as DNA formation in the serum-free medium; the values for GAG synthesis did not increase as the serum concentration increased, but the cell mass did. The action of FGF was intermediate between that of EGF and PDGF: with 50 ng FGF/ml, increasing concentrations of serum caused a large progressive reduction of radiosulfate incorporation as growth was stimulated. In basal medium, however, FGF caused mild enhancement of GAG synthesis. Insulin increased aggregatable proteoglycan production far out of proportion to its growth-promoting activity in the presence of 1% heat-inactivated FBS. The response was effaced when higher concentrations of serum were employed. Ascorbate had a unique anabolic effect, increasing both cell growth and proteoglycan synthesis that is not suppressed by higher concentrations of serum. The content of serum and its several peptide and hormonal components thus have divergent effects on growth and proteoglycan synthesis in cell culture. This phenomenon must be taken into account in studying biochemical processes and pharmacologic reactions of articular chondrocytes in vitro.

Effect of purified growth factors on rabbit articular chondrocytes in monolayer culture. I. Dna synthesis.

The ability of purified growth factors, insulin, ascorbate, and several other compounds to stimulate DNA synthesis by rabbit articular chondrocytes was studied in monolayer culture. Platelet-derived growth factor (1 U/ml), pituitary fibroblast growth factor (1-100 ng/ml), and epidermal growth factor (1-50 ng/ml) were stimulatory in a basal medium supplemented with 1% heat-inactivated fetal bovine serum. Insulin, 1-50 micrograms/ml, has small growth-promoting effects but acted synergistically with platelet-derived, pituitary fibroblast, and epidermal growth factors. Increasing concentrations of serum up to 10% enhanced the growth-promoting action of the purified factors, but not of insulin. There were indications of cooperation between insulin and bovine serum albumin and dexamethasone. Ascorbate (0.2 mM) reduced or had little growth-promoting action in the basal medium. At 5 and 10% serum concentrations, however, ascorbate promoted DNA synthesis as effectively as the purified growth factors. No significant stimulatory effect was shown by transferrin, thrombin, L-glutamine, putrescine, selenous acid, dexamethasone, 7S nerve growth factor, or multiplication-stimulating activity.