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Biomedical subjects

G F Babcock

Publications and source records attributed to G F Babcock.

At least 19 recordsLinked to original sources
PubMed1992

Isolation of Pneumocystis carinii cysts by flow cytometry.

Pneumocystis carinii cysts were separated as enriched populations from suspensions of lung homogenate obtained from infected rats containing all developmental stages of this organism. Isolation of cyst populations was achieved by incubating filtered lung homogenate with the fluorescent phospholipid analog 1-palmitoyl-2-C6-NBD-phosphatidylcholine. Whereas cysts did not fluorescence as a result of outer-wall restraint of lipid integration, trophozoites and young intermediate stages readily incorporated the fluorescently labeled lipid analog into their outer membrane. The two distinct labeling patterns displayed by cysts and other developmental phases of P. carinii constitute a novel, easy, and reproducible means of isolating cysts from infected lung homogenate by flow cytometry.

Animals↗
PubMed1992

Reduced expression of neutrophil CD11b and CD16 after severe traumatic injury.

Overwhelming sepsis continues to be a major source of morbidity and mortality in patients who have sustained severe traumatic injury. Recently, much interest has been focused on the role of the peripheral blood neutrophil (PMN) in infections in these patients. Two surface receptors, CD11b (CR3) and CD16 (Fc gamma RIII), are thought to participate in bacterial phagocytosis and are both present on greater than 85% of normal PMNs. We have previously shown that cells that lack both of these receptors have markedly reduced phagocytic function. The purpose of this study was to determine the effect of severe trauma on the expression of these PMN receptors. Twenty severe trauma patients, age 19-70 years, presenting with an initial APACHE II score of greater than or equal to 10 were arbitrarily divided into two groups to define severity of injury: Group A, initial APACHE II of 10-18 (n = 11) and Group B, initial APACHE II of 19-25 (n = 9). Blood was obtained on admission, on Day 3, and weekly thereafter. PMNs were stained with fluorochrome-labeled monoclonal antibodies directed against CD11b and CD16 and then analyzed by flow cytometry. Controls consisted of 14 normal adults, age 20-65 years. The percentage and absolute numbers of CD11b+/CD16+ PMNs were determined for each patient or control sample. ANOVA and multiple comparison of variables (P = 0.05) were performed for each week. Values for Group A were different from controls at Weeks 0, 1, and 3. Values for Group B were significantly lower than those of controls at all weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1992

Impact of blood transfusion and burn injury on microbial translocation and bacterial survival.

The role of the immune system in microbial translocation must be clarified. In these studies, the effect of blood transfusion-related immunosuppression on translocation was investigated in a burn animal model previously known to increase the gut's permeability to 14C-radiolabeled Escherichia coli. In a first experiment, Balb/c mice underwent transfusion (T) with 0.2 mL per mouse of allogeneic C3H/HeJ mouse blood 5 days prior to undergoing 30-percent burn injury (B) and simultaneous gavage (G) with 10(9) E. coli bacteria labeled with 14C. An additional six groups of Balb/c mice underwent different combinations of T, B, and G procedures (TG, BG, TB, T, B, G). Survival rate was recorded for all groups on Day 10. This experiment suggested that B and T, to a lesser extent, were the factors affecting survival, although the combination of T, B, and G clearly showed a synergistic effect on mortality. In a second experiment, 18 Balb/c mice belonging to TBG, BG, TG, and G groups were sacrificed 1, 4, and 24 hours after burn or gavage. The residual radioactivity and the percentage of viable bacteria were computed for mesenteric lymph nodes, spleen, liver, lungs, blood, and peritoneal fluid. Statistical analysis of the radionuclide counts recognized B as the only variable able to enhance the magnitude of 14C E. coli translocation. The percentage of viable bacteria showed that T and, more moderately, B were the factors leading to the failure of bacterial clearance in the tissues.

Animals↗
PubMed1992

The induction of immunologic hyporesponsiveness by preoperative donor-specific transfusions and cyclosporine in human cadaveric transplants. A preliminary trial.

A prospective randomized preliminary trial was performed in patients undergoing cadaveric renal transplantation to determine the potential benefits, disadvantages, and logistic problems associated with the administration of donor-specific transfusions and cyclosporine initiated 24 hr before transplantation. Ten patients received DST followed by continuous intravenous CsA approximately 24 hr before cadaveric renal transplantation from the same donor. Twelve patients receiving sequential therapy with Minnesota antilymphoblast globulin, azathioprine, and steroids with subsequent conversion to CsA served as controls. Patient demographics and the donor characteristics were evenly matched in the two groups. While the study group had longer cold ischemia time and more evidence of renal dysfunction within the first two weeks, subsequent renal function was identical in the groups and there were fewer episodes of severe rejection requiring treatment with OKT3 within the first six months in the DST group (5 vs. 0, P less than 0.05), which also had less reactivity in mixed lymphocyte cultures against preserved donor-specific lymphocytes than did the control group (stimulation index 9.0 +/- 3.0 vs. 25.3 +/- 6.0, respectively, P less than 0.05). The need for dialysis, incidence of infections and other complications, and subsequent immunosuppressive therapy were not different in the two groups. It is concluded that DSTs and intravenous CsA initiated 24 hr prior to transplantation are capable of inducing reduced immunologic responsiveness against the specific donor. Patients treated with this therapy should receive organs from "ideal" donors without risk factors and cold ischemia time should not exceed 30 hr. Further clinical studies of this approach are warranted.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Rapid whole-blood microassay using flow cytometry for measuring neutrophil phagocytosis.

A simple flow cytometric method (FCM) for measuring phagocytosis of Staphylococcus aureus by human neutrophils (polymorphonuclear leukocytes [PMNs]) is described. This assay utilizes 100 microliters of EDTA-anticoagulated whole blood and a simplified method of fluorescently labeling bacteria. A commercially available whole-blood lysing reagent allows for the removal of erythrocytes and the exclusion of external free or adherent bacteria. Phagocytized bacteria are unaffected by this reagent, so PMNs containing internalized bacteria can be easily identified by FCM. Advantages of this method include the following: (i) small sample size, (ii) no requirement for PMN separation, (iii) rapid reliable method of labeling the bacteria, (iv) ability to distinguish between adherent bacteria and those which are actually internalized, (v) avoidance of vital dyes as quenching agents, and (vi) ability to fix cells and store for future FCM analysis.

Adult↗
PubMed1991

Distribution and survival of Escherichia coli translocating from the intestine after thermal injury.

The present investigation was performed to study the kinetics of tissue distribution and deposition of Escherichia coli and endotoxin translocating from the intestine after thermal injury. Escherichia coli was grown in the presence of 14C glucose and both labeled bacteria and endotoxin prepared from the labeled bacteria were used as translocation probes. Escherichia coli (10(8) to 10(10) bacteria) and E. coli endotoxin (100 micrograms per animal) were gavaged into the stomach immediately before a 30% burn injury was inflicted in mice. Animals were killed 1, 4 and 24 hours after burn injury. Translocation occurred extensively within 1 hour after burn injury. Expressed as amount of radioactivity per gram of tissue, translocation was greatest in the mesenteric lymph node (MLN) followed by spleen, lung, and liver. Translocation of endotoxin was similar to translocation of intact bacteria, with the exception that less radioactivity could be found in the peritoneal cavity and more in the liver. Both intact E. coli and endotoxin translocated directly through the intact bowel wall. Killing of bacteria was greatest in the MLN and spleen, approximating 95% to more than 99% of translocating bacteria. Killing efficiency was lowest in the lungs. It is concluded that estimation of translocation by viable bacterial counts in tissues grossly underestimates the extent of translocation of bacteria and ignores the extent of translocation of endotoxin. Translocation of endotoxin may have biologic significance that is independent of and in addition to translocation of intact bacteria.

Animals↗
PubMed1990

Neutral surface aminopeptidase activity of human tumor cell lines.

Seven human tumor cell lines were studied for their neutral surface aminopeptidase (AP) activity. The activity was shown to exist on all cell lines to varying degrees. The neutral AP activity of the cell lines had similar Km values and were affected by the same inhibitors as those reported for AP's of peripheral blood lymphocytes (PBL, Refs. 1 and 2). However, a difference was seen in the Vmax values of the various cell lines. These values were shown to correlate (r = 0.767, P less than 0.05) with cell surface area.

Aminopeptidases↗
PubMed1990

Flow cytometric analysis of neutrophil subsets in thermally injured patients developing infection.

The expression of CD11b (CR3, complement receptor type three), CD16 (FcR, Fc IgG receptor), and CD35 (CR1, complement receptor type one) on neutrophils obtained from thermally injured patients was examined using immunofluorescence and flow cytometry. Because defects in neutrophil function have been related to an increased risk of infection and death following thermal injury, we compared changes in neutrophil subpopulations following thermal injury with the onset of infection. Neutrophils from 34 patients with large thermal injuries were monitored weekly for CD11, CD16, and CD35. Changes in the cell surface antigens over time were compared with the incidence of bacteremia and pneumonia. Although the percentages of CD16+ CD11+ neutrophils were suppressed in almost all patients, the changes which occur in each individual patient rather than the actual values appear to be of major importance. Patients developing bacteremia or pneumonia displayed a significant reduction in both the percentage and absolute number of CD16+ CD11+ neutrophils compared to their preinfection values. The values did not increase until the infections were completely cleared. Patients remaining free of bacteremia or pneumonia usually had lower than normal percentages of CD16+ and CD11+ neutrophils with no predictable pattern being noted. The percentage of CD35+ neutrophils dropped within 1 week following thermal injury in all patients but did not correlate with the onset of infections.

Antigens, Differentiation↗
PubMed1990

The process of microbial translocation.

The process of microbial translocation was studied using Candida albicans, Escherichia coli, or endotoxin instilled into Thiry-Vella loops of thermally injured guinea pigs and rats. Translocation of C. albicans occurred by direct penetration of enterocytes by a unique process different from classical phagocytosis. Translocation between enterocytes was not observed. Internalization was associated with a disturbance of the plasma membrane and brush border, but most internalized organisms were not surrounded by a plasma membrane. Passage of the candida into the lamina propria appeared to be associated with disruption of the basal membrane with extrusion of cytoplasm of the cell and candida. Organisms in the lamina propria were commonly phagocytized by macrophages but also were found free in lymphatics and blood vessels. Translocation of E. coli and endotoxin also occurred directly through enterocytes rather than between them, but translocated endotoxin diffused through the lamina propria and muscular wall of the bowel wall by passing between rather than through the myocytes. These descriptive phenomena provide new insight into the role of the enterocyte and intestinal immune cells in the translocation process.

Animals↗
PubMed1990

The effect of dietary fatty acids on response to Pseudomonas infection in burned mice.

Since fatty acids influence prostaglandin synthesis, and since both fatty acids and prostaglandins modulate immune function, we investigated the hypothesis that manipulation of dietary fats would affect survival after infection in a murine burn model. Mice were fed for 2 to 3 weeks with diets containing different types and amounts of fat. They were then subjected to a 20% flame burn and infected with Pseudomonas aeruginosa. Survival in the group fed 40% of total calories as fish oil had significantly higher mortality than those fed safflower oil. This difference was not noted at lower fat levels. Similar groups of animals were sacrificed the day after injection. Splenic macrophage production of PGE2 was significantly lower in the fish-oil group, but production of LTB4 and TXB2 were not affected. In vitro tests of T- and B-cell function were not different amongst groups. We conclude that manipulation of dietary fats can alter outcome in this murine model of infection after thermal injury.

Animals↗
PubMed1990

The effect of free radical scavengers on outcome after infection in burned mice.

Thermal injury generates free radicals from various cellular populations, and modulation of free radical activity with scavengers may improve outcome. Balb/c mice were infected with Ps. aeruginosa the day after burn injury and mortality rates observed. Tocopherol was given by gavage daily for 4 days starting 2 days before burn. Survival was improved in the groups receiving 25 and 250 IU/kg compared to control. In other groups, tocopherol was given after burn, but mortality rates were not changed. Treatment with the oxygen radical scavengers ascorbic acid, and a combination of superoxide dismutase and catalase had no effect on mortality. We conclude that ascorbic acid, superoxide dismutase, and catalase do not appear to benefit survival after thermal injury and infection in this murine model. Tocopherol given in high doses of at least 25 IU/kg by gavage preceding injury and continued thereafter for 2 days did improve survival, but this benefit was not seen if tocopherol was not started until after injury.

Animals↗
PubMed1989

Surface aminopeptidase activity of human lymphocytes. I. Biochemical and biologic properties of intact cells.

Surface aminopeptidase activity in intact lymphocytes was studied and was shown to have the following properties when alanine-p-nitroanilide was used as substrate: 1) The activity was surface associated and not secreted as determined by extracellular location of product and the effect of proteases and diazotized sulfanilic acid on enzyme activity. 2) The enzyme activity was shown to have a pH optimum of 7.4 to 8.0. 3) Enzyme activity was shown to be inhibited by amastatin, bestatin, and 1,10 phenanthroline. Inhibition by amastatin consisted of a high-affinity component (Ki = 3.5 x 10(-6) M) which accounted for approximately 20% of the total activity and a low-affinity component (Ki = 3.5 x 10(-5) M) which accounted for the remainder suggesting that two forms of aminopeptidase exist. Only a single component of inhibition was seen with bestatin (Ki = 3.5 x 10(-6) M) and 1,10 phenanthroline (Ki = 2.0 x 10(-4) M) which accounted for 80 and 90% of the total enzyme activity, respectively. Unlike the competitive inhibitors bestatin and amastatin, inhibition by 1,10 phenanthroline was shown to be non-competitive. Finally, surface aminopeptidase activity essentially doubled in the presence of PHA (10 micrograms/ml) or Con A (10 micrograms/ml), at 72 h. This enhancing effect was shown to be dose dependent, time dependent, and mitogen dependent and correlated with the cellular state of activation as determined by [3H]TdR incorporation.

Aminopeptidases↗
PubMed1989

Immunoregulation of transfusion-induced immunosuppression with inhibitors of the arachidonic acid metabolism.

To further define the role of arachidonic acid (AA) metabolites in transfusion-induced immunosuppression (TII), the effects of pharmacological manipulation of AA metabolism were examined in a rodent model. If the prostaglandins of the E series are mediators of TII, as has been recently hypothesized, then inhibition of cyclooxygenase (indomethacin) should abrogate whereas inhibition of lipoxygenase (nordihydroguaiaretic acid [NDGA]), or thromboxane synthetase (4-63557A) could potentiate the transfusion effect. Lewis rats received donor-specific transfusions from Buffalo rats in conjunction with one of the above inhibitors. Two weeks later they received intraabdominal Buffalo heart allografts or were used for one-way mixed lymphocyte reactions. Cyclooxygenase inhibition partially abrogated TII with shortened cardiac allograft survival. Lipoxygenase inhibition augmented TII, with depression of MLR and prolongation of allograft survival. Thromboxane synthetase inhibition had no effect. These results indicate that AA metabolites play a role in TII, and that immunoregulation via pharmacological manipulation of AA metabolism is possible.

Adjuvants, Immunologic↗
PubMed1988

Degradation of thymopentin by human lymphocytes: evidence for aminopeptidase activity.

Thymopentin (Arg-Lys-Asp-Val-Tyr) was shown to be degraded in vitro by human lymphocytes into two main fragments; the tetrapeptide Lys-Asp-Val-Tyr and the tripeptide Asp-Val-Tyr. Degradation products were identified by HPLC and amino-acid analysis. Analysis of the time-course of degradation revealed a 'stepwise' degradative event beginning at the N-terminal. The degradation of thymopentin after the first 10 min, as well as the formation of the tetrapeptide (5-30 min) were essentially curvilinear. Degradation of the tripeptide, was linear. Upon screening a panel of compounds that inhibit enzymatic activity, bestatin, amastatin and 1,10-phenanthroline were shown to be the most effective. Bestatin and amastatin caused an 85-90% inhibition of thymopentin degrading activity with IC50 values of 7.1 x 10(-6) M and 4.5 x 10(-9) M, respectively. 1,10-Phenanthroline completely inhibited the degradative process with an IC50 of 2 x 10(-4) M. When the tetrapeptide Lys-Asp-Val-Tyr was used as the starting substrate, similar IC50 values were seen for amastatin, bestatin and 1,10-phenanthroline. The importance of divalent metal ions in the degradative event was demonstrated not only by the effect of 1,10-phenanthroline, but also by the ability of Zn2+ and Co2+ to reverse the inhibition of 1,10-phenanthroline (at its IC50) to activities near control values (no inhibitor). These data strongly suggest that an aminopeptidase(s) is responsible for the degradative activity.

Aminopeptidases↗
PubMed1988

The synergistic effect of low-dose cyclosporine and fluocinolone acetonide on the survival of rat allogeneic skin grafts.

Both CsA and topical FA can prolong the survival of skin allografts under the proper conditions. This study was performed to determine if there is a synergistic effect between these two compounds. Buf (RT1b) rat split-thickness skin grafts were transplanted onto the backs of Lew (RT1l) rats. The MST for the control group was 9.89 +/- 0.35 days. In rats given oral CsA, 2.5 or 5 mg/kg, daily from the second day of grafting, the MST was 16.0 +/- 1.9 and 13.6 +/- 0.4 days (blood CsA levels were 166 +/- 20 and 640 +/- 32 ng/ml at the time of rejection, respectively. Topical FA applied daily beginning 72 hr after grafting resulted in a MST of 24.1 +/- 3.6 days. When both topical FA and 5 mg/kg oral CsA were used, the allograft survival time was more than 100 days in 4 of 7 animals. When oral CsA 2.5 mg/kg was combined with topical CsA and FA, the allograft rejection was delayed until 50 days postgrafting in four of six animals. The synergistic effects of oral CsA and topical FA is significant, and thus allows for the use of a subtherapeutic dosage of each compound and provides a potentially safe means for prolonging skin allograft survival.

Animals↗
PubMed1988

The prolongation of skin allograft survival by topical use of cyclosporine A.

The absorption of CsA applied topically on normal or grafted skin was studied. When care was taken to prevent the rat from ingesting the CsA off their backs, the CsA blood levels was about 100 ng/mL or less, a suboptimal level to prevent rejection. The mean survival time of BUF grafts topically treated with 12 mg CsA/d was still significantly prolonged from 9.8 +/- 0.4 to 12.0 +/- 0.3 days. In bilateral grafting experiments where one graft was treated with CsA and one was not, the treated graft survived longer. Both grafts survived significantly longer than control animals with single grafts. These findings indicate that there is both a systemic and local immunosuppressive effect of topical CsA.

Administration, Topical↗