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M Bessler

Publications and source records attributed to M Bessler.

At least 19 recordsLinked to original sources
PubMed2000

Lymphocyte proliferation in mice after a full laparotomy is the same whether performed in a sealed carbon dioxide chamber or in room air.

PURPOSE: Our laboratory has demonstrated that significantly more cell-mediated immunosuppression occurs after full laparotomy than after either anesthesia control or carbon dioxide (CO2) pneumoperitoneum. We further demonstrated that the postoperative immunosuppression is related to the length of the incision. Other investigators believe that the immunosuppression observed after laparotomy is caused by peritoneal exposure to small amounts of lipopolysaccharide found in circulating air. They believe that the better-preserved immune function associated with laparoscopic surgery results from the avoidance of air contamination of the peritoneal cavity. To investigate this hypothesis, we determined and compared postoperative lymphocyte proliferation rates after (a) laparotomy in room air, (b) laparotomy in a CO2 chamber, (c) CO2 insufflation in a murine model, and (d) anesthesia alone. METHODS: Female C3H/He mice (n = 21) were divided randomly into four groups: (a) anesthesia control, (b) air laparotomy, (c) CO2 laparotomy, and (d) CO2 insufflation. The control mice underwent no procedure. The group 2 animals underwent a full midline incision (xiphoid to pubis) and exposure to room air for 20 min and then were clipped closed. The group 3 mice underwent a full midline incision in a sealed CO2 chamber for 20 min, and the group 4 mice insufflation with CO2 gas at 4 to 6 mm Hg for 20 min. Splenocytes were harvested from all the animals on day 2 after the interventions. Lymphocyte proliferation then was assessed using the nonradioactive colorimetric MTS/PMS system 72 h after concanavalin-A stimulation. RESULTS: There was no significant difference in lymphocyte proliferation between the air and CO2 laparotomy groups. Lymphocyte proliferation in the anesthesia control and CO2 insufflation groups was significantly higher than in both the air laparotomy (p<0.05) and CO2 laparotomy (p<0.05) groups (p values by Tukey-Kramer test). There was no significant difference between the anesthesia control and CO2 pneumoperitoneum groups. CONCLUSIONS: Our results suggest that full laparotomy performed in a sealed CO2 chamber compared to room air laparotomy resulted in similar suppression of lymphocyte proliferation. Furthermore, no significant suppression of lymphocyte proliferation was observed in the CO2 pneumoperitoneum group. These results, with regard to lymphocyte proliferation rates, refute the hypothesis that postoperative immunosuppression is related to air exposure and support the alternative hypothesis that immunosuppression is related to incision length.

Air↗
PubMed2000

Time course of differences in lymphocyte proliferation rates after laparotomy vs CO(2) insufflation.

BACKGROUND: Our laboratory has previously demonstrated that cell-mediated immune function is significantly more suppressed after both laparotomy and laparoscopic-assisted bowel resection than after peritoneal insufflation or open bowel resection, as assessed by delayed-type hypersensitivity (DTH) response. The purpose of this study was to further evaluate cell-mediated immunity by examining lymphocyte proliferation rates after laparotomy vs CO(2) insufflation. METHODS: Female Balb/C mice (n = 75) were randomly divided into the following three groups: (a) anesthesia control (A/C), (b) CO(2) insufflation (INS), and (c) sham laparotomy (OPEN). The A/C group mice underwent no procedure. The INS group underwent insufflation with CO(2) gas at 4-6 mmHg for 20 min. The OPEN group underwent a midline incision from xiphoid to pubic symphysis, which was clipped closed after 20 min. Splenocytes were obtained via splenic harvest and lymphocyte isolation on postoperative days (POD) 1, 2, 3, 4, and 8. Lymphocyte proliferation was determined by a nonradioactive colorimetric MTS/PMS assay 72 h after concanavalin A stimulation. RESULTS: The laparotomy group's lymphocyte proliferation rates were significantly lower than both the control and the insufflation groups on POD 2, POD 3, and POD 4. On POD 1 and POD 8, there were no significant differences in lymphocyte proliferation among the three groups. No differences were found between the control and insufflation groups at any point. CONCLUSIONS: After stimulation, lymphocytes proliferate at a lower rate after laparotomy than after CO(2) insufflation. Significant differences in lymphocyte proliferation rates between groups persist at least through POD 4. By POD 8, the mean lymphocyte proliferation rate in the laparotomy group was back to the baseline level. Our results suggest greater immunosuppression after sham laparotomy than after CO(2) insufflation.

Animals↗
PubMed1999

Increased sensitivity to complement and a decreased red blood cell life span in mice mosaic for a nonfunctional Piga gene.

The gene PIGA encodes one of the protein subunits of the alpha1-6-N acetylglucosaminyltransferase complex, which catalyses an early step in the biosynthesis of glycosyl phosphatidylinositol (GPI) anchors. PIGA is somatically mutated in blood cells from patients with paroxysmal nocturnal hemoglobinuria (PNH), leading to deficiency of GPI-linked proteins on the cell surface. To investigate in detail how inactivating mutations of the PIGA gene affect hematopoiesis, we generated a mouse line, in which loxP-mediated excision of part of exon 2 occurs on the expression of Cre. After crossbreeding with EIIa-cre transgenic mice, recombination occurs early in embryonic life. Mice that are mosaics for the recombined Piga gene are viable and lack GPI-linked proteins on a proportion of circulating blood cells. This resembles the coexistence of normal cells and PNH cells in patients with an established PNH clone. PIGA(-) blood cells in mosaic mice have biologic features characteristic of those classically seen in patients with PNH, including an increased sensitivity toward complement mediated lysis and a decreased life span in circulation. However, during the 12-month follow-up, the PIGA(-) cell population did not increase, clearly showing that a Piga gene mutation is not sufficient to cause the human disease, PNH.

Animals↗
PubMed1999

X inactivation and somatic cell selection rescue female mice carrying a Piga-null mutation.

A somatic mutation in the X linked PIGA gene is responsible for the deficiency of glycosyl phosphatidylinositol (GPI)-anchored proteins on blood cells from patients with paroxysmal nocturnal hemoglobinuria. No inherited form of GPI-anchor deficiency has been described. Because conventional Piga gene knockout is associated with high embryonic lethality in chimeric mice, we used the Cre/loxP system. We generated mice in which two loxP sites flank part of Piga exon 2. After crossbreeding with female mice of the EIIa-cre strain, the floxed allele undergoes Cre-mediated recombination with high efficiency during early embryonic development. Because of X chromosome inactivation, female offspring are mosaic for cells that express or lack GPI-linked proteins. Analysis of mosaic mice showed that in heart, lung, kidney, brain, and liver, mainly wild-type Piga is active, suggesting that these tissues require GPI-linked proteins. The salient exceptions were spleen, thymus, and red blood cells, which had almost equal numbers of cells expressing the wild-type or the recombined allele, implying that GPI-linked proteins are not essential for the derivation of these tissues. PIGA(-) cells had no growth advantage, suggesting that other factors are needed for their clonal dominance in patients with paroxysmal nocturnal hemoglobinuria.

Animals↗
PubMed1999

Tumor proliferative index is higher in mice undergoing laparotomy vs. CO2 pneumoperitoneum.

PURPOSE: Our laboratory has previously shown that tumors are more easily established and grow larger after laparotomy vs. laparoscopy. The purpose of this study was to better characterize these differences in tumor growth by assessing tumor cell proliferation via the proliferating cell nuclear antigen assay, which has been shown to be a reliable marker of cellular proliferation. METHODS: Female C3H/He mice (N = 40) were inoculated intradermally in the dorsal skin with 10(6) cultured mouse mammary carcinoma cells <1 hour before interventions. Anesthesia control mice underwent no procedure. Laparotomy group mice had a midline incision from xiphoid to pubis that was closed after 20 minutes. Insufflation group mice underwent CO2 pneumoperitoneum (4-6 mmHg) for 20 minutes. On postoperative Day 6, tumors were excised from one-third of the mice in each group, and from the remaining mice on postoperative Day 12. Sections were made and stained immunohistochemically for proliferating cell nuclear antigen, and the proliferative index of each tumor was determined by taking the average of proliferating cell nuclear antigen-positive cells in five high-power fields (x450), counted in a blinded fashion with the aid of an optical grid. RESULTS: On postoperative Day 6, the mean proliferative index for the laparotomy group was significantly higher than those for both the insufflation (P < 0.04) and the control (P < 0.001) groups. Of note, the proliferative index of the insufflation group was significantly higher than that of the control (P < 0.01) group. Similarly, on postoperative Day 12, the mean proliferative index for the laparotomy group was significantly higher than for both the insufflation (P < 0.05) and the control (P < 0.005) groups. The proliferative index in the insufflation group was also significantly higher than that of the control (P < 0.04) group. CONCLUSIONS: We have demonstrated that there is a significantly higher rate of tumor cell proliferation with the mouse mammary carcinoma cell tumor line after laparotomy than after pneumoperitoneum or anesthesia alone at two postoperative times. Additionally, insufflation alone increases postoperative tumor cell proliferation but to a lesser extent than laparotomy. The mechanism underlying these findings is unclear.

Animals↗
PubMed1999

Peritoneal irrigation with povidone-iodine solution after laparoscopic-assisted splenectomy significantly decreases port-tumor recurrence in a murine model.

PURPOSE: The development of port-wound tumor recurrences has raised questions regarding the safety of laparoscopic methods for the resection of malignancies. The cause and the incidence of abdominal-wall tumor recurrences remain unknown. It is also not clear how to avoid or lower the incidence of port-tumor recurrences. The purpose of the current study was to determine the impact of abdominal irrigation with povidone-iodine on the port-wound tumor incidence in a murine model. METHODS: A splenic tumor model was used for this study. To establish splenic tumors, female BALB/c mice (N = 48) were given subcapsular splenic injections of a 0.1 ml suspension containing 10(5) C-26 colon adenocarcinoma cells via a left-flank incision at the initial procedure. Seven days later, the animals with isolated splenic tumors (100 percent) were randomly assigned to one of three groups: 1) control, 2) saline irrigation (saline), or 3) povidone-iodine irrigation. All animals underwent laparoscopic mobilization of the spleen using a three-port technique, intra-abdominal crushing of the tumor, followed by an extracorporeal splenectomy via a subcostal incision. No irrigation was performed for control group animals. In the saline irrigation group, the subcostal incision was closed and pneumoperitoneum was re-established. The abdominal cavity was irrigated with 5 ml of normal saline for 60 seconds before instrument removal. In the povidone-iodine irrigation group, similar abdominal irrigation was performed, using 0.25 percent povidone-iodine. Attempts were made to recover completely the irrigation for both irrigation groups. Seven days after the splenectomy, animals were killed and inspected for abdominal-wall tumor implants. RESULTS: There were significantly more animals with at least one port-tumor recurrence in the control group than in the povidone-iodine group (P = 0.007). Although not statistically significant, the number of animals with port-wound tumors was higher in the saline group than in the povidone-iodine group (P < 0.08). There was no significant difference between the saline group and the control group. When each port site was considered independently, the incidence of port-wound tumors (number of ports with tumors per total number of ports) was significantly lower in the povidone-iodine group than in both the control (P = 0.00001) and saline groups (P = 0.03). The incidence of port-wound tumors was also significantly lower in the saline group compared with the control group incidence (P = 0.03). CONCLUSIONS: Abdominal irrigation with dilute povidone-iodine solution significantly reduced the number of animals with port-tumor recurrences. Abdominal irrigation with saline was also effective in reducing the incidence of port-wound tumor formation when each port was considered separately. However, povidone-iodine irrigation was much more effective than saline irrigation in preventing port-wound tumor formation.

Adenocarcinoma↗
PubMed1999

Increased tumor establishment and growth after open vs laparoscopic surgery in mice may be related to differences in postoperative T-cell function.

BACKGROUND: Previous work has demonstrated that cell-mediated immune function in rats is better preserved after laparoscopic than open surgery. We have also shown that tumors are more easily established in mice and grow larger after sham laparotomy than after pneumoperitoneum. The purpose of this study is to determine if the functional status of the cell-mediated immune system influences postoperative tumor growth. METHODS: Immunocompetent (study 1) and T-cell deficient athymic (study 2) mice were injected with mouse mammary carcinoma cells in the dorsal skin. Mice then underwent either no procedure, midline laparotomy, or carbon dioxide pneumoperitoneum. Tumor masses on postoperative day 12 were compared. RESULTS: In immunocompetent mice, laparotomy group tumors were nearly twice as large as laparoscopy group tumors (p < 0.02), which were 1.5 times as large as control group tumors (NS). In the athymic model, however, differences between the sham laparotomy and pneumoperitoneum groups were lost (p > 0.5). Tumors grew much larger in the athymic control mice than in the immunocompetent control mice (p < 0.01). CONCLUSION: We conclude that T-cell function plays a significant role in host containment of mouse mammary carcinoma and in the mechanism of differences in tumor growth observed after laparotomy and pneumoperitoneum.

Animals↗
PubMed1999

Delayed-type hypersensitivity response is better preserved in mice following insufflation than after laparotomy.

BACKGROUND: Our laboratory has previously used pig and rat models to demonstrate that delayed-type hypersensitivity (DTH) response to an antigen challenge is suppressed following laparotomy compared to insufflation. The purpose of this study was to develop a practical and reliable mouse DTH model that could be used in future studies to test immunomodulating drugs and therapies. METHODS: Female C3H/HeN mice (n = 100) were given three serial DTH challenges of 25 microl of 4 mg/ml phytohemagglutinin (PHA) 12 days before the test procedure, immediately following the test procedure, and on the 2nd postoperative day. All challenges were administered via subcutaneous injection in alternating footpads. The thickness of the footpad was determined with electronic calipers immediately prior to injection and 24 h following injection in a blinded fashion. The difference in thickness represents the response. On the day of the procedure, mice were randomized into the following three groups: (a) control (AC), (b) insufflation (INS), and (c) open (OPEN). AC mice underwent no procedure. INS mice underwent CO(2) insufflation at 2-4 mmHg for 20 min. OPEN mice underwent a midline incision from xiphoid to pubis that was closed after 20 min. Data were analyzed using ANOVA and Tukey-Kramer tests to determine differences between groups. RESULTS: Preoperatively, there were no significant differences among the three groups. On POD1, the OPEN group had significantly less response than both the AC and INS groups. On POD3, there were significant differences between the OPEN group and both the INS and AC groups. There was no significant difference between the AC and INS group at any time. CONCLUSIONS: In conclusion, a DTH mouse model has been established that allows serial assessment of cell-mediated immune function. This model can be used to study immune function after open and minimal access procedures in a simple and cost-effective manner.

Animals↗
PubMed1998

New somatic mutation in the PIG-A gene emerges at relapse of paroxysmal nocturnal hemoglobinuria.

We report a detailed longitudinal study of the first patient to be treated (in 1973) for paroxysmal nocturnal hemoglobinuria (PNH) with syngeneic bone marrow transplantation (BMT). The patient subsequently relapsed with PNH in 1983, and still has PNH to date. Analysis of the PIG-A gene in a recent blood sample showed in exon 6 an insertion-duplication causing a frameshift. Polymerase chain reaction (PCR) amplification of the PIG-A exon 6 from bone marrow (BM) slides obtained before BMT showed that the duplication was not present; instead, we found several single base pair substitutions in exons 2 and 6. Thus, relapse of PNH in this patient was not due to persistence of the original clones; rather, it was associated with the emergence of a new clone. These findings support the notion that the BM environment may create selective conditions favoring the expansion of PNH clones.

Adolescent↗
PubMed1998

The spectrum of somatic mutations in the PIG-A gene in paroxysmal nocturnal hemoglobinuria includes large deletions and small duplications.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal blood disorder characterized by chronic hemolysis with hemoglobinuria and venous thrombosis. PNH clones arise through somatic mutations in the X-linked PIG-A gene that occur in early hematopoietic stem cells. Here we report 28 previously undescribed mutations; we confirm that somatic mutations are spread throughout the entire coding region of the PIG-A gene and that the majority are frameshift mutations producing a non-functional PIG-A protein (PIG-A(o)). In addition, we found 1 total deletion of the PIG-A gene, and 2 short nucleotide duplications. Although mutations are spread throughout the entire coding region, we observe more missense mutations in exon 2 than in the other exons. The increasing number of identified missense PIG-A mutations should help elucidate structure-function relationships in the PIG-A protein.

DNA Mutational Analysis↗
PubMed1998

Colon adenocarcinoma and B-16 melanoma grow larger following laparotomy vs. pneumoperitoneum in a murine model.

PURPOSE: Mouse mammary carcinoma tumors are established more easily and grow larger after sham laparotomy and open bowel resection than after CO2 pneumoperitoneum and laparoscopic-assisted bowel resection. The purpose of this study was to determine whether similar differences in tumor growth would be found when sham laparotomy and pneumoperitoneum were compared for the colon-26 mouse adenocarcinoma and B-16 mouse melanoma tumor lines. METHODS: In all three studies, a high-dose injection of tumor cells was used, which resulted in tumors in almost all control mice. In Study 1, female BALB/C mice (n = 127) were injected intradermally in the dorsal skin with 10(6) colon-26 cells in a 0.1-ml volume before interventions. In Study 2, female C57 BL/6 mice (n = 140) were inoculated similarly with 10(6) B-16 melanoma cells. Study 2 consisted of three separate trials conducted on different days. Study 3 was performed because considerable differences in mean tumor size were observed in each of these trials. In Study 3, the B16 experiment was repeated with a larger n (n = 82) on a single day. In each study, after tumor cell injections, mice were randomly assigned to one of three groups: 1) anesthesia control (no procedure); 2) full laparotomy (4-cm midline incision x 20 minutes, staple closure); or 3) CO2 pneumoperitoneum (4-6 mmHg X 20 minutes). Tumors were excised and weighed on postoperative day 12. RESULTS: In Studies 1 and 3, mean tumor sizes of the laparotomy groups were significantly larger than both the control group and pneumoperitoneum group lesions (P values by Student's t-test). In Study 2, laparotomy group tumors, although significantly larger than control group lesions, were not significantly larger than pneumoperitoneum group tumors. For all three studies, there was no significant difference between mean tumor sizes of the pneumoperitoneum and control groups. CONCLUSION: Both colon-26 adenocarcinoma and B-16 melanoma tumors grow larger after laparotomy than after pneumoperitoneum in a murine model. The mechanism of these postoperative tumor growth differences remains to be elucidated.

Adenocarcinoma↗
PubMed1998

Abdominal wound tumor recurrence after open and laparoscopic-assisted splenectomy in a murine model.

PURPOSE: The cause of abdominal wall tumor recurrences after laparoscopic surgery for cancer remains unknown. A recent study from our laboratory using a murine splenic tumor model suggests that poor surgical technique (i.e., crushing of the tumor) and not the CO2 pneumoperitoneum is responsible for port wound tumors. However, in that experiment no actual laparoscopic procedure or manipulation was performed. The purpose of the current study was to determine the rate of abdominal wound tumors after laparoscopic-assisted splenectomy performed via a CO2 pneumoperitoneum vs. open splenectomy using the mouse splenic tumor model. METHODS: To establish splenic tumors, female BALB/c mice (N=72) were given subcapsular splenic injections of a 0.1-ml suspension containing 10(5) C-26 colon adenocarcinoma cells via a left flank incision at the initial procedure. Eight days later, animals were randomized into one of two groups: 1) laparoscopic-assisted splenectomy, or 2) open splenectomy. Laparoscopic-assisted splenectomy animals had three laparoscopic ports placed and then underwent laparoscopic mobilization of the spleen under a CO2 pneumoperitoneum followed by extracorporeal splenectomy via a subcostal incision. Group 2 animals underwent open splenectomy via a subcostal incision after three port incisions were made in the same locations as for laparoscopic-assisted splenectomy mice. The incision was closed after 20 minutes in both groups. Ten days later, the mice were killed and inspected for abdominal wall tumor implants. The experiment was performed via two separate trials. RESULTS: When results of the two trials were combined, there was no significant difference in the incidence of animals in each group with at least 1 port tumor (open, 21 percent; laparoscopic-assisted splenectomy, 33 percent; P=0.14). However, the overall incidence of port site tumors (number of ports with tumors/total number of ports for each group) was significantly higher in the laparoscopic-assisted splenectomy group than in the open group (20 vs. 7 percent; P=0.01). The subcostal incisional tumor recurrence rate was also higher in the laparoscopic-assisted splenectomy group (50 vs. 21 percent; P=0.02). as was the perioperative mortality rate (21 vs. 7 percent; P=0.08). Results of the two individual trials were also considered separately. The incidence of port wound tumors decreased significantly from the first to the second laparoscopic-assisted splenectomy trial (36 vs. 9 percent; P=0.003), although the incidence of tumors at the subcostal incision and the mortality rate for the two laparoscopic-assisted splenectomy group trials were not significantly different. The open group tumor incidences did not change from trial to trial. CONCLUSIONS: Overall, significantly more port and incisional tumors were noted in the laparoscopic-assisted group. Although not statistically significant, mortality rate of the laparoscopic-assisted group was higher than the open group. The reasons for these findings are unclear. Laparoscopic mobilization was quite difficult and required excessive splenic manipulation, which may have liberated tumor cells from the primary tumor and facilitated port tumor formation. With increased experience, less manipulation was required to complete mobilization. Of note, the incidence of port tumors in the laparoscopic-assisted splenectomy group decreased significantly from the first to the second trials; therefore, it is possible that surgical technique is a factor in port tumor formation. However, the persistently high tumor incidence at the subcostal incision site argues against the hypothesis that the second trial's laparoscopic mobilizations were less traumatic. The CO2 pneumoperitoneum may also be a factor. Further studies are warranted to clarify these issues.

Abdominal Neoplasms↗
PubMed1998

The effects of elevated intraabdominal pressure, hypercarbia, and positioning on the hemodynamic responses to laparoscopic colectomy in pigs.

BACKGROUND: This study investigated three factors postulated to be sources of physiological stress in laparoscopic surgery: hypercarbia, elevated intraabdominal pressure, and the steep Trendelenburg position. Our research was designed to define the effects of each of these potential stressors on hemodynamic responses observed during laparoscopic colectomy in pigs. METHODS: Twenty-four pigs were randomized into the following four groups, based on the method for obtaining surgical exposure while a colectomy or laparoscopic-assisted colectomy was performed: Open surgery (n = 6), CO2 pneumoperitoneum (n = 6), Helium pneumoperitoneum (n = 6), and abdominal wall Lifter (n = 6). The animals were paralyzed with minute ventilation adjusted. All animals underwent extensive pulmonary and hemodynamic monitoring with measurements of the following parameters: RR, Vt, minute ventilation, O2, sat, ETCO2, PVR, HR, MAP, CO, PAP, CVP, PCWP, SV, LVSWI, DO2, and VO2. The laparoscopic pigs were placed in the steep Trendelenburg position during surgery. RESULTS: The effect of a CO pneumoperitoneum was to increase PaCO2 PVR and cause an acidemia that could not be prevented by an increase in minute ventilation. Elevated intraabdominal pressure decreased UO. Both pneumoperitoneum groups had a fourfold increase in IVCP, a measure of intraabdominal pressure. Some of this increase was due to placement into the Trendelenburg position; IVCP increased to a lesser degree in the Lifter group. The steep Trendelenburg position caused significant increases in PAP, CVP, and PCWP; however, a contributory effect of elevated intraabdominal pressure cannot be ruled out. None of these procedures had any significant effect on the HR or MAP. There was a significant increase in CO in the CO2 and Lifter groups; however, when CO was controlled for HR effects, there was no significant effect on SV from any of these different procedures. LVSWI, DO2, and VO2 were not affected by any of the different exposure methods. CONCLUSIONS: The effects of laparoscopic surgery and open surgery on hemodynamic responses are minimal, and no one method is superior to another when performed in pigs that are healthy, hydrated, and hyperventilated to keep ETCO2 < 40. However, since elderly and sick patients have a lower threshold for physiologic decompensation, we can infer that the small hemodynamic changes noted in this study might become significant factors when surgery is performed on compromised patients. The finding that an abdominal wall lifting device causes the fewest metabolic and hemodynamic effects makes its use an important consideration when performing laparoscopic surgery in patients with cardiopulmonary compromise, hemodynamic instability, or any preexisting renal insufficiency.

Abdomen↗
PubMed1998

The effect of peritoneal air exposure on postoperative tumor growth.

BACKGROUND: Previous work has demonstrated that cell-mediated immune function is better preserved in rodents after laparoscopic than open surgery. The cause of this laparotomy-related immunosuppression is unclear. Some investigators have attributed it to the length of the incision; others, to peritoneal air exposure. It has also been shown that tumors in mice are more easily established and grow larger after sham laparotomy than after pneumoperitoneum. Lastly, the differences in tumor growth have been shown to be, at least in part, attributable to the immunosuppression that occurs after laparotomy. The purpose of this study was to determine if air pneumoperitoneum, presumably via immunosuppression related to peritoneal air exposure, is associated with increased tumor growth in the postoperative period. METHOD: A total of 150 immunocompetent syngeneic mice received high-dose intradermal injections of mouse mammary carcinoma tumor cells. They were then randomized to undergo one of the following procedures: (a) anesthesia alone, (b) air insufflation (44 mm Hg), (c) CO2 insufflation, or (d) full laparotomy. No intraabdominal procedure was carried out. All procedures were 20 min long. After 12 days, the animals were killed and the mean tumor mass determined for each group. RESULTS: All animals grew tumors. There was no significant difference in the mean tumor size of the anesthesia control, CO2 insufflation, and air insufflation groups (p > 0.85 by ANOVA). However, the laparotomy group tumors were 1.5 times as large as those of the other three groups (p < 0.05 by ANOVA). CONCLUSIONS: In this model, air insufflation did not significantly affect postoperative tumor growth, nor did CO2 pneumoperitoneum. However, full laparotomy was associated with increased tumor growth.

Air↗
PubMed1998

Traumatic handling of the tumor independent of pneumoperitoneum increases port site implantation rate of colon cancer in a murine model.

BACKGROUND: Reports of port site tumor recurrences after laparoscopic-assisted resection of colon tumors have raised concerns about the safety of laparoscopic cancer surgery. Tumor cell suspension studies in animals have implicated the CO2 pneumoperitoneum (pneumo) in the etiology of port tumors. Unfortunately, in several ways, the cell suspension model is unrealistic and does not permit assessment of how tumor cells become liberated from the primary tumor. The purpose of this study was to establish a more realistic splenic tumor model and to determine the relative importance of the CO2 pneumo and excessive surgical manipulation in the development of port site and incisional tumor recurrences. METHODS: Splenic tumors were established in female Balb/C mice (n = 134) via a subcapsular injection of 10(5) C-26 colon adenocarcinoma cells (0.1 ml volume) via a left-flank incision at the initial procedure. Ten days later, the animals were reexplored via a 1-cm left subcostal incision. Those with isolated splenic tumors (95%) were randomized into one of four groups: (a) control, (b) CO2 pneumo, (c) crushed tumor, or (d) crushed tumor with pneumo. Ports were placed in the left lower, right lower, and right upper quadrants of each mouse. In groups 1 and 2, the mice underwent a meticulously performed splenectomy; in groups 3 and 4, the tumor capsule was crushed intraabdominally prior to splenectomy. In groups 1 and 3, the subcostal incision was closed and the ports were removed after 15 min of anesthesia. Following splenectomy, group 2 and group 4 mice underwent closure of the subcostal incision and a 15-min CO2 pneumo (4-6 mm Hg) after which the ports were removed. Twelve days later, the mice were killed and examined for abdominal wall tumor implants. RESULTS: Significantly more animals in group 3 (crushed tumor) developed port site and incisional tumors than those in group 1 (control) (p < 0.002 for both comparisons). The same results were found when group 4 (crush plus pneumo) was compared to group 2 (pneumo) (p < 0.002 for both comparisons). Regarding the port wounds, when the ports are considered individually (number of ports with tumors/total number of ports for each group), there were significantly more port tumors in the two crush groups than in the noncrush groups. No significant differences were noted when the port site and incisional tumor rates for group 1 (control) and group 2 (pneumo) were compared or when the results for group 2 (crush) and group 4 (crush pneumo) were compared. CONCLUSIONS: A splenic tumor model was successfully established. When compared to meticulous technique, purposefully traumatic handling of the splenic tumor before resection resulted in significantly more port wound and incisional tumors. In contrast, the addition of a pneumo after splenectomy did not significantly influence the incidence of port tumors in either the "good" or the "poor" technique groups. These results suggest that surgical technique plays a larger role in the development of port site tumors than the CO2 pneumoperitoneum.

Adenocarcinoma↗
PubMed1998

Increased tumor establishment and growth after open vs laparoscopic bowel resection in mice.

BACKGROUND: Surgery can suppress immune function and facilitate tumor growth. Several studies have demonstrated better preservation of immune function following laparoscopic procedures. Our laboratory has also shown that tumors are more easily established and grow larger after sham laparotomy than after pneumoperitoneum in mice. The purpose of this study was to determine if the previously reported differences in tumor establishment and growth would persist in the setting of an intraabdominal manipulation. METHODS: Syngeneic mice received intradermal injections of tumor cells and underwent either an open or laparoscopic cecal resection. In study 1, the incidence of tumor development was observed after a low dose inoculum; whereas in study 2, tumor mass was compared on postoperative day 12 after a high-dose inoculum. RESULTS: In study 1, tumors were established in 5% of control mice, 30% of laparoscopy mice, and 83% of open surgery mice (p < 0.01 for all comparisons). In study 2, open surgery group tumors were 1.5 times as large as laparoscopy group tumors (p < 0.01), which were 1.5 times as large as control group tumors (p < 0.02). CONCLUSION: We conclude that tumors are more easily established and grow larger after open laparoscopic bowel resection in mice.

Animals↗
PubMed1998

General oncologic effects of the laparoscopic surgical approach. 1997 Frankfurt international meeting of animal laparoscopic researchers.

The results from the majority of the reviewed studies support the hypothesis that abdominal surgery, performed via either a large incision or CO2 pneumoperitoneum, systemically encourages tumor growth in the postoperative period. A full laparotomy incision appears to have a significantly greater effect than CO2 pneumoperitoneum on postoperative tumor growth. Whether the large tumor observed in the surgical groups are the result of increased tumor cell proliferation or diminished tumor cell death remains unclear. There is some evidence pointing to both mechanisms. The loss of the postoperative tumor growth differences between the open and pneumo animals in the athymic mouse experiment suggests that cell-mediated immune function plays a role in tumor containment. The proliferation study results, however, suggest that other stimulatory influence(s) are also at work. Clearly, much research needs to be done regarding the etiology of these tumor growth differences. Other tumor cell lines need to be studied, and investigations regarding tumor growth in an intra-abdominal location need be performed as well. This body of research suggests that the manner in which the surgeon gains access to the abdominal cavity may have an impact on the propensity of tumor cells to implant, survive, and grow in the period immediately after surgery. If true, this may be the most compelling justification for the use of minimally invasive techniques for the curative resection of malignancies. However, it remains to be proven that human tumors will demonstrate differences in tumor growth similar to those noted in some of these animals models. Furthermore, it is not all clear that slight differences in tumor growth postoperatively will translate into significant differences in long-term survival or recurrence rates. At first glance, the existence of port-site tumors would appear to contradict totally the conclusions of many studies discussed in this synopsis. If laparoscopic methods are associated with decreased rates of tumor growth and establishment, then why do port-site tumors form? This is a complex issue calling for discussion that goes far beyond the scope of this article. However, several brief comment on this topic follow. The etiology of port tumors is unknown, although traumatization of the tumor during mobilization, resection, or removal is likely to play a significant role in the liberation of tumor cells from the primary. A relatively small protective benefit, in terms of slower tumor growth rates in laparoscopic patients, will likely not be sufficient to prevent a large inoculum of viable tumor cells in an abdominal wound from establishing a metastasis. Furthermore, as suggested earlier, the systemic effects on tumor growth may be different from the local (i.e., intra-abdominal or abdominal wound) effects. Finally, the true incidence of port tumors remains unknown. It has not been definitively established that the laparoscopic wound tumor incidence is significantly higher than the open rate, although this is the assumption of most surgeons. Several relatively large recently published laparoscopic series have reported port tumor incidences of 0 to 1.2%, which is in the same "ballpark" as the 0.6 1.0% abdominal wound tumor incidences mentioned in several open colectomy series. Clearly, much more research in this area is needed to understand port tumors better and to reconcile the port tumor results with the systemic tumor growth benefits that may be associated with minimally invasive methods.

Animals↗