Biomedical subjects

S Casillas

Publications and source records attributed to S Casillas.

9 recordsLinked to original sources

PubMed2006

Neural gastrointestinal electrical stimulation enhances colonic motility in a chronic canine model of delayed colonic transit.

Neural gastrointestinal electrical stimulation (NGES) induces sequential contractions and enhances emptying in acute canine gastric and colonic models. This study was set to determine (i) the effect of NGES in a chronic canine model of delayed colonic transit and (ii) possible mechanism of action. Four pairs of electrodes were implanted in the distal colon of nine mongrel dogs. Delayed colonic transit was induced by diphenoxylate/atropine and alosetron. Transit was fluoroscopically determined by the rate of evacuation of radiopaque markers, and was tested twice in each dog, in random order, on and off stimulation. Two stimulation sequences, separated by 1 min, were delivered twice a day via exteriorized electrodes. Colonic manometry during stimulation was performed before and after intravenous (i.v.) injection of 1 mg of atropine. Complete evacuation of all markers was significantly shortened by NGES, from 4 days to 2 days, interquartile range 3-4 days vs 2-3 days, respectively, P = 0.016. NGES induced strong sequential contractions that were significantly diminished by atropine: 190.0 +/- 14.0 mmHg vs 48.7 +/- 19.4 mmHg, respectively (P < 0.001). NGES induces strong sequential colonic contractions and significantly accelerates movement of content in a canine model of delayed colonic transit. The effect is atropine sensitive.

Animals↗

PubMed2005

Long-term outcome after laparoscopic and open surgery for rectal prolapse: a case-control study.

BACKGROUND: Laparoscopic repair (LR) of rectal prolapse is potentially associated with earlier recovery and lower perioperative morbidity, as compared with open transabdominal repair (OR). Data on the long-term recurrence rate and functional outcome are limited. METHODS: Perioperative data on rectal prolapse in relation to all LRs performed between December 1991 and April 2004 were prospectively collected. The LR patients were matched by age, gender, and procedure type with OR patients who underwent surgery during the same period. Patients with previous complex abdominal surgery or a body mass index exceeding 40 were excluded from the study. Data on recurrence rate, bowel habits, continence, and satisfaction scores were collected using a telephone survey. RESULTS: A total of 111 patients (age, 56.8 +/- 18.1 years; female, 87%) underwent attempted LR. An operative complication deferred repair in two cases. Among the 111 patients, 42 had posterior mesh fixation, and 67 had sutured rectopexy (32 patients with sigmoid colectomy for constipation). Eight patients (7.2%) had conversion to laparotomy. Matching was established for 86 patients. The LR patients had a shorter hospital stay (mean, 3.9 vs 6.0 days; p < 0.0001). The 30-day reoperation and readmission rates were similar for the two groups. The rates for recurrence requiring surgery were 9.3% for LR and 4.7% for OR (p = 0.39) during a mean follow-up period of 59 months. An additional seven patients in each group reported possible recurrence by telephone. Postoperatively, 35% of the LR patients and 53% of the OR patients experienced constipation (p = 0.09). Constipation was improved in 74% of the LR patients and 54% of the OR patients, and worsened, respectively, in 3% and 17% (p = 0.037). The postoperative incontinence rates were 30% for LR and 33% for OR (p = 0.83). Continence was improved in 48% of the LR patients and 35% of the OR patients, and worsened, respectively, in 9% and 18% (p = 0.22). The mean satisfaction rates for surgery (on a scale of 0 to 10) were 7.3 for the LR patients and 8.1 for the OR patients (p = 0.17). CONCLUSIONS: The hospital stay is shorter for LR than for OR. Both functional results and recurrent full-thickness rectal prolapse were similar for LR and OR during a mean follow-up period of 5 years.

Abdomen↗

PubMed2003

Late abscess formation after spilled gallstones masquerading as a liver mass.

The most common complication during laparoscopic cholecystectomy is the spillage of stones into the abdominal cavity. Although spillage occurs in 30% of cases, the potential adverse effects of this event are rare and generally manifest within months. When complications do occur, however, they may cause significant morbidity for the patient. We report an unusual case in which an inflammatory mass mimicking a liver tumor developed 5 years after the stones had been lost during a laparoscopic cholecystectomy. We therefore urge all surgeons to make every attempt to retrieve gallstones from the abdominal cavity once they have been accidentally dropped.

Abdominal Abscess↗

PubMed1999

Hepatic tumor radioembolization in a rat model using radioactive rhenium (186Re/188Re) glass microspheres.

PURPOSE: The aim of this study was to fully characterize newly developed radioactive rhenium glass microspheres in vivo by determining their biodistribution, stability, antitumor effect, and toxicity after hepatic arterial injection in a syngeneic rat hepatoma model. The dose response of the tumors to increasing amounts of radioactive 186Re and 188Re microspheres was also determined. METHODS AND MATERIALS: Rhenium glass microspheres were made radioactive by neutron activation and then injected into the hepatic artery of Sprague-Dawley rats containing 1-week-old Novikoff hepatomas. The biodistribution of the radioactivity and tumor growth were determined 1 h and 14 days after injection. RESULTS: Examination of the biodistribution indicated a time-dependent, up to 7-fold increase in Novikoff hepatoma uptake as compared to healthy liver tissue uptake. After 14 days, the average T:L ratio was 1.97. Tumor growth in the rats receiving radioactive microspheres was significantly lower than in the group receiving nonradioactive microspheres (142% vs. 4824%, p = 0.048). Immediately after injection, 0.065% of the injected radioactivity was measured in the thyroid; it decreased to background levels within 24 h. CONCLUSION: Radioactive rhenium microspheres are effective in diminishing tumor growth without altering hepatic enzyme levels. The microspheres are safe with respect to their radiation dose to healthy tissue and radiation release in vivo and can be directly imaged in the body with a gamma camera. Furthermore, rhenium microspheres have an advantage over pure beta-emitting microspheres in terms of preparation and neutron-activation time. In sum, this novel radiopharmaceutical may provide an innovative and cost-effective approach for the treatment of nonresectable liver cancer.

Animals↗

PubMed1998

Vasopressin selectively increases 5-fluorouracil uptake by colorectal liver metastases following hepatic artery bolus infusion.

BACKGROUND: Poor drug uptake secondary to the hypovascularity of colorectal liver metastases may partially explain their limited response to hepatic artery chemotherapy. Vasoconstrictors can increase tumor perfusion but their effect on drug uptake has not been well-characterized. The aim of this study was to determine whether vasopressin could selectively increase tumor uptake of 5-FU. MATERIALS AND METHODS: A syngeneic rat model of colorectal liver metastases was used. Control group rats underwent a 60-s hepatic artery infusion of 14C-5-FU (30 mCi/150 microL). Treatment group rats had vasopressin (60 mIU/kg, dose determined in pilot study) added to the 14C-5-FU infusion. Mean systemic arterial pressure was minimally affected. Tumor:liver (T/L UR) and tumor center:periphery (C/P UR) 5-FU uptake ratios were determined using quantitative autoradiography techniques. Differences in tumor size (< or > 4 mm) and location (superficial vs deep) were accounted for. Statistical analysis was by repeated measures ANOVA (P = 0.01 significant). RESULTS: A total of 161 tumors in 18 rats was analyzed. T/L URs were significantly higher in the treatment group compared to controls for tumors <4 mm (1.72 +/- 0.14 vs 0.70 +/- 0.16, P <0.001), tumors >4 mm (0.99 +/- 0.15 vs 0.45 +/- 0.16, P = 0.01), deep tumors (1.17 +/- 0.13 vs 0.68 +/- 0.15, P = 0.01), and superficial tumors (1.54 +/- 0. 15 vs 0.47 +/- 0.17, P <0.001). C/P URs did not differ significantly between the groups. CONCLUSIONS: The results of this study show that vasopressin selectively enhances the uptake of 5-FU by colorectal liver metastases in a rat model of hepatic artery infusion. This may represent a promising strategy for improving tumor response rates and patient survival.

Animals↗

PubMed1997

Perfusion to colorectal cancer liver metastases is not uniform and depends on tumor location and feeding vessel.

Future effective therapies for hepatic metastases may depend on a better understanding of perfusion to these tumors. The purpose of this project was to define blood flow to colorectal cancer liver metastases using quantitative autoradiography (QAR). Liver tumors were established in F1 hybrids of WF x BN rats by intrasplenic injection of a DMH-induced rat colon adenocarcinoma. Rats underwent laparotomy 4-5 weeks later and [14C]iodoantipyrine (a radiotracer) was infused via the hepatic artery (HA) or portal vein (PV). Livers were harvested, frozen in liquid nitrogen, and sectioned at 20 microns through all tumors. QAR compared optical density of cross sections of tumors to surrounding normal liver tissue. Tumor:liver perfusion ratios (T/L PR) and tumor center:tumor periphery perfusion ratios (C/P PR) were calculated. All groups were analyzed with regard to tumor location and size. Seventy-seven tumors in 6 rats in the HA infusion group were analyzed; 74 tumors in 8 rats in the PV group were analyzed. Statistical analysis was by repeated measures analysis of variance. Mean HA T/L PR = 0.97 +/- 0.13, mean PV T/L PR = 0.25 +/- 0.11. Mean HA T/L PR for deep tumors was 1.38 +/- 0.17 and for superficial tumors was 0.57 +/- 0.15 (P < 0.01). Mean HA T/L PR for small tumors was 1.09 +/- 0.12 and for large tumors was 0.86 +/- 0.21 (P = 0.27). Mean PV T/L PR for deep tumors was 0.27 +/- 0.14 and for superficial tumors was 0.24 +/- 0.15 (P = 0.71). Mean PV T/L PR for small tumors was 0.31 +/- 0.15 and for large tumors was 0.20 +/- 0.14 (P = 0.54). Mean HA C/P PR = 1.15 +/- 0.15, mean PV C/P PR = 0.81 +/- 0.14 (P = 0.06). Mean HA C/P PR for small tumors was 1.37 +/- 0.16 and for large tumors was 0.92 +/- 0.17 (P = 0.01). Mean PV C/P PR for small tumors was 0.78 +/- 0.18 and for large tumors was 0.72 +/- 0.13 (P = 0.71). HA perfusion of tumors is significantly higher than PV perfusion compared to surrounding normal liver tissue. HA perfusion varies significantly depending on tumor location. There was a trend toward HA perfusion to the tumor center being slightly greater than to the periphery whereas the reverse was seen for PV perfusion. Tumor size did not affect overall perfusion but it did affect regional HA tumor perfusion.

Adenocarcinoma↗

PubMed1997

Adjuvant therapy for colorectal cancer: present and future perspectives.

In recent years, adjuvant therapy for colorectal cancer has advanced considerably. This article reviews these advances and provides an update of the most recent and ongoing trials. In 1990, adjuvant therapy became the "standard of care" for patients with Stage III colon cancer (Dukes C) in the United States. Recent clinical trial data indicate that adjuvant treatment may also be effective in patients with Stage II (Dukes B2) colon cancer. The combination of 5-fluorouracil plus leucovorin may slightly improve survival (5-10 percent) compared with the standard 5-fluorouracil plus levamisole combination. The three-drug regimen (5-fluorouracil plus levamisole plus leucovorin) is more toxic, with no superior effect on survival. Intraportal chemotherapy, although it may significantly improve patient survival, does not decrease the frequency of liver metastases. However, it is still a promising form of adjuvant therapy owing to its short treatment period and relatively equivalent effects in survival compared with that of systemic therapy. For patients with Stage II or Stage III rectal cancer, postoperative systemic 5-fluorouracil plus radiation therapy plus protracted venous 5-fluorouracil infusion is the most effective postoperative adjuvant regimen. However, results from several studies show that preoperative radiation alone or chemoradiation for advanced local rectal cancers might also be effective while also improving resectability, decreasing morbidity, and increasing the chance that a sphincter-sparing procedure may be performed. The role of leucovorin in rectal cancer remains to be determined. Immune therapies with agents such as interferon-alpha-2a, monoclonal antibody 17-1A, and autologous tumor vaccines are being assessed and could further improve survival.

Chemotherapy, Adjuvant↗

PubMed1996

Development of a reliable colorectal cancer liver metastasis model.

UNLABELLED: The liver is the most frequent and most fatal site of distant spread of colorectal cancer. Most current animal models of liver metastases utilize direct liver or intravascular injection (dissimilar to mechanisms of metastasis) or immunosuppression to establish metastases. AIM: The aim of this study was to develop a reliable rat model of liver metastases in immunocompetent hosts, whereby metastases spread hematogenously as in colorectal cancer. METHODS: WB-2054 is a poorly differentiated colon adenocarcinoma induced by 1,2 DMH in a WF x BN F1 hybrid rat. WB-2054-M0, Ml, M2, M3, and M4 are successive metastatic variant cell lines obtained through serial application of the Fidler hypothesis. WF x BN F1 rats were inoculated intrasplenically with 1 x 10(6)(M0) or 5 x 10(6)(M0-M4) cells; the spleen was left intact. Animals were evaluated 4 to 12 weeks postinjection and, if no metastases were found, reexplored 1-2 weeks later. Animals with liver metastases were sacrificed, and full abdominal and thoracic zoopsy was performed. Livers were excised and serially sectioned, to determine size, number, and location of liver metastases, and studied histologically to confirm the nature of the metastases. RESULTS: 44% (4/9), 80% (8/10), 86% (65/76), 94% (34/36), and 100% (65/65) of animals inoculated with the M0, M1, M2, M3, and M4 cell lines, respectively, developed liver metastases. Metastases were uniformly spread throughout all lobes of the livers. CONCLUSION: We have developed an extremely hepatotrophic metastatic colorectal cancer cell line. Intrasplenic injection of WB-2054-M4 cells is a reliable model for producing colorectal cancer liver metastases without the need for immunosuppression and should prove valuable in colorectal liver metastasis experiments.

Adenocarcinoma↗

PubMedDate not supplied

Current status in laparoscopic colorectal surgery.

BACKGROUND: Laparoscopic techniques are being applied with increasing frequency to surgery of both small and large intestines. PURPOSE: This review article was undertaken to analyze the current direction of laparoscopic colorectal surgery. RESULTS: The most feasible procedures are diagnostic laparoscopy, construction of intestinal stomas, rectopexy, and limited resections for benign conditions. Resections for Crohn's disease, especially extensive resections, and colorectal cancer are complex and should be considered investigational. CONCLUSIONS: The role for use of laparoscopic techniques in colorectal surgery will expand greatly in the next several years.

Adenomatous Polyposis Coli↗