Protein expression pattern of P-glycoprotein along the gastrointestinal tract of the yucatan micropig

The purpose of this study is to characterize the distribution pattern of P-gp protein levels along the entire GI tract in the Yucatan micropig, which is being developed as a model for human drug bioavailability. Small and large intestines were freshly obtained and divided into about 37 segments and 10 segments, respectively (ca., 1 foot/segment). Epithelial cells from the small intestine were obtained by an elution method; whereas, a scraping method was applied to the large intestine. Total cellular protein was isolated from the epithelial cells. Western blot analysis using P-gp antibody showed that the amount of P-gp protein increased distally from the duodenum to the ileum over approximately a 10-fold range. P-gp protein in the large intestine was present at a higher level in the central portion, but the absolute amount was much less than what was found in the small intestine.

Experimental lens-sparing optimization in therapeutic orbital irradiation with electron beams

There has been a number of approaches in the literature for therapeutic malignant and benign orbital irradiation. All techniques intend to deliver a homogenous dose to the orbital and retroorbital target volume while sparing the lens of excessive dose. In this experimental lens-sparing study, 4 MeV and 12 MeV anterior electron irradiation has been used with cerrobend shielding circular blocks of varying diameter and thickness placed on a thin Mylar at the distal tip of the electron applicator to spare the lens. The first phase of the study in water phantom has been designed to determine the shield thickness and diameter constant for 4 MeV and 12 MeV electron beams. After optimizing the lens dose by water phantom, the second phase of our study has been designed to measure doses at lens and other specific localizations in randophantom under same conditions with 4 MeV and 12 MeV electron beams. By this technique lens accumulated 18.56% of prescribed dose and lateral aspects of the lens received 44.59% of the prescribed dose in 4 MeV electron irradiation, whereas this was 13.86% and 44.80%, respectively in 12 MeV electron irradiation. The technique used is found to be an extremely simple and effective technique allowing an easier setup with excellent dose distribution characteristics with lens sparing applicable to orbital irradiation practice.

Sensitive and rapid isocratic liquid chromatography method for the quantitation of curcumin in plasma

An HPLC assay was developed using three methods of plasma sample preparation in order to quantitate curcumin, the main constituent in the herbal dietary supplement turmeric. Each method involves simple and rapid processing of samples (either an ethyl acetate or chloroform extraction) with resulting different quantitation limits for curcumin. The assay was developed in an effort to quantify extremely low curcumin plasma concentrations observed in preliminary in vivo studies. The most sensitive assay can reliably detect concentrations down to 2.5 ng/ml. Plasma quantitation was precise and accurate based on both intra- and inter-day validations as indicated by low values for coefficients of variation and bias, respectively (< or =15%). The analytical validation was reproducible between different analysts. The resulting analytical method couples desired sensitivity with the ease of an isocratic system.

Evaluation of radiation carcinogenesis risk in vertebral hemangioma treated by radiotherapy

The purpose of this study is to report carcinogenesis risk factor evaluation in vertebral hemangioma patients treated by radiotherapy. Between 1975 and 1995, 29 patients received 20-30 Gy total irradiation dose using conventional fractionation scheme. All the patients had measurements with thermoluminescent dosimeters (TLD 100 ), placed on multiple randophantom sites in vivo within the irradiated volume, to verify irradiation accuracy and calculate carcinogenesis risk factor. Twenty nine still-alive patients who had a minimum 6-year and maximum 26-year follow-up (median 14.34 years) have been evaluated by carcinogenic radiation risk factor on the basis of tissue weighting factors as defined by International Commission on Radiological Protection Publication 60. Reasonable pain relief has been obtained in all 29 patients. Calculated mean carcinogenesis risk factor is 0.6% for single irradiation portals and 0.9% for double irradiation portals in the whole group, whilst no secondary cancer has been detected. Radiotherapy is an effective treatment modality in relieving pain of vertebral hemangioma patients. Estimated secondary cancer risk factor for this benign neoplasm irradiation is not as high as can be feared.

Can radiotherapy be a treatment option for elderly women with invasive vulvar carcinoma without radical surgery?

PURPOSE OF THE INVESTIGATION

To evaluate the impact of radiotherapy after limited surgery in vulvar carcinoma.

METHODS

Between March 1980 and January 2000, 22 patients older than 60 years and suffering from invasive vulvar carcinoma were treated with limited surgery and radiotherapy at Gülhane Military Medicine Academy. These are the subjects of this review.

RESULTS

The median age of the patients was 67 (range 60 to 78 years). Median follow-up was 35 months (range 12 to 60 months). Local recurrence rate was 18%. Median time to local failure was 12 months (range 8 to 14 months). Two patients with local failure also developed lung metastases. Five-year survival rate was 60% and cause-specific survival rate was 69%. No treatment delay or death related to treatment was observed.

CONCLUSIONS

Radiotherapy and conservative surgery can be an alternative to radical surgery with less morbidity in elderly patients.

Evaluation of dose homogenization and radiation carcinogenesis risk in total body irradiation for bone marrow transplantation

The purpose of this study is to report on the dose homogeneity in total body irradiated patients undergoing Bone Marrow Transplantation (BMT), and carcinogenic risk in surviving patients. Between 1987 and 2001, 105 patients received hyperfractionated (6 fractions in 3 days) 12 Gy Total Body Irradiation (TBI) in our institution with lateral opposed fields. All the patients had measurements with thermoluminiscence dosimetry (TLD100) placed on seven bilateral body sites in vivo, controlled by the randophantom measurements to verify reasonable dose homogeneity achievement. The comorbid effects in the whole TBI conditioning group with at least three months post BMT follow-up were noted and surviving patients who had a minimum 5-year and maximum 14-year follow-up (median 7.8 years) have been evaluated for carcinogenic radiation risk on the basis of tissue weighting factors as defined by ICRP 60. Reasonable dose homogeneity by lateral opposed beam TBI has been obtained in all 105 patients in whom lateral TLD100 measurement means were within +5% of the planned doses. Calculated carcinogenesis risk factor was 11.34% for males and 12.40% for females, and no second-cancer has been detected whilst radiation-induced 5 cataracts and 10 interstitial pneumonia comorbidities were noted. Dose homogenization can be well achieved for hyperfractionated lateral-beam TBI with acceptable comorbidities and estimated second-cancer risk is significant but relatively low compared to the risk from the clinical indications for TBI.

Postoperative radiotherapy for ganglioglioma; report of three cases and review of the literature

Gangliogliomas are rare tumors of the central nervous system. The definite role of postoperative radiotherapy has not been established. In studying three cases who underwent radiotherapy after subtotal resection, we evaluated the clinical, pathological, radiological features with follow-up of mean 8.1 years. All of three patients were male, and mean age was 22.3 years. All of the cases have temporal lobe lesions and, except for one, they all have seizures. Radiotherapy was given to all patients after surgery. Parallely opposed local fields were used. A total of 54 Gy in 5.5 weeks was given to the mid-plane using a Co-60 tele-therapy device. No recurrence, no new symptoms, and no new neurological deficiency were detected during follow-up.

Endovascular radiotherapy for stenosis after percutaneous transluminal coronary angioplasty

The rate of restenosis after percutaneous transluminal coronary angioplasty ranges from 30% to 60%. Despite numerous trials, no effective pharmacological therapy has been found. This late effect can be reduced by endovascular radiotherapy. In animal models of restenosis after balloon injury, there is marked reduction of neointimal proliferation when the injured vessel is irradiated, using a variety of radiation sources and delivery systems. Early human trials did not focus on the importance of source selection and calibration. Other aspects which should be carefully determined are source selection and responsibilities of the treatment team. These matters are reviewed and discussed.

Recognition of 16S rRNA by ribosomal protein S4 from Bacillus stearothermophilus

Protein S4 is essential for bacterial small ribosomal subunit assembly and recognizes the 5' domain (approximately 500 nt) of small subunit rRNA. This study characterizes the thermodynamics of forming the S4-5' domain rRNA complex from a thermophile, Bacillus stearothermophilus, and points out unexpected differences from the homologous Escherichia coli complex. Upon incubation of the protein and RNA at temperatures between 35 and 50 degrees C under ribosome reconstitution conditions [350 mM KCl, 8 mM MgCl2, and 30 mM Tris (pH 7.5)], a complex with an association constant of > or = 10(9) M(-1) was observed, more than an order of magnitude tighter than previously found for the homologous E. coli complex under similar conditions. This high-affinity complex was shown to be stoichiometric, in equilibrium, and formed at rates on the order of magnitude expected for diffusion-controlled reactions ( approximately 10(7) M(-1) x s(-1)), though at low temperatures the complex became kinetically trapped. Heterologous binding experiments with E. coli S4 and 5' domain RNA suggest that it is the B. stearothermophilus S4, not the rRNA, that is activated by higher temperatures; the E. coli S4 is able to bind 5' domain rRNA equally well at 0 and 37 degrees C. Tight complex formation requires a low Mg ion concentration (1-2 mM) and is very sensitive to KCl concentration [- partial differential[log(K)]/partial differential(log[KCl]) = 9.3]. The protein has an unusually strong nonspecific binding affinity of 3-5 x 10(6) M(-1), detected as a binding of one or two additional proteins to the target 5' domain RNA or two to three proteins binding a noncognate 23S rRNA fragment of the approximately same size. This binding is not as sensitive to monovalent ion concentration [- partial differential[log(K)]/partial differential(log[KCl]) = 6.3] as specific binding and does not require Mg ion. These findings are consistent with S4 stabilizing a compact form of the rRNA 5' domain.

Comparison of granulocyte-colony, stimulating factor and granulocyte macrophage-colony stimulating factor in the treatment of chemotherapy extravasation ulcers

The results of perilesional granulocyte macrophage-colony stimulating factor and granulocyte-colony stimulating factor application in a patient with chemotherapy extravasation ulcers are reported. A 64-year-old patient with recurrent ovarian carcinoma was admitted to our department in February 1999. In June 1998, six cycles of chemotherapy were applied to the patient after surgery. At the first cycle, two ulcers appeared on both lower arms related to doxorubicin extravasation despite all interventions. When the patient was admitted to in our department, we observed an ulcer on the distal part of the right lower arm with a dimension of 1.5x2 cm and another on the proximal portion of the left lower arm with a dimension of 2.5x3 cm. Of those ulcers, the bigger and deeper one on the left was treated with weekly 400 mcg granulocyte macrophage-colony stimulating factor subcutaneously for three weeks. The lesion completely disappeared in the fourth week. The other ulcer that was left for control on the right arm was treated with weekly 48 M.U. granulocyte-colony stimulating factor for four weeks. This ulcer did not reduce in size. As a result granulocyte-colony stimulating factor did not affect the healing of chemotherapy extravasation ulcers, as did granulocyte macrophage-stimulating factor.

Structural Basis of Binding of High-Affinity Ligands to Protein Kinase C: Prediction of the Binding Modes through a New Molecular Dynamics Method and Evaluation by Site-Directed Mutagenesis

The structural basis of protein kinase C (PKC) binding to several classes of high-affinity ligands has been investigated through complementary computational and experimental methods. Employing a recently developed q-jumping molecular dynamics (MD) simulation method, which allows us to consider the flexibility of both the ligands and the receptor in docking studies, we predicted the binding models of phorbol-13-acetate, phorbol-12,13-dibutyrate (PDBu), indolactam V (ILV), ingenol-3-benzoate, and thymeleatoxin to PKC. The "predicted" binding model for phorbol-13-acetate is virtually identical to the experimentally determined binding model for this ligand. The predicted binding model for PDBU is the same as that for phorbol-13-acetate in terms of the hydrogen-bonding network and hydrophobic contacts. The predicted binding model for ILV is the same as that obtained in a previous docking study using a Monte Carlo method and is consistent with the structure-activity relationships for this class of ligands. Together with the X-ray structure of phorbol-13-acetate in complex with PKCdelta C1b, the predicted binding models of PDBu, ILV, ingenol-3-benzoate, and thymeleatoxin in complex with PKC showed that the binding of these ligands to PKC is governed by a combination of several highly specific and optimal hydrogen bonds and hydrophobic contacts. However, the hydrogen-bonding network for each class of ligand is somewhat different and the number of hydrogen bonds formed between PKC and these ligands has no correlation with their binding affinities. To provide a direct and quantitative assessment of the contributions of several conserved residues around the binding site to PKC-ligand binding, we have made 11 mutations and measured the binding affinities of the high-affinity PKC ligands to these mutants. The results obtained through site-directed mutagenic analysis support our predicted binding models for these ligands and provide new insights into PKC-ligand binding. Although all the ligands have high affinity for the wild-type PKCdelta C1b, our site-directed mutagenic results showed that ILV is the ligand most sensitive to structural perturbations of the binding site while ingenol-3-benzoate is the least sensitive among the four classes of ligands examined here. Finally, we have employed conventional MD simulations to investigate the structural perturbations caused by each mutation to further examine the role played by each individual residue in PKC-ligand binding. MD simulations revealed that several mutations, including Pro11 --> Gly, Leu21 --> Gly, Leu24 --> Gly, and Gln27 --> Gly, cause a rather large conformational alteration to the PKC binding site and, in some cases, to the overall structure of the protein. The complete abolishment or the significant reduction in PKC-ligand binding observed for these mutants thus reflects the loss of certain direct contacts between the side chain of the mutated residue in PKC and ligands as well as the large conformational alteration to the binding site caused by the mutation.

Prostate specific antigen in the female body: its role in breast cancer prognosis

Prostate-specific antigen, a 33 kDa serine protease, is found at high concentrations in seminal plasma and prostate epithelial cells. It is currently used for the diagnosis and monitoring of prostate carcinoma. However, several investigators have demonstrated nonprostatic sources of prostate specific antigen, including amniotic fluid, breast milk, breast cyst fluid, nipple aspirate fluid, and breast tumor cytosol. Studies have revealed that a high prostate-specific antigen level in tumors of women with breast cancer is associated with good prognosis. This finding is analyzed in this manuscript.

Evaluation of a minimal experimental design for determination of enzyme kinetic parameters and inhibition mechanism

The advent of combinatorial chemistry has led to a deluge of new chemical entities whose metabolic pathways need to be determined. A significant issue involves determination of the ability of new agents to inhibit the metabolism of existing drugs as well as its own susceptibility for altered metabolism. There is need to estimate the enzyme inhibition parameters and mechanism or mechanisms of inhibition with minimal experimental effort. We examined a minimal experimental design for obtaining reliable estimates of K(i) (and V(max) and K(m)). Simulations have been applied to a variety of experimental scenarios. The least experimentally demanding case involved three substrate concentrations, [S], for the control and one substrate-inhibitor pair, [S]-[I]. The control and inhibitor data (with 20% coefficient of variance random error) were simultaneously fit to the full nonlinear competitive inhibition equation [simultaneous nonlinear regression (SNLR)]. Excellent estimates of the correct kinetic parameters were obtained. This approach is clearly limited by the a prior assumption of mechanism. Further simulations determined whether SNLR would permit assessment of the inhibition mechanism (competitive or noncompetitive). The minimal design examined three [S] (control) and three [S]-[I] pairs. This design was successful in identifying the correct model for 98 of 100 data sets (20% coefficient of variance random error). SNLR analysis of metabolite formation rate versus [S] permits a dramatic reduction in experimental effort while providing reliable estimates of K(i), K(m), and V(max) along with an estimation of the mechanism of inhibition. The accuracy of the parameter estimates will be affected by the experimental variability of the system under investigation.

Role for the C-terminus in agonist-induced mu opioid receptor phosphorylation and desensitization

Determining which domains and amino acid residues of the mu opioid receptor are phosphorylated is critical for understanding the mechanism of mu opioid receptor phosphorylation. The role of the C-terminus of the receptor was investigated by examining the C-terminally truncated or point-mutated mu opioid receptors in receptor phosphorylation and desensitization. Both wild-type and mutated receptors were stably expressed in Chinese hamster ovary (CHO) cells. The receptor expression was confirmed by receptor radioligand binding and immunoblottting. After exposure to 5 microM of DAMGO, phosphorylation of the C-terminally truncated receptor and the mutant receptor T394A was reduced to 40 and 10% of that of the wild-type receptor, respectively. Mutation effects on agonist-induced desensitization were studied using adenylyl cyclase inhibition assays. The C-terminally truncated receptor and mutant receptor T394A both showed complete loss of DAMGO-induced desensitization, while the mutant T/S-7A receptor only lost part of its ability to desensitize. Taken together, these results suggest that the C-terminus of the mu opioid receptor participates in receptor phosphorylation and desensitization with threonine 394, a crucial residue for both features. DAMGO-induced mu opioid receptor phosphorylation and desensitization are associated and appear to involve both the mu opioid receptor C-terminus and other domains of the receptor.

Split-course radiotherapy with or without concurrent or sequential chemotherapy in non-small cell lung cancer

In our department we designed a three-armed study to compare the effects of sequential and concurrent chemoradiotherapy in locally advanced non-small cell lung cancer. Each treatment arm consisted of 15 patients with histologically confirmed stage III non-small cell lung cancer. In group 1, the main treatment approach was split-course radiotherapy alone. In group 2, 6 mg/m2 of cisplatin was applied daily and concurrently with split-course radiotherapy. In group 3, two cycles of etoposide, ifosfamide, and cisplatin chemotherapy, which ended three weeks before split-course radiotherapy, was applied. Overall response rates were 40%, 66%, and 53% in groups 1, 2, and 3, respectively. Median survival was 10, 11, and 10 months for groups 1, 2, and 3 respectively. Results are discussed in the light of the literature.

A successful and simplified filgrastim primed single apheresis method without large volume apheresis for peripheral blood stem cell collection

BACKGROUND

There is a tendency to use only one apheresis collection to reduce the morbidity and the cost of peripheral blood stem cell collection. We studied whether rapid and complete engraftment could be achieved by single apheresis by using only Filgrastim without large volume apheresis in previously treated patients.

METHODS

Engraftment of single apheresis in 25 patients was compared with those of multiple apheresis in 26 patients; 52% of patients in the single apheresis group and 62% of patients in the multiple apheresis group were heavily pretreated. All patients received 10-15 microg/kg/day of Filgrastim starting on day 14 after 3-4 cycles of induction chemotherapy. Apheresis was performed using Cobe Spectra on day 4, 5 or 6 in the single apheresis group and every other day in the multiple apheresis group after day 3.

RESULTS

The median collection volume was 250 ml (250-300 ml) in the single apheresis group and 750 ml (200-1500 ml) in the multiple apheresis group. The median CD34(+) cell number was not significantly different in the two groups (11.79 vs. 9.38x10(6)/kg). The median times to achieve leukocytes > or =1x10(9)/l and platelets > or =50x10(9)/l counts were 10 days (8-21 days) and 15 days (9-38 days) in the single apheresis group vs 11 days (8-23 days) and 20 days (10-32 days) in the multiple apheresis group, respectively (p<0.05). Antibiotic use was less in the single apheresis group than the multiple apheresis group (9 vs. 12 days, p<0.05).

CONCLUSION

Adequate numbers of peripheral stem cells were harvested by G-CSF in a single apheresis without large volume apheresis even in heavily pretreated patients. Rapid and complete engraftment occurred in all patients and it was faster in single than multiple apheresis.

Agonist-induced, G protein-dependent and -independent down-regulation of the mu opioid receptor. The receptor is a direct substrate for protein-tyrosine kinase

The mu opioid receptor (MOR) has been shown to desensitize after 1 h of exposure to the opioid peptide, [D-Ala(2), N-MePhe(4), Gly-ol(5)]enkephalin (DAMGO), largely by the loss of receptors from the cell surface and receptor down-regulation. We have previously shown that the Thr(394) in the carboxyl tail is essential for agonist-induced early desensitization, presumably by serving as a primary phosphorylation site for G protein-coupled receptor kinase. Using a T394A mutant receptor, we determined that Thr(394) was also responsible for mu opioid receptor down-regulation. The T394A mutant receptor displayed 50% reduction of receptor down-regulation (14.8%) compared with wild type receptor (34%) upon 1 h of exposure to DAMGO. Agonist-induced T394A receptor down-regulation was unaffected by pertussis toxin treatment, indicating involvement of a mechanism independent of G protein function. Interestingly, pertussis toxin-insensitive T394A receptor down-regulation was completely inhibited by a tyrosine kinase inhibitor, genistein. Tyrosine kinase inhibition blocked wild type MOR down-regulation by 50%, and the genistein-resistant wild type MOR down-regulation was completely pertussis toxin-sensitive. Following DAMGO stimulation, MOR was shown to be phosphorylated at tyrosine residue(s), indicating that the receptor was a direct substrate for tyrosine kinase action. Mutagenesis of the four intracellular tyrosine residues resulted in complete inhibition of the G protein-insensitive MOR internalization. Therefore, agonist-induced MOR down-regulation appears to be mediated by two distinct cellular signal transduction pathways. One is G protein-dependent and GRK-dependent, which can be abolished by pertussis toxin treatment of wild type MOR or by mutagenesis of Thr(394). The other novel pathway is G protein-independent but tyrosine kinase-dependent, blocked by genistein treatment, and one in which Thr(394) has no regulatory role but phosphorylation of tyrosine residues appears essential.

Fifteen cases of male breast carcinoma treated between 1980 and 1995

Male breast carcinoma is a rare malignity. In Turkey, as in other countries, there are insufficient studies on male breast cancer. In the Radiation Oncology Department, Gülhane Military Medical Academy, we treated 15 cases of male breast cancer versus 1393 female breast cancer. Two of the cases had stage I, nine had stage II, and the remaining four had stage III disease. Median age was 52. All patients had definitive external beam radiation therapy with daily 200 cGy fractionation, following surgery. Median follow-up was 227 months. Five year survival rate was found to be 60% for all stages. Our evaluations of the pathologic findings, management, and treatment outcome were compared with literature.

In vivo chiro-inositol metabolism in the rat: a defect in chiro-inositol synthesis from myo-inositol and an increased incorporation of chiro-[3H]inositol into phospholipid in the Goto-Kakizaki (G.K) rat

We report our comparative studies of myo- and chiro-[3H]inositol distribution in control nondiabetic Wistar and spontaneous nonobese insulin-resistant Type II diabetic G.K. rat tissues following 78-h labeling period. From various tissue extracts, free inositols, inositol phosphates, and inositol phospholipids were isolated and analyzed. Our findings demonstrate (1) a significant difference in the metabolism of myo- and chiro-inositol in normal Wistar and G.K. rats, (2) a severe defect in conversion of myo-[3H]inositol to chiro-[3H]inositol at the inositol phospholipid level of insulin-sensitive tissues of the G.K. rat, (3) an increased incorporation of myo-[3H]inositol into purified inositol phospholipids of the G.K. rat consistent with a decreased conversion to chiro-[3H]inositol, (4) the presumed presence of a pathway which incorporates chiro-[3H]inositol into inositol phospholipids, and which is overactive in the G.K. rat compared to the Wistar rat, and (5) no or minimal conversion of chiro-[3H]inositol to myo-[3H]inositol.

Agonist-induced desensitization of the mu opioid receptor is determined by threonine 394 preceded by acidic amino acids in the COOH-terminal tail

To identify the structural determinants necessary for mu opioid receptor desensitization, we serially ablated potential phosphorylation sites in the carboxyl tail of the receptor and examined their effects on [D-Ala2,N-Me-Phe4,Gly-ol5]enkephalin (DAMGO)-induced desensitization. First, we replaced Thr394 with alanine (T394A) and stably expressed this mutant receptor in Chinese hamster ovary cells. The T394A receptor did not desensitize after 1 h of treatment with DAMGO, indicating that Thr394 is required for agonist-induced early desensitization. To test whether Thr394 was the only residue necessary, we investigated the importance of 7 potential phosphorylation sites between residues 363 and 383, which were all replaced by alanines with the Thr394 maintained. This mutant (AT) showed partial loss of desensitization (30%), which was attributable to the Ala mutation at Thr383, since complete desensitization was achieved by restoring Thr383 (ATT). These results suggest that Thr394 is the primary recognition site for G protein-coupled receptor kinases, but Thr383 is also required for complete agonist-induced desensitization. The specificity of Thr394 as the primary initiation site appears to be dependent on the preceding acidic amino acid stretch, because in a mutant in which glutamic acid residues at 388, 391, and 393 were replaced by glutamines (EQ), agonist-induced desensitization was completely abolished, identical to the T394A mutant.

Prostate rhabdomyosarcoma in a young adult: a case study

Prostate rhabdomyosarcoma is a very rare malignancy in young adults. This case study presents an 18-year-old adult with prostate rhabdomyosarcoma treated with a combined regimen of radiotherapy and chemotherapy.

Protective effect of vitamin A on acute radiation injury in the small intestine

The objective of this study was to examine the influence of vitamin A on the development of early radiation-induced reactions in the rat small intestine. The early effects of intraoperative gamma-radiation on the small bowel utilizing the terminal ileum of Sprague-Dawley rats and the protective effect of supplemental vitamin A on acute radiation injury were investigated. Three groups were included in the study: group I (10 rats) was the surgical control group; group II (13 rats) underwent only intraoperative irradiation; and group III (10 rats) was the vitamin A plus irradiation group. Exteriorized terminal ileal segments of groups II and III were exposed to a single fraction of 20 Gy of intraoperative gamma-irradiation. On the seventh postoperative day, terminal ileal segments of all rats were resected and histopathologically evaluated for ulceration, enteritis cystica profunda, atypical epithelial regeneration, fibrosis, vascular sclerosis, and inflammatory process. Although none of the above findings were present in the surgical control group, group III rats experienced less severe effects than group II rats. The results suggest the early side effects of radiation may be prevented by vitamin A supplementation.