[Biodegradable catheters for fistula prevention in hypospadias. Experimental preliminary study]

INTRODUCTION

Continuous technical innovations are not enough to resolve the high incidence of fistula after hypospadias repair. A urethral catheter-tutor made of reabsorbable polymeric biomaterial (RPB) which could be left in situ long enough could reduce the complications.

TARGET

To investigate in an animal model differents RPB to be used in urology.

METHODOLOGY

CRL Wistar rats, males, divided into 5 equal groups according to the used polymers: polylactide; lactic-coprolactone copolymer; lactic-glycolic copolymer; simulated; control silicones. Three individuals were sacrificed per group at 4th, 10th and 16th week. In all animals (exceptuating the simulated group), biomaterial was fixed to the bladder wall bylaparotomy. Animals remained in individual housing and kept under daily control of hematuria during the first 15 days and weekly weight and urine control for pH and lactate. After being slaughtered, remaining polymer was collected for chemical analysis and bladder tissue for hystologic study.

RESULTS

There was no mortality, hematuria nor other clinical signs. The bladder wall showed a mild foreign body reaction. The values of lactate and pH in urine did not reach toxic levels. Lactic-glycolic was totally reabsorbed by the 10th week and had the lowest degree of calcification. Polylactide and lactic-coprolactone remained intact.

CONCLUSION

The model of urinary bladder has proven useful for studying the degradation of bioresorbable polymers. The analyzed polymers have spent long time to be reabsorbed, so we will have to study new others.

[Adaptation in the small intestine: Effect of minimal enteral nutrition and probiotics on proliferation and apoptosis in the intestinal wall]

BACKGROUND

The intestinal wall integrity is central to the barrier function and depends on the balance of proliferation/apoptosis. Short bowel (SB) or Parenteral Nutrition (PN) induce high bacterial translocation (BT) probably by the intestinal barrier bug. Probiotics or minimal enteral nutrition (MEN) have reduced BT in animal models.

OBJECTIVE

Determine in two BT animal models (SB or PN) the effect of MEN or probiotics on proliferation and apoptosis rates of the intestinal wall.

METHODS

Seventy-one Wistar rats, divided into 4 groups: 1) PN (N = 23): parenteral nutrition; 2) PNMEN (N = 16): PN + MEN (2.9 g/100 g/day standard diet); 3) RES (N = 15): 80% bowel resection and standard oral diet; 4) RESPROB (N = 17): RES + probiotics (7 X 10(9) CFU Bifidobacterium lactis). After 10 days in metabolic cages, mesenteryc lymph nodes, portal blood and peripheral blood were cultured. By immunohistochemistry, proliferation and apoptosis index were calculated as well as the proliferation-apoptosis rate.

RESULTS

BT: decreased in PNMEN (45%) and RESPROB groups (35%) versus PN (65%) and RES (67%) groups (p<0.05). Proliferation index: was better in PNMEN (12,07) and RESPROB (13,93) groups than PN (7,45) and RES (5,54) groups. (p</0.05). Apoptosis index: PNMEN group had 7,81 and PN group 14,90. (p<0,05). Proliferation-apoptosis rate: was higher in PNMEN (1,54) and RESPROB (1,67) groups than PN (0,50) ans RES (0,71) groups. (p<0.01).

CONCLUSIONS

MEN and probiotics reduce BT and improve cellular renewal by encouraging the proliferation. MEN also prevents apoptosis.

Minimizing creatine kinase variability in rats for neuromuscular research purposes

Rat serum or plasma creatine kinase (CK) activity is widely used to evaluate myopathic processes, to test the myotoxicity of different drugs, or to analyse the benefits of emerging gene therapies in some neuromuscular disorders. However, great variability is found in this determination. The aim of this study has been to control some factors of variation in order to reduce variability and increase the reproducibility of analytical data. 8-10-week-old Wistar-Han rats were used. The study consisted of four sequential phases. Phase I aimed to analyse the effect of ether and isoflurane as anaesthetic drugs. The objective of Phase II was to evaluate bleeding rats via retro-orbital sinus vs. tail vein. Phases III and IV were designed as two separate, repeated measure experiments on two factors: habituation to laboratory handling procedures in Phase III and gender in Phase IV. The repeated factor was the storage temperature of blood sample prior to centrifugation. Ether did not significantly increased the CK value. Using isoflurane, getting rats accustomed to laboratory handling procedures and whole blood refrigeration prior to centrifugation and serum separation resulted in statistically significant reduction in CK value and variability. Male rats showed significantly higher values than female rats. In the light of our findings, CK value and variability in rats may be minimized by choosing tail vein as site of bleeding, getting rats accustomed to laboratory handling procedures and maintaining whole blood refrigerated until centrifugation and serum separation.

[Short bowel syndrome in the research setting: 15 years' experience]

The fight against infection and liver disease associated with parenteral nutrition (PN) are surely two of the most problematic aspects in the management of paediatric patients with short bowel syndrome (SBS). In the Research Unit of Donostia Hospital, we have spent the past 15 years investigating different ways of reducing these complications in an experimental model of short bowel in the Wistar rat (resection of 80% of the small bowel, with and without PN). All the experiments had a duration of 10 days and 323 animals reached the end of the study period. Nine groups were established in which some type of intervention was performed, and there were 8 control groups. The interventions were: 3 dietary (minimal enteral nutrition [MEN] with low or high dose probiotics); 5 pharmacological (administration of growth hormone [GH], epidermal growth factor [EGF], insulin, cholecystokinin [CCK], and selective intestinal decontamination [SID]); and 1 surgical (resection of the ileocaecal valve). Infection due to bacterial translocation (BT) was detected by culture of mesenteric lymph nodes, portal blood and peripheral blood, and liver damage by the levels of proinflammatory cytokines (IL-1 and TNF-alpha). In summary, our results are: Probiotics, MEN and SID reduce BT. Liver damage was milder in the groups with MEN, SID and CCK. The groups receiving GH, EGF or insulin presented a higher incidence of BT. BT was lower after resection of the ileocaecal valve. In conclusion, the probiotics, MEN and CCK could be useful in the management of children with SBS. These data confirm the utility of this experimental model of short bowel for the investigation of different aspects of SBS.

[Effect of the administration of cholecystokinin on the cholestasis associated with total parenteral nutrition in experimental short bowel]

INTRODUCTION

Total parenteral nutrition (TPN) is not free of complications. One of the most serious is cholestasis; the cause of this complication is unclear but it may be due to a lack of an enteral stimulus for cholecystokinin (CCK) production. CCK is essential for contraction of the gallbladder and also stimulates intrahepatic bile flow. Its absence may contribute to cholestasis. After any hepatic aggression, the Kupffer cells respond and release proinflammatory cytokines, such as interleukin-1 (IL-1) and tumour necrosis factor alpha (TNF-alpha), which increase the hepatic damage. The objective of this experimental study has been to observe the effect that the exogenous administration of CCK could have on hepatic damage in experimental short bowel with and without TPN, determined using the serum levels of IL-1 and TNF-alpha.

MATERIAL AND METHODS

A resection of 80% of the small bowel was performed on 53 Wistar rats and a continuous infusion of saline or TPN was initiated. The rats were divided into the following groups: SHAM (N = 14): normal saline infusion and free access to food and water. TPN (N = 15): Standard TPN. SHAM-CCK (N = 14): same as the SHAM group but with a daily dose of CCK. TPN-CCK (N = 10): same as the TPN group but with a daily dose of CCK. At the end of the experiment, the animals were sacrificed and blood samples were obtained to determine the IL-1 and TNF-alpha values by ELISA.

RESULTS

The IL-1 and TNF-alpha levels were higher in the TPN group (7.537 and 5.899 pg/mL, respectively) than in the SHAM group (6.509 and 4.989 pg/mL, respectively) (p > 0.05). The TNF-alpha values were higher in the SHAM group (4.989 pg/mL) than in the SHAM-CCK group (4.583 pg/mL) (p < 0.001). The IL-1 and TNF-alpha levels were higher in the TPN group than in the TPN-CCK group (6.709 and 4.794 pg/mL, respectively) (p < 0.001 for TNF-alpha).

CONCLUSIONS

1. There is a rise in the serum levels of the pro-inflammatory cytokines IL-1 and TNF-alpha in animals with short bowel on TPN or enteral nutrition. 2. The administration of CCK causes a fall in the IL-1 and TNF-alpha levels, and could be used such as a further measure to prevent TPN-associated cholestasis.

[Necrotizing enterocolitis and bacterial translocation: role of minimal enteral nutrition]

INTRODUCTION

Both necrotizing enterocolitis (NEC) and bacterial translocation (BT) have in common that bacterial overgrowth, a decrease in immunity and intestinal mucosal damage, followed by a barrier failure, can act as trigger factors. The main objectives in NEC treatment are to reduce mortality due to sepsis and to promote feeding tolerance. To achieve that, Minimal Enteral Nutrition (MEN) (less than 25% of the calories provided by enteral route) is a more and more used technique in newborns who receive Parenteral Nutrition (PN) to slow down fasting related villi atrophy and to attenuate its consequences.

AIM

To test the hypothesis that MEN decreases BT in an experimental model of PN.

METHODS

Twenty-four adult Wistar male rats received a continuous infusion of all-in-one PN solution through a jugular vein catheter. The animals were randomly divided in two groups and maintained in individual metabolic cages for ten days. * Control group (N= 1): fasting rats receiving, standard PN (300 mL/kg/ 24 h, 280 kcall kg/24 h). * MEN group (N=13): standard PN and rat chow (15 g /24 h, 3,1 kcal/g). At the end of the experiment animals were sacrificed and mesenteric lymph nodes (MLN), and both peripheral and portal blood samples were recovered and cultured. Bacterial identification in blood was carried out by conventional methods and MLN culture was considered positive with a growth over 100 Colony Forming Units/g.

RESULTS

Weight curve was better in MEN group and BT was also significantly reduced. Translocation was found in 45% of control group and 8% of MEN group (p < 0,05). The relative risk (RR) was 5,9 (IC 95% 0,81-43,71) and the number needed to treat (NNT) was 3 (95% CI 2-20).

CONCLUSIONS

1. MEN reduces the incidence of BT in an experimental model of parenteral nutrition. 2. BT reduction could decrease NEC-related sepsis risk.

[Selective intestinal decontamination and parenteral nutrition related liver disease. Experimental study]

Selective intestinal decontamination (SID) has been useful restraining Bacterial translocation (BT) in both animal models and human clinics. The not well known parenteral nutrition-related liver disease is a serious problem associated to short bowel and long-term parenteral nutrition (PN) use, and BT is also frequent in those patients. Germs reach liver through portal vein and activate Kupffer cells, which release cytokines as IL-1 or TNF-alpha. The aim of this study was to test the use of SID restraining BT in a PN undergoing experimental short bowel model, and its possible favourable consequences on hepatic injury determined by IL-1 and TNF-alpha levels. Twenty-five 240-280 g Wistar rats were divided into two groups and maintained in individual metabolic cages for ten days: Resection-PN group (n=15): animals with a bowel resection of the 80% and a continuous PN infusion. Resection-PN-SID (n=10) group: similar to previous group and a daily oral administration of Tobramycine (20mg/kg/day) and Polymyxine-E (25mg/kg/day). Animals were sacrificed and mesenteric lymph nodes (MLN), and both peripheral and portal blood samples were recovered for TB determination in bacterial culture. Determination of both IL-l and TNF-alpha seric levels were carried out by ELISA. Bacterial translocation incidence was higher in RES-NPT group (66.6%) than RES-NPT-SID group (30%) (P>0,05). The relative risk was 2.22 (IC 95% 0,81-6,11) and the number needed to treat was 3 (IC 95% 2-235). Seric levels of IL-1 and TNF-alpha were also higher in RES-NPT group (7,537 and 5,399 pg/ml, respectively) than in RES-NPT-SID group (6,397 and 5,032 pg/ml respectively) (p<0,001). 1. SID reduces TB in a PN undergoing experimental short bowel resection murine model. 2. Parenteral nutrition-related liver disease decreases in DIS receiving animals.

[Incidence of bacterial translocation in four different models of experimental short bowel syndrome]

The outcome of patients with short bowel syndrome is influenced for factors such as the length of remnant intestine or the presence or absence of ileocecal valve (ICV). Gram-negative sepsis, the main cause of mortality in this group of children, is probably due to bacterial translocation (BT), because after gut resection there are a number of circumstances that favour its occurrence, being the most known intestinal dismotility, bacterial overgrowth, loss of gut-associated lymphoid tissue, total parenteral nutrition (TPN) and fasting related mucosal atrophy. The aim of this experimental controlled study was to test the incidence of BT after four different types of gut resection, in animals fed orally or receiving TPN. Hundred and three adult Wistar rats bred and raised in our facilities according to European Union Regulations were randomly divided in six groups:--Group 1 (n = 26): non-manipulated animals, served as a control.--Group 2 (n = 14): 80% non-lethal small bowel resection, fed orally.--Group 3 (n = 15): same resection as group 2 but including ICV. Rat chow ad libitum.--Group 4 (n = 27): non-resected fasting animals receiving all-in-one TPN solution.--Group 5 (n = 11): same resection as group 2, but fasting and receiving TPN--Group 6 (n = 10): 90% small bowel resection, including cecum and ICV, fasting and TPN. The animals were maintained for 10 days in individual metabolic cages, and, at the end of the experiment, were bled by portal and cardiac puncture. Mesenteric lymph nodes, peripheral and portal blood samples were cultured for BT. Non-manipulated rats (group 1) had lower BT incidence (8%) than resected ones (groups 2, 3, 5 and 6, 93%, 60%, 91%, 60%, p < 0.05) or animals non-resected, receiving TPN (group 4.51%, p < 0.05). When resection included ICV in orally fed rats BT index was also lower (group 3 vs group 2.60% vs 91%, p < 0.05). In TPN resected animals a drop was also found in BT when ICV and cecum were added to small bowel resection (group 6 vs group 5.60% vs 91%, p < 0.05).

IN CONCLUSION

1. Gut resection is associated to a high degree of BT, even if the animals are fed orally. 2. Resection including ICV, produced less BT. 3. TPN-related BT was shown in half of the animals non resected. 4. TPN-resected rats had also less BT when ICV and cecum were removed.

Probiotic supplementation reduces the risk of bacterial translocation in experimental short bowel syndrome

BACKGROUND/PURPOSE

Probiotics are live organisms that survive passage through the gastrointestinal tract and have beneficial effects on the host. Lactobacillus and Bifidobacterium have been recommended for cholesterol lowering, acute diarrhea, prevention of cancer, or inflammatory bowel disease. On the other hand, after massive bowel resection, bacterial overgrowth is frequent and favors bacterial translocation (BT). The possible beneficial effects of Bifidobacterium lactis (BL) administration on BT in experimental short bowel syndrome (SBS), have not been investigated. The aim of this study was to test the hypothesis that BL administration decreases BT in SBS in animals fed orally.

METHODS

One hundred twenty-eight adult Wistar rats fed orally with standard rat chow and tap water "ad libitum" were maintained in individual metabolic cages for 10 days and divided into 3 groups: control group (n = 71): nonmanipulated animals; RES group (n = 39): 80% gut resection from 10 cm beyond the angle of Treitz to 10 cm above the cecum; RES-PRO group (n = 18): same resection and daily 7.8 x 10(8) CFU B Lactis administration, after orogastric intubation. At the end of the experiment they were killed, and mesenteric lymph nodes (MLN) and peripheral and portal blood specimens were recovered and cultured. Bacterial identification in blood was made by conventional methods, and MLN culture was considered positive with a growth over 100 CFU/g.

RESULTS

Bacterial translocation was detected in 6% of control group rats. The incidence of BT in the RES group was 87% (34 of 39), whereas only 50% (9 of 18) of RES-PRO animals had BT (P <.05). The relative risk reduction (RRR) was 0.43 (95% Cl 0.14 to 0.72), and the number needed to treat (NNT) was 3 (95% Cl 2 to 8). In other words, animals that received BL had the risk of BT reduced by 43% (RRR of 0.43), and of every 3 animals treated, 1 is expected to be free of BT (NNT of 3).

CONCLUSION

Administration of B Lactis reduces the incidence of BT in adult Wistar rats after 80% gut resection.

Anorectal atresia. An experimental model in the rat

Aiming to assess the development of the anorectal sphincteric apparatus and whether it is influenced by the presence of an intestinal conduit through the muscular complex, we seek to develop an experimental model of anorectal atresia in foetuses of female pregnant rats, given orally the herbicide ethylenethiourea (ETU). Six 3-months-old, 300 g female Wistar rats were included in the study group (SG). The foetuses of another unexposed rat formed the control group (CG). In the SG 54, foetuses were alive, all had hypoplasia of the tail and 47 (87%) had no visible anal orifice. The 18 foetuses of the CG were normal. The histological study was performed at the level of the pubic symphysis. Type I anorectal atresia was defined when this section demonstrated an intestinal conduit and Type II when only a muscular cord was found, without any intestinal tube. This study was completed in 15 (32%) of the SG, 9 (60%) with anorectal atresia Type II and 6 (40%) with atresia Type I, and in 11 animals (61%) of the CG. The thickness of the sphincter muscle was larger in the CG (260.47+/-35.32 micro) than in the SG (208.98+/-55.01 micro), p<0.05, but this difference was due to the animals showing atresia Type II. To conclude: ETU had a teratogenic effect. The foetuses with atresia, particularly Type II, had a decreased development of the muscular complex. The presence of an intestinal conduit does not significantly influence the development of the muscular complex.

[Effect of various trophic factors on bacterial translocation in experimental short bowel syndrome]

Massive bowel resection triggers an adaptive process in the remaining intestine in spite of which, bacterial translocation (BT) is frequent under these conditions. Several trophic factors, including growth hormone (GH), epidermal growth factor (EGF) and insuline (INS) are involved in the process of adaptation in short bowel syndrome (SBS). However, the effect of GH, EGF or INS on BT has not been investigated experimentally. The aim of the study was to test the hypothesis that GH, EGF or INS administration prevents BT in rats with SBS receiving only parenteral nutrition (PN). Thirty-seven adult Wistar rats underwent central venous cannulation and were randomly assigned to one of two groups receiving for ten days four treatment regimes: PN group (N = 10) fasting, all-in-one PN solution (300 mL/kg/24 h, 280 kcal/kg/24 h), 80% gut resection including ileo-cecal valve. GH group (N = 9) fasting, same PN regime and resection plus GH (1 mg/kg/d, s.c.). EGF group (N = 9): same PN regime and resection plus EGF (150 microgr/24 h, e.v.) INS group(N = 9): same PN regime and resection plus INS (1 U.I./100 g/24 h s.c.) At the end of the experiment the rats were exanguinated and mesenteric lymph nodes and samples of systemic and portal blood were obtained and cultured. Several samples of full-thickness jejunal wall were taken for measuring cell proliferation index (PCNA) and mucosal thickness. Jejunal mucosal thickness increased by 30%, 28% and 29% and PCNA index by 21%, 20% and 25% in GH, EGF and INS, treated rats respectively in comparison with those treated with PN alone. However, contrary to our expectations, BT expressed by positive culture of intestinal germs in systemic blood was demonstrated respectively in 44%, 40% and 28% of GH, EGF and INS animals, respectively, and in 0% of PN-only rats. Although exogenous GH, EGF or INS improves gut mucosal structure in rats with SBS treated with PN, it seems to increase rather than decrease mucosal permeability to intestinal germs in them.

Effect of growth hormone, epidermal growth factor, and insulin on bacterial translocation in experimental short bowel syndrome

BACKGROUND/PURPOSE

An adaptive process starts in the remaining intestine after massive resection, and several trophic factors including growth hormone (GH), epidermal growth factor (EGF), and insulin (INS) have been shown to have a positive effect on it. Bacterial translocation (BT) is frequent after extensive small bowel resection, but the effects of GH, EGF, or INS have not been investigated in experimental short bowel syndrome (SBS). This study tests the hypothesis that GH, EGF, or INS decrease BT in SBS in rats with parenteral nutrition (PN).

METHODS

Thirty-eight adult Wistar rats underwent central venous cannulation and were assigned randomly to 1 of 4 groups receiving for 10 days 4 treatment regimes: (1) PN group (n = 10): fasting, all-in-one PN solution (300 mL/kg/24 h, 280 kcal/kg/24 h), 80% gut resection including ileo-cecal valve; (2) GH group (n = 9): fasting, same PN regime and resection, GH (1 mg/kg/d, subcutaneously); (3) EGF group (n = 9): fasting, PN, resection, EGF (150 microg/24 h intravenously); (4) INS group (n = 9): fasting, PN, resection, INS (1 UI/100 g/24 h subcutaneously). At the end of the experiment they were killed, and mesenteric lymph nodes (MLN) and peripheral and portal blood samples were recovered and cultured. Several fragments of intestine were taken to determine cell proliferation (PCNA index) and morphometric parameters (villous height, crypt depth).

RESULTS

GH, EGF, and INS groups showed a 28%, 29%, and 30% increase in gut mucosal thickness, and PCNA index rose 21%, 20%, and 25%, respectively in comparison with PN controls. Bacterial translocation to peripheral blood was detected in 0% of PN animals and in 44%, 40%, and 28% of GH, EGF, or INS rats, respectively (P < .05). No differences were found in BT in MLN or portal blood among groups.

CONCLUSION

Administration of GH, EGF, or INS improves gut mucosal structure in rats with SBS under PN, but, surprisingly, the incidence of BT detected in peripheral blood was increased rather than decreased in animals receiving these treatments.

Bacterial translocation is favored by the preservation of the ileocecal valve in experimental short bowel with total parenteral nutrition

Sepsis in short-bowel syndrome (SBS) is in part due to bacterial translocation (BT). Parenteral nutrition (PN) is often necessary in SBS and promotes BT. The aim of this study was to asses the effect of the presence or absence of ileocecal valve (ICV) on BT in parenterally-fed rats with massive intestinal resection. Sixty-five adult Wistar rats underwent central venous cannulations and were randomly assigned to one of five groups receiving for ten days five treatment regimes: Sham (n = 17) standard rat chow + i.v. saline. PN (n = 17) fasting + PN. Res-Sham (n = 10) standard rat chow + i.v. saline + 80% gut resection. Res-PN (n = 11) fasting, PN + 80% gut resection. Res-ICV-PN (n = 10) fasting, PN + 80% gut resection including ICV. At the end of the experiment they were euthanized and mesenteric lymph nodes (MLN), spleen and peripheral and portal blood specimens were recovered and cultured. BT was found in 47% of PN animals, 91% of Res-PN rats, 100% of Res-Sham group and 60% of Res-ICV-PN animals, but not in Sham ones. 97% of BT+ animals had positive cultures in MLN and/or portal blood, whereas germs beyond liver were detected in 30% of Res-Sham, 37% of PN, 50% of Res-PN and 0% of Res-ICV-PN rats. The present study confirms that both massive intestinal resection and PN promote BT. In addition, it shows that animals deprived of ICV have lower incidence of BT in this setting than those with it and that the germs do not reach in them peripheral blood in the same proportions as in ICV-intact animals. These results suggest that the presence of an intact ICV favor BT in parenterally-fed rats with massive intestinal resection.

Effect of growth hormone on bacterial translocation in experimental short-bowel syndrome

Despite the adaptive process triggered in the remaining intestine by massive bowel resection, bacterial translocation (BT) is frequent under these conditions. Several trophic factors, including growth hormone (GH), are involved in the process of adaptation in short-bowel syndrome (SBS). However, the effect of GH on BT has not been investigated experimentally. The aim of this study was to test the hypothesis that GH administration prevents BT in rats with SBS receiving only parental nutrition (PN). Nineteen adult Wistar rats underwent central venous cannulation and were randomly assigned to one of two groups receiving for 10 days two treatment regimes: PN group (n = 10): fasting, all-in-one PN solution (300 ml. kg. 24 h, 280 kcal/kg. 24 h), 80% gut section including ileocecal valve; GH group (n = 9): fasting, same PN regime and resection plus GH 1 mg/kg s.c). At the end of the experiment, the rats were killed and mesenteric lymph nodes (MLN) and samples of systemic and portal blood were obtained and cultured. Several samples of full-thickness jejunal wall were taken for determining cell proliferation index (PCNA) and mucosal thickness. Jejunal mucosal thickness increased by 30% and PCNA index by 35% in GH-treated rats in comparison with those treated with PN alone. However, contrary to our expectations, BT expressed by positive culture of intestinal flora in portal blood, MLN, or systemic blood was found in 60% of PN and 87% of GH animals (P = 0.1). Translocation to the general circulation expressed by the presence of organisms in systemic blood was detected in 0% of PN and 44% of GH rats (P < 0.05). Although exogenous GH improves gut mucosal structure in rats with SBS treated with PN, it seems to increase rather than decrease mucosal permeability to intestinal bacteria.

Bacterial translocation and T-lymphocyte populations in experimental short-bowel syndrome

Bacterial translocation (BT) accounts in part for sepsis in short-bowel syndrome in which total parenteral nutrition (TPN) is routinely necessary. TPN "per se" facilitates BT and it has been suggested that decreased T-lymphocyte populations (TLP) in newborn rabbits and nude mice promote BT as well. We have tested the hypothesis that BT and modifications in TLP are to be expected in rats subjected to TPN and gut resection. Forty-five adult Wistar rats underwent central venous cannulations and were randomly assigned to one of three groups receiving for ten days three treatment regimes: - Group Sham (n = 17) oral intake of rat chow + saline (300 ml/kg/24 h) through a jugular vein catheter. - Group TPN (n = 17) fasting + infusion of all-in-one TPN solution (300 ml/kg/24 h). - Group RES (n = 11) fasting, same TPN regime + 80% gut resection. At the end of the experiment they were sacrified and specimens (peripheral and portal blood, spleen and mesenteric lymph nodes) were recovered, cultured and/or assessed for CD4+ and CD8+. Bacterial translocation was found in 47% of TPN animals, 92% of RES rats, but not in SHAM ones. Lymphocyte populations were not different in BT+ (n = 8) or BT- (n = 9) rats in the TPN group. TPN and resected animals showed a rise in CD4+ and a drop in CD8+ (then a better CD4+/CD8 ratio) when comparing with SHAM group rats. From this data we may conclude that: 1) BT is frequent if TPN is administered, and constant in resected animals. 2) No apparent relationship between the proportions of CD4+ and CD8+ lymphocytes and BT could be shown in TPN group. 3) High CD4+/CD8+ ratio in TPN and RES groups demonstrate that BT is possible even having good TLP.

[Saliva in experimental gastroesophageal reflux]

Saliva, with a neutral pH, mucous content and inhibitory factors of the stomach acid secretion, can be considered a protecting element of the esophageal mucosa in the gastroesophageal reflux. 39 Wistar rats 175-225 g were used divided in seven groups: "C" control, "E-A" esophago-gastrostomy. "E-M" esophago-myectomy, "S-C" only sialoadenectomy, "S-EA" sialoadenectomy plus esophagogastrostomy, "S-EM" sialoadenectomy plus esophago-myectomy. 15 days later the rats were sacrificed, the esophagus was taken out for its histological examination and blood samples were drawn. The comparison between the control and treated groups, showed a significant deterioration of the EA, SEA and SEM groups regarding the final weight, and the SC group in the white series and ions. Many of the animals with esophagus operations showed vomit signs and general affectation. None of the groups showed esophageal lesions in the histology, from which it can be deduced that, in the rat, a 90% saliva absence doesn't produce negative effects on the esophageal mucosa either in acid presence or not.

Lymphocyte subpopulations after extensive small bowel resection in the rat

The increased risk of infection after massive intestinal resection (MIR) may be attributable to impaired nutrition, loss of intestinal lymphoid tissue, or both. This study examines whether MIR itself changes the immune cell populations in laboratory animals when nutritional status is preserved. The authors studied cellular immunity (lymphocyte subsets T4 and T8 and the T4:T8 ratio) and humoral immunity (IgG, IgM, IgA, and B lymphocytes) in the blood, spleen, and mesenteric lymph nodes of unresected Wistar rats (control group, n = 6) and of animals that underwent 80% bowel resection followed by 7 days of either oral feeding (resection-oral group, n = 6) or parenteral nutrition (resection-TPN group, n = 6). The increase in body weight was similar among all groups, and the levels of total protein, albumin, prealbumin, and immunoglobulin remained unchanged. All resected animals, irrespective of their feeding route, had significantly lower proportions of T4 and B lymphocytes and T4:T8 ratio in blood, T4 and T8 in mesenteric lymph nodes, and T4 and T4:T8 ratio in the spleen. The author's results suggest that removal of large amounts of lymphoid tissue along with the bowel during MIR might lead to inadequate immune response even when the nutritional status is preserved.

Continuous positive airway pressure and gastroesophageal reflux: an experimental study

Gastroesophageal reflux (GER) often occurs in babies receiving respiratory assistance for neonatal distress. The authors examined the lower esophageal sphincter and the thoracic and abdominal pressure conditions in rats under progressively higher continuous positive airway pressure (CPAP) to test the efficacy of the antireflux barrier under such conditions. Intrathoracic and intraabdominal pressures were recorded within the esophagus and within the inferior vena cava in 10 anaesthesized 250-g male rats. Pull-through techniques were used for lower esophageal sphincter pressure (LESP) and length (LESL) studies, and the length of the intraabdominal segment of the esophagus (LIASE) was also determined. Measurements were performed in baseline conditions and at CPAP levels of 0, 1, 3, 5, and 7 cm H2O. The respiratory effort progressively increased with prolonged expiration and decreased frequency. LESP and LESL did not change significantly, but the antireflux barrier was weakened by a progressive shortening of LIASE. Successive CPAP increases led to increasingly negative thoracic pressures during inspiration, and increasingly positive abdominal pressures during expiration yielded progressively greater transdiaphragmatic pressure gradients. The authors suggest that CPAP weakens the antireflux barrier and, at the same time, increases the gastroesophageal pressure gradient, thus increasing the risk of GER. Although transpolation of experimental data to the clinical setting is always hazardous, the authors believe this issue should be investigated in infants.

Airway obstruction and gastroesophageal reflux: an experimental study on the pathogenesis of this association

Gastroesophageal reflux (GER) frequently complicates the clinical course of children suffering from conditions leading to upper airway obstruction (UAO) (choanal atresia, tracheomalacia, esophageal atresia, vascular rings, etc). In an attempt to explore whether partial airway obstruction causes changes in the normal thoracoabdominal pressure gradients, we measured end-inspiratory intrathoracic and intraabdominal pressures in anesthetized rats under spontaneous breathing conditions, after tracheostomy, and under upper airway obstruction induced by tracheal intubation with three progressively narrower cannulae (inner diameters 1.0 mm, 0.5 mm, and 0.2 mm). We also measured the lower esophageal sphincter pressure (LESP) and length (LESL) and calculated the thoracoabdominal end-inspiratory pressure gradient (TAEIPG). Neither LESP nor LESL changed significantly before or after maximal tracheal obstruction (14.3 +/- 6.2 v 18 +/- 7.6 cm H2O [P > .05] and 0.34 +/- 0.09 v 0.41 +/- 0.1 cm H2O [P > .05] respectively) but TAEIPG significantly increased from 5.58 +/- 1.34 cm H2O to 17.62 +/- 4.27 cm H2O (P < .01) under the same conditions, mainly as a result of progressively increasing negative intrathoracic pressures during inspiration. These experiments prove that the powerful thoracoabdominal pressure gradients developed after partial UAO may contribute to the pathogenesis of GER by overcoming the antireflux barrier function. This study points out the convenience of routinely screening for GER all children with airway obstructive conditions, bearing in mind that the reestablishment of normal respiratory conditions should be the primary goal of treatment.

Lung growth and maturation in the rat model of experimentally induced congenital diaphragmatic hernia

This paper explores whether, in addition to the previously described lung hypoplasia with arteriolar hypermuscularization present in the nitrofen-induced foetal rat model of congenital diaphragmatic hernia (CDH), there are changes in the respiratory exchange epithelium, consistent with the hypothesis that abnormal surfactant production and/or release could account in part for the respiratory insufficiency in this condition. Foetal lungs from nitrofen-treated rats were obtained on the 21st day of gestation, weighed and processed for light and electron-microscopic studies and compared to controls of the same age. Tissues from 29 control and 26 CDH foetuses were examined. In addition, lungs from 19 foetuses born to nitrofen-treated dams but without CDH were also studied. The lungs from CDH animals were hypoplastic by weight in comparison with control ones and so were those from treated foetuses without CDH. Airway branching was arrested in CDH at the pseudo-glandular stage of development, corresponding to the 16th day of gestation and the very narrow air spaces were lined by generally mature type II pneumocytes rich in glycogen and lamellar bodies corresponding to the 19th day of gestation. This pattern was in contrast to that of the control foetuses which had a normal terminal sac pattern with flat type I pneumocyte lining corresponding to their gestational age. Nitrofentreated animals without CDH had intermediate patterns. These findings support the hypothesis that the surfactant-producing system has the same lesions in this experimental model as in other less-affordable ones, like the foetal lamb one. Further studies on the contribution of this factor to the altered respiratory physiology in CDH using this model are warranted.

The nutrition of the fetus with intestinal atresia: studies in the chick embryo model

This article examines the effects of experimental prenatal intestinal obstruction on the growth and blood composition of chick embryos. Intestinal atresia (IA) was produced by bipolar bowel electrocoagulation in fertile eggs on the 14th day of incubation. The chicks killed on the 19th day were measured, weighed, and blood-sampled. Twenty-three control, 10 sham-operated, and 11 IA chicks were studied. Animals with IA were severely undernourished by weight (43.4 +/- 4.7 v 70.3 +/- 7.6% of egg weight, P < .001) and length (15.3 +/- 1.1 v 18.1 +/- 0.9 mm tibial length, P < .001) in comparison with sham-operated ones. Their hematocrit was slightly lower, and total protein increased. Prealbumin was absent in their sera and albumin, alpha and beta globulins were significantly decreased, whereas gamma-globulin was greatly increased. Sodium, potassium chloride, urea, and glucose remained within normal limits. The lack of placenta in the avian embryo precludes any supply of nutrients by this route and the ingestion of amniotic fluid, which is protein-rich after the 13th day of incubation, when the opening of the seroamniotic connection allows albumen to be mixed with it, becomes the main source of nutrients until hatching. Obstruction of the main incoming avenue by IA induces severe malnutrition in this model which relies on this route to a greater extent than the human fetus. In spite of the obvious biological differences between the avian embryo and the human fetus, the present evidence supports the hypothesis that prenatal interruption of the amniotic fluid transit contributes to fetal undergrowth in IA.

The kidney in the fetal rat model of congenital diaphragmatic hernia induced by nitrofen

This paper explores whether there is a correlation between kidney and lung growths in an experimental model of congenital diaphragmatic hernia (CDH) induced by intragastric administration of Nitrofen (115 mg/kg) in olive oil on time-dated pregnant Wistar rats at the 9th day of gestation. For comparison we used pregnant rats treated with olive oil alone. Twenty-nine normal fetuses from 3 control rats and 24 left CDH fetuses from 6 Nitrofen rats were studied. Fetal (3.6 +/- 0.8 v 4.9 +/- 0.4 g, P < .001) and total lung (2% +/- 0.5% v 2.6% +/- 0.3% of body weight, P < .001) weights were significantly decreased in animals with CDH. Kidneys were also smaller in CDH animals although not significantly (0.7% +/- 0.1% v 0.8% +/- 0.1% of body weight, P = .05) and were also histologically immature. Regression of kidney weight on body weight for both groups yielded regression lines that were identical at analysis of covariance and all data points from the CDH group were within the control group 95% confidence limits. After converting raw data into lung/body and kidney/body weight ratios, no inverse correlation suggesting a feedback mechanism of growth regulation between both organs could be found. Since nitrofen acts through modifications of the thyroid hormone status in both dam and fetus, altered maturation of several organs should be expected although some of them, like the lung, are the leading targets. The present CDH rodent model is probably different from the human malformation in spite of the striking anatomic similarities between them.(ABSTRACT TRUNCATED AT 250 WORDS)

[Peritoneal dialysis in the chick embryo with gastroschisis]

The ever increasing possibilities of prenatal diagnosis and intra-uterine treatment of malformations has created the need for simple and reproducible experimental models on which to build a better knowledge of the biology of the abnormal fetus. Using our own model of experimental gastroschisis (GX) in the chick embryo, we have undertaken to study whether transperitoneal exchanges of water and solutes take place after prolonged visceral exposure to the mixture of amniotic and allantoic fluids which has a greater content in Potassium, Urea, and Proteins and less sodium, chloride and glucose than fetal blood. After surgical evisceration of bowel on the 14th day, incubation was resumed until the 19th day and the embryos were then recovered for weighing and for blood sampling biochemical analysis. The chicks with GX had significantly increased serum Potassium and minimally increased Urea whereas Sodium and Chloride were moderately decreased. Our data confirm that a real peritoneal dialysis with transperitoneal exchange of water and solutes between extraembryonal fluids and the fetal internal environment does indeed take place in this model.

[Total parenteral nutrition in rats]

Total parenteral nutrition (TPN) is difficult in rats because of their activity and aggressivity. On the other hand, this animal is an ideal experimental subject because it is easy to handle, resistant to infections, it has a short vital cycle and is very cheap. Long-term TPN can be simulated in rats after only relatively short periods of infusion. We report herein the results on TPN in rats obtained in our laboratory. Male Wistar rats (n = 86) weighing 170-225 g had a central line inserted under general anesthesia and received 330 mL/kg/day of fluids. They were divided into an Experimental Group (n = 70) that had a solution containing carbohydrates, proteins and lipids (310 Kcal/kg/day) and a Control Group (n = 16) receiving only saline and having free access to rat pellets. Total infusion time was 582.9 days. Twenty-five percent of the rats were withdrawn because of technical problems, 7% because of infection, 46% died and only 22% survived until the end of the experimental period. All animals gained weight. Those in the Experimental Group had significantly higher total protein and Chloride whereas those in the Control Group had higher leukocytes, BUN, liver weight, large bowel length and spleen relative weight. This TPN rat model is suitable for metabolic studies in the laboratory and should be further developed.

Transperitoneal exchanges of water and solutes in the fetus with gastroschisis. Experimental study in the chick embryo

Aiming at testing the hypothesis that, in the foetus with gastroschisis (GX) peritoneal dialysis during antenatal bowel exposure to the amniotic fluid may induce some modifications of the internal environment, we have studied the composition of blood, amniotic fluid and allantoic fluid in a chick embryo model of GX. Intestinal loops were surgically eviscerated in 184 embryos on the 14th day of incubation and exposed to the mixture of both embryonal fluids until the 19th day (hatching expected at the 21th). Typical lesions of GX were present in half of the 94 survivors (n = 42). For comparison we used a control group of non-manipulated animals (n = 19) and a "sham" group of animals in which the operation was carried out only until umbilical manipulation but without bowel exposure (n = 22). Chicks with GX were smaller and slightly dehydrated as attested by clinical signs and had moderately increased hematocrit. They had significant hyperkaliaemia and slight decreases in serum Na and Cl. Urea, total protein and protein fractions were not modified. Taking into account the gradients for such substances existing between the dialysate (amino-allantoic mixture) and the embryonal blood, the changes observed, albeit slight, suggest that there was some evidence of dialysis through the peritoneum: lower Na and Cl concentrations in the dialysate than in blood, induced slight falls in serum Na and Cl whereas higher K concentration resulted in severe hyperkaliemia. The high levels of albumin in the chick amniotic fluid did not allow protein depletion and therefore total protein and its fractions remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Spina bifida: a chick embryo experimental model

Neural Tube Defects (NTD) can be induced in the chick embryo with relative ease in order to provide an experimental tool for investigation of such disabling malformations. Domestic hen (Gallus gallus) eggs were incubated at 37.5 degrees C and 80% humidity for 24 h. At that moment, 5 ml of albumen were aspirated by sterile puncture of the shell, and the incubation was resumed. The embryos were recovered and studied at the 8th, 10th and 14th days. Almost half (45%) of the 602 treated embryos survived and 73 of them (12%) had various malformations. Thirty-six (6%) suffered NTD of which 30 were open myelomeningocele, 2 meningocele and 4 encephalocele. The anatomy of the defects was astonishingly similar to that of the human malformation. Whether these experimental NTD are induced by mechanical or nutritional modifications of the internal environment of the egg is unknown, but the similarity of the lesion with those in humans make them suitable for further investigation of these issues. We believe that this relatively simple and inexpensive model is a suitable tool for research on spina bifida.

[The chick embryo as a model of fetal surgery: intestinal atresia]

Aiming at depicting the advantages of chick embryo as a model of fetal surgery we report on our experience of 402 operations carried out in an attempt to induce fetal intestinal obstruction. We have used fertile domestic hen (gallus gallus) eggs incubated at 37.5 degrees with 80% humidity and turned every hour. At the 12th day of incubation we coagulated, after exposing the umbilical cord, a small bowel loop in the physiologic umbilical hernia through a 1 cm-wide opening in the shell which was then sealed with plastic sterile adhesive. After sacrifice at the 15th day of the 76 surviving embryos (19%) we found type I intestinal atresia with localized meconium peritonitis and dilated proximal loop in 46 cases. In 3 out of them there was, like in some human newborns with intestinal obstruction, increased amount of bile-stained amniotic fluid. Both macroscopic and microscopic findings were identical to those usually found in human atresia and in that experimentally induced in fetus of other animal species. We firmly believe that our model is as good as any other for this purpose and, at the same time, it is cheaper and easier to handle.