[Saliva in experimental gastroesophageal reflux]. / La saliva en el reflujo gastro-esofágico experimental.

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.

[Fetal nutrition in intestinal atresia. Studies on the chick embryo]. / Nutrición fetal en la atresia intestinal. Estudios en el embrión de pollo.

This paper 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 sacrificed 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 vs 70.3 +/- 7.6% of egg weight, p < 0.001) and length (15.3 +/- 1.1 vs 18.1 +/- 9 mm. tibial length, p < 0.001) in comparison with sham-operated ones. Their haematocrit was slightly lower, and total protein increased. Pre-albumin 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 sero-amniotic 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 foetus. In spite of the obvious biological differences between the avian embryo and the human foetus, the present evidence supports the hypothesis that prenatal interruption of the amniotic fluid transit contributes to foetal undergrowth in IA.

[Amniotic and serum alphafetoprotein in the chick embryo with neural tube defect]. / Alfafetoproteína sérica y amniótica en el embrión de pollo con defecto del tubo neural.

Although alpha-feto-protein (AFP) is a widely used marker for human neural tube defects (NTD) little is known about the mechanisms for its increase in the amniotic fluid in this condition. For investigating this issue we developed a chick embryo AFP assay and tested it in a NTD experimental model. AFP obtained by electroelution on PAGE/SDS gels from the plasma of 12-day-old embryos was used to produce rabbit polyclonal and mouse monoclonal antibodies. A specific sandwich-type enzyme-immune-assay was developed using both reagents. Sterile aspiration of 5 ml. of albumen from 602 fertile hen eggs on the 27th hour of incubation (Hamburger stages 8 to 11) led to the appearance of NTD in 36 out of the 270 survivors (13%). Amniotic and seric AFP levels were measured on the 15th day of incubation in NTD chicks (n = 11) and in control ones (n = 9) and the results were compared by non-parametric tests. Serum AFP was five times higher in NTD chicks than in controls (119.2 +/- 32.6 vs 523.3 +/- 173.62 micrograms/ml., p < 0.001) and amniotic AFP was absent in control and very increased in NTD animals (0.15 +/- 0.02 vs 87.14 +/- 84 micrograms/ml., p < 0.001). It is concluded that: 1) serum AFP is intriguingly increased in the chick with NTD; 2) since urine is not diversed into the amniotic sac in the avian embryo, the only source of AFP in its fluid is exudation through an open defect. This conclusion is further supported by the absence of amniotic AFP in a chick with a large closed NTD.

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]. / Diálisis peritoneal en el embrión de pollo con laparosquisis.

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.

[Pulmonary surfactant in experimental congenital diaphragmatic hernia]. / Surfactante pulmonar en la hernia diafragmatica congénita experimental.

This paper examines the amounts of tensoactive phospholipids in the lung tissue of rat fetuses treated with Nitrofen (TOK) and in control animals. The herbicide led to congenital diaphragmatic hernia (CDH) in some fetuses and to pulmonary hypoplasia (PH) in all. The amounts of phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylinositol (PI) and phosphatidylethanolamine (PE) per gram of fresh lung tissue were significantly increased in comparison with the control animals, those of phosphatidylserine (PS) and sphingomyelin (SM) were also increased, but not significantly. Fetuses with HP alone had intermediate values. These findings are in agreement with our previous demonstration of an excess of type II pneumocytes in this model, and point to the existence of some trouble of the secretion or release of surfactant in it; although they do no clarify whether the amount of alveolar surfactant is in fact decreased.

[Total parenteral nutrition in rats]. / Nutrición parenteral total en la rata.

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)

[The experimental production of abdominal wall defects in the chick embryo]. / Producción experimental de defectos de la pared abdominal en el embrión de pollo.

We have developed experimental models of gastroschisis and celosomias (omphalocele and Cantrell's pentalogy) in the chick embryo. They were obtained by operation "in ovo" and early aspiration of 5 ml of egg albumin respectively. We have observed 42 gastroschisis out of 184 operated embryos and 12 exomphalos and 20 pentalogies out of 528 aspirated embryos. These models enable us to study the biology of malformed fetuses.

Mucosal morphology in experimental intestinal atresia: studies in the chick embryo.

Lesions identical to those observed in human intestinal atresia (IA) have been experimentally reproduced in several mammal models by either mesenteric vessels or intestinal wall injury. The recent availability of an avian model led us to investigate whether the same lesions could be studied at less expense. An intestinal loop within the body stalk hernia was coagulated on the 12th incubation day in 427 chick embryos (group 3), the lesions were studied in survivors 4 days later under light and scanning electronmicroscopy (EM), and the findings were compared with those in 12 control embryos (group 1) and 14 sham-operated ones (group 2). Types I or II atresias were obtained in 61 (73.4%) of the 83 survivors in group 3. Seromuscular layers were normal at both ends of the lesion; there was some flattening of villi at the proximal, dilated end, and hyperplasia with apparently lengthened, branched villi at the distal, unused one. Mucosal pattern under light microscopy was strikingly close to that observed in human IA and in the fetal lamb experimental model. On the other hand, scanning EM showed that in this model there were no villi as such, but rather prominent mucosal folds that were regularly arranged in a tire-rubber pattern in the normal intestine, flattened and distended in the dilated one, and again roughly normal in the distal unused gut. High-power magnification scanning EM showed that enterocytes were normal at all levels but, in agreement with previous findings in the fetal lamb model, that intercellular spaces were widened in the dilated portion adjacent to the obstruction.(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.

[Experimental malformations of the body wall in the chick embryo]. / Malformations expérimentales de la paroi du tronc chez l'embryon de poulet.

The rapidly growing possibilities of prenatal diagnosis and intrauterine manipulation of the malformed fetus have created the need for animal experimental models as simple and easy to handle as possible. We report on our experience with the induction of body wall defects in the chick embryo. Laparoschisis was produced by evisceration of the bowel through the umbilical stalk and its exposition to the allantoic fluid at the 14th day of incubation. Exomphalos, Cantrell's Pentalogy and Spina Bifida were induced by sterile aspiration of 5 ml of egg albumen at the 24th hour of incubation. All embryos were recovered and studied at the 19th day of incubation. The results can be summarized as follows: ninety-four (51%) of the 184 embryos operated for bowel exteriorization survived and 42 (45%) had intestinal lesions identical to those found in human laparoschisis. Two-hundred ans seventy (45%) of the 602 embryos treated by albumen extraction survived and 197 (73%) had no visible malformations, whereas either exomphalos or Cantrell's pentalogy were found in 37 (14%) and spina bifida was observed in the remaining 36 (13%). All lesions were strikingly similar to the human ones. These models could facilitate research on the above-mentioned malformations without the major difficulties and expenses inherent to fetal research in mammals. The chick embryo, for many decades a favorite model for embryologists, is a tool for fetal research as well and opens some perspectives in this field even for relatively modest laboratories.

[Experimental gastro-esophageal reflux in rats]. / Reflux gastro-oesophagien expérimental chez le rat.

Aiming at developing a model of experimental gastro-esophageal reflux (GER) in the rodent we have tested three surgical procedures (distal esophageal myectomy (EM), esophago-gastrostomy (EG) and end-to-side esophago-jejunostomy (EJ) in three groups of 12 Wistar rats weighting 175 to 225 g. We have used for comparison a control group of unoperated rats. We have checked radiologically and by lower esophageal pH-monitoring that all three procedures induced GER and that this was absent in control animals. Six individuals in each group were sacrificed at the 7th day and the remaining six at the 14th day. At that time blood was drawn and esophageal tissue was collected for histological studies. Animals in the EM group were healthy after operation, had little vomiting and conserved their initial weight. Those in the EG and EJ groups had frequent vomiting, and lost weight. These symptoms were particularly severe in the EJ group. Animals in the control, EM and EG groups had histologically normal esophageal mucosa at the 7th and at the 14th days whereas those in the EJ group had grade 2-3 esophagitis at the 7th and grade 3 esophagitis at the 14th days. Esophageal epithelium in the rat is keratinized and therefore highly resistant to acid GER as attested by its excellent tolerance to reflux in the EM and EG groups. On the contrary, the presence of gastric and pancreatic juices and bile in the refluxate, like in the EJ group, digests the superficial layers of the epithelium and induces severe esophagitis.(ABSTRACT TRUNCATED AT 250 WORDS)