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Biomedical subjects

D Kluth

Publications and source records attributed to D Kluth.

At least 37 records · Page 2Linked to original sources
PubMed1999

A pneumoperitoneum perpetuates severe damage to the ultrastructural integrity of parietal peritoneum in gastric perforation-induced peritonitis in rats.

BACKGROUND: Minimal invasive surgery is increasingly used in conditions complicated by peritonitis-e.g., peptic ulcer perforation. This study was devised to assess the effect of a pneumoperitoneum (PP) on the ultrastructural integrity of parietal peritoneum in perforation-induced peritonitis. METHODS: Anesthetized rats were subjected either to standardized gastrotomy simulating gastric perforation (groups Ia-d; IIa-d) or to sham perforation (groups IIIa-d, IVa-d). In group I (a-d) and III (a-d), CO2 was insufflated 12 h after gastrotomy for 60 min (Pia 4 mmHg). Glutaraldehyde was administered intraperitoneally at the end of the PP period while the abdominal wall was still extended (group index a), as well as 30 sec (b), 2 h (c), and 12 h (d) after desufflation. Specimens were taken from the parietal peritoneum of the left diaphragm for scanning electronic-microscopic (SEM) analysis. In groups II (a-d) and IV (a-d), simple puncture of the abdominal cavity was performed, and specimens were taken at corresponding times. RESULTS: In group Ia (gastric perforation with PP), distortion of the mesothelial cell layer with concomittant opening of stomata to the submesothelial tissue was already observed in specimens harvested while the abdominal wall was still extended. Concomitantly, scarce microvilli, which appeared coarse and thickened, were lying flat on top of the mesothelial cells. After desufflation (groups Ib-c), a rapid process of mesothelial disintegration with disruption from the submesothelial layer and vanishing of microvilli occurred. At 12 h after PP (group Id), complete deterioration of mesothelial cell integrity was observed. In groups IIa-c (gastric perforation without PP), microvilli appeared shrunk and coarse, while integrity of the mesothelial cell layer remained intact up to 2 h after the abdominal puncture. At 12 h after abdominal puncture (group IId), the microvilli had nearly completely vanished and the mesothelium was breaking apart into multiple soils. CONCLUSIONS: In SEM analysis of parietal peritoneum, premature distortion, and disintegration of the mesothelial cell layer was observed in animals exposed to increased abdominal pressure in addition to gastric perforation-induced peritonitis.

Animals↗
PubMed1999

Cardiovascular malformations in experimental congenital diaphragmatic hernia.

BACKGROUND/PURPOSE: Newborns with congenital diaphragmatic hernia (CDH) frequently have associated anomalies that have a major impact on survival rate independent of pulmonary hypoplasia and pulmonary hypertension. Cardiovascular malformations (CVM) represent a major group of lethal extrapulmonary abnormalities that often assume greatest prognostic significance in most CDH studies. Animal models resembling human CDH may aid knowledge of the basic embryology that leads to the coexpression of CDH and CVM. This study, therefore, analyzed the incidence and spectrum of CVM in fetal rats with CDH. METHODS: Left-sided CDH (LCDH) was induced in fetal rats by the maternal administration of 100 mg of nitrofen by gavage on day 9.5 gestation (term, day 22). Control animals received olive oil (OO) and were used for comparative analysis. Fetal rats were harvested by cesarean section on day 21.5 or day 22, histologically processed and examined for CVM. RESULTS: A significant number of CVM were observed in 15 of 60 (25%) LCDH rats compared with 4 of 60 (6.7%) nitrofen non-CDH rats (P = .01). The spectrum of abnormalities in CDH included ventricular septal (VSD) defects (n = 6), vascular rings (n = 4), anomalous subclavian arteries (n = 3), atrioventricular septal defects (n = 1) and Fallot's tetralogy (n = 1). A VSD (n = 1), double-outlet right ventricle VSD (n = 1) and Fallot's tetralogy (n = 2) were noted in nitrofen non-CDH rats. Control (OO) fetal rats (n = 60) displayed no malformations. CONCLUSIONS: These results confirm a significant incidence and spectrum of CVM in a teratogenic CDH model similar to that seen in humans with CDH. The findings of this study reinforce the validity of the nitrofen model as a research tool to uncover the genetic and molecular mechanisms responsible for the genesis of CDH and allied malformations.

Animals↗
PubMed1999

Evaluation of methods of hepatotrophic stimulation in rat heterotopic hepatocyte transplantation using polymers.

BACKGROUND: Hepatocyte transplantation has been studied as an alternative to organ transplantation. Hepatocyte transplant models should provide sufficient cell mass for replacement function and hepatotrophic stimulation of the transplanted cells in heterotopic locations. METHOD: The authors used three-dimensional porous polyvinyl-alcohol matrices as cell carriers, which were implanted between mesenteric leaves of the intestine. In this study, different methods were evaluated for hepatotrophic stimulation. Fifty million transplanted hepatocytes (approximately 10% liver mass) were implanted in Lewis rats. We compared 70% partial hepatectomy, portacaval shunt, cotransplantation of enterocytes, cotransplantation of islets of Langerhans, and methylprednisolone injection to a control group with only hepatocyte transplantation. Portacaval shunt and islet cotransplantation also were used in combination. Specimens were harvested 2 weeks after transplantation, and area per histological cross section compromised by hepatocytes was measured. RESULTS: Seventy percent partial hepatectomy, enterocyte cotransplantation, and methylprednisolone injection resulted in hepatocyte maintenance similar to control group (3,100 +/- 7,592 microm2). Portacaval shunt (96,866 +/- 55,039 microm2) and islet cotransplantation (173,020 +/- 75,977 microm2) yielded a highly significant increase in hepatocyte area. The combination of portacaval shunt and islet cotransplantation resulted in a significant increase compared with using these methods individually (288,930 +/- 86,726 microm2). Additional immunohistochemical stains for active DNA synthesis, insulin, and glucagon demonstrated the proliferative abilities of the hepatocytes and the synthesis of insulin and glucagon in the cotransplanted islets. CONCLUSION: Hepatocyte transplantation can be performed using polymer carriers and that hepatocyte survival and maintenance can be improved with portacaval shunt and islet cotransplantation.

Animals↗
PubMed1999

Influence of pancreatic islets on growth and differentiation of hepatocytes in co-culture.

Improvement of cell culture conditions in hepatic tissue engineering may permit cell/tissue banking and the generation of liver tissue equivalents for transplantation. In these systems, continuous hepatotrophic stimulation is still necessary. We investigated the stimulatory effects of pancreatic islets on hepatocytes in co-culture and characterized the stimulatory mechanisms. Hepatocytes and pancreatic islets were harvested from Lewis rats. Cells were cultured on collagen dishes either with nonstimulated media (controls and co-cultures with low or high islet rate) or stimulated media (controls and co-cultures). To characterize stimulatory mechanisms, additional co-cultures with membrane separation, with antiinsulin, antiglucagon, and with both antibodies were examined. Hepatocyte numbers, albumin secretion rate by enzyme-linked immunoadsorbent assay, and monoethylglycinxylidid biotransformation values by fluorescence polarization immunoassay were assessed. A radioimmunoassay measured insulin and glucagon concentrations. In groups with nonstimulated media, cell number was higher in co-cultures with low islet rate, and albumin secretion rate was increased in co-cultures with high islet rate compared to controls. MEGX biotransformation was decreased in co-cultures. In groups with stimulated media, co-culture had no impact on cell number or albumin secretion rate. Hepatocyte numbers and albumin secretion rates were not changed in co-cultures after membrane separation. Islet effects on hepatocytes were reduced in co-cultures with antiinsulin, antiglucagon, or both antibodies. Pancreatic islets provide stimulation for hepatocytes in vitro. Islet effects were mediated by soluble factors, and are dependent on insulin and glucagon. These results permit further investigations towards three-dimensional transplantable hepatocyte-islet devices for continuous in vitro and in vivo stimulation.

Albumins↗
PubMed1998

Hereditary multiple atresias of the gastrointestinal tract: report of a case and review of the literature.

Hereditary multiple atresia of the gastrointestinal tract is an extremely rare subgroup of intestinal atresia. The aim of this study was to report a new case, to review the literature, and to describe the unique features of this malformation. A computer-generated list of articles on this subject was obtained, and all articles relative to this malformation were reviewed. Thirty-five other well-documented cases were found in the literature. Hereditary multiple atresias have several unique features: (1) the abdominal x-ray shows signs of gastric or duodenal atresia combined with typical large rounded or oval homogeneous calcifications in the abdominal cavity, (2) intraoperatively widespread atresias (exclusively type I and II) extending mostly from stomach to rectum are found, (3) cystic dilatation of the bile ducts can be present in cases with both complete pyloric and duodenal or proximal jejunal atresia, (4) the pathogenesis is still speculative; a combined immunodeficiency should be excluded, and (5) a fatal outcome is the rule.

Abnormalities, Multiple↗
PubMed1998

Formation of spheroidal aggregates of hepatocytes on biodegradable polymers under continuous-flow bioreactor conditions.

Our laboratory has investigated heterotopic hepatocyte transplantation on biodegradable polymer matrices as an experimental treatment for end-stage liver disease. One of the limitations has been survival of sufficient cell mass after transplantation. We hypothesize that in vitro conditioning of cells within polymer matrices prior to implantation may increase hepatocyte survival and function. In this preliminary study we investigated the effect of continuous flow on hepatocytes and sinusoidal endothelial cells on poly-L-lactic acid (PLLA) discs in vitro. Highly porous PLLA discs were manufactured measuring 18 mm diameter by 1 mm thickness using previously described techniques. Hepatocytes were isolated from adult, male Lewis rats (200-300 g) using a two-step collagenase digestion. Sinusoidal endothelial cells were isolated using a two-step collagenase digestion, differential sedimentation, Percoll gradient centrifugation, and selective adherence. PLLA discs were seeded with hepatocytes alone or with co-cultures of hepatocytes and sinusoidal endothelial cells. Seeded discs were then secured within a flow bioreactor chamber and exposed to continuous flow of culture media at a rate of 20 ml/minute through the chamber. Seeded discs placed in static culture conditions served as controls. Specimens seeded with only hepatocytes were harvested at 24 hours, 48 hours, and 168 hours after seeding. Co-culture specimens were harvested after 168 hours. Specimens were viewed under phase-contrast microscopy and then formalin-fixed and prepared for histologic sectioning. Sections were stained with Hematoxylin and Eosin and then analyzed with light microscopy. Hepatocytes under flow conditions formed spheroidal aggregates of cells of 50 to 200 microns in diameter by 24 hours in culture. Hepatocytes in static conditions showed decreased aggregation of cells and spheroid formation was absent. Co-cultured specimens under flow also showed spheroid formation with endothelial cells lining the outside of hepatocyte spheroids. Co-cultured specimens in static culture showed no spheroid formation and no organization between sinusoidal endothelial cells and hepatocytes. These results suggest that continuous flow increases organization of hepatocytes cultured within biodegradable polymer matrices.

Animals↗
PubMed1998

[Effect of pneumoperitoneum on ultrastructure of parietal peritoneum in experimentally induced peritonitis in the rat].

Aim of this study was to analyse the effect of gastric perforation induced peritonitis and a pneumoperitoneum (PP) on the ultrastructure of the parietal peritoneum. After randomisation rats allocated to groups I and II were subjected to standardized gastrotomy simulating gastric perforation. After a 12-h-interval a PP was induced in groups I and III. After PP for 60 min a primary fixant was injected intraperitoneally as the abdominal wall was still extended, as well as 30 s, 2 h and 12 h after release of the PP. In groups II and IV simple puncture of the abdomen was performed. Animals were sacrified and tissue specimens taken from the parietal peritoneum of the left diaphragm were analysed using raster electronic miroscopy (REM: 100x to 5000x). In group II (gastric perforation without PP) microvilli appeared shrunk and coarse, while integrity of the mesothelial cell layer remained intact up to 2 h after abdominal puncture. In group I (gastric perforation with PP) distortion of the mesothelial cell layer with concomittant opening of stomata to the submesothelial tissue was observed already in specimens harvested as the abdominal wall was still extended. Concomittantly scarce microvilli appearing coarse and thickened were laid flat on top of the mesothelial cells. After desufflation a rapid process of mesothelial desintegration with disruption from the submesothelial layer and vanishing of microvilli occurred. In REM analysis of parietal peritoneum premature distortion and desintegration of the mesothelial cell layer was observed after exposure to increased abdominal pressure and to gastric perforation-induced peritonitis.

Animals↗
PubMed1997

[Extralobar lung sequestration with fistula to the esophagus].

Pulmonary sequestrations have no communication with the bronchial tree. Therefore they are usually airless. However, in the presence of a fistula to the esophagus or the stomach, they might contain air or could even be emphysematic. Such a case in a newborn is presented. This very rare anomaly is frequently named "communicating bronchopulmonary foregut malformation". This malformation has to be included in the differential diagnosis of multicystic lung diseases. Diagnosis can be made preoperatively by esophagography and Doppler sonography.

Bronchial Fistula↗
PubMed1997

Inhaled nitric oxide increases survival rates in newborn rats with congenital diaphragmatic hernia.

The high mortality of newborn infants with congenital diaphragmatic hernia (CDH) can be partly attributed to pulmonary hypertension causing extrapulmonary right-to-left shunting with subsequent severe hypoxemia. Inhaled nitric oxide (NO) may reduce elevated pulmonary artery pressure and has been successfully improve arterial oxygenation in some newborns with CDH. However, it is not clear whether inhaled NO will actually improve survival of newborns with CDH. We therefore investigated the effect of inhaled NO on the survival rate of newborn rats with CDH following intrauterine exposure to nitrofen. A total of 151 newborn rats (9 litters) were exposed to nitrofen on day 11 of pregnancy, After spontaneous delivery, 63 newborn rats (4 litters) were allowed to spontaneously breathe air containing NO (80 parts per million), while 88 newborn rats (5 litters) were given air without NO. Survival was checked 15 min after birth and then hourly until the animals were sacrificed at 24 h of age to verify the absence or presence of CDH. The 2 groups of newborn rats breathing air with or without NO did not differ significantly with respect to the presence or size of CDH. Twenty-four of 63 (38%) newborn rats breathing air with NO survived for 24 h, compared to 12 of 88 (14%) rats breathing air alone (p < 0.01). Of newborn rats that were actually found to have CDH (n = 113), 8 of 42 (19%) animals breathing air with NO survived for 24 h, compared to 2 of 71 (2.8%) animals breathing air alone (p < 0.01). In animals with CDH confirmed by autopsy, the median survival time was significantly longer with NO (p < 0.001) ( 2 h, interquartile range 2h-15h), than those breathing or without NO (median/interquartile range 15 min). We conclude that in the nitrofen rat CDH model, significantly improved survival rates occur with inhaled NO as a sole intervention. The combined impact of inhaled NO and mechanical ventilation remains to be determined.

Administration, Inhalation↗
PubMed1997

Applied embryology in pediatric surgery.

The surgical correction of birth defects in the newborn is still a major challenge for pediatric surgeons. Approximately 3% of human newborns present with congenital malformations. In 1%, these malformations are so severe that immediate surgical intervention is necessary to save the affected newborns life. Morbidity remains high in some of these children with the necessity of repeated operations and hospitalizations despite a successful primary operation. As a consequence, in the United States today congenital malformations are the main cause of death in the neonatal period. This mortality shift indicates that gradually knowledge about congenital malformations lags behind the general progress clinical research has made in the surrounding fields. This is highlighted by the fact that detailed knowledge of the embryological background, the natural history and the teratology of many congenital defects is still unclear or controversial. In the past, progress in this field of research was hampered by small numbers of suitable normal human embryos of the various stages. Three-dimensional (3-D) reconstructions which are an essential component to investigate the development of structures like the foregut, the hindgut or the diaphragm, were technically difficult and time consuming to perform. Studies on abnormal development were not possible due to a paucity of appropriate embryos and young fetuses with congenital defects. However, recently some animal models have been developed applicable to embryological studies. We used these to elucidate the abnormal development of the hindgut and the diaphragm. An animal model for the study of abnormal foregut development will be available soon.

Animals↗
PubMed1997

An unusual case of segmental dilatation of the sigmoid colon.

An unusual case of segmental dilatation of the colon (SDC) with a broad membranous bridge in the distal part of the dilated bowel is presented. To our knowledge, this association has not been previously reported and might provide further insight into the underlying etiology of SDC.

Child↗
PubMed1997

Disseminated islands of gastric mucosa in jejunum and ileum detected by technetium-99m-pertechnetate scintigraphy.

Disseminated islands of gastric mucosa are very rare in the small intestine. The secretion of hydrochloric acid can lead to ulceration which results in gastrointestinal bleeding. It is often difficult to localize the focus in case of gastrointestinal blood loss especially in the small bowel. Technetium-99m-pertechnetate scintigraphy may be a helpful tool in detecting ectopic gastric mucosa. We report a case of a 21-mo-old boy with recurrent gastrointestinal bleeding. By using pertechnetate scintigraphy, extensive tracer accumulation in the jejunum and proximal ileum was detected. Histologically, multiple islands of ectopic gastric mucosa were found in about 50 excited mucosal and transmural biopsies. The unusual finding of disseminated accumulation of 99mTc-pertechnetate in the small intestine was the diagnostic clue for such a rare disease.

Biopsy↗
PubMed1997

Current concepts in the embryology of anorectal malformations.

Today, the normal and abnormal development of the hindgut is still a matter of speculation. However, owing to recent studies in appropriate animal models, most embryological events that finally lead to abnormal hindgut development are better known than in the past: (1) The process of maldevelopment starts early in the embryo. (2) The cloacal membrane always is too short in its dorsal part. Thus the dorsal cloaca is missing too. (3) As a result, the hindgut remains attached to the sinus urogenitalis, thus forming the recto-urethral fistula. In the past, an impaired process of septation was believed to be the main cause of abnormal hindgut development. In contrast to this, our results indicate that the development of the septum is more passive than active. Further results of our studies in normal and abnormal development indicate that (1) the embryonic cloaca never passes through a stage that is similar to any form of anorectal malformation in neonates, including the so-called "cloacas" in females, and (2) to explain abnormal development, studies in abnormal embryos are mandatory.

Anal Canal↗
PubMed1996

Anorectal malformation: a new anatomic variant resembling an H-type fistula.

A new anatomic variant of an anorectal malformation resembling an H-type fistula was observed in a newborn girl. This variant consisted of a high-grade stenosis of the anal canal below the level of the levator muscle with a blind-ending fistulous tract originating from the stenotic segment and running toward the posterior wall of the vestibulum. The embryogenesis of this malformation remains to be seen.

Anal Canal↗
PubMed1996

Embryology of congenital diaphragmatic hernia.

It is still generally believed that the defect in congenital diaphragmatic hernia results from failure of the so-called pleuroperitoneal canals (PPCs) to close at the end of the embryonic period (8th gestational week). Furthermore, it is assumed that gut could enter the thoracic cavity through this defect, causing compression and finally hypoplasia of the lung. However, this sequence of embryological events has never been studied, and many details even of normal diaphragmatic development are still unknown. Using scanning electron microscopy and a new animal model of congenital diaphragmatic hernia (CDH), the nitrofen rat model, the normal embryology of the diaphragm was reinvestigated and, for the first time, the crucial developmental steps of congenital diaphragmatic hernia formation were studied. The basic results were: (1) In normal development, the PPCs are never wide enough to allow herniation of gut loops. (2) The formation of the defect happens in an early embryonic period. (3) The early ingrowth of liver through the defect is of major importance for the formation of CDH. In another set of experiments, the nitrofen rat model of congenital diaphragmatic hernias was used to study the cellular mechanisms involved during epithelial and mesenchymal growth and differentiation in normal and in abnormal lungs. These results, combined with selected culture techniques (eg, branching morphogenesis and epithelio-mesenchymal interaction) probably open new ways to a better understanding of the mechanisms that finally lead to an abnormal lung in CDH.

Animals↗
PubMed1996

Toward understanding the developmental anatomy of congenital diaphragmatic hernia.

The pathway of abnormal embryonic development leading to congenital diaphragmatic hernia (CDH) is incompletely understood. Using a nitrofen-induced model of left CDH in rats, sequential stages of development were analyzed by scanning electron microscopy. Abnormal development patterns were observed in the cells comprising the posthepatic mesenchymal plate and the adjacent liver. The septum transversum did not appear to be involved. In this article, the authors theorize that a disturbed "balance of cell growth" is responsible for the creation of the diaphragmatic defect.

Animals↗