[Identification model of tooth number abnormalities on pediatric panoramic radiographs based on deep learning]

Objective: To identify tooth number abnormalities on pediatric panoramic radiographs based on deep learning. Methods: Eight hundred panoramic radiographs of children aged 4 to 11 years meeting the inclusion and exclusion criteria were selected and randomly assigned by writing programs in Python (version 3.9) to the training set (480 images), verification set (160 images) and internal test set (160 images), taken in Department of Pediatric Dentistry, Peking University School and Hospital of Stomatology between November 2012 to August 2020. And all panoramic radiographs of children aged 4 to 11 years taken in the First Outpatient Department of Peking University School and Hospital of Stomatology from June 2022 to December 2022 were collected as the external test set (907 images). All of the 1 707 images were obtained by operators to determine the outline and to label the tooth position of each deciduous tooth, permanent tooth, permanent tooth germ and additional tooth. The deep learning model with ResNet-50 as the backbone network was trained on the training set, validated on the verification set, tested on the internal test set and external test set. The images of test sets were divided into two categories according to whether there was abnormality of tooth number, to calculate sensitivity, specificity, positive predictive value and negative predictive value, and then divided into four types of extra teeth and missing permanent teeth both existed, extra teeth existed only, missing permanent teeth existed only, and normal teeth number, to calculate Kappa values. Results: The sensitivity, specificity, positive predictive value and negative predictive value were 98.0%, 98.3%, 99.0% and 96.7% in the internal test set, and 97.1%, 98.4%, 91.9% and 99.5% in the external test set respectively, according to whether there was abnormality of tooth number. While images were divided into four types, the Kappa value obtained in the internal test set was 0.886, and that in the external test set was 0.912. Conclusions: In this study, a deep learning-based model for identifying abnormal tooth number of children was developed, which could identify the position of additional teeth and output the position of missing permanent teeth on the basis of identifying normal deciduous and permanent teeth and permanent tooth germs on panoramic radiographs, so as to assist in diagnosing tooth number abnormalities.

[Prognosis of adenoid cystic carcinoma of head and neck and risk factors for lung metastasis]

Objective: To analyze the prognosis and risk factors of lung metastasis of patients with adenoid cystic carcinoma(ACC) of head and neck. Methods: A retrospective study was conducted. The data of 157 patients with ACC of head and neck treated in Beijing Tongren Hospital, Capital Medical University from January 2014 to October 2020 were collected, including 72 males and 85 females, with onset age between 14 and 72 years old. According to whether lung metastasis occurred, the patients were divided into lung metastasis group (88 cases) and non-pulmonary metastasis group (69 cases). Kaplan-Meier method was used to calculate the overall survival rate and progression-free survival rate using SPSS 26.0 software. Log-rank test was used to evaluate statistically relevant clinicopathological factors. Cox proportional risk model was used in multivariate analysis for the factors affecting the lung metastasis-free survival using R Studio 1.2.5042. Results: The 3-year and 5-year overall survival rates were 91.5% and 85.2%, respectively. The 3-year and 5-year progression-free survival rates were 57.7% and 34.3%, respectively. Univariate analysis showed that primary site, histological grade, high-grade transformation, Ki-67, T stage, and lymph node status were the risk factors for lung metastasis (χ²=11.78, 10.41, 4.06, 4.71, 5.37, 16.20, respectively, all P<0.05). Multivariate analysis showed independent risk factors for lung metastasis, including submandibular gland and sublingual gland (HR=3.53, 95%CI: 1.19-10.46, P<0.05), T3-4 stage (HR=3.09, 95%CI: 1.54-6.23, P<0.05), and Grade Ⅱ-Ⅲ grade (HR=2.47, 95%CI: 1.26-4.86,P<0.05). Conclusion: Distant metastasis, mainly pulmonary metastasis, affects the long-term prognosis of patients with ACC significantly. Primary site, T stage and histopathological grade can be used as the predictors for the risk of lung metastasis.

["Point line anterograde dissection" for the safe preparation of supraclavicular flap]

Objective: To investigate the application in the preparation of supraclavicular island flap by "point line anterograde dissection (PLAD) ". Methods: A retrospective analysis was performed on 45 flaps of 43 patients treated with supraclavicular artery island flap from the Department of Otorhinolaryngology Head and Neck Surgery, Beijing Tongren Hospital Affiliated to Capital Medical University from January 2013 to June 2019. The patients were all male, aged 35-72 years old. There were 26 cases of hypopharyngeal cancer, 4 cases of recurrent laryngeal cancer, 2 cases of cervical esophageal cancer, 1 case of tonsillar cancer, 1 case of parotid gland cancer, 3 cases of postoperative pharyngeal fistula after hypopharyngeal cancer, 2 cases of esophageal fistula after trauma, 2 cases of esophageal stricture after hypopharyngeal carcinoma operation, 1 case of autoimmune laryngeal stenosis, and 1 case of cheek defect after maxillary sinus cancer operation."Point" was the origin of the supraclavicular artery in the transverse carotid artery. "Line" was an extension line made along the starting point of the supraclavicular vessel for anterograde anatomy of 1-2 cm and the direction of the blood vessel. The extension line was used as the central axis of the designed island flap. Characteristics of flap blood supply, the time of flap preparation, flap survival, donor area recovery and clinical follow-up were recorded. Results: The arterial blood supply of the flap was constant, and the venous reflux was variable. The area of the prepared flap was (4-8) cm×(10-18) cm, and the preparation time was 30-60 min, with a median of 42 min. Skin flap survival rate was 100%. Partial necrosis of skin flap occurred in 1 patient and postoperative pharyngeal fistula occurred in 5 patients, all of whom were cured by dressing change. The donor site defects were closed and sutured directly. 3 patients had partial incision dehiscence and healed after dressing change. During the follow-up, 1 patient was lost, and the remaining 42 patients were followed up for 8 to 55 months.40 patients involved swallowing function, all of them returned to regular diet or soft fluid after operation.40 patients involved malignant tumors and local tumor recurrence in 3 patients among whom, there were 2 cases of lymph node recurrence, and 2 cases of distant metastasis, including 1 case of lung metastasis and 1 case of bone metastasis. Conclusion: PLAD is a simple, safe and efficient method for the preparation of supraclavicular island flap.

[Rapid identification of Gekko gecko by loop-mediated isothermal amplification based on 12S rRNA sequence]

Gekko gecko (Tokay Gecko) is a valuable traditional Chinese medicine. In this study, the loop-mediated isothermal amplification (LAMP) technique was introduced for visual rapid identification of G. gecko from adulterants. A total of sixty-five 12S rRNA sequences of fourteen species of G. gecko and its adulterants were obtained. The results showed that G. gecko could be identified from its adulterants through BLAST analysis based on 12S rRNA regions. The 12S rRNA sequences of ten batches of G. gecko were conserved. There were only two haplotypes and three variation sites in the available regions for primers design. Six specific LAMP primers were successfully designed online based on 12S rRNA sequences. The visual rapid detection of G. gecko could be achieved with the optimized conditions (64 °C for 1 h and 80 °C for 5 min). And the required minimal template concentration was 5 μg·L⁻¹ while conventional PCR with 0.5 mg·L⁻¹. Consequently, the LAMP method established from this study was rapid, specific, highly sensitive, and simple. It could be applied to detect G. gecko from its adulterants efficiently.

[Statues and research strategy of molecular breeding in Artemisia annua]

Malaria is one of the three most deadly diseases in the world. Artemisinin is the first line and effective drug for treating malaria, and only can be extracted from Artemisia annua. Therefore, it is of great significance to cultivate new varieties of A. annua with high artemisinin content. Based on the germplasm bank and the whole genome, transcriptome and genetic map, the authors can explore high-quality genes, stress-resistant genes and genetic markers which have been used for rapid breeding of superior varieties of A. annua. So these methods of molecular breeding will become the main breeding direction of A. annua in the future. The breeding times of new varieties of A. annua can be shortened with molecular breeding technology. Based on the genetic background and the current situation of molecular breeding of A. annua, the strategy and technical route of molecular breeding were discussed and worked out in this paper, which provided a guidance and scientific reference for molecular breeding of A. annua in the future.

Diagnostics for fast ignition science (invited)

The ignition concept for electron fast ignition inertial confinement fusion requires sufficient energy be transferred from an approximately 20 ps laser pulse to the compressed fuel via approximately MeV electrons. We have assembled a suite of diagnostics to characterize such transfer, simultaneously fielding absolutely calibrated extreme ultraviolet multilayer imagers at 68 and 256 eV; spherically bent crystal imagers at 4.5 and 8 keV; multi-keV crystal spectrometers; MeV x-ray bremmstrahlung, electron and proton spectrometers (along the same line of sight), and a picosecond optical probe interferometer. These diagnostics allow careful measurement of energy transport and deposition during and following the laser-plasma interactions at extremely high intensities in both planar and conical targets. Together with accurate on-shot laser focal spot and prepulse characterization, these measurements are yielding new insights into energy coupling and are providing critical data for validating numerical particle-in-cell (PIC) and hybrid PIC simulation codes in an area crucial for fast ignition and other applications. Novel aspects of these diagnostics and how they are combined to extract quantitative data on ultrahigh intensity laser-plasma interactions are discussed.

Oral glucose augments the counterregulatory hormone response during insulin-induced hypoglycemia in humans

It has been suggested that the counterregulatory hormone (CRH) response to acute hypoglycemia is triggered via glucose sensors situated in either the hypothalamus or the portohepatic area. If the latter were critical during hypoglycemia, one would anticipate that ingestion of glucose, by raising glucose levels in the portal circulation, should attenuate CRH responses previously described in animal studies. To evaluate the effect of raising portal, but not peripheral, glucose levels during insulin-induced hypoglycemia, we performed hypoglycemic clamp studies in five healthy adult males on two occasions. On one occasion, subjects received oral glucose (OG) (25 g) during hypoglycemia; and on one occasion, noncarbohydrate-containing drink of equal volume, while maintaining plasma glucose at 55 +/- 2 mg/dL (3.08 mmol/L). As a result, there were no significant differences in systemic plasma glucose levels between the two hypoglycemic clamp studies, and basal CRH concentrations were also similar. As expected, there was a brisk rise in all CRH during the control (hypoglycemia+noncarbohydrate drink) study. In the experimental study, administration of OG (hypoglycemia+OG), to raise intraportal glucose levels during systemic hypoglycemia, did not attenuate CRH responses. Indeed, OG enhanced the rise in epinephrine, glucagon, and GH. Increases in cortisol and norepinephrine did not differ between the two studies. Therefore, our data suggest that increasing the level of glucose in the portal vein above that in the systemic circulation, during hypoglycemia, enhances (rather than suppresses) CRH responses. Thus, ingestion of glucose may reverse hypoglycemia directly by provision of substrate, as well as indirectly by stimulating counteregulatory mechanisms.

Mechanism of extracellular calcium regulation of intestinal epithelial tight junction permeability: role of cytoskeletal involvement

Recent studies suggest that an abnormal increase in intestinal tight junction (TJ) permeability may be an important etiologic factor in number of diseases including Crohn's disease, NSAID-associated enteritis, and various infectious diarrheal syndromes. The intracellular processes involved in regulation of intestinal epithelial TJ permeability, however, remain poorly understood. In this study, we used cultured Caco-2 intestinal epithelial cells to examine the intracellular processes involved in extracellular Ca(++) modulation of intestinal epithelial monolayer TJ barrier. Incubation of the filter-grown Caco-2 intestinal monolayers in Ca(++)-free solution (CFS), consisting of modified Krebs-buffer solution containing 0 mM Ca(++) and 1 mM EGTA, resulted in a rapid drop in Caco-2 epithelial resistance and increase in epithelial permeability to paracellular markers mannitol and inulin, indicating an increase in TJ permeability. The increase in Caco-2 TJ permeability was rapidly reversed by the re-introduction of Ca(++) (1.8 mM) into the incubation medium. The CFS-induced increase in Caco-2 TJ permeability was associated with separation of the cytoplasmic and transmembrane TJ proteins, ZO-1 and occludin, and formation of large intercellular openings between the adjoining cells. The CFS-induced modulation of TJ barrier was associated with activation of myosin light chain kinase (MLCK) activity and centripetal retraction of peri-junctional actin and myosin filaments. The inhibition of CFS-induced activation of Caco-2 MLCK with MLCK inhibitor (ML-7) prevented the CFS-induced retraction of actin and myosin filaments and the subsequent alteration of TJ barrier function and structure. Our results suggested that the CFS-induced alteration of TJ proteins and functional increase in TJ permeability was mediated by Caco-2 MLCK activation and the resultant contraction of the peri-junctionally located actin-myosin filaments. Consistent with the role of MLCK in this process, selected inhibitors of Mg(++)-myosin ATPase and metabolic energy, but not protein synthesis inhibitors, also prevented the CFS-induced retraction of actin and myosin filaments and the subsequent increase in TJ permeability. In conclusion, our results indicate that extracellular Ca(++) is crucial for the maintenance of intestinal epithelial TJ barrier function. The removal of extracellular Ca(++) from the incubation medium causes activation of Caco-2 MLCK, which in turn leads to an increase in intestinal monolayer TJ permeability.

Mechanism of extracellular calcium regulation of intestinal epithelial tight junction permeability: role of cytoskeletal involvement

Recent studies suggest that an abnormal increase in intestinal tight junction (TJ) permeability may be an important etiologic factor in number of diseases including Crohn's disease, NSAID-associated enteritis, and various infectious diarrheal syndromes. The intracellular processes involved in regulation of intestinal epithelial TJ permeability, however, remain poorly understood. In this study, we used cultured Caco-2 intestinal epithelial cells to examine the intracellular processes involved in extracellular Ca(++) modulation of intestinal epithelial monolayer TJ barrier. Incubation of the filter-grown Caco-2 intestinal monolayers in Ca(++)-free solution (CFS), consisting of modified Krebs-buffer solution containing 0 mM Ca(++) and 1 mM EGTA, resulted in a rapid drop in Caco-2 epithelial resistance and increase in epithelial permeability to paracellular markers mannitol and inulin, indicating an increase in TJ permeability. The increase in Caco-2 TJ permeability was rapidly reversed by the re-introduction of Ca(++) (1.8 mM) into the incubation medium. The CFS-induced increase in Caco-2 TJ permeability was associated with separation of the cytoplasmic and transmembrane TJ proteins, ZO-1 and occludin, and formation of large intercellular openings between the adjoining cells. The CFS-induced modulation of TJ barrier was associated with activation of myosin light chain kinase (MLCK) activity and centripetal retraction of peri-junctional actin and myosin filaments. The inhibition of CFS-induced activation of Caco-2 MLCK with MLCK inhibitor (ML-7) prevented the CFS-induced retraction of actin and myosin filaments and the subsequent alteration of TJ barrier function and structure. Our results suggested that the CFS-induced alteration of TJ proteins and functional increase in TJ permeability was mediated by Caco-2 MLCK activation and the resultant contraction of the peri-junctionally located actin-myosin filaments. Consistent with the role of MLCK in this process, selected inhibitors of Mg(++)-myosin ATPase and metabolic energy, but not protein synthesis inhibitors, also prevented the CFS-induced retraction of actin and myosin filaments and the subsequent increase in TJ permeability. In conclusion, our results indicate that extracellular Ca(++) is crucial for the maintenance of intestinal epithelial TJ barrier function. The removal of extracellular Ca(++) from the incubation medium causes activation of Caco-2 MLCK, which in turn leads to an increase in intestinal monolayer TJ permeability.

Cytochalasin B modulation of Caco-2 tight junction barrier: role of myosin light chain kinase

The intracellular mechanisms that mediate cytochalasin-induced increase in intestinal epithelial tight junction (TJ) permeability are unclear. In this study, we examined the involvement of myosin light chain kinase (MLCK) in this process, using the filter-grown Caco-2 intestinal epithelial monolayers. Cytochalasin B (Cyto B) (5 microg/ml) produced an increase in Caco-2 MLCK activity, which correlated with the increase in Caco-2 TJ permeability. The inhibition of Cyto B-induced MLCK activation prevented the increase in Caco-2 TJ permeability. Additionally, myosin-Mg(2+)-ATPase inhibitor and metabolic inhibitors (which inhibit MLCK induced actin-myosin contraction) also prevented the Cyto B-induced increase in Caco-2 TJ permeability. Cyto B caused a late-phase (15-30 min) aggregation of actin fragments into large actin clumps, which was also inhibited by MLCK inhibitors. Cyto B produced a morphological disturbance of the ZO-1 TJ proteins, visually correlating with the functional increase in Caco-2 TJ permeability. The MLCK and myosin-Mg(2+)-ATPase inhibitors prevented both the functional increase in TJ permeability and disruption of ZO-1 proteins. These findings suggested that Cyto B-induced increase in Caco-2 TJ permeability is regulated by MLCK activation.

Mechanism of extracellular calcium regulation of intestinal epithelial tight junction permeability: role of cytoskeletal involvement

Recent studies suggest that an abnormal increase in intestinal tight junction (TJ) permeability may be an important etiologic factor in number of diseases including Crohn's disease, NSAID-associated enteritis, and various infectious diarrheal syndromes. The intracellular processes involved in regulation of intestinal epithelial TJ permeability, however, remain poorly understood. In this study, we used cultured Caco-2 intestinal epithelial cells to examine the intracellular processes involved in extracellular Ca(++) modulation of intestinal epithelial monolayer TJ barrier. Incubation of the filter-grown Caco-2 intestinal monolayers in Ca(++)-free solution (CFS), consisting of modified Krebs-buffer solution containing 0 mM Ca(++) and 1 mM EGTA, resulted in a rapid drop in Caco-2 epithelial resistance and increase in epithelial permeability to paracellular markers mannitol and inulin, indicating an increase in TJ permeability. The increase in Caco-2 TJ permeability was rapidly reversed by the re-introduction of Ca(++) (1.8 mM) into the incubation medium. The CFS-induced increase in Caco-2 TJ permeability was associated with separation of the cytoplasmic and transmembrane TJ proteins, ZO-1 and occludin, and formation of large intercellular openings between the adjoining cells. The CFS-induced modulation of TJ barrier was associated with activation of myosin light chain kinase (MLCK) activity and centripetal retraction of peri-junctional actin and myosin filaments. The inhibition of CFS-induced activation of Caco-2 MLCK with MLCK inhibitor (ML-7) prevented the CFS-induced retraction of actin and myosin filaments and the subsequent alteration of TJ barrier function and structure. Our results suggested that the CFS-induced alteration of TJ proteins and functional increase in TJ permeability was mediated by Caco-2 MLCK activation and the resultant contraction of the peri-junctionally located actin-myosin filaments. Consistent with the role of MLCK in this process, selected inhibitors of Mg(++)-myosin ATPase and metabolic energy, but not protein synthesis inhibitors, also prevented the CFS-induced retraction of actin and myosin filaments and the subsequent increase in TJ permeability. In conclusion, our results indicate that extracellular Ca(++) is crucial for the maintenance of intestinal epithelial TJ barrier function. The removal of extracellular Ca(++) from the incubation medium causes activation of Caco-2 MLCK, which in turn leads to an increase in intestinal monolayer TJ permeability.

Mechanism of extracellular calcium regulation of intestinal epithelial tight junction permeability: role of cytoskeletal involvement

Recent studies suggest that an abnormal increase in intestinal tight junction (TJ) permeability may be an important etiologic factor in number of diseases including Crohn's disease, NSAID-associated enteritis, and various infectious diarrheal syndromes. The intracellular processes involved in regulation of intestinal epithelial TJ permeability, however, remain poorly understood. In this study, we used cultured Caco-2 intestinal epithelial cells to examine the intracellular processes involved in extracellular Ca(++) modulation of intestinal epithelial monolayer TJ barrier. Incubation of the filter-grown Caco-2 intestinal monolayers in Ca(++)-free solution (CFS), consisting of modified Krebs-buffer solution containing 0 mM Ca(++) and 1 mM EGTA, resulted in a rapid drop in Caco-2 epithelial resistance and increase in epithelial permeability to paracellular markers mannitol and inulin, indicating an increase in TJ permeability. The increase in Caco-2 TJ permeability was rapidly reversed by the re-introduction of Ca(++) (1.8 mM) into the incubation medium. The CFS-induced increase in Caco-2 TJ permeability was associated with separation of the cytoplasmic and transmembrane TJ proteins, ZO-1 and occludin, and formation of large intercellular openings between the adjoining cells. The CFS-induced modulation of TJ barrier was associated with activation of myosin light chain kinase (MLCK) activity and centripetal retraction of peri-junctional actin and myosin filaments. The inhibition of CFS-induced activation of Caco-2 MLCK with MLCK inhibitor (ML-7) prevented the CFS-induced retraction of actin and myosin filaments and the subsequent alteration of TJ barrier function and structure. Our results suggested that the CFS-induced alteration of TJ proteins and functional increase in TJ permeability was mediated by Caco-2 MLCK activation and the resultant contraction of the peri-junctionally located actin-myosin filaments. Consistent with the role of MLCK in this process, selected inhibitors of Mg(++)-myosin ATPase and metabolic energy, but not protein synthesis inhibitors, also prevented the CFS-induced retraction of actin and myosin filaments and the subsequent increase in TJ permeability. In conclusion, our results indicate that extracellular Ca(++) is crucial for the maintenance of intestinal epithelial TJ barrier function. The removal of extracellular Ca(++) from the incubation medium causes activation of Caco-2 MLCK, which in turn leads to an increase in intestinal monolayer TJ permeability.

Pulmonary arteriovenous malformations: cerebral ischemia and neurologic manifestations

BACKGROUND

There is an increasingly recognized association between pulmonary arteriovenous malformations (PAVM) and cerebral ischemia, frequently attributed to paradoxical embolization. PAVM occur in 20 to 30% of the hereditary hemorrhagic telangiectasia (HHT) population.

OBJECTIVE

To evaluate the risk determinants for cerebral ischemia and neurologic manifestations in patients with PAVM.

METHODS

A retrospective cross-sectional study was performed on consecutive patients admitted between 1988 and 1992 for treatment of PAVM. The number of PAVM, feeding artery (FA) diameters, and aneurysmal sizes were determined by pulmonary angiography. Patients were categorized as having single or multiple PAVM with an FA diameter of > or = 3 mm. History, examination, and cerebral imaging studies were used to determine the prevalence of neurologic manifestations. Patients were defined as having cerebral paradoxical embolization if there was radiologic evidence of cortical infarction.

RESULTS

There were 75 cases: 26 single PAVM and 49 multiple PAVM. Cortical infarction was present in 14% of patients with single PAVM. Patients with multiple PAVM had a greater prevalence of any infarction (OR 3.2; 95% CI, 1.2 to 9.44, p = 0.030), cortical infarctions (OR 2.3; 95% CI, 0.58 to 9.2, p = 0.230), subcortical infarctions (OR 2.1; 95% CI, 0.58 to 7.95, p = 0.249), abscesses (OR 2.3; 95% CI, 0.46 to 11.94; p = 0.295), and seizures (OR 6.4, 95% CI 0.77 to 53.2, p = 0.054). Patients with multiple PAVM had markedly greater odds of having any clinical or radiologic evidence of cerebral ischemic involvement (OR 4.5; 95% CI, 1.47 to 14; p = 0.008).

CONCLUSION

There is a strong association between single PAVM and various neurologic manifestations. The prevalence is greater for patients with multiple PAVM, suggesting increased predisposition for paradoxical embolization with a greater number of malformations.

Eicosanoids and the small intestine

Prostaglandins play an important role in modulation of various physiologic processes in the small intestine. In this review, the involvement of prostaglandins in various small-intestinal functions including small-intestinal secretion, mucosal protection, epithelial and endothelial barrier function, and motility are discussed.

Basic fibroblast growth factor stimulates repair of wounded hepatocyte monolayer: modulatory role of protein kinase A and extracellular matrix

The two important repair mechanisms after hepatocyte injury are proliferation and migration of the nearby healthy hepatocytes. Although previous studies have shown that basic fibroblast growth factor (bFGF) levels are markedly elevated after liver injury, the role of bFGF in the repair of the wounded hepatocytes is not well understood. The aim of this study was to delineate the role of bFGF in the repair of the wounded hepatocyte monolayers. Specifically, we examined the role of bFGF in cellular proliferation and migration of hepatocytes with an in vitro wound model. Standardized excisional wounds were created in clone 9 rat hepatocyte monolayers by a razor blade, and the extent of epithelial proliferation and migration was measured. After wound formation, bFGF (30 ng/mL) significantly stimulated proliferation of hepatocytes at the wound margin. bFGF also stimulated the migration of hepatocytes at the wound front. bFGF stimulation of hepatocyte migration correlated with increased formation of actin stress fibers and bFGF-receptor protein level. The bFGF stimulation of hepatocyte migration was abolished by various protein kinase A activating agents including 3-isobutyl-1-methylxanthine, 8-bromoadenosine-3', 5'-cyclic monophosphate, forskolin, and cholera toxin. In addition, protein kinase A activating agents almost completely prevented bFGF-induced actin stress fiber formation in the cells at the wound front. Varying the basement membrane composition of the extracellular matrix had a selective enhancing effect on the basal rates of hepatocyte migration (collagen IV > or = laminin > collagen I > fibronectin > control (plastic)). bFGF treatment resulted in a similar additive increase in hepatocyte migration across all coated surfaces studied. We conclude that bFGF promotes hepatocyte wound repair by stimulating both proliferation and migration of the hepatocyte at the margin of the wound.

Ethanol modulation of intestinal epithelial tight junction barrier

Previous studies have shown that high concentrations of ethanol (>/=40%) cause functional damage of the gastrointestinal epithelial barrier by direct cytotoxic effect on the epithelial cells. The effects of lower noncytotoxic doses of ethanol on epithelial barrier function are unknown. A major function of gastrointestinal epithelial cells is to provide a barrier against the hostile substances in the gastrointestinal lumen. The apicolaterally located tight junctions (TJs) form a paracellular seal between the lateral membranes of adjacent cells and act as a paracellular barrier. In this study, we investigated the effects of lower doses of ethanol on intestinal epithelial TJ barrier function using filter-grown Caco-2 intestinal epithelial monolayers. The Caco-2 TJ barrier function was assessed by measuring epithelial resistance or paracellular permeability of the filter-grown monolayers. Ethanol (0, 1, 2.5, 5, 7.5, and 10%) produced a dose-related drop in Caco-2 epithelial resistance and increase in paracellular permeability. Ethanol also produced a progressive disruption of TJ protein (ZO-1) with separation of ZO-1 proteins from the cellular junctions and formation of large gaps between the adjacent cells. Ethanol, at the doses used (</=10%), did not cause cytotoxicity (lactate dehydrogenase release) to the Caco-2 cells. Ethanol produced a disassembly and displacement of perijunctional actin and myosin filaments from the perijunctional areas. On ethanol removal, actin and myosin filaments rapidly reassembled at the cellular borders. Ethanol stimulated the Caco-2 myosin light chain kinase (MLCK) activity but did not affect the MLCK protein levels. Specific MLCK inhibitor ML-7 inhibited both ethanol increases in MLCK activity and TJ permeability without affecting the MLCK protein levels. Consistent with these findings, metabolic inhibitors sodium azide and 2,4-dinitrophenol significantly prevented ethanol-induced increase in Caco-2 TJ permeability, whereas cycloheximide or actinomycin D had no effect. The results of this study indicate that ethanol at low noncytotoxic doses causes a functional and structural opening of the Caco-2 intestinal epithelial TJ barrier by activating MLCK.

Riboflavin uptake by the human-derived liver cells Hep G2: mechanism and regulation

The water-soluble vitamin riboflavin (RF) plays a critical role in many metabolic reactions, and thus, is essential for normal cellular functions and growth. The liver plays a central role in normal RF metabolism and is the site of maximal utilization of the vitamin. The mechanism of liver uptake of RF has been studied in animals, but no information is available describing the mechanism of the vitamin uptake in the human situation and its cellular regulation. In this study, we used the human-derived liver cells Hep G2 as an in vitro model system to address these issues. Uptake of RF by Hep G2 cells was found to be temperature- and energy-dependent but Na+-independent in nature. Uptake seemed to involve a carrier-mediated process as indicated by the saturation as a function of substrate concentration (apparent Km 0.41 +/- 0.08 microM), and by the ability of the structural analogs lumiflavin and lumichrome to inhibit the uptake process [inhibition constant (K) of 1.84 and 6.32 microM, respectively]. RF uptake was energy dependent, and was inhibited by the -SH group blocker p-chloromercuriphenylsulfonate (p-CMPS) (Ki of 0.10 mM). Specific modulators of intracellular protein kinase A (PKA)-, protein kinase C (PKC)-, and protein tyrosine kinase (PTK)-mediated pathways did not affect RF uptake by Hep G2 cells. On the other hand, specific inhibitors of Ca2+/calmodulin-mediated pathway significantly inhibited the uptake process; this effect seemed to be mediated through a decrease in the Vmax of the substrate uptake process. Maintaining Hep G2 cells in a RF-deficient growth medium was associated with a significant up-regulation in the substrate uptake; this effect was specific for RF and was mediated mainly by means of an increase in the Vmax of the uptake process. These results describe, for the first time, the mechanism and cellular regulation of RF uptake by a human-derived liver cellular preparation, and shows the involvement of a carrier-mediated system in the uptake process. Furthermore, the uptake process seems to be regulated by an intracellular Ca2+/calmodulin-mediated pathway and by extracellular substrate levels.

Total parenteral nutrition via multilumen catheters does not increase the risk of catheter-related sepsis: a randomized, prospective study

The purpose of this study was to determine in a randomized, prospective manner whether administration of total parenteral nutrition (TPN) via multilumen catheters increases the risk of catheter-related sepsis (CRS). All patients receiving hyperalimentation during a 24-month period were randomized to receive either a double-lumen catheter (DLC) or a triple-lumen catheter (TLC). A total of 101 catheters were placed in 79 patients, of which 49 were DLCs and 52 were TLCs. The patients with DLCs received a total of 784 days of TPN, whereas patients with TLCs received a total of 754 days of TPN. CRS was associated with one (2.0%) of the 49 DLCs vs. one (1.9%) of the 52 TLCs. In comparison, the rate of CRS associated with single-lumen catheters (historical control) at our institution was 1.4% (P > .90). We conclude that the use of multilumen catheters in TPN therapy does not result in an increased risk of CRS.

Intestinal epithelial barrier dysfunction in Crohn's disease

Despite extensive research, the etiology of Crohn's disease remains unknown. Accumulating evidence suggests the possibility that a primary defect of intestinal barrier function may be present in Crohn's disease. In this review, the possible role of intestinal barrier defect in Crohn's disease is discussed. It has been recognized for some time that Crohn's patients have a defective intestinal epithelial barrier function manifested by an increase in intestinal permeability. Recent studies indicate that a subgroup of healthy first-degree relatives of Crohn's patients (a population at high risk for developing Crohn's disease) also have increased intestinal permeability. Additionally, this subgroup of patients have evidence of increased exposure to foreign antigens, suggesting a possible link between increase in intestinal permeability and increase in antigenic penetration. Furthermore, exacerbation of Crohn's disease is produced by agents that disrupt intestinal epithelial barrier function, while remission of active disease is induced by decreasing intestinal antigenic load. A "leaky gut" hypothesis is advanced which proposes that a preexisting disorder of intestinal permeability is responsible for the intestinal inflammation of Crohn's disease.

Role of protein kinase a pathway in epidermal growth factor-induced liver cell repair

To gain a better understanding of the mechanisms that control the repair process in the injured liver, the actions of epidermal growth factor (EGF) and protein kinase A (PKA) were studied. Normal rat liver cells (clone 9) were grown to confluence. Standardized excisional wounds were made with a razor blade. The extent of hepatocyte migration into the wound was measured and determined at specific time intervals using a computerized digital analyzing system. Immunostaining of F-actin was performed with a fluorescein-labeled phalloidin. EGF significantly stimulated liver cell migration, whereas specific EGF-neutralizing antibody inhibited the EGF-induced migration. Agents that activate PKA at different stages of the PKA activation pathway, including 3-isobutyl-1-methylxanthine (IBMX), forskolin, and cholera toxin, inhibited EGF-induced migration. EGF triggered formation of actin stress fibers. PKA-activating agents inhibited actin stress fiber formation and stretching of cells at the wound margin. The following conclusions were drawn: (1) In excisional wounds of hepatocyte monolayers, both EGF and PKA exert action on actin microfilaments, which are stretched by EGF and inhibited by PKA; (2) the enhanced repair of wounded hepatocyte monolayers by EGF is blocked by activation of the PKA pathway at various levels; and (3) these actions of EGF and PKA indicate their important regulatory roles in controlling the rate of hepatocyte migration and restitution following the creation of excisional wounds.

Intracellular regulation of intestinal folate uptake: studies with cultured IEC-6 epithelial cells

Although the mechanism of folate uptake in the small intestine has been well characterized, very little is known about the intracellular regulation of the uptake process. Using mature confluent monolayers of the intestinal epithelial cell line IEC-6 as an in vitro intestinal epithelial cell model, we have found the uptake of folic acid to be similar to that of the native small intestine in that it is 1 ) temperature, energy, and pH dependent, 2) Na+ independent, 3) inhibited by structural analogs and anion transport inhibitors, and 4) saturable as a function of substrate concentration [apparent Michaelis constant (Km) = 0.45 +/- 0.06 microM; maximal velocity (Vmax) = 3.08 +/- 0.14 pmol x mg protein(-1) x 5 min(-1)]. Furthermore, IEC-6 cells were found by Northern blot analysis to lack the expression of the membrane folate-binding protein. Pretreatment of IEC-6 monolayers with specific protein tyrosine kinase (PTK) inhibitors genistein and tyrphostin A25 caused a significant inhibition in folic acid uptake. On the other hand, their negative controls, genistin and tyrphostin A1, respectively, had no effect. The inhibitory effect of genistein was mediated through inhibition in the Vmax of the folate uptake process with no change in the apparent Km. Pretreatment of IEC-6 monolayers with compounds that increase intracellular adenosine 3',5'-cyclic monophosphate (cAMP) level (e.g., dibutyryl cAMP) also resulted in a significant (though modest) inhibition in folic acid uptake; however, specific inhibitors of protein kinase A did not affect the uptake process. Specific modulators of protein kinase C and Ca2+/calmodulin-mediated pathways did not significantly affect folic acid uptake. These results demonstrate the suitability of IEC-6 monolayers as an intestinal epithelial model to study folate transport and demonstrate for the first time that uptake of folic acid is regulated by a PTK- and a cAMP-mediated pathway.

Uptake of L-carnitine by a human intestinal epithelial cell line, Caco-2

BACKGROUND & AIMS

The mechanism of intestinal uptake of L-carnitine is controversial. The aim of this study was to clarify the mechanism and regulation of L-carnitine uptake.

METHODS

Uptake of [3H]-L-carnitine was measured across the apical membrane of confluent monolayers of Caco-2 cells.

RESULTS

[3H]-L-carnitine uptake was linear and appreciable for up to 7 minutes with minimal metabolic alteration, was temperature- and Na(+)-(but not pH-) dependent, and included a saturable component with an apparent Michaelis constant of 45.5 +/- 6.5 mumol/L and a maximum velocity of 83.5 +/- 5.6 nmol.mg protein-1.5 min-1. Unlabeled L-carnitine and its structurally related analogues significantly (P < 0.01) inhibited [3H]-L-carnitine uptake, whereas unrelated compounds were ineffective. L-Carnitine uptake was also energy-dependent, being significantly (P < 0.01) inhibited by metabolic inhibitors. Our results also suggested that a calmodulin- but not a protein kinase C- or protein kinase A-mediated pathway plays a role in regulating L-carnitine uptake by Caco-2 cells.

CONCLUSIONS

L-carnitine uptake by intestinal epithelial cells (Caco-2) involves a carrier-mediated system that is temperature-, Na(+)-, and energy-dependent and seems to be under the regulation of a calmodulin-mediated pathway.

16,16-Dimethyl Prostaglandin E2 modulation of endothelial monolayer paracellular barrier function

Prostaglandins prevent gastrointestinal mucosal injury and promote healing following mucosal injury by various noxious agents. Preservation or repair of microvascular function appears to be crucial in these processes. The processes involved in prostaglandin-mediated repair and preservation of endothelial function are unclear. In the present study, we investigated the role of prostaglandins on endothelial paracellular barrier function using the filter-grown bovine aortic endothelial cell monolayers. Endothelial paracellular barrier function as assessed using a paracellular marker, mannitol. Prostaglandin analogs 16,16-dimethyl prostaglandin E2 (DMPGE2) and prostaglandin I2 (PGI2) caused an enhancement of endothelial monolayer paracellular barrier function as evidenced by a dose-dependent decrease in endothelial paracellular permeability. DMPGE2 induced enhancement of endothelial paracellular barrier function correlated directly with increasing intracellular cAMP levels. Agents which increase intracellular cAMP levels at different stages of cAMP amplification cascade including phosphodiesterase inhibitor (3-isobutyl-1 methylxanthine [IBMX]), membrane permeable cAMP (8-bromo cAMP), and adenylate cyclase activators (isoproterenol and forskolin) also produced enhancement in endothelial paracellular barrier function. DMPGE2 enhancement of paracellular barrier function correlated with dense accumulation of actin microfilaments near the intercellular junctions. IBMX, isoproterenol, forskolin, and 8-bromo cAMP also produced similar changes in endothelial actin microfilaments. Cytochalasin B prevented the DMPGE2 enhancement of paracellular barrier function. Indomethacin (INDO), a cyclooxygenase inhibitor, caused a dose-dependent increase in endothelial paracellular permeability. Pharmacologic doses of INDO resulted in condensation and disruption of actin microfilaments with formation of large paracellular openings or gaps between the adjacent cells. Pretreatment of endothelial monolayers with DMPGE2 prevented INDO-induced disturbance of actin microfilaments and paracellular barrier function. IBMX, isoproterenol, forskolin, and 8-bromo cAMP also prevented INDO-induced changes in actin microfilaments and paracellular barrier function. These findings indicate that DMPGE2 has a paracellular barrier enhancing effect on filter-grown endothelial monolayers. This effect appears to be mediated through intracellular cAMP and actin microfilaments.

Cytoskeletal regulation of Caco-2 intestinal monolayer paracellular permeability

An abnormal increase in intestinal paracellular permeability may be an important pathogenic factor in various intestinal diseases. The intracellular factors and processes that regulate and cause alteration of intestinal paracellular permeability are not well understood. The purpose of this study was to examine some of the intracellular processes involved in cytoskeletal regulation of intestinal epithelial paracellular permeability using the filter-grown Caco-2 intestinal epithelial monolayers. Cytochalasin-b and colchicine were used to disrupt the cytoskeletal elements, actin microfilaments, and microtubules. Cytochalasin-b (5 micrograms/ml) and colchicine (2 x 10(-5) M) at the doses used caused marked depolymerization and disruption of actin microfilaments and microtubules, respectively. Cytochalasin-b-induced disruption of actin microfilaments resulted in perturbation of tight junctions and desmosomes and an increase in Caco-2 monolayer paracellular permeability. The cytochalasin-b-induced disruption of actin microfilaments and subsequent changes in intercellular junctional complexes and paracellular permeability were not affected by inhibitors of protein synthesis (actinomycin-D or cycloheximide) or microtubule function (colchicine), but were inhibited by metabolic energy inhibitors (2,4-dinitrophenol or sodium azide). The cytochalasin-b-induced disturbance in Caco-2 actin microfilaments and intercellular junctional complexes and increase in paracellular permeability were rapidly reversed. The paracellular pathway "re-tightening" following cytochalasin-b removal was not affected by actinomycin-D, cycloheximide, or colchicine, but was inhibited by 2,4-dinitrophenol and sodium azide. The colchicine-induced disruption of microtubules did not have significant effect on actin microfilaments, intercellular junctions, or paracellular permeability. These findings suggest that cytochalasin-b-induced increase in Caco-2 monolayer paracellular permeability was due to actin microfilament mediated perturbation of intercellular junctional complexes. The re-tightening of paracellular pathways (following removal of cytochalasin-b) resulted from energy-mediated re-assembly of pre-existing actin microfilaments and intercellular junctional complexes. This re-closure process did not require protein synthesis or microtubule-mediated shuttling process.

Mechanism of colonic permeation of inulin: is rat colon more permeable than small intestine?

BACKGROUND/AIMS

Colonic epithelium is considered to be relatively tight. The colonic "pore" diameter is 6 A; therefore, colonic epithelium has generally been considered to be impermeable to hydrophilic probes with a cross-sectional diameter of > 6 A. This study examined whether rat colon is permeable to inulin, a large hydrophilic macromolecule having a molecular weight of 5000 g/mol and a cross-sectional diameter of 15 A (hydration diameter, 20 A).

METHODS

The colonic permeation of inulin (10 mumol/L) in vivo was investigated by perfusion of rat colonic segments.

RESULTS

There was significant colonic permeation of inulin, but tissue retention of inulin was low. The net colonic flux of inulin was strongly dependent on net water flux, showing a strong solvent drag effect. Addition of 16,16-dimethyl prostaglandin E2 decreased water flux with a corresponding decrease in inulin flux; this process seemed to be mediated by 5'-cyclic adenosine monophosphate because both the phosphodiesterase inhibitor aminophylline and dibutyryl adenosine 5'-cyclic adenosine monophosphate decreased water and inulin flux in a parallel manner. Chenodeoxycholic and taurocholic acids decreased net mucosal-to-serosal water flux but increased inulin flux. The net colonic permeation rate of inulin was higher than the small intestinal permeation rate.

CONCLUSIONS

Rat colon is permeable to inulin. The higher net colonic permeability may be caused by differences in mucosal surface, permselectivity, solvent drag effect, and differences in net water fluxes of the colon and small intestine.

Uptake of biotin by human hepatoma cell line, Hep G2: a carrier-mediated process similar to that of normal liver

Little is known about the cellular and molecular regulation of the uptake process of the water-soluble vitamin biotin into liver cells, the major site of biotin utilization and metabolism. Such studies are best done using a highly viable and homogeneous cellular system that allows examination of prolonged exposure to an agent(s) or a particular condition(s) on the uptake process. Isolated hepatocytes when maintained in primary culture lose their ability to transport biotin by the specialized carrier system. The aim of the present study was, therefore, to examine the mechanism(s) of biotin uptake by the cultured human-derived liver cells, Hep G2. Uptake of biotin by Hep G2 cells was appreciable and linear for up to 10 min of incubation. The uptake process was Na+ gradient-dependent as indicated by studies of Na+ replacement and pretreatment of cells with gramicidin and ouabain. Biotin uptake was also dependent on both incubation temperature and intracellular energy. Unlabeled biotin and the structural analogs with free carboxyl groups (thioctic acid, desthiobiotin) but not those with blocked carboxyl group (biocytin, biotin methyl ester, and thioctic amide) caused significant inhibition of 3H-biotin uptake at 37 degrees C but not 4 degrees C. Initial rate of biotin uptake was saturable as a function of concentration at 37 degrees C but was lower and linear at 4 degrees C. Pretreatment of Hep G2 cells with sulfhydryl group inhibitors (e.g., p-chloromercuribenzene sulfonate) led to a significant inhibition in biotin uptake; this inhibition was effectively reversed by reducing agents (e.g., dithiothreitol). Biotin uptake was also inhibited by the membrane transport inhibitors probenecid (noncompetitively), DIDS and furosemide but not by amiloride. Pretreatment of Hep G2 cells with valinomycin did not alter biotin uptake. The stoichiometric ratio of biotin to Na+ uptake in Hep G2 cells was also determined and found to be 1:1. These findings demonstrate that biotin uptake by these cultured liver cells is mediated through a specialized carrier system that is dependent on Na(+)-gradient, temperature, and energy and transports the vitamin by an electroneutral process. These findings are similar to those seen with native liver tissue preparations and demonstrate the suitability of Hep G2 cells for in-depth investigations of the cellular and molecular regulation of biotin uptake by the liver.

Regulation of riboflavin intestinal uptake by protein kinase A: studies with Caco-2 cells

Although the mechanism of riboflavin (RF) intestinal uptake has been the subject of many studies, virtually nothing is known about the cellular regulation of the uptake process. In the present study, we investigated the role of protein kinase A (PKA)- and C (PKC)-mediated pathways in the regulation of RF intestinal uptake using the confluent Caco-2 monolayers. Treatment of Caco-2 cells with 3-isobutyl-1-methylxanthine (IBMX), forskolin, cholera toxin, or dibutyryl adenosine 3',5'-cyclic monophosphate caused a significant inhibition in RF uptake. The inhibitory effect of IBMX was reversible and resulted from a significant decrease in the maximal velocity of the RF uptake process with no change in its apparent Michaelis constant. The IBMX-induced inhibition in RF uptake was not mediated via inhibition in the synthesis of the RF carrier protein or through inhibition in the recruitment of preexisting carrier protein into the plasma membrane. Calyculin A also inhibited RF uptake when added alone and further potentiated the inhibitory effect of IBMX when added together. Phorbol 12-myristate 13-acetate or chelerythrine, on the other hand, showed no significant effect on RF uptake. These results demonstrate for the first time that compounds that increase intracellular cAMP levels downregulate RF intestinal uptake and that this effect is mediated via a decrease in the activity of the RF uptake carrier. It is suggested that a PKA-mediated pathway(s) plays an important role in regulating RF intestinal uptake.

Mechanisms and sites of mannitol permeability of small and large intestine in the rat

Mannitol is commonly used as an intestinal permeability probe, yet the mechanisms of its penetration of the intestinal barrier are not entirely clear. Therefore, we studied mannitol's permeability of different segments of the intestine and studied the kinetics and influence of intraluminal factors on mannitol permeability in vivo in perfused intestinal segments of rats. There was linear relationship between permeability rate of mannitol and its luminal concentration (y = 7.2x + 1.7; r = 0.98), indicating that passive diffusion is involved in mannitol's permeability. Increased luminal fluid osmolarity from 0.3 to 0.6 osmol/liter resulted in decreased net water flux with a corresponding decrease in mannitol permeability in both jejunum and colon (P < 0.01), indicating the prominent influence of solvent drag on net mannitol permeability. The relationship between mannitol permeability and water absorption at different osmolarities was linear in the jejunum and colon. At luminal osmolarity of 0.3 osmol/liter, 34.6% of mannitol permeability was mediated by passive diffusion and 65.4% was mediated by solvent drag in the jejunum. Mannitol permeability was much more dependent on solvent drag in the colon (88.9%) than in the small intestine (65.4%). The net permeability rate of mannitol was similar in the jejunum and ileum but was much higher in the colon (P < 0.01). Addition of chenodeoxycholate (5 mM) to the perfusate resulted in a significant decrease in absorption of water (P < 0.01) with a corresponding decrease in mannitol permeability (P < 0.01). These studies indicate that mannitol permeability of the intestinal barrier is mediated by passive diffusion and solvent drag, with the latter accounting for a greater fraction of the total permeability.

The utero-placental circulation, eugenics and the prevention and treatment of high risk pregnancies

Through systematic experimental and clinical studies, the physiological regulation of utero-placental circulation and the relation of the disturbance in this acirculation to pathogenic mechanisms of high risk pregnancies-Intrauterine Growth Retardation (IUGR) and Pregnancy-induced hypertension (PIH) were explored. The pharmacological effects and mechanism of a Chinese herbal medicine-Qingxintong in improving, the utero-placental circulation and the therapeutic efficacy in treatment of IUGR and PIH, both accompanied by disturbance of utero-placental circulation, were investigated as well.

Human intestinal cell line Caco-2: a useful model for studying cellular and molecular regulation of biotin uptake

The mechanisms of enterocyte and molecular regulation of biotin uptake are poorly understood. An intestinal cell line processing the transport characteristics of native intestinal cells is highly desirable to investigate the finer details of the cellular processing and molecular regulation of biotin transport. In the present study, we investigated the uptake of the water-soluble vitamin biotin by a human intestinal cell line Caco-2. Uptake of both low (4 nM) and high (20 microM) concentrations of biotin by confluent monolayers of Caco-2 cells was appreciable and linear for up to 10 min of incubation. Replacement of Na+ in the incubation medium with other monovalent cations--K+, choline, Li+ and NH4(+)--caused a significant inhibition of biotin uptake; a relatively lesser inhibition was seen with Li+. Initial rate of uptake of biotin was temperature-dependent and saturable as a function of concentration at 37 degrees C but not at 4 degrees C. The Vmax and apparent Km of the temperature-dependent saturable process were 520 pmol/mg protein per min and 9.5 microM, respectively. The addition of unlabeled biotin and the structural analogue desthiobiotin to the incubation media caused a significant inhibition of the uptake of [3H]biotin. The inhibitory effect of desthiobiotin was competitive in nature with an inhibition constant (Ki) of 41 microM. Biocytin, on the other hand, was a weak inhibitor and biotin methyl ester and diaminobiotin did not have any effect. Pretreatment of Caco-2 cells with the monovalent cation ionophore gramicidin and the Na+, K+(-)ATPase inhibitor ouabain caused significant inhibition of biotin uptake. Pretreatment with the K+ ionophore valinomycin did not affect biotin uptake. Using the 'Activation Method', the stoichiometric ratio of biotin- to Na+ coupling was found to be 1:1. Growing confluent Caco-2 cells in a biotin-deficient environment resulted in rapid up-regulation of biotin transport with a marked increase (258%) in the Vmax of biotin uptake. These findings demonstrate that biotin uptake by Caco-2 cells is via a carrier-mediated system. This system is temperature-dependent, driven by Na(+)-gradient and is regulated by the substrate level. These in-vitro findings are very similar to and further confirm previous findings in human and animal studies and dispute other findings previously reported for Caco-2 cells; the present study also demonstrates the suitability of this system for further characterization of the cellular and molecular regulation of biotin uptake.

Mechanism of riboflavine uptake by Caco-2 human intestinal epithelial cells

The cellular and molecular regulation of intestinal absorption of the water-soluble vitamin riboflavine (RF) is poorly understood. The availability of a suitable in vitro cultured system that possesses the transport characteristics of the native intestinal absorptive cells would provide a powerful means to address this issue. In this study, we examined RF uptake by the human-derived cultured Caco-2 intestinal epithelial cells. RF uptake was Na+ and pH independent and occurred without metabolic alterations of the transported RF. Initial rate of RF uptake was temperature dependent and saturable as a function of concentration at 37 degrees C but not at 4 degrees C (apparent Michaelis constant = 0.30 +/- 0.03 microM, maximal velocity = 209.90 +/- 24.40 pmol.mg protein-1.3 min-1). Unlabeled RF, lumiflavine, 8-amino-riboflavine, isoriboflavine, and lumichrome in the incubation solution caused significant inhibition of RF uptake. RF uptake was also energy dependent and was sensitive to the inhibitory effect of sulfhydryl group reagents. The membrane transport inhibitor amiloride, but not 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, 4-acetamide-4'-isothiocyanostilbene-2,2'-disulfonic acid, furosemide, or probenecid, inhibited RF uptake in a competitive (inhibitory constant = 0.48 mM) and reversible manner. Growing Caco-2 monolayers in a RF-deficient and oversupplemented media caused significant up- and downregulation of RF uptake, respectively. These results demonstrate the existence of a carrier-mediated system for RF uptake by Caco-2 cells and provide new information regarding amiloride sensitivity, involvement of sulfhydryl groups, and up- and downregulation by the substrate level and clarify the controversy regarding the role of Na+ in the uptake process.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoradiographic determination of permeation pathway of permeability probes across intestinal and tracheal epithelia

Mucosal permeability studies are used to assess intestinal and respiratory barrier functions. Our ability to interpret results of permeability studies are hampered by our lack of understanding of absorptive pathways of permeability markers. The aim of this study was to visually trace the pathway of permeability probes across the small intestinal and tracheal epithelia by using electron microscopic autoradiography and cytochemistry. We saw a constant rate of mucosal to serosal permeation of intestinal permeability probes polyethylene glycol 400 (PEG-400) and mannitol across the everted small intestinal sac and of the pulmonary permeability probe bovine serum albumin (BSA) across the tracheal epithelia. Electron microscopic tracing of the permeation pathways of tritiated PEG-400 and tritiated mannitol revealed that the majority of the probes traversed the intestinal epithelium paracellularly within 1 half distance (1650 A) of the intercellular space. It is interesting that we also found a small but significant transcellular transport of permeability probes. Goblet cells also absorbed permeability probes transcellularly, but in an "all or none" fashion. Similar pathways were identified in studies utilizing the commonly used pulmonary permeability probes iodine 125-labeled BSA and horseradish peroxidase to determine the routes of transfer in the airway epithelia. In the normal unperturbed trachea, these large permeability probes traversed the pulmonary epithelia transcellularly via endocytosis. On barrier disruption by cytochalasin D, the probes permeated predominantly via the paracellular pathway. This study also demonstrates some of the similarities and differences in transmucosal pathways shared by intestinal and pulmonary epithelia.

[Effect of 3,4-dihydroxyacetophenone treatment on intrauterine growth retardation]

In this paper, the results of a pilot study of 3,4-dihydroxyacetophenone (DHAP) treatment for intrauterine growth retardation (IUGR) were reported. 20 out of 38 cases of IUGR were treated with DHAP and 18 with amino acid. Additionally, 170 normal pregnant women were served as control group. The following parameters have been observed and measured including uterine fundal height (UFH), body weight (BW), S/D ratio of umbilical artery (UmA), hemorheological indices, platelets aggregation, TXB2/6-keto-PGF1 alpha ratio and also fetal and neonatal various growth indices etc. After administration of DHAP, all the parameters almost restored to the normal range. The results expressed that the therapeutic effect of DHAP was much better than that of amino acid. It has also been verified by neonatal birth weight and fetal biparietal diameter. The clinical effective rate of DHAP treatment group was 90.00% which was significantly higher than that 74.00%, 79.00% of amino-acid treatment group. Meanwhile, the mechanism of DHAP has preliminarily been discussed.

A clinical study of cytomegalovirus infections during pregnancy

Enzyme-linked Immunosorbent Assay (ELISA) was adopted to detect the human cytomegalovirus (HCMV) specific IgG, IgM in the blood samples of 216 pregnant women and the umbilical cord blood, as well as the HCMV antigen in the urine specimens of 91 newborn infants. Emphasis was put on the occurrence of cytomegalovirus infection during pregnancy and influence on both the mother and the infant. Our experimental results showed that HCMV IgG positive rate in the maternal sera as well as in cord sera was 93.98%; HCMV IgM positive rates were 8.8% in maternal sera and 3.7% in cord sera, respectively. In maternal sera IgG-positive group, 31.6% cord sera showed also HCMV IgG positive results. In 91 urine specimens of newborn infants, HCMV-Ag positive specimens accounted for 10.98% (10 cases). The rates of abortion, congenital malformation, stillbirth, premature fetal death, and intrauterine growth retardation (IUGR) were all apparently higher in the HCMV-IgM positive pregnant group than in the HCMV-IgM negative group. The infants of HCMV-IgM positive mothers also showed lower birth weight, height, biparietal diameter, suboccipitobregmatic diameter, occipitofronatal diameter, occipito-mental diameter than the infants of HCMV-IgM negative mothers. Meanwhile, the growth and development indices of the former showed a tendency to decrease. Placenta histological examination showed that HCMV-IgM positive group had a higher incidence of pathological changes than HCMV-IgM negative group. Altogether, there were 8 cases of congenital infections.

IEC-18, a nontransformed small intestinal cell line for studying epithelial permeability

Small intestinal epithelium is leaky and allows permeation of hydrophilic molecules of various sizes. Passively absorbed hydrophilic permeability probes have been shown to permeate across intestinal epithelium mainly through the paracellular pathways. In this study we introduce microporous filter-grown IEC-18 epithelial cells, a nontransformed small intestinal cell line, as a in vitro model of intestinal epithelium for the study of epithelial permeability. IEC-18 cells, originally derived from native rat ileal crypts, form confluent epithelium when grown on hydrated collagen-coated Millicell-CM permeable inserts (Millipore Corp., Bedford, Mass.). With scanning and transmission electron microscopy, the presence of tight junctions and desmosomes between cells and the development of microvilli at the apical surface were confirmed. Immunofluorescent labeling of ZO-1 proteins and desmoplakins verified the presence of tight-junctional proteins (ZO-1) and desmosomes in the intercellular junctions of confluent IEC-18 epithelium. The net electrical resistance of IEC-18 epithelium (28 omega-cm2) was similar to resistance values obtained from small intestinal tissue with (50 to 100 omega-cm2) or without (20 to 45 omega-cm2) muscularis and serosal layers. Assessment of mannitol and dextran permeation revealed early "maturation" of paracellular pathway, with increasing restriction of permeation to both probes through day 4. Resistance across IEC-18 epithelium also reached plateau levels between 4 and 7 days. Permeability studies with various probes indicate that cross-sectional diameter rather than molecular weight of the probe is the important determinant of permeation rate. IEC-18 epithelium selectively restricted the permeation of probes proportional to probe size; permeation of larger probes such as albumin was negligible. We conclude that cultured IEC-18 epithelial cells, because of their native crypt origin, similarity in resistance to small intestinal epithelia, retention of ability to differentiate into villus-like enterocytes, and permeability characteristics, are a useful model of intestinal epithelium for the study of permeability and paracellular transport.

Effect of aging and caloric restriction on intestinal permeability

Intestinal permeability is increased in several disorders such as Crohn's disease or rheumatoid arthritis. Since aging leads to alteration of many biological functions, the effect of aging on intestinal permeability was studied by measuring the intestinal permeability in aging rats gavaged with different size permeability probes--mannitol, polyethylene glycol (PEG) 400, and inulin. In rats fed with control diet, there was a significant increase in intestinal permeability to medium size probes PEG 400 (14.8 +/- 0.4 and 21.0 +/- 1.1% at 3 and 28 months respectively, p less than .01) and mannitol (3.41 +/- 0.4 and 5.3 +/- 0.5% at 3 and 28 months, respectively, p less than .01). Intestinal permeability of the large macromolecule inulin did not change (0.42 +/- 0.03 and 0.38 +/- 0.02% at 3 and 28 months, respectively) with aging. There was no correlation between weight of the rats and their intestinal permeability. Because dietary caloric restriction has been found to prolong the life span, retard deterioration of several biological functions, and affect intestinal absorptive functions, we examined the effect of lifelong calorie restriction on intestinal permeability changes. Lifelong calorie-restricted diet did not affect age-related change in intestinal permeability. We conclude that intestinal permeability of medium size probes increases with aging and that lifelong caloric restriction does not prevent this change. We speculate that age-associated deterioration in intestinal barrier functions could permit increased systemic absorption of lumenal antigens and could perhaps contribute to the genesis of antigen-related age-associated diseases.

Oxygen free radical injury of IEC-18 small intestinal epithelial cell monolayers

Oxygen radicals can cause endothelial and epithelial permeability changes and mucosal injury of the small intestine. There is no clear consensus concerning the relative injurious potential of individual oxygen radicals. In this study, the small intestinal cell line IEC-18 was used as an in vitro model to study the relative injurious effects of reactive oxygen metabolites. By introducing different combinations of oxygen metabolite-producing enzymes, xanthine oxidase, superoxide dismutase, and catalase, and an iron chelator, deferoxamine, to the fully confluent monolayers and to proliferating IEC-18 cells, the differential injurious effects of the oxygen metabolites O2-, H2O2, and OH. could be evaluated. The extent of cellular injury was assessed using [3H]thymidine uptake, 51Cr release, and morphological evaluations. Our results suggest that OH. produced as a by-product of O2- and H2O2 via the Haber-Weiss reaction was the most injurious oxygen species involved in cellular injury of IEC-18 monolayers induced by xanthine oxidase. O2- produced by xanthine oxidase appeared to be only minimally injurious, and H2O2 produced by xanthine oxidase and as a result of conversion of O2- by superoxide dismutase was moderately injurious. Superoxide dismutase and deferoxamine at appropriate concentrations were protective against xanthine/xanthine oxidase-induced monolayer injury. H2O2 added directly or produced indirectly by glucose oxidase was very injurious to the intestinal monolayers, and this injury was mitigated by catalase.

Is the small intestinal epithelium truly "tight" to inulin permeation?

In this study, we evaluated the "leakiness" of intestinal epithelium through examination of small intestinal absorption of inulin in vivo by perfusing rat jejunum with 10 microM inulin. In physiological conditions, we found significant absorption of inulin at a rate of 44.6 nmol.100 cm-1.h-1 or absorption of 14.7%.100 cm-1.h-1 of the amount perfused. Increasing water flux by changing the luminal osmolarity resulted in linear (y = 31.1 + 2.4x, r = 0.97) increase in absorption of inulin, indicating a significant convective component of inulin absorption. There was large permeation of inulin at net water secretion and at zero net water fluxes (31.1 nmol.100 cm-1.h-1), indicating significant absorption of inulin by diffusive movement as well. The small intestinal tissue retention of inulin occurred rapidly within the first 15 min of perfusion, and the total tissue retention remained unchanged thereafter at approximately 10.8 nmol/100 cm. 16,16-Dimethylprostaglandin E2 decreased water flux, whereas cyclooxygenase inhibitors, indomethacin and acetylsalicylate, increased water flux. Inulin absorption closely paralleled changes in water flux induced by these agents. Taurocholate also caused parallel decrease in water and inulin absorption. Varying the resistance of unstirred water layer with changing luminal flow rate, the addition of mucolytic agent acetylcysteine, or alterations of luminal pH did not affect water or inulin absorption. We conclude that inulin permeates the small intestinal epithelium in significant amounts under normal physiological conditions, presumably through the paracellular pathways utilizing aqueous channels.

Polyethylene glycol 400 penetration of the colonic epithelial barrier of the rat

Permeability changes of polyethylene glycol 400 have been seen in patients with inflammatory bowel diseases. Because the colon can be involved in inflammatory bowel disease, the mechanisms, kinetics, and influence of intraluminal factors on polyethylene glycol 400 permeation of perfused colonic segments of rats were studied. The absorption rate of polyethylene glycol 400 was linearly related to its luminal concentration (r = 0.94), suggesting that passive diffusion is a significant mechanism involved in polyethylene glycol 400 absorption. Changing the perfusate pH from 6.0 to 7.5 did not affect water absorption or polyethylene glycol 400 permeation. Increasing luminal osmolarity significantly decreased water and polyethylene glycol 400 absorption (P less than 0.01). The relationship between polyethylene glycol 400 and water absorption at different luminal osmolarities was linear (r = 0.97). At luminal osmolarity of 0.3 osm/L, 14.3% of polyethylene glycol 400 absorption was mediated by passive diffusion and 85.7% was mediated by convection. The solvent drag reflection coefficient for polyethylene glycol 400 in the colon was 0.03. Taurocholic acid (10 mmol/L) and chenodeoxycholic acid (5 mmol/L) decreased polyethylene glycol 400 and water absorption (P less than 0.01). Addition of 1 micrograms/mL of 16,16-dimethyl prostaglandin E2, 2 mmol/L of dibutyryladenosine-3',5'-cyclic monophosphate, or 10 mmol/L of aminophylline significantly decreased water and polyethylene glycol 400 absorption (P less than 0.01). These studies demonstrate that polyethylene glycol 400 permeation of the colon is mediated by both passive diffusion and solvent drag. Convective absorption is the major mechanism of polyethylene glycol 400 permeation of the colon. Polyethylene glycol 400 permeation is modified by bile acids, prostaglandins, and cyclic nucleotides through changes in water flux.

PEG 400, a hydrophilic molecular probe for measuring intestinal permeability

There is a widely held misconception that low-molecular-weight polyethylene glycols are "highly lipophilic" permeability probes and therefore are transported across lipid cell membranes. The relative lipophilicity of polyethylene glycols 400 and 600 were examined by determining their partition coefficients (Kd) in water and organic solvents of increasing relative polarity. The Kd of polyethylene glycol 414 between hexane and water was 0.000015, indicating that there are only 1.5 parts of polyethylene glycol 414 in hexane for 100,000 parts of polyethylene glycol 414 in water. When the Kd was determined in organic solvents with increasing relative polarity or "water character", there was a linear increase in Kd. The relative urinary recovery of individual molecular weight fractions of polyethylene glycol 400 in normal volunteers was analyzed. After oral ingestion, there was a progressive decrease in relative urinary recovery of increasing molecular weight fractions of polyethylene glycol 400 suggesting that increase in the molecular size limited polyethylene glycol intestinal permeability. There was excellent correlation between the relative urinary recovery and the hydrophilicity of the intravenously administered polyethylene glycol 400 fractions. It is concluded that polyethylene glycols 400 and 600 are strongly hydrophilic. Since partitioning of polyethylene glycol into lipid phase is negligible in lipid/water mixtures, they are unlikely to be transported via lipid pathways. The intestinal permeability of polyethylene glycols are governed by their molecular size, and once in circulation their urinary excretion appears to be governed in part by their plasma or water solubility.

Mechanisms of polyethylene glycol 400 permeability of perfused rat intestine

Abnormal permeability to polyethylene glycol 400 (PEG 400) has been demonstrated in various disorders with defective intestinal barrier functions. To understand the basic mechanisms of PEG 400 permeability, we compared PEG 400 permeation in different segments of the intestine and studied the kinetics and influence of intraluminal factors on PEG 400 absorption in vivo in perfused intestinal segments of the rat. The permeation rate of PEG 400 was dependent on the luminal concentration (y = 12.99x + 3.5; r = 0.97), indicating that passive movement is the mechanism involved in PEG 400 absorption. Changing the perfusate pH from 6 to 7.4 or modifying the unstirred water layer resistance by changing luminal flow rate did not affect PEG 400 absorption. When luminal osmolarity was varied from 0.225 to 0.6 osmol/L, higher osmolarity decreased both water and PEG 400 absorption (p greater than 0.01). The relationship between PEG 400 and water absorption at different osmolarities was linear (y = 0.9x + 5.7; r = 0.98). At a luminal osmolarity of 0.3 osmol/L 43% of PEG 400 permeation was mediated by passive diffusion and 57% was mediated by solvent drag. Increasing water absorption by decreasing luminal osmolarity resulted in proportional increase of PEG 400 permeation through solvent drag or convection. The solvent drag reflection coefficient (sigma f) for PEG 400 permeation of the jejunum was 0.1. Taurocholic acid (10 mM) alone or with oleic acid (2.5 mM) did not affect PEG 400 absorption. Permeabilities of 1 mM PEG 400 and water were similar in jejunum and ileum but were markedly increased in the colon (p greater than 0.01). These studies demonstrate that PEG 400 is absorbed by both passive diffusion and by solvent drag, with the latter accounting for a greater fraction of the absorptive drive under normal conditions. Polyethylene glycol 400 uses aqueous pathways for its permeation across the intestinal epithelium.