Relationship between clinical factors and severity of esophageal candidiasis according to Kodsi's classification.

Severe Candida esophagitis (CE) may lead to development of strictures, hemorrhage, esophagotracheal fistula, and a consequent decrease in quality of life. Although the severity of CE has been classified based on macroscopic findings on endoscopy, the clinical significance remains unknown. The aim of the study was to elucidate the predictive clinical factors for endoscopic severity of CE. Patients who underwent upper endoscopy and answered questionnaires were prospectively enrolled. Smoking, alcohol, human immunodeficiency virus (HIV) infection, diabetes mellitus, chronic renal failure, liver cirrhosis, systemic steroids use, proton pump inhibitor use, H2 blocker use, and gastrointestinal (GI) symptoms were assessed on the same day of endoscopy. GI symptoms including epigastric pain, heartburn, reflux, hunger cramps, nausea, dysphagia, and odynophagia were assessed on a 7-point Likert scale. Endoscopic severity was classified as mild (Kodsi's grade I/II) or severe (grade III/IV). Of 1855 patients, 71 (3.8%) were diagnosed with CE (mild, n = 48; severe, n = 23). In the CE patients, 50.0% (24/48) in the mild group and 23.1% (6/23) in the severe group did not have any GI symptoms. In HIV-infected patients (n = 17), a significant correlation was found between endoscopic severity and declining CD4 cell count (Spearman's rho = -0.90; P < 0.01). Multivariate analysis revealed that GI symptoms (odds ratio [OR], 3.32) and HIV infection (OR, 3.81) were independently associated with severe CE. Patients in the severe group experienced more epigastric pain (P = 0.02), reflux symptoms (P = 0.04), dysphagia (P = 0.05), and odynophagia (P < 0.01) than those in the mild group. Of the GI symptoms, odynophagia was independently associated with severe CE (OR 9.62, P = 0.02). In conclusion, the prevalence of CE in adults who underwent endoscopy was 3.8%. Silent CE was found in both mild and severe cases. Endoscopic severity was associated with characteristic GI symptoms and comorbidity of HIV infection. A decline in immune function correlated with CE disease progression.

Predictive value of endoscopic findings in the diagnosis of active intestinal amebiasis.

Endoscopic diagnosis of amebic colitis can be difficult because its appearance may mimic other forms of colonic disease. The aim of this study was to identify predictive endoscopic findings for amebic colitis. Patients with suspected amebic colitis based on distinctive endoscopic findings such as aphthae or erosions, ulcers, exudates, or a bump, were included in the study. A total of 157 patients were selected, 50 of whom had amebic colitis. The sensitivity and specificity of endoscopic findings that were significantly associated with amebic colitis were: cecal lesions (80% and 54%), multiple number of lesions (96% and 29%), presence of aphthae or erosions (84% and 37%), and presence of exudate (88% and 74%). Multivariate analysis revealed that the best combination of findings to predict amebic colitis was the presence of cecal lesions, multiple lesions, and exudates, which corresponded to an area under the receiver operating characteristic curve of 0.89 (95% confidence interval 0.82-0.95).

Recurrence of colonic diverticular bleeding and associated risk factors.

AIM: Colonic diverticular bleeding often recurs, but the risk factors remain unclear. Our aim was to identify risk factors for recurrence in patients with diverticular bleeding. METHOD: Seventy-two hospitalized patients who were diagnosed with diverticular bleeding between 2004 and 2008 were analyzed. Rebleeding was considered as the main outcome measure, with the duration until recurrence identified from medical records. Potential risk factors for rebleeding, such as underlying pathologies, medication and smoking and drinking habits, were investigated from the medical records on initial admission. RESULTS: Of the 72 patients, 19 had a diverticular disease on the right, 16 on the left side and 37 on both sides of the colon. Recurrence was identified in 27 (38%) patients at a median interval of 1535 days. The cumulative incidence of rebleeding at 6, 12 and 24 months was 15%, 20% and 33%. Multivariate analysis revealed nonsteroid anti-inflammatory drugs (NSAIDs) (hazard ratio (HR), 2.57; 95% confidence interval (CI), 0.89-7.46; P=0.08), antiplatelet drugs (HR, 2.39; 95% CI, 1.01-5.67; P=0.05) and hypertension (HR, 4.16; 95% CI, 1.22-14.2; P=0.02) to be risk factors for rebleeding. CONCLUSION: Patients with colonic diverticular bleeding show high recurrence rates within a short period. Risk factors for recurrence have been identified as the use of NSAIDs or antiplatelet drugs and hypertension.

Endoscopic ablation therapy of Barrett's esophagus.

Barrett's esophagus (BE) is an important risk factor for esophageal carcinoma and its incidence is rising. Amongst the various available endoscopic ablative therapies, radiofrequency ablation (RFA) is currently regarded as the most promising one, since RFA achieves high eradication rates of dysplasia and intestinal metaplasia with minimal complications. Patients with BE are advised to undergo regular endoscopic surveillance for dysplasia or cancer and endoscopy with four quadrant biopsy sampling at intervals of 1-2 cm of the entire length of BE remains the current standard for the detection of dysplasia or cancer. The management of BE depends on the histology of the biopsy specimens obtained during endoscopy, which includes non-dysplastic BE (ND-BE), low grade dysplasia, high grade dysplasia and adenocarcinoma. However, histological evaluation of dysplasia is fraught with error because of inter-observer variability even among expert gastrointestinal pathologists, and as a result, it often leads to false-negative or false-positive diagnoses. Non-dysplastic mucosa in BE shows clonal molecular aberrations, loss of cell cycle control, and other features of "neoplasia". These changes occur prior to morphologic expression of neoplasia (dysplasia). Given the difficulties of dysplasia assessment in mucosal biopsies, the molecular characteristics of ND-BE and LGD, and safe and effective profiles of RFA, this technique should be considered as a treatment option for the whole spectrum of BE patients.

Heat stress prevents the decrease in succinate dehydrogenase activity in the extensor digitorum longus of streptozotocin-induced diabetic rats.

This study aimed to investigate whether heat stress (HS) prevents a decrease in succinate dehydrogenase (SDH) activity and heat shock protein 60 (HSP60) and superoxide dismutase 2 (SOD2) contents in the extensor digitorum longus of streptozotocin (STZ)-induced diabetic rats. Twelve-week-old male Wistar rats were assigned to one of the four groups (n=6/group): control (Con), HS, diabetes mellitus (DM), and diabetes mellitus and heat stress (DM+HS). Diabetes was induced by the administration of STZ (50 mg/kg). HS was initiated 7 days after STZ treatment and performed at 42 °C for 30 min 5 times a week for 3 weeks. SDH activity was decreased in the DM and DM+HS groups. However, SDH activity was greater in the DM+HS group than in the DM group. Although HSP60 content was lower in the DM group than in the Con group, it was maintained in the DM+HS groups and was higher than that in the DM group. SOD2 content was decreased only in the DM group. These findings suggest that HS prevents the decrease in SDH activity in the skeletal muscle induced by DM. According to this mechanism, the maintenance of SOD2 and HSP60 by HS may suppress the increase in oxidative stress.

Current understandings of Helicobacter pylori, peptic ulcer and gastroesophageal reflux disease.

H. pylori infection is a major pathogen inducing gastric mucosal inflammation and causing dysregulation of normal acid inhibitory regulatory mechanisms. The overall effect on gastric acid secretion is dependent on the location and severity of inflammation. Eradication results in healing of gastric mucosal inflammation, healing of peptic ulcers, prevention of new peptic ulcers, prevention or reduction in gastric cancer risk and in transmission of the infection. Neither H. pylori infection nor H. pylori eradication causes gastroesophageal reflux disease (GERD). H. pylori eradication also does not impede anti-secretory drug therapy of GERD. Misunderstandings of the negative association between H. pylori infection and GERD and/or Barrett's esophagus and misuse of the epidemiologic concept of ''protection'' led to considerable confusion and likely resulted in some patients receiving poor care. Current evidence is consistent with the notion that H. pylori should be eliminated whenever the organism is found. However, H. pylori infection has become increasing difficult to cure in part due to the emergence of antimicrobial resistance. In Western countries, triple therapy consisting of a proton pump inhibitor, amoxicillin and clarithromycin no longer achieves adequate eradication rates and will soon need to be abandoned. When used, legacy triple therapy should be given for 14 days. Fluorquinolones may temporarily be useful: 10-14 day duration is superior to 7 days. However, worldwide resistance is rapidly increasing. Other potential replacement therapies and strategies are discussed including sequential therapies, high-dose proton pump inhibitor plus amoxicillin, and new quadruple therapies.

Effect of combination treatment with cyclophosphamide and nonspecific passive immunization on a transplantable tumor in WKA rats.

Combination of cyclophosphamide (CY) and passive immunization with lymphoid cells sensitized to allogeneic tumor was studied in the treatment of a methylcholanthrene-induced transplantable fibrosarcoma in WKA rats. For determination of the most effective timing of combination treatment, rats given an injection of CY on Day 3 received passive transfer of the sensitized lymphoid cells on Day 0, 1, 2, 3, 4, or 6. A remarkable therapeutic effect was observed only when the passive transfer was combined on Day 4 with CY on Day 3. Rats inoculated with tumor succumbed in all cases without any treatment. After i.v. injection of CY on Day 3, 2 of 28 rats were cured (7.1%). Passive immunization with the sensitized lymphoid cells on Day 4 resulted in no therapeutic effect. After combination of CY on Day 3 and transfer of nonsensitized normal lymphoid cells on Day 4, 2 of 15 rats survived (13.3%). However, combination of CY and passive transfer of the nonspecifically sensitized lymphoid cells resulted in 23 survivors of 29 rats (79.3%).

Effect of normal allogeneic lymphoid cell transfer in combination with chemotherapy on a transplantable tumor in rats.

In combination with chemotherapy [ftorafur (FT)], allogeneic lymphoid cells were transferred to inhibit the growth of a 3-methylcholanthrene-induced transplantable KMT-17 fibrosarcoma in Wistar-King-Aptekman/Hok rats. The transference of allogeneic lymphoid cells 4 days after tumor inoculation did not prove effective in inhibiting the growth of the tumor; administration of FT (300 mg/kg) on Day 3 resulted in a 16.7% survival rate. However, a combination of the transfer of cells and administration of FT resulted in an improved effect of 55.0%. A low dose of FT (100 mg/kg) also increased the therapeutic effect in combination with allogeneic lymphoid cell transfer (28.0%). However, a high dose of FT (500 mg/kg) did not increase the therapeutic effect (30.0%), even if combined with allogeneic lymphoid cell transfer on Day 2, 4, 6, or 9, although a high dose of FT administered alone on Day 4 showed a direct antitumor effect (32.0%). This effect was rather diminished when the transfer was combined on Day 2. (7.1%). The differences in the combination effect of doses of FT seem to depend on the immune status of the host induced by treatment with FT. In order to investigate the mechanism of combination timing of FT and allogeneic lymphoid cell transfer, the specific delayed hypersensitivity reaction to KMT-17 tumor was assayed by the radioisotopic footpad method. The specific delayed hypersensitivity reaction was strengthened by an injection of FT (300 mg/kg).

Immunochemotherapy of transplanted KMT-17 tumor in WKA rats by combination of cyclophosphamide and immunostimulatory protein-bound polysaccharide isolated from basidiomycetes.

Protein-bound polysaccharide Kureha (PS-K) isolated from Basidiomycetes was used in combination with cyclophosphamide (CY) for the treatment of a 3-methylcholanthrene- induced KMT-17 fibrosarcoma in WKA/Mk rats. A single administration of PS-K exhibited no inhibitory effect on the growth of s.c.-inoculated KMT-17 tumor at any timing and dose. However, PS-K exhibited a marked antitumor effect when it was combined with CY. The effect of PS-K dependend on the combination timing of PS-K and CY; a marked antitumor effect was observed when PS-K was administered before CY but not if it was given after CY or before tumor inoculation. When PS-K was administered on Day 1 followed by CY on Day 3, the highest survival rate of 78.5% (11 of 14) was obtained. Delayed hypersensitivity response of rats to KMT-17 was investigat ed by radioisotopic footpad assay. On Day 12, the hypersensitivity response in rats treated with PS-K on Day 1 and CY on Day 3 was significantly higher than that in nontreated rats, indicating an enhanced specific immunity to KMT-17 possibly resulting in a marked antitumor effect.

Localization of the violet and yellow receptor cells in the crayfish retinula.

Cellular identification of color receptors in crayfish compound eyes has been made by selective adaptation at 450 nm and 570 nm, wavelengths near the lambda(max)'s of the two retinular cell classes previously demonstrated. By utilizing earlier evidence, the concentration of lysosome-related bodies (LRB) was used to measure relative light adaptation and thus wavelength sensitivity in 665 retinular cells from six eyes. The observed particle distributions demonstrate the following. Both violet and yellow receptors occur ordinarily in each retinula. Of the seven regular retinular cells two (R(3) and R(4) using Eguchi's numbering [1965]) have mean sensitivities significantly greater to violet and less to yellow than the other five. The latter apparently comprise "pure" yellow receptors (R(1) and R(7)) and mixed yellow and violet receptors (R(2), R(5), and R(6)). Explanations of such ambiguity requiring two visual pigments in single retinular cells or intercellular coupling of adjacent neuroreceptors are apparently precluded by previous evidence. Present data imply alternatively some positional variability in the violet pair's location in individual retinulas. Thus R(3) and R(4) are predominantly the violet receptors but in some retinulas R(2) and R(3) or R(4) and R(5) (or rarely some other cell pairs) may be. The retinal distribution of such variations has yet to be determined. In agreement with intracellular recordings the blue and yellow cells here identified belong to both the vertical and horizontal e-vector sensitive channels.

Heat stress attenuates skeletal muscle atrophy of extensor digitorum longus in streptozotocin-induced diabetic rats.

To investigate whether heat stress attenuates skeletal muscle atrophy of the extensor digitorum longus (EDL) muscle in streptozotocin-induced diabetic rats, 12-week-old male Wistar rats were randomly assigned to four groups (n = 6 per group): control (Con), heat stress (HS), diabetes mellitus (DM), and diabetes mellitus/heat stress (DM + HS). Diabetes was induced by intraperitoneal injection of streptozotocin (50 mg/kg). Heat stress was induced in the HS and DM + HS groups by immersion of the lower half of the body in hot water at 42 °C for 30 min; it was initiated 7 days after injection of streptozotocin, and was performed once a day, five times a week for 3 weeks. The muscle fiber cross-sectional area of EDL muscles from diabetic and non-diabetic rats was determined; heat stress protein (HSP) 72 and HSP25 expression levels were also analyzed by western blotting. Diabetes-induced muscle fiber atrophy was attenuated upon heat stress treatment in diabetic rats. HSP72 and HSP25 expression was upregulated in the DM + HS group compared with the DM group. Our findings suggest that heat stress attenuates atrophy of the EDL muscle by upregulating HSP72 and HSP25 expression.

Natural history of bleeding risk in colonic diverticulosis patients: a long-term colonoscopy-based cohort study.

BACKGROUND: The natural history of bleeding risk from colonic diverticulosis remains unclear. AIM: To identify the incidence of bleeding in colonic diverticulosis patients and associated risk factors. METHODS: A cohort of 1514 patients with colonoscopy-confirmed asymptomatic diverticulosis was selected between 2001 and 2013. Age, sex and location of colonic diverticulosis (right or left side, or bilateral) were assessed. The endpoint was a bleeding event, and data were censored at the time of last colonoscopy. The cumulative and overall incidences of bleeding were estimated using the Kaplan-Meier and person-years methods. The Cox proportional hazards model was used to estimate age- and sex-adjusted hazard ratios (aHRs). RESULTS: The median follow-up period was 46 months. Bleeding events occurred in 35 patients, and the median time-to-event interval was 50 months. Kaplan-Meier analysis showed that the cumulative incidence of diverticular bleeding was 0.21% at 12 months, 2.2% at 60 months and 9.5% at 120 months. By the person-years method, the overall incidence rate of bleeding was 0.46 per 1000 patient-years. On multivariate analysis, age ≥70 (aHR. 3.7) and bilateral diverticulosis (aHR, 2.4) were significant risk factors for bleeding. CONCLUSIONS: This long-term follow-up study demonstrated that the cumulative incidence of bleeding from diverticulosis was approximately 2% at 5 years and 10% at 10 years, and the overall incidence was 0.46 per 1000 patient-years. Bilateral diverticulosis increased the risk of bleeding.

Diffuse Liver Metastasis of Small-Cell Lung Cancer Presenting as Acute Liver Failure and Diagnosed by Transjugular Liver Biopsy: A Rare Case in Whom Nodular Lesions Were Detected by Enhanced CT Examination.

Small-cell lung cancer (SCLC) is a subgroup of lung cancer with a high frequency of liver metastasis, which is a predictor of poor prognosis. Diffuse liver metastases of SCLC with no visible nodular lesions in the liver when examined using computed tomography (CT) are relatively rare; however, a few cases with rapid progression to acute liver failure that were diagnosed after death have been reported. In this paper, we report a 63-year-old man with diffuse liver metastases of SCLC that were histologically diagnosed using a transjugular liver biopsy while the patient was alive, even though no lesions were visible during a contrast-enhanced CT examination.

A novel control system for polymerase chain reaction using a RIKEN GS384 thermalcycler.

We have developed a novel high-throughput thermalcycler, the RIKEN GS384, which has a maximum of 1536 wells and whose temperature can be controlled accurately and simultaneously for a very small volume of a reaction mixture. In practice, the reaction is carried out using four 384-well (3.5 mm in diameter) plate formats which can be automatically moved using a robotic arm. To achieve accurate temperature control with high thermo-conductivity, we adopted Teflon-coated aluminum well plates closely sandwiched between silicon sheet-covered lids on top and a graphite sheet below. The lids were kept at a higher temperature (2 to 5 degrees C) than the reaction wells. The temperature of the 1536 sample wells was controlled accurately without temperature variability among the wells or evaporation, even for samples of very small volume (minimum 2 microliters). We also developed a new type of plate format which is similar to the 384-well place in terms of plate size, shape, and material, but which differs in the number (1536) and size (1.6 mm in diameter) of the wells. Since the amplification reactions could be done precisely as well, a total of 6144 reactions can potentially be carried out simultaneously using the GS384 thermalcycler. This is very promising for DNA microfabrication technology. This thermalcycler offers the advantage of high-throughput DNA analysis which should be useful for DNA diagnoses or for the human genome project.

Automated purification of synthetic oligonucleotides.

We have automated the trityl-on purification of oligonucleotides by use of an XYZ axis robotic solid-phase extraction system. This greatly decreased the preparation time required for oligonucleotide purification. After about 15 min for set up of the samples and instrument, the oligonucleotides are automatically purified with a 15-min run time per sample. Thus, for example, the purification of 15 oligonucleotides requires only about 15 min of preparation time and 4 h of machine time. Yields and purity are equivalent to manual methods.

Changes in enzyme activities in skin fibroblasts derived from persons of various ages.

We examined antioxidant enzyme activities (catalase, glutathione peroxidase, and superoxide dismutase) in cultured skin fibroblasts (passage number 2-3) derived from 30 persons of various ages. With increasing ages, catalase activity decreased, glutathione peroxidase activity increased slightly, and superoxide dismutase activity was unchanged. After UVA irradiation (4.8 joule/cm2) of the fibroblasts, only catalase activity decreased by 70%. This suggests that catalase may play an important role in the aging of human skin fibroblasts.

Mechanism of apoptosis in HL-60 cells induced by n-3 and n-6 polyunsaturated fatty acids.

The biochemical properties and specificity of n-3 and n-6 polyunsaturated fatty acids (PUFAs) are not well known. Because PUFAs induce apoptosis of different cells, we studied the effect of various PUFAs, such as arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosapentaenoic acid (DPA), on the fate of cultured human promyelocytic leukemia cells (HL-60) to elucidate the mechanism of apoptosis and the difference in action between n-3 and n-6 PUFAs. Fairly low concentrations of PUFAs inhibited the growth of HL-60 cells and induced their apoptosis by a mechanism that is sensitive to DMSO, an antioxidant, and z-Val-Ala-Asp(OMe)-fluoromethylketone (z-VAD-fmk), a pan-caspase inhibitor. PUFAs stimulated the generation of reactive oxygen species (ROS) and activated various types of caspase-like proteases, such as caspase-3, -6, -8, and -9, but not caspase-1. In addition, PUFAs triggered the reaction leading to the cleavage of Bid, a death agonist member of the Bcl-2 family, and also released cytochrome c from mitochondria into the cytosol. PUFAs also decreased the mitochondrial membrane potential of intact HL-60 cells. All of these actions of n-3 PUFAs were stronger than those of AA, an n-6 PUFA, although the mechanism is not known. PUFAs stimulate swelling and membrane depolarization of isolated mitochondria in a cyclosporin A-sensitive manner. The results indicated that PUFA-induced apoptosis of HL-60 cells may be caused, in part, by direct action on the cells and by activation of the caspase cascade through cytochrome c release coupled with mitochondrial membrane depolarization.

Mechanism of dibucaine-induced apoptosis in promyelocytic leukemia cells (HL-60).

Dibucaine, a local anesthetic, inhibited the growth of promyelocytic leukemia cells (HL-60) without inducing arrest of the cell cycle and differentiation to granulocytes. Typical DNA fragmentation and DNA ladder formation were induced in a concentration- and time-dependent manner. The half-maximal concentration of dibucaine required to induce apoptosis was 100 microM. These effects were prevented completely by the pan-caspase inhibitor z-Val-Ala-Asp-(OMe)-fluoromethylketone (z-VAD-fmk), thereby implicating the cysteine aspartase (caspase) cascade in the process. Dibucaine activated various caspases, such as caspase-3, -6, -8, and -9 (-like) activities, but not caspase-1 (-like) activity, and induced mitochondrial membrane depolarization and the release of cytochrome c (Cyt.c) from mitochondria into the cytosol. Processing of pro-caspase-3, -8, and -9 by dibucaine was confirmed by western blot analysis. Bid, a death agonist member of the Bcl-2 family, was processed by caspases following exposure of cells to dibucaine. However, 100 microM dibucaine scarcely inhibited oxidative phosphorylation, but it induced membrane permeability transition in isolated rat liver mitochondria. Taken together, these data suggest that dibucaine induced apoptosis of HL-60 cells through activation of the caspase cascade in conjunction with Cyt.c release induced by a processed product of Bid and depolarization of the mitochondrial membrane potential.

Selective inhibition of formyl-methionyl-leucyl-phenylalanine (fMLF)-dependent superoxide generation in neutrophils by pravastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase.

It has been shown previously that inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, such as compactin, lovastatin, and pravastatin, block cholesterol synthesis, suppress lymphocyte functions, and beneficially affect atherogenesis. Recently, it was reported that compactin and lovastatin inhibit the respiratory burst of DMSO-differentiated HL-60 cells, an effect reversed by mevalonic acid. The mode of action of these inhibitors in this role is not understood fully. Thus, we studied the mechanism of inhibition of neutrophil superoxide (O2*-) generation by pravastatin and found that pravastatin at 0.5 mM inhibited the receptor-mediated tyrosine kinase (TK)-dependent pathway of O2*- generation and also luminol chemiluminescence but not the protein kinase C (PKC)-dependent or the TK- and PKC-independent pathways of O2*- generation in neutrophils. Pravastatin also inhibited the tumor necrosis factor-alpha- and formyl-methionyl-leucyl-phenylalanine-induced phosphorylation of a tyrosine of a 115-kDa protein. These effects were not reversed by mevalonate. From these results it is concluded that pravastatin inhibited receptor-mediated O2*-generation by decreasing tyrosine phosphorylation but not by inhibiting the formation of an intermediate in the biosynthesis of cholesterol.

Immunohistochemical demonstration of epidermal growth factor (EGF) receptors in normal human placental villi.

With an avidin-biotin-peroxidase (or glucose oxidase) complex method using anti-epidermal growth factor receptor monoclonal antibody (528 IgG), the tissue and cellular distribution of the receptors for epidermal growth factors (EGF) in normal human placental villi, from 6 to 42 weeks of gestation, were studied. EGF receptors were mainly localized on the free surface of the syncytiotrophoblast that directly faced to intervillous space of the maternal circulation. The cell surface of cytotrophoblasts, except for the region that was adjacent to the basal lamina, was also positive for EGF receptors. The receptors were in close contact to the fetal vessels in the villous stroma. The EGF receptors on the syncytiotrophoblast were thought to be involved in the production and secretion of human chorionic gonadotropin and placental lactogen, probably under the control of maternal EGF. The receptors on cytotrophoblasts may play a role in trophoblastic proliferation, possibly mediated by EGF in the fetal circulatory system.