Biomedical subjects

Ren Yuan

Publications and source records attributed to Ren Yuan.

4 recordsLinked to original sources

PubMed2006

Computer-aided detection in screening CT for pulmonary nodules.

OBJECTIVE: Our objective was to evaluate the performance of a computer-aided detection (CAD) system for pulmonary nodule detection using low-dose screening CT images. MATERIALS AND METHODS: One hundred fifty consecutive low-dose screening CT examinations were independently evaluated by a radiologist and a CAD pulmonary nodule detection system (R2 Technology) designed to identify nodules larger than 4 mm in maximum long-axis diameter. All discrepancies between the two techniques were reviewed by one of another two radiologists working in consensus with the initial interpreting radiologist, and a "true" nodule count was determined. Detected nodules were classified by size, density, and location. The performance of the initial radiologist and the CAD system were compared. RESULTS: The radiologist detected 518 nodules and the CAD system, 934 nodules. Of the 1,106 separate nodules detected using the two techniques, 628 were classified as true nodules on consensus review. Of the true nodules present, the radiologist detected 518 (82%) of 628 nodules and the CAD, 456 (73%) of 628 nodules. All 518 radiologist-detected nodules were true nodules, and 456 (49%) of 934 of CAD-detected nodules were true nodules. The radiologist missed 110 true nodules that were only detected by CAD. In six patients, these were the only nodules detected in the examination, changing the imaging follow-up protocol. CAD identified 478 lesions that on consensus review were false-positive nodules, a rate of 3.19 (478/150) per patient. CONCLUSION: CAD detected 72.6% of true nodules and detected nodules in six (4%) patients not identified by radiologists, changing the imaging follow-up protocol of these subjects. In this study, the combined review of low-dose CT scans by both the radiologist and CAD was necessary to identify all nodules.

Diagnosis, Computer-Assisted↗

PubMed2005

Targeted overexpression of calcitonin in gonadotrophs of transgenic mice leads to chronic hypoprolactinemia.

It was previously shown that calcitonin-like pituitary peptide (pit-CT) is synthesized and secreted by gonadotrophs, and pit-CT inhibits PRL gene transcription and lactotroph cell proliferation. Present studies examined long-term consequences of pit-CT overexpression on the functioning of mouse anterior pituitary (AP) gland. Targeted overexpression of pit-CT in gonadotrophs of mouse pituitaries was achieved by generating mice overexpressing bovine luteinizing hormone (LH)-alpha subunit promoter-pit-CT cDNA transgene. Transgenic (pit-CT+) mice displayed chronic but selective overexpression of pit-CT in gonadotrophs. The mice also displayed a dramatic decline in PRL gene expression as assessed by PRL mRNA abundance, PRL immunohistochemistry (IHC) and serum PRL levels. LH secretion in pit-CT+ mice was also reduced, without any change in FSH secretion. Reproductive abnormalities such as prolonged estrous cycles, reduced pregnancy rate, delivery of smaller litters, increased neonatal mortality and deficient lactation were also observed. Administration of PRL during early pregnancy significantly increased the pregnancy rate and neonatal survival of newborns. These results demonstrate that overexpression of pit-CT leads to chronic hypoprolactinemia and reproductive dysfunction in female mice, and reinforces the possibility that gonadotroph-derived pit-CT is an important paracrine regulator of lactotroph function.

Animals↗

PubMed2004

Sonographic findings of active Clonorchis sinensis infection.

PURPOSE: The aim of this study was to document the characteristic sonographic findings of clonorchiasis for the diagnosis of active infection in an endemic area. METHODS: In a village in northeastern China, residents underwent fecal examinations for detection of Clonorchis sinensis eggs. Shortly thereafter, residents were examined with abdominal sonography. An experienced radiologist performed the sonographic examinations and analyzed the findings. Subjects whose fecal examinations were positive for eggs were considered to have active clonorchiasis; those whose examinations were negative for eggs were used as control subjects. The distinguishing sonographic features of active clonorchiasis were identified by stepwise logistic regression analysis. RESULTS: The study population comprised 457 subjects; fecal examinations revealed C. sinensis eggs in 316 and no eggs in 141. Four sonographic findings distinguished subjects with active clonorchiasis from control subjects: increased periductal echogenicity (p < 0.001; R = 0.11; sensitivity, 35%; specificity, 91%), floating echogenic foci in the gallbladder (p < 0.001; R = 0.09; sensitivity, 28%; specificity, 94%), diffuse dilatation of the intrahepatic bile ducts (p < 0.01; R = 0.03; sensitivity, 67%; specificity, 48%), and gallbladder distention (p < 0.05; R = 0.02; sensitivity, 3%; specificity, 100%), in decreasing order of significance. Among these 4 sonographic findings, increased periductal echogenicity and floating echogenic foci in the gallbladder were more significantly associated with active infection than were the other 2. CONCLUSIONS: Increased periductal echogenicity and floating echogenic foci in the gallbladder were identified as the 2 most significant findings for the sonographic diagnosis of active C. sinensis infection.

Adolescent↗

PubMed2003

Antiproliferative action of calcitonin on lactotrophs of the rat anterior pituitary gland: evidence for the involvement of transforming growth factor beta 1 in calcitonin action.

Calcitonin-like pituitary peptide, which is synthesized and secreted by gonadotrophs of the rat anterior pituitary (AP) gland, is a potent inhibitor of prolactin biosynthesis and lactotroph cell proliferation. Because TGF-beta 1 is an autocrine inhibitor of lactotroph cell proliferation, we investigated a possibility that calcitonin (CT) interacts with TGF-beta 1 to inhibit lactotroph cell proliferation. The actions of CT on GGH3 cell proliferation were examined in the absence or presence of anti-TGF-beta 1 serum. Subsequent experiments tested the effects of CT on TGF-beta 1 mRNA abundance as well as TGF-beta 1 synthesis. The studies also tested whether the stimulatory action of CT on TGF-beta 1 mRNA expression involves stabilization of TGF-beta 1 mRNA. Finally, the experiments investigated in vivo actions of CT on TGF-beta 1 synthesis in the AP gland. This was accomplished by studying the changes induced by i.v. administered CT in TGF-beta 1-immunopositive cell populations of adult female rat AP glands. The results have shown that the inhibitory action of CT on proliferation of GGH3 cells was attenuated by rabbit anti-TGF-beta 1 serum. Moreover, CT stimulated TGF-beta 1 mRNA expression, as well as TGF-beta 1 synthesis, in a dose-dependent fashion. Stimulatory action of CT on TGF-beta 1 expression may be posttranscriptional, because it significantly increased TGF-beta 1 mRNA stability. When administered in vivo, CT significantly increased TGF-beta 1-immunopositive cell populations of adult female rat AP gland. Colocalization studies for prolactin and TGF-beta 1 suggest that CT increased TGF-beta 1 synthesis in lactotrophs, and possibly in nonlactotroph cell populations. These results suggest that antiproliferative action of CT on lactotrophs may, at least in part, be mediated by CT-induced TGF-beta 1 expression.

Animals↗