Juvenile polyposis syndrome is a rare autosomal dominant syndrome characterized by multiple distinct juvenile polyps in the gastrointestinal tract and an increased risk of colorectal cancer.The cumulative life-time ri...Juvenile polyposis syndrome is a rare autosomal dominant syndrome characterized by multiple distinct juvenile polyps in the gastrointestinal tract and an increased risk of colorectal cancer.The cumulative life-time risk of colorectal cancer is 39% and the relative risk is 34.Juvenile polyps have a distinctive histology characterized by an abundance of edematous lamina propria with inflammatory cells and cystically dilated glands lined by cuboidal to columnar epithelium with reactive changes.Clinically,juvenile polyposis syndrome is defined by the presence of 5 or more juvenile polyps in the colorectum,juvenile polyps throughout the gastrointestinal tract or any number of juvenile polyps and a positive family history of juvenile polyposis.In about 50%-60% of patients diagnosed with juvenile polyposis syndrome a germline mutation in the SMAD4 or BMPR1A gene is found.Both genes play a role in the BMP/TGF-beta signalling pathway.It has been suggested that cancer in juvenile polyposis may develop through the socalled "landscaper mechanism" where an abnormal stromal environment leads to neoplastic transformation of the adjacent epithelium and in the end invasive carcinoma.Recognition of this rare disorder is important for patients and their families with regard to treatment,follow-up and screening of at risk individuals.Each clinician confronted with the diagnosis of a juvenile polyp should therefore consider the possibility of juvenile polyposis syndrome.In addition,juvenile polyposis syndrome provides a unique model to study colorectal cancer pathogenesis in general and gives insight in the molecular genetic basis of cancer.This review discusses clinical manifestations,genetics,pathogenesis and management of juvenile polyposis syndrome.展开更多
While the preferential movement of water inside carbon nanotube is appealing for water purification,our understanding of the water transport mechanism through carbon nanotube(CNT)-based membrane is far from adequate. ...While the preferential movement of water inside carbon nanotube is appealing for water purification,our understanding of the water transport mechanism through carbon nanotube(CNT)-based membrane is far from adequate. Here we conducted molecular dynamics simulations to study how the alignment of the CNTs in the membrane affects the water transport through the CNT membrane. It was shown that compared to the conventional CNT membrane where the alignment of CNTs was vertical to membrane surface, the ‘‘italicized CNT membrane'' in which the contact angel between membrane surface and the CNT alignment is not 90° offered a higher transmembrane flux of water. The expanded exposure of more carbon atoms to water molecules reduced the energy barrier near the entrance of this italicized CNT membrane, compared to the vertical one. For water flows through the italicized CNT membrane, the Lennard-Jones interaction between water and nanotube as function of central path of the CNT changes from ‘‘U'' to ‘‘V'' pattern, which significantly lowers energy barrier for filling water into the CNT,favoring the water transport inside carbon nanotube. Above simulation indicates new opportunities for applying CNT in water purification or related fields in which water transport matters.展开更多
文摘Juvenile polyposis syndrome is a rare autosomal dominant syndrome characterized by multiple distinct juvenile polyps in the gastrointestinal tract and an increased risk of colorectal cancer.The cumulative life-time risk of colorectal cancer is 39% and the relative risk is 34.Juvenile polyps have a distinctive histology characterized by an abundance of edematous lamina propria with inflammatory cells and cystically dilated glands lined by cuboidal to columnar epithelium with reactive changes.Clinically,juvenile polyposis syndrome is defined by the presence of 5 or more juvenile polyps in the colorectum,juvenile polyps throughout the gastrointestinal tract or any number of juvenile polyps and a positive family history of juvenile polyposis.In about 50%-60% of patients diagnosed with juvenile polyposis syndrome a germline mutation in the SMAD4 or BMPR1A gene is found.Both genes play a role in the BMP/TGF-beta signalling pathway.It has been suggested that cancer in juvenile polyposis may develop through the socalled "landscaper mechanism" where an abnormal stromal environment leads to neoplastic transformation of the adjacent epithelium and in the end invasive carcinoma.Recognition of this rare disorder is important for patients and their families with regard to treatment,follow-up and screening of at risk individuals.Each clinician confronted with the diagnosis of a juvenile polyp should therefore consider the possibility of juvenile polyposis syndrome.In addition,juvenile polyposis syndrome provides a unique model to study colorectal cancer pathogenesis in general and gives insight in the molecular genetic basis of cancer.This review discusses clinical manifestations,genetics,pathogenesis and management of juvenile polyposis syndrome.
基金supported by the National Natural Science Foundation of China(21476125)Tsinghua University Foundation(2013108930)State Key Laboratory of Chemical Engineering(SKL-CHE-10A01)
文摘While the preferential movement of water inside carbon nanotube is appealing for water purification,our understanding of the water transport mechanism through carbon nanotube(CNT)-based membrane is far from adequate. Here we conducted molecular dynamics simulations to study how the alignment of the CNTs in the membrane affects the water transport through the CNT membrane. It was shown that compared to the conventional CNT membrane where the alignment of CNTs was vertical to membrane surface, the ‘‘italicized CNT membrane'' in which the contact angel between membrane surface and the CNT alignment is not 90° offered a higher transmembrane flux of water. The expanded exposure of more carbon atoms to water molecules reduced the energy barrier near the entrance of this italicized CNT membrane, compared to the vertical one. For water flows through the italicized CNT membrane, the Lennard-Jones interaction between water and nanotube as function of central path of the CNT changes from ‘‘U'' to ‘‘V'' pattern, which significantly lowers energy barrier for filling water into the CNT,favoring the water transport inside carbon nanotube. Above simulation indicates new opportunities for applying CNT in water purification or related fields in which water transport matters.
