Novel porous aortic elastin and collagen scaffolds for tissue engineering

Decellularized vascular matrices are used as scaffolds in cardiovascular tissue engineering because they retain their natural biological composition and three-dimensional (3-D) architecture suitable for cell adhesion and proliferation. However, cell infiltration and subsequent repopulation of these scaffolds was shown to be unsatisfactory due to their dense collagen and elastic fiber networks. In an attempt to create more porous structures for cell repopulation, we selectively removed matrix components from decellularized porcine aorta to obtain two types of scaffolds, namely elastin and collagen scaffolds. Histology and scanning electron microscopy examination of the two scaffolds revealed a well-oriented porous decellularized structure that maintained natural architecture of the aorta. Quantitative DNA analysis confirmed that both scaffolds were completely decellularized. Stress-strain analysis demonstrated adequate mechanical properties for both elastin and collagen scaffolds. In vitro enzyme digestion of the scaffolds suggested that they were highly biodegradable. Furthermore, the biodegradability of collagen scaffolds could be controlled by crosslinking with carbodiimides. Cell culture studies showed that fibroblasts adhered to and proliferated on the scaffold surfaces with excellent cell viability. Fibroblasts infiltrated about 120 microm into elastin scaffolds and about 40 microm into collagen scaffolds after 4 weeks of rotary cell culture. These results indicated that our novel aortic elastin and collagen matrices have the potential to serve as scaffolds for cardiovascular tissue engineering.     

乳腺管状小叶癌

乳腺管状小叶癌（Tubulolobular carcinoma，TLC）最初是被作为小叶癌的管状变型。作者总结了27例TLC的组织学、免疫表型和临床特征，并与纯小管癌和经典型小叶癌进行了比较。此组患者年龄43-79岁（中位年龄60岁）。1例双侧乳腺受累，5例病变为多灶性。肿瘤直径0．5-2．5cm，色灰褐，质硬。组织学观察：TLC的肿瘤细胞形成管状和条索状两种结构模式并相互混杂，且两者比例相当（统称为管状小叶模式）。     

Germline mutations of the CDKN2 gene in UK melanoma families

Germline mutations in CDKN2 on chromosome 9p21, which codes for the cyclin D kinase inhibitor p16, and more rarely, mutations in the gene coding for CDK4, the protein to which p16 binds, underlie susceptibility in some melanoma families. We have sequenced all exons of CDKN2 and analysed the CDK4 gene for mutations in 27 UK families showing evidence of predisposition to melanoma. Five different germline mutations in CDKN2 were found in six families. Three of the mutations (Met53Ile, Arg24Pro and 23ins24) have been reported previously. We have identified two novel CDKN2 mutations (88delG and Ala118Thr) which are likely to be associated with the development of melanoma, because of their co-segregation with the disease and their likely functional effect on the CDKN2 protein. In binding assays the protein expressed from the previously described mutation, Met53Ile, did not bind to CDK4/CDK6, confirming its role as a causal mutation in the development of melanoma. Ala118Thr appeared to be functional in this assay. Arg24Pro appeared to bind to CDK6, but not to CDK4. No mutations were detected in exon 2 of CDK4, suggesting that causal mutations in this gene are uncommon. The penetrance of these mutant CDKN2 genes is not yet established, nor is the risk of non-melanoma cancer to gene carriers.      

Solution properties of ultrahigh-molecular-weight polymers, 16. Unperturbed dimensions of poly(isobutyl methacrylate)

Three techniques, i. e., the Lenka extrapolation method, the Stockmayer-Fixman method, and the extrapolation of the Mark-Houwink constants to a = 0,5 were applied to determine the unperturbed dimensions of ultrahigh-molecular-weight poly(isobutyl methacrylate). A correction term, depending on the exponent a of the Mark-Houwink relation, is suggested to be introduced into the Stockmayer-Fixman-Burchard equation.     

The cerebral microvasculature of the rat: structure and luminal surface properties during early development

The development of the cerebral microvasculature of the rat was studied during three successive postnatal periods, namely: 1) neonatal period, i.e., 1 to 9 days after birth (capillary sprouting period); 2) myelinization period, i.e., 10 to 20 days; and 3) young adult period, i.e., 2 to 3 months. The survey covered structural aspects and distribution of binding sites for anionic or cationic probes and for albumin-gold complexes on the luminal surface of the microvascular endothelium. The salient results are: a) an extensive development of the endoplasmic reticulum of endothelial cells during the first period (presumably in relation with the production of basement membrane components); b) the high surface density of coated pits and coated vesicles that peaks during the myelinization period; c) the paucity of plasmalemmal vesicle and their differential distribution (their volume density is higher in the endothelium of arterioles than in that of capillaries and venules); d) the existence of an extensive smooth surface tubular system in the cytoplasm of endothelial cells, whose structural connections and functional significance remains to be established; and e) the presence of pericytes with elaborate interactions with endothelia in the early developmental periods. Labeling by perfused tracers indicates an uneven patchy distribution of binding sites for cationic ferritin (generally limited to the plasmalemma proper) and a more even distribution of binding sites for cationic and anionic hemeundecapeptides. Binding patterns did not change during the developmental periods studied. No binding sites were detected for albumin-gold complexes.     

Changes in the organization of membrane lipids during human platelet activation. Study by fluorescent and freeze-fracture cytochemistry

Modifications in the membrane lipid organization of human platelets activated with different agents (adenosine 5'-diphosphate, thrombin, collagen type I, and monosaccharides such as fucose, mannose, and galactose) were analyzed in vitro by using three lipid markers. Cholesterol was detected upon interaction with filipin, the anionic phospholipids were reacted with polymyxin B, and alterations in the degree of lipid packing were evaluated with the lipophilic fluorescent probe merocyanine 540, which reportedly inserts into bilayer domains whose lipids are more disordered. Filipin-sterol complexes and polymyxin B-anionic phospholipid complexes form characteristic membrane deformations which were examined in freeze-fracture preparations, whereas the merocyanine 540 binding to platelet membrane was recorded by fluorescent microscopy. In contrast to the resting cells, thrombin-stimulated platelets displayed an uneven distribution of filipin-sterol complexes which occurred in much higher density on the cell body than on pseudopods: on the latter, apparently cholesterol-free domains were very common. Unlike the non-stimulated cells, the platelets aggregated with the various agents employed showed characteristic polymixin B-anionic phospholipid complexes deformations of plasmalemma suggesting the appearance in uneven concentration of anionic phospholipids in the outer membrane leaflet. Incubation with merocyanine 540 did not result in staining of resting platelets when these were maintained in plasma, but a slight fluorescence was observed when platelets were kept in Tyrode buffer. However, platelets stimulated with thrombin, collagen type I, and monosaccharides bound very heavily the fluorescent dye; platelets aggregated with adenosine-5'-diphosphate bound only small amounts of merocyanine 540. The results showed that, during activation by different agents, modifications in lipid membrane organization include alterations in cholesterol and anionic phospholipid distribution, transbilayer movement of anionic phospholipids accompanied by more disordered membrane.