Fibrils in marsupial enamel tubules

Summary Serial etching of cross-sectioned prisms in undecalcified adult marsupial enamel from different species, revealed distinct cylindrical acid-resistant fibrils that were demonstrable by light microscopy and by scanning electron microscopy. No fibrils were found in the enamel of Vombatus.The fibrils and the organic matrix in the remainder of the enamel stain differently. The fibrils project from the center of prisms or the borderline between prisms and interprismatic substance.It is concluded that the fibrils are chemically different from the organic matrix in the enamel, that they constitute the compact, homogenous, and morphologically well defined organic contents of the tubules in adult marsupial enamel.Since most of the material was obtained from dry museum crania, it is concluded that the fibrils are not destroyed by prolonged drying.The scanning electron micrographs were taken at the Electron Microscopical Unit for Biological Sciences, Oslo, Norway.     

Muscles advance the teeth in sand dollars and other sea urchins

We demonstrate the action of the dental promoter muscles in advancing the continuously growing teeth of sand dollars and sea urchins. Teeth wear at the occlusal end, while new calcite is added to the opposite end. Dental ligaments rigidly hold teeth during chewing, but soften and reform during advancement. The source of forces that advance the teeth was unknown until our discovery of the dental promoter muscles. The muscles, which underly the tooth, attach centrally to the stereom of the pyramid of the Aristotle''s lantern (jaw) and peripherally to a membrane that covers the distal end of the tooth. The muscles shorten along an axis nearly parallel to the long axis of the tooth. We stimulated contraction by addition of acetylcholine, with increasing concentrations of acetylcholine generating higher forces. Forces exerted by this muscle are appropriate for its size and are 1000 times lower than forces exerted by interpyramidal muscles that generate chewing forces. In sand dollars, a single muscle contraction of the dental promoter muscle can account for half the mean daily advancement of the teeth.     

纤维桩树脂核用于老年残根残冠修复的效果及对生活质量的影响

目的:探讨老年残根残冠应用纤维桩树脂核修复的临床效果及对病人生活质量的影响。方法:抽选我院行纤维桩树脂核修复的79例(86颗)老年残根残冠患者,对其进行3年随访,观察总体及不同牙位修复成功率和修复前、后生活质量的变化。结果:修复后进行3年随访,86颗残根残冠修复总成功率为95.3%,不同牙位修复成功率无显著差异(P0.05),均在94%以上,86颗牙失败4颗(其中2颗并发牙周炎、2颗牙纤维桩脱落,均未出现牙桩折断);修复后患者生活质量总分及各维度评分均明显优于修复前(P0.05)。结论:纤维桩树脂核是一种极为理想的残冠残根修复材料,能显著提高老年患者术后的生活质量,值得临床推广。     

靶控输注静脉麻醉和腰硬联合麻醉对直肠癌根治术患者免疫功能的影响研究

目的：探讨靶控输注静脉麻醉和腰硬联合麻醉对直肠癌根治术患者免疫功能的影响。方法：选择在我院行直肠癌根治术的72例患者,将其分为观察组和对照组各36例,其中观察组给予靶控输注静脉麻醉,对照组采用腰硬联合麻醉,对两组患者手术时间、术中出血量以及免疫球蛋白水平（IgG、IgA、IgM）、血清白介素-6水平（IL-6）、肿瘤坏死因子α水平（TNF-α）以及T细胞亚群（CD3、CD4）水平进行对比。结果：观察组手术平均时间为（130．5±11．7）min,术中平均出血量为（271.3±37．8）ml,与对照组比较差异均无统计学意义（P〉0．05）;两组IgG、IgA及IgM,在T1、T2、T3及T4时刻水平比较差异均无统计学意义（P〉0．05）;两组IL-6、TNF-α、CD3及CD4在麻醉后较T1时均有明显变化,比较差异均有统计学意义（P〈0．05）,且观察组变化较对照组更为明显,两组比较差异有统计学意义（P〈0．05）。结论：靶控输注静脉麻醉和腰硬联合麻醉对直肠癌根治术患者免疫功能均存在抑制作用,且以抑制细胞免疫功能为主,而腰硬联合麻醉抑制作用较低,值得推广应用。     

内镜下黏膜切除术治疗大肠息肉的临床疗效及术后出血的影响因素分析

摘要 目的：研究内镜下黏膜切除术（EMR）治疗大肠息肉的临床疗效及术后出血的影响因素。方法：将我院从2016年1月～2019年12月收治的大肠息肉患者500例纳入研究,所有患者均接受EMR治疗。分析其临床疗效以及术后出血发生情况,并对术后出血的影响因素实施单因素、多因素Logistic回归分析。结果：500例患者临床治疗总有效率为97.80%（489/500）,术后出血发生例数为17例,出血发生率为3.40%（17/500）。治疗后患者各项生活质量评分均高于治疗前（均P<0.05）。经单因素分析发现：大肠息肉患者经EMR治疗后其切除息肉数、术后进食时间、息肉外观、息肉分叶均与术后出血有关（均P<0.05）;而年龄、性别、息肉部位以及病理类型均与术后出血无关（均P>0.05）。经多因素Logistic回归分析可得：切除息肉数≥4枚、术后48 h内进食、息肉外观潮红/糜烂以及息肉分叶均是大肠息肉患者经EMR治疗后出血的危险因素（均P<0.05）。结论：EMR治疗大肠息肉患者的临床疗效较佳,可改善其生活质量,其中切除息肉数、术后进食时间、息肉外观以及息肉分叶均和术后出血有关,值得临床关注。     

Focus: 50 Years of DNA Repair: The Yale Symposium Reports: Investigations of Homologous Recombination Pathways and Their Regulation

The DNA double-strand break (DSB), arising from exposure to ionizing radiation or various chemotherapeutic agents or from replication fork collapse, is among the most dangerous of chromosomal lesions. DSBs are highly cytotoxic and can lead to translocations, deletions, duplications, or mutations if mishandled. DSBs are eliminated by either homologous recombination (HR), which uses a homologous template to guide accurate repair, or by nonhomologous end joining (NHEJ), which simply rejoins the two broken ends after damaged nucleotides have been removed. HR generates error-free repair products and is also required for generating chromosome arm crossovers between homologous chromosomes in meiotic cells. The HR reaction includes several distinct steps: resection of DNA ends, homologous DNA pairing, DNA synthesis, and processing of HR intermediates. Each occurs in a highly regulated fashion utilizing multiple protein factors. These steps are being elucidated using a combination of genetic tools, cell-based assays, and in vitro reconstitution with highly purified HR proteins. In this review, we summarize contributions from our laboratory at Yale University in understanding HR mechanisms in eukaryotic cells.     

New dental remains of Anoiapithecus and the first appearance datum of hominoids in the Iberian Peninsula

New dental remains of the fossil great ape Anoiapithecus brevirostris are described from the Middle Miocene local stratigraphic series of Abocador de Can Mata (ACM) in els Hostalets de Pierola (Vallès-Penedès Basin, NE Iberian Peninsula). These specimens correspond to maxillary fragments with upper teeth from two female individuals from two different localities: left P³–M¹ (IPS41712) from ACM/C3-Aj (type locality; 11.9 Ma [millions of years ago]); and right M¹–M² and left P⁴–M² (IPS35027) from ACM/C1-E* (12.3–12.2 Ma). Relative enamel thickness is also computed in the latter individual and re-evaluated in other Middle Miocene hominoids from ACM, in order to better assess their taxonomic affinities. With regard to maxillary sinus development, occlusal morphology, molar proportions and enamel thickness, the new specimens show greater resemblances with the (male) holotype specimen of A. brevirostris. They differ from Pierolapithecus catalaunicus in displaying less inflated crests, a more lingually-located hypocone, and relatively lower-crowned molars; from Dryopithecus fontani, in the relatively thicker enamel and lower-crowned molars; from Hispanopithecus spp., in the more inflated crown bases, less peripheral cusps and more restricted maxillary sinus; and from Hispanopithecus laietanus also in the thicker crests, more restricted occlusal foveae, and relatively lower-crowned molars. The new specimens of A. brevirostris show some slight differences compared with the holotype of this species: smaller size (presumably due to sexual size dimorphism), and less distally-tapering M² occlusal contour (which is highly variable in both extant and extinct hominoids). The reported remains provide valuable new evidence on dental intraspecific variation and sexual dimorphism in Anoiapithecus. From a taxonomic viewpoint, they support the distinction of this taxon from both Dryopithecus and Pierolapithecus. From a chronostratigraphic perspective, IPS35027 from ACM/C1-E* enlarges the known temporal distribution of Anoiapithecus, further representing the oldest record (first appearance datum) of hominoids in the Iberian Peninsula.     

Effects of cryopreservation with a newly-developed magnetic field programmed freezer on periodontal ligament cells and pulp tissues

The purpose of this study was to evaluate the effects of long-term cryopreservation on the isolated human periodontal ligament cells (PDL) and pulp tissues. In the first part of study, 10 freshly extracted teeth were selected and divided into two groups. In the cryopreserved group, the teeth were frozen for 5 years using a programmed freezer combined with a magnetic field, known as Cells Alive System “CAS”. As for the control group, freshly extracted teeth were used. In each group, extracted PDL tissues were cultured and gene expression and protein concentration of collagen type I, alkaline-phosphatase (ALP) and vascular endothelial growth factor (VEGF) was compared between the two groups. In the second part, pulp tissues were obtained from 10 mature and immature third molars which were freshly extracted or cryopreserved for three months. Expression of VEGF and nerve growth factor (NGF) mRNAs and the protein concentration in the supernatant were investigated. Results indicated that long-term cryopreservation with the use of CAS freezer cannot affect the growth rate and characteristics of PDL cells. There was no significant difference in VEGF expression and VEGF and NGF protein concentration of pulp cells derived from cryopreserved teeth with immature apex and control group with mature root formation. Finally, proper PDL regeneration and appropriate apexogenesis after transplanting magnetically cryopreserved immature tooth was clinically confirmed. These findings demonstrate that teeth banking with the use of magnetic field programmed freezer can be available for future autotransplantation as a treatment modality for replacing missing teeth.     

VEGF levels and the angiogenic potential of the microenvironment can affect surgical strategy for colorectal liver metastasis

The hypotheses emerging from basic research on colorectal liver metastases must be tested in clinical situations for the adaptation of current treatment strategies. Pre-metastatic niches have been shown to exist in human colorectal synchronous metastases, with the liver parenchyma adjacent to the synchronous liver metastases providing a favorable, angiogenic environment for metastatic tumor growth. The role of the VEGF signaling pathway in liver regeneration and tumor growth remains unclear, but the use of antiangiogenic agents in combination with surgical treatment is almost certainly beneficial.