Calcification of the permanent first mandibular molar in rhesus monkeys

Evidence suggests that in rhesus monkeys calcification in the mandibular permanent first molar commences much earlier than has been previously reported. This tooth is the first secondary dental element to calcify, as it is in man.     

不同石灰化程度板栗中淀粉代谢及蔗糖含量变化

【目的】研究不同石灰化程度板栗中淀粉代谢及蔗糖含量的变化,探讨板栗石灰化发生与上述指标变化的关系,为进一步揭示板栗石灰化发生机理提供依据。【方法】以新鲜板栗为试材,进行常温贮藏,相对湿度60%—70%。贮藏一定时间后,将板栗石灰化程度分成5个等级0、30%、60%、90%、100%,测定不同石灰化程度板栗中水分含量、淀粉酶活性、淀粉含量和蔗糖含量的变化。【结果】随着板栗石灰化程度的加深,板栗的水分含量和淀粉逐渐减少,表现为明显的负相关关系,相关系数分别为r＝-0.946和r＝-0.950;而α-淀粉酶和β-淀粉酶活性均随着板栗石灰化程度的加深呈先升后降的趋势,蔗糖含量则逐渐增加。【结论】板栗石灰化发生与板栗失水诱导淀粉酶活性增强、导致淀粉不断分解致使含量减少、引起淀粉晶体结构及理化性能发生改变密切相关,与蔗糖含量无关。     

Corneal calcification

Superficial calcification was produced in the normal rabbit cornea by mild irradiation with a carbon dioxide laser. The calcification was entirely extracellular and closely resemnbled that observed in human band keratopathy, which was characterized as hydroxyapatite by x-ray diffraction. The electron-mnicroscopic appearance of calcific spheriules and conglomerates in early cornteal calcification is presented. The calcific spherules arise at the basal plasma membrane surface of the epithelial cells in close relation to their basement membrane.     

Growth of Western Australian corals in the anthropocene

Anthropogenic increases of atmospheric carbon dioxide lead to warmer sea surface temperatures and altered ocean chemistry. Experimental evidence suggests that coral calcification decreases as aragonite saturation drops but increases as temperatures rise toward thresholds optimal for coral growth. In situ studies have documented alarming recent declines in calcification rates on several tropical coral reef ecosystems. We show there is no widespread pattern of consistent decline in calcification rates of massive Porites during the 20th century on reefs spanning an 11° latitudinal range in the southeast Indian Ocean off Western Australia. Increasing calcification rates on the high-latitude reefs contrast with the downward trajectory reported for corals on Australia's Great Barrier Reef and provide additional evidence that recent changes in coral calcification are responses to temperature rather than ocean acidification.     

茶多酚对板栗“石灰化”及活性氧代谢的影响

 【目的】探讨抗氧化剂茶多酚对板栗“石灰化”及活性氧代谢的影响。【方法】以新鲜板栗为试材,经2%、4% 、6%茶多酚溶液处理后进行常温贮藏,测定贮藏过程中“石灰化”指数、超氧阴离子( )产生速率、过氧化氢(H2O2)含量、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性的变化以及膜脂过氧化产物(丙二醛,MDA)含量的变化。【结果】经2%茶多酚溶液处理的板栗“石灰化”指数受到显著抑制。进一步研究表明,2%茶多酚溶液处理能使板栗的SOD和CAT活性高于对照,而 产生速率和H2O2积累量低于对照,减少MDA积累,从而抑制板栗过氧化作用。【结论】适宜浓度的茶多酚处理可降低板栗贮藏过程中的活性氧产生,抑制“石灰化”发生。     

Ⅱ型糖尿病骨质疏松与血管钙化的相关性分析

目的分析Ⅱ型糖尿病患者骨质疏松和骨量减少与血管钙化之间的关联性,为早期诊断和预防糖尿病性骨质疏松提供依据．方法按入选标准对59例Ⅱ型糖尿病患者记录临床体征、血液实验室检查结果．采用双能x线吸收法测定腰椎和股骨颈骨密度值,x线摄片记录胸主动脉和髂动脉的血管钙化情况,并对各因素与糖尿病性骨质疏松相关性进行分析．结果腰椎骨量分析可见：骨质疏松6例（10．2％）,骨量减少27例（45．8％）;股骨颈骨量分析可见：骨质疏松7例（11．8％）,骨量减少28例（49％）．髂动脉钙化与腰椎（L1—L4）骨质疏松（P=0．04）和股骨颈骨质疏松（P=0．036）存在显著相关性．结论Ⅱ型糖尿病患者髂动脉钙化与骨质疏松呈正相关,发现动脉钙化可能提示骨质疏松或骨量减少的存在．     

Silicon: a possible factor in bone calcification

Silicon, a relatively unknown trace element in nutritional research, has been uniquely localized in active calcification sites in young bone. Silicon increases directly with calcium at relatively low calcium concentrations and falls below the detection limit at compositions approaching hydroxyapatite. It is suggested that silicon is associated with calcium in an early stage of calcification.     

Calcification on an Unstable Substrate: Marginal Growth in the Moilusk Pecten diegensis

Observations of the growing margin of Pecten diegensis show that calcification can occur on an unstable substrate, although this initial shell material is quite disordered. Later growth on the inner surface of the disordered material soon becomes ordered, which suggests that the calcification process benefits from the stability of a mineralized substrate, but does not utilize the substrate as a physical or stereochemical template.     

Modern cyanobacterial analogs of paleozoic stromatoporoids

Recent and subfossil calcareous structures resembling cystose and subclathrate Paleozoic stromatoporoids have been discovered in a sea-linked, stratified, alkaline crater lake on Satonda Island, Indonesia. The structures are produced by mats of coccoid cyanobacteria growing along the lakeshore from the water surface down to the O(2)-H(2)S interface located at a depth of 22.8 meters. Calcification of the mats is controlled by seasonal changes in calcium carbonate supersaturation in the epilimnion. The internally complex structures are a product of two different calcification processes: (i) periodic in vivo calcification of the surficial cyanobacterial layers by low-Mg calcite, and (ii) early postmortem calcification of the cyanobacterial aggregates below the mat surface by microbially precipitated aragonite. The finding supports the idea that Paleozoic stromatoporoids represent fossilized cyanobacteria (stromatolites). It also implies that the stromatoporoid-generating epicontinental seas during the early Paleozoic may have been more alkaline and had a higher carbonate mineral supersaturation than modern seawater.     

Inhibition of calcification of bioprosthetic heart valves by local controlled-release diphosphonate

Bioprostheses fabricated from porcine aortic valves are widely used to replace diseased heart valves. Calcification is the principal cause of the clinical failure of these devices. In the present study, inhibition of the calcification of bioprosthetic heart valve cusps implanted subcutaneously in rats was achieved through the adjacent implantation of controlled-release matrices containing the anticalcification agent ethanehydroxydiphosphonate dispersed in a copolymer of ethylene-vinyl acetate. Prevention of calcification was virtually complete, without the adverse effects of retarded bone and somatic growth that accompany systemic administration of ethanehydroxydiphosphonate.     

Foraminiferal calcification response to glacial-interglacial changes in atmospheric CO2

A record of foraminiferal shell weight across glacial-interglacial Termination I shows a response related to seawater carbonate ion concentration and allows reconstruction of a record of carbon dioxide in surface seawater that matches the atmospheric record. The results support suggestions that higher atmospheric carbon dioxide directly affects marine calcification, an effect that may be of global importance to past and future changes in atmospheric CO2. The process provides negative feedback to the influence of marine calcification on atmospheric carbon dioxide and is of practical importance to the application of paleoceanographic proxies.     

Drug-induced teratogenesis in vitro: inhibition of calcification by different tetracyclines

Inhibition of calcification in embryonic bone rudiments was studied in the presence of several tetracyclines at three different concentrations. Different criteria for calcification and different concentrations of tetracyclines yielded parallel results and showed significant differences in the inhibitory action of the various compounds. The clear-cut results indicate that the test-system that was developed may be useful for the comparison of various teratogens under simplified controllable conditions.     

Aragonite Crystals within Codiacean Algae: Distinctive Morphology and Sedimentary Implications

Morphologic studies of single crystals of aragonite within Codiacean algae reveal characteristic crystal forms produced by two distinctly different modes of calcification. Diagnostic serrated crystals (1 micrometer in length) of aragonite originating within the extracellular sheaths of capitular filaments are incorporated into modern lime sediments and may serve as effective tracers for particles of algal origin. Intracellular calcification within Penicillus dumetosus, previously unueported, is represented by doubly terminated aragonite crystals ranging in size from 48 to 160 micrometers.     

BIOTIN DEFICIENCY AND OTHER CHANGES IN RATS GIVEN SULFANILYLGUANIDINE OR SUCCINYL SULFATHIAZOLE IN PURIFIED DIETS

The following pathological changes have been observed in rats given sulfaguanidine or sulfasuxidine in purified diets. 1. A granulocytopenia, leukopenia, hypocellularity of bone marrow and, occasionally, an anemia. 2. Hyalinization, necrosis and calcification of voluntary muscle. 3. Hyaline sclerosis and calcification of blood vessels. 4. A dermatitis which can be prevented or successfully treated with crystalline biotin. We have also observed necrosis of heart muscle, hemorrhage into various organs and subcutaneous tissues, and liver damage.     

An early-branching microbialite cyanobacterium forms intracellular carbonates

Cyanobacteria have affected major geochemical cycles (carbon, nitrogen, and oxygen) on Earth for billions of years. In particular, they have played a major role in the formation of calcium carbonates (i.e., calcification), which has been considered to be an extracellular process. We identified a cyanobacterium in modern microbialites in Lake Alchichica (Mexico) that forms intracellular amorphous calcium-magnesium-strontium-barium carbonate inclusions about 270 nanometers in average diameter, revealing an unexplored pathway for calcification. Phylogenetic analyses place this cyanobacterium within the deeply divergent order Gloeobacterales. The chemical composition and structure of the intracellular precipitates suggest some level of cellular control on the biomineralization process. This discovery expands the diversity of organisms capable of forming amorphous calcium carbonates.     

利用X射线测定活体鹿茸骨化程度及其与生长速度的关系

为阐明鹿茸骨化与生长的关系,以5头雄性梅花鹿为试验材料,利用X射线测定活体鹿茸相对骨质密度（RBM）和鹿茸生长速度。结果表明：从脱盘到75d鹿茸生长速度递增并达高峰;75d以后生长速度下降,到120d基本停止生长;RBM在75d前增长缓慢,75d以后快速增长,并与鹿茸生长速度呈明显负相关（r=0.9）。     

早期乳腺癌的数字化X线征象与病理分析

目的研究早期乳腺癌的全数字化乳腺患者X线征象及病理特征．方法对12例经真空穿刺活检后病理证实为早期乳腺癌患者的X线征象进行回顾性分析．结果4例非浸润性乳腺癌患者X线表现：微细成簇钙化3例,其中1例合并局灶腺体致密,1例仅表现为局灶腺体致密．8例早期浸润癌患者X线表现：微细成簇钙化6例,肿块3例,局灶腺体致密2例,局部结构扭曲2例．结论全数字化乳腺摄影结合真空穿刺活检是诊断早期乳腺癌极为有效的方法．     

Phytoplankton calcification in a high-CO2 world

Ocean acidification in response to rising atmospheric CO2 partial pressures is widely expected to reduce calcification by marine organisms. From the mid-Mesozoic, coccolithophores have been major calcium carbonate producers in the world's oceans, today accounting for about a third of the total marine CaCO3 production. Here, we present laboratory evidence that calcification and net primary production in the coccolithophore species Emiliania huxleyi are significantly increased by high CO2 partial pressures. Field evidence from the deep ocean is consistent with these laboratory conclusions, indicating that over the past 220 years there has been a 40% increase in average coccolith mass. Our findings show that coccolithophores are already responding and will probably continue to respond to rising atmospheric CO2 partial pressures, which has important implications for biogeochemical modeling of future oceans and climate.     

Geochemical consequences of increased atmospheric carbon dioxide on coral reefs

A coral reef represents the net accumulation of calcium carbonate (CaCO3) produced by corals and other calcifying organisms. If calcification declines, then reef-building capacity also declines. Coral reef calcification depends on the saturation state of the carbonate mineral aragonite of surface waters. By the middle of the next century, an increased concentration of carbon dioxide will decrease the aragonite saturation state in the tropics by 30 percent and biogenic aragonite precipitation by 14 to 30 percent. Coral reefs are particularly threatened, because reef-building organisms secrete metastable forms of CaCO3, but the biogeochemical consequences on other calcifying marine ecosystems may be equally severe.     

Mercury poisoning: prevention by spironolactone

The renal tubular necrosis and calcification as well as the mortality induced by mercuric chloride in the rat are readily prevented by prior treatment with well-tolerated amounts of spironolactone.