CELLULAR BIOLOGY OF BONE RESORPTION

Past knowledge and the recent developments on the formation, activation and mode of action of osteoclasts, with particular reference to the regulation of each individual step, have been reviewed. The following conclusions of consensus have emerged.
1. The resorption of bone is the result of successive steps that can be regulated individually.
2. Osteoclast progenitors are formed in bone marrow. This is followed by their vascular dissemination and the generation of resting preosteoclasts and osteoclasts in bone.
3. The exact pathways of differentiation of the osteoclast progenators to mature osteoclasts are debatable, but there is clear evidence that stromal cells support osteoclast generation.
4. Osteoclasts are activated following contact with mineralized bone. This appears to be controlled by osteoblasts that expose mineral to osteoclasts and/or release a factor that activates these cells.
5. Activated osteoclasts dissolve the bone mineral and digest the organic matter of bone by the action of agents secreted in the segregated microcompartments underlying their ruffled borders. The mineral is solubilized by protons generated from CO, by carbonic anhydrase and secreted by an ATP-driven vacuolar H⁺-K⁺-ATPase located at the ruffled border. The organic matrix of the bone is removed by acid proteinases, particularly cysteine-proteinases that are secreted together with other lysosomal enzymes in the acid environment of the resorption zone.
6. Osteoclastic bone resorption is directly regulated by a polypeptide hormone, calcitonin (CT), and locally, by ionized calcium (Ca²⁺) generated as a result of osteoclastic bone resorption.
7. There is new evidence that osteoclast activity may also be influenced by the endothelial cells via generation of products including PG, NO and endothelin.     

Polymorphic microsatellite markers isolated from partially enriched genomic library of Chitala chitala

A total eight polymorphic microsatellite loci were obtained from genomic library of Indian feather back, Chitala chitala (order Osteoglossiformes, family Notopteridae) and the 46 samples were analysed to determine genetic variation. The mean number of alleles per locus ranged from 4.50 to 5.25, and expected heterozygosity ranged from 0.124 to 0.852. Deviation from Hardy–Weinberg equilibrium expectations (P < 0.002) was observed at loci Cch2, Cch9 (Bhaghirathi) and Cch9 (Brahmaputra). The identified microsatellite loci were found promising for population genetics studies of C. chitala and related species Notopterus notopterus (family Notopteridae).     

普达措国家公园四种针叶树径向生长对气候因子的响应

运用树木年代学的原理和方法,对普达措国家公园大果红杉、长苞冷杉、高山松和麦吊云杉4个优势针叶树种的年轮宽度进行测量,建立年轮宽度差值年表。分析年表与香格里拉气象站的日、月气候数据的相关性,研究4个优势针叶树种的径向生长对气候因子的响应。结果表明: 大果红杉的年生长速率最高,长苞冷杉的年生长速率最低;4种针叶树径向生长对气候因子的响应存在物种特异性,大果红杉与气候因子的相关性最强,麦吊云杉的径向生长对气候因子的响应不敏感;长苞冷杉树轮宽度年表与上年冬季(11、12月)和当年夏季(7月)的平均温度呈显著正相关;大果红杉树轮宽度年表与生长季早期(6月)温度呈显著正相关,与同期降水量和相对湿度呈显著负相关;而高山松树轮宽度年表与生长季早期(5月)的降水量和相对湿度呈显著正相关,与同期最高温度呈显著负相关,表明高山松的径向生长主要受生长季早期水分可利用性的影响。     

Occurrence of Intraxylary Phloem in Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg.

The occurrence of intraxylary phloem in Hevea brasiliensis isreported. The phloem elements were observed as strands associatedwith the protoxylem group in the pericentral region. The natureand importance of such tissue in this species are discussed. Hevea brasiliensis, intraxylary phloem, laticifers, tapping     

Association of <Emphasis Type="Italic">IL-10</Emphasis> gene (−1082A&gt;G, −819C&gt;T and −592C&gt;A) polymorphism and its serum level with metabolic syndrome of north Indian subjects

Metabolic syndrome (MetS) is an inflammatory disorder, in which various cytokines play important role in tilting balance towards disease state. Interleukin-10 (IL-10) is an important antiinflammatory cytokine, but its genetic polymorphisms and serum levels in Indian MetS subjects are unknown. Three IL-10 gene polymorphisms (?1082A >G (rs1800896), ?819C >T (rs1800872) and ?592C >A (rs1800871)) were genotyped with PCR-RFLP in MetS subjects (n = 384) and age/sex matched control subjects (n = 386). Serum IL-10 was measured using enzyme-linked immunosorbent assay. Serum IL-10 level was significantly low in MetS subject and significantly correlated with clinicobiochemical parameters of MetS. Of three investigated promoter polymorphisms, IL-10 –819C > T and –592C >A were significantly associated with risk of MetS. The mutant alleles ?819T and ?592A of IL-10 gene polymorphism were significantly higher in MetS subjects compared to controls. Of the four different haplotypes obtained, common ACC haplotype and rare GTA haplotype of IL-10 polymorphisms were associated with MetS. The mean of fasting insulin and HOMA-IR were significantly different between the genotypes of both ?819 C >T and ?592C >A polymorphisms of IL-10 in MetS subjects. These results suggested that polymorphisms in IL-10 gene (?819C >T and ?592C >A), haplotypes (ACC and GTA) and serum level are significantly associated with risk of MetS. IL-10 ?819C >T and ?592C >A polymorphic variants are also significantly associated with insulin level and homeostasis model assessment-insulin resistance in north Indian MetS subjects.