The myofibroblast, cadherin, alpha smooth muscle actin and the collagen effect

In granulation tissue the myofibroblast, a specialized fibroblast characterized by cytoplasmic stress fibres with alpha smooth muscle actin (SMA), develops from mechano-tension between cells. In vitro the myofibroblast phenotype can be induced in the absence of obvious tension by plating human dermal fibroblasts at low density (LD). Upon reaching confluence the LD-plated cells express alpha SMA within stress fibres. In contrast, few cells express alpha SMA when those same fibroblasts are plated at high density (HD). Cadherins, trans-membrane proteins, and link cells tie the cytoskeletal stress fibres of neighbouring cells together. By immunohistology myofibroblasts (LD-plated fibroblasts) are shown to express cadherin-11 on their surface and between cells, while HD-plated fibroblasts expressed less cadherin-11 on their surface. Western blot analysis revealed elevated concentrations of cadherin-11 and alpha SMA in confluent LD-plated cell lysates. Reduced amounts of both proteins were found in confluent HD-plated cell lysates. Plating fibroblasts on collagen inhibits alpha SMA synthesis. When confluent LD-plated myofibroblasts were covered with a collagen lattice for 24 h, both the expression of cadherin-11 and alpha SMA were reduced by 50%. There is the possibility that direct linkage of the cytoskeleton stress fibres by cell surface cadherins maintains tension between neighbouring cells, which induces alpha SMA expression in stress fibres. Cell contact with collagen reduces cadherin expression, which may eliminate the generation of mechano-tension between fibroblasts. The other possibility is that the myofibroblast phenotype may be induced by factors other than mechano-tension.     

中国洞穴蜘蛛多样性及其对洞穴环境的适应

对中国洞穴蜘蛛的多样性、地理分布信息进行了详细的闸述.初步探讨了洞穴蜘蛛对洞穴环境的适应性特征及其进化机制.我国洞穴蜘蛛目前已知16科27属80种,其巾暗蛛科、弱蛛科、泰莱蛛科和巨蟹蛛科物种最多;在属级阶元上,以弱蛛属Leptoneta14种、泰莱蛛属Telema lO种、龙角蛛属Draamar如和巾遁蛛属Sinopoda各9种,宽隙蛛属Platocoelotes 8种居多.我国洞穴蜘蛛主要集中分布在贵卅、海南、云南、北京、浙江、广西等喀斯特洞穴较为密集地区,在河北、河南、湖北和湖南也有部分报道.在不同地区分布的洞穴蜘蛛类群或优势类群及区系成分等都存在较大差异.洞穴蜘蛛中约有20%～30%的种类凶为长期生活在黑暗无光、食物匮乏以及缺乏温度和光周期的季节调节等特殊环境,出现了一些地表生境蜘蛛类群中所没有的刘洞穴环境的适应性特征,如缺乏体色素、眼退化共至无眼、附肢延长、全身牛有很多具较敏锐触觉和嗅觉功能的感觉毛、繁殖无季节性、耗氧量降低而新陈代谢缓慢、代谢率降低、产牛的后代少、单个卵粒包含更多的营养等.     

Daily and hourly movement of male desert-dwelling elephants

The daily and hourly movements of eight male desert-dwelling elephants of various ages (12–45 years old) were determined hourly by global positioning system (GPS)/telemetry collars during the wet, cold dry and hot dry seasons of 2006 in northwest Namibia. The average daily movement in the wet season was greater than that observed during either the cold dry or the hot dry seasons. A similar difference was also observed for the movement rates, with the highest average rate of hourly movement recorded during the wet season. The diurnal movements (both distance and rate) were greater than those in the nocturnal hours during the wet season, whilst during the cold dry and hot dry season the reverse was true. The daily cycle of movement also changed seasonally, with greatest movement rates observed during the wet season between 11.00–20.00 hours, during the cold dry season between 14.00–21.00 hours; and between 04.00–11.00 hours during the hot dry season. Periods of decreased movement rates were observed between 09.00–10.00 and 02.00–03.00 hours in the wet season; 03.00–06.00 and 11.00–13.00 hours in the cold dry season; and 01.00–03.00 and 12.00–14.00 hours during the hot dry season.     

Ultrastructural localization of epithelial mucin core proteins in colorectal tissues.

Mucins are high molecular weight glycoproteins with a variety of postulated biological functions, including physicochemical protection from toxins and mutagens, adhesion modulation, signal transduction, and regulation of cell growth. Mucins are widely and differentially expressed in the gastrointestinal tract. To date, studies of cellular expression have relied on light microscopy using in situ hybridization and immunohistochemistry. Although informative, it has been difficult with these techniques to ascertain exactly which cell types are producing a given mucin. We studied expression of MUC1, MUC2, and MUC4 apomucins in a series of normal colon biopsies using a combination of immunoelectron microscopy and light microscopy. MUC1 mucin was localized to both goblet and columnar cells, where it was seen in secretory vesicles, microvilli, and in cytoplasmic remnants in goblet cell thecae. MUC2 expression was restricted to goblet cells, in which reactivity was concentrated in the rough endoplasmic reticulum (RER). MUC4 expression was seen in both columnar and goblet cells, localized to the RER. The inability to detect MUC2 and MUC4 apomucins in the Golgi complex and the mature mucous gel probably represents masking of peptide epitopes following O-glycosylation. This study has helped clarify lineage-specific mucin synthesis in the normal colon.     

关联维数法在皮肤激光散斑测量中的应用

本文采用关联维数方法研究了皮肤厚度对皮肤激光散斑测量的影响。计算了６种模拟皮肤厚度情况下的生物散斑关联维数。结果表明,维数随皮肤厚度的增加而减小,而且重复性很好。这说明,关联维数方法可以应用在皮肤激光散斑的研究中     

Role of prostaglandins in controlling plasma fibronectin levels

Fibronectin is a normal glycoprotein component of plasma, interstitial fluid, and extracellular matrix which has binding sites for collagen, gelatin, actin, glycosaminoglycans, fibrin, Staphylococcus aureus, and some cells. Since it is a dimer, it can crosslink these substances to each other or to extracellular components of basement membrane, thereby affecting many physiological processes. The level of circulating fibronectin is markedly reduced following even moderate blunt or operative trauma, thermal injury, starvation, advanced cancers, hemorrhage, etc. Replacement therapy has been tried with some success in patients who become septic following multiple injuries. The reduction in plasma fibronectin has been attributed to several causes including consumption by binding to cell debris at the site of injury, binding to circulating cell debris and its subsequent removal by elements of the phagocytic system, and degradation by proteolytic cleavage. However, the amount of fibronectin removed from circulation raises some question about this. In this paper, we used indomethacin, ibuprofen, imidazole, and essential fatty acid deprivation to inhibit the synthesis of prostaglandins in young adult rats. Thirty minutes after ip administration of one of the inhibitors, the rats were subjected to a midline laparotomy and mild intestinal manipulation. Blood samples were taken at intervals following closure of the incision and analyzed for fibronectin. In all cases, the normal decline in plasma fibronectin seen in untreated rats was abrogated by inhibiting prostaglandin synthesis. Since imidazole specifically inhibits thromboxane A synthesis, this strongly suggests that thromboxanes directly or indirectly control the trauma-induced reduction in circulating fibronectin. This was confirmed by ip injection of thromboxane into the rats which resulted in a decline in plasma fibronectin levels.     

ENVIRONMENTAL CONDITIONS, GROWTH AND PRODUCTION OF ANADARA SENILIS (LINNAEUS, 1758) IN A SENEGAL LAGOON

Two populations of Anadara senilis were sampled periodicallyin a lagoon of Senegal. Spatfall occurs in summer during therainy season. Population density decreases from about 50, 000.m^–2,two months after spatfall, down to 6, 750 one year later and750 after 28 months. The average growth, measured on the surfaceof the shell, following the umbo rim axis is 0.8 mm per month.The main reduction in growth rate occurs in winter and endsby the deposition of a growth ring. A second growth reductiontakes place during the rainy season and sometimes ends by aweak growth ring. The microgrowth increments are conspicuousand widest during spring equinox. They are not directly relatedto the tidal cycle, but it was impossible to determine if theyhave a tidal or a daily periodicity. (Received 11 February 1990; accepted 16 July 1993)     

A retinal substrate for colour discrimination in crabs

Summary In crabs, there is behavioural evidence for colour discrimination from the portunidCarcinus and severalUca species, but in the same and related species only a single visual pigment has been found in the rhabdoms by microspectrophotometry. Micro-electrode recordings of the spectral sensitivity of single portunid photoreceptors may throw some light on this apparent inconsistency. Large changes in spectral sensitivity occur with light adaptation in the crabScylla serrata. Selective adaptation experiments rule out the possibility that the changes may be caused by the presence of a number of visual pigments or of antenna pigments. The results suggest that inScylla the absorption of a single visual pigment type is modified by different coloured filters in different photoreceptors and that this makes colour discrimination possible.     

The importance of within-system spatial variation in drivers of marine ecosystem regime shifts

Comparative analyses of the dynamics of exploited marine ecosystems have led to differing hypotheses regarding the primary causes of observed regime shifts, while many ecosystems have apparently not undergone regime shifts. These varied responses may be partly explained by the decade-old recognition that within-system spatial heterogeneity in key climate and anthropogenic drivers may be important, as recent theoretical examinations have concluded that spatial heterogeneity in environmental characteristics may diminish the tendency for regime shifts. Here, we synthesize recent, empirical within-system spatio-temporal analyses of some temperate and subarctic large marine ecosystems in which regime shifts have (and have not) occurred. Examples from the Baltic Sea, Black Sea, Bengula Current, North Sea, Barents Sea and Eastern Scotian Shelf reveal the largely neglected importance of considering spatial variability in key biotic and abiotic influences and species movements in the context of evaluating and predicting regime shifts. We highlight both the importance of understanding the scale-dependent spatial dynamics of climate influences and key predator–prey interactions to unravel the dynamics of regime shifts, and the utility of spatial downscaling of proposed mechanisms (as evident in the North Sea and Barents Sea) as a means of evaluating hypotheses originally derived from among-system comparisons.