Mechanobiological oscillators control lymph flow

The ability of cells to sense and respond to physical forces has been recognized for decades, but researchers are only beginning to appreciate the fundamental importance of mechanical signals in biology. At the larger scale, there has been increased interest in the collective organization of cells and their ability to produce complex, “emergent” behaviors. Often, these complex behaviors result in tissue-level control mechanisms that manifest as biological oscillators, such as observed in fireflies, heartbeats, and circadian rhythms. In many cases, these complex, collective behaviors are controlled—at least in part—by physical forces imposed on the tissue or created by the cells. Here, we use mathematical simulations to show that two complementary mechanobiological oscillators are sufficient to control fluid transport in the lymphatic system: Ca²⁺-mediated contractions can be triggered by vessel stretch, whereas nitric oxide produced in response to the resulting fluid shear stress causes the lymphatic vessel to relax locally. Our model predicts that the Ca²⁺ and NO levels alternate spatiotemporally, establishing complementary feedback loops, and that the resulting phasic contractions drive lymph flow. We show that this mechanism is self-regulating and robust over a range of fluid pressure environments, allowing the lymphatic vessels to provide pumping when needed but remain open when flow can be driven by tissue pressure or gravity. Our simulations accurately reproduce the responses to pressure challenges and signaling pathway manipulations observed experimentally, providing an integrated conceptual framework for lymphatic function.Flow of fluid within the lymphatic system is central to many aspects of physiology, including fluid homeostasis and immune function, and poor lymphatic drainage results in significant morbidity in millions of patients each year (1). Although it is known that various mechanical and chemical perturbations can affect lymphatic pumping, there are still no pharmacological therapies for lymphatic pathologies. A fundamental understanding of how various signals coordinate lymphatic vessel function is a necessary first step toward development of treatments to restore fluid balance and enhance immunosurveillance.The lymphatic system consists of fluid-absorbing initial lymphatic vessels that converge to collecting lymphatic vessels, which transport lymph through lymph nodes and back to the blood circulation (2). The collecting lymphatic vessels actively transport fluid via contractions of their muscle-invested walls. Unidirectional flow is achieved by intraluminal valves that limit back flow. Unfortunately, lymphatic pumping is not always operational, and this can lead to lymphedema and immune dysfunction (3, 4).Much is known about the mechanisms responsible for the contractions of the vessel wall. As in blood vessels, the muscle cells that line lymphatic vessels respond to changes in Ca²⁺ concentration. Membrane depolarization results in an influx of Ca²⁺ to initiate the contractions, and this process can be modulated by neurotransmitters (5) or inflammatory mediators, which generally alter the frequency and amplitude of lymphatic pumping (4, 6). Many studies have also reported that physical distension, either by applying isometric stretch or by pressurizing the vessel can affect the phasic contractions (7–10). Interestingly, endothelial (11) and smooth muscle cells (12) have stretch-activated ion channels that can initiate Ca²⁺ mobilization in response to mechanical stresses. Thus, stretch may constitute an important trigger for the contraction phase of a pumping cycle.There are also complementary mechanisms for tempering the Ca²⁺-dependent contractions. The most notable is nitric oxide (NO), a vasodilator that acts at multiple points in the Ca²⁺-contraction pathway to modulate Ca²⁺ release and uptake, as well as the enzymes responsible for force production (13). Blocking or enhancing NO activity can dramatically affect pumping behavior (4, 14–17). Furthermore, lymphatic endothelial cells produce NO in response to fluid flow (16, 18, 19). Importantly, NO dynamics are faster than observed pumping frequencies, so flow-induced NO production is another potential mechanosignal involved in lymphatic regulation (20).     

Induction of NK activity in large granular lymphocyte leukemia: activation with anti-CD3 monoclonal antibody and interleukin 2

Large granular lymphocyte (LGL) leukemia is a rare disease characterized by clonal expansion of LGL associated with chronic neutropenia, multiple auto-antibodies, and occasionally polyarthritis. We studied cell surface antigen expression and functional activity of leukemic LGL from ten such patients. Using two-color flow cytometric analysis, we found that leukemic LGL from all ten patients expressed the CD3 and HNK-1 markers, while cells from only four patients expressed IgG Fc receptors (FcR). The LGL leukemic cells had little or no NK activity (defined as MHC-nonrestricted cytotoxicity against K562 target cells); however, NK activity could be induced in leukemic LGL by in vitro treatment with as little as 0.05 microgram/mL of anti-CD3 monoclonal antibody. Cell sorting experiments demonstrated that NK activity was induced in CD3+ leukemic LGL (either CD3+, HNK-1+ or CD3+, FcR+) with anti-CD3 monoclonal antibody but not in normal CD3+, FcR- T cells. Treatment with purified interleukin 2 (IL 2) also caused direct activation of some CD3+ leukemic LGL. Despite induction with anti-CD3 MAb or IL 2, activated leukemic LGL did not proliferate or express high density IL 2 receptors detectable by cell sorter analysis. Treatment with alpha interferon had minimal effect on NK activity of LGL leukemic cells. These results suggest that leukemic LGL may provide a useful model for examining the signals required for LGL maturation and activation.     

CD3+ leukemic large granular lymphocytes utilize diverse T-cell receptor V beta genes

CD3+ large granular lymphocyte (LGL) leukemia is a disease of unknown etiology characterized by clonal proliferation of T cells that usually express T-cell receptor (TCR) alpha beta heterodimers. The purpose of this study was to identify the variable (V), joining (J), and diversity (D) region TCR beta-chain genes expressed by CD3+ LGL leukemic cells in an attempt to gain insights into the etiology of this disorder. Twelve patients with LGL leukemia were studied, including seven with both LGL leukemia and rheumatoid arthritis (RA). RA is also a disease of unknown etiology that occurs frequently in patients with LGL leukemia. Clonally expanded T cells that express specific TCR V beta genes have been identified in fluid and tissue specimens from the joints of patients with RA. In this study, V beta expression was determined by PCR using a panel of 22 unique V beta primers to amplify cDNA prepared from peripheral blood mononuclear cells (PBMC). A dominant V beta gene product was readily apparent in all patients. To confirm that the dominant V beta gene originated from a clonal expansion, DNA fragments corresponding to the dominant V beta genes were subcloned into plasmids and independently isolated recombinants were sequenced. V-D-J region sequences that occurred repeatedly indicated clonality. The V beta and J beta genes expressed by the leukemic cells showed a pattern of distribution that followed the frequency with which these genes are represented in the peripheral blood. The residues corresponding to the third complementarity-determining region of the TCR beta chain were different in all cases. A specific pattern of VDJ usage was not identified for those patients with both LGL leukemia and RA; however, utilization of V beta-6 by LGL clones (N = 3) was observed only in the setting of RA. These data suggest that leukemic CD3+ LGL cells have been clonally transformed in a random fashion with respect to the TCR beta chain.     

Use of cyclical etidronate and prevention of non-vertebral fractures

This study examined the effects of cyclical etidronate, when used in routine clinical practice, on the prevention of fracture. Information was obtained from 550 general practices in the UK that provide their medical records to the General Practice Research Database. A total of 7977 patients taking cyclical etidronate treatment and 7977 age-, sex- and practice-matched control patients with a diagnosis of osteoporosis were analysed. People taking cyclical etidronate had a significantly reduced risk of non-vertebral fracture (by 20%) and of hip fracture (by 34%) relative to the osteoporosis control patients. The relative risk of non-vertebral fracture was 0.80 (95% confidence interval 0.70-0.92), that of hip fracture 0.66 (0.51-0.85) and that of wrist fracture 0.81 (0.58-1.14). When fracture incidence rates were compared between the two groups, the rate of non-vertebral, hip and wrist fracture decreased significantly (P < 0.05) with increasing etidronate exposure. The results of this study complement and extend clinical observations supporting the anti-fracture efficacy of cyclical etidronate therapy.      

In vitro differentiation of chick embryo bone marrow stromal cells into cartilaginous and bone-like tissues

Bone marrow stromal cells, progenitor cells involved in repair of bone and cartilage, can potentially provide a source for autologous skeletal tissue engineering. We investigated which factors were required to induce in vitro differentiation of avian bone marrow stromal cells into three-dimensional cartilaginous and bone-like tissues. Bone marrow stromal cells from embryonic chicks were expanded in monolayers, seeded onto biodegradable polyglycolic acid scaffolds, and cultured for 4 weeks in orbitally mixed Petri dishes. Cell-polymer constructs developed an organized extracellular matrix containing glycosaminoglycans and collagen, whereas control bone marrow stromal cell pellet cultures were smaller and consisted predominantly of fibrous tissue. Bone marrow stromal cells expanded with fibroblast growth factor-2 and seeded onto polymer scaffolds formed highly homogeneous three-dimensional tissues that contained cartilage-specific molecular markers and had biochemical compositions comparable with avian epiphyseal cartilage. When cell-polymer constructs were cultured in the presence of beta-glycerophosphate and dexamethasone, the extracellular matrix mineralized and bone-specific proteins were expressed. Our work shows that cell expansion in the presence of fibroblast growth factor-2 and cultivation on a three-dimensional polymer scaffold allows differentiation of chick bone marrow stromal cells into three-dimensional cartilaginous tissues. In the in vitro system studied, the same population could be selectively induced to regenerate either cartilaginous or bonelike tissue.     

高效液相色谱法测定血清中依普拉芬浓度及在人体的药代动力学研究

高效液相色谱法测定血清中依普拉芬浓度及在人体的药代动力学研究马晓红许逸刘天培（南京医科大学基础医学院药理教研室，南京２１００２９）依普拉芬（ｉｐｒｉｆｌａｖｏｎｅ，７异丙氧基异黄酮）为一合成的异黄酮衍生物，是新型治疗骨质疏松药物。它主要通过抑制骨吸...     

小檗碱对培养大鼠神经细胞内游离Ca2+的影响

以Fura-2/AM为细胞内钙离子的荧光指示剂,用AR-CM-MIC阳离子测定系统,直接测定了体外培养的新生大鼠神经细胞内游离钙([Ca²⁺]i)值,并观察了小檗碱(Ber)的影响。结果表明,Ber对神经细胞静息[Ca²⁺]i无明显影响,Ber1～100μmol·L^-1能剂量依赖地抑制去甲肾上腺素和H₂O₂引起的[Ca²⁺]i升高,其IC₅₀分别为39.9和17.9μmol·L^-1。高剂量Ber(10～100μmol·L^-1)能抑制高K+引起的[Ca²⁺]i升高。姐果提示,Ber对去甲肾上腺素,高K⁺及H₂O₂引起的[Ca²⁺]i升高的抑制作用可能是其抗脑缺血作用机制之一。     

Arthrography in the evaluation of the temporomandibular joint

Temporomandibular joint arthrography has been helpful in selecting patients for reconstructive surgery who have severe temporomandibular joint dysfunction. Structural abnormalities of the soft tissues can be demonstrated where only minimal osseous changes are seen on tomography. The normal arthrographic anatomy of the joint is reviewed and normal and pathological joints are illustrated.     

The pathogenesis of peripheral aneurysms of the central nervous system: a subject review from the AFIP

Most central nervous system aneurysms occur around the circle of Willis, and are congenital or arteriosclerotic in origin when in that location. Peripherally located aneurysms are either idiopathic or secondary to infection, tumor embolus (from choriocarcinoma and cardiac myxoma), Moyamoya disease, or trauma. The pathophysiologic features of these aneurysms are discussed.