Surfactant protein A modulates the differentiation of murine bone marrow-derived dendritic cells

Surfactant protein A (SP-A) is an innate immune molecule that regulates pathogen clearance and lung inflammation. SP-A modulates innate immune functions such as phagocytosis, cytokine production, and chemotaxis; however, little is known about regulation of adaptive immunity by SP-A. Dendritic cells (DCs) are the most potent antigen-presenting cell with the unique capacity to activate naive T cells and initiate adaptive immunity. The goal of this study was to test the hypothesis that SP-A regulates the differentiation of immature DCs into potent T cell stimulators. The data show that incubation of immature DCs for 24 h with SP-A inhibits basal- and LPS-mediated expression of major histocompatibility complex class II and CD86. Stimulation of immature DCs by SP-A also inhibits the allostimulation of T cells, enhances dextran endocytosis, and alters DC chemotaxis toward RANTES and secondary lymphoid tissue chemokine. The effects on DC phenotype and function are similar for the structurally homologous C1q, but not for SP-D. These studies demonstrate that SP-A participates in the adaptive immune response by modulating important immune functions of DCs.     

alpha(1C) (Ca(V)1.2) L-type calcium channel mediates mechanosensitive calcium regulation

Smooth muscle exhibitsmechanosensitivity independent of neural input, suggesting thatmechanosensitive pathways reside within smooth muscle cells. The nativeL-type calcium current recorded from human intestinal smooth muscle ismodulated by stretch. To define mechanosensitive mechanisms involved inthe regulation of smooth muscle calcium entry, we cloned the_1C L-type calcium channel subunit (Ca_V1.2)from human intestinal smooth muscle and expressed the channel in aheterologous system. This channel subunit retained mechanosensitivitywhen expressed alone or coexpressed with a ₂ calciumchannel subunit in HEK-293 or Chinese hamster ovary cells. Theheterologously expressed human cardiac _1C splice formalso demonstrated mechanosensitivity. Inhibition of kinase signalingdid not affect mechanosensitivity of the native channel. Truncation of the _1C COOH terminus, which containsan inhibitory domain and a proline-rich domain thought to mediatemechanosensitive signaling from integrins, did not disruptmechanosensitivity of the expressed channel. These data demonstratemechanical regulation of calcium entry through molecularly identifiedL-type calcium channels in mammalian cells and suggest that themechanosensitivity resides within the pore forming_1C-subunit.

     

Diabetes-induced changes in responsiveness of rat bladder and vas deferens to peptides in vitro: susceptibility to reversal by insulin

Changes in responsiveness of the vas deferens and urinary bladder to bradykinin (BK) receptor agonists (Tyr8-BK and des-Arg9-BK), substance P (SP), and endothelin-1 (ET-1) were assessed 8 weeks after streptozotocin (STZ)-induced diabetes. Preparations from control or STZ-treated (60 mg/kg i.p.) male rats were tested for contractile and neurogenic twitch potentiating (TP, in VD only) effects of all four agonists (1 nM to 0.3 or 3 microM). In diabetic VD, contractile effects of Tyr8-BK, des-Arg9-BK, and SP were enhanced, but ET-1 effects were unchanged. In contrast, TP by des-Arg9-BK was unaffected, that by Tyr8-BK was decreased, and those by SP and ET-1 were increased. In diabetic UB, only contractions to des-Arg9-BK and SP were enhanced. Following insulin replacement (human, 1-3 U/day s.c.), starting 1 week after STZ, TP induced by Tyr8-BK and des-Arg9-BK in VD were further inhibited, but all other changes in both preparations were reversed at least partially. Insulin treatment of nondiabetic rats, however, also affected VD (but not UB) responsiveness, such that contractions to Tyr8-BK and TP by ET-1 were increased, but TP by Tyr8-BK was decreased. Thus, STZ-induced type I diabetes causes important alterations in responsiveness of non-vascular smooth muscle tissues of the rat to BK, SP, and ET-1. Long term insulin replacement, at doses normalising glycaemia, effectively reversed most changes in VD or UB responsiveness, but it is unclear if this is truly due to blocking of STZ-induced changes, since the treatment also affected responsiveness of nondiabetic tissues.     

Neuronal differentiation from postmitotic precursors in the ciliary ganglion

In the chick ciliary ganglion, neuronal number is kept constant between St. 29 and St. 34 (E6-E8) despite a large amount of cell death. Here, we characterize the source of neurogenic cells in the ganglion as undifferentiated neural crest-derived cells. At St. 29, neurons and nonneuronal cells in the ciliary ganglion expressed the neural crest markers HNK-1 and p75(NTR). Over 50% of the cells were neurons at St. 29; of the nonneuronal cells, a small population expressed glial markers, whereas the majority was undifferentiated. When placed in culture, nonneuronal cells acquired immunoreactivity for HuD, suggesting that they had commenced neuronal differentiation. The newly differentiated neurons arose from precursors that did not incorporate bromodeoxyuridine. To test whether these precursors could undergo neural differentiation in vivo, purified nonneuronal cells from St. 29 quail ganglia were transplanted into chick embryos at St. 9-14. Subsequently, quail cells expressing neuronal markers were found in the chick ciliary ganglion. The existence of this precursor pool was transient because nonneuronal cells isolated from St. 38 ganglia failed to form neurons. Since all ciliary ganglion neurons are born prior to St. 29, these results demonstrate that there are postmitotic neural crest-derived precursors in the developing ciliary ganglion that can differentiate into neurons in the appropriate environment.     

Ancestral loss of the maxillary sinus in Old World monkeys and independent acquisition in Macaca

Cercopithecoid monkeys are unique among primates in that all species (except macaques) lack a maxillary sinus, an unusual condition among eutherian mammals. Although this uncommon distribution of cranial pneumatization was noted previously, the phylogenetic ramifications have not been investigated fully. Recently, character state optimization analysis of computed tomography (CT) data from extant Old World monkeys suggested that the loss of the sinus may have occurred at the origin of the group, unlike previous hypotheses positing only a reduction in size of the structure. To critically evaluate the "early loss" hypothesis, a recently recovered complete cranium of Victoriapithecus macinnesi from Maboko Island, Kenya, was examined by CT to determine the extent of its cranial pneumatization. This taxon is crucial for evaluating character state evolution in Old World monkeys, due to its phylogenetic position, preceding the cercopithecine/colobine split. CT analysis reveals only cancellous bone lateral of the nasal cavity, indicating that Victoriapithecus does not possess a maxillary sinus. Phylogenetic evaluation of the fossil with extant catarrhine taxa strongly supports the early loss of the sinus in cercopithecoids. The results suggest that the maxillary sinus found in the genus Macaca is not homologous with that of other eutherians, which may provide insights into the origin and function (if any) of the paranasal pneumatizations.     

Structural analysis of thermosome from hyperthermophilic archaeon Thermococcus

The purification and characterization of thermostable chaperonin of the thermosome family from hyperthermophilic archaeon Thermococcus profunds are described. The purified thermosome is a homooligomeric complex and an ATPase with maximal activity at 80 degrees C. The electron micrographs obtained from negatively stained as well as frozen-hydrated specimen showed an eight-fold symmetry of chaperonin. They were about 15 nm height and 16 nm in diameter with a central cavity of 5 nm. In order to understand the ATPase cycling of thermosome, we analyzed the oligomeric structure of thermosome treated with several nucleotides.     

Surfactant protein A regulates surfactant phospholipid clearance after LPS-induced injury in vivo

Previous in vitro studies have suggested that surfactant protein A (SP-A) may play a role in pulmonary surfactant homeostasis by mediating surfactant secretion and clearance. However, mice made deficient in SP-A [SP-A (-/-) animals] have relatively normal levels of surfactant compared with wild-type SP-A (+/+) animals. We hypothesize that SP-A may play a role in surfactant homeostasis after acute lung injury. Bacterial lipopolysaccharide was instilled into the lungs of SP-A (-/-) mice and SP-A (+/+) mice to induce injury. Surfactant phospholipid levels were increased 1.6-fold in injured SP-A (-/-) animals, although injury did not alter [3H]choline or [14C]palmitate incorporation into dipalmitoylphosphatidylcholine (DPPC), suggesting no change in surfactant synthesis/secretion 12 h after injury. Clearance of [3H]DPPC from the lungs of injured SP-A (-/-) animals was decreased by approximately 40%. Instillation of 50 microg of exogenous SP-A rescued both the clearance defect and the increased phospholipid defect in injured SP-A (-/-) animals, suggesting that SP-A may play a role in regulating clearance of surfactant phospholipids after acute lung injury.     

Gates and oscillators: a network model of the brain clock

The suprachiasmatic nuclei (SCN) control circadian oscillations of physiology and behavior. Measurements of electrical activity and of gene expression indicate that these heterogeneous structures are composed of both rhythmic and nonrhythmic cells. A fundamental question with regard to the organization of the circadian system is how the SCN achieve a coherent output while their constituent independent cellular oscillators express a wide range of periods. Previously, the consensus output of individual oscillators had been attributed to coupling among cells. The authors propose a model that incorporates nonrhythmic "gate" cells and rhythmic oscillator cells with a wide range of periods, that neither requires nor excludes a role for interoscillator coupling. The gate provides daily input to oscillator cells and is in turn regulated (directly or indirectly) by the oscillator cells. In the authors' model, individual oscillators with initial random phases are able to self-assemble so as to maintain cohesive rhythmic output. In this view, SCN circuits are important for self-sustained oscillation, and their network properties distinguish these nuclei from other tissues that rhythmically express clock genes. The model explains how individual SCN cells oscillate independently and yet work together to produce a coherent rhythm.