Susceptibility of dopamine D5 receptor targeted mice to cysteamine

BACKGROUND: Recently we demonstrated that gastric mucosa of rats can synthesize, store and release dopamine. Out of five different subtypes, mRNA of D5 (=D1b) dopamine receptor is very abundant in the gastric epithelium. D1 receptor selective dopamine agonists have been shown to protect against experimental gastro-duodenal lesions. AIMS: To test the hypothesis that protective effects of dopamine involve D5 receptors, mucosal lesions were induced in D5 receptor deficient (KO) and wild-type (WT) mice using cysteamine. Morphology and gastric acid secretion of D5 KO mice were also studied. METHODS: Single doses of 600 mg/kg, 300 mg/kg cysteamine or vehicle were administered subcutaneously to fasted animals. After 24 h, number and severity of gastro-duodenal lesions were analyzed. Basal and histamine-induced maximal gastric acid output were measured by a stomach-sac wash-through method. RESULTS: All the KOs in the 600 mg/kg cysteamine group died within 4 h showing symptoms of toxicity while three out of four WTs survived (P<0.05). Mortality after 300 mg/kg cysteamine was significantly higher in KOs versus the WTs: 6/14 versus 2/11, P<0.05. Gastric lesion-index was also significantly higher in KOs (median, middle quartile): four (3-9) versus 0 (0-0), P<0.05. Duodenal lesions did not develop from this single dose of cysteamine in either genotype. Basal and histamine-induced maximal gastric acid output were comparable in the two genotypes. CONCLUSIONS: This study demonstrates that loss of D5 receptor causes mucosal vulnerability and increased toxicity of cysteamine in genetically manipulated mice. Thus, D5 receptor subtype is indeed likely to be involved in protective effects of dopamine in the stomach.     

The Expression of Connexins and SOX2 Reflects the Plasticity of Glioma Stem-Like Cells

Glioblastoma (GBM) is the most malignant primary brain tumor, with an average survival rate of 15 months. GBM is highly refractory to therapy, and such unresponsiveness is due, primarily, but not exclusively, to the glioma stem-like cells (GSCs). This subpopulation express stem-like cell markers and is responsible for the heterogeneity of GBM, generating multiple differentiated cell phenotypes. However, how GBMs maintain the balance between stem and non-stem populations is still poorly understood. We investigated the GBM ability to interconvert between stem and non-stem states through the evaluation of the expression of specific stem cell markers as well as cell communication proteins. We evaluated the molecular and phenotypic characteristics of GSCs derived from differentiated GBM cell lines by comparing their stem-like cell properties and expression of connexins. We showed that non-GSCs as well as GSCs can undergo successive cycles of gain and loss of stem properties, demonstrating a bidirectional cellular plasticity model that is accompanied by changes on connexins expression. Our findings indicate that the interconversion between non-GSCs and GSCs can be modulated by extracellular factors culminating on differential expression of stem-like cell markers and cell-cell communication proteins. Ultimately, we observed that stem markers are mostly expressed on GBMs rather than on low-grade astrocytomas, suggesting that the presence of GSCs is a feature of high-grade gliomas. Together, our data demonstrate the utmost importance of the understanding of stem cell plasticity properties in a way to a step closer to new strategic approaches to potentially eliminate GSCs and, hopefully, prevent tumor recurrence.     

Neuropeptide Y and peptide YY neuronal and endocrine systems

An extensive system of neuropeptide Y (NPY) containing neurons has recently been identified in the central and peripheral nervous system. In addition, NPY and a structurally related peptide, peptide YY (PYY), containing endocrine cells have been identified in the periphery. The NPY system is of particular interest as the peptide coexists with catecholamines in the central and sympathetic nervous system and adrenal medulla. Evidence has been presented which indicates that NPY may play important roles in regulating autonomic function.     

Duration of strike-induced chemosensory searching in long-term captive rattlesnakes at national zoo,audubon zoo,and San Diego Zoo

Rattlesnakes typically strike and release adult rodent prey. Striking is followed by a sustained, high rate of tongue flicking that guides the snake to the envenomated, dead prey. Wild-caught rattlesnakes exhibited this chemosensory searching for about 2.5 h, and the present study demonstrated that long-term captive rattlesnakes (Crotalus atrox, C durissus, C horridus, C vegrandis, C unicolor) at three zoos did the same. Because these zoo-raised snakes had always been offered dead rodents and because the snakes had become accustomed to ingesting them without striking, the present snakes had rarely exercised their innate predatory repertoires. The duration of chemosensory searching in these snakes indicates that this important aspect of the predatory repertoire had not been degraded as a consequence of long-term captive husbandry.     

Insertion of inverted Ter sites into the terminus region of the Escherichia coli chromosome delays completion of DNA replication and disrupts the cell cycle

To investigate the co-ordination between DNA replication and cell division, we have disrupted the DNA replication cycle of Escherichia coli by inserting inverted Ter sites into the terminus region to delay completion of the chromosome. The inverted Ter sites (designated Inv Ter :: spc ^r) were initially inserted into the chromosome of a Δ tus strain to allow unrestrained chromosomal replication. We then introduced a functional tus gene by transforming the Inv Ter :: spc ^r strain with a plasmid carrying the tus gene under control of an arabinose-inducible promoter. In the presence of 0.2% arabinose, the cells formed long filaments, suggesting that activation of the inverted Ter sites by Tus arrested DNA replication and delayed the onset of cell division. Induction of sfiA , a gene in the SOS regulon, was observed following arrest of DNA replication; however, when a sfiB114 allele was introduced into Inv Ter :: spc ^r strain, long filaments were still formed, suggesting that the sfi -independent pathway also caused filamentation. Either recA :: cam ^r or lexA3 alleles suppressed filamentation when introduced in the Inv Ter strain. Interestingly, in both the recA :: cam ^r and lexA3 mutants, virtually all cells had a nucleoid, suggesting that cell division was proceeding even though DNA replication was not complete. These results suggest that DNA replication and cell division are uncoupled when recA is inactivated or when genes repressed by LexA cannot be induced.     

Branching design of the bronchial tree based on a diameter-flow relationship

Kitaoka, Hiroko, and Béla Suki. Branching designof the bronchial tree based on a diameter-flow relationship.J. Appl. Physiol. 82(3): 968-976, 1997.We propose a method for designing the bronchial tree where thebranching process is stochastic and the diameter(d) of a branch is determined by itsflow rate (Q). We use two principles: the continuumequation for flow division and a power-law relationship betweend and Q, given by Q ~ dⁿ,where n is the diameter exponent. The value ofn has been suggested to be ~3. Weassume that flow is divided iteratively with a random variable for theflow-division ratio, defined as the ratio of flow in the branch to thatin its parent branch. We show that the cumulative probabilitydistribution function of Q, P(>Q) is proportional to Q¹. Weanalyzed prior morphometric airway data (O. G. Raabe, H. C. Yeh, H. M. Schum, and R. F. Phalen, Report No.LF-53, 1976) and found that the cumulative probabilitydistribution function of diameters, P(>d), isproportional to dⁿ, which supportsthe validity of Q ~ dⁿ sinceP(>Q) ~ Q¹. This allowed us toassign diameters to the segments of the flow-branching pattern. Wemodeled the bronchial trees of four mammals and found that theirstatistical features were in good accordance with the morphometricdata. We conclude that our design method is appropriate for robustgeneration of bronchial tree models.

     

Dynamic properties of lung parenchyma: mechanical contributions of fiber network and interstitial cells

Yuan, Huichin, Edward P. Ingenito, and Béla Suki.Dynamic properties of lung parenchyma: mechanical contributions offiber network and interstitial cells. J. Appl.Physiol. 83(5): 1420-1431, 1997.We investigatedthe contributions of the connective tissue fiber network andinterstitial cells to parenchymal mechanics in a surfactant-freesystem. In eight strips of uniform dimension from guinea pig lung, weassessed the storage (G) and loss (G") moduli by usingpseudorandom length oscillations containing a specially designed set ofseven frequencies from 0.07 to 2.4 Hz at baseline, during methacholine(MCh) challenge, and after death of the interstitial cells.Measurements were made at mean forces of 0.5 and 1 g and strainamplitudes of 5, 10, and 15% and were repeated 12 h later in the same,but nonviable samples. The results were interpreted using a linearviscoelastic model incorporating both tissue damping (G) and stiffness(H). The G and G" increased linearly with the logarithmof frequency, and both G and H showed negative strain amplitude andpositive mean force dependence. After MCh challenge, the G andG" spectra were elevated uniformly, and G and H increased by<15%. Tissue stiffness, strain amplitude, and mean force dependencewere virtually identical in the viable and nonviable samples. The G andhence energy dissipation were ~10% smaller in the nonviable samplesdue to absence of actin-myosin cross-bridge cycling. We conclude thatthe connective tissue network may also dominate parenchymal mechanicsin the intact lung, which can be influenced by the tone or contractionof interstitial cells.

     

In vitro modulation of natural killer cell activity in non-Hodgkin's lymphoma patients after therapy

Summary The depressed natural killer (NK) activity, antibody-dependent cellular cytotoxicity (ADCC) and NK cytotoxic factor cytotoxicity in untreated non-Hodgkin's lymphoma patients were found to be elevated after chemotherapy. In vitro treatment of the effector NK cells with interferon could augment the NK activity in normal subjects and treated patients to a comparable degree. Chemotherapy mainly affected the post-binding events in the NK cytotoxic process by causing an increase in the active killing potential of the NK cells. This study provides a better understanding of changes in the NK cytotoxic mechanism in non-Hodgkin's lymphoma patients and the role of interferon in this process.B. A. Mehta is a recipient of the Lady Tata Memorial Trust, India, Senior Scholarship