Protein-based human iPS cells efficiently generate functional dopamine neurons and can treat a rat model of Parkinson disease

Parkinson disease (PD) involves the selective loss of midbrain dopamine (mDA) neurons and is a possible target disease for stem cell-based therapy. Human induced pluripotent stem cells (hiPSCs) are a potentially unlimited source of patient-specific cells for transplantation. However, it is critical to evaluate the safety of hiPSCs generated by different reprogramming methods. Here, we compared multiple hiPSC lines derived by virus- and protein-based reprogramming to human ES cells (hESCs). Neuronal precursor cells (NPCs) and dopamine (DA) neurons delivered from lentivirus-based hiPSCs exhibited residual expression of exogenous reprogramming genes, but those cells derived from retrovirus- and protein-based hiPSCs did not. Furthermore, NPCs derived from virus-based hiPSCs exhibited early senescence and apoptotic cell death during passaging, which was preceded by abrupt induction of p53. In contrast, NPCs derived from hESCs and protein-based hiPSCs were highly expandable without senescence. DA neurons derived from protein-based hiPSCs exhibited gene expression, physiological, and electrophysiological properties similar to those of mDA neurons. Transplantation of these cells into rats with striatal lesions, a model of PD, significantly rescued motor deficits. These data support the clinical potential of protein-based hiPSCs for personalized cell therapy of PD.

Virilizing adrenocortical oncocytoma in a child: a case report

Functioning adrenocortical oncocytomas are extremely rare and most reported patients are 40-60 yr of age. To our knowledge, only 2 cases of functioning adrenocortical oncocytomas have been reported in childhood. We report a case of functioning adrenocortical oncocytoma in a 14-yr-old female child presenting with virilization. She presented with deepening of the voice and excessive hair growth, and elevation of plasma testosterone and dehydroepiandrosterone sulfate. She had an adrenalectomy. The completely resected tumor composed predominantly of oncocytes without atypical mitosis and necrosis. A discussion of this case and a review of the literature on this entity are presented.

Foxa2 and Nurr1 synergistically yield A9 nigral dopamine neurons exhibiting improved differentiation, function, and cell survival

Effective dopamine (DA) neuron differentiation from neural precursor cells (NPCs) is prerequisite for precursor/stem cell-based therapy of Parkinson's disease (PD). Nurr1, an orphan nuclear receptor, has been reported as a transcription factor that can drive DA neuron differentiation from non-dopaminergic NPCs in vitro. However, Nurr1 alone neither induces full neuronal maturation nor expression of proteins found specifically in midbrain DA neurons. In addition, Nurr1 expression is inefficient in inducing DA phenotype expression in NPCs derived from certain species such as mouse and human. We show here that Foxa2, a forkhead transcription factor whose role in midbrain DA neuron development was recently revealed, synergistically cooperates with Nurr1 to induce DA phenotype acquisition, midbrain-specific gene expression, and neuronal maturation. Thus, the combinatorial expression of Nurr1 and Foxa2 in NPCs efficiently yielded fully differentiated nigral (A9)-type midbrain neurons with clearly detectable DA neuronal activities. The effects of Foxa2 in DA neuron generation were observed regardless of the brain regions or species from which NPCs were derived. Furthermore, DA neurons generated by ectopic Foxa2 expression were more resistant to toxins. Importantly, Foxa2 expression resulted in a rapid cell cycle exit and reduced cell proliferation. Consistently, transplantation of NPCs transduced with Nurr1 and Foxa2 generated grafts enriched with midbrain-type DA neurons but reduced number of proliferating cells, and significantly reversed motor deficits in a rat PD model. Our findings can be applied to ongoing attempts to develop an efficient and safe precursor/stem cell-based therapy for PD.

Syndrome of inappropriate secretion of antidiuretic hormone as a leading cause of hyponatremia in children who underwent chemotherapy or stem cell transplantation

BACKGROUND

Hyponatremia is a common metabolic disorder in cancer patients. However, little information is available for patients receiving chemotherapy or stem cell transplantation (SCT). We analyzed the frequency, characteristics, and various causes of hyponatremia including routine use of hypotonic fluids in children following chemotherapy or SCT.

PROCEDURE

We reviewed the clinical and laboratory data of 63 children who received chemotherapy or SCT at the Department of Pediatrics, Hanyang University Medical Center from July 2005 to July 2008.

RESULTS

All 63 patients at admission received routine parenteral fluids of 0.25% or 0.45% NaCl and 82 episodes of hyponatremia were observed in 40 (63.5%) patients. Of these 82 episodes, 50 episodes of hyponatremia developed in 29 children following chemotherapy and 32 episodes in 16 children following SCT. Seventy-six out of 82 episodes (92.7%) of hyponatremia developed in 37 patients receiving hypotonic fluids with NaCl concentrations between 30 and 150 mEq/L. The frequency of SIADH in the SCT setting was more frequent (14/21, 66.6%) than in the chemotherapy setting (18/58, 31.0%) (P = 0.02), even though the leading cause of hyponatremia was SIADH in both settings.

CONCLUSIONS

SIADH is a leading cause of hyponatremia in children following chemotherapy or SCT, and more frequent in SCT settings than in chemotherapy settings. Furthermore, the routine use of hypotonic fluids which could aggravate the development of hyponatremia for these patients should be avoided and then switched to isotonic fluids.

Generation of dopamine neurons with improved cell survival and phenotype maintenance using a degradation-resistant nurr1 mutant

Nurr1 is a transcription factor specific for the development and maintenance of the midbrain dopamine (DA) neurons. Exogenous Nurr1 in neural precursor (NP) cells induces the differentiation of DA neurons in vitro that are capable of reversing motor dysfunctions in a rodent model for Parkinson disease. The promise of this therapeutic approach, however, is unclear due to poor cell survival and phenotype loss of DA cells after transplantation. We herein demonstrate that Nurr1 proteins undergo ubiquitin-proteasome-system-mediated degradation in differentiating NP cells. The degradation process is activated by a direct Akt-mediated phosphorylation of Nurr1 proteins and can be prevented by abolishing the Akt-target sequence in Nurr1 (Nurr1^Akt). Overexpression of Nurr1^Akt in NP cells yielded DA neurons in which Nurr1 protein levels were maintained for prolonged periods. The sustained Nurr1 expression endowed the Nurr1^Akt-induced DA neurons with resistance to toxic stimuli, enhanced survival, and sustained DA phenotypes in vitro and in vivo after transplantation.

Conditions for tumor-free and dopamine neuron-enriched grafts after transplanting human ES cell-derived neural precursor cells

We have previously demonstrated derivation of neural precursor (NP) cells of a midbrain-type from human embryonic stem (hES) cells to yield an enriched population of dopamine (DA) neurons. These hES-derived NPs can be expanded in vitro through multiple passages without altering their DA neurogenic potential. Here, we studied two aspects of these hES-NP cells that are critical issues in cell therapeutic approaches for Parkinson's disease (PD): cell survival and tumorigenic potential. Neuroepithelial rosettes, a potentially tumorigenic structure, disappeared during hES-NP cell expansion in vitro. Although a minor population of cells positive for Oct3/4, a marker specific for undifferentiated hES cells, persisted in culture during hES-NP cell expansion, they could be completely eliminated by subculturing hES-NPs under differentiation-inducing conditions. Consistently, no tumors/teratomas are formed in rats grafted with multipassaged hES-NPs. However, extensively expanded hES-NP cells easily underwent cell death during differentiation in vitro and after transplantation in vivo. Transgenic expression of Bcl-XL and sonic hedgehog (SHH) completely overcame the cell survival problems without increasing tumor formation. These findings indicate that hES-NP cell expansion in conjunction with Bcl-XL+SHH transgene expression may provide a renewable and safe source of DA neurons for transplantation in PD.

Human embryonic stem cell-derived neural precursors as a continuous, stable, and on-demand source for human dopamine neurons

Human embryonic stem (hES) cells can be guided to differentiate into ventral midbrain-type neural precursor (NP) cells that proliferate in vitro by specific mitogens. We investigated the potential of these NP cells derived from hES cells (hES-NP) for the large-scale generation of human dopamine (DA) neurons for functional analyses and therapeutic applications. To address this, hES-NP cells were expanded in vitro for 1.5 months with six passages, and their proliferation and differentiation properties determined over the NP passages. Interestingly, the total hES-NP cell number was increased by > 2 x 10(4)-folds over the in vitro period without alteration of phenotypic gene expression. They also sustained their differentiation capacity toward neuronal cells, exhibiting in vitro pre-synaptic DA neuronal functionality. Furthermore, the hES-NP cells can be cryopreserved without losing their proliferative and developmental potential. Upon transplantation into a Parkinson's disease rat model, the multi-passaged hES-NP cells survived, integrated into the host striatum, and differentiated toward the neuronal cells expressing DA phenotypes. A significant reduction in the amphetamine-induced rotation score of Parkinson's disease rats was observed by the cell transplantation. Taken together, these findings indicate that hES-NP cell expansion is exploitable for a large-scale generation of experimental and transplantable DA neurons of human-origin.

Generation of functional dopamine neurons from neural precursor cells isolated from the subventricular zone and white matter of the adult rat brain using Nurr1 overexpression

Neural precursor (NP) cells from adult mammalian brains can be isolated, expanded in vitro, and potentially used as cell replacement source material for treatment of intractable brain disorders. Reduced ethical concerns, lack of teratoma formation, and possible ex vivo autologous transplantation are critical advantages to using adult NP donor cells over cells from fetal brain tissue or embryonic stem cells. However, the usage of adult NP cells is limited by the ability to induce specific neurochemical phenotypes in these cells. Here, we demonstrate induction of a dopaminergic phenotype in NP cells isolated from the subventricular zone (SVZ) and white matter of rodent adult brains using overexpression of the nuclear receptor Nurr1 in vitro. Forced expression of Nurr1, a transcriptional factor specific to midbrain dopamine (DA) neuron development, caused in the adult cells an acquisition of the DA neurotransmitter phenotype and sufficient differentiation toward morphologically, phenotypically, and ultrastructurally mature DA neurons. Co-expression of neurogenic factor Mash1 and treatment with neurogenic cytokines brain-derived neurotrophic factor and neurotrophin-3 greatly enhanced Nurr1-induced DA neuron yield. The Nurr1-induced DA neurons demonstrated in vitro presynaptic DA neuronal functionality, releasing DA neurotransmitter in response to depolarization stimuli and specific DA reuptake. Furthermore, Nurr1-engineered adult SVZ NP cells survived, integrated, and differentiated into DA neurons in vivo that can reverse the behavioral deficit in the host striatum of parkinsonian rats. These findings open the possibility for the use of precursor cells from adult brains as a cell source for neuronal replacement treatment of Parkinson disease. Disclosure of potential conflicts of interest is found at the end of this article.

Acquisition of in vitro and in vivo functionality of Nurr1-induced dopamine neurons

Neural precursor cells provide an expandable source of neurons and glia for basic and translational applications. However, little progress has been made in directing naive neural precursors toward specific neuronal fates such as midbrain dopamine (DA) neurons. We have recently demonstrated that transgenic expression of the nuclear orphan receptor Nurr1 is sufficient to drive dopaminergic differentiation of forebrain embryonic rat neural precursors in vitro. However, Nurr1-induced DA neurons exhibit immature neuronal morphologies and functional properties and are unable to induce behavioral recovery in rodent models of Parkinson's disease (PD). Here, we report on the identification of key genetic factors that drive morphological and functional differentiation of Nurr1-derived DA neurons. We show that coexpression of Nurr1, Bcl-XL, and Sonic hedgehog (SHH) or Nurr1 and the proneural bHLH factor Mash1 is sufficient to drive naive rat forebrain precursors into neurons exhibiting the biochemical, electrophysiological, and functional properties of DA neuron in vitro. On transplantation into the striatum of Parkinsonian rats, precursor cells engineered with Nurr1/SHH/Bcl-XL or Nurr1/Mash1 survived in vivo and differentiated into mature DA neurons that can reverse the behavioral deficits in the grafted animals.

Differential actions of the proneural genes encoding Mash1 and neurogenins in Nurr1-induced dopamine neuron differentiation

The steroid receptor-type transcription factor Nurr1 has a crucial role in the development of the mesencephalic dopamine (DA) neurons. Although ectopic expression of Nurr1 in cultured neural precursor cells is sufficient in establishing the DA phenotype, Nurr1-induced DA cells are morphologically and functionally immature, suggesting the necessity of additional factor(s) for full neuronal differentiation. In this study, we demonstrate that neurogenic basic helix-loop-helix (bHLH) factors Mash1, neurogenins (Ngns) and NeuroD play contrasting roles in Nurr1-induced DA neuronal differentiation. Mash1, but not Ngn2, spatially and temporally colocalized with aldehyde dehydrogenase 2 (AHD2), a specific midbrain DA neuronal progenitor marker, in the early embryonic ventral mesencephalon. Forced expression of Mash1 caused immature Nurr1-induced DA cells to differentiate into mature and functional DA neurons as judged by electrophysiological characteristics, release of DA, and expression of presynaptic DA neuronal markers. By contrast, atonal-related bHLHs, represented by Ngn1, Ngn2 and NeuroD, repressed Nurr1-induced expression of DA neuronal markers. Domain-swapping experiments with Mash1 and NeuroD indicated that the helix-loop-helix domain, responsible for mediating dimerization of bHLH transcription factors, imparts the distinct effect. Finally, transient co-transfection of the atonal-related bHLHs with Nurr1 resulted in an E-box-independent repression of Nurr1-induced transcriptional activation of a reporter containing Nurr1-binding element (NL3) as well as a reporter driven by the native tyrosine hydroxylase gene promoter. Taken together, these findings suggest that Mash1 contributes to the generation of DA neurons in cooperation with Nurr1 in the developing midbrain whereas atonal-related bHLH genes inhibit the process.

In vitro and in vivo analyses of human embryonic stem cell-derived dopamine neurons

Human embryonic stem (hES) cells, due to their capacity of multipotency and self-renewal, may serve as a valuable experimental tool for human developmental biology and may provide an unlimited cell source for cell replacement therapy. The purpose of this study was to assess the developmental potential of hES cells to replace the selectively lost midbrain dopamine (DA) neurons in Parkinson's disease. Here, we report the development of an in vitro differentiation protocol to derive an enriched population of midbrain DA neurons from hES cells. Neural induction of hES cells co-cultured with stromal cells, followed by expansion of the resulting neural precursor cells, efficiently generated DA neurons with concomitant expression of transcriptional factors related to midbrain DA development, such as Pax2, En1 (Engrailed-1), Nurr1, and Lmx1b. Using our procedure, the majority of differentiated hES cells (> 95%) contained neuronal or neural precursor markers and a high percentage (> 40%) of TuJ1+ neurons was tyrosine hydroxylase (TH)+, while none of them expressed the undifferentiated ES cell marker, Oct 3/4. Furthermore, hES cell-derived DA neurons demonstrated functionality in vitro, releasing DA in response to KCl-induced depolarization and reuptake of DA. Finally, transplantation of hES-derived DA neurons into the striatum of hemi-parkinsonian rats failed to result in improvement of their behavioral deficits as determined by amphetamine-induced rotation and step-adjustment. Immunohistochemical analyses of grafted brains revealed that abundant hES-derived cells (human nuclei+ cells) survived in the grafts, but none of them were TH+. Therefore, unlike those from mouse ES cells, hES cell-derived DA neurons either do not survive or their DA phenotype is unstable when grafted into rodent brains.

Enhanced in vitro midbrain dopamine neuron differentiation, dopaminergic function, neurite outgrowth, and 1-methyl-4-phenylpyridium resistance in mouse embryonic stem cells overexpressing Bcl-XL

Embryonic stem (ES) cells provide a potentially unlimited source of specialized cells for regenerative medicine. The ease of inducing stable genetic modifications in ES cells allows for in vitro manipulations to enhance differentiation into specific cell types and to optimize in vivo function of differentiated progeny in animal models of disease. We have generated mouse ES cells that constitutively express Bcl-XL, an antiapoptotic protein of Bcl-2 family. In vitro differentiation of Bcl-XL overexpressing ES (Bcl-ES) cells resulted in higher expression of genes related to midbrain dopamine (DA) neuron development and increased the number of ES-derived neurons expressing midbrain DA markers compared with differentiation of wild-type ES cells. Moreover, DA neurons derived from Bcl-ES cells were less susceptible to 1-methyl-4-phenylpyridium, a neurotoxin for DA neurons. On transplantation into parkinsonian rats, the Bcl-ES-derived DA neurons exhibited more extensive fiber outgrowth and led to a more pronounced reversal of behavioral symptoms than wild-type ES-derived DA neurons. These data suggest a role for Bcl-XL during in vitro midbrain DA neuron differentiation and provide an improved system for cell transplantation in a preclinical animal model of Parkinson's disease.

Urinary N-acetyl-beta-D-glucosaminidase and malondialdehyde as a markers of renal damage in burned patients

This study was aimed to evaluate renal dysfunction during three weeks after the burn injuries in 12 patients admitted to the Hallym University Hankang Medical Center with flame burn injuries (total body surface area, 20-40%). Parameters assessed included 24-hr urine volume, blood urea nitrogen, serum creatinine, creatinine clearance, total urinary protein, urinary microalbumin, 24-hr urinary N-acetyl-beta-D-glucosaminidase (NAG) activity, and urinary malondialdehyde (MDA). Statistical analysis was performed using repeated measures ANOVA test. The 24-hr urine volume, creatinine clearance, and urinary protein significantly increased on day 3 post-burn and fell thereafter. The urine microalbumin excretion showed two peak levels on day 0 post-burn and day 3. The 24-hr urinary NAG activity significantly increased to its maximal level on day 7 post-burn and gradually fell thereafter. The urinary MDA progressively increased during 3 weeks after the burn injury. Despite recovery of general renal function through an intensive care of burn injury, renal tubular damage and lipid peroxidation of the renal tissue suggested to persist during three weeks after the burn. Therefore, a close monitoring and intensive management of renal dysfunction is necessary to prevent burn-induced acute renal failure as well as to lower mortality in patients with major burns.

Modification of cardiovascular responses to adenosine A1 receptor stimulation in the posterior hypothalamus of anaesthetized rats by cAMP and by GABA(B) receptor blockade

1 Injection of N(6)-cyclohexyladenosine (CHA; 1, 5 and 10 nmol), an adenosine A1 receptor agonist, into the posterior hypothalamus of rats produced a dose-dependent decrease in blood pressure (BP) and heart rate (HR). 2 Pretreatment with 8-cyclopentyl-1,3-dimethylxanthine (CPDX; 50 nmol), an adenosine A1 receptor antagonist, blocked the depressor and bradycardic effects of CHA (10 nmol). 3 Pretreatment with 8-bromo-cyclic adenosine monophosphate (AMP) (10 nmol), a cAMP analogue, attenuated the depressor and bradycardic effect of CHA (10 nmol); 8-bromo-cyclic guanosine monophosphate (GMP) (10 nmol), a cGMP analogue, did not modify those effects of CHA. 4 In addition, pretreatment with 5-aminovaleric acid (25 nmol), a gamma-aminobutyric acid (GABA)(B) receptor antagonist, attenuated the depressor and bradycardic effects of CHA (10 nmol). 5 These results suggest that adenosine A1 receptors in the posterior hypothalamus have an inhibitory role in the central cardiovascular regulation and that these vasodepressive and bradycardic actions are modified by raised cAMP and by GABA(B) receptor inhibition.

Data mining applications in the context of casemix

In October 1999, the Singapore Government introduced casemix-based funding to public hospitals. The casemix approach to health care funding is expected to yield significant benefits, including equity and rationality in financing health care, the use of comparative casemix data for quality improvement activities, and the provision of information that enables hospitals to understand their cost behaviour and reinforces the drive for more cost-efficient services. However, there is some concern about the "quicker and sicker" syndrome (that is, the rapid discharge of patients with little regard for the quality of outcome). As it is likely that consequences of premature discharges will be reflected in the readmission data, an analysis of possible systematic patterns in readmission data can provide useful insight into the "quicker and sicker" syndrome. This paper explores potential data mining applications in the context of casemix by using readmission data as an illustration. In particular, it illustrates how data mining can be used to better understand readmission data and to detect systematic patterns, if any. From a technical perspective, data mining (which is capable of analysing complex non-linear and interaction relationships) supplements and complements traditional statistical methods in data analysis. From an applications perspective, data mining provides the technology and methodology to analyse mass volume of data to detect hidden patterns in data. Using readmission data as an illustrative data mining application, this paper explores potential data mining applications in the general casemix context.

Mediation of the cardiovascular response to spinal gamma-aminobutyric acid(B) receptor stimulation by adenosine A(1) receptors in anesthetized rats

Cardiovascular inhibitory effects induced by intrathecal (i.t.) administration of adenosine A(1) receptor agonist and its modulation by gamma-aminobutyric acid(B) (GABA(B)) receptor was suggested by our previous report. In this experiment, we examined the mediation of cardiovascular effects of GABA(B) receptor stimulation by adenosine A(1) and A(2) in the spinal cord. I.t. administration of GABA(B) receptor agonist, baclofen (30, 60 and 100 nmol) produced a dose dependent decrease of blood pressure and heart rate. Pretreatment with adenosine A(1) receptor antagonist, 8-cyclopentyl-1,3-dimethylxanthine (50 nmol), attenuated the depressor and bradycardiac effects of baclofen (100 nmol), but not with adenosine A(2) receptor antagonist, 3, 7-dimethyl-1-propargylxanthine (25 nmol). These results suggest that GABA(B) receptors in the spinal cord play an inhibitory role in the central cardiovascular regulation and that the depressor and bradycardiac actions are mediated by adenosine A(1) receptors.

Single amino acid of g(alpha16) (Ala(228)) is responsible for the ability of chemoattractant C5a receptor to induce G(alpha16)-mediated inositol phosphate release

Our previous study suggested that the region encompassing residues 220-240 on G(alpha16) is important in coupling with C5a receptor (Lee et al. (1995) Mol. Pharmacol. 47, 218-223). When aligned sequences are compared in the residue 220-240 segment of G(alpha16), there is a block of eight amino acids extending from residue 227 to residue 234 (227-Ile-Ala-Leu-Ile-Tyr-Leu-Ala-Ser-234) in G(alpha16) that is replaced by a heterologous block extending from amino acid residue 224 to residue 231 (224-Thr-Ser-Ile-Met-Phe-Leu-Val-Ala-231) in G(alpha11). In order to identify the specific amino acid residue necessary for coupling to C5a receptor within the extension of eight amino acids in G(alpha16), a series of chimeric G(alpha11)/G(alpha16) cDNA constructs and mutant G(alpha16) cDNAs were expressed. Then the ability of chimeras and mutant proteins to mediate C5a-induced release of inositol phosphate in transfected Cos-7 cells was tested. The results show that single amino acid Ala(228) is responsible for conferring about 40-50% of the activity of G(alpha16) induced by C5a receptor stimulation.

Modification of cardiovascular response of adenosine A2 receptor agonist by adenylate cyclase in the spinal cord of rats

This study was performed to investigate the influence of spinal adenosine A2 receptors on the central regulation of blood pressure (BP) and heart rate (HR), and to define whether its mechanism is mediated by adenylate cyclase or guanylate cyclase. Intrathecal (i.t.) administration of drugs at the thoracic level were performed in anesthetized, artificially ventilated male Sprague-Dawley rats. Injection (i.t.) of adenosine A2 receptor agonist, 5'-(N-cyclopropyl)-carboxamidoadenosine (CPCA; 1, 2 and 3 nmol) produced a dose dependent decrease of BP and HR. Pretreatment with adenylate cyclase inhibitor, MDL-12,330, attenuated the depressor and bradycardiac effects of CPCA (2 nmol), but not with guanylate cyclase inhibitor, LY-83,583. These results suggest that adenosine A2 receptor in the spinal cord plays an inhibitory role in the central cardiovascular regulation and that the depressor and bradycardiac actions are mediated by adenylate cyclase.

Modification of cardiovascular responses to spinal GABA(B) receptor stimulation by cAMP and by K(ATP) channel blockade in anaesthetized rats

1. Intrathecal (i.t.) injection of baclofen (30, 60 and 100 nmol), a GABA(B) receptor agonist, produced a dose-dependent decrease in blood pressure (BP) and heart rate (HR). 2. Pretreatment with 5-aminovaleric acid (50 nmol), a GABA(B) receptor antagonist, blocked the depressor and bradycardic effects of baclofen (100 nmol). 3. Pretreatment with 8-bromo-cAMP (10 nmol), a cAMP analogue, attenuated the depressor and bradycardic effects of baclofen (100 nmol), but not with 8-bromo-cGMP (10 nmol), a cGMP analogue. 4. In addition, pretreatment with glipizide (20 nmol), an ATP-sensitive K+ channel (K(ATP)) blocker, attenuated the depressor and bradycardic effects of baclofen (100 nmol). These results suggest that GABA(B) receptors in the spinal cord have an inhibitory role in the central cardiovascular regulation and that these depressive and bradycardic actions are modified by cAMP and by K(ATP) channel blockade.

Differential coupling of G alpha q family of G-protein to muscarinic M1 receptor and neurokinin-2 receptor

The ligand binding signals to a wide variety of seven transmembrane cell surface receptors are transduced into intracellular signals through heterotrimeric G-proteins. Recently, there have been reports which show diverse coupling patterns of ligand-activated receptors to the members of Gq family alpha subunits. In order to shed some light on these complex signal processing networks, interactions between G alpha q family of G protein and neurokinin-2 receptor as well as muscarinic M1 receptor, which are considered to be new therapeutic targets in asthma, were studied. Using washed membranes from Cos-7 cells co-transfected with different G alpha q and receptor cDNAs, the receptors were stimulated with various concentrations of carbachol and neurokinin A and the agonist-dependent release of [3H]inositol phosphates through phospholipase C beta-1 activation was measured. Differential coupling of G alpha q family of G-protein to muscarinic M1 receptor and neurokinin-2 receptor was observed. The neurokinin-2 receptor shows a ligand-mediated response in membranes co-transfected with G alpha q, G alpha 11 and G alpha 14 but not G alpha 16 and the ability of the muscarinic M1 receptor to activate phospholipase C through G alpha q/11 but not G alpha 14 and G alpha 16 was demonstrated. Clearly G alpha q/11 can couple M1 and neurokinin-2 receptor to activate phospholipase C. But, there are differences in the relative coupling of the G alpha 14 and G alpha 16 subunits to these receptors.

Mediation of the cardiovascular response of adenosine A1 receptor through a GABA(B) receptor in the spinal cord of the rat

Cardiovascular inhibitory effects induced by intrathecal (i.t.) administration of adenosine A1 receptor agonist and its modulation by cyclic AMP was suggested by our previous report. In this experiment, we examined the mediation of cardiovascular effects of adenosine A1 receptor by gamma-aminobutyric acid receptors A and B [GABA(A) and GABA(B)] in the spinal cord. I.t. administration of 10 nmol of N6-cyclohexyladenosine (CHA), an adenosine A1 receptor agonist, and pretreatment with bicuculline (10 nmol, i.t), a GABA(A) receptor antagonist, and 5-aminovaleric acid (50 nmol, i.t.), a GABA(B) receptor antagonist, prior to injection of CHA were performed in anesthetized, artificially ventilated Sprague-Dawley rats. I.t. injection of 50 nmol of 5-aminovaleric acid significantly attenuated the inhibitory cardiovascular effects of CHA but 10 nmol of bicuculline did not alter CHA-induced cardiovascular actions. It is suggested that cardiovascular responses of adenosine A1 receptor is mediated by GABA(B) receptor in the spinal cord.

Modification of cardiovascular response of adenosine A1 receptor agonist by cyclic AMP in the spinal cord of the rats

This study was performed to investigate the influence of the spinal adenosine A1 receptors on the central regulation of blood pressure (BP) and heart rate (HR), and to define whether its mechanism is mediated by cyclic AMP (cAMP) or cyclic GMP (cGMP). Intrathecal (i.t.) administration of drugs at the thoracic level were performed in anesthetized, artificially ventilated male Sprague-Dawley rats. Injection (i.t.) of adenosine A1 receptor agonist, N6-cyclohexyladenosine (CHA; 1, 5 and 10 nmol) produced dose dependent decrease of BP and HR. Pretreatment with a cAMP analogue, 8-bromo-cAMP, attenuated the depressor and bradycardiac effects of CHA (10 nmol), but not with cGMP analogue, 8-bromo-cGMP. These results suggest that adenosine A1 receptor in the spinal cord plays an inhibitory role in the central cardiovascular regulation and that this depressor and bradycardiac actions are mediated by cAMP.

Intrathecal administration of sodium nitroprusside, a nitric oxide donor, increases blood pressure in anesthetized rats

The present study was performed to investigate the role of spinal nitric oxide (NO) in the central regulation of blood pressure (BP). Experiments were carried out in anesthetized artificially ventilated male Wistar rats. Intrathecal (i.t.) administration of drugs was made at the thoracic spinal level. I.t. injection of a NO donor, sodium nitroprusside (SNP; 1, 5, and 15 nmol) increased BP dose-dependently. Intrathecal pretreatment of methylene blue (200 nmol) significantly attenuated the pressor response evoked by SNP (15 nmol, i.t.). I.t. administration of nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester (100 and 1000 nmol), caused decreases in BP. These results suggest that NO plays a tonic excitatory role in the central regulation of BP in the rat spinal cord.

Predictive classified vector quantization

A vector quantization scheme based on the classified vector quantization (CVQ) concept, called predictive classified vector quantization (PCVQ), is presented. Unlike CVQ where the classification information has to be transmitted, PCVQ predicts it, thus saving valuable bit rate. Two classifiers, one operating in the Hadamard domain and the other in the spatial domain, were designed and tested. The classification information was predicted in the spatial domain. The PCVQ schemes achieved bit rate reductions over the CVQ ranging from 20 to 32% for two commonly used color test images while maintaining the same acceptable image quality. Bit rates of 0.70-0.93 bits per pixel (bpp) were obtained depending on the image and PCVQ scheme used.