TIF1gamma, a novel member of the transcriptional intermediary factor 1 family

The Anaphase-Promoting Complex/Cyclosome (APC/C) is an ubiquitin ligase that functions during mitosis. Here we identify the transcriptional regulator, Transcriptional Intermediary Factor 1γ, TIF1γ as an APC/C-interacting protein that regulates APC/C function. TIF1γ is not a substrate for APC/C-dependent ubiquitylation but instead, associates specifically with the APC/C holoenzyme and Cdc20 to affect APC/C activity and progression through mitosis. RNA interference studies indicate that TIF1γ knockdown results in a specific reduction in APC/C ubiquitin ligase activity, the stabilization of APC/C substrates, and an increase in the time taken for cells to progress through mitosis from nuclear envelope breakdown (NEBD) to anaphase. TIF1γ knockdown cells are also characterized by the inappropriate presence of cyclin A at metaphase, and an increase in the number of cells that fail to undergo metaphase-to-anaphase transition. Expression of a siRNA-resistant TIF1γ species relieves the mitotic phenotype imposed by TIF1γ knockdown and allows for mitotic progression. Binding studies indicate that TIF1γ is also a component of the APC/C-Mitotic Checkpoint Complex (MCC), but is not required for MCC dissociation from the APC/C once the Spindle Assembly Checkpoint (SAC) is satisfied. TIF1γ inactivation also results in chromosome misalignment at metaphase, and SAC activation; inactivation of the SAC relieves the mitotic block imposed by TIF1γ knockdown. Together these data define novel functions for TIF1γ during mitosis and suggest that a reduction in APC/C ubiquitin ligase activity promotes SAC activation.

TIF1gamma, a novel member of the transcriptional intermediary factor 1 family

We report the cloning and characterization of a novel member of the Transcriptional Intermediary Factor 1 (TIF1) gene family, human TIF1gamma. Similar to TIF1alpha and TIF1beta, the structure of TIF1beta is characterized by multiple domains: RING finger, B boxes, Coiled coil, PHD/TTC, and bromodomain. Although structurally related to TIF1alpha and TIF1beta, TIF1gamma presents several functional differences. In contrast to TIF1alpha, but like TIF1beta, TIF1 does not interact with nuclear receptors in yeast two-hybrid or GST pull-down assays and does not interfere with retinoic acid response in transfected mammalian cells. Whereas TIF1alpha and TIF1beta were previously found to interact with the KRAB silencing domain of KOX1 and with the HP1alpha, MODI (HP1beta) and MOD2 (HP1gamma) heterochromatinic proteins, suggesting that they may participate in a complex involved in heterochromatin-induced gene repression, TIF1gamma does not interact with either the KRAB domain of KOX1 or the HP1 proteins. Nevertheless, TIF1gamma, like TIF1alpha and TIF1beta, exhibits a strong silencing activity when tethered to a promoter. Since deletion of a novel motif unique to the three TIF1 proteins, called TIF1 signature sequence (TSS), abrogates transcriptional repression by TIF1gamma, this motif likely participates in TIF1 dependent repression.

[Application of supercritical fluid extraction (SFE) on environmental analysis]

In this paper, publications from 1993 are classified according to the type of matrix from which the environmental analytes are extracted. Although the most applications of SFE are used for the solid, some analysts have concerned with aqueous and gaseous media. Various aspects of investigation of environmental potential carcinogen, such as, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, dioxins, pesticides, phenols and other hazardous and toxic pollutants in environmental samples have been reviewed with 55 references. The coupled techniques of SFE have also been introduced in this paper.

A unified reconstruction framework for both parallel-beam and variable focal-length fan-beam collimators by a Cormack-type inversion of exponential radon transform

A variety of inversions of exponential Radon transform has been derived based on the circular harmonic transform in Fourier space by several research groups. However, these inversions cannot be directly applied to deal with the reconstruction for fan-beam or variable-focal-length fan-beam collimator geometries in single photon emission computed tomography (SPECT). In this paper, we derived a Cormack-type inversion of the exponential Radon transform by employing the circular harmonic transform directly in the projection space and the image space instead of the Fourier space. Thus, a unified reconstruction framework is established for parallel-, fan-, and variable-focal-length fan-beam collimator geometries. Compared to many existing algorithms, the presented one greatly mitigates the difficulty of image reconstruction due to the complicated collimator geometry and significantly reduces the computational burden of the special functions, such as Chebyshev or Bessel functions. By the well-established fast-Fourier transform (FFT), our algorithm is very efficient, as demonstrated by several numerical simulations.

[The protective role of heat shock gene expression on hydrogen peroxide induced pulmonary alveolar macrophages]

The aim of this study is to determine whether heat-induced heat shock gene expression in rat pulmonary alveolar macrophages (PAMs) would protect PAMs against hydrogen peroxide (H2O2)-mediated cell killing. In response to sublethal heat shock at 42 degrees C for 2 h, the cells synthesized heat shock protein 70 kD (HSP70) and other different molecular weight heat shock proteins, which were detected with gel electrophoresis after [35S]-methionin labeling cellular protein and Western blotting analysis in PAMs. Northern blot analysis showed the induction of HSP70 mRNA with heat shock treatment. Futhermore, with heat shock, there was a significant increment of survival cells after H2O2 (1,2,3 mmol.L-1, 45 min) exposure. This increase was blocked both by Cycloheximide and by Actinomycin D, and was associated with inhibition of synthesis of HSP70 protein and transcription of HSP70 mRNA. These results strongly suggest that expression of heat shock gene (especially HSP70 gene) plays an important role in the intracelluar mechanism of cytoprotection against H2O2 in rat PAMs.

A harmonic decomposition reconstruction algorithm for spatially varying focal length collimators

Spatially varying focal length fan-beam collimators can be used in single photon emission computed tomography to improve detection efficiency and to reduce reconstruction artifacts resulting from the truncation of projection data. It has been proven that there exists no convolution backprojection algorithm for this type of collimator, so a complicated interpolation between two nonparallel projection rays is necessary for existing algorithms. The interpolation may generate blurring and artifacts in the reconstructed images. Based on a harmonic decomposition technique and the translation property of Fourier series, a semifrequency resampling technique is proposed to avoid the above mentioned interpolations. By this technique, the harmonic decomposition of projection data for spatially varying focal length fan-beam collimators has the same form as that for parallel-beam collimators in the semifrequency domain (Fourier transform with respect to angular variables only). An alternative version of the inverse Cormack transform is then proposed to reconstruct the images. The derived reconstruction algorithm was implemented in a Pentium II/266 PC computer. Numerical simulations demonstrated its efficiency (3 s for 128 x 128 reconstruction arrays) and its robust performance (compared to the existing algorithms).

TIF1alpha: a possible link between KRAB zinc finger proteins and nuclear receptors

Ligand-induced gene activation by nuclear receptors (NRs) is thought to be mediated by transcriptional intermediary factors (TIFs), that interact with their ligand-dependent AF-2 activating domain. Included in the group of the putative AF-2 TIFs identified so far is TIF1alpha, a member of a new family of proteins which contains an N-terminal RBCC (RING finger-B boxes-coiled coil) motif and a C-terminal bromodomain preceded by a PHD finger. In addition to these conserved domains present in a number of transcriptional regulatory proteins, TIF1alpha was found to contain several protein-protein interaction sites. Of these, one specifically interacts with NRs bound to their agonistic ligand and not with NR mutants that are defective in the AF-2 activity. Immediately adjacent to this 'NR box', TIF1alpha contains an interaction site for members of the chromatin organization modifier (chromo) family, HP1alpha and MOD1, which both are heterochromatinic proteins. Finally, TIF1alpha also has a binding site for KRAB silencing domains of C2H2 zinc finger proteins. TIF1beta, another member of the TIF1 gene family, has some interacting partners in common with TIF1alpha. TIF1beta can interact with HP1alpha, MOD1 and KRAB domains, but apparently not with NRs. Both TIF1alpha and TIF1beta repress transcription when fused to a DNA binding domain in transiently transfected mammalian cells. A model discussing the potential function(s) of TIF1s in the control of transcription at the level of the chromatin template will be presented.

Effect of artemether on hexokinase, glucose phosphate isomerase and phosphofructokinase of Schistosoma japonicum harbored in mice

AIM

To study the effect of artemether (Art) on hexokinase (HK), glucose phosphate isomerase (GPI) and phosphofructokinase (PFK) of Schistosoma japonicum.

METHODS

Mice infected with schistosome cercariae for 4-5 wk were treated ig with Art 100 or 300 mg.kg-1 and killed 24 h or 48 h after medication for collection of schistosomes. The activities of HK, GPI and PFK of the worms were determined by measuring the formation of NADPH or consumption of NADH.

RESULTS

Worms from the infected mice treated ig with Art at a single dose of 300 mg.kg-1 the inhibition rates of HK activity of female and male worms were 33.7% and 13.7%, respectively 24 h after administration. Similar results were seen in GPI activity, but 48 h after medication, the inhibition rate of GPI increased to 46.2% (female) and 32.9% (male), respectively. Worms from mice treated with Art 100 or 300 mg.kg-1, the inhibitory effect on PFK in female worms was found much higher than that of male worms the inhibition rates of PFK were 64.9%-71.0% in female worms and 16.3%-54.2% in male worms, respectively at 24 h and 48 h after treatment.

CONCLUSION

The results suggest that in the glycolytic pathway of schistosome PFK might be one of the targets attacked by Art.

Benefits of angular expression to reconstruction algorithms for collimators with spatially varying focal lengths

Fan-beam collimators with spatially varying focal lengths are used in single photon emission computed tomography (SPECT) to improve the imaging sensitivity and to reduce the reconstruction artifacts resulting from the truncation of projection data. An angular representation of the detector coordinates for the projection data is adopted to investigate several aspects of the reconstruction problem for this type of collimation. A rebinning reconstruction algorithm is derived. We prove a conjecture posed by Zeng and Gullberg and obtain a simplified form of their backprojection filtering algorithm. Some computer simulations are presented to investigate the performance of the rebinning algorithm.

Advances in the treatment and prophylaxis of Pneumocystis carinii pneumonia

Pneumocystis carinii pneumonia (PCP) is the most common illness associated with the acquired immunodeficiency syndrome (AIDS) in the United States and also occurs in immunocompromised persons not infected with the human immunodeficiency virus.. Several advances have taken place in the treatment and prophylaxis of PCP, with most clinical trials conducted in patients with AIDS. Treatment of choice is trimethoprim-sulfamethoxazole (TMP-SMX). Desensitization regimens are available for those who have a fever or rash associated with the agent. Patients with severe PCP who cannot tolerate TMP-SMX may be treated successfully with pentamidine or trimetrexate. Those with mild to moderate disease may receive dapsone-trimethoprim, clindamycin-primaquine, or atovaquone if they cannot take TMP-SMX. Adjunctive therapy with corticosteroids improves the outcome in patients with AIDS and severe PCP.

Endothelial-mediated dilations of rat middle cerebral arteries by ATP and ADP

The hypothesis that ATP and ADP produce dilations of rat middle cerebral arteries (MCAs) by different mechanisms was tested. Vessel diameters were measured from pressurized, perfused MCAs after application of different agonists. The luminal administration of ATP and ADP elicited concentration-dependent dilations (35% maximum). Removal of endothelium abolished the dilation to intraluminal ATP and attenuated the dilation to intraluminal ADP. The dilations to ATP were abolished with N omega-nitro-L-arginine methyl ester (L-NAME; 10 microM), a nitric oxide synthase inhibitor, at ATP concentrations of 1 microM and below. However, at concentrations of 10 microM ATP and above, L-NAME had no effect on the response. The dilations to ADP were attenuated by L-NAME to the same degree as removal of endothelium. The mechanism for dilation by ATP was identical to that of UTP, a selective P2u purinoceptor agonist. The mechanism of dilation by ADP was similar to that of 2-methylthioadenosine 5'-triphosphate, a selective P2y purinoceptor agonist. We conclude that ATP and ADP elicit dilations of rat MCA by different mechanisms. ATP and ADP likely stimulate P2u and P2y purinoceptors, respectively.

Preconditioning during warm blood cardioplegia

OBJECTIVE

Preconditioning describes the cardioprotective effects of multiple brief episodes of warm ischemia. The purpose of the study was to determine whether warm ischemia, during the intermittent delivery of warm blood cardioplegia, would induce preconditioning during cardioplegia arrest.

METHODS

Dogs, 15, were randomized to a preconditioning protocol or to serve as controls. The control group received 60 min of continuous warm blood cardioplegia (WBC) followed by 30 min of warm arrested ischemia. The preconditioned group were arrested with WBC and then underwent three consecutive cycles consisting of 10 min of warm ischemia followed by 10 min of reperfusion. Reperfusion was provided by a continuous infusion of WBC. The preconditioning protocol was followed by 30 min of warm arrested ischemia. Myocardial functional recovery was assessed before cardiopulmonary bypass and cardioplegia arrest and again 30, 60 and 90 min after the arrest. Pressure-volume loops were used to measure the maximum elastance of the left ventricle (Emax), diastolic compliance, and used to calculate preload recruitable stroke work area.

RESULTS

Myocardial functional recovery was better preserved after 30 min of warm arrested ischemia in those animals that had been preconditioned.

CONCLUSION

Preconditioning may be induced when warm blood cardioplegia is delivered intermittently during cardioplegia arrest.

Altered expression of insulin-like growth factor I and its receptor during multistage carcinogenesis in mouse skin

We examined the possible role of insulin-like growth factor-I (IGF-I) and IGF-I receptor (IGF-Ir) during multistage carcinogenesis in mouse skin. For this purpose, the expression of both IGF-I and IGF-Ir was investigated in mouse skin during tumor promoter treatment and in primary papillomas and squamous cell carcinomas (SCCs) obtained from SENCAR mice treated with standard initiation-promotion regimens. IGF-I transcripts were not detectable or only weakly detectable in normal SENCAR mouse epidermis by northern or reverse transcription (RT)-polymerase chain reaction (PCR) analysis, respectively, whereas IGF-I transcripts (primarily a 7.0-kb transcript) were readily detected in RNA preparations from the dermis by both northern blot analysis and RT-PCR analysis. In contrast, IGF-Ir transcripts were observed in RNA samples from both epidermis and dermis of control SENCAR mice. Single and multiple topical treatments with 3.4 nmol of 12-O-tetradecanoylphorbol-13-acetate (TPA) had no effect on dermal or epidermal IGF-I and IGF-Ir mRNA levels. In contrast, the levels of IGF-I transcripts were elevated (2.5- to 15-fold) in a significant number of mouse skin tumors (71% of all tumors examined). Transcripts of 7.0, 2.5, and 1.3 kb were more consistently overexpressed in skin tumors compared with epidermis, whereas the two smaller transcripts were most consistently overexpressed compared with the dermis. The levels of an 11.0-kb IGF-Ir transcript were also elevated (2.5- to 8-fold) in some papillomas (20%) and SCCs (55%), but the percentage of tumors exhibiting this property (32% of all tumors examined) was lower than the percentage overexpressing IGF-I. These data suggest that altered expression of IGF-I and IGF-Ir may play a role in multistage carcinogenesis in the mouse skin model. The inability of TPA to induce elevated IGF-I or IGF-Ir expression suggests that these changes in skin tumors are coincident with tumor formation and not a direct result of altered epidermal proliferation per se. Altered expression of IGF-I in a high percentage of papillomas may indicate that IGF-I has an important role in the development of autonomous growth in these tumors. The higher percentage of SCCs with altered levels of IGF-Ir mRNA may indicate a role for these changes in the later stages (i.e., tumor progression) of carcinogenesis in this model system.

[Interrelationship between endothelin and glomerular mesangial cells]

The interrelationship between endothelin (ET), endothelin receptors (ET-R) and glomerular mesangial cells (MC) was investigated by MC culture, RT-PCR, Northern blot hybridization, DNA cytometry and immunohistochemistry methods. The results showed that in MC, there existed the expression of ET mRNA and also the expression of 2 subsets ETA mRNA and ETB mRNA. ET mRNA peptide is synthesized in MC. ET mRNA induced significant MC contraction and stimulated MC division and proliferation. The results suggest that MC are special cells with the capacity of producing ET and are also the target cells for ET. It is possible that ET influence glomerular filtration area and rate by inducing MC contraction and cause also MC proliferation and glomerular sclerosis.

Characterization of neuropeptide Y receptors mediating contraction, potentiation and inhibition of relaxation

In addition to its direct vasoconstrictive effect, neuropeptide Y (NPY) potentiates noradrenaline-(NA) induced contraction and inhibits acetylcholine-(ACh) induced relaxation: The aim of the present study was to elucidate the NPY receptor subtypes responsible for mediating these three responses. NPY, peptide YY (PYY) and pro34NPY (a NPY Y1 receptor agonist) induced equipotent and equally strong concentration-dependent contractions of guinea pig basilar arteries. NPY13-36 (a NPY Y2 receptor agonist), however, caused only weak contraction with significantly lower potency. The NPY-induced contraction was significantly inhibited by the selective NPY Y1 receptor antagonist BIBP3226 (1 microM). NPY, PYY and pro34NPY but not NPY13-36 significantly potentiated the NA-induced contraction in guinea pig mesenteric arteries. The potentiation was significantly inhibited by BIBP3226 (1 microM). In precontracted guinea pig basilar arteries, ACh induced a concentration-dependent relaxation which was significantly inhibited by NPY, PYY and NPY13-36 but not by pro34NPY. BIBP3226 had no significant effect on the NPY-induced inhibition of the relaxation. These results suggests that the NPY Y1 receptors mediate the direct contraction and the potentiation of the NA-induced contraction but not the inhibition of the ACh-induced relaxation. This effect seems to be mediated by another NPY receptor subtype, presumably by the Y2 receptor, as judged from the agonist potency order.

Responses of tumor cell pseudopod protrusion to changes in medium osmolality

The potential involvement of osmotically generated force in protrusion of tumor cell pseudopods was examined during a micropipette assay. Experiments were performed on single A2058 melanoma cells activated by a micropipette filled with soluble type IV collagen. Previous observations suggested that tumor cell pseudopod protrusion induced by type IV collagen took place in distinct, separable phases: an initial bleb (first phase) caused by localized Ca2+-activated actin filament severing resulting in an osmotic flux followed by an extension with an irregular shape (second phase) which required G protein-mediated actin polymerization (Dong et al., 1994, Microvasc. Res., 47:55-67). Presently we studied cell pseudopod protrusion in response to the changes in chemoattractant osmolality. Reduction of attractant osmolality by 20-25% from its baseline value (297 mmol/ kg) resulted in an increase in pseudopod length by 50% apparent in the initial phase. Increases in attractant osmolality by 25-30% from the baseline value arrested pseudopod protrusion significantly during both initial and later phases. Using a dual-pipette method, such osmotic influence on the cell pseudopod protrusion was shown to be only a local effect in a small region where the cell surface was stimulated by the micropipette. While forces derived from actin polymerization and osmotic pressure have been proposed to cause protrusion in general, our results suggested that osmotically generated force is more apparent in the initial phase of the pseudopod formation.

Reduced tumorigenicity of metastatic human lung cancer cell subline (PGCL3) transfected with hRAR beta gene

The recombinant PSG5-RAR beta plasmid and the G418-resistant PSV2 neo plasmid (10.1) were cotransfected into PGCL3 cells by coprecipitation with calcium phosphate. The transfectants CR3 and CR4, which expressed the RAR beta gene, were identified by Northern blot hybridization. The results showed that the in vitro growth and invasion of CR3 and CR4 were dramatically reduced compared to the control-transfected cell (CSV1). Furthermore, the colony-forming abilities in soft agar and the tumorigenicity in nude mice of CR3 and CR4 were abrogated. Our results suggests that RAR beta functions not only as a receptor mediating the RA action, but also as a suppressor in lung tumorigenesis.

alpha-Trinositol: a functional (non-receptor) neuropeptide Y antagonist in vasculature

Neuropeptide Y is a sympathetic co-neurotransmitter released with noradrenaline upon sympathetic nerve stimulation. This study describes the ability of a synthetic inositol phosphate, alpha-trinositol(D-myo-inositol 1,2,6-triphosphate; PP 56) to antagonize vasoconstrictor responses to neuropeptide Y in-vitro as well as in-vivo. In human and guinea-pig isolated arteries alpha-trinositol potently (10 nM to 1 microM extracellular concentration) suppressed the constriction evoked by neuropeptide Y alone, the potentiation by neuropeptide Y of noradrenaline-evoked constriction, and the neuropeptide Y-induced inhibition of relaxation. Moreover, in the pithed (areflexive) rat, a non-adrenergic portion of the pressor response to preganglionic sympathetic nerve stimulation was sensitive to alpha-trinositol. As studied in the recently cloned human (vascular-type) Y1 receptor, the action of alpha-trinositol does not occur through antagonism at the neuropeptide Y recognition site nor does it induce allosteric changes of this receptor. However, we found alpha-trinositol to inhibit the rise in intracellular Ca2+ as well as inositol triphosphate concentrations induced by neuropeptide Y. It is, therefore, proposed that alpha-trinositol represents a non-receptor, but yet selective antagonist of neuropeptide Y in vasculature, opening up the possibility to investigate involvement of neuropeptide Y in sympathetic blood pressure control and in cardiovascular disorders.

Peptidergic innervation of guinea-pig brain vessels: comparison with immunohistochemistry and in vitro pharmacology in rostrally and caudally located arteries

The peptidergic innervation of the guinea-pig basilar artery and the posterior, middle and anterior cerebral arteries were studied by means of immunohistochemical and image analysis techniques using whole mount preparations. An in vitro pharmacological study was performed to correlate the distribution of peptide-containing nerves and the action of neuropeptides on vessel segments from the same vascular regions. The overall distribution of perivascular nerve fibres was demonstrated using an antiserum to the general neuronal marker protein gene product 9.5 (PGP 9.5) and the percentage immunostained area of total vessel wall area occupied by PGP-containing nerves, in each of the basilar, posterior and middle cerebral arteries, was set at 100% and used to determine the relative density of specific populations of autonomic and sensory nerve fibres. In all four cerebral arteries, the majority of nerve fibres possessed neuropeptide Y (NPY) and tyrosine hydroxylase (TH) immunoreactivity, occupying 6.2-13.3% and 5.8-7.5% of the total vessel wall area, respectively. Vasoactive intestinal peptide (VIP), substance P (SP) and calcitonin-gene-related peptide (CGRP) were detected at lower densities. The pharmacological study performed on small circular segments with an intact endothelium revealed that, in all four cerebral arteries, NPY was a more potent constrictor than noradrenaline (NA). The rank order of potency for relaxant agents was CGRP = SP > VIP > ACh in the PCA and MCA, and SP = CGRP > VIP > ACh in the BA and ACA. The correlation between immunostained nerve area and the agonist potency suggested that the denser the peptidergic nerve-supply, the lower the sensitivity to the agonist.

Selective induction of cell cycle regulatory genes cdk1 (p34cdc2), cyclins A/B, and the tumor suppressor gene Rb in transformed cells by okadaic acid

Genes encoding cdk1 (p34cdc2), cyclin A, cyclin B, and the tumor suppressor gene Rb are fundamental regulators of cell cycle progression which associate as a complex with the transcription factor E2F. Expression of many of these proteins has previously been shown to be repressed by okadaic acid, a specific inhibitor of protein phosphatases 1/2A (PP1/PP2A), resulting in growth arrest in nontransformed but immortalized cells. We have investigated levels of mRNA encoding cdk1 (p34cdc2), cyclin A, cyclin B, Rb, GAPDH, c-myc, and histone H4 genes for sensitivity to okadaic acid in HeLa cells to determine if transformation altered their regulation. Serum starvation slowed growth and diminished mRNA levels for all genes tested except c-myc and GAPDH. When starved cells were subsequently exposed to 19 nM okadaic acid or refed 10% serum, mRNA levels of cyclin A, cyclin B, cdk1, and Rb dramatically increased while mRNA levels for c-myc and GAPDH were largely unaffected. Histone H4 mRNA levels and the rate of DNA synthesis were greatly enhanced by serum addition but not affected appreciably by okadaic acid. Okadaic acid was also effective in blocking proliferation of exponentially growing HeLa cells at G2/M and S phase. Despite the cell cycle phase-specific block, elevated mRNA levels for cdk1, cyclin A, cyclin B, Rb, and suppression of H4 mRNA levels were detected and persisted for at least 12 hr following okadaic acid removal. The results demonstrate that cell cycle progression is blocked and several cell cycle regulatory genes, encoding transcription factor E2F-associated proteins, experience elevation of mRNA levels through mechanisms sensitive to okadaic acid likely through a PP1/PP2A-sensitive mechanism. Data from transformed cells contrast with data from immortalized but nontransformed cells in which okadaic acid also blocks cell cycle progression during G2/M phase but suppresses expression of these genes. Such contrasts may be correlated with reduced growth factor dependence and transformation.

Relation between cyclic GMP generation and cerebrovascular reactivity: modulation by NPY and alpha-trinositol

It is considered that cyclic guanosine monophosphate (cGMP) plays a pivotal role in mediating the relaxation of vascular and nonvascular smooth muscles. cGMP steady state levels are regulated by guanylyl cyclase, cGMP phosphodiesterases and its flux from cells. The present study examines the possible relation between cerebrovascular vasodilator agents and generation of cGMP in guinea pig cerebral vessels. Acetylcholine, substance P, nitroglycerine and sodium nitroprusside significantly increased the generation of cGMP. The application of acetylcholine, substance P, nitroglycerine and sodium nitroprusside elicited concentration-dependent relaxation of basilar artery segments. Neuropeptide Y increased the generation of cGMP by 2%-46% of control levels (at 10(-7)-10(-6)M of neuropeptide Y; *P < 0.05). In addition, neuropeptide Y (10(-6)M) induced a transient relaxation of the precontracted guinea pig basilar arteries with endothelium. This transient relaxation was blocked by nitro-L-arginine (10(-4)M). alpha-Trinositol does not alter the formation of cGMP nor the neuropeptide Y-induced relaxation. In the presence of alpha-trinositol neuropeptide Y (10(-7)-10(-6)M) did not significantly elevate the production of cGMP as compared with controls. The rise in cGMP induced by acetylcholine, substance P and nitroglycerine was slightly increased by the addition of neuropeptide Y (3 x 10(-7) M). Acetylcholine and substance P induced an endothelium-dependent relaxation of the precontracted guinea pig basilar arteries, while sodium nitroprusside and nitroglycerine induced an endothelium-independent relaxation. Acetylcholine, substance P and nitroglycerine induced concentration-dependent relaxations of basilar artery, respectively. The relaxation elicited by acetylcholine or substance P, but not nitroglycerine, was markedly attenuated by neuropeptide Y (3 x 10(-7) M).(ABSTRACT TRUNCATED AT 250 WORDS)