Alteration of platelet aggregation in patients with thyroid disorders

To determine whether Graves' disease or primary hypothyroidism influence platelet function, we evaluated platelet aggregation in the platelet-rich plasma (PRP) from such patients. Platelet aggregation induced by adenosine diphosphate (ADP) in blood obtained from patients with untreated Graves' disease was significantly lower than normal, whereas that in patients with untreated primary hypothyroidism was relatively increased. The magnitude of platelet aggregation induced by collagen in both groups of patients resembled that induced by ADP. However, significant differences were evident between the two diseases (P < .05). In addition, we observed a significant inverse correlation between the extent of platelet aggregation and plasma levels of thyroid hormones (triiodothyronine [T3], thyroxine [T4], and free T3). Platelet aggregation returned to normal when the euthyroid condition was obtained in the patients following administration of antithyroid drugs or thyroid hormone. The findings are consistent with the possibility that thyroid hormones influence platelet aggregation partly via inhibition of myosin light-chain kinase (MLCK).

Antithrombotic effects of 3-([1:1',2':1"]-3'-terphenyl)propanol in animals

3-([1:1',2':1"]-3'-Terphenyl)propanol (CAS 186835-06-3, F050) and acetylsalicylic acid (ASA) inhibited platelet aggregation induced by CaCl2, arachidonic acid, collagen, adenosine diphosphate (ADP) and thrombin in guinea pigs, rabbits and rats in vitro. However, F050 had a wider spectrum of actions than ASA. Orally administered F050 inhibited platelet aggregation ex vivo. F050 significantly reduced the thrombus formation in the extracorporeal circulation thrombosis model in guinea pigs. It inhibited erythrocyte hemolysis induced by hypotonic NaCl, while ASA did not. F050, but not ASA, inhibited increases in platelet [CA2+]i caused by thrombin in guinea pigs. F050 is a parent compound that will facilitate the development of an orally active drug for the treatment of thrombotic diseases.

Anticoagulant activity of the novel thrombin inhibitor 1-butyl-3-(6,7-dimethoxy-2-naphthylsulfonyl) amino-3-(3-guanidinopropyl)-2-pyrrolidinone hydrochloride

1-Butyl-3-(6,7-dimethoxy-2-naphthylsulfonyl)amino-3-(3-guanidin opropyl)-2-pyrrolidinone hydrochloride (CAS 173440-64-7, SPI-501), which has highly selective thrombin-inhibitory activity, caused a concentration-dependent increase in the time taken for coagulation induced by thrombin in rabbit plasma. The IC50 of SPI-501 was 1.7 mumol/l. Argipidine also prolonged coagulation time and its activity was one order of magnitude greater than that of SPI-501. SPI-501 and argipidine caused dose-dependent increases in the activated partial prothrombin time (APTT) and prothrombin time (PT) of rat plasma. When APTT and PT were measured, IC50 values of SPI-501 were 38.0 and 18.5 mumol/l and those of argipidine, 1.4 and 1.9 mumol/l, respectively. Intravenous administration of SPI-501 (10 and 30 mumol/kg) and argipidine (1 and 3 mumol/kg) prolonged both APTT and PT in rats. While SPI-501 was less potent than argipidine, the durations of the effects of both were the same.

Controlled gene expression with a reverse tetracycline-regulated retroviral vector (RTRV) system

A retroviral vector was constructed with an autoregulatory cassette to allow expression of the gene of interest in response to oral administration of doxycycline (Dox) in vivo. The cassette contains all the components of the reverse tetracycline-regulated (rtTA) system, a drug selectable marker with the internal ribosome entry site and the gene of interest (GFP). FACS analyses showed an induction of GFP-fluorescence of two orders of magnitude in retrovirus-infected 208F cells dependent on the amount of Dox in the medium. Furthermore, oral administration of Dox resulted in GFP expression in transplanted 208F cells in the peritoneal cavity of nude mice. Thus this reverse tetracycline-regulated retroviral vector (RTRV) system simplifies the delivery of controllable genes to cultured and implanted cells. It is hoped that this approach may pave the way to controlled gene expression during a particular window of time in gene therapy applications.

Expression cloning and intracellular localization of a human ZF5 homologue

We isolated a cDNA encoding a human homologue of ZF5 (hZF5), which has five Kruppel-like C2H2 type zinc fingers at carboxyl terminus and the BTB/POZ (poxvirus and zinc finger) at the amino terminus, using autoimmune sera from a patient with overlap syndrome (dermatomyositis and scleroderma). Sequencing of the entire cDNA revealed an open reading frame (ORF) of 1349 bp with a deduced protein sequence of 449 amino acid residues and a calculated molecular weight of 51.3 kDa. The deduced amino acid sequence of hZF5 is highly homologous to mouse ZF5 (99.3% identity). Immunofluorescence studies revealed that HA-tagged hZF5 transiently expressed in COS-7 cells showed the nuclear dot pattern in the BTB/POZ domain-dependent manner.

Anti-mitosin antibodies in a patient with chronic graft-versus-host disease after allogeneic bone marrow transplantation

In a patient undergoing allogeneic BMT for ALL, chronic GVHD (cGVHD) with skin changes developed within 110 days after transplantation. One year post-BMT, anti-nuclear antibodies were detected. The patient's serum was used for immunoscreening of a HeLa cDNA library. Ten different overlapping positive clones were found to be partial clones of mitosin, a 350-kDa nuclear phosphoprotein which shows a speckled nuclear distribution in S phase and which relocates to the centromere and mitotic apparatus in M phase. Although autoantibodies against centromere protein-F, which is very similar to mitosin, have been reported in patients with cancer, this is the first report of autoantibodies against mitosin in a patient with cGVHD.

Characterization of a serum response factor-like protein in Saccharomyces cerevisiae, Rlm1, which has transcriptional activity regulated by the Mpk1 (Slt2) mitogen-activated protein kinase pathway

The Mpk1 (Slt2) mitogen-activated protein (MAP) kinase has been implicated in several biological processes in Saccharomyces cerevisiae. The Rlm1 protein, a member of the MADS box family of transcription factors, functions downstream of Mpk1 in the pathway. To characterize the role of Rlm1 in mediating the transcriptional activation by the Mpk1 pathway, we constructed a LexA-Rlm1 deltaN chimera in which sequences, including the MADS box domain of the Rlm1 protein, were replaced by the LexA DNA binding domain and tested the ability of this chimera to activate a LexA operator-controlled reporter gene. In this assay, the Rlm1 protein was found to activate transcription in a manner regulated by the Mpk1 pathway. The Mpk1 protein kinase phosphorylated Rlm1 deltaN in vitro and the LexA-Rlm1 deltaN chimera protein was phosphorylated in vivo in a Mpk1-dependent manner. These results suggest that Mpk1 regulates the transcriptional activity of Rlm1 by directly phosphorylating it. We identified a Mpk1-like protein kinase, Mlp1, as an Rlm1-associated protein by using the yeast two-hybrid system. Overexpression of MLP1 suppresses the caffeine-sensitive phenotype of the bck1 delta mutation. The additivity of the mlp1 delta defect with the Mpk1 delta defect with regard to the caffeine sensitivity, combined with the results of genetic epistasis experiments, suggested that the activity of Rlm1 is regulated independently by Mpk1 MAP kinase and the Mlp1 MAP kinase-like kinase.

High-affinity binding of DTZ323, a novel derivative of diltiazem, to rabbit skeletal muscle L-type Ca++ channels

A novel derivative of diltiazem (1,5-benzothiazepine Ca++ antagonist), DTZ323, 3-(acetyloxy)-5-[2-[[2-(3,4-dimethoxyphenyl)ethyl]-methylamino]eth yl]-2,3-dihydro-2-(4-methoxyphenyl)-1,5-benzothiazepine-4(5H)-one, was characterized by radioligand binding experiments with rabbit skeletal T-tubule membranes in terms of the affinity and the selectivity to the binding sites for the three classical calcium antagonists, such as dihydropyridines, phenylalkylamines and benzothiazepines. DTZ323, like diltiazem and clentiazem, exhibited complete and concentration-dependent inhibition of d-cis-[3H]diltiazem binding to the membrane with a slope factor close to unity. Ki values indicated that DTZ323 (Ki = 6.6 +/- 0.6 nM, mean +/- S.E., n = 4) was 48 times and 9 times more potent than diltiazem and clentiazem, respectively. DTZ323 partially inhibited the specific binding of a dihydropyridine ligand, (+)-[3H]PN200-110, at 37 degrees C. The equilibrium saturation study showed that DTZ323 reduces the affinity for the (+)-[3H]PN200-110 binding in a concentration-dependent manner with a slight decrease in the density of the binding sites. DTZ323 also inhibited the specific binding of a phenylalkylamine ligand, (-)-[3H]D888, completely as did diltiazem. DTZ323 (1 microM) had no effect on the dissociation rate of d-cis-[3H]diltiazem at 2 degrees C, whereas 30 microM verapamil increased the dissociation rate, which suggested that DTZ323 inhibits the specific binding of d-cis-[3H]diltiazem in a manner similar to other competitive ligands for the benzothiazepine binding site. These results indicate that DTZ323 is a selective ligand for the 1,5-benzothiazepine binding site with the highest affinity among the diltiazem derivatives.

Phosphorylation of ATF-1 enhances its DNA binding and transcription of the Na,K-ATPase alpha 1 subunit gene promoter

Transcriptional activity of both ATF-1 and CREB is enhanced by protein phosphorylation. While enhancement has been attributed to an increase in binding affinity for a co-activator (CBP), induction of the DNA binding activity by phosphorylation is an open question. Using the Na,K-ATPase alpha1 subunit gene promoter, which has an asymmetrical ATF/CRE site, we analyzed the effect of phosphorylation on DNA binding activity of the ATF-1-CREB heterodimer. Dephosphorylation of the heterodimer in nuclear extracts reduced binding to the ATF/CRE site. Phosphorylation of ATF-1 at Ser63 enhanced its binding to the ATF/CRE site in both the homodimeric and heterodimeric forms. Transcription of the Na,K-ATPase alpha 1 subunit gene promoter was also stimulated by phosphorylated ATF-1 in vitro.

Echographia as a symptom of interictal state in an epileptic patient: a case report

Echographia is a phenomenon in which a patient continuously translates verbal stimuli into writing. We encountered a patient with epilepsy who developed visual echographia during interictal periods. In this case, echographia was observed during two different periods, namely the period of disturbed consciousness after the epileptic seizure and the period of clear consciousness after suppression of the seizures. Disinhibition due to disturbance of the consciousness is considered to have been the cause of echographia in the former period. In the latter period, it is considered that echographia was caused by the release of lower function from suppression of upper function by brain dysfunction, as the after effect of status epilepticus. As echographia can be observed in epileptic patients, attention and careful observation by epileptologists is needed.

Antithrombotic effects of the novel inhibitor of thrombin-induced offtelet aggregation and thrombus formation, 3-[2-[1,1':2',1"]-terphenyl-4'-yl)ethyl]phenoxyacetic acid

The new compound 3-[2-([1,1':2,1"]-terphenyl-4'yl)ethyl]phenoxyacetic acid (F1070) was synthesized and its effects on platelet aggregation induced by thrombin, thrombin receptor agonist peptide (TRAP), ADP and collagen were evaluated in humans, guinea pigs and rats, and were compared with the effects of he thrombin antagonists argipidine and (D)Phe-Pro-Arg-CH2Cl (FPR). F1070 inhibited the platelet aggregation induced by these agonists and was highly selective in its inhibition of thrombin. F1070 inhibited fibrin formation induced by thrombin, but far less effectively than argipidine. In a guinea pig model of extracorporeal circulation thrombosis, F1070 (10 mg/kg p.o.) significantly inhibited the development of a thrombus. F1070 is thus a key compound that should facilitate the development of new orally active antithrombotic drugs that are specific for thrombin.

Gene therapy against an experimental glioma using adeno-associated virus vectors

The efficacy of gene therapy for glioma was examined using adeno-associated virus (AAV)-based vectors to deliver genes to experimental tumors in mice. Stereotactic injection of 2 x 10(5) U-251SP human glioma cells into the brains of nude mice produced tumors of 19.06 +/- 1.79 mm2 17 days after injection. Employing a high titer preparation of AAV vector containing the gene for beta-galactosidase (AAV-lacZ), dose-dependent transduction of U-251SP cells was seen in vitro. When 1.6 x 10(10) AAV-lacZ particles were directly injected into tumors in vivo, 30-40% of the cells along the needle track expressed beta-galactosidase. Transduction of U-251SP cells in vitro with an AAV vector containing a bicistronic gene encoding both herpes simplex thymidine kinase and human interleukin-2 (AAV-tk-IRES-IL2) rendered them sensitive to the cytocidal effects of ganciclovir (GCV) and IL-2 was produced in a dose-dependent manner. Cocultures of AAV-tk-IRES-IL2 transduced cells and nontransduced cells proved highly sensitive to GCV indicating the contribution of the bystander effect. Stereotactic delivery of 6 x 10(10) AAV-tk-IRES-IL2 particles into day 7 tumors in nude mice followed by administration of GCV for 6 days, resulted in a 35-fold reduction in the mean volume of tumors compared with controls. Normal brains did not suffer from any toxic effect of the administration of AAV-tk-IRES-IL2 and GCV. These results indicate that high titer AAV vector treatment may be safe and effective for in vivo gene therapy of human brain tumors.

Purification and identification of a major activator for p38 from osmotically shocked cells. Activation of mitogen-activated protein kinase kinase 6 by osmotic shock, tumor necrosis factor-alpha, and H2O2

A stress-activated, serine/threonine kinase, p38 (also known as HOG1 or MPK2) belongs to a subgroup of mitogen-activated protein kinase (MAPK) superfamily molecules. An activity to activate p38 (p38 activator activity) as well as p38 activity itself were greatly stimulated by hyperosmolar media in mouse lymphoma L5178Y cells. The activator activity has been purified by sequential chromatography. A 36-kDa polypeptide that was coeluted with the activity in the final chromatography step was identified as MAPK kinase 6 (MAPKK6) by protein microsequencing analysis. Monoclonal and polyclonal antibodies raised against recombinant MAPKK6 recognized specifically the 36-kDa MAPKK6 protein but did not cross-react with MKK3 proteins. The use of these anti-MAPKK6 antibodies revealed that two major peaks of the p38 activator activity in the first chromatography step reside in the activated MAPKK6. Using a genetic screen in yeast, we isolated MKK3b, an alternatively spliced form of MKK3. Like MKK3 and MAPKK6, MKK3b was shown to be a specific activator for p38 and was activated by osmotic shock when expressed in COS7 cells. Immunoblotting analysis revealed that MAPKK6 is expressed highly in HeLa and KB cells and scarcely in PC12 cells, whereas MKK3 and MKK3b are expressed in all cells examined. Immunodepletion of MAPKK6 from the extracts obtained from L5178Y cells and KB cells exposed to hyperosmolar media depleted them of almost all of the p38 activator activity, indicating that MAPKK6 is a major activator for p38 in an osmosensing pathway in these cells. In addition, MAPKK6 was activated strongly by tumor necrosis factor-alpha, H2O2, and okadaic acid and moderately by cycloheximide in KB cells. Thus, there are at least three members of p38 activator, MKK3, MKK3b, and MAPKK6, and MAPKK6 may function as a major activator for p38 when expressed.

Calmodulin-dependent protein kinase II potentiates transcriptional activation through activating transcription factor 1 but not cAMP response element-binding protein

Activating transcription factor 1 (ATF1) and the cAMP response element-binding protein (CREB) are members of the CREB/ATF family implicated in cAMP- and calcium-induced transcriptional activation. Although ATF1 and CREB share extensive homology, the function of ATF1 is poorly understood. Its phosphorylation state and activation by Ca2+- and calmodulin-dependent protein kinase (CaMK) II were therefore examined. Phosphopeptide mapping analysis and Western blotting studies demonstrated that in vitro, CaMK II phosphorylates only Ser63 (corresponding to Ser133 of CREB), which is essential for the activation, and not Ser72 (corresponding to Ser142 of CREB), which is a negative regulation site. Both ATF1 and CREB bound CBP in a phosphorylation-dependent manner. As expected from these in vitro studies, transient transfection studies revealed that ATF1 is activated by CaMK II. Our findings suggest that CaMK II mediates transactivation of cAMP responsive genes via ATF1.

In vitro antiplatelet activity of the carbinol analogue of ketoprofen, 3-(1-methyl-2-hydroxyethyl)-benzophenone

3-(1-Methyl-2-hydroxyethyl)-benzophenone (F025) is a close structural analogue of ketoprofen, in which the carboxylic acid of ketoprofen is reduced to a carbinol moiety. The in vitro effects of F025 on platelet aggregation, cyclooxygenase and hypotonic NaCl-induced erythrocyte hemolysis were examined in comparison with those of ketoprofen. Although the inhibitory activity of F025 on collagen, arachidonic acid and ADP-induced platelet aggregation was between 2 and 20 times that of ketoprofen in healthy volunteers, guinea pigs, rabbits and rats, F025 had only one-tenth of the inhibitory action of ketoprofen on sheep seminal vesicle cyclooxygenase F025, but not ketoprofen, inhibited hypotonic NaCl-induced erythrocyte hemolysis in guinea pigs. The substantial antiplatelet activity of F025 may be due to membrane stabilization as well as to cyclooxygenase inhibition.

Anticoagulant peptides; synthesis, stability and antithrombin activity of hirudin C-terminal-related peptides and their disulfated analog

We designed a unique anticoagulant decapeptide, which possesses two O-sulfated tyrosine residues, based on the structure of hirudin's C-terminal functional domain. We first prepared a series of octa-, nona- and decapeptides with no sulfation, Suc-Phe-Glu-Pro-Ile-Pro-Glu-Tyr-Tyr-X-OH [X = bond, Leu or Leu-Gln], by a solution phase method and measured their thrombin times (TT) using human thrombin and rabbit plasma. The shortest octapeptide (3a) showed full antithrombin activity comparable to that of the lead compound hirudin (54-65), and the longest decapeptide (3c) prolonged TT most potently with an IC50 value of 5.8 microM. We consequently converted 3c to a disulfated decapeptide (NF-22) with SO3.pyridine complex and compared its antithrombin activity with that of known hirudin-related peptides: hirugen, MDL28050 and hirulog-1. NF-22 showed potent antithrombin activity with an IC50 value of 0.3 microM, being more potent than hirugen and MDL28050 (IC50 values of 4.0 microM and 1.1 microM, respectively). NF-22 was as potent as hirulog-1. NF-22 showed no change in activity in aqueous solution for 10 d at 60 degrees C, and remained about 90% unchanged in rat plasma on incubation for 24h at 37 degrees C, whereas the corresponding unsulfated peptide (3c) was completely digested under the same condition. NF-22 appears to be one of the most potent and stable peptide anticoagulants among the hirudin analogs.

A novel kinase cascade mediated by mitogen-activated protein kinase kinase 6 and MKK3

A cDNA encoding a novel member of the mitogen-activated protein kinase kinase (MAPKK) family, MAPKK6, was isolated and found to encode a protein of 334 amino acids, with a calculated molecular mass of 37 kDa that is 79% identical to MKK3. MAPKK6 was shown to phosphorylate and specifically activate the p38/MPK2 subgroup of the mitogen-activated protein kinase superfamily and could be demonstrated to be phosphorylated and activated in vitro by TAK1, a recently identified MAPKK kinase. MKK3 was also shown to be a good substrate for TAK1 in vitro. Furthermore, when co-expressed with TAK1 in cells in culture, both MAPKK6 and MKK3 were strongly activated. In addition, co-expression of TAK1 and p38/MPK2 in cells resulted in activation of p38/MPK2. These results indicate the existence of a novel kinase cascade consisting of TAK1, MAPKK6/MKK3, and p38/MPK2.

Suppression of CD44 expression decreases migration and invasion of human glioma cells

We have reported high expression of CD44H in human glioma cells. To investigate the role of CD44H in the invasion of human glioma, we established a CD44-anti-sense-gene-expression glioma cell line named U-251A1. The expression of CD44H in the G-418-selected U-251A1 cells was reduced to 20% of that in the parental U-251SP cells, as determined by flow-cytometry analysis. We first examined the migratory responses of U-251A1 cells in vitro by time-lapse video-microscopic sparse cell-migration assay on hyaluronic acid or on chondroitin 6 sulfate. U-251A1 cells did not show significant differences in motility on any substrate, while U-251SP and other CD44H-positive cells showed dose-dependent increase of migration specifically on hyaluronic acid. To examine the physiologic function of CD44H in gliomas in vivo, U-251A1 and its control cells, U-251S1, which retain CD44-sense-expression vector, were injected stereotactically into the brains of nude mice. U-251A1 cells were localised in the region of the injection site, with relatively well demarcated borders between tumour and brain tissue, while the control cells demonstrated a cell-infiltration pattern. Our data suggest that CD44H may be required for infiltration of glioma cells through its interaction with hyaluronic acid, a major component of the brain extracellular matrix.

Molecular cloning and characterization of a cDNA encoding a novel basic helix-loop-helix protein structurally related to Neuro-D/BHF1

We cloned a novel basic helix-loop-helix protein, NDRF (NeuroD-related factor), cDNA. NDRF contains 383 amino acids and exhibits 53.4% and 52.2% sequence identity to NeuroD and MATH-2/NEX-1, respectively. NDRF mRNA appears in the brain of 12-day-old mouse embryos and is localized in certain regions of the adult brain, such as the hippocampus, dentate gyrus and cerebellum, Thus, the structure and expression patterns of NDRF are similar to but distinct from those of NeuroD and MATH-2/NEX-1, suggesting that NDRF may play distinct roles in neural development and plasticity as a novel member of the NeuroD family.

Effects of anandamide and arachidonic acid on specific binding of (+) -PN200-110, diltiazem and (-) -desmethoxyverapamil to L-type Ca2+ channel

We examined the effects of anandamide (N-arachidonoylethanolamine) on the binding of three types of Ca2+ channel antagonists for L-type Ca2+ channel, i.e., 1,4-dihydropyridine, 1,5-benzothiazepine and phenylalkylamine, to rabbit skeletal muscle membranes. Anandamide inhibited the binding of all three ligands. Arachidonic acid, a putative metabolite or a precursor of anandamide, inhibited 1,4-dihydropyridine binding, whereas it augmented both 1,5-benzothiazepine and phenylalkylamine binding. The involvement of prostaglandins synthesized from arachidonic acid was considered to be minor. These findings indicate that both anandamide and arachidonic acid interact not only with 1,4-dihydropyridine but also with 1,5-benzothiazepine and phenylalkylamine binding sites as a common feature of unsaturated lipids.

[Transcriptional regulation by cAMP and calcium]

Transcription of a number of eukaryotic genes is activated in response to an increase in the intracellular cAMP concentration. These genes stimulated by cAMP have a common promoter element, cAMP response element (CRE). The CRE is recognized by a CRE binding protein, CREB. The binding of CREB to CRE does not induce transcription. Activation of transcription requires the phosphorylation or CREB at Ser-133. In the case of the cAMP pathway, the activated catalytic subunit of cAMP-dependent protein kinase (PKA) translocates to the nucleus and phosphorylates Ser-133 of CREB. In the nervous system, signals transmitted across synapses are known to regulate gene expression in the post-synaptic cell. This process often involves membrane depolarization and subsequent amplification of intracellular Ca2+. The transcriptional activation induced by membrane depolarization and Ca2+ influx is mediated by a promoter element, called the Ca(2+)-responsive element (CaRE). Recent studies of c-fos and proenkephalin gene expression have shown that the CaRE is indistinguishable from a CRE. In this paper, we focus on the possible interactions between Ca2+ and the cAMP signaling pathways into the nucleus.

Differential distribution of CaM kinases and induction of c-fos expression by flashing and sustained light in rat retinal cells

PURPOSE

To examine the expression of c-fos proto-oncogene and phosphorylation of cAMP responsive element binding (CREB) protein in the rat retina after changes in the light-dark condition.

METHODS

Rats were exposed to both steady light and flashing light and were killed at the end of light exposure. The retinas were analyzed by in situ hybridization using single-stranded RNA probes for c-fos transcripts and by immunocytochemistry using phosphoSer-133 specific CREB antiserum, anti-calcium calmodulin dependent protein (CaM) kinase II, and anti-CaM kinase IV.

RESULTS

c-fos mRNA was expressed in the outer half of the inner nuclear layer (INL) and in the ganglion cell layer (GCL) after 30 minutes of sustained light. After 30 minutes of flashing light, c-fos expression also was detected in the inner border of the INL. Phosphorylated CREB immunoreactive nuclei had similar distribution after steady and flashing light. Both CaM kinase II and CaM kinase IV, which phosphorylate CREB at Ser 133 in vitro, were expressed in the GCL and in the INL. CaM kinase II, however, was localized in the inner border of the INL, whereas CaM kinase IV was distributed in the outer half of the INL.

CONCLUSIONS

These results suggest that the differential expression of c-fos mRNA induced by flashing and sustained light may reflect the CREB phosphorylation by CaM kinases in a different subpopulation of retinal cells.