Active mitochondria surrounding the pancreatic acinar granule region prevent spreading of inositol trisphosphate-evoked local cytosolic Ca(2+) signals

Agonist-evoked cytosolic Ca(2+) spikes in mouse pancreatic acinar cells are specifically initiated in the apical secretory pole and are mostly confined to this region. The role played by mitochondria in this process has been investigated. Using the mitochondria-specific fluorescent dyes MitoTracker Green and Rhodamine 123, these organelles appeared as a bright belt concentrated mainly around the secretory granule area. We tested the effects of two different types of mitochondrial inhibitor on the cytosolic Ca(2+) concentration using simultaneous imaging of Ca(2+)-sensitive fluorescence (Fura 2) and electrophysiology. When carbonyl cyanide m-chlorophenylhydrazone (CCCP) was applied in the presence of the Ca(2+)-releasing messenger inositol 1,4, 5-trisphosphate (IP(3)), the local repetitive Ca(2+) responses in the granule area were transformed into a global rise in the cellular Ca(2+) concentration. In the absence of IP(3), CCCP had no effect on the cytosolic Ca(2+) levels. Antimycin and antimycin + oligomycin had the same effect as CCCP. Active mitochondria, strategically placed around the secretory pole, block Ca(2+) diffusion from the primary Ca(2+) release sites in the granule-rich area in the apical pole to the basal part of the cell containing the nucleus. When mitochondrial function is inhibited, this barrier disappears and the Ca(2+) signals spread all over the cytosol.

Calcium binding capacity of the cytosol and endoplasmic reticulum of mouse pancreatic acinar cells

1. The droplet technique was used in this study to measure total calcium loss from pancreatic acinar cells due to calcium extrusion. The calcium binding capacity of the cytosol (kc) was measured as the ratio of the decrease in the total calcium concentration of the cytosol of the cell (Delta[Ca]c) and the synchronously occurring decrease in the free calcium ion concentration in the cytosol (Delta[Ca2+]c). The calcium dependency of the calcium binding capacity was determined by plotting values of kc against the corresponding [Ca2+]c. The rise in the cytosolic Ca2+ concentration of pancreatic acinar cells was triggered by stimulation with a supramaximal dose of cholecystokinin (CCK). The recovery of [Ca2+]c during continued exposure to the agonist was due to calcium extrusion from the cell. 2. The calcium binding capacity was about 1500-2000 for the [Ca2+]c range 150-500 nM. The mechanism of buffering was not investigated in this study. The calcium binding capacity of the cytosol did not vary significantly with [Ca2+]c in this range. The CCK-evoked decrease in the total calcium concentration in the lumen of the endoplasmic reticulum (ER) can be estimated from our data, taking into account previously published values for the volume of the ER in pancreatic acinar cells. Comparing the decrease in the total ER calcium concentration with our recently reported values for agonist-induced reductions in the free Ca2+ concentration inside the ER, we estimate that the calcium binding capacity of the ER is approximately 20. In pancreatic acinar cells we have therefore found a difference of two orders of magnitude in the efficiency of calcium buffering in the cytosol and the ER lumen.

Intracellular glucose switches between cyclic ADP-ribose and inositol trisphosphate triggering of cytosolic Ca2+ spiking

Cyclic ADP-ribose (cADPR) is a potentially important intracellular Ca2+ releasing messenger [1-5]. In pancreatic acinar cells where intracellular infusion of both inositol trisphosphate (IP3) and cADPR evoke repetitive Ca2+ spiking [6], the cADPR antagonist 8-NH2-cADPR [7], which blocks cADPR-evoked but not IP3-evoked Ca2+ spiking, can abolish Ca2+ spiking induced by physiological levels of the peptide hormone cholecystokinin (CCK) [8]. We have tested the effect of intracellular glucose on the ability of IP3, cADPR and CCK to induce cytosolic Ca2+ spikes in pancreatic acinar cells. In order to gain access to the intracellular cytosol, we used the whole-cell configuration of the patch-clamp technique [9] and monitored cytosolic Ca2+ concentration changes by measuring the Ca(2+)-dependent ionic current [10-13]. Glucose (300 microM to 10 mM) in the patch pipette/intracellular solution prevented cADPR from evoking Ca2+ spiking. The same effect was observed with 2-deoxy-glucose, but not L-glucose. In contrast, glucose potentiated IP3-evoked Ca2+ spiking. CCK evoked Ca2+ spiking irrespective of the presence or absence of intracellular glucose, but the cADPR antagonist 8-NH2-cADPR blocked CCK-evoked Ca2+ spiking only in the absence of intracellular glucose. This suggests that the hormone can evoke Ca2+ spiking via either the IP3 or the cADPR pathway. The intracellular glucose level may control a switch between these two pathways.

Two cases of intrapulmonary lymph node presenting as a peripheral nodular shadow: diagnostic differentiation from lung cancer

We present two cases of intrapulmonary lymph node. The patients were a 44-year-old woman and a 71-year-old man each with a small peripheral nodule in the lung. On computed tomography (CT) scans, both nodules were spiculated. Since histological diagnosis could not be obtained by bronchoscopic examination or CT-guided needle biopsy, they underwent video-assisted thoracoscopic surgery. Histological examination of the resected material revealed that both nodules were composed of lymph node. Intrapulmonary lymph node has until recently been assigned no clinical significance; however, differential diagnosis of this lesion from lung cancers and other metastatic tumors is now clinically important.

The calcium store in the nuclear envelope

The nuclear envelope has a relatively small volume, but is connected up to the vastly larger endoplasmic reticulum. The Ca2+ concentration in the lumen of the interconnected nuclear envelope and endoplasmic reticulum network is in the resting state maintained at a level of more than 100 microM. There are specific Ca2+ release channels present in the inner nuclear membrane that can be activated by inositol trisphosphate or cADP ribose. The system, therefore, allows selective release of Ca2+ into the nucleoplasm which could be important for the control of specific types of gene expression.

Termination of cytosolic Ca2+ signals: Ca2+ reuptake into intracellular stores is regulated by the free Ca2+ concentration in the store lumen

The mechanism by which agonist-evoked cytosolic Ca2+ signals are terminated has been investigated. We measured the Ca2+ concentration inside the endoplasmic reticulum store of pancreatic acinar cells and monitored the cytoplasmic Ca2+ concentration by whole-cell patch-clamp recording of the Ca2+-sensitive currents. When the cytosolic Ca2+ concentration was clamped at the resting level by a high concentration of a selective Ca2+ buffer, acetylcholine evoked the usual depletion of intracellular Ca2+ stores, but without increasing the Ca2+-sensitive currents. Removal of acetylcholine allowed thapsigargin-sensitive Ca2+ reuptake into the stores, and this process stopped when the stores had been loaded to the pre-stimulation level. The apparent rate of Ca2+ reuptake decreased steeply with an increase in the Ca2+ concentration in the store lumen and it is this negative feedback on the Ca2+ pump that controls the Ca2+ store content. In the absence of a cytoplasmic Ca2+ clamp, acetylcholine removal resulted in a rapid return of the elevated cytoplasmic Ca2+ concentration to the pre-stimulation resting level, which was attained long before the endoplasmic reticulum Ca2+ store had been completely refilled. We conclude that control of Ca2+ reuptake by the Ca2+ concentration inside the intracellular store allows precise Ca2+ signal termination without interfering with store refilling.

Phospholipase C inhibitor, U73122, releases intracellular Ca2+, potentiates Ins(1,4,5)P3-mediated Ca2+ release and directly activates ion channels in mouse pancreatic acinar cells

It is recognized in many cellular systems that the receptor/G-protein activation of phospholipase C and Ins(1,4,5)P3 production is the transduction pathway regulating the release of Ca2+ from internal stores. Ca2+ signals can now be monitored at the level of single cells but the biochemical detection of Ins(1,4,5)P3 cannot match this resolution. It is often difficult or impossible to directly attribute responses evoked in single cells by putative phospholipase C-coupled agonists to changes in Ins(1,4,5)P3 levels. U73122 is an aminosteroid that is reported to act as a specific inhibitor of phospholipase C and it has become an important tool in establishing the link between phospholipase C activation and cellular Ca2+ signalling. In the present study we use both patch-clamp electrophysiology and the imaging of fluorescent Ca2+ indicators to investigate the effect of U73122 in mouse pancreatic acinar cells. The study reveals that U73122 has effects other than the inhibition of phospholipase C. U73122 can directly activate ion channels. It can itself promote the release of Ca2+ from intracellular stores in permeabilized cells and in intact cells it triggers a release of Ca2+ that is initiated specifically at the secretory pole of these morphologically and functionally polarized cells. We also present evidence that U73122 can potentiate the response to Ins(1,4,5)P3; this is seen both in permeabilized cells and in patch-clamp protocols in which cells are internally dialysed with submaximal concentrations of Ins(1,4,5)P3. The effects of U73122 are therefore multiple and not specific for the inhibition of phospholipase C. Importantly, all the effects described influence Ca2+ signalling yet in many experimental protocols some of these effects can go unnoticed and might in error be attributed simply to the inhibition of Ins(1,4,5)P3 production.

Ca2+ flow via tunnels in polarized cells: recharging of apical Ca2+ stores by focal Ca2+ entry through basal membrane patch

Intracellular Ca2+ store depletion induces Ca2+ entry across the plasma membrane, allowing the store to recharge. In our experiments, Ca2+ stores in pancreatic acinar cells were depleted by acetylcholine (ACh) stimulation in Ca2+-free solution. Thereafter, Ca2+ entry was only allowed through a CaCl2-containing pipette attached to the basal membrane. Recharging intracellular Ca2+ stores via a patch pipette occurred without a rise in the cytosolic Ca2+ concentration and depended on the operation of a thapsigargin-sensitive Ca2+ pump. After a period of focal Ca2+ entry, ACh could again evoke a rise in the cytosolic Ca2+ concentration, and this rise always started in the apical secretory pole. Recharging the apical Ca2+ store therefore depends on Ca2+ flow through a tunnel from the basal to the secretory pole, and the endoplasmic reticulum Ca2+ pump is essential for this process.

Blockade of DNA synthesis induced by platelet-derived growth factor by tranilast, an inhibitor of calcium entry, in vascular smooth muscle cells

The present study was conducted to establish a pharmacological method of controlling growth of vascular smooth muscle cells (VSMC) by blocking calcium entry. In cultured rat VSMC, 1 nM platelet-derived growth factor (PDGF) induced a biphasic elevation of cytoplasmic free calcium concentration, ([Ca2+]c). The second sustained phase of [Ca2+]c was dependent on extracellular calcium. At lower concentrations, PDGF induced oscillatory changes in [Ca2+]c, and reduction of extracellular calcium attenuated the oscillation. An antiallergic compound, tranilast, abolished the sustained phase of [Ca2+]c induced by 1 nM PDGF. Tranilast also inhibited the oscillatory changes in [Ca2+]c induced by 200 pM PDGF. In addition, PDGF-induced calcium influx in the late G1 phase, as assessed by measuring the initial uptake of 45Ca, was inhibited by tranilast in a concentration-dependent manner. Tranilast also inhibited PDGF-augmented DNA synthesis; the ID50 for the inhibition of DNA synthesis was nearly identical to that for calcium influx. Although tranilast blocked PDGF-induced calcium entry, it did not affect PDGF-mediated autophosphorylation of the PDGF receptor, activation of phosphatidylinositol 3-kinase, activation of Ras or mitogen-activated protein kinase. Similarly, PDGF-induced elevation of diacylglycerol was not affected by tranilast. These results suggest that the antiallergic drug tranilast inhibits PDGF-induced DNA synthesis by blocking PDGF-mediated calcium entry. Tranilast may be of use in controlling PDGF-induced DNA synthesis in VSMC.

Primary lung cancer associated with diffuse granulomatous lesions in the pulmonary parenchyma

A 60-year-old man was admitted to our hospital for productive cough. Chest roentgenography and CT scan disclosed a left hilar tumor invading the mediastinum, with mediastinal lymphadenopathy and diffuse micronodular shadows in both lung fields. A biopsied sample of the tumor revealed squamous cell carcinoma, while noncaseating epithelioid cell granulomas were observed in the samples obtained by transbronchial lung biopsy. The granulomas in the pulmonary parenchyma were determined to be sarcoid reactions secondary to lung cancer, since there was no evidence of sarcoidosis. Combination chemotherapy was effective for the tumor, and the granulomas disappeared after completion of the chemotherapy. These findings suggest the presence of a relationship between sarcoid reactions and lung cancer in this case.

[Intrahepatic arterial infusion chemotherapy for the colon cancer patients with liver metastases--a comparison of arterial embolization chemotherapy versus continuous arterial infusion chemotherapy]

To compare the prognostic benefit between arterial embolization chemotherapy (AEC) and continuous arterial infusion chemotherapy (CAIC), we clinicopathologically examined 32 colorectal cancer patients with liver metastases. Seventy patients were treated with AEC, and 15 patients with CAIC. In the AEC regimen, either ADR or CDDP dissolved in Lipiodol was infused by the implanted reservoir every one to two months. Otherwise, for the CAIC regimen, 360 mg/m2/day of 5-FU was continuously infused by the reservoir for 14 days. Subsequently, on day 22 after the initial 5-FU infusion, 180 mg/m2/day of 5-FU was continuously infused for 7 days. After a 7-day interval without infusion, 180 mg/m2/day of 5-FU was infused for 7 days. This 7-day infusion/7-day no-infusion cycle was repeated. The efficacy of the AEC was 6% (1 PR + 7 NC + 9 PD), CAIC (6 PR + 4 NC + 5 PD), suggesting that CAIC provides the better response rate. With regard to prognosis, the 1- and 2-year survival rates of AEC were 63% and 19%, respectively. The median survival time was 415 days. Otherwise, the 1- and 2-year survival with CAIC was 54% and 40%, respectively, and the median survival time was 470 days. No significant difference between the AEC and the CAIC was observed in the colorectal cancer patients with liver metastases.

Modulation of adenosine triphosphate-sensitive potassium channel and voltage-dependent calcium channel by activin A in HIT-T15 cells

The ATP-sensitive potassium channel (KATP channel) determines the membrane potential of pancreatic beta-cells and plays a critical role in the regulation of insulin secretion. The present study was conducted to investigate the effect of activin A, a member of the transforming growth factor-beta supergene family, on the KATP channel in HIT-T15 clonal hamster insulinoma cells. In an excised inside-out patch, ATP-sensitive currents with a single channel conductance of approximately 20 picosiemens were observed. In an outside-out patch, currents with identical unitary conductance were also observed. In either case, the currents were augmented by diazoxide and blocked by glibenclamide, verifying that they were KATP channel currents. When KATP channel currents were monitored in an outside-out patch, activin A added to the bath solution inhibited KATP channel currents. Upon removal of activin A, the KATP channel currents were restored, suggesting that the inhibition was not due simply to spontaneous disappearance of channel activity (run-down). The KATP channel activity was markedly reduced after the addition of activin A and was reversed by diazoxide. Besides the inhibition of KATP channel, activin A increased, in a perforated patch, the amplitude of the inward Ba2+ current in response to a depolarizing pulse from -40 to +10 mV. Under the current clamp condition, activin A induced gradual depolarization, followed by a burst of action potentials. Activin-mediated action potentials were accompanied by an elevation of the cytoplasmic free calcium concentration. These results indicate that activin A causes depolarization of the plasma membrane by inhibiting the activity of the KATP channel. In addition, activin A directly modulates the voltage-dependent calcium channel and augments calcium entry.

Expression of calcium-permeable cation channel CD20 accelerates progression through the G1 phase in Balb/c 3T3 cells

CD20 is a transmembrane protein that functions as a Ca(2+)-permeable cation channel (Bubien, J. K., Zhou, L. J., Bell, P. D., Frizzel, R. A., and Tedder, T. F. (1993) J. Cell Biol. 121, 1121-1132) and is involved in growth regulation of B lymphocytes. In order to further investigate the role of calcium entry in cell cycle progression, we introduced the cDNA encoding a Ca(2+)-permeable cation channel, CD20, into Balb/c 3T3 cells. Balb/c 3T3 cells transfected with a vector containing cDNA encoding CD20 expressed the CD20 protein, which was detected by assaying the binding of a monoclonal antibody against CD20. Calcium-permeable cation channel activity was detected in CD20-expressing cells by whole cell patch clamp recording and microfluorometric determination of the cytoplasmic Ca2+ concentration using fura-2. The expression of CD20 induced significant alterations in the responses of the cells to insulin-like growth factor-I (IGF-I). IGF-I induced DNA synthesis by control cells only when they had been pretreated with both platelet-derived growth factor (PDGF) and epidermal growth factor (EGF). In contrast, DNA synthesis by 30% of the quiescent CD20-expressing cells was initiated in response to IGF-I in the absence of priming with PDGF and EGF. When control quiescent cells were primed with PDGF and EGF, the addition of IGF-I led to the initiation of DNA synthesis after 14 h or more, whereas it induced DNA synthesis by CD20-expressing cells primed with PDGF and EGF 4 h earlier. The IGF-induced DNA synthesis was dependent on extracellular Ca2+, and expression of CD20 reduced the concentration of extracellular Ca2+ required for it. Furthermore, DNA synthesis by approximately 25% of the CD20-expressing cells was initiated after priming with PDGF and EGF, even in the absence of the progression factor IGF-I. These results indicate that CD20 expressed in Balb/c 3T3 cells functions as a constitutively active Ca(2+)-permeable cation channel and that expression of CD20 accelerates G1 progression in a Ca(2+)-dependent manner.

Conversion of amylase-secreting rat pancreatic AR42J cells to neuronlike cells by activin A

When AR42J cells, an amylase-secreting pancreatic exocrine cell line, were treated with activin A, cells extended neuritelike processes, and, concomitantly, amylase-containing vesicles disappeared. Immunofluorescence and immunoelectron microscopy revealed that these processes had neurite-specific cytoskeletal architectures: neurofilaments and microtubule bundles with cross-bridges of microtubule-associated protein 2. In addition to such morphological changes, activin-treated cells exhibited a marked increase in cytoplasmic free calcium concentration in response to depolarizing concentration of potassium. Moreover, activin-treated AR42J cells expressed mRNA for alpha 1 subunit of the neuroendocrine/beta cell-type voltage-dependent calcium channel. In naive AR42J cells, a sulfonylurea compound, tolbutamide, did not affect free calcium concentration, while it induced a marked elevation of free calcium in activin-treated cells. Single channel recording of the membrane patch revealed the existence of ATP-sensitive potassium channel in activin-treated cells. These results indicate that activin A converts amylase-secreting AR42J cells to neuronlike cells. Given that pancreatic endocrine cells possess neuronlike properties and express ATP-sensitive potassium channel as well as neuroendocrine/beta cell-type voltage-dependent calcium channel, activin treatment of AR42J cells may provide an in vitro model system to study the conversion of pancreatic exocrine cells to endocrine cells in islets.

Production of activin A and follistatin in cultured rat vascular smooth muscle cells

Activin A, a member of the transforming growth factor beta supergene family, modulates DNA synthesis in cultured rat vascular smooth muscle cells (VSMC) (Kopma et al. (1993) Exp. Cell. Res. 206, 152-156). In the present study, we studied the production of activin A and follistatin in VSMC. When VSMCs cultured in a 24-well plate were cultured with 10% fetal calf serum (FCS) for 24 h, 0.94 +/- 0.20 pmol/well (mean +/- SE, n = 6) of bioactive activin was released into the culture media. Reverse-transcription polymerase chain-reaction revealed the expression of mRNA for the beta A subunit of inhibin but not for either the beta B or alpha subunit. Bioactivity of activin was increased in quiescent cells treated with FCS or platelet-derived growth factor (PDGF) but not with angiotensin II (Ang II) or insulin-like growth factor-I (IGF-I). Ang II or IGF-I did not stimulate DNA synthesis by itself but, when these two agents were combined, they increased nuclear labeling by 16.4% and release of bioactive activin by 170% of basal. The dose-response relationship and time course study indicated that PDGF-mediated release of activin correlated with initiation of DNA synthesis. Steady state expression of mRNA for the beta A subunit was markedly elevated 12 h after the addition of PDGF and was reduced thereafter. To assess the significance of autocrine activin, the effect of PDGF was determined in the presence and absence of excess of exogenous follistatin. The PDGF-mediated DNA synthesis was enhanced by the addition of excess follistatin.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of ATP-sensitive K+ channel by a non-sulfonylurea compound KAD-1229 in a pancreatic beta-cell line, MIN 6 cell

We studied the mechanism of action of KAD-1229, a non-sulfonylurea compound shown to stimulate insulin secretion, in a glucose responsive insulinoma cell line, MIN 6 cells. In microsomal fraction of MIN 6 cells, KAD-1229 displaced binding of [3H]glibenclamide in a concentration-dependent manner. The dissociation constant and the maximum binding capacity were 0.61 nM and 8.70 pmol/mg.protein, respectively. In inside out configuration of patch-clamp technique, KAD-1229 attenuated the opening of ATP-sensitive K+ channels. The effect of KAD-1229 was detected at 10(-8) M, and 10(-5) M KAD-1229 almost completely blocked the activity of ATP-sensitive K+ channel. When membrane potential was monitored by a perforated mode of patch clamp, KAD-1229 induced depolarization of plasma membrane, which was followed by a burst of action potentials. These action potentials were blocked by cobalt. In a fura-2-loaded single MIN 6 cell, KAD evoked an elevation of intracellular free Ca2+ concentration, [Ca2+]i. The KAD-1229-mediated elevation of [Ca2+]i was attenuated by either removal of extracellular Ca2+ or an addition of nifedipine. Finally, KAD-1229 augmented insulin secretion in MIN 6 cells in a concentration-dependent manner. KAD-1229 also enhanced the effect of glucose and nifedipine inhibited the action of KAD-1229 on insulin secretion. These results indicate that KAD-1229 stimulates insulin secretion by stimulating Ca2+ influx and that, despite the lack of sulfonylurea structure, KAD-1229 binds to sulfonylurea receptors and inhibits the activity of ATP-sensitive K+ channel in MIN 6 cells.

Scintigraphic study on the distribution of radiolabeled cis-diamminedichloroplatinum (II) in the tumor-bearing rabbit: a comparison between intra-arterial injection with lipiodol and intravenous injection

To compare the distribution of cis-diamminedichloroplatinum (II) (CDDP) on scintigraphic images between intra-arterial injection with lipiodol and intravenous injection, we obtained serial scintigraphic images using radiolabeled CDDP (Pt-195m CDDP), which had a high specific activity (7.4 x 10(6) Bq [200 microCi]/mg-CDDP), in the rabbit VX-2 tumor system. A dose of 9.25 x 10(6) Bq (250 microCi) of Pt-195m CDDP was injected at one shot via an ear vein, while 7.4 x 10(6) Bq (200 microCi of Pt-195m CDDP mixed with 1 ml of lipiodol was injected at one shot via a saphenous artery. Mean pixel count, which was corrected for the total dose injected, in the arterially injected tumor always exceeded than that in the intravenously injected tumor. Pt-195m CDDP uptake by the rabbit tumor at 2 hr was 7.8% of the total injected dose with intravenous injection and 16.0% with intra-arterial injection. These data suggest that intra-arterial injection with lipiodol is a more useful method to increase CDDP uptake by tumors than intra-venous injection.

Stimulation of calcium entry is prerequisite for DNA synthesis induced by platelet-derived growth factor in vascular smooth muscle cells

The present study was conducted to determine a role of calcium entry in the growth promoting action of platelet-derived growth factor (PDGF) in cultured rat vascular smooth muscle cells. Addition of PDGF to quiescent cells induced a rapid elevation of cytoplasmic free calcium concentration, [Ca2+]c, followed by a sustained plateau of [Ca2+]c. Removal of extracellular calcium abolished the sustained phase, confirming that PDGF augments calcium entry. When calcium influx rate was determined by measuring initial uptake of [45Ca], PDGF induced a gradual increase in the rate of calcium entry. PDGF-mediated calcium entry became maximal after 90 min of the addition of PDGF, which persisted for at least 8 hrs. Calcium entry induced by PDGF was attenuated by nickel ion but not by a calcium channel blocker, nifedipine. When PDGF-induced calcium entry was blocked for a few hrs by either reducing extracellular calcium or by adding nickel, rate of entrance of S phase was reduced. In particular, VSMC stop progression when calcium entry is blocked in the middle of G1 phase. These results indicate that stimulation of calcium entry is prerequisite for initiation of DNA synthesis induced by PDGF in vascular smooth muscle cells.

Distribution of radiolabeled cis-diamminedichloroplatinum (II) on scintigraphic images in the tumor-bearing rabbit

To evaluate the feasibility of using scintigraphic images to assess the distribution of cis-diamminedichloroplatinum (II) (CDDP), we obtained serial scintigraphic images using radiolabeled CDDP (Pt-195m CDDP), which had high specific activity (7.4 x 10(6) Bq [200 microCi]/mg-CDDP) in the rabbit VX-2 tumor system. Radioactivity at the heart decreased in a biexponential manner, with an initial half-time of 15.3 min and secondary phase of 4.5 days. Time-activity curves revealed that the tumor/heart ratio was greater than 1.0 (1.0-1.1) between 30 min and 4 hr after intravenous injection. The scintigraphic study clearly depicted the tumor. Pt-195m CDDP uptake by the rabbit tumor at 2 hr was 7.8% of the total injected dose. These data suggest that scintigraphic imaging using Pt-195m CDDP is a promising method for imaging tumors and evaluating their CDDP uptake.

Role of calcium entry and protein kinase C in the progression activity of insulin-like growth factor-I in Balb/c 3T3 cells

We previously reported that insulin-like growth factor-I (IGF-I) stimulated calcium entry (Kojima, I., Matsunaga, H., Kurokawa, K., Ogata, E., and Nishimoto, I. (1988) J. Biol. Chem. 263, 16561-16567) and production of 1,2-diacylglycerol in IGF-responsive "primed competent" Balb/c 3T3 cells (Kojima, I., Kitaoka, M., and Ogata, E. (1990) J. Biol. Chem. 265, 16846-16850). The present study was conducted to determine a role of protein kinase C (PKC) in the progression activity of IGF-I. To monitor the activity of PKC in intact cells, we measured phosphorylation of a synthetic KRTLRR peptide, a substrate of PKC, immediately after the permeabilization of the cells with digitonin. When 1 nM IGF-I was added to primed competent cells, KRTLRR peptide phosphorylation was augmented. IGF-I induced more than 2-fold increase in KRTLRR peptide phosphorylation that was blocked by PKC19-36, a pseudosubstrate of PKC, which blocks the activity of the kinase, and Ro31-8220, an inhibitor of PKC. The phosphorylation remained elevated for up to 6 h. To assess the role of PKC in cell cycle progression, IGF-I-induced nuclear labeling was measured in the presence of Ro31-8220. Ro31-8220 reduced the rate of entrance into S phase when added in the first quarter of the G1 phase, but did not affect cell cycle progression when added at the second quarter or later. In contrast, reduction of extracellular calcium completely blocked cell cycle progression when done in the first, second, and third quarter but had no effect in the last quarter. These results indicate that IGF-I persistently activates PKC in primed competent cells, but the activation is required only for the initiation of progression. We conclude that IGF-I promotes cell cycle progression by calcium-dependent mechanisms that are largely independent of PKC.

Modulation of growth of vascular smooth muscle cells by activin A

Activin A is a homodimeric protein structurally related to transforming growth factor-beta. The present study was conducted to examine the effect of activin A on the growth of rat vascular smooth muscle cells (VSMC) in culture. When serum-deprived cells were incubated with activin A, nuclear labeling of bromodeoxyuridine occurred after a 12-h lag period. The effect of activin A on nuclear labeling was dose-dependent, being maximal at 10(-9) M. Activin A also increased the number of VSMC after 30 h of incubation. Insulin-like growth factor-1 (IGF-1) had only a small effect on nuclear labeling by itself but the effects of IGF-1 and activin A were additive. When quiescent VSMC were treated with activin A for 4 h, the effect of subsequent IGF-1 was markedly enhanced. Furthermore, activin A induced an autocrine production of IGF-1 in VSMC. In contrast to these positive effects on cell growth, activin A was rather inhibitory to the action of IGF-1 in activin-primed cells. In addition, activin A inhibited platelet-derived growth factor-induced nuclear labeling. These results indicate that activin A modifies growth of VSMC by complex mechanisms involving autocrine production of IGF-1 and modification of the action of IGF-1.

Activin A inhibits cell-cycle progression induced by insulin-like growth factor-I in Balb/c 3T3 cells

The present study was carried out to examine the effect of activin A on cell-cycle progression induced by insulin-like growth factor-I (IGF-I) in Balb/c 3T3 cells. When activin A was added together with IGF-I to competent cells primed with epidermal growth factor (primed competent cells), both [3H]thymidine incorporation and nuclear labelling induced by IGF-I were inhibited. The inhibition was concentration-dependent and the maximum inhibition was obtained with 1 nmol activin A/1. To ascertain the time in which activin A exerted its inhibitory action, we divided 12 h, the time required for primed competent cells to progress towards the S phase, into four periods and activin A was added during each of the four periods. It was effective when added during either the second (3 to 6 h) or the third period (6 to 9 h) but it did not affect cell-cycle progression when added during the first (0 to 3 h) or the last period (9 to 12 h). We then examined whether activin A affected intracellular events elicited by IGF-I. It did not affect either autophosphorylation of the IGF-I receptor or calcium entry induced by IGF-I. Likewise, it did not cause any change in the radioactivity of 1,2-diacylglycerol (DAG) in cells prelabelled with [3H]myristate while the increase in the mass of DAG induced by IGF-I was markedly reduced by activin A. The dose-response relationship for the activin A-mediated reduction of DAG mass correlated well with th at for the activin A-mediated reduction of DNA synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

[Intraarterial urokinase infusion therapy with superselective catheterization for acute occlusive cerebrovascular disease]

Intraarterial urokinase infusion therapy with superselective catheterization was performed on 11 patients for acute occlusive cerebrovascular disease. The subjects were five men and six women with a mean age of 70 years (range, 48-83 years). Nine of 11 patients had middle cerebral artery occlusion and two had basilar artery occlusion. The interval from onset to infusion ranged from 3.5 to 9 hours, and the total dosage of urokinase from 24 x 10(4) to 150 x 10(4) IU. Recanalization of the occluded artery was achieved in nine patients (82%), and favorable clinical outcome was achieved in seven patients (64%). Six of whom were discharged with no neurologic deficits. Hemorrhagic infarction occurred in two patients without clinical deterioration. Our observations suggest that intraarterial urokinase infusion therapy with superselective catheterization may be very useful in the acute stage of occlusive cerebrovascular disease.

[A case with delayed-onset radiation pneumonitis suspected to be induced by oral etoposide]

Radiation pneumonitis usually occurs within 1-3 months after the completion of radiation therapy. A 63-year-old male with primary lung cancer treated by radiation therapy developed radiation pneumonitis 5 months after the completion of radiation therapy. He received 60 Gy to the lung tumor in a conventional fractionation schedule, and then two courses of intravenous chemotherapy using cis-diamine-dichloroplatinum (II) (110-140 mg) and etoposide (140-175 mg). Oral etoposide was initiated for bone metastases on the 104th day after the completion of radiation therapy at a daily dose of 20 mg, to a total dose of 1075 mg. He complained of fever and exertional dyspnea 5 months after the completion of radiation therapy. Chest radiography showed homogeneous infiltrates in the irradiated lung. These clinical signs and symptoms were refractory to antibiotic therapy, but steroid therapy resulted in marked improvement. The development of radiation pneumonitis was suspected to be induced by oral etoposide, which was given before the onset of radiation pneumonitis. These data suggest that etoposide induces a recall phenomenon, as has been demonstrated with such drugs as adriamycin and actinomycin-D.