Human cerebral acetylcholinesterase activity measured with positron emission tomography: procedure, normal values and effect of age

The regional cerebral metabolic rate of [11C]N-methyl-4-piperidyl acetate, which is nearly proportional to regional cerebral acetylcholinesterase (AChE) activity, was measured by dynamic positron emission tomography in 20 healthy subjects with a wide age range (24-89 years). Quantitative measurement was achieved using a kinetic model which consisted of arterial plasma and cerebral tissue compartments. The plasma input function was obtained using thin-layer chromatography and an imaging phosphor plate system at frequent sampling intervals to catch the rapid metabolism of the tracer in the blood. The distribution of the rate constant k3, an index of AChE activity, agreed well with reported post-mortem AChE distribution in the cerebral cortex (0.067-0.097 min-1) and thalamus (0.268 min-1), where AChE activity was low to moderate. The k3 values in the striatum and cerebellum, where AChE activity was very high, did not respond linearly to AChE activity because of increased flow dependency. No significant effect of age was found on AChE activity of the cerebral cortex, suggesting that the ascending central cholinergic system is preserved in normal aging. This study has shown that quantitative measurement of enzyme activity in the living brain is possible through appropriate modelling of tracer kinetics and accurate measurement of the input function. The method should be applicable to patients with Alzheimer's disease and those with other kinds of dementia whose central cholinergic system has been reported to be disturbed.

Enhanced absorption of cyclosporin A by complexation with dimethyl-beta-cyclodextrin in bile duct-cannulated and -noncannulated rats

The enhancing effects of dimethyl-beta-cyclodextrin (DM-beta-CyD) on the absorption of cyclosporin A (CsA) after oral administration to rats under bile duct-cannulated and -noncannulated conditions were investigated. The dissolution rate of CsA was markedly augmented by complexation with DM-beta-CyD. In a closed loop in situ study, DM-beta-CyD considerably increased the cumulative amounts of CsA in the mesenteric venous blood after injection of the aqueous CsA suspension into the small intestinal sac of rats. In addition, the cumulative amount ratio of M1, the dominant metabolite of CsA in rats, to CsA in the mesenteric venous blood for up to 40 min after the injection of the CsA-DM-beta-CyD suspension into the sac was lower than that of the CsA suspension alone. DM-beta-CyD inhibited the bioconversion of CsA in the small intestinal microsomes of rats. These results indicate that the bioconversion of CsA was abated by complexation with DM-beta-CyD. An in vivo study revealed that DM-beta-CyD increased the transfer of CsA to blood, not lymph, with low variability in the absorption after oral administration of the CsA suspension to rats. The variability of bioavailability of DM-beta-CyD complex was lower than that of Sandimmune, although the extent of bioavailability of DM-beta-CyD was only a little higher than that of Sandimmune. The bioavailability of CsA or its DM-beta-CyD complex was appreciably decreased by the cannulation of the bile duct of rats, and the extent of the lowering in the bioavailability in the presence of DM-beta-CyD was much less serious than that of CsA alone. The present results suggest that DM-beta-CyD is particularly useful in designing oral preparations of CsA with an enhanced bioavailability and a reduced variability in absorption.

1-Methyl-4-phenylpyridinium ion (MPP+) selectively inhibits the replication of mitochondrial DNA

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine is known to cause Parkinsonism in its neurotoxic form, 1-methyl-4-phenylpyridinium ion (MPP+). We have previously reported that MPP+ decreases the content of mitochondrial DNA (mtDNA) independently of the inhibition of complex I in human cells [Miyako, K., Kai, Y., Irie, T., Takeshige, K., and Kang, D. (1997) J. Biol. Chem. 272, 9605-9608]. Here we study the mechanism causing the decrease in mtDNA. MPP+ inhibits the incorporation of 5-bromo-2'-deoxyuridine into mtDNA but not into nuclear DNA, indicating that MPP+ inhibits the replication of mtDNA but not that of the nuclear genome. The replication of mtDNA is initiated by the synthesis of the heavy strand switched from the transcription of the light strand. MPP+ decreases the nascent heavy strands per mtDNA and increases the transcript of the ND6 gene, encoded on light strand, per mtDNA. The amount of mitochondrial transcription factor A is not decreased. These data suggest that the transcription is not inhibited and therefore the transition from transcription to replication of mtDNA is lowered in the MPP+-treated cells. Electron microscopy shows that the number of mitochondria is not decreased in the MPP+-treated cells, suggesting that MPP+ does not affect the overall biogenesis of mitochondria. Thus, MPP+ selectively inhibits the replication of mtDNA.

[Clinical outcomes in low grade follicular lymphoma]

Twenty-six patients with follicular small-cleaved lymphoma (FSCL) and 16 patients with follicular mixed lymphoma (FML) were treated at the Nichidai Itabashi Hospital between 1981 and 1995. The 5-year overall survival rate was 74.3% and 70.0% for the FSCL and FML patients, respectively. Of the patients with stage III-IV FSCL, 9 were assigned to a "watchful waiting" follow-up course and 13 were treated with a single alkylating agent or CHOP therapy. The 5-year failure-free survival rate was 66.7% and 33.0%, respectively. Of the patients with stage II-IV FML, 6 were treated with CHOP or MACOP-B protocol. The complete response rate for this group was only 33.3%, and none of the patients were in remission for more than 2 years. Histological transformation into diffuse aggressive lymphoma was observed in 7 patients, with the median time from diagnosis to transformation at 50 months. Three of those patients were successfully treated with intensive chemotherapy after transformation.

Residual disease and presence of human papillomavirus after conization

The objective of this study was to evaluate the incidence of residual disease and the presence of human papillomavirus (HPV) after conization. Data on 53 patients with carcinoma in situ or microinvasive carcinoma who underwent hysterectomy less than 2 months after conization were examined. Seven of 53 patients (13%) had positive margins. In 4 of these 7 patients (57%), residual disease was found in the postconization hysterectomy specimen. Two of 46 patients (4%) with negative margins also had residual disease. HPV DNA was detected by PCR in 27 of 53 conization specimens and in 2 postconization hysterectomy specimens. Of 2 patients, 1 did not have residual disease. Residual disease could be present even with a negative conization margin, and HPV DNA may be found in a histologically normal cervix after conization.

Role of neutrophil elastase in stress-induced gastric mucosal injury in rats

Activated neutrophils play an important role in tissue injury by releasing various inflammatory mediators capable of damaging endothelial cells. To investigate whether neutrophil elastase (NE) is involved in stress-induced gastric mucosal injury, we examined the effects of 2 NE inhibitors (ONO-5046 and L-658 758) as well as nitrogen mustard-induced leukocytopenia on the formation of gastric mucosal lesions, gastric mucosal blood flow, gastric mucosal microvascular permeability, and gastric neutrophil accumulation in rats subjected to water immersion-restraint stress (WIR). Gastric mucosal injury peaked 8 hours after WIR. Gastric mucosal blood flow, as measured by laser-Doppler flow cytometry, decreased to 45% of its initial level 8 hours after WIR. Gastric mucosal microvascular permeability, evaluated by Evans blue dye leakage to the gastric mucosa, showed an increase, peaking 8 hours after WIR. Gastric accumulation of neutrophils, determined by measuring gastric myeloperoxidase activity and by histologic examination, was also significantly increased 8 hours after WIR. Both of the NE inhibitors markedly prevented the formation of gastric mucosal lesions. They also decreased the reduction in gastric mucosal blood flow seen in animals subjected to WIR while preventing increases in gastric mucosal microvascular permeability. Gastric neutrophil accumulation was significantly reduced in animals given either inhibitor 8 hours after WIR. Leukocytopenia produced effects similar to those produced by the inhibitors. Taken together, these observations strongly suggest that NE promotes stress-induced gastric mucosal injury in rats by reducing gastric mucosal blood flow and increasing neutrophil accumulation.

The metabolic pathway of visual pigment chromophore formation in Drosophila melanogaster--all-trans (3S)-3-hydroxyretinal is formed from all-trans retinal via (3R)-3-hydroxyretinal in the dark

Carotenoid-depleted fruit flies, Drosophila melanogaster, were reared on yeast/glucose medium containing lipid-depleted white corn grits and cholesterol. After rearing for more than a year, the yield of flies remained constant and the content of 3-hydroxyretinal in a head was three logarithmic units less than that of normal flies reared on medium containing yellow corn grits. When all-trans retinal was supplied as the sole source of retinoids, the flies formed and accumulated all-trans 3-hydroxyretinal in the dark. To examine the metabolic pathway to produce (3S)-3-hydroxyretinal in Drosophila, all-trans retinal was supplemented for two hours to carotenoid-depleted flies in the dark, and the subsequent changes in the composition of 3-hydroxyretinal enantiomers were analyzed using a chiral column on HPLC. The results indicated initial formation of (3R)-3-hydroxyretinal followed by isomerization into the 3S enantiomer. In another set of experiments, the membrane fraction was obtained from the head homogenate of retinoid-depleted flies and an in vitro assay of 3-hydroxyretinal formation from retinal was performed. The 3-hydroxyretinal produced was the 3R enantiomer, supporting the result obtained from the in vivo experiment whereby (3S)-3-hydroxyretinal is produced from retinal via (3R)-3-hydroxyretinal. Addition of NADPH enhanced 3-hydroxyretinal formation and the presence of carbon monoxide inhibited it, suggesting that hydroxylation at the C3 position of retinal occurred via the monooxygenase activity of cytochrome P-450.

A newly developed adenovirus-mediated transfer of a wild-type p53 gene increases sensitivity to cis-diamminedichloroplatinum (II) in p53-deleted ovarian cancer cells

A new recombinant adenovirus carrying a wild-type p53 gene (AxCAp53) was developed and the combination effect of p53 gene transfer and cis-diamminedichloroplatinum (II) (CDDP) was examined in an ovarian cancer cell line, SK-OV-3, with deletion of the p53 gene. AxCAp53 showed a high efficiency of gene transduction and increased sensitivity to CDDP in the SK-OV-3 cells. It was found that the sensitivity of the cells to CDDP correlated with the amount of infectious units of virus per cell of AxCAp53 which correlated with p53 protein expression. The results suggest that the combination of CDDP and AxCAp53 may be a potential strategy for the therapy of CDDP-resistant ovarian cancer.

Design and evaluation of an osmotic pump tablet (OPT) for prednisolone, a poorly water soluble drug, using (SBE)7m-beta-CD

PURPOSE

The purpose of this study was to develop a controlled-porosity osmotic pump tablet (OPT) for poorly water soluble drugs using a sulfobutyl ether-beta-cyclodextrin, (SBE)7m-beta-CD or Captisol, which acted as both a solubilizer and as an osmotic agent.

METHODS

Prednisolone (PDL) was chosen as a model drug for this study. The release of PDL from osmotic pump devices and tablets was studied. In vivo absorption of PDL from OPT was evaluated in male beagle dogs.

RESULTS

PDL release from the osmotic pump tablet with (SBE)7m-beta-CD was complete. Another cyclodextrin, hydroxypropyl-beta-cyclodextrin (HP-beta-CD), and a sugar mixture of lactose and fructose resulted in incomplete release. Although PDL release from the OPT with (SBE)7m-beta-CD and the sugar formulation displayed mainly zero-order release characteristics, the tablet utilizing HP-beta-CD showed apparent first-order release characteristics. An in vivo absorption study in dogs correlated very well with the in vitro release profiles using the Japanese Pharmacopoeia dissolution method.

CONCLUSIONS

The present results confirm that (SBE)7m-gamma-CD can serve as both the solubilizer and the osmotic agent for OPT of PDL, and modify the input rate of PDL without compromising oral bioavailability.

Design, synthesis and evaluation of transition-state analogue inhibitors of Escherichia coli gamma-glutamylcysteine synthetase

Phosphinic acid-, sulfoximine- and sulfone-based transition-state analogues were synthesized and evaluated as inhibitors of Escherichia coli gamma-glutamylcysteine synthetase. These compounds have a carboxyl function at the beta-carbon to the tetrahedral central hetero atom so as to mimic the carboxyl group of the attacking cysteine in the transition state. The phosphinic acid- and the sulfoximine-based compounds were found to be potent ATP-dependent inactivators, both showing a slow-binding kinetics with overall affinities and second-order inactivation rates of one to two orders of magnitude greater than those of L-buthionine (SR)-sulfoximine (L-BSO). The sulfone was a simple reversible inhibitor without causing ATP-dependent enzyme inactivation, but its affinity toward the enzyme was still five times greater than that of L-BSO, indicating that the beta-carboxyl function plays a key role in the recognition of the inhibitors by the enzyme. The sulfoximine with (S)-beta-carbon to the sulfur was synthesized stereoselectively, and the two diastereomers with respect to the chiral sulfur atom were separated as a cyclic sulfoximine derivative. The sulfoximine with R-configuration around the sulfur served as an extremely powerful ATP-dependent inactivator with an overall inhibition constant of 39 nM and an inactivation rate of 6750 M-1 s-1, which correspond to 1260-fold higher affinity and almost 1400-fold greater inactivation rate as compared with L-BSO. The sulfoximine with (S)-sulfur was a simple reversible inhibitor with an inhibition potency comparable to that of the sulfone. The synthesis and inhibition profile of the N-phosphoryl sulfoximine is also described.

Chloride concentration in cultured hippocampal neurons increases during long-term exposure to ammonia through enhanced expression of an anion exchanger

The effects of long-term exposure to ammonia on [Cl-]i in cultured hippocampal neurons were examined. Ammonia increased the [Cl-]i time- (>/=24 h) and concentration- (>/=2 mM) dependently, resulting in a depolarizing shift of the equilibrium potential of the GABAA receptor-Cl- channel opening (EGABA). Such an effect of ammonia was diminished by the inhibitors of Cl-/HCO3- exchangers, 0.1 mM 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS) and 0.1 mM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), and a carbonic anhydrase inhibitor, 2 mM acetazolamide, but not by a Na+/K+/2Cl-cotransport inhibitor, 50 microM bumetanide, suggesting an enhanced Cl-/HCO3- exchange activity by ammonia. The ammonia-induced increase in [Cl-]i was also abolished by the inhibitors of protein kinase C (PKC), 0.1 microM calphostin C and 10 microM 1-(5-isoquinolinyl-sulfonyl)-2-methylpiperazine dihydrochloride (H-7), and of transcription and de novo protein synthesis, 1 microM actinomycin D and 0.5 microg/ml cycloheximide, while a PKC activator, 0.1 h microM phorbor 12-myristate 13-acetate (PMA), increased the [Cl-]i. The mRNA level of the AE3 Cl-/HCO3- exchanger was increased by ammonia in a calphostin C- and H-7-sensitive manner. The AE3-like immunoreactivity was also increased by ammonia. These findings suggest that long-term exposure to ammonia increases the expression of AE3 through the activation of PKC, resulting in an increase in [Cl-]i in neurons and a reduction of inhibitory postsynaptic potentials.

Radical surgery following neoadjuvant chemotherapy for patients with stage IIIB cervical cancer

BACKGROUND

We conducted a phase II trial of radical surgery following neoadjuvant chemotherapy in patients with stage IIIB cervical cancer.

METHODS

A total of 26 patients with stage IIIB cervical cancer were entered in this study. Patients were treated with a chemotherapeutic regimen consisting of intraarterial infusion of cisplatin and intravenous infusion of other anticancer agents, to a maximum of 3 courses. If the results of the evaluation indicated that surgery was feasible, radical surgery, including complete removal of pelvic vessels, partial resection of adjacent organs, and pelvic and paraaortic lymphadenectomy, was performed. Patients whose tumors showed no response received radiotherapy. We evaluated operability, survival rate, toxicities, and complications. Additionally, we examined prognostic variables by multivariate analysis in the patients treated by radical surgery.

RESULTS

Eighteen patients (69.2%) underwent radical surgery. The remaining eight patients received radiation therapy. The 3-year disease-free survival rate was 72.2% in patients who received surgery and 25.0% in those who received radiotherapy. Multivariate analysis did not show any independent prognostic factors in the patients who underwent surgery.

CONCLUSION

Radical surgery following neoadjuvant chemotherapy may be feasible in two thirds of patients with stage IIIB cervical cancer; therefore, phase III trials can be recommended.

[Pharmaco-dynamic influence under ascites or laparotomy on intraperitoneal sequential MTX/5-FU therapy]

We studied pharmaco-dynamic changes of intraperitoneal sequential MTX (30 mg)/5-FU (750 mg) therapy in gastric cancer patients with malignant ascites and those who had undergone a gastrectomy. The serum and ascites levels of MTX in patients with malignant ascites decreased much slower than in patients without ascites. In patients with ascites, the serum MTX concentration peaked 8 hours later and then gradually decreased. The ascites MTX level decreased as low as 1/10 2 days after the intraperitoneal administration. The serum and ascites 5-FU levels revealed a minor prolongation of 5-FU concentration in patients with ascites. Gastrectomy did not affect the pharmaco-dynamics of MTX in post-operative patients with sequential intraperitoneal administration of MTX/5-FU on 1, 8 and 15 POD.

[Usefulness of CO2 US angiography in treating hepatocellular carcinoma]

We evaluated the usefulness of CO2 US angiography in the detectability of and the effectiveness of TAE and/or PEIT for hepatocellular carcinoma (HCC). Twenty-three patients with HCC underwent CO2 angiography during the interventional procedure to treat HCC after examination of CT and conventional US. CO2 US angiography was observed on the US monitor by injecting CO2 microbubbles through a catheter placed in the hepatic artery. Contrast materials for CO2 US angiography were 3 ml of CO2 microbubbles prepared by vigorously mixing 3 ml of normal saline with 3 ml of 20% Intralipid, 3 ml of 20% albumin or 3 ml of the patient's own blood. In all patients, CO2 US angiography revealed equal or superior tumor detectability as compared with CT, conventional US and angiography. For demonstrating the inner structure of HCC, the image of CO2 microbubbles mixed with Intralipid was better than that of CO2 microbubbles mixed with albumin. In 9 of 23 patients, CO2 US angiography depicted nodules that had not been seen in the other images. TAE was performed in 21 patients with HCC who showed hypervascularity. In one patient in whom it was difficult to clearly depict the small lesion of HCC by conventional angiography and US, PEIT was successful under CO2 US angiography. The detectability of HCC was higher in CO2 US angiography than in CT, conventional US or angiography. The distribution of blood supply to HCC was observed easily by CO2 US angiography. In TAE of HCC, CO2 US angiography was useful to determine the dose of embolization materials without having to perform repeated angiography. It was possible to perform PEIT easily for non-detectable tumors without CO2 US angiography. CO2 US angiography was useful to evaluate the stage of HCC and to perform TAE and PEIT.

Blood pressure lowering effect of low intensity aerobic training in elderly hypertensive patients

PURPOSE

The purpose of this investigation was to determine the effect of 9 months of low intensity aerobic training on blood pressure in elderly hypertensive patients who were receiving antihypertensive medication.

METHODS

The training group (N = 13; mean age 75.4 +/- 5.4 yr) agreed to take part in physical training using a treadmill with an exercise intensity at the blood lactate threshold (LT) for 30 min three to six times a week for 9 months. The rest (N = 13; mean age 73.1 +/- 4.2 yr) served as controls.

RESULTS

The resting systolic (-15 +/- 8 mm Hg), mean (-11 +/- 6 mm Hg), and diastolic blood pressures (-9 +/- 9 mm Hg) decreased significantly after 3 months of training and the blood pressure of all participants stabilized at a significantly lower level by the end of the study (9 months) in the training group, whereas no significant changes in blood pressure were found in the control group. Both the pretraining systolic and diastolic blood pressure of those recruited patients negatively correlated with those changes after the training (SBP: P < 0.01; DBP: P < 0.05, respectively). After 1 month of detraining in five patients, the blood pressure levels were similar to those in the pretraining state. The LT increased significantly in the training group (P < 0.01).

CONCLUSION

In conclusion, an additional antihypertensive effect of mild aerobic training at the LT was confirmed in elderly patients receiving antihypertensive medication. The cessation of such training in five patients, however, resulted in a relatively rapid return to pretraining levels within a month.

Breast masses: color Doppler, power Doppler, and spectral analysis findings

PURPOSE

To determine the diagnostic efficacy of power Doppler sonography (PDS) with spectral analysis for breast diseases, we retrospectively compared PDS and color Doppler sonography (CDS) in patients with breast lesions.

METHODS

One hundred thirty-eight women with palpable breast lesions were examined with PDS (65 women) and/or CDS (73 women). We calculated peak velocity, end-diastolic velocity, pulsatility index (PI), and resistance index (RI).

RESULTS

On a 4-point subjective visual vascularity scale, PDS demonstrated higher vascularity than did CDS. Although smaller and more subtle vessels could be detected only with PDS, the PI and RI differed significantly between malignant and benign lesions when either PDS or CDS was used. However, logistic regression analysis showed that high PI and RI were associated with malignancy only when CDS was used. When PDS was used, PI was significantly higher in invasive ductal carcinomas with fibrous stroma and ill-defined margins (associated with a poor prognosis) than in invasive ductal carcinomas without fibrous stroma or with well-defined margins.

CONCLUSIONS

Doppler spectral analysis of malignant breast lesions using PDS may contribute to the determination of prognosis.

Does potassium ion concentration affect lung preservation?

To evaluate the influence of potassium ion concentration in an organ preservation solution on lung preservation, four types of solutions were produced. These preservation solutions consisted of sodium and potassium ions on the cation and phosphate ions on the anion with glucose. Contents of solutions were: (1) 155 mmol/l Na+, 0 mmol/l K+; (2) 150 mmol/l Na+, 5 mmol/l K+; (3) 20 mmol/l Na+, 135 mmol/l K+; and (4) 0 mmol/l Na+, 155 mmol/l K+. All four solutions possessed the same osmolarity, the same pH in the same temperature, and the same buffer action. Lungs were preserved at 7 degrees C in these solutions for 24 h and evaluated in a rat lung perfusion system with perfluorochemical emulsion. Pressure-limited perfusions with pressure-limited ventilation were carried out for 20 min before and after preservation. Thereafter, the recovery ratios of pulmonary arterial flow (Q), tidal volume (VT), oxygen tension of the pulmonary venous effluent (PPVO2), and wet-to-dry ratios were compared. The recovery ratios of Q were better in low, but not zero, potassium solutions, whereas wet-to-dry ratios were kept lower in high potassium solutions. No difference in pulmonary compliance or gas exchange was observed against a great change in potassium ion concentration. Therefore, the potassium ion concentration did not play a major role in lung preservation.

Glucose and methionine uptake by rat brain tumor treated with prodrug-activated gene therapy

The effect of acyclovir (ACV) on the metabolism of rat 9L-gliosarcoma cells expressing the herpes simplex virus-thymidine kinase gene was studied using 2-deoxy-2-[18F]fluoro-D-glucose (FDG) and L-[methyl-11C]methionine. Though the average weight of the tumors treated with ACV was significantly lower than that of the saline-injected control group, FDG and methionine uptake per weight of tumor tissue was not different between the two groups. This result exhibits a striking contrast to the metabolic pattern observed after radiation therapy, suggesting the different pathways regarding tumor cell death between the therapies.

Cloning and characterization of the gene encoding the iron-sulfur protein of succinate dehydrogenase from Pleurotus ostreatus

Genomic and cDNA fragments encoding the iron-sulfur protein (Ip) subunit of dehydrogenase (EC 1.3.99.1) have been cloned from the edible basidiomycetous fungus, Pleurotus ostreatus. The gene is interrupted by five introns and is predicted to encode a polypeptide of 268 amino acid residues. Sequence comparison with the Ip subunit from other species identified three conserved cysteine-rich clusters. One of these contains a critical histidine residue implicated in carboxin sensitivity in the heterobasidiomycete Ustilago maydis.

Homogeneous assay for measuring low-density lipoprotein cholesterol in serum with triblock copolymer and alpha-cyclodextrin sulfate

We have developed a fully automated method for measuring LDL-cholesterol (LDL-C) in human serum without the need for prior separation, using a nonionic surfactant, polyoxyethylene-polyoxypropylene block copolyether (POE-POP), and a sodium salt of sulfated cyclic maltohexaose, alpha-cyclodextrin sulfate. Of the surfactants tested, POE-POP with a higher molecular mass of the POP block and a greater hydrophobicity reduced the reactivity of cholesterol in lipoprotein fractions; the reactivity in descending order was LDL >> VLDL > chylomicron approximately HDL. Gel filtration chromatographic studies revealed that POE-POP removed lipids selectively from the LDL fraction and allowed them to participate in the cholesterol esterase-cholesterol oxidase coupling reaction system. By contrast, alpha-cyclodextrin sulfate reduced the reactivity of cholesterol, especially in chylomicrons and VLDL. A combination of POE-POP with alpha-cyclodextrin sulfate provided the required selectivity for the determination of LDL-C in serum in the presence of magnesium ions and a small amount of dextran sulfate without precipitating lipoprotein aggregates. There was a good correlation between the results of LDL-C assayed by the proposed method and the beta-quantification reference method involving 161 sera with triglyceride concentrations ranging from 0.3 to 22.6 mmol/L.

Effects of protein kinase and phosphatase inhibitors on slow shortening of guinea pig cochlear outer hair cells

The intracellular mechanisms of slow shortening in isolated guinea pig cochlear outer hair cells were investigated using inhibitors and/or an activator of protein kinases and protein phosphatases. The slow shortening was induced by tetanic electrical field stimulation, and changes in the cell length, volume and intracellular Cl- concentration were microscopically monitored using a chloride-sensitive fluorescent dye. The slow shortening was inhibited by a calmodulin inhibitor, W-7, and a calcium calmodulin-dependent protein kinase II (CaMKII) inhibitor, KN-62. The inhibition by W-7 or KN-62, was abolished by the supplemented conductance of K+ with valinomycin. Among the protein phosphatase inhibitors tested, a type 1 and 2A protein phosphatase inhibitor, calyculin A, inhibited the slow shortening. The inhibition by calyculin A was abolished by the increased Cl- permeability, but neither by the increased K+ conductance with valinomycin nor by the increased Ca2+ conductance with A23187. A protein serine/threonine phosphatase activator, N-acetylsphingosine, inhibited the shortening, which was abolished by either valinomycin or a type 2A protein phosphatase inhibitor, okadaic acid, but not by calyculin A. These findings suggest the following signaling mechanisms in the slow shortening of outer hair cells; the K+ channel opening is facilitated through protein phosphorylation by CaMKII and suppressed via okadaic acid-sensitive dephosphorylation, and the Cl- channel opening depends on calyculin A-sensitive protein phosphatase activity.