Expression of a soybean nodule-enhanced phosphoenolpyruvate carboxylase gene that shows striking similarity to another gene for a house-keeping isoform

Three different cDNAs for phosphoenolpyruvate carboxylase (PEPC) were isolated from soybean root nodules. The full-length cDNA of the most abundant isoform (GmPEPC7) was very similar to another one (GmPEPC15), the nucleotide sequence of which is identical to that of a reported clone (gmppc1) (Vazquez-Tello, A., Whittier, R.F., Kawasaki, T., Sugimoto, T., Kawamura, Y. and Shibata, D. (1993) Plant Physiol. 103, 1025-1026). In the coding region, the newly isolated GmPEPC7 and the previously reported were gmppc1 99% and 98% identical at the amino acid and nucleotide levels, respectively. In contrast, they exhibited only 39% identity in the 3' non-coding region, indicating that they are encoded by distinct genes. Northern blot analysis with 3' non-coding regions as isoform-specific probes showed that GmPEPC7 is nodule-enhanced whereas GmPEPC15 (gmppc1) is expressed in most soybean tissues. The third clone (GmPEPC4) was much less homologous to the above two clones and thus was not further characterized. It was also shown by in situ hybridization that the nodule-enhanced isoform is expressed in all cell types in nodules, including in Bradyrhizobium-infected and uninfected cells and cortical cells. A relatively strong hybridization signal was detected in the vascular bundle pericycle. Southern blot analysis indicated that there are only two PEPC genes exhibiting a high degree of similarity in the soybean genome, one for the nodule-enhanced GmPEPC7 and the other for the constitutively expressed gmppc1. A phylogenetic tree based on the amino acid sequences of soybean PEPCs and nodule-enhanced PEPCs of alfalfa and pea suggested that the soybean nodule-enhanced isoform evolved from the housekeeping PEPC gene after the ureid-translocating and amide-translocating legumes diverged from each other.

cDNA cloning of squalene synthase genes from mono- and dicotyledonous plants, and expression of the gene in rice

cDNA clones encoding squalene synthases were isolated from rice, maize and soybeans. A phylogenetic tree showed that the enzymes of monocots and dicots form distinct subgroups. In rice, squalene synthase mRNA was detected in tissues containing dividing cells and its level was repressed by illumination.

Influence of highly purified eicosapentaenoic acid ethyl ester on insulin resistance in the Otsuka Long-Evans Tokushima Fatty rat, a model of spontaneous non-insulin-dependent diabetes mellitus

We investigated the effect of long-term administration of highly purified eicosapentaenoic acid ethyl ester (EPA-E), an n-3 polyunsaturated fatty acid derived from fish oil, in comparison to the effects of lard, olive oil, safflower oil, or distilled water as the control on the development of insulin resistance in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of spontaneous non-insulin-dependent diabetes mellitus (NIDDM) with obesity. After 17 or 18 weeks of treatment, the glucose infusion rate (GIR) in the euglycemic insulin-glucose clamp test only showed a significant increase in EPA-E-treated rats compared with control rats given distilled water alone as the vehicle. The GIR in EPA-E-treated animals was approximately three times greater than in the controls. This is the first report to display the influence of various fatty acids on the development of insulin resistance in OLETF rats. We demonstrated that EPA-E prevents the onset of insulin resistance, whereas olive oil and safflower oil have no effect and lard exacerbates insulin resistance. Fatty acid analysis of phospholipids in skeletal muscle showed a significant increase of the C18:2, C20:5, and C22:5 components in EPA-E-treated rats and, conversely, a significant decrease in C20:4. In addition, EPA-E-treated rats showed a significant increase in GLUT4 mRNA in skeletal muscle when compared with control rats. Our results indicate that the beneficial effect of EPA-E on insulin resistance in OLETF rats is likely to be dependent on modification of the phospholipid components of the skeletal muscle membrane. These findings suggest that dietary fatty acids may play a key role in the development of insulin resistance in patients with NIDDM.

Pirfenidone prevents collagen accumulation in the remnant kidney in rats with partial nephrectomy

Pirfenidone (PFD) is a new compound that prevents and even reverses the extracellular matrix accumulation in several organs as shown by experimental and clinical studies. In the present study, we examined the effect of PFD (500 mg/kg daily in the food) on the progression of chronic renal failure (CRF) in the 5/6 nephrectomy rat model. Proteinuria progressively increased in rats with renal ablation (C) at 12 weeks. Urinary protein excretion in PFD-treated rats (P) was numerically lower than C, but the difference did not reach statistical significance. In contrast, in the chronic phase, PFD improved renal function and reduced collagen accumulation detected by hydroxyproline content (OH-Pro) in the cortex of the remnant kidney. Although creatinine clearance decreased with time in C, the values in P were significantly better at 10 and 12 weeks. The OH-Pro in C at 12 weeks was significantly higher than that of no-ablation, sham-operated rats, whereas OH-Pro in CRF was lower in (P). Expression of mRNA for type IV and I collagen in the cortex also increased in C, but it was inhibited in (P). To study the role that TGF-beta plays in the regulatory process following CRF, we examined the expression of TGF-beta mRNA in this model. Levels of cortical TGF-beta mRNA in C were significantly elevated at 12 weeks. The increase was suppressed by PFD. These results demonstrate that PFD attenuates the development of CRF by preventing collagen accumulation in this model, and suggest that PFD can be clinically useful for treating CRF.

Effects of site-directed mutagenesis of conserved Lys606 residue on catalytic and regulatory functions of maize C4-form phosphoenolpyruvate carboxylase

Lys606, one of the two highly conserved lysine residues in maize C4-form phosphoenolpyruvate carboxylase (PEPC), was converted to Asn, Glu or Arg by site-directed mutagenesis. Resulted mutant enzymes expressed using pET system [Dong, L.-Y. et al. (1997) Biosci. Biotech, Biochem. 61:545] were purified by one step procedure through nickel-chelate affinity chromatography to a purity of about 95%. The replacement of Lys606 by Arg had little effect on the kinetic and allosteric properties of the resulting mutant enzyme. In contrast, the maximum velocities (Vmax) were decreased to 22% and 2% of that of wild-type PEPC upon the substitution of Lys606 by Asn and Glu, respectively. The value of S0.5(HCO3-) was increased 21-25 fold by the replacements, whereas the S0.5(Mg2+) and S0.5(PEP) values were increased only 5-8 fold. The extents of activation of mutant enzymes by glucose 6-phosphate and glycine were 2 to 3-fold higher than those of wild-type enzyme. The mutant enzymes showed less sensitivity to malate inhibition, compared with the wild-type enzyme. The results suggested that the Lys606 is not obligatory for the enzyme activity, but may be involved in the bicarbonate-binding and contribute somehow to the allosteric regulatory properties.

Regulatory phosphorylation of plant phosphoenolpyruvate carboxylase: role of a conserved basic residue upstream of the phosphorylation site

In order to mimic regulatory phosphorylation of the Ser-15 of maize C4-form phosphoenolpyruvate carboxylase (PEPC), we replaced Ser-15 and Lys-12 with Asp (S15D) and Asn (K12N), respectively, by site-directed mutagenesis. Although both mutant enzymes were catalytically as active as the wild-type PEPC, they showed much less sensitivity to malate, an allosteric inhibitor, similarly to the phosphorylated wild-type PEPC. A maize protein kinase of 30 kDa which is known to be specific to PEPC (PEPC-PK), phosphorylated K12N as well as the wild-type PEPC but not S15D. The phosphorylation of K12N further diminished the sensitivity to malate. Thus, a positive charge of the conserved Lys-12 is not required for the recognition by PEPC-PK but contributes to the intrinsic sensitivity to malate inhibition.

Interleukin-2 modulates the responsiveness to angiotensin II in cultured vascular smooth muscle cells

Preincubation with interleukin-2 (IL-2), a T cell-derived cytokine, enhanced the increase in intracellular Ca2+ ([Ca2+]i) induced by angiotensin II (AII) in vascular smooth muscle cells (VSMC). IL-2 itself did not affect the basal [Ca2+]i level or the maximal response of [Ca2+]i increase induced by AII. Furthermore, IL-2-induced enhancement was not observed in the absence of extracellular Ca2+, suggesting that IL-2 enhances Ca2+ influx induced by AII. IL-2 also enhanced the stimulation of DNA synthesis induced by AII, although IL-2 alone did not stimulate DNA synthesis. Genistein, an inhibitor of protein tyrosine kinases, significantly inhibited IL-2-induced enhancement of both Ca2+ influx and DNA synthesis induced by AII. A neutralizing antibody against heparin-binding epidermal growth factor-like growth factor (HB-EGF) partially inhibited IL-2-induced enhancement of DNA synthesis induced by AII. These findings suggest that autocrine HB-EGF is partially involved in the mechanism of IL-2-induced enhancement of DNA synthesis. On the other hand IL-2 stimulated both glycosaminoglycan (GAG) and prostacyclin syntheses and enhanced the stimulation of both GAG and prostacyclin syntheses induced by AII. Therefore, IL-2 may play important roles in the pathogenesis of atherosclerosis and vascular disease by modulating the responsiveness to AII in VSMC.

Determination of simvastatin and its active metabolite in human plasma by column-switching high-performance liquid chromatography with fluorescence detection after derivatization with 1-bromoacetylpyrene

By using a fluorescent derivatization and column-switching technique, a highly sensitive and selective high-performance liquid chromatographic (HPLC) method has been developed for the determination of simvastatin (I, beta-hydroxy-delta-lactone form) and its active hydrolyzed metabolite (II, beta,delta-dihydroxy acid form of I) in human plasma. A plasma sample spiked with internal standards was applied to a C8 solid-phase extraction column. Compounds I and II were separately extracted from plasma into two fractions. Compound I in one of the fractions was hydrolyzed to II. A fluorescent derivative was prepared by esterification of II with 1-bromoacetylpyrene in the presence of 18-crown-6 for both fractions. The pyrenacyl ester of II thus obtained was purified on a phenylboronic acid (PBA) solid-phase extraction column, and was measured by column-switching HPLC with fluorescence detection. The calibration curves for both I and II were linear in the concentration range of 0.1-10 ng/ml. The intra-day coefficients of variation were less than 11.0%, and the accuracies were between 91.7% and 117% within the concentration range for both analytes. The limits of quantification (LOQ) for both analytes were set to 0.1 ng/ml. This assay method has adequate sensitivity and selectivity to measure the concentrations of I and II in human plasma from clinical studies.

[Mantle cell lymphoma with multiple extranodal involvement]

A 79-year-old male was admitted to our hospital because of general fatigue and night sweat. Physical examination showed generalized superficial lymphadenopathy, marked splenomegaly, and tumors in the conjunctiva and the abdomen. Chest X-ray and computed tomography (CT) revealed pleural effusion and intrathoracic lymphadenopathy. Abdominal ultrasonography and CT showed hepatosplenomegaly and intraperitoneal tumors. Upper gastrointestinal fiberscopy revealed multiple polypoid lesions and ulcers in the duodenum and the stomach. Involvement of relatively small-sized lymphocytes with cleaved nuclei was identified in each biopsied specimen from a cervical lymph node, a tumor in the conjunctiva, gastrointestinal polypoid lesions, and the bone marrow. Surface marker analysis of abnormal lymphocytes in the bone marrow revealed that CD5, CD19, and CD20 were strongly positive, but CD23 was weakly positive. Although (11:14)(q13:q32) translocation was not identified by chromosome analysis of bone marrow cells, Northern blot analysis of bone marrow cells revealed overexpression of the PRAD1 oncogene. Diagnosis of mantle cell lymphoma (MCL) was made. Combination chemotherapy by cyclophosphamide and vincristine was not effective, but etoposide perorally given at a dose of 50 mg per day was effective. In MCL, extranodal involvement of a digestive tract and bone marrow is well known. This case suggests that involvement of multiple organs including lacrimal glands and pleura could be characteristic of MCL cells.

Cell-cycle-regulated transcription of A- and B-type plant cyclin genes in synchronous cultures

Synchronously dividing cell cultures of Catharanthus roseus were used to isolate cDNAs for two mitotic cyclins, named CYS and CYM. The deduced protein sequence of CYS is similar to that of A-type cyclins, and CYM belongs to the group of B-type cyclins. In a fashion similar to the pattern of expression seen for A-type and B-type cyclins in mammalian cells, CYS is expressed before CYM in C. roseus cells during the cell cycle. CYS mRNA accumulated at the onset of S phase and disappeared early in the G2 phase, whereas CYM mRNA was detected in the G2 and M phases of the cell cycle. Tobacco homologs of the two genes showed similar cell-cycle dependent expression patterns in synchronous cultures of tobacco BY2 cells. In both systems, CYS was expressed much earlier in the cell cycle than most other plant A-type cyclins, and hence CYS along with the soybean cyc1GM can be classified into a distinct subclass. The activities of CYM and CYS promoters during the cell cycle were analyzed in stably transformed tobacco BY2 cells. Cyclin promoter sequences of 0.5 kb could confer the typical cell-cycle-dependent expression to the beta-glucuronidase (GUS) reporter gene: the CYS promoter directed S-phase-specific expression, whereas the CYM promoter drove M-phase-specific expression. These results indicate the important role of transcriptional regulation in the oscillations of cyclin mRNA levels during the cell cycle.

High-level expression of maize C4-type phosphoenolpyruvate carboxylase in Escherichia coli and its rapid purification

Maize C4-type phosphoenolpyruvate carboxylase (PEPC) was expressed in E. coli with the pET32 system. The expressed fusion PEPC was active and its amount comprised more than 10% of total soluble protein. The specific activity increased by about 45-fold, compared with our previous system [S. Yanagisawa and K. Izui, Agric. Biol. Chem., 54, 241-243 (1990)]. The fusion PEPC was rapidly purified with His bind metal chelation resin, showing a single band on SDS-PAGE. Moreover, the tag domain fused at the N-terminus did not have any effect on catalytic and regulatory properties of PEPC.

cDNA cloning and prokaryotic expression of maize calcium-dependent protein kinases

Using degenerate oligonucleotide primers corresponding to conserved regions of the calcium-dependent protein kinase (CDPK) family, we carried out a polymerase chain reaction and obtained four distinct partial-length cDNAs from a maize leaf library. We then used these clones as probes for conventional screening and isolated 19 longer clones from another cDNA library of maize seedlings. These clones were classified into four groups based on their DNA cross-hybridization. Two full-length cDNAs, designated as ZmCDPK9 and ZmCDPK7, were sequenced and characterized. The predicted protein of each clone was a typical CDPK with eleven canonical subdomains of protein kinases, and four EF-hand calcium-binding motifs in its N-terminal and C-terminal halves, respectively. The catalytic and regulatory domains were linked by a well-conserved junction domain. The N-terminus of the protein also contained a consensus sequence for an N-myristoylation signal. Northern blot analysis showed that the transcription level of each gene was higher in roots and etiolated leaves than in green leaves. To confirm the calcium dependency of the maize enzymes, the entire coding region of ZmCDPK9 was subcloned into an expression vector so that it was in frame with the vector-encoded peptide tags. A cell-free extract of Escherichia coli transformed with the recombinant plasmid exhibited calcium-dependent phosphorylation activity, using casein as a substrate.

Possible participation of Fas-mediated apoptosis in the mechanism of atherosclerosis

Apoptosis is a programmed cell death that plays a major role during development, homeostasis, and in many diseases. Recent evidence has demonstrated the death of vascular smooth muscle cells (VSMCs) within advanced human atheroma. In the rat balloon-injury model, apoptotic cells were specifically identified in the neointima. The presence of apoptotic cells was demonstrated by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). To clarify the mechanisms that trigger apoptosis in atherosclerotic lesions, we examined whether cytokines released from macrophages can modulate Fas, a death signal, in cultured human VSMCs. Simultaneous treatment with interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) but not with each cytokine alone induced upregulation of Fas in VSMCs. However, coincubation with NG-monomethyl-L-arginine, an inhibitor of nitric oxide (NO) synthesis, inhibited the upregulation of Fas induced by IL-1 and TNF-alpha. Incubation with sodium nitroprusside, a NO donor, also induced upregulation of Fas in VSMCs. Furthermore, fluorescent nuclear staining with Hoechst 33258 revealed that monoclonal antibody to human Fas significantly enhanced NO-induced apoptotis in VSMCs. These findings suggest that macrophage-derived cytokines can induce upregulation of Fas through a NO-dependent mechanism in VSMCs. Thus, Fas-mediated apoptosis may regulate apoptotic death of VSMCs during atherogenesis.

Pilomatricoma with a bullous appearance

A 15-year-old Japanese girl had an asymptomatic nodule on the right thigh of seven months' duration. The clinical appearance was similar to that of a bulla. There was a history of blunt trauma from dog scratch to the skin over the tumor shortly before tumor growth. Histopathological findings were consistent with pilomatricoma. In the overlying dermis, the collagen bundles were compressed to the tissue surrounding the tumor and the large space was seen. Around the tumor, some dilated endothelium-lined vascular channels were found, which were identified as lymphatic vessels.

Plant calcium-dependent protein kinase-related kinases (CRKs) do not require calcium for their activities

In plants, calcium-dependent protein kinases (CDPKs) make up a large family that is characterized by a C-terminal calmodulin(CaM)-like domain. Recently, a novel carrot cDNA clone encoding an atypical CDPK, which has a significantly degenerate sequence in the CaM-like domain, was found and named CDPK-related protein kinase (CRK) [Lindzen, E. and Choi, J.H. (1995) Plant Mol. Biol. 28, 785-797]. We obtained two different cDNA clones from maize which encode CRKs. For the first enzymatic characterization of CRK, a maize cDNA clone was expressed in E. coli. The recombinant protein efficiently phosphorylated casein, a conventional protein substrate. Notably, in this in vitro phosphorylation assay, the kinase activity did not require calcium as an activator. Thus, CRKs were suggested to be novel calcium-independent protein kinases having a degenerate CaM domain, the function of which remains to be elucidated.

The left ventriculographic pattern and serial electrocardiographic changes in hypertrophic cardiomyopathy patients with giant negative T waves

The configuration of the left ventriculogram (LVG) was classified in 64 patients with hypertrophic cardiomyopathy (HCM) observed in ECG, and characteristics of the configuration and serial changes in SV1+RV5 and giant negative T (GNT) waves were studied. The LVG configuration was classified into the spade (15 patients), papillary-muscle hypertrophy (PMH; n = 23), oval (n = 24) and banana types (n = 2). The spade, PMH and oval types were observed for mean periods of 66, 90 and 91 months, respectively. Serial changes in ECG were as follows: GNT decreased from 16.7 +/- 3.3 to 13.3 +/- 5.1 mm in the spade type and decreased significantly from 16.9 +/- 5.9 to 9.8 +/- 6.9 mm in PMH but showed no changes in the oval type. SV1+RV5 decreased significantly from 69.0 +/- 14.9 to 58.2 +/- 14.7 mm in PMH but showed no significant changes in the spade or oval types. Thus GNT decreased progressively in many patients with the exception of a few with the oval type. From these findings, we consider that apical hypertrophy had been established at the time of the initial LVG and changed over time thereafter in the spade and PMH types but that hypertrophy was still in progress in some patients with the oval type.

Excimer laser photorefractive keratectomy for patients with contact lens intolerance caused by dry eye

AIMS/BACKGROUND

To evaluate epithelial wound healing and visual outcome of excimer laser photorefractive keratectomy (PRK) performed on high myopic eyes with contact lens intolerance due to dry eye.

METHODS

PRK was performed on two groups of patients with non-Sjogren's dry eye: group A (-6 D to -9.5 D, 11 patients, 17 eyes) and group B (-11.5 D to -19.5 D, 11 patients, 16 eyes) in an attempt to eliminate the use of contact lenses (CL). The intended correction was full in group A and 10 D in group B.

RESULTS

Uncorrected visual acuity in group A was better than 20/40 in 12 (80.0%) of 15 eyes at 6 months and in 10 (90.9%) of 11 eyes at 1 year. Fourteen (92.8%) of 17 eyes in group A and four (25.0%) of 16 eyes in group B achieved refraction within plus or minus 1 D of the intended correction at 6 months. Re-epithelialisation was complete in 4 days, and epithelial cell area and permeability returned to the preoperative level within 1 month in all cases. All patients in group A were able to eliminate CL, whereas in group B, one patient needed spectacles for residual myopia and two patients resumed CL use because of regression. One eye with severe subepithelial scar formation and one eye with macular haemorrhage were observed in group B.

CONCLUSION

Our results suggest that PRK is effective for patients with high myopia (-6 D to approximately -10 D) and CL intolerance due to dry eye. Further studies are required to improve predictability and to prevent complications in PRK for very high myopia (> -10 D).

Quantitative videographic analysis of blinking in normal subjects and patients with dry eye

OBJECTIVE

To study patterns of eye blinking in normal subjects and patients with dry eye.

METHODS

We developed an automated, noninvasive blink monitor that permits quantitative analysis of 6 parameters of blinking. We used this method under normal conditions and then examined the effects on the patterns of blinking in patients with dry eye; several steps in this method were designed to exacerbate or ameliorate ocular surface desiccation.

RESULTS

The mean (+/-SD), maximum, and coefficient of variation of the interblinking time in normal subjects and patients with dry eye were 4.0 +/- 2.0 and 1.5 +/- 0.9 seconds, 8.9 +/- 4.0 and 4.2 +/- 2.4 seconds, and 55% +/- 21% and 65% +/- 24%, respectively. Those values for the blinking time were 0.20 +/- 0.04 and 0.27 +/- 0.16 seconds, 0.35 +/- 0.12 and 0.99 +/- 1.30 seconds, and 23% +/- 9% and 46% +/- 34%, respectively. The use of artificial tears or spectacles with moist panels and moist inserts tended to normalize the patterns of blinking in the patients with dry eye, whereas exposure to wind made them more abnormal.

CONCLUSIONS

Our technique permitted a rigorous analysis of blinking that was previously unavailable. We have shown that local ocular surface conditions alone can significantly affect patterns of blinking. This method should be applicable to studying psychologic and any other factors that may influence blinking.

Nitric oxide induces upregulation of Fas and apoptosis in vascular smooth muscle

Interleukin-1 induced a time-dependent release of high levels of nitric oxide from rat vascular smooth muscle cells up to 96 hours. A time-dependent release of lactate dehydrogenase was also induced by Interleukin-1 from 72 to 96 hours after its stimulation. In situ nick end-labeling assay revealed that incubation for 48 hours with interleukin-1 induced a positive staining of fragmented nuclei. However, NG-monomethyl-L-arginine, an inhibitor of nitric oxide synthase, inhibited both lactate dehydrogenase release and DNA fragmentation induced by interleukin-1. Furthermore, sodium nitroprusside, a nitric oxide donor, also induced lactate dehydrogenase release and DNA fragmentation. Fluorescent staining of DNA revealed patches of irregularly dispersed, brightly staining, and condensed chromatin in rat vascular smooth muscle cells treated with sodium nitroprusside. Flow cytometric analysis with monoclonal antibody against human Fas revealed that expression of Fas was upregulated by sodium nitroprusside in human vascular smooth muscle cells. Methylene blue, an inhibitor of soluble guanylate cyclase, did not affect sodium nitroprusside-induced upregulation of Fas. Furthermore, 8-bromo-guanosine 3':5'-cyclic monophosphate, an analogue of cGMP, did not upregulate Fas expression. These findings indicate that nitric oxide released from vascular smooth muscle cells may induce apoptosis in vascular smooth muscle cells themselves and also induced upregulation of Fas via a cGMP-independent mechanism. Thus, nitric oxide could trigger the remodeling of atherosclerotic plaques.

Parathyroid hormone-related protein inhibits indothelin-1 production

The effect of human parathyroid hormone-related protein, a powerful vasodilator, on endothelin-1 production in cultured bovine pulmonary arterial endothelial cells was studied. Treatment with parathyroid hormone-related protein(1-34) at concentrations of 10(-9) to 10(-6) mol/L for 24 hours caused dose-dependent suppression of the secretion of endothelin-1, with maximal suppression at 10(-7) mol/L to 74% of the control value. This inhibitory effect was completely abolished by coincubation with 100 ng/mL pertussis toxin, an inhibitor of GTP binding protein. Furthermore, addition of Ng-monomethyl-L-arginine, an inhibitor of nitric oxide synthase, at 10(-3) mol/L significantly blocked the suppressive effect of parathyroid hormone-related protein (1-34) on endothelin-1 secretion, and further addition of 5x10(-3) mol/L L-arginine significantly attenuated the blocking effect of N(G)-monomethyl-L-arginine. Parathyroid hormone-related protein (1-34) at 10(-7) mol/L resulted in an approximately fivefold increase in intracellular cGMP level. Northern blot analysis revealed that parathyroid hormone-related protein (1-34) inhibited both basal and thrombin-induced endothelin-1 gene expression. These findings suggest that the vasodilating property of parathyroid hormone-related protein may be mediated in part through its inhibitory effect on endothelin-1 production, which is probably mediated through nitric oxide and cGMP in endothelial cells. Thus, a feedback regulatory mechanism may exist between parathyroid hormone-related protein and endothelin-1 in the vascular wall.

High-performance liquid chromatographic determination of finasteride in human plasma using direct injection with column switching

A fully automated column-switching high-performance liquid chromatographic (HPLC) method was developed for the quantification of finasteride [N-(1,1-dimethylethyl)-3-oxo-4-aza-5 alpha-androst-1-ene-17 beta- -carboxamide] in human plasma. Plasma samples were diluted with an equal volume of ethylene glycol-water (40:60, v/v), then the diluted sample (150 microliters) was injected into the HPLC system without clean-up. The analyte was retained on a pretreatment column, whereas plasma proteins and other endogenous components were washed out to waste. The analyte was transferred to the analytical column in the heart-cut mode and then detected at 210 nm. A quantification limit of 1 ng/ml was attained. There was a linear relationship between peak height and drug concentration in plasma in the range 1-50 ng/ml. This method was validated and applied to the assay of plasma samples to characterize pharmacokinetic parameters in clinical studies.

Increase in corneal epithelial cell size with extended wear soft contact lenses depends on continuous wearing time

AIM

Although 1 week of continuous wearing time (CWT) is recommended for extended wear soft contact lenses (EWSCL), there have been few studies concerning the appropriateness of this or other CWTs. The current study was undertaken to examine the effect of various CWTs on the cornea by observing the corneal epithelium.

METHODS

Specular microscopy was used to evaluate corneal epithelial changes induced by EWSCL in 19 myopic patients (24.0 (SD 6.7) years), divided into four groups: CWT of 0, 1, 3, and 6 days.

RESULTS

The initial mean cell area was 628.2 (13.4) micron2. After 6 months this was 629.3 (28.6) micron2 for daily wear (ns), and 660.0 (40.9) micron2, 727.7 (49.6) micron2 (p < 0.01), and 815.5 (67.2) micron2 (p < 0.01) for CWT of 1, 3, and 6 days, respectively (p < 0.01).

CONCLUSION

These findings indicate that the corneal epithelium changes proportionally with the CWT; the shorter the CWT, the better the epithelial morphology. This suggests that the CWT for EWSCL be minimised, so as to reduce the potential risk of contact lens related problems.

Simultaneous monitoring of intracellular pH and proton excretion during glycolysis by Streptococcus mutans and Streptococcus sanguis: effect of low pH and fluoride

A system was developed by which 2',7'-bis(carboxyethyl)-4 or 5-carboxyfluorescein could be used to monitor intracellular pH at the same time that proton excretion was being measured. Streptococcal cells were loaded with the dye, and after the addition of glucose protons were excreted and the intracellular pH increased quickly and remained higher than the extracellular pH of 7.0. The excretion of protons stopped and the intracellular pH returned to the original level when glucose was depleted. The intracellular level of ATP remained high during glucose metabolism and decreased with the depletion of glucose. At extracellular pH of 5.5, and 5.0, the intracellular pH of fasting cells was higher than the extracellular pH value. After addition of glucose there were initial lags of proton excretion and of increases in intracellular pH at the acidic extracellular pH values. In the presence of fluoride, a lag in proton excretion and a simultaneous decrease in intracellular pH were observed, indicating a partial and transient inhibition of proton-ATPase activity.