Alanine-scanning mutagenesis of the epsilon subunit of the F1-F0 ATP synthase from Escherichia coli reveals two classes of mutants

Alanine-scanning mutagenesis was applied to the epsilon subunit of the F1-F0 ATP synthase from E. coli. Nineteen amino acid residues were changed to alanine, either singly or in pairs, between residues 10 and 93. All mutants, when expressed in the epsilon deletion strain XH1, were able to grow on succinate minimal medium. Membranes were prepared from all mutants and assayed for ATP-driven proton translocation, ATP hydrolysis +/- lauryldiethylamine oxide, and sensitivity of ATPase activity to N,N'-dicyclohexylcarbodiimide (DCCD). Most of the mutants fell into 2 distinct classes. The first group had inhibited ATPase activity, with near normal levels of membrane-bound F1, but decreased sensitivity to DCCD. The second group had stimulated ATPase activity, with a reduced level of membrane-bound F1, but normal sensitivity to DCCD. Membranes from all mutants were further characterized by immunoblotting using 2 monoclonal antibodies. A model for the secondary structure of epsilon and its role in the function of the ATP synthase has been developed. Some residues are important for the binding of epsilon to F1 and therefore for inhibition. Other residues, from Glu-59 through Glu-70, are important for the release of inhibition by epsilon that is part of the normal enzyme cycle.

Brain tissue hydrolysate acts on presynaptic adenosine receptors in the rat hippocampus

Adenosine is a potent inhibitory modulator in the brain. It suppresses glutamatergic synaptic transmission and possibly acts as a brain endogenous neuroprotective agent. In this study we have examined the effects of a clinically used porcine brain tissue hydrolysate, Cerebrolysin, on synaptic transmission in the CA1 area of rat hippocampal slices. A major effect of the drug at doses approximating those administered clinically to demented patients was a depression of synaptic transmission at the Schaffer collateral-commissural pathway in CA1. Detailed analysis showed that the inhibition is presynaptic and can be reduced by low doses of a specific blocker of adenosine A1 receptors, 8-cyclopentyltheophylline. Because Cerebrolysin does not contain a detectable amount of adenosine, the effect on adenosine A1 receptors must be indirect, perhaps by release of the endogenous agonist. This action of Cerebrolysin is consistent with a putative neuroprotective action underlying its clinical usage.

[Characters and insecticidal polypeptide of a new strain of Bacillus thuringiensis subsp. kenyae in China]

A new strain of Bacillus thurinigiensis Bt with high toxicity against noctuidae larvae has been screened for many generations since isolated from larvae candle of Aphomia gularis in Yiyang County, Jiangxi Province, in China. By comparison and analysis of results of physiological and biochemical test, flagella antigen identification and esterase type, the strain is identified as H4a-4c Bt serovar. kenyae. Since its crystal protein type and plasmid type are different from those of Bt serovar. kenyae's type 023. The strain is assigned a novel strain: Btken-Ag. Btken-Ag's parasporal crystals are multi-morphorous: bipyramid, cube, small irregular sphere and embedded. After UMT dissolve, PAGE and SDS-PAGE separation preparation and analysis, it is found that its major insecticide component to Heliothis armigera is 61kD toxic protein. By ELISA homology analysis, it is found that this toxic protein has high homology with crystal protein of 023 and 7501 (H4a-4c), partly homology with that of HD-1(H3a-3b), but no homology with that of Bti(H14) and (Bacillus sphaericus) Ts-1 strain. In bioassay with larvae from Culex pipiens, Pseudaletia unipuncta and Heliothis armigera, together with other ten Bt strains, Btken-Ag is toxic to 3 star larvae of Culex pipiens; two isolates of Btken-Ag (b1-4 and H4-1) show higher toxicity than type strain 023 and HD-1 do to Pseudaletia unipuncta and Heliothis armigera.

Periodicity of polar and nonpolar amino acids is the major determinant of secondary structure in self-assembling oligomeric peptides

The tendency of a polypeptide chain to form alpha-helical or beta-strand secondary structure depends upon local and nonlocal effects. Local effects reflect the intrinsic propensities of the amino acid residues for particular secondary structures, while nonlocal effects reflect the positioning of the individual residues in the context of the entire amino acid sequence. In particular, the periodicity of polar and nonpolar residues specifies whether a given sequence is consistent with amphiphilic alpha-helices or beta-strands. The importance of intrinsic propensities was compared to that of polar/nonpolar periodicity by a direct competition. Synthetic peptides were designed using residues with intrinsic propensities that favored one or the other type of secondary structure. The polar/nonpolar periodicities of the peptides were designed either to be consistent with the secondary structure favored by the intrinsic propensities of the component residues or in other cases to oppose these intrinsic propensities. Characterization of the synthetic peptides demonstrated that in all cases the observed secondary structure correlates with the periodicity of the peptide sequence--even when this secondary structure differs from that predicted from the intrinsic propensities of the component amino acids. The observed secondary structures are concentration dependent, indicating that oligomerization of the amphiphilic peptides is responsible for the observed secondary structures. Thus, for self-assembling oligomeric peptides, the polar/nonpolar periodicity can overwhelm the intrinsic propensities of the amino acid residues and serves as the major determinant of peptide secondary structure.

Phosphorylation of eukaryotic protein synthesis initiation factor 4E by insulin-stimulated protamine kinase

Insulin-stimulated protamine kinase (cPK) and protein kinase C (PKC) phosphorylated eukaryotic protein synthesis initiation factor 4E (eIF-4E) on serine and threonine residues located on an identical tryptic fragment as judged by two-dimensional phosphopeptide mapping. With cPK and PKC, the apparent Km for eIF-4E was about 1.2 and 50 microM, respectively. Relative to recombinant human eIF-4E, cPK exhibited about 100% and < or = 5% activity with eIF-4ES209A and eIF-4ET210A, respectively, and eIF-4ES209A was phosphorylated exclusively on threonines. Bovine kidney eIF-4E enhanced up to 1.8-fold globin synthesis in m7GTP-Sepharose-treated reticulocyte lysates. In contrast, following incubation with cPK, these eIF-4E preparations stimulated globin synthesis up to 6-fold. Compared to the dephosphorylation of the cPK-modified serine on eIF-4E, reticulocyte lysates and highly purified protein phosphatase 2A exhibited marked preference for the cPK-modified threonine. The results indicate that cPK phosphorylates eIF-4E on Ser209 and Thr210, that the hydroxyl group or phosphorylation of Thr210 is necessary for cPK to act on Ser209, and that Ser209 phosphorylation activates reticulocyte globin synthesis. The results suggest that cPK could contribute to the insulin-stimulated phosphorylation of eIF-4E, but that protein phosphatase 2A may confer the site specificity of this response.

Correlation between the presence of virulence-associated genes as determined by PCR and actual virulence to mice in various strains of Listeria spp

Five chromosomal genes, prfA, plcA, hlyA, mpl and plcB, are implicated in the virulence of Listeria monocytogenes and some of these genes have been used for the identification of bacteria by polymerase chain reaction (PCR). Using 6 strains of L. monocytogenes and 3 L. innocua strains, the relationship was examined between the presence of five virulence-associated genes and actual virulence to mice in terms of 50% lethal dose (LD50), bacterial viability in the organ of infected mice and the intracellular growth in cultured macrophages. None of the five genes could be amplified by PCR in all the L. innocua strains and they were actually avirulent to mice. All L. monocytogenes strains were shown to be virulent and to have intact virulence-associated genes except for the strain ATCC15313. This particular strain was revealed to be avirulent and defective in hlyA and plcA in PCR amplification. It was suggested that PCR detection of genes prfA, mpl, or plcB may not be sufficient to detect virulent strains of L. monocytogenes. It appeared that the ability to produce listeriolysin O (LLO), which is encoded by hlyA, was critical for the expression of virulence regardless of the amount of LLO produced.

Construction and plasmid-borne complementation of strains lacking the epsilon subunit of the Escherichia coli F1F0 ATP synthase

Two strains of Escherichia coli that lack the epsilon subunit of the F1F0 ATP synthase have been constructed. They are shown to be viable but with very low growth yields (28%). These strains can be complemented by plasmids carrying wild-type uncC, but not when epsilon is overproduced. These results indicate that epsilon is not essential for growth on minimal glucose medium and that the level of its expression affects the assembly of the ATP synthase.

Autophosphorylation-activated protein kinase inactivates the protein tyrosine phosphatase activity of protein phosphatase 2A

Phosphorylation of the catalytic subunit of protein phosphatase 2A (PP2A) on threonines with a distinct autophosphorylation-activated protein kinase [Guo and Damuni (1993) Proc. Natl. Acad. Sci. USA 90, 2500-2504] inactivated the phosphatase with 32P-labelled myelin basic protein prepared by incubation with the kinase domain of the epidermal growth factor receptor, the src-family protein kinases p56lck and p60c-src, myelin basic protein kinase-1, or protamine kinase. Phosphoamino acid analysis demonstrated that the kinase domain of the epidermal growth factor receptor, p56lck and p60c-src phosphorylated myelin basic protein on tyrosines, that the protamine kinase phosphorylated myelin basic protein on serines, and that myelin basic protein kinase-1 phosphorylated myelin basic protein on threonines. The results demonstrate that the autophosphorylation-activated protein kinase not only inactivates the protein serine/threonine phosphatase, but also the protein tyrosine phosphatase activity of PP2A. This autophosphorylation-activated protein kinase-mediated inactivation of PP2A may, in response to extracellular stimuli, not only contribute to the enhanced phosphorylation of cellular proteins on serines and threonines but also on tyrosines.

Cytokine gene expression in mice at an early stage of infection with various strains of Listeria spp. differing in virulence

By using reverse transcription-PCR, cytokine gene expression was examined in mice 24 h after infection with various strains of Listeria spp. differing in virulence as determined by in vivo growth and 50% lethal dose values. All the virulent strains of Listeria monocytogenes induced the expression of mRNAs specific for interleukin-1 alpha (IL-1 alpha), gamma interferon (IFN-gamma), and tumor necrosis factor alpha (TNF-alpha) in the spleen of mice, while an L. monocytogenes strain incapable of producing listeriolysin O and strains of Listeria innocua induced the expression of TNF-alpha mRNA only. The levels of expression of IL-1 alpha and IFN-gamma mRNAs were proportional to the levels of listeriolysin O produced by each strain. Those strains which induced the expression of IFN-gamma were capable of generating protective immunity in the infected host, suggesting that the virulence-related induction of some cytokine at the initial stage of infection plays a role in the induction of acquired cellular resistance to L. monocytogenes.

Angiotensin II depresses glutamate depolarizations and excitatory postsynaptic potentials in locus coeruleus through angiotensin II subtype 2 receptors

A previously reported depression of glutamate responses by angiotensin II was investigated to define the nature of this neuromodulatory effect. Studies were carried out in an vitro brain slice preparation containing the locus coeruleus, using intracellular recordings, and iontophoretic, micropressure and bath perfusion methods for application of drugs. The angiotensin action was found to be blocked by a non-peptide antagonist specific for the angiotensin type 2 receptor, and not by an antagonist selective for the type 1 receptor. Excitatory postsynaptic potentials mediated primarily by excitatory amino acids were also depressed by angiotensin II. The angiotensin II depressions of glutamate were shown to be strong and highly specific. The low effectiveness of bath-applied compared with iontophoretically or micropressure-applied angiotensin II was found to be at least partly explained by a rapid degradation by peptidases. Ammonium ions and hydrogen ions were also able to depress glutamate responses, but these effects were not specific for locus coeruleus neurons and were mediated independently of the angiotensin actions. Strong depression by angiotensin II of excitatory postsynaptic potentials as well as exogenously applied glutamate strengthens the strong possibility of a physiological role for this neuromodulatory mechanism. The identification of the type 2 angiotensin receptor subtype as the mediator of this effect indicates a novel functional role for this receptor, since previously recognized functions of angiotensin II in the brain, such as vascular and body fluid regulation, have been associated with the type 1 receptor.

Detection of multiple virulence-associated genes of Listeria monocytogenes by PCR in artificially contaminated milk samples

The inhibitory effect of milk in the PCR detection of Listeria monocytogenes could be overcome by washing the contaminated milk sample with phosphate-buffered saline and concentrating the bacteria to 1/10 of the original volume. In order to avoid a possible failure in the detection of virulent L. monocytogenes, a one-step procedure which enabled demonstration of three virulence-associated genes, prfA, hlyA, and plcB, simultaneously in a single PCR mixture was developed.

Enzyme-catalysed kinetic resolution of 4-endo-hydroxy-2-oxabicyclo[3.3.0]oct-7-en-3-one and employment of the pure enantiomers for the synthesis of anti-viral and hypocholestemic agents

The endo-hydroxylactone (+/-)-(1) was resolved by enantioselective acetylation using Candida cylindracea lipase or preferentially Pseudomonas fluorescens lipase (pfl). Alternatively the corresponding butyrate (+/-)-(3) was hydrolysed with pfl to give the ester (+)-(1S,4R,5S)-(3) and the alcohol (-)-(1R,4S,5R)-(1). The latter compound was converted into carbovir (-)-(1R,4S)-(12) while the ester (+)-(3) was transformed into the delta-lactone (+)-(3R,5S)-(18). The exo-hydroxylactone (+/-)-(2) was resolved less efficiently by a trans-esterification process employing pfl and vinyl acetate.

Protein design by binary patterning of polar and nonpolar amino acids

A general strategy is described for the de novo design of proteins. In this strategy the sequence locations of hydrophobic and hydrophilic residues were specified explicitly, but the precise identities of the side chains were not constrained and varied extensively. This strategy was tested by constructing a large collection of synthetic genes whose protein products were designed to fold into four-helix bundle proteins. Each gene encoded a different amino acid sequence, but all sequences shared the same pattern of polar and nonpolar residues. Characterization of the expressed proteins indicated that most of the designed sequences folded into compact alpha-helical structures. Thus, a simple binary code of polar and nonpolar residues arranged in the appropriate order can drive polypeptide chains to collapse into globular alpha-helical folds.

Modelling cortical cataractogenesis. 13. Early effects on lens ATP/ADP and glutathione in the streptozotocin rat model of the diabetic cataract

A possible contribution to cell toxicity in the diabetic lens due to early ATP loss is not well characterized prior to the appearance of vacuoles in the lens. Changes in lens ATP levels at longer periods of hyperglycaemia (6-8 weeks) have been reported. We used [31P]NMR analysis of lens extracts at three time periods, comparing diabetic to concurrent control groups at 1, 2 and 4 weeks of hyperglycaemia. With this design, significant alterations (> 10%) in the ATP/ADP ratio can be monitored. NMR analysis revealed a decreased ATP/ADP ratio at all time periods, averaging a 38% decrease. Luminescent determination of ATP levels indicates that this decrease is mainly caused by a decrease of 25% in ATP concentration. The early loss of GSH was large and not accompanied by an appearance of GSSG, as monitored by HPLC electrochemical detection. A 1-week experiment with animals receiving daily insulin treatment was carried out to control for effects of STZ on the lens. This treatment resulted in normal lens GSH levels and a near normal [31P]NMR profile.

Diffusion control in blood coagulation. Activation of factor X by factors IXa/VIIIa assembled on human monocyte membranes

This study examines mechanisms that regulate the activation of blood coagulation proteases on intact cell membranes. The activation of factor X by factors IXa and VIIIa assembled on viable monocytes is presented as a biologically relevant model for membrane-dependent proteolysis of coagulation zymogens. The hypothesis that this reaction is limited by diffusion was tested by comparing predicted with observed concentration dependence, temperature dependence, and effective rate coefficient. Rates of factor X catalysis were measured using a chromogenic substrate specific for the product, factor Xa. The value of KR and of K1/2, i.e. concentrations giving half-maximal rates in reciprocal functional titrations with substrate and enzyme, respectively, were directly correlated with the concentration of the titrated component. Arrhenius plots constructed over temperatures encompassing 10-35 degrees C were biphasic with downward concavity. Apparent activation energies were 6.01 +/- 0.93 and 35.84 +/- 8.9 kcal/mol for the interval above and below the inflection point, respectively. The effective rate coefficient calculated from apparent kinetic parameters was 3.58 +/- 0.1 x 10(12) M-1 s-1. This rate is similar to the maximal rate of collision between factor X molecules and the monocyte, i.e. 2.9 x 10(12) M-1 s-1 estimated from the steady-state von Smoluchowski equation for uniformly reacting spherical particles. The observed agreement between predicted and experimental results indicates that under biologically relevant conditions, the rate of factor X activation by the intrinsic protease is controlled by diffusion of factor X toward the catalytic site.

Topical tocopherol acetate reduces post-UVB, sunburn-associated erythema, edema, and skin sensitivity in hairless mice

Exposure of the skin of the back of skh-1 hairless mice to UVB (310 nm peak) irradiation at doses of 0.115-0.23 J/cm2 results after 24-48 h in an erythema which can be quantified using an erythema meter, providing a useful model of sunburn. Application of pure d-alpha-tocopherol acetate, a thick oil, to the skin immediately following the exposure to UVB significantly reduces the increase in erythema index, by 40-55%. At the lower dose (0.115 J/cm2), skin thickness (associated with edematous swelling of the sunburned skin) was measured by a novel non-invasive technique not previously reported for this purpose--magnetic resonance imaging (MRI). In two experiments the UVB-induced increase in skin thickness was significantly reduced at 24 hr by 29 and 54%, and at 48 hr by 26 and 61%. After 8 days the untreated irradiated mouse skin still showed a significant increase in thickness (24%) compared to the untreated unirradiated control, while the treated irradiated control was not significantly thicker than the unexposed control. Skin sensitivity was tested using a modification of the technique of esthesiometry, by observing rapid avoidance responses of the mouse to a pressure of 0.96 g/cm2 exerted by applying to the skin the tip of a nylon esthesiometer fiber extended to 60 mm in length. The untreated irradiated mice were more sensitive (p less than 0.07, Wilcoxon test) than the treated irradiated mice, and also significantly different from the untreated unirradiated control mice (p less than 0.04, Wilcoxon test), but the treated irradiated mice were not significantly differently sensitive when compared to the unirradiated controls (p less than 0.32). Taken together these data indicate that the erythema, edema, and skin sensitivity commonly associated with UVB-induced sunburn are significantly reduced by topical application of tocopherol acetate even after the exposure has occurred. This observation suggests that treatment of sunburn may be possible even after the irradiation has stopped, by a derivative of d-alpha-tocopherol which is stable to autooxidation.

Structural modification study of anthracyclinones: synthesis and biological activity of several derivatives of eta-pyrromycinone

On the basis of the N-O-O triangular pharmacophore hypothesis postulated earlier in our laboratory, selected side chains with or without the nitrogen atom at the strategic position were incorporated to eta-pyrromycinone, one of the anthracyclinones derived from the antibiotic cinerubins. Since none of the anthracyclinones (the aglycones of anthracyclines) were reported to have antineoplastic activity, the validity of the proposed hypothesis could be tested. Results indicated that a compound designed in this manner, 1,4-bis[2-(2,2-dimethyloxazolidin-3-yl)ethylamino]-1,4-didehydr oxy-eta- pyrromycinone (9c) possessed both in vitro and in vivo antineoplastic activity comparable to that of mitoxantrone. The structure-activity relationship of this class of compounds is discussed.

Rose bengal activates the Ca2+ release channel from skeletal muscle sarcoplasmic reticulum

The photooxidizing xanthene dye rose bengal (10 nM to 1 microM) stimulates rapid Ca2+ release from skeletal muscle sarcoplasmic reticulum vesicles. Following fusion of sarcoplasmic reticulum (SR) vesicles to an artificial bilayer, reconstituted Ca2+ channel activity is stimulated by nanomolar concentrations of rose bengal in the presence of a broad-spectrum light source. Rose bengal does not appear to affect K+ channels present in the SR. Following reconstitution of the sulfhydryl-activated 106-kDa Ca2+ channel protein into a bilayer, rose bengal activates the isolated protein in a light-dependent manner. Ryanodine at a concentration of 10 nM is shown to lock the 106-kDa channel protein in a subconductance state which can be reversed by subsequent addition of 500 nM rose bengal. This apparent displacement of bound ryanodine by nanomolar concentrations of rose bengal is also directly observed upon measurement of [3H]ryanodine binding to JSR vesicles. These observations indicate that photooxidation of rose bengal causes a stimulation of the Ca2+ release protein from skeletal muscle sarcoplasmic reticulum by interacting with the ryanodine binding site. Furthermore, similar effects of rose bengal on isolated SR vesicles, on single channel measurements following fusion of SR vesicles, and following incorporation of the isolated 106-kDa protein strongly implicates the 106-kDa sulfhydryl-activated Ca2+ channel protein in the Ca2+ release process.

The effect of insulin and aldose reductase inhibition on the phosphate metabolism of streptozotocin-diabetic rat lens

Sorbitol-3-phosphate (S3P) and fructose-3-phosphate (F3P) are novel phosphorus compounds recently discovered and identified in the crystalline lens as well as other tissues. These phosphates increased with diabetes progression in streptozotocin-diabetic rat lenses. Treatment of these rats with an orally administered aldose reductase inhibitor eliminated S3P and intramuscularly injected insulin obliterated F3P. These results indicate that enzymes catalyzing S3P and F3P formation co-activate with aldose reductase activation and hyperglycemia, respectively.

Metabolic studies of galactosemic cataract

Experimental diabetic and galactosemic animal models are widely used to study diabetes-induced complications. Galactose feeding can rapidly produce cataract, retinopathy and nephropathy; it is therefore favored over the diabetic model. Although the common feature for both models is the activation of aldose reductase, there are substantial differences between the two--not only does the rate of cataract progression differ but the metabolic patterns are far more complex than for polyol production alone. We here present the result of a comparison between diabetic and galactosemic lenses and show the differences in phosphorus and aldose metabolism, cell integrity and osmotic environment.

Metabolic analysis of reepithelializing rabbit cornea using phosphorus-31 nuclear magnetic resonance spectroscopy

To investigate metabolic differences between the central and peripheral cornea the latter including the limbal area, corneas were dissected and examined using phosphorus-31 (31P) nuclear magnetic resonance spectroscopy. Since most 31P signals originate from the epithelium, 31P spectra of the cornea primarily represent the metabolic state of the epithelium. The spectra of the peripheral cornea showed all phosphorus resonances detected in the whole cornea; in contrast, the central cornea showed no phosphocreatine and glycerophosrylethanolamine, and only low levels of ATP. These results indicate that there is a higher metabolic activity in the peripheral epithelium, especially in the limbal area, than in the central epithelium. To evaluate the metabolic state of corneal epithelium during regeneration, we also examined corneas reepithelializing after 7 mm of central epithelial tissue had been removed by mechanical scraping. Rabbits were killed 24 and 48 h after scraping. The reepithelializing corneas clearly showed an increase in ATP, phosphocreatine, and sugar phosphates with time, although phosphorylcholine remained depressed. These findings suggest that the reepithelializing cornea has an elevated level of energy production and that it may have reached a higher steady state, thereby indicating accelerated metabolism of the epithelium during regeneration.

Disulfide linkage of biotin identifies a 106-kDa Ca2+ release channel in sarcoplasmic reticulum

Reactive disulfide reagents (RDSs) with a biotin moiety have been synthesized and found to cause Ca2+ release from sarcoplasmic reticulum (SR) vesicles. The RDSs oxidize SH sites on SR proteins via a thiol-disulfide exchange, with the formation of mixed disulfide bonds between SR proteins and biotin. Biotinylated RDSs identified a 106-kDa protein which was purified by biotin-avidin chromatography. Disulfide reducing agents, like dithiothreitol, reverse the effect of RDSs and thus promoted active re-uptake of Ca2+ and dissociated biotin from the labeled protein indicating that biotin was covalently linked to the 106-kDa protein via a disulfide bond. Several lines of evidence indicate that this protein is not Ca2+, Mg2+-ATPase and is not a proteolytic fragment or a subunit of the 400-kDa Ca2+-ryanodine receptor complex (RRC). Monoclonal antibodies against the ATPase did not cross-react with the 106-kDa protein, and polyclonal antibodies against the 106-kDa did not cross-react with either the ATPase or the 400-kDa RRC. RDSs did not label the 400-kDa RRC with biotin. Linear sucrose gradients used to purify the RRC show that the 106-kDa protein migrated throughout 5-20% linear sucrose gradients, including the high sucrose density protein fractions containing 400-kDa RRC. Protease inhibitors diisopropylfluorophosphate used to prevent proteolysis of 400-kDa proteins did not alter the migration of 106-kDa in sucrose gradients nor the patterns of biotin labeling of the 106-kDa protein. Incorporation of highly purified 106-kDa protein (free of RRC) in planar bilayers revealed cationic channels with large Na+ (gNa+ = 375 +/- 15 pS) and Ca2+ (gCa2+ = 107.7 +/- 12 pS) conductances which were activated by micromolar [Ca2+]free or millimolar [ATP] and blocked by micromolar ruthenium red or millimolar [Mg2+]. Thus, the SR contains a sulfhydryl-activated 106-kDa Ca2+ channel with apparently similar characteristics to the 400-kDa "feet" proteins.

Polyol pathway activity in streptozotocin-diabetic rat lens

We have examined polyol pathway kinetics in the lenses of rats made diabetic with streptozotocin. At up to 11 days after diabetes induction, the lenses were isolated and subjected to 'pulse-chase' studies: the lenses were incubated with [13C]glucose and lens metabolism followed by [13C]nuclear magnetic resonance (NMR) spectroscopy. Proton NMR spectroscopy was also performed to measure the hexose monophosphate shunt (HMPS) activity. The results showed that (1) the activity of aldose reductase increased initially and decreased after 11 days of diabetes; (2) the fructose pool increased initially but started to decline after 3 days; (3) the HMPS activity increased nearly 40% immediately after diabetes induction; and (4) the turnover rates of glucose, alpha-glycerophosphate (GP), lactate, sorbitol, and fructose were 80.8 +/- 2.6, 10.1 +/- 1.4, 47.7 +/- 3.7, 7.9 +/- 0.9 and 5.2 +/- 2.2 nmol hr-1 lens-1 (34 mg wet weight lens-1), respectively. Up to 35% of lactate appeared to derive from the polyol pathway. Further, GP was rapidly metabolized, although its fate is currently unknown. These results reveal a far more complex pattern of glucose metabolism in the diabetic lens than that in lenses incubated in high glucose.

Metabolic changes in the cornea of vitamin A-deficient rats

We have investigated alterations of the metabolic state in vitamin A-deficient (A-) corneas using phosphorus-31 (31P) nuclear magnetic resonance (NMR) spectroscopy. Comparing to the control, A- corneas showed a prominent rise of phosphocreatine (PCr) as well as a total loss of glycerophosphorylcholine (GPC). Further, ATP levels were lower, and sugar phosphates (SP) and inorganic phosphate (Pi) were higher than those of the control. The accumulation of PCr and Pi, and decrease of ATP indicate that the activity of creatine kinase may be altered in vitamin A deficiency. These results suggest that vitamin A may have a role in creatine kinase activation and/or induction and that its deficiency causes a decline of energy metabolism in corneal epithelium. Moreover, disappearance of GPC implies an impaired cellular membrane metabolism. When retinyl acetate was supplied to A-rats for 5 weeks, the 31P profiles of vitamin A-repleted rat corneas recovered to normal.

[Observation on muscular glycogen in spleen-deficient rats treated with a jian pi yi qi decoction]

The relationship between "Spleen" and muscles was explored by determining the amount of muscular glycogen to indicate the stored energy in muscles. The amount of muscular glycogen in normal rats was 6.34 +/- 0.20 mg/g muscles, it was much more than that in Spleen deficiency rats caused by rhubarb (4.27 +/- 0.40 mg/g muscles). In order to observe the effects of Jian Pi Yi Qi decoction on Spleen deficiency, the Spleen deficiency rats were divided into two groups, one of which was treated with Jian Pi Yi Qi decoction as experimental group, the other with distilled water as control. After one week, the amount of muscular glycogen in experimental group was 5.35 +/- 0.16 mg/g muscles and in control 4.63 +/- 0.15 mg/g muscles. It showed that the rising of the amount of muscular glycogen in experimental group was more than that in control with statistic significance but it was still lower than that in normal rats.

Aqueous/vitreous tonicity in "sugar' cataracts

We examined the aqueous/vitreous tonicity in "sugar' cataracts. Four sets of eyes and their controls were examined: diabetic human eyes, eyes from rabbits and rats fed 50% galactose for up to 1 week, and eyes from streptozotocin-diabetic rats of up to 21 days after diabetes induction. The results showed no statistically significant increase of aqueous/vitreous tonicity in the diabetic human eye and eyes from galactose-fed rats and rabbits. Diabetic rats, on the other hand, showed large tonicity increase in the vitreous, although treatment of the diabetic rats with an aldose reductase inhibitor or insulin completely normalized the tonicity. Seven days after feeding, the galactose-fed animals already showed lens opacities, while diabetic rat lenses remained clear even after 21 days after diabetes induction. These results indicate insignificant osmotic changes in the human eye. In the rat eye, the increase of lens tonicity can be offset by a concomitant increase in the vitreous tonicity. However, this phenomenon is not observed in the galactose eyes. The nature of the osmolytes in the diabetic eye is unclear, although both glucose and sorbitol have been ruled out. The presence of an osmotic regulatory mechanism in the eye is implied.