Effects of ethanol on mitogen-activated protein kinase and stress-activated protein kinase cascades in normal and regenerating liver

To understand the mechanisms by which ethanol inhibits hepatocyte proliferation, we studied the effects of ethanol on p42/44 mitogen-activated protein kinase (MAPK), p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal kinase (JNK) in normal and regenerating rat liver. Treatment of rat hepatocytes with 100 mM ethanol in vitro for 16 h prolonged the activation of p42/44 MAPK and p38 MAPK induced by various agonists. Such treatment also increased basal JNK activity, but did not potentiate or prolong agonist-induced JNK activation. Ethanol potentiation of the activation of p42/44 MAPK was abolished by pertussis toxin. In contrast, chronic ethanol consumption in vivo inhibited the activation of p42/44 MAPK, p38 MAPK and JNK induced either by partial hepatectomy or by various agonists. However, both acute and chronic ethanol inhibited hepatocyte proliferation induced by insulin and epidermal growth factor. A selective inhibitor of p42/44 MAPK partially prevented the inhibition of hepatocyte proliferation caused by acute, but not by chronic, ethanol exposure, whereas a selective inhibitor of p38 MAPK further inhibited hepatocyte proliferation under both conditions. These data suggest that acute and chronic ethanol inhibit hepatocyte proliferation by different mechanisms. The effect of acute ethanol may be related to the prolongation of p42/44 MAPK activation, whereas inhibition of hepatocyte proliferation by chronic ethanol may be due to inhibition of p38 MAPK activation.

[Multicentre, randomized, prospective and comparative study of ceftriaxone, cefotaxime and cefuroxime in treating mild to moderate respiratory tract infection]

OBJECTIVE

The objective of this multicentre, randomized, prospective and comparative study was to evaluate and compare the efficacy and safety of 1 g intravenous ceftriaxone (active ingredient of Rocephin), 3 g intravenous cefoiaxime (active ingredient of clafron), and 2.25 g intavenous cefuroxime (active ingredient of Zinacef).

METHOD

In this multicentre, randomized, prospective and comparative study, patients received 1 g of ceftriaxone intravenously once a day (group A), or 1 g of cefotaxime intravenously three times a day (group B), or 0.75 g of cefuroxime intravenously three time a day (group C). 197 patients were enrolled in the study, and in 142 (48 in group A, 46 in group B and 48 in group C) we were able to make an evaluation.

RESULT

The overall efficacy (bacteriological eradication plus clinical cure or clear improvement) of ceftriaxone, cefotaxime and cefuroxime were 81%, 83%, 79% respectively (P > 0.05). The eradication rate for three groups were 80%, 78%, 75% (P > 0.05). No adverse events occured.

CONCLUSION

Data obtained in our study indicate that for the majority of patients with lower respiratory tract infections, 1 g ceftriaxone, 3 g cefotaxime and 2.25 g cefuroxime are effective and safe, and 7 days therapy is enough, but the use of 1 g ceftriaxone is more convenient.

[Retrocaval ureter]

OBJECTIVE

To improve the diagnosis of retrocaval ureter.

METHOD

20 cases of retrocaval ureter with an average age of 33.4 years were reported. The diagnosis of this disease depends on urography and retrograde ureterography. Operation was the principal treatment. Ureter orthopedics and reduction were performed in 19 cases of type 1 (low loop) except one case of type II (high loop). After removing 3 - 4 cm retrocaval ureter with pathological changes, we anastomosed the ureter without tension and regained its normal anatomic position.

RESULT

B-ultrasound and excretory urography showed no stenosis and improvement of hydronephrosis.

CONCLUSION

Ureter orthopedics and reduction are ideal for the treatment of retrocaval ureter.

3-Nitrotyrosine in the proteins of human plasma determined by an ELISA method

The modification of tyrosine residues in proteins to 3-nitrotyrosine by peroxynitrite or other potential nitrating agents has been detected in biological systems that are subject to oxidative stress. A convenient semi-quantitative method has been developed to assay nitrated proteins in biological fluids and homogenates using a competitive ELISA developed in our laboratory. This assay selectivity detected 3-nitro-l-tyrosine residues in a variety of peroxynitrite-treated proteins (BSA, human serum albumin (HSA), alpha1-antiprotease inhibitor, pepsinogen and fibrinogen) and also in a nitrated peptide, but had a low affinity for free 3-nitro-L-tyrosine and 3-chloro-L-tyrosine. The IC50 values for the inhibition of antibody binding by different nitrated proteins were in the range 5-100 nM, suggesting that the antibody discriminated between nitrotyrosine residues in different environments. The presence of nitrotyrosine in plasma proteins was detected by Western blot analysis and quantified by the ELISA. A concentration of 0. 12+/-0.01 microM nitro-BSA equivalents was measured in the proteins of normal plasma which was increased in peroxynitrite-treated plasma and was elevated in inflammatory conditions. HSA and low-density lipoprotein (LDL) isolated from plasma contained 0.085+/-0.04 and 0. 03+/-0.006 nmol nitro-BSA equivalents/mg protein, respectively. Comparison of the level of nitration in peroxynitrite-treated HSA and LDL in the presence and absence of plasma indicates that nitration and presumably oxidation is inhibited by plasma antioxidants. The presence of nitrotyrosine in LDL is consistent with previous reports implicating peroxynitrite in the oxidative modification of lipoproteins and the presence of a low concentration of oxidized LDL in the blood.

[The experimental study of the facial nerve regeneration in silicone chamber: the influence of nerve growth factor]

OBJECTIVE

To elucidate the role of NGF in the regeneration of facial nerve.

METHODS

The superior buccal division of facial nerve of adult New Zealand rabbit was transected and a nerve growth chamber created. The chamber of the experimental side was filled with NGF/normal saline and that of the control side with normal saline alone. Four and eight weeks after operation, the regenerated nerves in the chambers were dissected for histological studies.

RESULTS

Four weeks after operation, the average thickness of myelin sheath and the average number of myelinated axons were 0.779 +/- 0.475 micron, 2.024 +/- 1.999 (n = 11) in experimental group and 0.413 +/- 0.132 micron, 368 +/- 171 (n = 8) in control sides respectively. There was significant difference between the experimental sides and control sides (P < 0.05). Eight weeks after operation, the regenerated nerve appeared more mature. There were significant difference in the average diameters, the thickness of myelin sheath and the number of myelinated axons between the experimental and control sides (P < 0.05).

CONCLUSION

NGF within a silicone chamber enhanced facial nerve regeneration in New Zealand rabbits.

Histone H1 isoforms purified from rat liver bind nonspecifically to the nuclear factor 1 recognition sequence and serve as generalized transcriptional repressors

Two polypeptides with molecular masses of 34 and 30 kDa were copurified from rat liver during DNA affinity purification of a sequence-specific transcription factor binding to the footprint II sequence within the P2 promoter of the rat alpha1B adrenergic receptor (alpha1B AR) gene, and were identified by microsequencing their endoproteinase Lys-C-derived peptides as histone H1d and histone H1c, respectively. Histone H1 was previously reported to bind to the nuclear factor 1 (NF1) recognition sequence, although the specificity of this binding has been controversial. Here, DNA mobility shift and supershift assays, DNase I footprinting and mutational analyses indicated that the binding of histone H1 to the NF1 sites located within footprint II of the alpha1B AR gene P2 promoter is nonspecific. Transient cotransfections into Hep3B cells of histone H1d cDNA with CAT constructs containing promoter regions of different genes resulted in generalized and non-specific suppression of CAT activity. The histone H1d-mediated repression of the activities of the alpha1B AR gene P2/CAT or beta2 AR gene P(-186/1307)/CAT constructs was reversed by the cotransfection of a cDNA encoding the sequence-specific transcription factor NF1/X, and the fold increase in CAT activities was similar to that obtained in the absence of histone H1d. These results suggest that sequence-specific transcription factors counteract the histone H1-mediated transcriptional repression in vivo by a true activation, which is different from the in vitro antirepression in histone H1-repressed chromatin templates (Laybourn and Kadonaga, (1991) Science 254: 238-245).

Both the cyclic AMP response element and the activator protein 2 binding site mediate basal and cyclic AMP-induced transcription from the dominant promoter of the rat alpha 1B-adrenergic receptor gene in DDT1MF-2 cells

cAMP markedly increases alpha 1B adrenergic receptor (alpha 1B-AR) expression in FRTL-5 and PC C13 rat thyroid cells, DDT1MF-2 smooth muscle cells, primary rat hepatocytes, and K9 rat liver cells. Here, we used DDT1MF-2 cells to evaluate further the mechanisms by which cAMP stimulates alpha 1B-AR expression. Receptor binding assays, Northern blotting, and nuclear run-on analyses demonstrated that forskolin (1 microM) in the presence of isobutylmethylxanthine (0.25 mM) increased alpha 1B-AR numbers, mRNA level, and gene transcription rate by 2.3 +/- 0.2-, 2.5 +/- 0.3-, and 3.5 +/- 0.2-fold over control, respectively. Dibutyryl cAMP (1 mM) plus isobutylmethylxanthine (0.25 mM) also enhanced alpha 1B-AR density by 2.7 +/- 0.1-fold over control. Further experiments demonstrated that the induction of alpha 1B-AR by forskolin requires new protein synthesis and is protein kinase A dependent. In DDT1MF-2 cells transfected with alpha 1B-AR gene P2 promoter/CAT constructs, both forskolin and dibutyryl cAMP significantly increased P2 promoter activity. The P2 promoter region of the rat alpha 1B-AR gene (-813 to -432) contains a cAMP response element (CRE) (-444 to -437) and an AP2 binding site (-647 to -638). Mutations in either one of these elements alone led to a decrease in both basal and cAMP-induced P2 promoter activity. Mutations in both elements caused a further inhibition of basal transcription and a complete block of cAMP-induced P2 promoter activity. Direct binding of purified activator protein 2 (AP2) to the AP2 element in the P2 promoter was reported previously. Gel mobility shift and super-shift assays using liver nuclear extracts from either rat liver or DDT1MF-2 cells demonstrated that the CRE in the alpha 1B-AR gene bound CRE binding protein. These data indicate that both the CRE and the AP2 element in the P2 promoter contribute to basal as well as cAMP-induced transcription of the alpha 1B-AR gene in DDT1MF-2 cells.

Effects of short and long term ethanol on the activation of signal transducer and activator transcription factor 3 in normal and regenerating liver

Interleukin-6 (IL-6) induced activation of Signal Transducer and Activator Transcription Factor 3 (Stat3) is a critical step in liver regeneration. Chronic ethanol consumption is known to increase the plasma concentration of IL-6, yet the ability of the liver to regenerate and the regenerative induction of several IL-6 initiated events are impaired in chronic alcoholic liver disease. We hypothesized that chronic ethanol consumption inhibits IL-6 dependent signal transduction. To test this hypothesis, the effect of ethanol on the Stat3 signal transduction pathway was studied in the adult rat liver. In vitro treatment of freshly isolated normal adult rat hepatocytes with 50-100 mM ethanol for 30 min blocked IL-6-induced Stat3 activation. Long-term ethanol intake in vivo significantly attenuated the activation of Stat3 induced either in vivo by partial hepatectomy or in vitro by IL-6. In contrast, short-term ethanol consumption enhanced the regenerative induction of Stat3 but inhibited IL-6 induced Stat3 activation. These data suggest that the inhibition of liver regeneration by chronic ethanol consumption is, at least in part, mediated by modulating the activation of Stat3.

Sp1-mediated transcriptional activation from the dominant promoter of the rat alpha1B adrenergic receptor gene in DDT1MF-2 cells

In the rat liver, NF1 and CP1 bind to the major P2 promoter of the alpha1B adrenergic receptor gene to generate footprint II. Here we show that, in DDT1MF-2 smooth muscle cells, the major protein bound to footprint II is not NF1 but Sp1, which binds to the 5'-portion of the footprint II sequence (footprint IIb). Mutational analyses demonstrate that the CCCGCG sequence in footprint IIb is critical for Sp1 binding and P2 promoter activity. A second GC box in the P2 promoter also binds the Sp1 protein and contributes to the P2 promoter activity. Gel shift assays indicate that footprint II can bind Sp1, NF1, and CP1, and that the binding of these 3 proteins is mutually exclusive. This is also indicated by the results of functional cotransfection experiments, where transient overexpression of NF1 and Sp1 together caused a similar increase in the activity of a P2/CAT reporter construct as overexpression of either Sp1 or NF1 alone, indicating lack of additivity. The preferential interaction of footprint II with Sp1 in DDT1MF-2 cells and NF1 in liver appears to be due to low levels of NF1 expression in DDT1MF-2 cells and low levels of Sp1 in liver. These observations suggest that NF1 and Sp1 are the major transcription factors involved in controlling the P2 promoter in liver versus DDT1MF-2 cells, respectively, which may be one of the mechanisms responsible for the complex tissue-specific regulation of the expression of the alpha1B adrenergic receptor gene.

ATP-dependent K+ channel activation in isolated normal and hypertensive newborn and adult porcine pulmonary vessels

The role of an ATP-dependent K+ channel (K(ATP)+) relaxation in the porcine pulmonary vasculature from birth to adulthood was investigated in vitro using levcromakalim on isolated, prostaglandin F2alpha (30 microM)-precontracted conduit arteries (CA), resistance arteries (RA), and veins (PV). Vessels from neonatal pulmonary hypertensive piglets exposed to chronic hypobaric hypoxia (CHH, 51 kPa) for 3 d, either from birth or from 3 d of age were also studied. Levcromakalim relaxed all vessels in a concentration- and glibenclamide-sensitive manner. In normal CA, the maximal extent of relaxation and sensitivity (EC50) increased between birth and 17 d. Endothelium-removal increased EC50 at 17 d only. Indomethacin (10 microM), but not N(G)-monomethyl-L-arginine (L-NMMA) (30 microM), inhibited relaxation in CA from newborn, 3-d-old, and adult animals. In RA, levcromakalim-induced relaxations did not change during development and endothelium-removal attenuated relaxations in 3-d-old but not in adult animals. At both ages in RA, L-NMMA attenuated relaxations and subsequent addition of L-arginine (1 mM) restored them. In PV, maximal relaxation increased between birth and 6 d with no change of EC50. At all ages, relaxation was partially endothelium-dependent and inhibited by L-NMMA (except in the newborn). Indomethacin only attenuated relaxations in veins from 6- and 17-d-old animals. CHH did not influence relaxant responses in CA and PV but decreased EC50 in RA. Thus K(ATP)+ channel activation caused relaxation from birth onward in all vascular segments with varying endothelium dependence. CHH did not affect relaxation in the large vessels and up-regulated those in RA. These findings indicate a possible role for K(ATP)+ channels during normal adaptation and a potential therapeutic role in the management of pulmonary hypertensive newborn infants.

Differential regulation of the mitogen-activated protein and stress-activated protein kinase cascades by adrenergic agonists in quiescent and regenerating adult rat hepatocytes

To study the mechanisms by which catecholamines regulate hepatocyte proliferation after partial hepatectomy (PHX), hepatocytes were isolated from adult male rats 24 h after sham operation or two-thirds PHX and treated with catecholamines and other agonists. In freshly isolated sham cells, p42 mitogen-activated protein (MAP) kinase activity was stimulated by the alpha1-adrenergic agonist phenylephrine (PHE). Activation of p42 MAP kinase by growth factors was blunted by pretreatment of sham hepatocytes with glucagon but not by that with the beta2-adrenergic agonist isoproterenol (ISO). In PHX cells, the ability of PHE to activate p42 MAP kinase was dramatically reduced, whereas ISO became competent to inhibit p42 MAP kinase activation. PHE treatment of sham but not PHX and ISO treatment of PHX but not sham hepatocytes also activated the stress-activated protein (SAP) kinases p46/54 SAP kinase and p38 SAP kinase. These data demonstrate that an alpha1- to beta2-adrenergic receptor switch occurs upon PHX and results in an increase in SAP kinase versus MAP kinase signaling by catecholamines. In primary cultures of hepatocytes, ISO treatment of PHX but not sham cells inhibited [3H]thymidine incorporation. In contrast, PHE treatment of sham but not PHX cells stimulated [3H]thymidine incorporation, which was reduced by approximately 25 and approximately 95% with specific inhibitors of p42 MAP kinase and p38 SAP kinase function, respectively. Inhibition of the p38 SAP kinase also dramatically reduced basal [3H]thymidine incorporation. These data suggest that p38 SAP kinase plays a permissive role in liver regeneration. Alterations in the abilities of catecholamines to modulate the activities of protein kinase A and the MAP and SAP kinase pathways may represent one physiological mechanism by which these agonists can regulate hepatocyte proliferation after PHX.

[Effects of high-dose iodine on brain development in mice]

It is an important topic in medicine and genetics, which has not yet been studied in depth, that whether high-dose iodine, especially iodine excess in mother's body, can cause impediment of brain development in babies as iodine deficiency do. An animal model of goiter was reconstructed in mice with feeding them water containing high level of iodine for three months. Weight of brain, protein and nucleic acid concentrations were measured in one-, seven-, 14-, 21- and 30-day old young mice, and morphological changes in the brain and their abilities of learning and memory were observed in 30-day old young mice, born to mothers with high-iodine goiter. Results indicated that weight of brain, protein content, ratio of protein to DNA, RNA content, and ratio of RNA to DNA all decreased significantly, and DNA content increased in the brain of high-iodine mice, as compared with those in normal iodine mice. Abilities of learning and memory in 30-day old mice decreased. And, those changes began from the seventh to 14th days after their birth. It suggests that excessive intake of iodine, as iodine deficiency, can not only cause high-iodine goiter, but also damage nervous system leading to retardation of brain development and impediment of its function.

The plasma concentrations of lidocaine after slow versus rapid administration of an initial dose of epidural anesthesia

We measured venous blood concentrations of lidocaine in 15 patients undergoing lower abdominal or extremity surgery after epidural injection of lidocaine. Patients were divided into either an infusion group (Group I, n = 6) or a bolus injection group (Group II, n = 9). We administered 15 ml of 2% lidocaine into the epidural space at 1 mL/min in Group I and at 1 mL/3 in Group II. Venous blood was drawn at 3, 6, 9, 12, 15, 18, 21, 30, 60, and 90 min after injection for measurement of plasma lidocaine concentrations. The peak plasma concentration (Cmax) of lidocaine in Group I was significantly less than that in Group II (P < 0.0005). We conclude that slow epidural infusion can produce a lower Cmax of lidocaine compared with that of a bolus administration and thereby decrease the potential for systemic toxicity of the local anesthetic.

The sexually dimorphic nucleus of the hypothalamus contains GABA neurons in rat and man

The sexually dimorphic nucleus of the preoptic area (SDN-POA) is the most striking structure displaying a morphological sex difference in the rat brain. A potentially homologous nucleus has been identified in the human hypothalamus. The objective of the present study was to pursue the putative homology of the rat and human SDN-POA by determining whether they express the same transmitter phenotype. We employed in situ hybridization histochemistry for GAD mRNA to show whether the neurons of the SDN-POA produce GABA. In both the rat and human, high levels of GAD65 and GAD67 mRNA are present in most, if not all, SDN-POA neurons. No sex difference is evident in the level of expression in either the rat or human. The data indicate that neurons of the SDN-POA in both the rat and human are GABA-producing and argue for the homology of these nuclei in the rat and human hypothalamus.

Transcriptional regulation of alpha(1b) adrenergic receptors (alpha(1b)AR) by nuclear factor 1 (NF1): a decline in the concentration of NF1 correlates with the downregulation of alpha(1b)AR gene expression in regenerating liver

The 5' upstream region from --490 to --540 (footprint II) within the dominant P2 promoter of the rat alpha(1b) adrenergic receptor (alpha(1b)AR) gene is recognized by a sequence-specific DNA-binding protein (B. Gao, M. S. Spector, and G. Kunos, J. Biol. Chem. 270:5614-5619, 1995). This protein, detectable in Southwestern (DNA-protein) blots of crude nuclear extracts as 32- and 34-kDa bands, has been purified 6,000-fold from rat livers by DEAE-Sepharose, heparin-Sepharose, and DNA affinity chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and UV cross-linking of the purified protein indicated the same molecular mass as that in crude extracts. Methylation interference analysis revealed strong contact with a TTGGCT hexamer and weak contact with a TGGCGT hexamer in the 3' and 5' portions of footprint II, respectively. Nucleotide substitutions within these hexamers significantly reduced protein binding to footprint II and the promoter activity of P2 in Hep3B cells. The purified protein also bound to the nuclear factor 1 (NF1)/CTF consensus sequence, albeit with lower affinity. Gel mobility supershift and Western blotting (immunoblotting) analyses using an antibody against the NF1/CTF protein identified the purified 32- and 34-kDa polypeptides as NF1 or a related protein. Cotransfection into Hep3B cells or primary rat hepatocytes of cDNAs of the NF1-like proteins NF1/L, NF1/X, and NF1/Redl resulted in a three- to fivefold increase in transcription directed by wild-type P2 but not by the mutated P2. Partial hepatectomy markedly decreased the levels of NF1 in the remnant liver and its binding to P2, which paralleled declines in the rate of transcription of the alpha(1b)AR gene and in the steady-state levels of its mRNA. These observations indicate that NF1 activates transcription of the rat alpha(1b)AR gene via interacting with its P2 promoter and that a decline in the expression of NF1 is one of the mechanisms responsible for the reduced expression of the alpha(1b)AR gene during liver regeneration.

A novel Escherichia coli vector for oxygen-inducible high level expression of foreign genes

By utilizing the oxygen-sensitive Escherichia coli Mn-superoxide dismutase (Mn-SOD) promoter, we have developed a vector system that expresses high levels of cloned foreign genes. The promoter for the bacterial Mn-SOD, as well as both 5'-untranslated and transcriptional termination sequences were ligated to a synthetic linker containing two restriction enzyme cloning sites. The vector also contained the gene for beta-lactamase, which confers ampicillin resistance to the host bacterium and provides a selectable marker. After screening and selection, high level of expression was achieved by exposure to the superoxide-generating agent paraquat (methyl viologen) as the inducer. To test the vector, both native and mutated human Mn-SOD cDNAs were cloned and expressed, respectively. To determine the optimal concentration of inducer necessary for maximal expression, recombinant bacteria were exposed to increasing concentrations of paraquat and subsequently assayed for superoxide dismutase (SOD) activity. The highest expression was induced by 20 microM paraquat, and approached 50% of total soluble protein.

DNA elements and protein factors involved in the transcription of the beta 2-adrenergic receptor gene in rat liver. The negative regulatory role of C/EBP alpha

Primer extension and RNase protection analyses of the rat beta 2-adrenergic receptor (beta 2AR) gene identify two transcription start points at -64 and -220 nt, respectively. Transient transfections of putative promoter/pCAT constructs into DDT1 MF-2 cells indicate that fragments -36 to -100 (PI) and -186 to -312 (P2) are sufficient to promote transcription, whereas -911 to -1122 contains a negative regulatory element(s). RNase protection analysis of the 3' untranslated region (3'-UTR) indicates the presence of two transcripts with 3'-UTR of 111 and 604 nt exclusive of the poly(A+) tails. Northern blots of beta 2AR mRNA using full-length and partial cDNA probes indicate that a major 2.2 kb and a minor 1.6 kb species arise from the use of alternative promoters as well as different polyadenylation signals. DNase I footprinting and DNA mobility shift assays (DMSA) using rat liver nuclear extracts identify a number of transcription factors binding to sequence elements within or upstream from P1 and P2, including Spl, CRE, CPl, AP-2, NF-1, NF-kappa B, and C/EBP. Supershift assays using antibodies against C/EBP alpha and C/EBP beta and mutational analyses indicate that the protein binding to the C/EBP consensus recognition site at -925 to -933 is C/EBP alpha. The activity of promoter/CAT constructs containing the C/EBP recognition site is significantly decreased by cotransfection of C/EBP alpha but not C/EBP alpha but not C/EBP beta into either DDT1 MF-2 cells or primary rat hepatocytes. Partial hepatectomy causes a transient decrease in C/EBP alpha, as measured by DMSA, and an increase in beta 2 AR mRNA levels and rate of transcription in the remnant liver. Thus, derepression via C/EBP alpha is likely involved in the up-regulation of beta 2AR in the regenerating rat liver.

Elucidation of the core residues of an epitope using membrane-based combinatorial peptide libraries

Combinatorial peptide libraries have proved to be a valuable tool for the study of the interaction of a functional protein with its ligand. Here, the epitope for a monoclonal antibody 201/9, raised against beta-factor XIIa, has been identified with a two-step approach using peptide libraries attached to a polymer (polyvinylidene difluoride) membrane. First, the octapeptide libraries with two amino acids defined at position 2 and 4, represented by the formula X-O2-X-O4-X-X-X-X, were synthesized on a sheet of polymer membrane in which X represents a mixture of all the natural -amino acids except cysteine, while O2 and O4 each represent a single amino acid. The libraries were probed with the antibody 201/9, and the bound antibody was detected with a sensitive chemiluminescent method. In the first cycle, the peptide mixtures X-Phe-X-Gln-X-X-X-X showed the strongest signal development. In the second cycle Phe and Gln were incorporated into new libraries consisting of sequences O1-Phe-X-Gln-X-X-X-X, X-Phe-O3-Gln-X-X-X-X, X-Phe-X-Gln-O5-X-X-X, X-Phe-X-Gln-X-O6-X-X, X-Phe-X-Gln-X-X-O7-X, and X-Phe-X-Gln-X-X-X-O8. After probing these new peptides, the residues representing the core sequence of the epitope for monoclonal antibody 201/9 were elucidated. The sequence Ser-Phe-Leu-Gln-Glu-Asn, identified as the immunodominant epitope, correlates well with the sequence Ser-Phe-Leu-Gln-Glu-Ala previously identified (Gao, B., and Esnouf, M. P. (1996) J. Immunol. 157, 183-188) in a scan of overlapping peptides based on the sequence of human beta-factor XIIa.

Effect of constitutive 70-kDa heat shock protein polymerization on its interaction with protein substrate

Constitutive 70-kDa heat shock protein (hsc70) is a mixture of monomers and oligomers in ADP, while in ATP it is monomeric unless certain DnaJ homologs are present which induce hsc70 to form large polymers in an ATP-dependent reaction. A key question regarding polymerized hsc70 is whether it is able to bind protein substrates. Polymerized BiP, the hsc70 present in the endoplasmic reticulum, has been found to bind substrates in vitro although substrates appear to bind only to monomeric BiP in vivo. In this study, we investigated whether substrate binds to polymerized cytoplasmic hsc70 in vitro. Although both stoichiometric ATP and high concentrations of cytochrome c peptide monomerized hsc70, direct binding studies provided no evidence that cytochrome c peptide binds to polymerized hsc70. Furthermore, the time course of cytochrome c peptide and clathrin binding to hsc70 suggested that rather than binding to polymerized hsc70, they monomerized it by reducing free monomer, thereby shifting the monomer-polymer equilibrium toward monomer. We conclude that peptide and protein substrates bind at least an order of magnitude more weakly to polymerized hsc70 than to monomer, suggesting that polymerization of hsc70 in vivo, perhaps by DnaJ homologs, may store it in an inactive form.

Multiple interactive residues of recognition: elucidation of discontinuous epitopes with linear peptides

The discontinuous epitopes of beta-factor XIIa for three mAbs were mapped by a linear peptide-based immunoblotting technique, referred to as multiple interactive residues of recognition. The Abs were incubated with a set of overlapping synthetic peptides, deduced from the cDNA sequences of beta-factor XIIa, on a polymer membrane, and the signal was amplified by an ECL assay. Several discrete sequences of the protein were recognized by each Ab. The recognized peptides were further characterized using alanine substitution analogues and peptides of different lengths. The discontinuous epitopes found for each Ab were formed by several peptides and were composed of 20 to 31 residues. The sequence FLQEA was recognized by all three Abs and was the immunodominant peptide. Abs 201/9 and 2/15 bound to very similar discontinuous sequences, but with subtle differences. The sequences 76RLHEAFSP83, 88HDLALLRLQE97, 178GFLEG182, 146FLQEA150, and 237IRE239 formed the epitope for mAb 201/9, whereas 76RLHEAFSP83, 90LALLRLQE97, 146FLQEA150, and 235AWIREHT241 formed the epitope for Ab 2/15. The third Ab 202/7 recognized the sequences 79EAFSP83, 93LRLQE97, 133WGHQF137, and 146FLQEA150. We suggest that these sequences represent the sites to which the Abs bind. This procedure provides a sensitive and convenient tool to elucidate discontinuous epitopes for the binding of Abs, receptor ligand-binding sites, or enzyme inhibitor binding sites.

Multiple interactive residues of recognition: elucidation of discontinuous epitopes with linear peptides

The discontinuous epitopes of beta-factor XIIa for three mAbs were mapped by a linear peptide-based immunoblotting technique, referred to as multiple interactive residues of recognition. The Abs were incubated with a set of overlapping synthetic peptides, deduced from the cDNA sequences of beta-factor XIIa, on a polymer membrane, and the signal was amplified by an ECL assay. Several discrete sequences of the protein were recognized by each Ab. The recognized peptides were further characterized using alanine substitution analogues and peptides of different lengths. The discontinuous epitopes found for each Ab were formed by several peptides and were composed of 20 to 31 residues. The sequence FLQEA was recognized by all three Abs and was the immunodominant peptide. Abs 201/9 and 2/15 bound to very similar discontinuous sequences, but with subtle differences. The sequences 76RLHEAFSP83, 88HDLALLRLQE97, 178GFLEG182, 146FLQEA150, and 237IRE239 formed the epitope for mAb 201/9, whereas 76RLHEAFSP83, 90LALLRLQE97, 146FLQEA150, and 235AWIREHT241 formed the epitope for Ab 2/15. The third Ab 202/7 recognized the sequences 79EAFSP83, 93LRLQE97, 133WGHQF137, and 146FLQEA150. We suggest that these sequences represent the sites to which the Abs bind. This procedure provides a sensitive and convenient tool to elucidate discontinuous epitopes for the binding of Abs, receptor ligand-binding sites, or enzyme inhibitor binding sites.

Glutamic acid decarboxylase message isoforms in human suprachiasmatic nucleus

The rat suprachiasmatic nucleus (SCN) is comprised of neurons that contain gamma-amino butyric acid (GABA) colocalized with one or more peptides. In the present study, the authors employed in situ hybridization histochemistry to determine whether the human SCN also contains GABA neurons using synthetic oligonucleotide probes complementary to sequences of two isoforms of the GABA-forming enzyme, glutamic acid decarboxylase (GAD), GAD65, and GAD67. Most, if not all, SCN neurons appear to express both GAD65 mRNA and GAD67 mRNA with the content of GAD67 greater than GAD65. Both isoforms also are expressed in some neurons of the anterior hypothalamic area, in small neurons of the paraventricular nucleus but not in the supraoptic nucleus. These data indicate that neurons in the human SCN, like those in rodents, use GABA as a neurotransmitter.

[The value of determining guanine deaminase in diagnosis of hepatic diseases]

We determined the Guanine Deaminase (GD) activity of 200 patients with different diseases. It was found that GD activity of hepatic patients is higher than that of health adults, while the GD activity of other patients is in the normal range. There is a linear correlation between GD activity and ALT in patients with chronic hepatitis, billiary obstruction, and between GD activity and total bilirubin in patients with chronic active hepatitis, biliary obstruction and liver cirrhosis. Moreover, the GD activity of patients positive for anti-HCV is significantly increased. So GD activity in serum is a specific and sensitive index to estimating hepatic functions and can be used in the diagnosis of acute and chronic hepatitis, cirrhosis of liver, and C virus hepatitis.

[Chemical constituents from the aerial part of Epimedium brevicornum Maxim]

Six flavonoids were isolated from the aerial part of Epimedium brevicornum and identified as baohuo side I, 2"' O-rhamnosyl icariside II, sagittatoside B, baohuoside II, ikarisoside F and ikarisoside C by means of UV, IR, 1H-NMR, 13C-NMR and FAB-MS spectral analysis, they were isolated from this plant for the first time.

Tests for possible effects of selection by domestic pyrethroids for resistance in culicine and anopheline mosquitoes in Sichuan and Hubei, China

Resistance tests, by conventional methods and by observing the time for knockdown, showed no evidence for any build up of resistance to deltamethrin in malaria vectors from areas where millions of bednets have been treated with this compound annually for up to 7 years. However, a strain of Culex quinquefasciatus which had been bred in a factory in which volatile pyrethroids are handled had developed unequivocal resistance to deltamethrin. Observation of the time for knockdown gave clearer discrimination between resistant and susceptible strains than did observation of percentage mortality after a standard exposure time.

GABAA-receptor subunit composition in the circadian timing system

In the present study, the distribution of GABAA-receptor alpha 1-, alpha 2-, alpha 3-, alpha 5-, beta 2.3- and gamma 2-subunits were localized immunohistochemically with subunit specific antibodies in the rat circadian timing system (CTS). The areas examined include the principal circadian pacemaker, the suprachiasmatic nucleus (SCN), and areas that receive important SCN input including the intergeniculate leaflet (IGL), subparaventricular zone (SPVZ), paraventricular hypothalamic nucleus (PVH), the retrochiasmatic area (RCh) and the paraventricular nucleus of the thalamus (PVT). The SCN has an unusual pattern with immunoreactivity for the alpha 2-, alpha 3-, alpha 5-, and gamma 2-subunits but not for the commonly expressed alpha 1- and beta 2.3-subunits. In all of the areas receiving SCN efferent input (SPVZ, PVH, RCh, PVT and IGL), staining is present either for all six subunits or for the three common subunits, alpha 1-, beta 2.3-, and gamma 2. There is some evidence for a differential distribution of subunits at the cellular level. The alpha 2-, and beta 2.3-subunits are predominantly expressed in neuropil, the alpha 3-, alpha 5- and gamma 2-subunits are predominantly expressed over perikarya and the alpha 1-subunit is expressed over both neuropil and perikarya in the areas in which subunit immunoreactivity is found. The demonstration of this regional and cellular expression of GABAA-receptor subunits should contribute to our understanding of GABAergic neurotransmission in the CTS.

Interaction of nucleotide-free Hsc70 with clathrin and peptide and effect of ATP analogues

The functions of the 70 kDa heat-shock proteins (hsp70s) are regulated by their bound nucleotide. We previously observed major differences in the effect of bound ATP and ADP on the interaction of hsc70 (constitutive hsp70) with its protein substrates. In the present study, we investigated the interaction of protein substrates with nucleotide-free hsc70 and with hsc70 with bound ATP analogues. We found, first, that nucleotide-free hsc70 appeared to interact differently with different substrates. Specifically, nucleotide-free hsc70 behaved much more like hsc70-ATP than hsc70-ADP in that clathrin very rapidly bound to and dissociated from nucleotide-free hsc70 in contrast to its very slow binding to and dissociation from hsc70-ADP. On the other hand, nucleotide-free hsc70 behaved more like hsc70-ADP than hsc70-ATP in that cytochrome c peptide dissociated very slowly from nucleotide-free hsc70 compared to its rapid dissociation from hsc70-ATP. Second, binding of the ATP analogues AMP-PNP, dATP, and ATP gamma S to nucleotide-free hsc70 had very little further effect on the properties of the nucleotide-free hsc70. Therefore, previously observed effects of ATP analogues may have been due to removal of the bound ADP rather than to the presence of analogues.

Cerebellar granule cells in vitro recapitulate the in vivo pattern of GABAA-receptor subunit expression

GABAA-receptor heterogeneity is based on the combinatorial assembly of a family of 15 subunits (alpha 1-6, beta 1-3, gamma 1-3, delta, rho 1-2) into multiple receptor subtypes. The factors regulating the differential expression of GABAA-receptor subtypes in the CNS are largely unknown. In the present study, we have used primary cultures of rat cerebellar granule cells as model system to analyze to which extent the expression, subunit composition, and subcellular localization of GABAA-receptors depend on signals available in the cerebellum in vivo, in particular GABAergic input which is lost in vitro. GABAA-receptor subunits were visualized immunohistochemically with subunit-specific antibodies and their subcellular localization was investigated by confocal laser microscopy with selective markers for dendritic proteins (microtubule-associated protein 2, non-phosphorylated neurofilaments) and synaptic vesicles (synaptophysin). Triple immunofluorescence staining experiments revealed that dissociated granule cells taken from 7-day-old rats and maintained in culture for 9 days co-expressed the subunits alpha 1 alpha 6 beta 2,3 gamma 2 delta, a subunit repertoire which is identical to that seen in vivo in the adult cerebellum. GABAA-receptor subunits were localized selectively in granule cell somata and in proximal neurites immunopositive for MAP-2. No staining was detected in distal neurites immunopositive for neurofilaments. GABAA-receptor subunits frequently were aggregated in clusters closely apposed to synaptophysin-immunoreactive varicosities, suggesting a post-synaptic localization. Thus, major functional determinants of GABAA-receptors in granule cells (subunit repertoire, subcellular segregation and clustering in post-synaptic sites) develop in vitro, indicating that they are regulated to a large extent by intrinsic factors, independently of GABAergic input.

Analysis of heterogeneity of gene products (interferon) expressed in yeast

FPLC, SDS-PAGE and Western blot techniques are used to analyse the heterogeneity of interferon alpha A (IFN-alpha A) expressed in yeast. The heterogeneity consists of (i) the presence of IFN polymer, (ii) partial processing of signal leader peptide and (iii) internal degradation. The reasons for heterogeneity of gene products in expression system of yeast are analysed. The methods of avoiding heterogeneity, such as depolymerization, adding inhibitors of protease to the culture supernatant, the oligonucleotide-directed deletion mutagenesis and improvements of fermentation, are discussed.

[Protective action of Lycium barbarum L. (LbL) and betaine on lipid peroxidation of erythrocyte membrane induced by H2O2]

H2O2 was used to induce lipid peroxidation of RBC membrane in rats to observe the protective action of different ingredients of LbL and betaine on the membrane. The result shows these ingredients cna inhibit the lipid peroxidation of RBC membrane in the following order of antioxidizing power: Fructus Lycii.LbL.dry(FL/LbL.dry) > Polysaccharide FL/LbL > Residue FL/LbL > betaine.

The rat alpha 1B adrenergic receptor gene middle promoter contains multiple binding sites for sequence-specific proteins including a novel ubiquitous transcription factor

Transcription of the rat alpha 1B adrenergic receptor (alpha 1BAR) gene in the liver is controlled by three promoters that generate three mRNAs. The middle promoter (P2), located between -432 and -813 base pairs upstream from the translation start codon and lacking a TATA box, is responsible for generating the major, 2.7-kilobase mRNA-species expressed in many tissues (Gao, B., and Kunos, G. (1994) J. Biol. Chem. 269, 15762-15767). DNase I footprinting using rat liver nuclear extracts identified three protected regions in P2: footprint I (-432 to -452), footprint II (-490 to -540), and footprint III (-609 to -690). Putative response elements in footprints I and III were not analyzed except the AP2 binding site in footprint III, which could be protected by purified AP2 protein. Footprint II contains four sites corresponding to half of the NF-I consensus sequence, but DNA mobility shift assays indicate that this footprint binds two proteins distinct from NF-I: a ubiquitous CP1-related factor and another novel factor, termed alpha-Adrenergic Receptor Transcription Factor (alpha ARTF), which binds to two separate sites in this region. The alpha ARTF is widely distributed, with the highest amounts found in brain, followed by liver, kidney, lung, and spleen, but no detectable activity in heart. Deletions of alpha ARTF binding sites nearly abolished P2 promoter activity, which suggests that the alpha ARTF is essential for the transcription of the alpha 1BAR gene in most tissues.

Identification of distinct GABAA-receptor subtypes in cholinergic and parvalbumin-positive neurons of the rat and marmoset medial septum-diagonal band complex

GABAA-receptor heterogeneity is based on a multiplicity of subunits (alpha 1-6, beta 1-4, gamma 1-4, delta, rho 1-2) encoded by distinct genes. Flexibility in GABAergic signal transduction and allosteric modulation is expected to arise from the differential assembly of subunits into receptor subtypes. The aim of the present study was to investigate the potential diversity of receptor subtypes expressed by defined neuron populations, as identified by their neurotransmitter phenotype. To this end we have determined immunohistochemically the subunit repertoire of cholinergic and GABAergic neurons in the basal forebrain of rat and marmoset monkey, focusing on the medial septum-diagonal band complex. Co-localization of the GABAA-receptor subunits alpha 1, alpha 3, beta 2, beta 3, and gamma 2 with markers of cholinergic and GABAergic neurons (choline acetyltransferase and parvalbumin, respectively) was assessed by double- and triple immunofluorescence staining. The results reveal that cholinergic neurons in the rat basal forebrain are typically characterized by the subunit combination alpha 3/beta 3/gamma 2, whereas most of the parvalbumin-positive GABAergic neurons express either the subunit combination alpha 1/beta 2/gamma 2 or the combination alpha 1/alpha 3/beta 2/gamma 2. A similar pattern was observed in marmoset monkey, with GABAA-receptors containing the alpha 1-subunit being associated with parvalbumin-positive cells, but never with cholinergic neurons. Thus, the expression of distinct subunit repertoires by cholinergic and GABAergic neurons points to a functional specialization which is conserved across species. These subunit combinations are likely to correspond to different receptor subtypes, and may reflect the engagement of cholinergic and GABAergic neurons in distinct neuronal circuits in the basal forebrain.

Application of the time-dependent Green's function and Fourier transforms to the solution of the bioheat equation

A theory for solving the bioheat equation is developed using a time-dependent Green's function and Fourier transform techniques. The description of both steady-state and time-dependent data are placed into a single framework which can also describe the effects of inhomogeneous blood perfusion. The theory is illustrated by examples including the modelling of a thermal conduction hyperthermia system and a new RF interstitial system. A possibility for measuring the blood perfusion parameter and thermal conductivity from the steady state temperature distribution of a point source is also proposed.

A site-directed mutant of Cu,Zn-superoxide dismutase modeled after native extracellular superoxide dismutase

The well-studied cytosolic Cu,Zn-superoxide dismutase (SOD) protects against reperfusion injury, although its short (6 min) plasma half-life and negative charge create undesirable pharmacokinetics. We have designed, cloned, and expressed a genetic variant of SOD with altered pharmacological properties. A fusion gene consisting of the entire coding region of human SOD followed by a positively charged carboxy-terminal (C-terminal) "tail" of eight glycine and six arginine residues was constructed. The tail was modeled after the extracellular SOD (EC-SOD) C-terminal 26-amino acid basic peptide. This EC-SOD tail binds to heparin-like proteoglycans on cell surfaces and contributes to the enzyme's very long (30 h) plasma clearance time. After expression in Escherichia coli, the mutant enzyme was purified and characterized. No differences in specific activity or UV absorption spectrum between the mutant and the native enzyme were found. The thermal stability of the fusion protein was greater than that of native SOD. Although native SOD has no affinity for heparin, the modified enzyme bound to a heparin-agarose column. A "designer" SOD able to bind to cell surfaces may aid in the prevention of superoxide-mediated endothelial damage.

Neutrophil-generated free radicals: possible mechanisms of injury in adult respiratory distress syndrome

The acute lung injury resulting from adult respiratory distress syndrome (ARDS) is thought to be largely mediated by activated neutrophils. Because activated neutrophils produce the superoxide radical, which is both bacterial and cytotoxic to host cells, this oxygen-derived free radical is likely responsible for at least part of the neutrophil-mediated lung injury. In a rat model of ARDS resulting from intratracheal instillation of interleukin-1, recombinant human manganous superoxide dismutase significantly decreased lung leak. One detrimental action of proteases released by adherent neutrophils may be the degradation of extracellular superoxide dismutase (ECSOD), which normally binds to the heparan sulfate on the surface the endothelium. We found that rabbit ECSOD incubated with either trypsin or activated neutrophils loses affinity for heparin. Furthermore, soluble ECSOD is elevated in the serum of patients with ARDS, consistent with this hypothesis.

Transcription of the rat alpha 1B adrenergic receptor gene in liver is controlled by three promoters

The proximal 5'-flanking region of the rat alpha 1B adrenergic receptor (alpha 1BAR) gene contains discrete transcription start points (tsp) utilized in liver, located at -54, -57 (tsp1), and -443 base pairs (tsp2) upstream from the translation start codon (Gao, B., and Kunos, G. (1993) Gene (Amst.) 131, 243-247). Primer extension analyses using 5' upstream primers now identify an additional cluster of tsp between -1035 and -1340 base pairs (tsp3). Northern blots of rat liver mRNA reveal three alpha 1BAR mRNAs of 2.3, 2.7, and 3.3 kilobases in length. Transient transfections of putative promoter/pCAT constructs document the existence of three promoters, P1 (-127, -49), P2- (-813, -432), and P3 (-1363, -1107), which direct transcription from tsp1, tsp2, and tsp3, respectively. P1 contains no recognition sequences for known transcription factors. P2 is (G + C)-rich, lacks a TATA box, and contains a cAMP response element, GC, CACC, and GCAAT boxes, and binding sites for nuclear factor I. P3 contains a putative TATATA and CCAAT box and is flanked by recognition sites for the liver-specific CCAAT/enhancer binding protein and hepatocyte nuclear factor 5. These findings indicate that heterogeneity of alpha 1BAR mRNA in liver is related to transcription of the gene by three distinct promoters. Differential control of these promoters may underlie the well documented developmental and tissue-specific regulation of the alpha 1BAR.

Effects of acute and chronic administration of the antidepressants, imipramine, phenelzine and mianserin, on the social behaviour of mice

Effects of imipramine, phenelzine and mianserin on the behaviour of male CDl mice were examined after a single intraperitoneal injection (imipramine, 15.8 and 63.2 mumol/kg; phenelzine, 1 and 8 mumol/kg); mianserin, 0.12 and 0.48 mumol/kg) and after administration for 12-16 days in the drinking fluid (mean daily intake; imipramine, 15.8 and 63.2 mumol/kg; phenelzine, 1 and 8 mumol/kg; mianserin, 0.12, 0.48 and 1.92 mumol/kg). Behaviour was examined by ethological procedures during 5 min encounters with an untreated partner in a familiar situation, the animal's home cage, and in the more aversive environment of an unfamiliar cage. At 30 min after injection, the higher doses of acutely administered imipramine and mianserin decreased aggressive behaviour in the unfamiliar cage. In the home cage, effects of mianserin were only slight, whereas imipramine reduced social investigation at the larger dose and in both test environments decreased digging. Phenelzine increased social investigation in both environments. After chronic administration, each of the drugs increased social investigation in the neutral cage and home cage at some of the dose levels, indicating potential anxiolytic efficacy. Mianserin showed the additional effect of enhancing digging during tests in the neutral cage, which may correlate with its anxiolytic actions. Phenelzine was the only antidepressant to increase aggression during encounters in the neutral cage after chronic administration. The significance of these findings is discussed.

Selective allocation of GABAA receptors containing the alpha 1 subunit to neurochemically distinct subpopulations of rat hippocampal interneurons

The identification of a large variety of GABAA receptor subunits by molecular cloning suggests the existence of multiple receptor subtypes differing in localization and functional properties. In the present study we analysed immunohistochemically the cellular distribution of GABAA receptors containing the alpha 1 subunit in the rat hippocampus with a subunit-specific antiserum. Prominent staining of numerous interneurons was evident in Ammon's horn and the dentate gyrus, which contrasted with moderate and diffuse immunoreactivity in the dendritic layers of pyramidal and granule cells. Double immunofluorescence staining with antibodies to GABA revealed that a subset of GABAergic neurons in the hippocampus were immunoreactive for the alpha 1 subunit. To determine whether these cells represent distinct subpopulations of interneurons, we analysed the co-localization of the GABAA receptor alpha 1 subunit with selective markers of hippocampal interneurons (selected calcium-binding proteins and neuropeptides). In both Ammon's horn and the dentate gyrus, all parvalbumin-positive neurons and 50% of calretinin-positive neurons were double-labelled, whereas interneurons containing calbindin-D28k were devoid of alpha 1 subunit staining. Similarly, most neurons positive for neuropeptide Y and a subset of somatostatin-positive cells were double-labelled, in contrast to cholecystokinin- and vasoactive intestinal peptide-containing cells, which lacked the alpha 1 subunit staining. These results demonstrate cell-specific expression of GABAA receptors containing the alpha 1 subunit among subsets of hippocampal interneurons, pointing to a pronounced functional specialization of these cells. Furthermore, the prominent expression of GABAA receptors by interneurons suggests that disinhibition may be of major functional relevance in regulating the balance between excitation and inhibition in hippocampal circuits.

Characterization of nucleotide-free uncoating ATPase and its binding to ATP, ADP, and ATP analogues

The interactions of the 70-kDa heat-shock proteins (hsp70s) with their protein substrates appear to be regulated by bound nucleotide. Previous work has shown that the nucleotide binding site of the bovine brain uncoating ATPase, a constitutive member of the hsp70 family, crystallographically resembles the nucleotide binding site of actin and, like actin, the uncoating ATPase has a strongly bound ADP which cannot be removed by dialysis or treatment with ethylenediaminetetraacetic acid (EDTA). This suggests that, like the bound nucleotide of actin, it may be required for the enzyme to retain its native structure. In this study, the strongly bound ADP was removed by first replacing it with 5'-adenylyl imidodiphosphate (AMP-PNP) and then removing the bound AMP-PNP by dialysis. Following this treatment, more than 95% of the uncoating ATPase becomes nucleotide-free. The nucleotide-free uncoating ATPase retains its ability to bind and hydrolyze ATP and to uncoat clathrin-coated vesicles, even after 10 days of storage at 4 degrees C. Therefore, in contrast to actin, the bound nucleotide of the uncoating ATPase is not required to prevent denaturation of the enzyme. Using nucleotide-free uncoating ATPase, we were able to accurately measure the dissociation constants of ATP, ADP, and the nucleotide analogues AMP-PNP and 2'-deoxyadenosine 5'-triphosphate (dATP). The dissociation constants of both ATP and ADP are about 10(-8) M, more than 1-2 orders of magnitude stronger than previously reported, while AMP-PNP and dATP bind 2-3 orders of magnitude more weakly than ATP.