Effect of endurance training on lipid metabolism in women: a potential role for PPARalpha in the metabolic response to training

Endurance training increases fatty acid oxidation (FAO) and skeletal muscle oxidative capacity. However, the source of the additional fat and the mechanisms for increasing FAO capacity in muscle are not clear. We measured whole body and regional lipolytic activity and whole body and plasma FAO in six lean women during 90 min of bicycling exercise (50% pretraining peak O(2) consumption) before and after 12 wk of endurance training. We also assessed skeletal muscle content of peroxisome proliferator-activated receptor-alpha (PPARalpha) and its target proteins that regulate FAO [medium-chain and very long chain acyl-CoA dehydrogenase (MCAD and VLCAD)]. Despite a 25% increase in whole body FAO during exercise after training (P < 0.05), training did not alter regional adipose tissue lipolysis (abdominal: 0.56 +/- 0.26 and 0.57 +/- 0.10 micromol x 100 g(-1) x min(-1); femoral: 0.13 +/- 0.07 and 0.09 +/- 0.02 micromol x 100 g(-1) x min(-1)), whole body palmitate rate of appearance in plasma (168 +/- 18 and 150 +/- 25 micromol/min), and plasma FAO (554 +/- 61 and 601 +/- 45 micromol/min). However, training doubled the levels of muscle PPARalpha, MCAD, and VLCAD. We conclude that training increases the use of nonplasma fatty acids and may enhance skeletal muscle oxidative capacity by PPARalpha regulation of gene expression.

[Advances in diagnosis and treatment of ectopic pregnancy during the past ten years]

OBJECTIVE

To investigate the changes of diagnosis and treatment of ectopic pregnancy (EP) during the past ten years.

METHODS

Medical records of 1,970 cases with EP seen in our hospital from Jan. 1987 to Dec. 1996 were collected and analyzed retrospectively.

RESULTS

(1) The incidence of EP increases from 1.0 per 42.4 labours during 1987-1988 to 1.0 per 6.6 labours in 1995-1996. (2) Diagnosis was confirmed more by television laparoscopy, transvaginal ultrasonography and sensitive human chorionic gonadotropin-beta subunit assay rather than loparotomy and with a shorter period, (6.5 +/- 0.7) days in 1987-1988 versus (3.7 +/- 0.2) days in 1995-1996. (3) The choice of treatment was more conservative or through laparoscopic surgery than abdominal salpingectomy. (4) The success rate of conservative surgery expectant management reached 100.0% and medical treatment with a variety of choices around 80.0%-85.%.

CONCLUSIONS

Although the incidence of EP increased, with the improvement of diagnostic approaches, patients were detected at an earlier stage and possible to be treated more conservatively.

Arthropod- and host-specific Borrelia burgdorferi bbk32 expression and the inhibition of spirochete transmission

Antisera to BBK32 (a Borrelia burgdorferi fibronectin-binding protein) and BBK50, two Ags synthesized during infection, protect mice from experimental syringe-borne Lyme borreliosis. Therefore, B. burgdorferi bbk32 and bbk50 expression within Ixodes scapularis ticks and the murine host, and the effect of BBK32 and BBK50 antisera on spirochetes throughout the vector-host life cycle were investigated. bbk32 and bbk50 mRNA and protein were first detected within engorged ticks, demonstrating regulated expression within the vector. Then bbk32 expression increased in mice at the cutaneous site of inoculation. During disseminated murine infection, bbk32 and bbk50 were expressed in several murine tissues, and mRNA levels were greatest in the heart and spleen at 30 days. BBK32 antisera protected mice from tick-borne B. burgdorferi infection and spirochete numbers were reduced by 90% within nymphs that engorged on immunized mice. Moreover, 75% of these ticks did not retain spirochetes upon molting, and subsequent B. burgdorferi transmission by adult ticks was impaired. Larval acquisition of B. burgdorferi by I. scapularis was also inhibited by BBK32 antisera. These data demonstrate that bbk32 and bbk50 are expressed during tick engorgement and that BBK32 antisera can interfere with spirochete transmission at various stages of the vector-host life cycle. These studies provide insight into mechanisms of immunity to Lyme borreliosis and other vector-borne diseases.

Effects of CTx and 8-bromo-cAMP on LPS-induced gene expression of cytokines in murine peritoneal macrophages

LPS, an endotoxin isolated from gram-negative bacterial, has been shown to be a potent cytokine initiator in murine peritoneal macrophages. CAMP-dependent pathway is generally considered to play a suppressive role in immune response. This study investigated the effect of cAMP on LPS-induced gene expression of cytokines in murine macrophages. Our data clearly demonstrated that in LPS-treated macrophages, cAMP elevator (CTx and 8-bromo-cAMP) could increase IL-1Ra and IL-10 gene expression, while mRNAs of IL-1alpha, IL-12, IL-6, and MIF were decreased and other cytokines like IL-1beta, and IFN-gamma did not give a definite tendency. This is the first report that CTx and 8-bromo-cAMP positively regulate IL-1Ra gene expression in LPS-stimulated macrophages. Our data also suggest that a cAMP-dependent pathway may play a regulatory role in Toll-receptor system.

Functional role of hyperreactive sulfhydryl moieties within the ryanodine receptor complex

Several laboratories using chemically heterogeneous sulfhydryl modifying agents have shown that sarcoplasmic reticulum (SR) Ca2+ channels known as ryanodine receptors (RyRs) are especially sensitive to modification of functionally important cysteine residues. The functional consequence of sulfhydryl modification of RyRs can include phases of activation and inhibition that are very much dependent on the concentration of the reagent used, the length of exposure, and the nature of the chemical reaction the reagent undertakes with sulfhydryl groups. Most challenging is understanding the relationship for how specific sulfhydryl moieties ascribe specific aspects of RyR function. Considering the structural complexity of the RyR complex with its associated proteins, this task is likely to be a formidable one. A small number of hyperreactive thiols have been shown to exist within the RyR complex. Their functional role does not appear to impact directly on channel gating. Rather hyperreactive cysteine (Cys) moieties may represent biochemical components of a redox sensor that conveys information about localized changes in redox potential produced by physiologic (e.g., glutathione, nitric oxide) and pathophysiologic (quinones, reactive oxygen species) channel modulators to the Ca2+ release process. The molecular and functional details of such a redox sensor remains to be elucidated.

Modification of ryanodine receptor/Ca2+ release channel with dinitrofluorobenzene

Modification of the ryanodine receptor (RyR)/Ca(2+) release channel with 2,4-dinitrofluorobenzene (DNFB) indicated that two classes of amino group interact with the reagent, as can be distinguished on the basis of their reactivity/accessibility and the effects on ryanodine binding and single channel activities. One group interacted very rapidly (t(1/2)<30 s) at 25 degrees C with low concentrations of DNFB [C(50) (concentration of DNFB required for 50% inhibition or stimulation of ryanodine binding)=5 microM], and at pH values of 6.2 and higher. This interaction resulted in the marked stimulation of ryanodine binding and the complete inhibition of a single Ca(2+) release channel incorporated into planar lipid bilayer. The second group is accessible at higher temperatures (37 degrees C); at pH values higher than 7.4 it reacted slowly (t(1/2)=20 min) with high concentrations of DNFB (C(50)=70 microM). This interaction led to the inhibition of ryanodine binding and single channel activity. Modification of RyR with DNFB under the stimulatory conditions resulted in 3.6-fold and 6-fold increases in ryanodine-binding and Ca(2+)-binding affinities respectively. Modification with DNFB under the inhibitory conditions resulted in a decrease in the total ryanodine-binding sites. The exposure of the RyR single channel to DNFB under both inhibitory and stimulatory conditions led to the complete closure of the channel. However, when modified under the stimulatory conditions, but not under the inhibitory ones, the DNFB-modified closed channel could be re-activated by sub-micromolar concentrations of ryanodine, in the presence of nanomolar concentrations of Ca(2+). The DNFB-modified ryanodine-activated RyR channel showed fast transitions between open, closed and several sub-conductance states, and was completely closed by Ruthenium Red. ATP re-activated the DNFB-modified closed channel or, if present during modification, prevented the inhibition of RyR channel activity by DNFB. Neither the stimulation nor the inhibition of ryanodine binding by modification with DNFB was affected by the presence of ATP. By using the photoreactive ATP analogue 3'-O-(4-benzoyl)benzoyl-[alpha-(32)P]ATP we found that DNFB modification had no effect on the ATP-binding site of RyR. The results are discussed with regard to the involvement of amino group residues in channel gating, ryanodine association/dissociation and occlusion, and the relationship between the open/closed state of the RyR and its capacity to bind ryanodine.

Affinity chromatography of human estrogen receptor-alpha expressed in Saccharomyces cerevisiae. Combination of heparin- and 17beta-estradiol-affinity chromatography

Estrogen receptor-alpha is a member of the nuclear hormone receptor superfamily and is considered as a very important regulatory protein. Human estrogen receptor-alpha has been cloned into Saccharomyces cerevisiae as a fusion to ubiquitin and expression is controlled by a metallothionin promotor. Pilot scale quantities of receptor have been produced by a yeast strain transformed with expression plasmid YEpE13 [Graumann et al., J. Steroid Biochem. Mol. Biol. 57 (1996) 293] in a 14 l stirred tank reactor. The yeast extract contained 2-4 pmol of receptor protein per mg total protein. A purification scheme has been developed using heparin-affinity chromatography combined with affinity chromatography with immobilized 17beta-estradiol 17-hemisuccinate. Heparin-affinity chromatography was very efficient to remove host cell protein. Accompanying proteins that stabilize unoccupied receptor have not been dissociated during elution. The receptor could be purified 5-10-fold in ligand-free state. In contrast to previous reports, we did not find a difference of the binding affinity of liganded and unliganded receptor for heparin immobilized onto Sepharose. The unoccupied receptor could be further purified 100-fold with ligand-affinity chromatography using 17beta-estradiol 17-hemisuccinate-bovine serum albumin-Sepharose. The receptor could be kept in its native state, although saturated with 17beta-estradiol. The purification sequence allows an efficient production of receptor. Further improvement of productivity can be only accomplished by increasing the expression level.

[Determination of 14 elements in chromium-rich brewer's yeast by ICP-AES]

An ICP-AES method was established for the determination of 14 elements in chromium-rich and normal brewer's yeast. The RSDs of two standard reference materials were 0. 5%-3.2% and 0.4%-3.4%, respectively. The results showed that chromium contents could affect the concentrations of other elements in chromium-rich brewer's yeast. The concentrations of K, Mn, P, V, Mg and Ca in chromium-rich brewer's yeast were significantly lower than those in normal brewer's yeast.

[The selection of tympanoplastic type in treating chronic suppurative otitis media]

OBJECTIVE

To investigate the effect of different type of tympanoplasty on chronic suppurative otitis media (CSOM).

METHOD

Myringoplasty, focuses clearance and myringoplasty, focuses clearance and ossiculoplasty and myringoplasty were performed in 189 cases of CSOM.

RESULT

The cure rate of perforation of tympanic membrane with myringoplasty was above 99% accompanied by the varying improvement in acoustic sensibility.

CONCLUSION

Different types of tympanoplasty should be used according to the CSOM. The slighter the pathological changes of CSOM, the more the hearing improve. The better effects was in tympanoplasty of simple type. The tympanic exploration is necessary to be included in tympanoplasty.

Site-selective modification of hyperreactive cysteines of ryanodine receptor complex by quinones

Quinones undergo redox cycling and/or arylation reactions with key biomolecules involved with cellular Ca2+ regulation. The present study utilizes nanomolar quantities of the fluorogenic maleimide 7-diethylamino-3-(4'-maleimidylphenyl)-4-methylcoumarin (CPM) to measure the reactivity of hyperreactive sulfhydryl moieties on sarcoplasmic reticulum (SR) membranes in the presence and absence of quinones by analyzing the kinetics of forming CPM-thioether adducts and localization of fluorescence by SDS-polyacrylamide gel electrophoresis. Doxorubicin, 1,4-naphthoquinone (NQ), and 1, 4-benzoquinone (BQ) are found to selectively and dose-dependently interact with a class of hyperreactive sulfhydryl groups localized on ryanodine-sensitive Ca2+ channels [ryanodine receptor (RyR)], and its associated protein, triadin, of skeletal type channels. NQ and BQ are the most potent compounds tested for reducing the rate of CPM labeling of hyperreactive SR thiols (IC50 = 0.3 and 1.8 microM, respectively) localized on RyR and associated protein. The reduced forms of quinone, tert-butylhydroquinone, and 5-imino-daunorubicin do not alter significantly the pattern or kinetics of CPM labeling up to 100 microM, demonstrating that the quinone group is essential for modulating the state of hyperreactive SR thiols. Nanomolar NQ is shown to enhance the association of [3H]ryanodine for its high-affinity binding site and directly enhance channel-open probability in bilayer lipid membrane in a reversible manner. By contrast, micromolar NQ produces a time-dependent biphasic action on channel function, leading to irreversible channel inactivation. These results provide evidence that nanomolar quinone selectively and reversibly alters the redox state of hyperreactive sulfhydryls localized in the RyR/Ca2+ channel complex, resulting in enhanced channel activation. The Ca2+-dependent cytotoxicities observed with reactive quinones formed at the microsomal surface by oxidative metabolism may be related to their ability to selectively modify hyperreactive thiols regulating normal functioning of microsomal Ca2+ release channels.

Effects of dextran on tracheal mucociliary velocity in dogs in vivo

We have previously shown that dextran (molecular weight 4kDa) is a potential mucolytic agent, reducing the viscoelasticity and spinnability of cystic fibrosis (CF) sputum and improving its mucociliary clearability during in vitro testing. We wished to see whether low molecular weight (LMW) dextran had similar effects on mucus rheology when administered by aerosol to living dogs, and whether the administration of dextran increased the rate of mucociliary clearance. Healthy mongrel dogs were anesthetized with pentobarbital and intubated. After a 30-min Ringer aerosol delivery during spontaneous breathing, tracheal mucociliary velocity (TMV by charcoal marker particle transport) was measured under bronchoscopic control, and mucus for viscoelasticity analysis (magnetic rheometer) was collected by the endotracheal tube method. Then LMW dextran in Ringer vehicle was delivered by aerosol via the endotracheal tube, followed by the same procedures. We performed eight experiments in eight dogs, involving 30 min administrations of dextran aerosol; all dogs received inhalations of 20 mg/ml, 65 mg/ml, and 200 mg/ml dextran. Compared with Ringer control, TMV increased to 145% of control (P=0.0417) at 65 mg/ml dextran. Mucus viscoelasticity (G*) significantly decreased to 19% of control (P=0.0426) at 65 mg/ml. This in vivo study supports our previous in vitro testing, that LMW dextran decreases the mucus viscoelasticity and increases the rate of mucociliary clearance. We estimate the dosage received by aerosol at 65 mg/ml to be within the effective concentration range studied in vitro, i.e. 10-15 mg/ml final concentration. The results are consistent with the proposed mechanism that the saccharide moieties in LMW dextran compete for hydrogen bonding sites with other mucous glycoproteins. These new hydrogen bonds are structurally and rheologically ineffective, thus reducing the overall cross-link density, and making the mucus more easily cleared by ciliary and cough mechanisms.

[Ultra trace determination of platinum, palladium, gold and rhodium in minerals]

Our work studied the minerals dissolved in aqua regia. The trace Pt(II), Pd(II) Au (III) and Rh(I) complexes were loaded by the mixed carbon powder which carried diphenyl thiourea when aqua regia or hydrochloric acid media as well as stannous chloride were present. We added some carbon powder in ashen loader and determined the elements with atomic emission spectrometry. The determination sensitivity counted with 10 grams of samples is 1 x 10(-9). The RSD for 0.05 x 10(-6) standard Pt, Pd, Au and Rh solutions are 6.0%, 5.1%, 8.5% and 11.4%, respectively. The method is simple and operation is easy. The results satisfy our requirement.

Antagonistic effects of NES and NLS motifs determine S. cerevisiae Rna1p subcellular distribution

Nucleus/cytosol exchange requires a GTPase, Ran. In yeast Rna1p is the GTPase activating protein for Ran (RanGAP) and Prp20p is the Ran GDP/GTP exchange factor (GEF). RanGAP is primarily cytosolic and GEF is nuclear. Their subcellular distributions led to the prediction that Ran-GTP hydrolysis takes place solely in the cytosol and GDP/GTP exchange solely in the nucleus. Current models propose that the Ran-GTP/Ran-GDP gradient across the nuclear membrane determines the direction of exchange. We provide three lines of evidence that Rna1p enters and leaves the nuclear interior. (1) Rna1p possesses leucine-rich nuclear export sequences (NES) that are able to relocate a passenger karyophilic protein to the cytosol; alterations of consensus residues re-establish nuclear location. (2) Rna1p possesses other sequences that function as a novel nuclear localization sequence able to deliver a passenger cytosolic protein to the nucleus. (3) Endogenous Rna1p location is dependent upon Xpo1p/Crm1p, the yeast exportin for leucine-rich NES-containing proteins. The data support the hypothesis that Rna1p exists on both sides of the nuclear membrane, perhaps regulating the Ran-GTP/Ran-GDP gradient, participating in a complete RanGTPase nuclear cycle or serving a novel function.

Borrelia burgdorferi erpT expression in the arthropod vector and murine host

The expression of a Borrelia burgdorferi gene, erpT, was investigated throughout the spirochaete life cycle in the arthropod vector and the murine host. Three phage clones from a B. burgdorferi DNA expression library synthesized a 30 kDa antigen that was recognized by antibodies in the sera of B. burgdorferi-infected mice but not mice hyperimmunized with B. burgdorferi lysates. Differential antibody binding suggested that this protein was preferentially expressed in vivo. This antigen was designated ErpT, based upon 99.6% homology with the BBF01 sequence in the B. burgdorferi genome. ErpT was not detected on spirochaetes cultured in BSK II medium by indirect immunofluorescence or in B. burgdorferi lysates by immunoblotting, implying that ErpT is not readily produced in vitro. erpT mRNA was not discernible by Northern blot but was identified by RNA polymerase chain reaction in vitro, indicating that erpT is expressed at low levels by cultured spirochaetes. erpT expression was then investigated in the vector and mice because B. burgdorferi do not normally reside in culture medium. RNA polymerase chain reaction and immunofluorescence studies demonstrated that erpT was expressed by a small minority of B. burgdorferi (11/500, 2.2%) within unfed ticks and then repressed during engorgement. erpT mRNA or ErpT antibodies were first detected in B. burgdorferi-infected mice at 4 weeks, suggesting that erpT was not expressed in the early stages of murine infection. Then, during persistent infection, RNA polymerase chain reaction showed that erpT was expressed by B. burgdorferi within the joints, heart and spleen, but not by spirochaetes in the skin. Immunization of mice with ErpT was antigenic but was not protective. These studies demonstrate that B. burgdorferi erpT is differentially expressed throughout the B. burgdorferi life cycle, in both the vector and the mammalian host, and is primarily expressed in extracutaneous sites during murine infection.

[An experimental study of anti-angiogenesis with a cartilage-derived inhibitor]

OBJECTIVE

To evaluate the efficacy of a cartilage-derived inhibitor for the treatment of corneal neovascularization in vivo.

METHODS

A cartilage-derived inhibitor (CDI) from bovine scapula was purified to homogeneity. By rabbit corneal neovascularization (CNV) model, the effect of inhibition of CDI under various conditions was determined in corneal micropocket analysis.

RESULTS

The purified CDI could inhibit strongly the growing speed and area of rabbit CNV compared to control (P < 0.001).

CONCLUSION

It is demonstrated that CDI is a potent dose-dependent inhibitor of angiogenesis.

Comparison of the chromium distribution in organs and subcellular fractions of normal and diabetic rats by using enriched stable isotope Cr-50 tracer technique

The enriched stable isotope 50Cr(III) tracer technique combined with neutron activation analysis was used to examine the intracellular distribution of Cr(III) in the liver, pancreas, testes, and kidney homogenates of both normal and diabetic rats. Our new results showed that the nucleic fraction has the highest Cr concentration in the liver cell of both normal and diabetic rats. The diabetic rats retain more Cr in the mitochondrial and lysosomal fractions of liver homogenate than the normal. This is likely an indication of chromium participating in the glucose or lipid metabolism to compensate the low level of insulin in the body of diabetic rats. The concentrations of Cr in the subcellular fractions of pancreas, testes, and kidney in the normal rats are higher than those in the diabetic rats, which favor the hypothesis that Cr(III) plays its biological function via interaction with the insulin-sensitive tissues or enhancement of the sensitivity of the insulin receptor.

[The changes of pancreatic function after cardiopulmonary bypass]

OBJECTIVE

To evaluate the changes of endocrine and exocrine pancreatic function in patients who underwent heart valve replacement under cardiopulmonary bypass (CPB) in order to optimally conside clinical management perioperatively.

METHOD

Sixteen patients with heart valve disease were selected. Serum glucose, lactate, insulin, C peptide, amylase and lipase were measured.

RESULT

Hyperglycemia and hyperlactacemia were noted after CPB and peaked at 19:00 on the operative day. Their changes were correctly correlated. Serum glucose and lactate returned to the baseline level on the third postoperative day. The average level of serum insulin were normal, but higher on the third postoperative day. However, the level of serum C peptide was higher than the baseline. It doubled the baseline level at 19:00 on the operative day. The average level of serum amylase and lipase was normal, except the higher level of serum lipase on the fourth postoperative day. In our group, 12 patients had normal serum amylase level perioperatively, and 4 increased serum amylase level (25%), among them 2 patients accompanied with hyperlipasimia (16%). There were 8 patients with hyperlipasimia (50%).

CONCLUSION

The endocrine and exocrine pancreatic functions were influenced by CPB and did produce pathophysiologic changes.

The Kaiser Permanente/USC Patient Consultation Study: change in use and cost of health care services

The impacts of three alternative models of pharmacist consultation on the use and cost of health care services were studied. Two studies were conducted concurrently in an HMO over two years. In one, 6000 patients were randomly assigned to one of three consultation models; in the other, the three models were implemented in six geographic regions of California (4600 patients). The models were (1) consultation about new or changed prescriptions as mandated by state law (state model), (2) consultation focused on selected high-risk ambulatory care patients (Kaiser Permanente [KP] model), and (3) a control model. The patients were surveyed three times about their health status and satisfaction, and computerized data on health care use and cost were collected. The effect of the consultation models on the use and cost of health care services was examined across five risk groups that were based on drug-use profiles. An additional 37,750 patients (10% of the patients residing in the areawide study sites) were included in a supplemental analysis of the use and cost of health care services. There was no indication in the random-assignment study that pharmacist consultations affected either drug costs or the cost of office visits. Similar results were found in the areawide study, with the exception that the KP model was associated with lower drug costs than the control model. In the 10% sample, the KP model appeared to be associated with lower office visit costs but higher drug costs. Both models were associated with a lower likelihood of a hospital admission and with lower total health care costs for some high-risk patients compared with the control model. Counseling patients about their medications may be unlikely to reduce medication costs or the cost of office visits but may reduce the likelihood of hospital admissions and the overall costs of health care services; a combination of counseling patients at high risk for drug-related problems and counseling all patients about any new or changed prescription should be considered.

Molecular and structural biology of thyroid hormone receptors

1. Thyroid hormone receptors (TR) are expressed from two separate genes (alpha and beta) and belong to the nuclear receptor superfamily, which also contains receptors for steroids, vitamins and prostaglandins. 2. Unliganded TR are bound to DNA thyroid hormone response elements (TRE) predominantly as homodimers, or as heterodimers with retinoid X-receptors (RXR), and are associated with a complex of proteins containing corepressor proteins. Ligand binding promotes corepressor dissociation and binding of a coactivator. 3. Recent studies from our group have focused on the acquisition and use of X-ray crystallographic structures of ligand-binding domains (LBD) of both the rat (r) TR alpha and the human (h) TR beta bound to several different ligands. We have also developed ligands that bind selectively to the TR beta, which may provide ways to explore the differential functions of TR alpha compared with TR beta isoforms. 4. The LBD is comprised mostly of alpha-helices. The ligand is completely buried in the receptor and forms part of its hydrophobic core. Kinetic studies suggest that the limiting step in formation of high-affinity ligand-receptor complexes is the rate of folding of the receptor around the ligand. Ligands can be fitted tightly in the ligand-binding pocket and small differences in this fitting may explain many structure-activity relationships. Interestingly, analysis of the structures of antagonists suggests that they have chemical groups, 'extensions', that could impair receptor folding around them and, thus, prevent the agonist-induced conformation changes in the receptor. 5. The TR structures allowed us to see that the mutations that occur in the syndrome of generalized resistance to thyroid hormone are located in the vicinity of the ligand-binding pocket. 6. X-ray structure of the TR has also been used to guide construction of mutations in the TR surface that block binding of various proteins important for receptor function. Studies with these TR mutants reveal that the interfaces for homo- and heterodimerization map to similar residues in helix 10 and 11 and also allow the definition of the surface for binding of coactivators, which appears to be general for nuclear receptors. Formation of this surface, which involves packing of helix 12 of the TR into a scaffold formed by helices 3 and 5, appears to be the major change in the receptor structure induced by hormone occupancy.

Mechanisms of thyroid hormone action: insights from X-ray crystallographic and functional studies

This review summarizes the studies conducted in our laboratory on the mechanisms of thyroid hormone action over the past two decades. We have attempted to place our studies on thyroid hormone receptors (TRs) in perspective with the work conducted by other investigators that established their nuclear localization, DNA-binding properties, DNA response elements, and the role of other proteins involved in TR-mediated regulation of gene transcription. Recently, our crystallographic studies of the TR ligand binding domain (LBD) revealed that the ligand has a structural role in the folding of the receptor's hydrophobic core. The analysis of the structure led to biochemical and genetic studies that have defined the surfaces on the TR LBD required for dimerization and binding of coactivator proteins. Placement of the mutations found in patients with the syndrome of generalized resistance to thyroid hormone on the TR LBD revealed that they were restricted to amino acids in the vicinity of the binding pocket for thyroid hormone. The insights gained from the elucidation of the TR LBD structure will provide the basis for the design of compounds with selective agonistic or antagonistic activities.

Voltage-dependent anion channel proteins in synaptosomes of the torpedo electric organ: immunolocalization, purification, and characterization

In this study, we purified and characterized the voltage-dependent anion channel (VDAC) from the Torpedo electric organ. Using immunogold labeling, VDAC was colocalized with the voltage-gated Ca2+ channel in the synaptic plasma membrane. By immunoblot analysis, five protein bands in synaptosomes isolated from the Torpedo electric organ cross reacted with two monoclonal anti-VDAC antibody. No more than about 7 to 10% mitochondrial contains could be detected in any synaptosomal membrane preparation tested. This was estimated by comparing the specific activity in mitochondria and synaptosomes of succinate-cytochrome-c oxidoreductase and antimycin-insensitive NADH-cytochrome-c oxidoreductase activities; mitochondrial inner and outer membrane marker enzymes, respectively. [14C]DCCD (dicyclohexylcarbodiimide), which specifically label mitochondrial VDAC, labeled four 30-35 kDa protein bands that were found to interact with the anti-VDAC antibody. The distribution of the Torpedo VDAC protein bands was different among membranes isolated from various tissues. VDAC was purified from synaptosomes and a separation between two of the proteins was obtained. The two purified proteins were characterized by their single channel activity and partial amino acid sequences. Upon reconstitution into a planar lipid bilayer, the purified VDACs showed voltage-dependent channel activity with properties similar to those of purified mitochondrial VDAC. Amino acid sequence of four peptides, derived from VDAC band II, exhibited high homology to sequences present in human VDACI (98%), VDAC2 (91.8%), and VDAC3 (90%), while another peptide, derived from VDAC band III, showed lower homology to either VDAC1 (88.4%) or VDAC2 (79%). Two more peptides show high homology to the sequence present in mouse brain VDAC3 (100 and 78%). In addition, we demonstrate the translocation of ATP into synaptosomes, which is inhibited by DCCD and by the anion transport inhibitor DIDS. The possible function of VDAC in the synaptic plasma membrane is discussed.

Differential expression of Borrelia burgdorferi genes during erythema migrans and Lyme arthritis

Borrelia burgdorferi, the agent of Lyme disease, selectively expresses genes in the arthropod vector and mammalian host. Specific B. burgdorferi gene expression during human infection was examined in tissue specimens, using RNA-polymerase chain reaction, from 3 patients with Lyme disease. ospA was investigated because OspA is down-regulated by B. burgdorferi in ticks during engorgement and is a vaccine candidate in phase III clinical trials. p35 and p37 were also assessed because these genes are induced by spirochetes during murine Lyme borreliosis and play roles in protective immunity. p35 and p37 mRNA were detected in erythema migrans biopsy specimens from 2 patients and in the synovium of 1 patient with Lyme arthritis. ospA mRNA was not identified in any of these tissues. These data show that ospA is repressed while p35 and p37 are induced in human infection; these results are the first direct demonstration of differential B. burgdorferi gene expression during Lyme disease.

Estrogen receptor activation function 1 works by binding p160 coactivator proteins

Estrogen receptor-alpha contains two transactivation functions, a weak constitutive activation function (AF-1) and a hormone-dependent activation function (AF-2). AF-2 works by recruiting a large coactivator complex, composed of one or more p160s, CREB-binding protein (CBP)/p300, and P/CAF (p300 and CBP-associated factor), via direct contacts with the p160s. We report here that independent AF-1 activity also requires p160 contacts. Unlike AF-2, which binds signature NR boxes in the center of the p160 molecule, AF-1 binds to sequences near the p160 C terminus. We propose that the ability of AF-1 and AF-2 to interact with separate surfaces of the same coactivator is important for the ability of these transactivation functions to synergize.

Serum and urine chromium concentrations in elderly diabetics

The serum and urine chromium concentrations of 57 diabetics and 55 normal fasting subjects were determined by atomic absorption spectrometry (AAS). Our results indicate that the chromium concentration ranges of serum and urine for diabetics are 0.22-0.36 and 4.54-5.90 microg/L, respectively, significantly lower than 0.66-0.84 7.80-9.68 microg/L for the normal (P<0.001), which implies that the elderly diabetics probably lack chromium. Further, it was found that the urine chromium level of the female diabetics was substantially higher than that of the male in the same age group (P<0.01), whereas the serum chromium level was almost the same. However, the urine chromium concentration increases with aging, no matter who the diabetics or the controls are. The serum chromium concentrations of the 24 cases patients with 2-h oral glucose tolerance test (OGTT) were significantly lower than that of those with empty stomach, whereas the urine chromium exhibits a contrary tendency. Our data indicate that the chromium lost and excreted from human body increases with aging and is related to the diabetics. Thus, it is recommended to supplement a certain amount of chromium to the elderly diabetics according to their nutritional level.

Solution NMR structure and backbone dynamics of the major cold-shock protein (CspA) from Escherichia coli: evidence for conformational dynamics in the single-stranded RNA-binding site

The major cold-shock protein (CspA) from Escherichia coli is a single-stranded nucleic acid-binding protein that is produced in response to cold stress. We have previously reported its overall chain fold as determined by NMR spectroscopy [Newkirk, K., Feng, W., Jiang, W., Tejero, R., Emerson, S. D., Inouye, M., and Montelione, G. T. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 5114-5118]. Here we describe the complete analysis of 1H, 13C, and 15N resonance assignments for CspA, together with a refined solution NMR structure based on 699 conformational constraints and an analysis of backbone dynamics based on 15N relaxation rate measurements. An extensive set of triple-resonance NMR experiments for obtaining the backbone and side chain resonance assignments were carried out on uniformly 13C- and 15N-enriched CspA. Using a subset of these triple-resonance experiments, the computer program AUTOASSIGN provided automatic analysis of sequence-specific backbone N, Calpha, C', HN, Halpha, and side chain Cbeta resonance assignments. The remaining 1H, 13C, and 15N resonance assignments for CspA were then obtained by manual analysis of additional NMR spectra. Dihedral angle constraints and stereospecific methylene Hbeta resonance assignments were determined using a new conformational grid search program, HYPER, and used together with longer-range constraints as input for three-dimensional structure calculations. The resulting solution NMR structure of CspA is a well-defined five-stranded beta-barrel with surface-exposed aromatic groups that form a single-stranded nucleic acid-binding site. Backbone dynamics of CspA have also been characterized by 15N T1, T2, and heteronuclear 15N-1H NOE measurements and analyzed using the extended Lipari-Szabo formalism. These dynamic measurements indicate a molecular rotational correlation time taum of 4.88 +/- 0.04 ns and provide evidence for fast time scale (taue < 500 ps) dynamics in surface loops and motions on the microsecond to millisecond time scale within the proposed nucleic acid-binding epitope.

Use of the enriched stable isotope Cr-50 as a tracer to study the metabolism of chromium (III) in normal and diabetic rats

The activable enriched stable isotope Cr-50 compound Cr2O3 was used as a tracer to study the metabolism of chromium(III) [CR(III)] intragastrically administered in normal and diabetic rats. The comparison of absorption, distribution, and excretion in organs and tissues of the two groups do not show much alteration, but some differences exist indeed. The contents of 51Cr radioactivity of the diabetic rats appear to be of higher retention than in most studied organisms. The urinary 51Cr excretion of diabetics is significantly higher than that of normal rats. Therefore, a conclusion can be drawn that the insulin-dependent rats generally absorb and excrete more chromium (Cr) than the normal rats.

Correlation of mercury with selenium in human hair at a typical mercury-polluted area in China

The levels of mercury (Hg) and selenium (Se) and their correlation in human scalp hair of 29 pairs of pregnant women and their newborns living at a high-Hg and low-Se area, the Second Song-Hua-Jiang River System, have been studied by instrumental neutron activation analysis. Our results indicate that the Hg level in infant hair samples are roughly close to that in their mothers, whereas the Se level in infants is much higher. Furthermore, the molar ratios of Se/Hg in newborns are also 40% higher than those in mothers. It demonstrates that infants are able to absorb more selenium from their mothers' bodies to protect against or alleviate the intoxication of Hg. This "autoprotective mechanism" likely plays a critical role during fetal development. The possible chemical species of Hg and Se in hair is also discussed.

Hormone-dependent coactivator binding to a hydrophobic cleft on nuclear receptors

The ligand-binding domain of nuclear receptors contains a transcriptional activation function (AF-2) that mediates hormone-dependent binding of coactivator proteins. Scanning surface mutagenesis on the human thyroid hormone receptor was performed to define the site that binds the coactivators, glucocorticoid receptor-interacting protein 1 (GRIP1) and steroid receptor coactivator 1 (SRC-1). The residues involved encircle a small surface that contains a hydrophobic cleft. Ligand activation of transcription involves formation of this surface by folding the carboxyl-terminal alpha helix against a scaffold of three other helices. These features may represent general ones for nuclear receptors.

Activation of NF-kappaB via a Src-dependent Ras-MAPK-pp90rsk pathway is required for Pseudomonas aeruginosa-induced mucin overproduction in epithelial cells

Cystic fibrosis (CF) is an autosomal recessive disorder, the most common lethal genetic disease in Caucasians. Respiratory disease is the major cause of morbidity and mortality. Indeed, 95% of CF patients die of respiratory failure. Pseudomonas aeruginosa, an opportunistic pathogen, chronically infects the lungs of over 85% of CF patients. It is ineradicable by antibiotics and responsible for airway mucus overproduction that contributes to airway obstruction and death. The molecular mechanisms underlying this pathology are unknown. Here we show that P. aeruginosa activates a c-Src-Ras-MEK1/2-MAPK-pp90rsk signaling pathway that leads to activation of nuclear factor NF-kappaB (p65/p50). Activated NF-kappaB binds to a kappaB site in the 5'-flanking region of the MUC2 gene and activates MUC2 mucin transcription. These studies bring new insight into bacterial-epithelial interactions and more specifically into the molecular pathogenesis of cystic fibrosis. Understanding these signaling and gene regulatory mechanisms opens up new therapeutic targets for cystic fibrosis.

Dicyclohexylcarbodiimide interaction with the voltage-dependent anion channel from sarcoplasmic reticulum

In a recent study [Shoshan-Barmatz, V., Orr, I., Weil, S., Meyer, H., Varsanyi, M. & Heilmeyer, L. M. G. (1996) FEBS Lett. 386, 205-210] we have demonstrated the presence of the voltage-dependent anion channel (VDAC) in skeletal muscle sarcoplasmic reticulum (SR) as supported here by co-localization of VDAC and (Ca2+ + Mg2+)ATPase in the SR using double-immunogold labeling. The interaction of the carboxyl-modifying reagent dicyclohexylcarbodiimide with the SR-VDAC is characterized by labeling with [14C]dicyclohexylcarbodiimide and by dicyclohexylcarbodiimide modification of the reconstituted-purified VDAC channel activity. In both SR and mitochondrial membranes, [14C]dicyclohexylcarbodiimide most specifically labeled a 35-kDa protein, identified as VDAC by specific anti-VDAC Ig. Labeling of the SR-VDAC was about twofold higher than that of the mitochondrial VDAC, which could result either form higher labeling of the SR protein or from relatively higher amounts of VDAC/mg total protein in the SR membranes. [14C]Dicyclohexylcarbodiimide labeling of the SR, but not the mitochondrial VDAC, was biphasic with respect to time and concentration of [14C]dicyclohexylcarbodiimide. Partial digestion of [14C]dicyclohexylcarbodiimide-labeled SR-VDAC with chymotrypsin yielded five proteolytic fragments which were recognized by the anti-VDAC Ig, and the dicyclohexylcarbodiimide-binding site was localized in the 19-kDa fragment. VDAC was purified from SR and mitochondrial membranes by spermine-agarose column. The interaction of dicyclohexylcarbodiimide with functional carboxyl residue(s) in the purified VDAC is demonstrated by recording its channel activity, following its reconstitution into planar lipid bilayer (PLB). Dicyclohexylcarbodiimide inhibited the channel activity in a voltage-dependent manner, requiring incubation with dicyclohexylcarbodiimide at high (negative or positive) potentials. Dicyclohexylcarbodiimide slowed down the transition from the high-conducting to a long-lived low-conducting states of the channel (approximately 20% of its maximal conductance), by stabilizing the intermediate states. Similar results were also obtained with purified-reconstituted mitochondrial VDAC. Hydrophilic carboxyl reagents [[1-ethyl-3-(3-dimethylamino)propyl] carbodiimide, N-ethyl-phenylisoxazolium-3'-sulfonate] neither modified the channel activity nor prevented [14C]dicyclohexylcarbodiimide labeling. These results indicate that dicyclohexylcarbodiimide interacts with a carboxyl group located in a hydrophobic region of the protein which is involved in the channel gating.

[Non-invasive determination of human oxygen metabolism during exercise]

Human muscle oxygenation during exercise was studied with near - infrared spectroscopy (NIRS). Ten athletes performed a 12 min aerobic cycling exercise with increasing workloads. Muscle oxygen content (OC), blood lactate (Bla) and heart rate (HR) were measured continuously throughout the test. The values measured showed a linear correlation (r = -0.962) between Bla and OC during aerobic exercise. The athletes and controls were also selected to compare the variation of OC, Bla and HR under exercise of the same workload. In addition, the muscle oxygen decrease and recovery during sprint were determined and discussed. The results demonstrated that NIRS provides an advantageous method for evaluation of oxygen supply and consumption in working muscles during exercise of varying intensity.

X-ray crystallographic and functional studies of thyroid hormone receptor

We have solved several X-ray crystallographic structures of TR ligand-binding domains (LBDs), including the rat (r) TR alpha and the human (h) TR beta bound to diverse ligands. The TR-LBD folding, comprised mostly of alpha-helices, is likely to be general for the superfamily. The ligand, buried in the receptor, forms part of its hydrophobic core. Tight fitting of ligand into the receptor explains its high affinity for the TR, although the structure suggests that ligands with even higher affinities might be generated. The kinetics of 3,5,3'-triiodo-L-thyronine (T3) and 3,5,3',5'-tetraiodo-L-thyronine (T4) binding suggest that folding around the ligand, rather than receptor opening, is rate-limiting for high affinity binding. TR beta mutations in patients with resistance to T3 cluster around the ligand; these different locations could differentially affect on other receptor functions and explain the syndrome's clinical diversity. Guided by the structure, mutations have been placed on the TR surface to define interactions with other proteins. They suggest that a similar surface in the LBD is utilized for homo- or heterodimerization on direct repeats and inverted palindromes but not on palindromes. Coactivator proteins that mediate TR transcriptional activation bind to a small surface comprised of residues on four helices with a well-defined hydrophobic cleft, which may be a target for pharmaceuticals. The coactivator-binding surface appears to form upon ligand-binding by the folding of helix 12 into the scaffold formed by helices 3, 4 and 5. The analysis of most currently used antagonists suggest that although they probably fit into the ligand-binding pocket, they possess a group that may alter proper folding of the receptor, with disruption of the coactivator-binding surface (the 'extension model').

Improved clearability of cystic fibrosis sputum with dextran treatment in vitro

Most patients with cystic fibrosis (CF) are infected by Pseudomonas aeruginosa. Dextran exhibits anti-adhesive effects in preventing attachment of P. aeruginosa to epithelial cells (1). The initial purpose of this study was to evaluate the potential of dextran to alter the rheology and ciliary transportability of CF sputum prior to initiation of a clinical trial in patients with CF. Sputum samples were collected from 25 patients with CF not receiving rhDNase therapy for use in in vitro testing. Aliquots of CF sputum were treated with 10% vol. Ringer's or the same volume of Dextran 4000 to give a final concentration of 0.4% (4 mg/ml) or 4% (40 mg/ml) dextran in the sputum. Dog mucus samples were collected from seven healthy, anesthetized dogs from the endotracheal tube cuff. Aliquots of dog mucus were subjected to the same concentrations of dextran as the CF sputum. All treated samples were incubated for 30 min at 37 degrees C, and their rheologic properties (viscoelasticity) were evaluated by magnetic microrheometry. For 17 of the sputum samples, frog palate mucociliary transportability was determined from sputum movement on the ciliated, mucus-depleted frog palate, relative to native frog mucus control. Spinnability (cohesiveness) was evaluated by the filancemeter technique for eight sputum samples. Overall, whether for CF sputum or healthy dog mucus, Dextran 4000 treatment significantly reduced viscoelasticity and increased predicted mucociliary and cough clearability. Direct measurements of sputum mucociliary clearability on frog palate increased significantly with 0.4% dextran and 4% dextran compared with saline control. Sputum spinnability (cohesiveness) decreased significantly with both dextran concentrations, too. The effects on viscoelasticity and spinnability were greater at 4% than at 0.4%. There was a significant positive correlation between spinnability and viscoelasticity, and negative relationships between spinnability and both forms of clearability as predicted from viscoelastic measurements. This study suggests that treatment with Dextran 4000 can reduce the crosslink density and cohesiveness of CF and improve mucociliary and cough clearability. Dextran 4000 is an inexpensive and nontoxic agent that may be of benefit in patients with CF lung disease and perhaps in other respiratory disease where mucus retention is an important feature.

Inhibition of airway liquid secretion and its effect on the physical properties of airway mucus

The combination of both Cl- and HCO3- secretion inhibitors causes an accumulation of mucins within the submucosal gland ducts of acetylcholine (ACh)-treated bronchi [S. K. Inglis, M. R. Corboz, A. E. Taylor, and S. T. Ballard. Am. J. Physiol. 272 (Lung Cell. Mol. Physiol. 16): L372-L377, 1997], suggesting indirectly that these agents block airway gland liquid secretion. The present study tested the hypotheses that ACh-stimulated liquid secretion is driven by Cl- and HCO3- secretion and that inhibition of this process leads to secretion of a dehydrated mucus with altered rheological properties. Excised distal bronchi from pigs were pretreated with either a combination of Cl- and HCO3- secretion inhibitors (bumetanide, acetazolamide, dimethylamiloride, and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid) or the dimethyl sulfoxide vehicle and were then treated with ACh to induce secretion. The rate of mucus liquid secretion was substantially reduced when the airways were pretreated with the anion secretion inhibitors. Mucus liquid from inhibitor-pretreated airways contained almost threefold more nonvolatile solids than the control liquid. Rheological analysis revealed that mucus liquid from inhibitor-pretreated airways expressed a significantly greater log G* (rigidity factor), whereas tangent delta (recoil factor) was significantly reduced. These results suggest that 1) ACh-induced liquid secretion in bronchi is driven by both Cl- and HCO3- secretion and 2) inhibition of ACh-induced liquid secretion results in the secretion of mucus with a reduced water content and altered rheological properties.

Identification, characterization and partial purification of a thiol-protease which cleaves specifically the skeletal muscle ryanodine receptor/Ca2+ release channel

A 94 kDa large subunit thiol-protease, as identified by anti-calpain antibodies, has been isolated from skeletal muscle junctional sarcoplasmic reticulum (SR). This protease cleaves specifically the skeletal muscle ryanodine receptor (RyR)/Ca2+ release channel at one site resulting in the 375 kDa and 150 kDa fragments. The 94 kDa thiol-protease degrades neither other SR proteins nor the ryanodine receptor of cardiac nor brain membranes. The partially purified 94 kDa protease, like the SR associated protease, had an optimal pH of about 7.0, was absolutely dependent on the presence of thiol reducing reagents, and was completely inhibited by HgCl2, leupeptin and the specific calpain I inhibitor. However, while the SR membrane-associated protease requires Ca2+ at a submicromolar concentration, the isolated thiol-protease has lost the Ca2+ requirement. The 94 kDa thiol-protease had no effect on ryanodine binding but modified the channel activity of RyR reconstituted into planar lipid bilayer: in a time-dependent manner, the channel activity decreases and within several minutes the channel is converted into a subconducting state. The protease-modified channel activity is still Ca2+-dependent and ryanodine sensitive. This 94 kDa thiol-protease cross react with anti-calpain antibodies thus, may represent the novel large subunit of the skeletal muscle specific calpain p94.

[Antitumor activity of Hypsizigus marmoreus. II. Preventive effect against lung metastasis of Lewis lung carcinoma]

Antitumor activity of Hypsizigus marmoreus, an edible mushroom, was investigated by in vivo bioassay. The aqueous extract, hereinafter referred to as YH, was tested against syngeneic tumor, Lewis lung carcinoma. YH was found to give a significant increase in life span when assayed using a solid tumor, Lewis lung carcinoma, by intraperitoneal administration, but not as much by oral administration. It was also found that YH have an inhibitory activity of spontaneous tumor metastasis in mice bearing Lewis lung carcinoma by intraperitoneal administration. YH significantly decreased the number of metastasized nodules. It was suggested by Winn test that antitumor and antimetasatic activities shown by YH was effective in increasing activity on immunological by competent cells.

Characterization of the long-lasting activator protein-1 complex induced by kainic acid treatment

Kainic acid is known to induce seizures, neuronal damage and cell loss in the rat hippocampus. Our laboratory has shown that a single kainic acid injection elicits acute increases of activator protein-1 DNA-binding activity and this activity stays at an elevated level for 2 weeks after kainic acid injection. However, some pathological changes such as mossy fiber sprouting do not occur until 2-3 weeks after the kainic acid injection and the specific transcription factors regulating the long-term events after kainic acid treatment are not clear. To determine the involvement of activator protein-1 transcription factors in the long-term events after kainic acid treatment, gel mobility-shift and Western blot analyses were used. The results showed that two activator protein-1 complexes with different mobilities occur during the acute stage. However, only the faster-migrating complex as well as the 35-37-kDa fos-related antigen and Jun-D proteins were seen during the late stage. These results suggest that different activator protein-1 complexes exist at different stages after convulsions and that they regulate ensembles of different genes.

Involvement of lysine residues in the gating of the ryanodine receptor/Ca2+-release channel of skeletal muscle sarcoplasmic reticulum

In this study, the modification of skeletal muscle ryanodine receptor (RyR)/Ca2+-release channel with 7-chloro-4-nitrobenzo-2-oxa-1,3,-diazole (Nbd-Cl) demonstrates that lysyl residues are involved in the channel gating. Nbd-Cl was found to have a dual effect: stimulation and inhibition of ryanodine binding and single channel activities. Nbd-Cl, in a time-dependent manner, first stimulated and subsequently inhibited ryanodine binding to both membrane-bound and purified RyR. Incubation of sacroplasmic reticulum membranes with Nbd-Cl for 5-20 s resulted in enhanced ryanodine-binding activity by 2-4-fold due, to an increased binding affinity by about tenfold, with no effect on the total binding sites (Bmax). However, under prolonged incubation (5-20 min), Nbd-Cl strongly inhibited ryanodine binding by decreasing the Bmax with no effect on the binding affinity. Similar effects of stimulation and inhibition by Nbd-Cl were obtained with single channel activity of RyR reconstituted into planar lipid bilayer. Nbd-Cl initially (within a few seconds) activated the channel to a highly open state, then (within a few minutes) inactivated it to the completely closed state. Nbd-Cl-modified protein, as assayed by ryanodine binding or single channel activities, was stable against thiolysis by dithiothreitol, suggesting Nbd-Cl modification of lysyl residues. Evidence from absorption and fluorescence excitation and emission spectra also demonstrated that lysyl residues in RyR were modified by Nbd-Cl. Spectrophotometric data were used to estimate a ratio of up to 1 mol Nbd bound/mol RyR (tetramer) and up to 4 mol Nbd bound per mol RyR (tetramer) for Nbd-Cl stimulated and inhibited RyR activities, respectively. The results clearly indicate the involvement of two classes of lysyl residues in RyR activity. Modification by Nbd-Cl of the fast-reacting group led to stimulation of ryanodine binding and single channel activities, while modification of the slow-reacting group resulted in inhibition of these activities. Thus, the involvement of lysine residues in the gating of the RyR channel is proposed.

Mutations in the conserved C-terminal sequence in thyroid hormone receptor dissociate hormone-dependent activation from interference with AP-1 activity

A short C-terminal sequence that is deleted in the v-ErbA oncoprotein and conserved in members of the nuclear receptor superfamily is required for normal biological function of its normal cellular counterpart, the thyroid hormone receptor alpha (T3R alpha). We carried out an extensive mutational analysis of this region based on the crystal structure of the hormone-bound ligand binding domain of T3R alpha. Mutagenesis of Leu398 or Glu401, which are surface exposed according to the crystal structure, completely blocks or significantly impairs T3-dependent transcriptional activation but does not affect or only partially diminishes interference with AP-1 activity. These are the first mutations that clearly dissociate these activities for T3R alpha. Substitution of Leu400, which is also surface exposed, does not affect interference with AP-1 activity and only partially diminishes T3-dependent transactivation. None of the mutations affect ligand-independent transactivation, consistent with previous findings that this activity is mediated by the N-terminal domain of T3R alpha. The loss of ligand-dependent transactivation for some mutants can largely be reversed in the presence of GRIP1, which acts as a strong ligand-dependent coactivator for wild-type T3R alpha. There is excellent correlation between T3-dependent in vitro association of GRIP1 with T3R alpha mutants and their ability to support T3-dependent transcriptional activation. Therefore, GRIP1, previously found to interact with the glucocorticoid, estrogen, and androgen receptors, may also have a role in T3R alpha-mediated ligand-dependent transcriptional activation. When fused to a heterologous DNA binding domain, that of the yeast transactivator GAL4, the conserved C terminus of T3R alpha functions as a strong ligand-independent activator in both mammalian and yeast cells. However, point mutations within this region have drastically different effects on these activities compared to their effect on the full-length T3R alpha. We conclude that the C-terminal conserved region contains a recognition surface for GRIP1 or a similar coactivator that facilitates its interaction with the basal transcriptional apparatus. While important for ligand-dependent transactivation, this interaction surface is not directly involved in transrepression of AP-1 activity.

[Detection of bcl-2/JH fusion gene in patients with B cell non-Hodgkin's lymphoma by polymerase chain reaction and its clinical implication]

OBJECTIVE

To investigate the frequency and clinical implication of bcl-2/JH gene rearrangement in B cell non-Hodgkin's lymphomas(B-NHLs).

METHODS

Major breakpoint region (MBR) and minor cluster region(mcr) of bcl-2 rearrangement were amplified by polymerase chain reaction in fresh tumor tissue, bone marrow and peripheral blood samples from 23 cases of B-NHL.

RESULTS

Translocation breakpoint was revealed in 10 fresh tumor tissue (71.4% of follicular NHL, 31.3% of diffuse NHL), 8 bone marrow and 7 peripheral blood specimens. The MBR was involved in most of the cases, while the mcr only in one. In addition, of 18 patients with normal bone marrow morphology, 4 were PCR positive, including 2 in early stage ( I and II). Untreated patients with bcl-2 gene rearrangement obtained lower complete remission rate than those without the rearrangement.

CONCLUSION

Detection of bcl-2/JH fusion gene was helpful in diagnosing and staging lymphomas, selecting treatment protocols, and monitoring minimal residual diseases.

Automated analysis of protein NMR assignments using methods from artificial intelligence

An expert system for determining resonance assignments from NMR spectra of proteins is described. Given the amino acid sequence, a two-dimensional 15N-1H heteronuclear correlation spectrum and seven to eight three-dimensional triple-resonance NMR spectra for seven proteins, AUTOASSIGN obtained an average of 98% of sequence-specific spin-system assignments with an error rate of less than 0.5%. Execution times on a Sparc 10 workstation varied from 16 seconds for smaller proteins with simple spectra to one to nine minutes for medium size proteins exhibiting numerous extra spin systems attributed to conformational isomerization. AUTOASSIGN combines symbolic constraint satisfaction methods with a domain-specific knowledge base to exploit the logical structure of the sequential assignment problem, the specific features of the various NMR experiments, and the expected chemical shift frequencies of different amino acids. The current implementation specializes in the analysis of data derived from the most sensitive of the currently available triple-resonance experiments. Potential extensions of the system for analysis of additional types of protein NMR data are also discussed.

Borrelia burgdorferi P35 and P37 proteins, expressed in vivo, elicit protective immunity

p35 and p37 are Borrelia burgdorferi genes encoding 35 and 37 kDa proteins. The gene products were identified by differential screening of a B. burgdorferi expression library with sera from B. burgdorferi infected- and B. burgdorferi-hyperimmunized mice. Northern blot and RT-PCR analyses confirmed that these genes were selectively expressed in vivo. ELISA, using P35 and P37, showed that infected mice (5 of 5, 100%) and patients (31 of 43, 72%) with Lyme borreliosis developed P35 or P37 antibodies. Mice developed peak IgG titers to P35 and P37 within 30 days, followed by decline. Mice given both P35 and P37 antisera were protected from challenge with 10(2) B. burgdorferi, and P35 and P37 antisera also afforded protection when administered 24 hr after spirochete challenge. The use of in vivo-expressed antigens such as P35 and P37 represents a new approach for Lyme disease serodiagnosis and for understanding the role of B. burgdorferi-specific immune responses in host immunity.