Acyl group and electron pair relay system: A network of interacting lipoyl moieties in the pyruvate and α-ketoglutarate dehydrogenase complexes from Escherichia coli

The dihydrolipoyl transacetylase component of the Escherichia coli pyruvate dehydrogenase complex [pyruvate:lipoate oxidoreductase (decarboxylating and acceptor-acetylating), EC 1.2.4.1] bears two sites on each of its 24 polypeptide chains that undergo reductive acetylation by [2-(14)C]pyruvate and thiamin pyrophosphate, acetylation by [1-(14)C]acetyl-CoA in the presence of DPNH, and reaction with N-ethyl[2,3-(14)C]maleimide in the presence of pyruvate and thiamin pyrophosphate. The data strongly imply that these sites are covalently bound lipoyl moieties. The results of similar experiments with the E. coli alpha-ketoglutarate dehydrogenase complex [2-oxoglutarate:lipoate oxidoreductase (decarboxylating and acceptor-succinylating), EC 1.2.4.2] indicate that its dihydrolipoyl transsuccinylase component bears only one lipoyl moiety on each of its 24 chains. Charging of the 48 acetyl acceptor sites on the transacetylase or the 24 succinyl acceptor sites on the transsuccinylase by pyruvate or alpha-ketoglutarate, respectively, and thiamin pyrophosphate was observed in the presence of only a few functionally active pyruvate dehydrogenase or alpha-ketoglutarate dehydrogenase chains. Extensive crosslinking of the transacetylase chains was observed when the pyruvate dehydrogenase complex was treated with pyruvate and thiamin pyrophosphate or with DPNH in the presence of N,N'-o- or N,N'-p-phenylenedimaleimide, respectively. When the alpha-ketoglutarate dehydrogenase complex was treated with DPNH in the presence of N,N'-p-phenylenedimaleimide, only transsuccinylase monomers and crosslinked transsuccinylase dimers were detected. It appears that the 48 lipoyl moieties in the transacetylase and the 24 lipoyl moieties in the transsuccinylase comprise an interacting network that functions as an acyl group and electron pair relay system through thiol-disulfide and acyl-transfer reactions among all of the lipoyl moieties.     

The significance of brain aminopeptidases in the regulation of the actions of angiotensin peptides in the brain

From the outset, the concept of a brain renin-angiotensin system (RAS) has been controversial and this controversy continues to this day. In addition to the unresolved questions as to the means by which, and location(s) where brain Ang II is synthesized, and the uncertainties regarding the functionality of the different subtypes of Ang II receptors in the brain, a new controversy has arisen with respect to the identity of the angiotensin peptide(s) that activate brain AT₁ receptors. While it has been known for some time that Ang III can activate Ang II receptors with equivalent or near-equivalent efficacy to Ang II, it has been proposed that in the brain, only Ang III is active. This proposal, which we have named “The Angiotensin III Hypothesis” states that Ang II must be converted to Ang III in order to activate brain AT₁ receptors. This review examines several aspects of the controversies regarding the brain RAS with a special focus on brain aminopeptidases, studies that either support or refute The Angiotensin III Hypothesis, and the implications of The Angiotensin III Hypothesis for the activity of the brain RAS. It also addresses the need for further research that can test The Angiotensin III Hypothesis and definitively identify the angiotensin peptide(s) that activate brain AT₁ receptor-mediated effects.     

LPL、GPIHBP1、apoA-Ⅴ突变在高脂血症性急性胰腺炎发病中的作用

急性胰腺炎(acute pancreatits,AP)是常见的一种急腹症,死亡率极高,其病因及发病机制尚未完全明确,是目前研究的热点.其中,高脂血症(hyperlipidemia,HL)与AP关系的研究越来越受到重视,而基因突变尤其是脂蛋白脂肪酶(lipoprotein lipase,LPL)、甘油磷酸肌醇锚定高密度脂蛋白结合蛋白1(glycosylphosphatidylinositol high density lipoprotein-binding protein1,GPIHBP1)及载脂蛋白A-Ⅴ(apolipo-proteinA-Ⅴ,apoA-Ⅴ)的基因突变对HL特别是高乳糜微粒血症及随之发生的复发性胰腺炎的影响最为显著.本文就这3个蛋白的相关基因突变在高脂血症性胰腺炎发病中的作用研究进展作一综述.     

The epidemiological risk factors of the larynx cancer among the native and migrant male population

In the present paper relative risk of larynx cancer has been evaluated in 272 cases in the stationary (native Upper Silesians) (65.4%) and migrant (34.6%) population of men. The corresponding control groups (total 739 men) consisted of 401 (54.3%) and 338 (45.7%) men, respectively, who did not suffer from neoplastic diseases. The important relationship between larynx cancer incidence and cigarette (with or without filter), pipe and cigar smoking has been proved. It has also been shown that the evaluation of larynx cancer risk according to the birth place of populations is more useful, because it enables to discover new epidemiological aspects of the larynx cancer. The higher larynx cancer risk has also been disclosed in men who are in manual work, and who are immediately exposed to the influence of various dusts and gases in their place of work. It has been discovered, that chronic inflammation of the upper respiratory tract, pneumonia, tuberculosis, emphysema or bronchitis also influence higher larynx cancer incidence risk in the native and migrant populations analysed.     

Stereological analysis of the effects of 6-hydroxydopamine on the ultrastructure of the melanocyte-stimulating hormone cell of the pars intermedia of the pituitary of Xenopus laevis.

It has been confirmed that intracisternal administration of the sympatholytic compound 6-hydroxydopamine (6-OHDA) to the toad Xenopus brings about degenerative changes in the appearance of the catecholaminergic innervation of the pars intermedia of the pituitary. This observation has been extended by stereological analysis of the ultrastructural composition of the presumed melanocyte-stimulating hormone (MSH) cells of the pars intermedia, which reveals that following the administration of this compound there is an increase in the amount of rough endoplasmic reticulum and a decrease in the numbers of secretory granules. These changes are consistent with increased secretory activity and are considered to reflect the removal of an inhibitory catecholaminergic influence from the MSH cells. 6-OHDA also brings about a prolonged darkening of the animals, but it is suggested that this cannot be due entirely to increased circulating levels of MSH in view of the finding that 6-OHDA has a pituitary-independent effect on pigmentation, as demonstrated by the administration of 6-OHDA to hypophysectomised animals when a transitory darkening occurs.     

Computed tomography in the diagnosis of asbestos-related thoracic disease

High-resolution computed tomography (HRCT) has improved the radiologist's ability to detect and potentially quantify the abnormalities of asbestos exposure. It has proved to be more sensitive than chest radiography for detecting pleural plaques and for discriminating between pleural fibrosis and extrapleural fat. HRCT is also more sensitive than chest radiography or conventional CT for detecting parenchymal abnormalities in asbestos-exposed persons. The HRCT findings that correlate with other parameters of asbestosis include (1) septal and centrilobular thickening, (2) parenchymal fibrous bands, (3) honeycomb patterns, (4) subpleural density persisting in the prone position, and (5) subpleural curvilinear lines that persist in the prone position. CT has an important role in evaluating benign and malignant lung and pleural masses in asbestosis.     

Similarities Between the Conformation of Arsanilazotyrosine 248 of Carboxypeptidase Aα in the Crystalline State and in Solution

Modification of carboxypeptidase A(gamma) crystals (Anson) with diazotized arsanilic acid specifically labels tyrosine 248; at pH 8.2 the modified enzyme gives yellow crystals, but a red solution. It has been suggested that arsanilazotyrosine 248 forms a complex with the Zn cofactor accounting for the red color in solution, but that a complex is not formed in the crystal. However, the crystal structure of carboxypeptidase A(gamma) is unknown. We show here that crystals of carboxypeptidase A(alpha), whose crystal structure has been determined, are red both in solution and in the crystalline state (at pH 8.2) after modification with diazotized arsanilic acid. These new data are of importance in relating the structure in the crystalline state to the catalytic mechanisms, as based on the x-ray diffraction evidence.The activity of carboxypeptidase A in the crystal and in solution has a ratio of only 1/3 for the alpha form, in contrast to the ratio of 1/300 for the gamma form, with carbobenzoxyglycyl-L-phenylalanine as a substrate.A pH-jump experiment monitored by stopped-flow kinetics in a split-beam apparatus has revealed a single exponential rate when a solution of arsanilazotyrosine 248 carboxypeptidase A(alpha) at pH 6.7 (yellow) is increased to pH 8.5 (red). The rate constants obtained in this experiment are 6.1 sec(-1) at 3.0 mg/ml and 7.2 sec(-1) at 1.6 mg/ml concentration of enzyme.     

Basic requirements for a metal-binding site in a protein: the influence of loop shortening on the cupredoxin azurin

The main active-site loop of the copper-binding protein azurin (a cupredoxin) has been shortened from C(112)TFPGH(117)SALM(121) to C(112)TPH(115)PFM(118) (the native loop from the cupredoxin amicyanin) and also to C(112)TPH(115)PM(117). The Cu(II) site structure is almost unaffected by shortening, as is that of the Cu(I) center at alkaline pH in the variant with the C(112)TPH(115)PM(117) loop sequence. Subtle spectroscopic differences due to alterations in the spin density distribution at the Cu(II) site can be attributed mainly to changes in the hydrogen-bonding pattern. Electron transfer is almost unaffected by the introduction of the C(112)TPH(115)PFM(118) loop, but removal of the Phe residue has a sizable effect on reactivity, probably because of diminished homodimer formation. At mildly acidic pH values, the His-115 ligand protonates and dissociates from the cuprous ion, an effect that has a dramatic influence on the reactivity of cupredoxins. These studies demonstrate that the amicyanin loop adopts a conformation identical to that found in the native protein when introduced into azurin, that a shorter than naturally occurring C-terminal active-site loop can support a functional T1 copper site, that CTPHPM is the minimal loop length required for binding this ubiquitous electron transfer center, and that the length and sequence of a metal-binding loop regulates a range of structural and functional features of the active site of a metalloprotein.     

Detection and Isolation of the Repressor Protein for the Tryptophan Operon of Escherichia coli

DNA from a transducing bacteriophage carrying a fusion of the tryptophan and lactose operons of E. coli (lambdadtrp-lac) has been used to direct cell-free synthesis of beta-galactosidase (EC 3.2.1.23). Whereas normal lac operon (lambdadlac) DNA requires adenosine-3':5'-cyclic monophosphate (cAMP) for beta-galactosidase synthesis, trp-lac DNA is unaffected by cAMP. This difference in cAMP dependence verifies the presence of a cAMP-requiring promoter in the lac operon that has been removed from the trp-lac DNA. Synthesis with trp-lac DNA is controlled by the protein product of the tryptophan repressor gene (trpR). Synthesis in extracts of trpR(-) (repressor-negative) cells is progressively reduced by increased additions of extract from trpR(+) cells. No trpR(-) product repression is seen when beta-galactosidase synthesis is programmed by normal lac DNA. This highly sensitive and specific assay has facilitated quantitation and partial purification of the trp repressor.     

Nature of the charged-group effect on the stability of the C-peptide helix.

The residues responsible for the pH-dependent stability of the helix formed by the isolated C-peptide (residues 1-13 of ribonuclease A) have been identified by chemical synthesis of analogues and measurement of their helix-forming properties. Each of the residues ionizing between pH 2 and pH 8 has been replaced separately by an uncharged residue. Protonation of Glu-2- is responsible for the sharp decrease in helix stability between pH 5 and pH 2, and deprotonation of His-12+ causes a similar decrease between pH 5 and pH 8. Glu-9- is not needed for helix stability. The results cannot be explained by the Zimm-Bragg model and host-guest data for alpha-helix formation, which predict that the stability of the C-peptide helix should increase when Glu-2- is protonated or when His-12+ is deprotonated. Moreover, histidine+ is a strong helix-breaker in host-guest studies. In proteins, acidic and basic residues tend to occur at opposite ends of alpha-helices: acidic residues occur preferentially near the NH2-terminal end and basic residues near the COOH-terminal end. A possible explanation, based on a helix dipole model, has been given [Blagdon, D. E. & Goodman, M. (1975) Biopolymers 14, 241-245]. Our results are consistent with the helix dipole model and they support the suggestion that the distribution of charged residues in protein helices reflects the helix-stabilizing propensity of those residues. Because Glu-9 is not needed for helix stability, a possible Glu-9-...His-12+ salt bridge does not contribute significantly to helix stability. The role of a possible Glu-2-...Arg-10+ salt bridge has not yet been evaluated. A charged-group effect on alpha-helix stability in water has also been observed in a different peptide system [Ihara, S., Ooi, T. & Takahashi, S. (1982) Biopolymers 21, 131-145]: block copolymers containing (Ala)20 and (Glu)20 show partial helix formation at low temperatures, pH 7.5, where the glutamic acid residues are ionized. (Glu)20(Ala)20Phe forms a helix that is markedly more stable than (Ala)20(Glu)20Phe. The results are consistent with a helix dipole model.     

Epidemiology of human T-lymphotropic virus type III and the risk of the acquired immunodeficiency syndrome

The discovery of human T-lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV) has opened a window to the understanding of the spectrum of the acquired immunodeficiency syndrome (AIDS) and related clinical syndromes. Analysis of risk factors for seropositivity has shown that HTLV-III is transmitted most efficiently via routes that involve close personal contact or parenteral exposure. Longitudinal studies have shown that HTLV-III infection has a long latent period. The prevalence of AIDS in different geographic areas and among different risk groups appears to depend in part on duration of exposure. Co-factors for AIDS outcome such as manner and route of exposure, underlying immune status, and host susceptibility are also likely to play a role in risk.     

Factors influencing the auricular murmur and the intensity of the first heart sound

Studies of cases of mitral stenosis in which there were varying degrees of heart block have clearly demonstrated that the presystolic murmur of mitral stenosis is produced by contraction of the auricle.^{1, 2, 3} More recently it has been appreciated that presystolic gallop rhythm and certain split heart sounds also result from sound waves initiated by auricular contraction.^{4, 5} The relation of the auricular contraction to the intensity of the first heart sound has been investigated by many observers.^{6, 7, 8} There has been no unanimity of opinion, however, as to the mechanism by which the auricular contraction modifies the intensity of the first sound. This study is reported for the purpose of emphasizing: (1) the effect of the degree of ventricular filling on the intensity of the sound produced by the auricular contraction; (2) the relative effect on the intensity of the first heart sound of (a) the time of auricular contraction and (b) the degree of ventricular filling.     

Therapeutic Plasma Exchange for the Treatment of Rapidly Progressive Glomerulonephritis

Abstract: Therapeutic plasma exchange (TPE) has been widely accepted as a successful means of removing the antiglomerular basement membrane (anti-GBM) antibodies that result in the rapidly progressive glomerulonephritis (RPGN) of Goodpasture's syndrome. TPE has also been investigated as a means of removing the immune complexes associated with the glomerulonephritides of systemic lupus erythematosus, IgA nephropathy, Henoch Schönlein purpura, and cryoglobulinemia. Recently, an antineutrophil cytoplasmic antibody (ANCA) has been implicated in the pathogenesis of RPGN associated with such diseases such as Wegener's granulomatosis and periarteritis nodosa. ANCA has also been found in many cases of RPGN formally considered to be idiopathic. The identification of this autoantibody has given new credence to the possibility that TPE may be beneficial in the treatment of these diseases. This article reviews the data regarding the use of TPE for RPGN.     

Glucose-insulin-potassium therapy in the era of coronary revascularization

Glucose-insulin-potassium (GIK) utilization in the treatment of acute myocardial infarction (AMI) has been studied since the early 1960s with varying results. It is well established that ischemic myocardial cells convert from aerobic metabolism of glucose to toxic anaerobic free fatty acid (FFA) metabolism for the production of energy. It has been hypothesized that administration of GIK during coronary revascularization would decrease the degree of myocardial damage. Earlier clinical trials, before the revascularization era, demonstrated a potential role for GIK therapy to reduce the mortality and morbidity associated with AMI. In recent years, GIK therapy has been incorporated into current revascularization methods without clear evidence as to its efficacy. Based on the most current studies, it has been determined that GIK therapy is not beneficial in patients with AMI, regardless of revascularization status, and therefore should not be used.     

Association study of the functional variants of the GLIS3 gene with risk of knee osteoarthritis

Clinical Rheumatology - Osteoarthritis (OA) ranks the most common joint disorder and the leading cause of disability. Growing evidence has revealed that OA has a strong genetic background, except...     

A Critique of the Concept of the Alcohol Dependence Syndrome

The term ‘alcoholism’ has been dropped from the International Classification of Diseases and replaced by the concept of the ‘alcohol dependence syndrome’. Four justifications for the syndrome idea are examined. It has been claimed that (1) the syndrome's existence was supported by scientific evidence, but only psychobiological alterations were truly supported by evidence; (2) dependence was not considered as all or none, but other statements contradicted this; (3) the syndrome idea had clinical usefulness, but it can be argued that the concept would be superfluous within a thorough assessment, and would likely confuse rather than enlighten a patient; (4) the syndrome concept synthesised research findings which contradicted the alcoholism concept, but this might inhibit further research by concentrating on ‘impaired control’ and neglecting the process of the development of drinking problems. Since both the validity and the utility of the concept of the alcohol dependence syndrome are questionable, it is suggested that the WHO's formal support for it was partly a political decision, and that the assertion that dependence is an illness might be an attempt to rejuslify the role of medical expertise in this area.     

Deubiquitinating function of ataxin-3: insights from the solution structure of the Josephin domain

Spinocerebellar ataxia type 3 is a human neurodegenerative disease resulting from polyglutamine tract expansion. The affected protein, ataxin-3, which contains an N-terminal Josephin domain followed by tandem ubiquitin (Ub)-interacting motifs (UIMs) and a polyglutamine stretch, has been implicated in the function of the Ub proteasome system. NMR-based structural analysis has now revealed that the Josephin domain binds Ub and has a papain-like fold that is reminiscent of that of other deubiquitinases, despite primary sequence divergence but consistent with its deubiqutinating activity. Mutation of the catalytic Cys enhances the stability of a complex between ataxin-3 and polyubiquitinated proteins. This effect depends on the integrity of the UIM region, suggesting that the UIMs are bound to the substrate polyubiquitin during catalysis. We propose that ataxin-3 functions as a polyubiquitin chain-editing enzyme.     

Genetic ablation of angiotensinogen in the subfornical organ of the brain prevents the central angiotensinergic pressor response

The subfornical organ (SFO) of the brain has long been considered a critical integrating center for the cardiovascular actions of the renin-angiotensin system (RAS). Early reports of angiotensin II (Ang II) immunoreactivity in the SFO and its neural projections to downstream cardiovascular nuclei raised the possibility that Ang II is produced locally and functions as a putative neurotransmitter in these circuits. However, evidence of functionally significant de novo synthesis of Ang II in the SFO has been lacking. Here, implementing spatiotemporally restricted gene ablation by way of the Cre recombinase/loxP system, we provide the first direct evidence that the local RAS in the SFO has a critical role in blood pressure regulation. Using a transgenic mouse harboring an angiotensinogen (AGT) gene modified for Cre-mediated deletion (hAGT(flox)), in combination with gene transfer of an adenovirus encoding Cre targeted to the SFO, we show that deletion of the Ang II substrate in this brain region nearly abolishes the pressor and bradycardic effects of renin infused in the CNS. Immunohistochemical analyses verified intense and restricted expression of Cre in the SFO, which paralleled the decrease in AGT expression selectively in this site. Further physiological studies confirmed the integrity of central angiotensinergic and nonangiotensinergic cardiovascular response systems in the Cre-treated mice. In addition to establishing that AGT expression in the SFO and its local conversion to Ang II has a profound effect on blood pressure, this study provides proof-of-principle of the utility of this approach for dissecting the brain RAS and other complex systems in CNS cardiovascular circuits.     

Application of the MAIEA Assay to the Kell Blood Group System

The monoclonal antibody-specific immobilisation of erythrocyte antigens (MAIEA) test has been employed to investigate the Kell system using five monoclonal antibodies which recognise high frequency epitopes on the 93,000-molecular weight Kell glycoprotein: BRIC 18, BRIC 68, BRIC 107, BRIC 203 and 6–22. BRIC 107, which has anti-k-like (KEL2) specificity, identifies a distinct epitope, whilst competitive binding assays suggested that BRIC 203 (anti-Kp^bc), BRIC 18, BRIC 68 and 6–22 (anti K14) comprise an overlapping set of epitopes. The MAIEA assay has been very successful in confirming the assignment of most of the Kell and para-Kell antigens to the Kell protein. Due to the competitive nature of the assay and the fact that the monoclonal antibodies bind to different regions, the results also suggest the relative positions of some of the Kell antigens on the Kell protein; these appear to be located in at least five spatially distinct regions.