Human obesity: from lipid abnormalities to lipid oxidation

The obese state has been recognized to accentuate the known risk factors for atherosclerotic disease as dyslipidemia, hypertension, glucose intolerance and insulin resistance. Among other risk factors, obesity is characterized by a series of lipid disturbances, such as hypercholesterolemia, high fasting (and postprandial) triglyceride levels, low HDL cholesterol, high apolipoprotein B, high small dense lipoprotein particles and alterations of serum and tissue LPL-activity. Although obesity is associated with such cluster of lipid abnormalities, these factors do not explain the complete process of atherogenesis in the obese subject. Other risk factors belonging to the polymetabolic syndrome-cluster, insulin resistance, hypertension, fibrinogen, add substantial but not full explanation to the atherothrombotic process. Over the last decade, a series of excellent studies have provided the background for a more indepth mechanism of atherosclerosis; the role of lipid peroxidation in particular has been one of the focuses of this current research. There exists a lot of evidence suggesting a major role for oxidized LDL and VLDL particles in the pathogenesis of atherosclerosis. Although obesity is characterized by dyslipidemia, less is known about the oxidation capacity of lipoproteins in obese subjects. We measured the oxidizability in vitro in 21 premenopausal women and compared them to 18 age-matched controls. The oxidizability of the non-HDL fraction is evaluated by measuring the fluorescence and thiobarbituric acid reactive substances (TBARS: MDA nM/mg non-HDL) at different time intervals of incubation. TBARS formation increased linearly with the increase of lipids both in non-obese and obese subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohols induce rapid depletion of intracellular free Mg2+ in cerebral vascular muscle cells: relation to chain length and partition coefficient

Acute effects of a series of alcohols (methanol, ethanol, n-butanol) on intracellular free magnesium concentration ([Mg2+]i) in canine cerebral vascular smooth muscle cells was studied using mag-fura-2 and digital imaging microscopy. In 1.2 mM [Mg2+]o, basal [Mg2+]i was 500 +/- 30 microM. Exposure of cells to a low concentration (25 mM) of ethanol, but not methanol, for only 30 s resulted in significant loss of [Mg2+]i. Exposure to 100 mM methanol, ethanol, and butanol for 30 s resulted in a relative order of potency for [Mg2+]i depletion, where butanol >> ethanol > methanol. The heterogeneous and relative subcellular compartmented concentrations of [Mg2+]i, where perinuclear > nuclear >> peripheral (cytosolic) region, was not significantly altered by the alcohols. The degree of cellular depletion of [Mg2+]i was directly a function of each alcohol's partition coefficient and chain length. The latter is suggestive of the probability that alcohols promote intracellular depletion of Mg2+ by partitioning in membranes and disordering lipid bilayers.

Determination of manganese in Chinese tea leaves by a catalytic kinetic spectrophotometric method

The catalytic effect of manganese(II) on the oxidation of Rhodamine B with potassium periodate in the presence of 1,10-phenanthroline in acetic acid-sodium acetate was studied. A catalytic kinetic spectrophotometric method for determination of manganese(II) was developed. Manganese in the range 0.1-5.0 ng ml-1 can be determined, and the detection limit is 0.02 ng ml-1. Manganese in Chinese tea leaves was successfully determined.

Chimeras from a human rhinovirus 14-human immunodeficiency virus type 1 (HIV-1) V3 loop seroprevalence library induce neutralizing responses against HIV-1

A chimeric virus library was designed whereby sequences corresponding to the V3 loop of human immunodeficiency virus type 1 (HIV-1) were presented on the surface of human rhinovirus 14. The V3 loop sequences consisted of a relatively conserved segment of seven amino acids and five adjacent residues that were allowed to vary in proportion to their seroprevalence among HIV-1 isolates of North America and Europe. A technique called random systematic mutagenesis was used to incorporate the composite V3 loop sequences flanked by zero to two randomized amino acids. This library could contain 2.7 x 10(8) members having diverse sequences and conformations. Immunoselection of a portion of this library by using two neutralizing V3 loop-directed monoclonal antibodies followed by selection for desirable growth and purification characteristics yielded a set of chimeric rhinoviruses, five of which are described. The inserted sequences in the five chimeras do not match those of any known isolate of HIV-1. Nonetheless, all five chimeras were neutralized by antibodies directed against different strains of HIV-1 and were able to elicit the production of antibodies that bind V3 loop peptides from diverse HIV-1 isolates. Moreover, antisera derived from four of the five chimeras were capable of neutralizing one or more strains of HIV-1 in cell culture. This study demonstrates that random systematic mutagenesis in conjunction with antibody screening is a powerful and efficient means to obtain antigenic chimeras with relevant immunogenic properties.

[Characterization and quantification of dermatan sulfate from donkey skin]

Dermatan sulfate (DS), a recently known antithrombotic glycosaminoglycan, was isolated and purified from donkey skin. Physiochemical characteristics of the glycan, including constituent analysis, electrophoretic behaviour, molecular mass, specific lyase degradations, IR and PMR spectra were described, using porcine skin-origin dermatan sulfate as a standard reference. Contents of DS in donkey skin and its gelatinized preparations (Ejiao) were also measured. Results indicate that the presence of DS may explain the long reputed clinical efficacy of donkey skin and Ejiao in treating serious symptoms associated with what has been called endogenous wind in traditional Chinese medicine.

RH-3421, a potent dihydropyrazole insecticide, inhibits depolarization-stimulated rises in free [Ca2+] and 45Ca2+ uptake in mammalian synaptosomes

The dihydropyrazole RH-3421 inhibits veratridine- and K(+)-induced rises in synaptosomal free Ca2+ with IC50s of 0.2 and 1 microM, respectively. The K(+)-induced rise in free synaptosomal Ca2+, which requires external Ca2+, is also blocked by RH-3421 in the presence of tetrodotoxin. The K(+)-stimulated 45Ca2+ uptake by synaptosomes is unaffected by tetrodotoxin, blocked by cobalt ions and inhibited by RH-3421 both alone (IC50 = 11 microM) and in the presence of tetrodotoxin. RH-3421 does not influence the level of free Ca2+ or basal 45Ca2+ uptake in non-depolarized synaptosomes. The results suggest RH-3421 inhibits voltage-sensitive calcium channels in nerve endings.

A rapid and simple method for measuring the susceptibility of low-density-lipoprotein and very-low-density-lipoprotein to copper-catalyzed oxidation

Much evidence has accumulated to suggest a role for the oxidation of low-density-lipoprotein (LDL) and very low-density-lipoprotein (VLDL) in the pathogenesis of atherosclerosis. The susceptibility of lipoprotein to copper-catalyzed oxidation is often used to evaluate its oxidizability. A method was developed which isolates the non-high-density lipoprotein (non-HDL) fraction and removes EDTA by a dextran-magnesium precipitation method. The oxidizability of this fraction is evaluated by monitoring the fluorescence and measuring thiobarbituric acid reactive substances (TBARS) at different intervals of incubation. Those parameters reflect apolipoprotein B (apo B) modification and lipid degradation during LDL and VLDL oxidation. Our assay is sensitive enough to study factors which can influence the oxidizability of LDL and VLDL. The method is simple, rapid and can be easily conducted in a routine laboratory.

Cocaine-induced cerebrovasospasm and its possible mechanism of action

Experiments were designed to study the effects and mechanism of action of cocaine (COC) on cerebrovascular tissues. Acute exposure to COC (10(-9) to 5 x 10(-3) M) induced contractile responses in isolated canine basilar (BA) and middle cerebral arteries in a dose-dependent manner, but not in mesenteric arteries. The presence or absence of intact endothelium did not alter COC concentration-response curves. The sensitivity to COC was higher in BA (ED50 = 7.20 +/- 0.16 x 10(-5) M) than middle cerebral arteries (ED50 = 1.25 +/- 0.12 x 10(-4) M). Similar effects of COC were also noted in BA from piglets (ED50 = 0.99 +/- 0.25 x 10(-4) M) and sheep (ED50 = 1.34 +/- 0.31 x 10(-4) M). A variety of amine antagonists, an opiate antagonist and an N-MDA receptor antagonist failed to interfere with the COC-induced contractions. However, haloperidol, indomethacin, verapamil and excess [Mg++]0 (4.8 x 10(-3) M) as well as removal of [Ca++]0 completely prevented vasospasms induced by COC. Dopamine and COC resulted in very similar concentration-response curves on canine BA. COC stimulation failed to affect vascular release of thromboxane B2, prostaglandins or 6-Keto-prostaglandin F1 alpha. Interestingly, 10(-7) M COC rapidly elevated intracellular free Ca++ concentrations of cultured cerebral vascular muscle cells about 50% over initial resting levels. The data suggest that COC produces cerebrovasospasm, probably by a direct action on cerebral blood vessels via promoting Ca++ influx and/or intracellular Ca++ release in cerebral vascular muscle cells, which may be modulated by Mg++.

Design and construction of rhinovirus chimeras incorporating immunogens from polio, influenza, and human immunodeficiency viruses

This paper describes the design and construction of chimeric human rhinoviruses that contain immunogenic regions from other pathogens as part of their surface coat proteins. Segments encoding the poliovirus 3 Sabin VP1 and VP2 proteins, the influenza hemagglutinin (HA) glycoprotein, and the human immunodeficiency virus gp120 surface and gp41 transmembrane glycoproteins were inserted into a full-length clone of human rhinovirus 14 (HRV14) at regions corresponding to neutralizing immunogenic sites IA (NIm-IA) and II (NIm-II). Of 12 chimeric constructs described, 3 produced viable virus. An HRV14 chimeric virus containing five amino acids of influenza HA (corresponding to 300 A2 of solvent-accessible surface area) had wild-type HRV14 growth characteristics and was neutralized by four of four anti-influenza HA antisera with reciprocal neutralizing titers ranging from 180 to 330. However, antisera raised in two guinea pigs against the HRV14:influenza HA chimera did not show significant neutralization of relevant strains of influenza. These results are the first to demonstrate the feasibility of making viable chimeras of human rhinoviruses displaying heterologous immunogens.

Use of random systematic mutagenesis to generate viable human rhinovirus 14 chimeras displaying human immunodeficiency virus type 1 V3 loop sequences

Random systematic mutagenesis was used to generate a library of human rhinovirus 14 chimeras that each display a segment from the V3 loop of human immunodeficiency virus type 1. The sequence XXIGPGRAXX, where X could be any of the 20 amino acids, was inserted at the neutralizing immunogenic site II of human rhinovirus 14 between VP2 residues 159 and 160. Twenty-five unique chimeric viruses were isolated, and the identity of their randomized residues was determined. A nonrandom amino acid distribution that may reflect structural requirements for viability was observed at the randomized positions. Fifteen of 25 chimeras were neutralized by one or more of a panel of four anti-human immunodeficiency virus type 1 V3 loop antibody preparations, indicating that antigenicity had been successfully transplanted. Libraries of chimeric viruses produced by using the techniques described may be a source of vaccines and other immunotherapeutic reagents. The random systematic mutagenesis methodology described should be generally useful for the rapid transplantation of foreign sequences into viral coat and other proteins to produce libraries containing members with the desired properties.

Role of excitatory amino acids in regulation of rat pial microvasculature

Recently, attention has been drawn to the possibility that excitatory amino acids (EAAs) may play an important role in the pathogenesis of hypoxic-ischemic neuronal injury. Exaggerated release of EAAs and excessive stimulation of N-methyl-D-aspartate (NMDA) receptors and other EAA receptors have been suggested to contribute to neuronal death in ischemia and anoxia. A number of in vitro and in vivo experimental studies have shown that EAA-receptor antagonists exert a protective effect on the brain after cerebral ischemia. Because neurons are in close apposition to small intracerebral vessels, synaptically released EAAs might also regulate small blood vessel function. With the use of quantitative television microscopic observations, in vivo studies were undertaken on pial arterioles of rats. Perivascular administration of cumulative doses (10(-7)-10(-2) M) of L-glycine, L-glutamate, L-aspartate, and NMDA on the pial microvessels resulted in concentration-dependent constriction of pial arterioles (5-30% decreases in diameter) and cerebrovasospasm; the relative order of potency was aspartate > NMDA > glycine > glutamate. High concentrations of EAAs often resulted in rupture of postcapillary venules. No amine or opiate antagonist or cyclooxygenase inhibitor prevented or attenuated the effects of these putative EAAs. EAA-induced constriction and spasm of pial arterioles as well as rupture of venules could, however, be blocked by the noncompetitive NMDA-receptor antagonist MK-801 and by Mg2+. MK-801 also produced a concentration-dependent relaxation on normal pial arterioles. These results are compatible with the idea that a specific NMDA-receptor complex (RC) exists in rat cortical microvessels, which subserves vasoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)

A rare 6q11+ heteromorphism: cytogenetic analysis and in situ hybridization

A rare variant of 6q11+ heteromorphism was found in a fetus and the mother during amniocentesis. The G- and Q-banding and DA/DAPI stain were negative. The C-banding was positive and the C-banded segment was 3-fold longer in the variant than in its homologue. Neither of the C-banded regions of chromosomes 6 decondensed when exposed to distamycin A or 5-azacytidine. A DNA replication study indicated that the C-banded variant was late replicating. The lateral asymmetry observed in the 6q11 variant after one replication cycle in 5-bromodeoxyuridine may result from an unequal interstrand distribution of thymidine in the repetitive DNA. Fluorescent in situ hybridization using a chromosome-6-specific alpha-satellite probe (D6Z1) demonstrated hybridization signals on the centromere of chromosome 6. The 6q11 variant showed a signal which was 3-fold larger than its homologue. These results indicate that the 6q11 variant is an amplification of a chromosome-6-specific alpha repeat, and the size of the hybridization signal correlates with the size of the laterally asymmetric and C-banded region.

Ethanol promotes rapid depletion of intracellular free Mg in cerebral vascular smooth muscle cells: possible relation to alcohol-induced behavioral and stroke-like effects

The acute effects of ethanol on intracellular free magnesium ions ([Mg2+]i) in cultured canine cerebral vascular smooth muscle cells (VSMCs) were studied by digital imaging microscopy using the Mg2+ fluorescent probe mag-fura-2. In 0 mM ethanol, the basal level of [Mg2+]i was between 500-700 microM with a heterogeneous distribution within the cells; [Mg2+]i was greater in the perinuclear than in the peripheral region. Treatment of the cells with 10, 25, and 100 mM ethanol resulted in rapid (within 30 s) concentration-dependent reduction in [Mg2+]i; the greater the concentration and the greater the duration of acute exposure, the greater the fall in [Mg2+]i. Exposure of cerebral VSMCs to 100 mM ethanol resulted in a 57% reduction in [Mg2+]i (i.e., from 510 +/- 40 to 220 +/- 30 microM). These observations are consistent with the tenet that "binge drinking" of ethanol could result in cerebrovasospasm, ischemia, and rupture of cerebral blood vessels as a consequence of depletion of cerebral VSMC [Mg2+]i. Deficits in [Mg2+]i, O2, and nutrient delivery could account in part for some of the behavioral actions of alcohol.

Sex pheromone for the brownbanded cockroach is an unusual dialkyl-substituted alpha-pyrone

Female brownbanded cockroaches, Supella longipalpa, emit a sex pheromone that attracts males from a distance. This pheromone was isolated and identified as 5-(2,4-dimethylheptanyl)-3-methyl-2H-pyran-2-one (which we refer to as supellapyrone), and its structure was confirmed by synthesis. A racemic blend of the synthetic compound elicited behavioral and electrophysiological responses comparable to the natural pheromone across a range of doses. This compound is not only a very different type of cockroach pheromone but also makes up an additional class of natural products--namely, 3,5-dialkyl-substituted alpha-pyrones.

Ethanol-induced contraction of cerebral arteries in diverse mammals and its mechanism of action

Acute ethanol exposure (8-570 mM) induced potent contractile responses of rings in both basilar and middle cerebral arteries, from dogs, sheep, piglets and baboons, in a dose-dependent manner. The contractions were reproducible and not tachyphylactic. The middle cerebral arteries were found to be more sensitive to ethanol than the basilar arteries. No known pharmacological antagonist, tested, exerted any effects on ethanol-induced contractions. No differences in responsiveness to ethanol in canine cerebral arteries were found between male and female animals or between the presence and the absence of endothelial cells. Removal of extracellular Ca2+ ([Ca2+]o) partially attenuated ethanol-induced contractions, while withdrawal of extracellular Mg2+ ([Mg2+]o) potentiated such contractions. In the complete absence of [Ca2+]o, caffeine and ethanol induced similar, transient contractions followed by relaxation in K(+)-depolarized cerebral vascular tissue. Ethanol-induced contractions were completely abolished by pretreatment of tissues with caffeine. Our results suggest that: (a) acute ethanol intoxication can induce direct contractions (independent of amine, prostanoid or opioid mediation) of diverse mammalian cerebral vascular tissues, including those from primates; (b) these contractile responses are heterogeneous along the cerebrovascular tree and independent of endothelial cells; (c) in addition to a need for [Ca2+]o, an intracellular release of Ca2+ is needed for ethanol to induce contractions; and (d) hypomagnesemia or Mg deficiency potentiates the contractile effects of ethanol on brain vessels and may be a risk factor for ethanol-related, ischemic stroke events.

The fish odour syndrome: biochemical, familial, and clinical aspects

OBJECTIVES

To study the biochemical, familial, and clinical features of the fish odour syndrome among subjects with suspected body malodour.

DESIGN

Subjects who responded to a newspaper article were screened for the fish odour syndrome by interview and biochemical tests. Families of subjects with the syndrome were tested if possible.

SETTING

St Mary's Hospital, London, and some interviews at subjects' homes.

SUBJECTS

187 subjects (28 males) with suspected body malodour, of whom 156 (19 males) underwent biochemical tests. Five families of six of the subjects with the fish odour syndrome agreed to further tests.

MAIN OUTCOME MEASURES

Amounts of trimethylamine and trimethylamine N-oxide in urine collected over 24 hours under normal dietary conditions and for eight hours after oral challenge with 600 mg trimethylamine.

RESULTS

The fish odour syndrome was diagnosed in 11 subjects: the percentage of total trimethylamine excreted in their urine samples that was oxidised to trimethylamine N-oxide was < 55% under normal dietary conditions and < 25% after oral challenge with trimethylamine (in normal subjects > 80% of trimethylamine was N-oxidised). Parents of six of the subjects with the syndrome were tested: all showed impaired N-oxidation of excreted trimethylamine (< 80%) after oral challenge, indicating that they were heterozygous carriers of the allele for the syndrome. The syndrome was associated with various psychosocial reactions including clinical depression.

CONCLUSIONS

The fish odour syndrome can be inherited in an autosomal recessive fashion. It should be considered as a possible causative factor in patients complaining of body malodour.

Cocaine induces rapid loss of intracellular free Mg2+ in cerebral vascular smooth muscle cells

Acute exposure of cultured canine cerebral vascular smooth muscle cells to low concentrations of cocaine HCl (10(-9) to (10(-7) M) resulted in significant, rapid (1 min) loss of intracellular free Mg ions ([Mg2+]i); these reductions (12-25%) in [Mg2+]i were reversible upon exposure to normal, Mg(2+)-containing physiological salt solution. These findings help to provide a rational basis for why cocaine can result in cerebrovasospasm and stroke.

Mg2+ and caffeine-induced intracellular Ca2+ release in human vascular endothelial cells

Interaction of ionized magnesium ([Mg2+]o) and caffeine in regulation of intracellular free calcium concentration ([Ca2+]i) in human aortic endothelial cells was studied using fura-2 and digital imaging microscopy. In 1.2 mM [Mg2+]o, basal [Ca2+]i was 73.7 +/- 22.4 nM, with a heterogeneous distribution within the cells. No significant changes of basal [Ca2+]i were found either when cells were treated with 10 mM caffeine or when [Mg2+]o was lowered from 1.2 mM to 0.3 mM. However, a combined superfusion of the cells with 0.3 mM [Mg2+]o and 10 mM caffeine resulted in a significant elevation of [Ca2+]i to 382.8 +/- 57.1 nM, probably by release of Ca2+ from internal stores, which was attenuated by NiCl2 (1 mM). These results suggest that a Ca(2+)-induced Ca2+ release mechanism is involved in regulation of [Ca2+]i in endothelial cells, which may be either regulated or modulated by Mg2+.

SCH 38057: a picornavirus capsid-binding molecule with antiviral activity after the initial stage of viral uncoating

The activity of a new water-soluble molecule, SCH 38057, against picornaviruses is described. SCH 38057 inhibited plaque formation of selected entero- and rhinoviruses in a range of 10.2 to 29.1 microM (50% endpoint) and had a therapeutic index of 10 against poliovirus type 2 (polio 2) in HeLa cells. When administered orally or subcutaneously, SCH 38057 protected mice infected with either coxsackievirus B3 (CVB3) or echovirus-9 from mortality. The molecule provided a low level of protection against thermal inactivation of virus, indicating that SCH 38057 interacts with the picornavirus capsid. Binding studies with [3H]SCH 38057 revealed that the molecule binds to CVB3 and human rhinovirus 14 (HRV14) in a ratio of 29 and 19 molecules per viral particle, respectively. The affinity constant for SCH 38057 binding to CVB3 was 7.0 x 10(-4) M. When added to cultures of infected cells at 3 h after infection, SCH 38057 markedly inhibited viral RNA synthesis. This finding with lack of inhibition of attachment and loss of infectious virus after attachment were interpreted to indicate that, although SCH 38057 binds to the viral capsid, the molecule exerts its antiviral effect after the initial stage of picornavirus uncoating, i.e., after conversion of the 156S infectious viral particle to smaller subviral species.

Structure determination of antiviral compound SCH 38057 complexed with human rhinovirus 14

SCH 38057 (1-[6-(2-chloro-4-methoxyphenoxy)-hexyl]imidazole hydrochloride) is a new, water-soluble antiviral compound that has inhibitory activities against a number of picornavirus infections. The structure of the human rhinovirus 14 (HRV14) complex with SCH 38057 was determined at 3.0 A resolution by single-crystal diffraction techniques using synchrotron X-radiation. SCH 38057 was found to bind at the innermost end of the hydrophobic pocket within the capsid protein VP1, a locus of binding of other antipicornaviral agents; however, the complex differs from previously reported complexes in two important aspects. It leaves a considerable volume near the entrance to the binding pocket unoccupied. In addition, the alterations in the conformation of the VP1 polypeptide are similar to, but more extensive than those observed in HRV14 complexes with other antiviral agents. Although only 9 amino acids of VP1 have close contacts with the SCH 38057 molecule (within 3.6 A), at least 36 amino acids from both VP1 and VP3 have significantly altered conformations (C alpha movement > 0.5 A versus native). The structures of complexes of HRV14 with SCH 38057 and WIN 51711 are compared. Aromatic ring interactions between picornavirus capsid residues and antiviral inhibitors are proposed to be among the major determinants for positioning of these compounds.

Effects of 5-hydroxymethyl-2'-deoxyuridine and 3-aminobenzamide on chromosome aberrations in cultured human lymphocytes

Effects of 5-hydroxymethyl-2'-deoxyuridine (HmdUrd, a thymidine analog) and 3-aminobenzamide (3AB) on chromosome aberrations in cultured human lymphocytes were studied. The results show that HmdUrd is an effective clastogen in human peripheral lymphocytes. When cells were treated with HmdUrd and 3AB, a synergistic effect on chromatid gaps, breaks and exchanges was found. These findings support the hypotheses that 5-hydroxymethyluracil (HmUra) residues in DNA are formed and then removed by the action of 5-HmUra-DNA glycosylase (Teeber et al., 1984) and that 3AB interferes with the completion of DNA repair following HmUra excision.

Extracellular magnesium regulates intracellular free Mg2+ in vascular smooth muscle cells

Regulatory effects of extracellular magnesium ions ([Mg2+]o) on intracellular free ionized magnesium ([Mg2+]i) were examined in cultured vascular smooth muscle cells (VSMCs) from rat aorta by digital imaging microscopy using the Mg2+ fluorescent probe, Mag-fura-2. With normal Mg2+ (1.2 mM)-containing incubation media, [Mg2+]i in VSMCs was 0.63 +/- 0.09 mM. The ratio of [Mg2+]i/[Mg2+]o was 0.52 +/- 0.07. Elevation of [Mg2+]o up to 4.8 mM induced consistent increments in [Mg2+]i (to a mean values of 1.63 +/- 0.08 mM) in 5 min and lowered the ratio of [Mg2+]i/[Mg2+]o to 0.34 +/- 0.02. Our data suggest that [Mg2+]o can regulate [Mg2+]i, which may be related to its effects on intracellular Ca2+ ([Ca2+]i) and tone of VSMCs.

Structure of HIV-1 reverse transcriptase/DNA complex at 7 A resolution showing active site locations

AIDS, caused by human immunodeficiency virus (HIV), is one of the world's most serious health problems, with current protocols being inadequate for either prevention or successful long-term treatment. In retroviruses such as HIV, the enzyme reverse transcriptase copies the single-stranded RNA genome into double-stranded DNA that is then integrated into the chromosomes of infected cells. Reverse transcriptase is the target of the most widely used treatments for AIDS, 3'-azido-3'-deoxythymidine (AZT) and 2',3'-dideoxyinosine (ddI), but resistant strains of HIV-1 arise in patients after a relatively short time. There are several nonnucleoside inhibitors of HIV-1 reverse transcriptase, but resistance to such agents also develops rapidly. We report here the structure at 7 A resolution of a ternary complex of the HIV-1 reverse transcriptase heterodimer, a monoclonal antibody Fab fragment, and a duplex DNA template-primer. The double-stranded DNA binds in a groove on the surface of the enzyme. The electron density near one end of the DNA matches well with the known structure of the HIV-1 reverse transcriptase RNase H domain. At the opposite end of the DNA, a mercurated derivative of UTP has been localized by difference Fourier methods, allowing tentative identification of the polymerase nucleoside triphosphate binding site. We also determined the structure of the reverse transcriptase/Fab complex in the absence of template-primer to compare the bound and free forms of the enzyme. The presence of DNA correlates with movement of protein electron density in the vicinity of the putative template-primer binding groove. These results have important implications for developing improved inhibitors of reverse transcriptase for the treatment of AIDS.

The neurospora CYT-18 protein suppresses defects in the phage T4 td intron by stabilizing the catalytically active structure of the intron core

The Neurospora CYT-18 protein, a tyrosyl-tRNA synthetase, which functions in splicing group I introns in mitochondria, promotes splicing of mutants of the distantly related bacteriophage T4 td intron. In an in vivo assay, wild-type CYT-18 protein expressed in E. coli suppressed mutations in the td intron's catalytic core. CYT-18-suppressible mutations were also suppressed by high Mg2+ or spermidine in vitro, suggesting they affect intron structure. Both the N- and C-terminal domains of CYT-18 are required for efficient splicing, but CYT-18 with a large C-terminal truncation retains some activity. Our results indicate that CYT-18 interacts with conserved structural features of group I introns, and they provide direct evidence that a protein promotes splicing by stabilizing the catalytically active structure of the intron RNA.

[A mid-infrared spectra study of a series of benzocrown ether and macrocyclic polyether diester]

With a Nicolet 20 SX B Fourier Transform infrared spectrometer, the mid-infrared spectra in region of 4000-400 cm-1 were observed for a series of benzocrown ether and macrocyclic polyether diester. A difference in the wavelength of absorption of the ether bond was found between benzocrown ether and macrocyclic polyether diester. The wavelength of absorption of the ether bond of the compounds I-IV moved down about 25 cm-1, as compared with that of the compounds V-IX.

Magnesium regulates intracellular free ionized calcium concentration and cell geometry in vascular smooth muscle cells

Regulatory effects of extracellular magnesium ions ([Mg2+]o) on intracellular free ionized calcium ([Ca2+]i) were studied in cultured vascular smooth muscle cells (VSMCs) from rat aorta by use of the fluorescent indicator fura-2 and digital imaging microscopy. With normal Mg2+ (1.2 mM)-containing incubation media, [Ca2+]i in VSMCs was 93.6 +/- 7.93 nM with a heterogeneous cellular distribution. Lowering [Mg2+]o to 0 mM or 0.3 mM (the lowest physiological range) resulted in 5.8-fold (579.5 +/- 39.99 nM) and 3.5-fold (348.0 +/- 31.52 nM) increments of [Ca2+]i, respectively, without influencing the cellular distribution of [Ca2+]i. Surprisingly, [Mg2+]o withdrawal induced changes of cell geometry in many VSMCs, i.e., the cells rounded up. However, elevation of [Mg2+]o up to 4.8 mM only induced slight decrements of [Ca2+]i (mean = 72.0 +/- 4.55 nM). The large increment of [Ca2+]i induced by [Mg2+]o withdrawal was totally inhibited when [Ca2+]o was removed. The data suggest that: (1) [Mg2+]o regulates the level of [Ca2+]i in rat aortic smooth muscle cells, and (2) [Mg2+] acts as an important regulatory ion by modulating cell shapes in cultured VSMc and their metabolism to control vascular contractile activities.

Ethanol decreases cytosolic-free calcium ions in vascular smooth muscle cells as assessed by digital image analysis

Effects of ethanol on intracellular-free Ca2+ concentration in cultured rat aortic smooth muscle cells were examined by digital imaging fluorescence microscopy using the Ca2+ fluorescence indicator, fura-2. Ethanol induced dose-dependent decrements in cytosolic-free Ca2+ concentration at 45 mM and 90 mM, which was consistent with previously reported observations of relaxation in intact rat aortic tissues. However, ethanol at high pharmacological concentrations (e.g., 450 mM) failed to induce any further inhibition in cytosolic-free Ca2+ concentration. Our results suggest that the vasodilator effects of ethanol, observed on intact blood vessels, may result in part from an interference with the availability of Ca2+ for excitation-contraction coupling in vascular smooth muscle cells.

Interactions of magnesium and chloride ions on tone and contractility of vascular muscle

Replacement of extracellular chloride ions ([Cl-]o) by other anions, on contractility and the effects of extracellular magnesium ions ([Mg2+]o) on spontaneous mechanical activity, as well as on agonist-induced responses of rat aorta and portal vein, were studied. Replacement of [Cl-]o with acetate (Ac-) or isethionate (Ise-) ions resulted in an increase and decrease, respectively, of the spontaneous mechanical activity frequency in portal vein; the amplitudes of the spontaneous mechanical activity were attenuated by Ac- and Ise- substitution. Withdrawal of [Mg2+]o in Cl(-)-containing media resulted in elevation of tension development in rat aortas, whereas a similar maneuver in media with Ac- or Ise-, substituted for [Cl-]o, resulted in abrogation of this tension development. Use of disulfonic stilbene anion-channel blockers, DIDS (4,4'-diisothiocyano-2,2'-stilbene disulfonate, 400-600 microM) and SITS (4,4'-acetamido-4'-isothiocyano-2,2'-stilbene disulfonic acid, 400-600 microM), failed to influence either spontaneous mechanical activity or basal tone of rat portal portal vein or aortas. Incubation of DIDS or SITS in Mg(2+)-free media also failed to influence mechanical responses to withdrawal of [Mg2+]o. Use of the Cl- cation transport inhibitor bumetanide (30-80 microM) also failed to alter spontaneous mechanical activity or basal tone in either the presence or absence of [Mg2+]o. Ac- and Ise- substitution attenuated norepinephrine- and K(+)-induced contractile responses in portal vein and aorta, Caffeine-induced contractions of aortas were potentiated by withdrawal of [Mg2+]o in Cl(-)-containing media but inhibited in Ac(-)- or Ise(-)-substituted solutions. In the presence of [Mg2+]o, substitution of foreign anions resulted in alterations in the agonist contractile dose-response curves; EC50s were increased whereas maximum tensions were depressed. Withdrawal of [Mg2+]o amplified these effects. Substitution of Ac- or Ise- for [Cl-]o in the presence or absence of [Mg2+]o depressed contractions induced by Ca acetate in aortas and portal vein. These results suggest that: (1) Cl- plays an important role in regulating spontaneous mechanical activity, basal tone, and contractility in rat aorta and portal vein; and (2) Cl- probably physiologically mediates some of the effects and actions of [Mg2+]o on intracellular release of and influx of Ca2+ in these smooth muscles.

Sexual dimorphism of vascular smooth muscle responsiveness is dependent on anions and estrogen

Alteration of the extracellular anion environment by replacement of chloride ions (Cl-) with thiocyanate ions (SCN-) in normal Krebs-Ringer bicarbonate solution (NKRB) induced sustained development of basal tension in isolated aortas from male adult Sprague-Dawley and Long-Evans rats, but not from females of these strains. However, aortic smooth muscle isolated from sexually immature male and female Wistar rats underwent more marked tension development under such treatment, exhibiting no gender differences. Such SCN(-)-induced contractile responses are not tachyphylactic, completely dependent on extracellular calcium ([Ca2+]0), and could be aborted (relaxed to basal tone) by readmission of Cl-. Castration and replacement of male sex hormones with estradiol inhibited SCN(-)-induced contractions in isolated aortas from adult Wistar male rats, while castration and testosterone supplementation failed to induce contraction in aortic muscle of adult female Wistar rats exposed to SCN-. We believe these data are compatible with the notion that gender differences in vascular activity may be modulated by actions of estradiol on the metabolism of Cl- and other anions in vascular smooth muscle, which may be linked to transport of Ca2+ across the vascular muscle cell membrane.

Endothelial cells are required for inhibition of contractile responses induced by reduction in extracellular magnesium and sodium ions in rat aortic smooth muscle [corrected]

The possible importance of facilitation of sodium-calcium (Na(+)-Ca2+) exchange by removal of extracellular magnesium ions ([Mg2+]o) in expression of endothelium-dependent relaxation was investigated in aortic rings isolated from female rats. Simultaneous [Mg2+]o withdrawal (0 mM Mg2+) and reduction in extracellular Na+ (Total [Na+]o = 84 mM), by replacement of NaCl with isosmolar amounts of sucrose in normal Krebs-Ringer bicarbonate (NKRB), induced significant increases of basal tone of denuded rat aortic rings, but not in tissues with intact endothelium. These vascular effects were not affected by indomethacin, phentolamine or atropine in any of the tissues tested. Reintroduction of 1.2 mM Mg2+ or removal of extracellular Ca2+ ([Ca2+]o) from the Mg2+ and Na(+)-deficient incubation media induced complete relaxation of the denuded tissues. Methylene blue (10(-5) M), an inhibitor of endothelium-derived relaxant factor (EDRF), potentiated tension development in intact tissues. These results suggest that: (1) as in vascular muscle, Mg2+ plays an important role in Ca2+ homeostasis in endothelial cells (EC), probably via Na(+)-Ca2+ exchange; and (2) such Mg(+)-regulated internal Na(+)-dependent Ca2+ entry participates in the expression of endothelium-dependent relaxation.

Sister chromatid exchanges in the human active and inactive X chromosomes

Four human female fibroblast strains with an i(Xq) or derivative X chromosome as a cytological marker for the inactive X chromosome were used to determine the frequency of sister chromatid exchanges (SCEs) in the active and inactive X chromosomes. No significant difference in SCE frequency between the active and inactive X chromosomes was observed. Therefore, the state of chromatin condensation and the late DNA replication in the facultative heterochromatin of the inactive X chromosome do not appear to influence the SCE frequency.

Size characterization of Mycobacterium bovis BCG (Bacillus Calmette Guérin) vaccine, Tice substrain

Reconstituted, lyophilized, attenuated Mycobacterium bovis, Bacillus Calmette Guérin (BCG) vaccine, Tice substrain, was characterized using a Coulter Multisizer and a HIAC/Royco counter. The primary organism has an equivalent spherical diameter approximating 1 micron but the BCG cell suspension is heavily aggregated. The cumulative size distribution of the suspension fits a log-probit plot and this information can be used to determine the total number of particles per ampoule. The instrumental count may be related to the viable count. The state of dispersion was unaffected by mild shear (syringe aspiration or ultrasound) and only slightly affected by the addition of cetylpyridinium chloride or sodium tauroglycolate.

DA/DAPI-fluorescent heteromorphism of human Y chromosome

Variation of DA/DAPI intensity in the Yq12 band was observed in five amniotic cell specimens and one blood specimen from the father of one fetus. Three distinct classes of Yq heterochromatin were identified by distamycin A (DA) treatment of the cell cultures and various staining techniques. The heterochromatin in the Yq11.23 sub-band does not undercondense when exposed to DA, and shows pale fluorescence with quinacrine staining, positive C-banding, and bright fluorescence with DA/DAPI technique. This class of heterochromatin was consistently observed in all specimens studied. The other two classes of heterochromatin are in the Yq12 band. Both show undercondensation when exposed to DA, quinacrine-bright fluorescence, and positive C-banding; however, one class of heterochromatin shows DA/DAPI-bright fluorescence and the other shows pale fluorescence. The size and banding intensity of the two classes of heterochromatin in Yq12 are variable. These results provide cytological evidence of heterogeneity within the Y heterochromatin region containing AT-rich DNA.

Chronic lymphocytic leukemia in China

Chronic lymphocytic leukemia (CLL) is a very common form of leukemia among middle-aged and elderly persons in Western countries. In the Japanese, or in those with Japanese ancestry born and living in the USA, CLL is rather rare. It is also rare in China, but convincing data to support this statement are found primarily in the Chinese literature. We have reviewed previously unpublished data from Peking Union Medical College (PUMC) concerning the frequency of CLL among adult patients with the four common types of leukemia. Of 4,174 such patients (1952-1986), 4.6% had CLL; 22.9% chronic myeloid leukemia (CML); 50.3% acute myeloid leukemia (AML); and 22.3% acute lymphoblastic leukemia (ALL). This low frequency of CLL is none the less higher than that found in a multiinstitutional collection of Chinese patients with leukemia. Various clinical and laboratory aspects of a carefully studied, previously published group of patients with CLL from PUMC were compared to similar published findings in patients from the University of Utah. No differences in the overall nature of the disease were detected between these groups. However, not unexpectedly, the duration of symptoms before the diagnosis was made longer in Chinese than in USA patients and the proportion diagnosed at a time when no CLL related symptoms had been noted was less in Chinese. Neither differences in life span in the two populations nor an excess of CML, AML, and ALL at the expense of CLL were viable hypotheses to explain the rarity of CLL in China. We suggest that the dearth of CLL in Chinese is on a genetic basis, as it is thought to be in the Japanese.

Effect of C-banded heterochromatin on centromere separation

The present study is to determine the effects of centromeric heterochromatin on centromere separation. Amniotic cell cultures in which the centromeric heterochromatin of one chromosome was at least twice as large (qh+) as the heterochromatin (qh) in the homologous chromosome were selected. Fifteen amniotic cell samples with 1qh+, 9qh+ or 16qh+ were studied. The size of the centromeric heterochromatin was directly correlated with the delay in centromere separation. The chromosome with the smaller centromeric heterochromatin tended to show earlier centromere separation than the homologue with the larger heterochromatin. Our results suggest that the quantity of centromeric heterochromatin may influence the genetic control of centromere separation.

Investigations of primary and secondary structure of porcine ubiquitin. Its N epsilon-acetylated lysine derivative

N epsilon-acetylation in vitro of internal lysyl residues of Ub by p-nitro-phenyl acetate at pH 8.0 was performed. The position of acetylation sites are determined. (e.g. Fully acetylated: Lys-6, Lys-11 and Lys-33; partially free internal lysines: Lys-27, Lys-29; Lys-48 and probably Lys-63.) 55 cycles Edman degradation were performed and the first 53 N-terminal residues were identified. Secondary structural studies of ubiquitin have been carried out using the circular dichroism (CD) technique. No changes are noted upon heating to 100 degrees C at neutral pH even in the presence of 8 M urea but in 6 M guanidine-HCl extensive modification results. Ubiquitin with an average of 4.4 of its 7 lysines in the N epsilon-acetyl form shows little deviation from native protein. After reduction with dithiothreitol and subsequent removal of the mercaptan, significant changes in the secondary structure are noted. Circular dichroic measurements of ubiquitin indicated an alpha-helical content of about 10% whereas the secondary structural predictions of Chou and Fasman suggest a level of about 45%.