The intracellular assembly of antigenic-peptide-class II complexes

The immune system employs remarkable strategies to ensure that foreign antigens, from the most complex pathogens to the simplest proteins, are displayed on the surfaces of cells which are targets of T lymphocyte recognition. At the heart of these strategies is the molecular transformation of a soluble protein antigen to a complex of a small peptide containing the antigenic determinant bound to a cell surface Major Histocompatibility Complex class I or class II protein. This process is termed antigen presentation. Progress in a variety of laboratories over the last several years has yielded a wealth of information about the molecular mechanisms underlying antigen presentation, providing potential new approaches to vaccine design. Here we describe recent studies in our laboratory aimed at elucidating the intracellular site in B lymphocytes in which antigenic peptide-class II complexes are assembled for recognition by helper T cells and the regulation of this assembly process. Our results suggest that processed antigen-class II complexes are assembled in a unique compartment in the endocytic route which contains all the necessary cellular and molecular machinery for assembly and that B cells regulate the assembly process in response to external and internal signals.

Inhibition of inducible nitric oxide synthase ameliorates cerebral ischemic damage

We sought to determine whether expression of the inducible, calcium-independent isoform of nitric oxide synthase (iNOS) contributes to the tissue damage produced by focal cerebral ischemia. The middle cerebral artery was occluded in halothane-anesthetized spontaneously hypertensive rats. Twenty-four hours later rats received intraperitoneal injections of the iNOS inhibitor aminoguanidine (100 mg/kg twice per day; n = 10) or of aminoguanidine + L-arginine (300 mg/kg four times per day; n = 7), aminoguanidine + D-arginine (n = 7), arginine alone (n = 6), or vehicle (n = 9). Drugs were administered for 3 consecutive days. Infarct volume was determined by image analysis in thionin-stained brain sections 4 days after induction of ischemia. Administration of aminoguanidine reduced infarct volume by 33 +/- 4% (P < 0.05 from vehicle; analysis of variance and Tukey's test), a reduction that was antagonized by coadministration of L- but not D-arginine. Administration of L-arginine alone did not affect infarct size (P > 0.05 vs. vehicle). In separate rats (n = 10), aminoguanidine attenuated calcium-independent NOS activity in the infarct (P < 0.05 vs. vehicle) without affecting calcium-dependent activity (P > 0.05). Aminoguanidine did not affect resting cerebral blood flow or the cerebrovascular vasodilation elicited by hypercapnia, as determined by laser-Doppler flowmetry (n = 4). We conclude that aminoguanidine selectively inhibits iNOS activity in the area of infarction and reduces the volume of the infarct produced by middle cerebral artery occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Helix formation in model peptides based on nucleolin TPAKK motifs

The structures formed by peptide models of the N-terminal domain of the nucleolar protein nucleolin were studied by CD and nmr. The sequences of the peptides are based on the putative nucleic acid binding sequence motif TPAKK. The peptides TP1 and TP2 have the sequence acetyl-G(ATPAKKAA)nG-amide, with n = 1 and 2, respectively. CD measurements indicate structural changes in both peptides when the lysine side chains are uncharged by increasing the pH or acetylation of the side-chain amines. When trifluoroethanol (TFE) is added, more extensive structural changes are observed, resembling helical structure based on nmr nuclear Overhauser effect (NOE) and C alpha proton chemical shift changes, and CD spectra. The structure formed in 0.5M NaClO4 as observed by nmr is similar to that when the lysine side chains are acetylated, due presumably to interactions of perchlorate ion with side-chain charges on lysines. The helical structure observed in TPAKK motifs may be stabilized via N-capping interactions involving threonine. The structures observed in TFE suggest that the Thr-Pro sequence initiates short helical segments in TPAKK motifs, and these helical structures might interact with nucleic acids, presumably via interactions between lysines and threonines of nucleolin.

Marked induction of calcium-independent nitric oxide synthase activity after focal cerebral ischemia

We studied the effect of focal cerebral ischemia on inducible (iNOS) and constitutive (cNOS) nitric oxide synthase enzymatic activities in the affected brain. The middle cerebral artery (MCA) was occluded in spontaneously hypertensive rats. Animals were killed 1, 2, 4, and 7 days later. cNOS and iNOS enzymatic activities were determined in the infarcted cortex using the assay of Bredt and Snyder. cNOS was assayed in the presence of calcium, whereas iNOS was assayed in the absence of calcium and in the presence of tetrahydrobiopterin. The validity of the iNOS assay was verified in rats treated with bacterial lipopolysaccharide. In these animals, the magnitude of the induction of iNOS enzymatic activity in lung, spleen, and brain paralleled the expression of iNOS mRNA, assessed by reverse-transcription polymerase chain reaction. After MCA occlusion, calcium-dependent (cNOS) activity was markedly reduced only in lesioned cerebral cortex at days 1-7 (p < 0.001; analysis of variance and Tukey's test). In contrast to cNOS, calcium-independent (iNOS) activity was induced substantially in the infarct (p < 0.005) but not in the contralateral intact cortex (p > 0.05). iNOS activity peaked at day 2 and was not different from baseline at day 7 (p > 0.05). No NADPH diaphorase-positive neurons were observed in the area of the lesion at days 1-7. Macrophages appeared at day 2 and invaded the infarcted tissue by day 7. At this time, numerous glial fibrillary acidic protein-positive astrocytes were observed within the lesion. The results suggest that the decline in calcium-dependent (cNOS) activity reflects loss of NOS neurons within the lesion.(ABSTRACT TRUNCATED AT 250 WORDS)

Exposure-response relationship between passive smoking and adult pulmonary function

The effects of exposure to environmental tobacco smoke (ETS) on pulmonary function were investigated in a random sample of 1,033 adults aged 40 to 69 yr from a residential area in Beijing. Compared with those not exposed, those exposed to ETS either at home or at work were associated with a 102-ml (SE = 40 ml) reduction in FEV1 and a 151-ml (SE = 44 ml) reduction in FVC after adjustment for confounding factors. Home and work ETS exposure was respectively associated with a 102-ml (SE = 33 ml) and 61-ml (SE = 34 ml) reduction in FEV1. When the subjects were grouped into three exposure categories (none, home only or work only, and both), the deficits in FEV1 and FVC in the third category were the greatest and statistically significant. The adverse effects of ETS were consistently observed in stratified analyses according to sex, occupational exposure, indoor use of coal stoves, and education. When ETS exposure was measured by the cigarettes smoked by other household members at home per day, an exposure-response association with FEV1 and FVC was again statistically significant. In conclusion, this study demonstrated that there is a significant association between exposure to ETS and reduced levels of FEV1 and FVC in adults, and such an association is dose-dependent.

Occupational Stress and Dysmenorrhea in Women Working in Cotton Textile Mills

The authors conducted a cross-sectional study of 895 never-smoking female textile workers, aged 20-40 years, employed in three cotton textile mills in Anhui Province, China, to assess the association of self-reported occupational stress with dysmenorrhea. Stress was assessed by means of a questionnaire incorporated into a larger, general health survey of textile workers. Dysmenorrhea was defined as abdominal/pelvic pain during menses. Proportions of no/low, moderate, and high levels of occupationally-related emotional stress among all the subjects were 56%, 23%, and 21%, respectively. The overall prevalence of dysmenorrhea in the population was 59.7%. The adjusted odds ratios of dysmenorrhea for women who had moderate and high levels of occupational stress relative to those with low levels were 1.6 (95% CI:1.1-2.2) and 2.3 (95% CI:1.6-3.4), suggesting an exposure-response relationship. The estimated odds ratio based on assigned scores (0, 1, and 2 assigned for no/low, moderate, and high degrees of occupational stress) was 1.5 (95% CI:1.3-1.8). In the analyses stratified by the mills and the women's job titles, a positive association was found in all groups. The association remained significant (OR = 1.6, 95% CI:1.3-2.0) when the analysis was restricted to those women with only one reported livebirth pregnancy. The findings suggest that high degrees of occupational stress predispose female textile workers to dysmenorrhea.

Two murine GSTpi genes are arranged in tandem and are differentially expressed

An 8-kilobase mouse genomic fragment containing two intact glutathione S-transferase (GST) genes has been isolated from a mouse lambda genomic library. Each of the genes (designated mGSTpiA and mGSTpiB) is less than 3 kilobases in size and is comprised of seven exons that give rise to a 630-base pair open reading frame encoding 209 amino acids. The deduced amino acid sequences of the gene products differ in only 6 amino acids at positions 10, 11, 89, 104, 106, and 109. These two genes are highly homologous to rat GST-P and to a lesser extent to human GST-pi. Northern blot analysis of mRNAs from a variety of mouse tissues demonstrated that mGSTpiB is ubiquitously expressed, whereas mGST-piA is more selectively expressed in gallbladder, colon, heart, and skeletal muscle. Primer extension analysis revealed four potential transcription start sites in mGST-piB and one in mGSTpiA. Although both genes were expressed in vitro and in vivo only mGSTpiB product metabolized 1-chloro-2,4-dinitrobenzene, a common GST substrate. Further in vitro expression studies of three chimeric mGSTpi genes suggested that one or both of the amino acids at positions 10 and 11 of mouse GSTpi enzymes are important for the enzyme's ability to metabolize 1-chloro-2,4-dinitrobenzene.

Nonimmunoselected intrastrain genetic variation detected in pairs of high-yielding influenza A (H3N2) vaccine and parental viruses

Seven influenza A (H3N2) high-yielding vaccine candidate strains were examined. Antigenic analysis revealed that 5 of the strains could be distinguished antigenically from their corresponding wild type parent viruses. Comparative sequence data for the HA1 domains of the HA (hemagglutinin) genes for these 5 high-yielding viruses and the corresponding wild type parents demonstrated one to three amino acid substitutions within each virus pair, with at least one amino acid change being located in a previously defined antigenic site. Comparison of the HA sequences of the 2 antigenically indistinguishable virus pairs revealed no amino acid differences in 1 and one amino acid change in the other. Examination of 1 additional wild type virus, A/Guangdong/39/89, and its three high-yielding derivatives obtained either by serial egg passage or by reassortment revealed an additive effect of the HA and M genes in creating the high-yielding phenotype.

A modified hepatitis B virus surface antigen with the receptor-binding site for hepatocytes at its C terminus: expression, antigenicity and immunogenicity

A modified hepatitis B virus (HBV) surface antigen, the SA-28 protein, was constructed and expressed by recombinant vaccinia virus in mammalian cells. This protein was composed of a PreS1 region-derived peptide (amino acids 21 to 47) that contained the hepatocyte receptor-binding site, joined to the C terminus of the major S protein at amino acid position 223. This modified surface antigen could be efficiently assembled into particles with a density of 1.23 g/ml and could be secreted from several mammalian cell lines. The results of immunoprecipitation revealed that the SA-28 protein was recognized by both the anti-S protein antibody and the anti-PreS1 antibody. A strong antibody response, against both the S protein and PreS1 epitopes, was induced in BALB/c mice immunized by the SA-28 particles indicating good immunogenicity. These results suggested that the HBV surface antigen consisting of the SA-28 protein could be a promising candidate as a new HBV vaccine with higher efficacy.

Study on the role of mast cells in the development of liver fibrosis during diethylnitrosamine (DEN) -induced hepatocarcinogenesis in rats

The mast cells (MC) and their roles in the development of liver fibrosis during experimental hepatocarcinogenesis in rats have been studied immunohistochemically and electron microscopically. Pronounced MC hyperplasia occurred after beginning of the treatment of DEN. The vast majority of mast cells in fibrotic livers was present in thickened fibrous septa. Intracellular or pericytial collagen type IV and laminin staining were found in mast cells, collagen types I, III and fibronectin were negative. Mast cells mainly distributed in proximity to basement membrane and the electron microscopical observation revealed a close topographic relationship between mast cells and fibroblasts. The fibroblasts phagocytized the granules released by mast cells and thus were activated, showing enhanced formation of collagenous fibrils. The mast cells may be derived from blood circulation or replicated in situ. Those findings indicated that mast cells take part in the process of fibrosis at least by two ways: (1) It directly synthesizes the basement membrane components; (2) It stimulates the fibroblasts or other types of cells which have the potential functions in fibrogenesis by releasing granule mediators or cytokines acting upon the fibrosis process.

Neurologic outcome and heart resuscitability with closed-chest cardiopulmonary bypass after prolonged cardiac arrest times in rabbits

OBJECTIVES

To observe the influence of prolonged cardiac arrest times on neurologic outcome and heart resuscitability, using a resuscitation model with cardiopulmonary bypass in the rabbit, and to determine whether the changes in the plasma concentrations of lactate and lipoperoxide correlate with the severity of global brain ischemia.

DESIGN

Randomized, prospective, controlled animal trial.

SETTING

University research laboratory.

SUBJECTS

Forty-three New Zealand white rabbits.

INTERVENTIONS

Rabbits were randomly assigned to one of five groups: control, and four groups with cardiac arrest times of 8, 10, 12, and 15 mins. A bolus of 4 to 6 mL of 0.5-M potassium chloride was injected into the right atrium to induce cardiac arrest within 5 secs. Resuscitation was performed using closed-chest cardiopulmonary bypass, and mechanical ventilation with pure oxygen. When necessary, a DC shock of 10 joules/kg was used to terminate ventricular fibrillation.

MEASUREMENTS AND MAIN RESULTS

Hemodynamics, electroencephalogram, electrocardiogram, and return times of various cranial reflexes were observed throughout the experiment. Plasma concentrations of lactate and lipoperoxide were determined before cardiac arrest and 5, 30, 90, and 150 mins after resuscitation. The neurologic outcome, measured by Neurologic Deficit Score, was determined at 150 mins postresuscitation. Values for the Neurologic Deficit Score were: 8 +/- 8 in the control group; 31 +/- 13; 37 +/- 19; 69 +/- 22; and 62 +/- 26 in the cardiac arrest groups of 8, 10, 12, and 15 mins, respectively. No significant differences in cardiac resuscitability were found among the four cardiac arrest groups. The plasma concentrations of lactate and lipoperoxide were significantly higher than the prearrest levels; however, there were no significant differences among the four cardiac arrest groups.

CONCLUSIONS

Cardiopulmonary bypass can be used to establish a resuscitation model in rabbits. Neurologic outcome worsens progressively in proportion to the prolonged cardiac times, especially when it exceeds 10 mins. Cardiac resuscitability is still possible, even when arrest time exceeds 15 mins. Changes in plasma concentrations of lactate and lipoperoxide do not correlate with the neurologic outcome and heart resuscitability following cardiac arrest.

Persistence of the SV40 early region without expression in permissive simian cells

SV40 containing recombinant vectors were introduced into permissive simian, non-permissive rodent and semi-permissive human cell lines, and assayed for transformation. All mouse and human cell clones expressed T-antigen (T-Ag) and were morphologically transformed when they contained only the wt T-Ag gene (E-SV40) or the entire wt viral genome with an interrupted late region. However, of 63 simian clones with these recombinant vectors, none became morphologically transformed and T-Ag containing cells were rare or absent. Nearly all simian cell lines made either no detectable early SV40 RNA or only small amounts of viral RNA but contained viral DNA restriction fragments similar to those in the original recombinant vectors. Functional T-Ag genes were recoverable from several cell clones and used to regenerate infectious virus. Hence, T-Ag gene expression had been suppressed. We found two conditions where T-Ag expression was activated. In a BSC-1 cell line containing E-SV40 DNA, subsequent introduction of a vector with a functional viral late coding region (L-SV40) resulted in the appearance of T-Ag and transformation. These findings suggest that L-SV40 sequences activate or enhance T-Ag expression and that this activation requires a functional Vpl gene. We found also, that vectors with E-SV40 DNA from the bipartite variant EL-SV40 consistently transformed simian CV-1 cells. Transformation was shown to be effected by the multiple alterations present in the regulatory region of this variant.

Role of nitric oxide in the regulation of oxygen consumption in conscious dogs

The role of nitric oxide (NO) in the regulation of O2 consumption was studied in chronically instrumented conscious dogs. A specific NO synthesis inhibitor, nitro-L-arginine (NLA, 30 mg/kg i.v.), significantly increased mean arterial pressure from 100 +/- 4 to 134 +/- 5 mm Hg (mean +/- SEM) and total peripheral resistance by 157 +/- 16% and reduced cardiac output by 47 +/- 3% and heart rate by 34 +/- 6% after 120 minutes. Changes in arterial blood gases were not observed. There were significant changes in PO2 (-14 +/- 2 mm Hg), O2 saturation (-21 +/- 2%), the percentage of hemoglobin as oxyhemoglobin (-21 +/- 2%), and O2 content (-3.0 +/- 0.9 vol%) and a significant increase in percent reduced hemoglobin (21 +/- 1%) in mixed venous blood, associated with an increase in O2 extraction (5.1 +/- 0.2 vol%) (all P < .01). O2 consumption was increased from 124 +/- 6 to 155 +/- 9 mL/min (P < .05). Methoxamine, titrated to have hemodynamic effects similar to those of NLA (eg, mean arterial pressure increased from 97 +/- 4 to 131 +/- 5 mm Hg), had much smaller effects on venous blood gases, hemoglobin, and O2 extraction (2.3 +/- 0.7 vol%) and no significant effect on O2 consumption. NLA also caused an increase in O2 consumption of 37 +/- 8% (P < .01) in quietly resting conscious dogs that had undergone pretreatment with hexamethonium and atropine, but no significant change in O2 consumption in dogs anesthetized with barbiturate.(ABSTRACT TRUNCATED AT 250 WORDS)

Compartmentalization of Ca2+ signaling and Ca2+ pools in pancreatic acini. Implications for the quantal behavior of Ca2+ release

Streptolysin O-permeabilized pancreatic acini were used to study compartmentalization of Ca2+ signaling and Ca2+ pools. In these cells, the inositol 1,4,5-trisphosphate (IP3)-dependent Ca2+ channels could be activated by a number of agonists (carbachol, cholecystokinin, or bombesin) or by activation of the entire cellular phospholipase C pool with GTP gamma S. Surprisingly, each of the antagonists interacting with acinar cells inactivated the channels after stimulation with GTP gamma S. In addition, when permeabilized cells were stimulated with more than one agonist, any antagonist to the specific agonists employed inactivated the channels. The aberrant behavior of the antagonists in permeable cells was not related to a loss of specificity since (a) when added before GTP gamma S, the antagonists had no effect on Ca2+ release and (b) when cells were stimulated with a single agonist, the antagonists prevented only the effect of their specific agonist. The differential behavior of the antagonists in intact and permeable cells suggests a compartmentalization of Ca2+ signaling into separate, agonist-specific units that is modified by cell permeabilization. Further evidence for compartmentalization of signaling was obtained by showing that the partial agonist (the CCK octapeptide analogue JMV-180) can access and release only 50% of the cholecystokinin- or IP3-mobilizable Ca2+ pool in intact and permeable cells. Kinetic measurements revealed a multiphasic time course of agonist-evoked Ca2+ release in permeable cells. At high agonist concentrations, all phases were fast and merged into an apparent single event of Ca2+ release. The phases were separated by three independent protocols: reduction in agonist concentrations, addition of heparin, or addition of guanosine-5'-O-(thio)diphosphate. Since all protocols that caused phase separation reduce IP3-mediated Ca2+ release, these findings demonstrate heterogeneity in the affinity for IP3 of channels present in compartmentalized Ca2+ pools of the same cells. Compartmentalization of signaling and the heterogeneity in the affinity for IP3 resulted in a quantal agonist-evoked Ca2+ release. The overall findings are discussed in the context of an integrated model of compartmentalization of signaling complexes, Ca2+ pools, and IP3-activated Ca2+ channels.

Simultaneous determination of urinary creatinine, calcium and other inorganic cations by capillary zone electrophoresis with indirect ultraviolet detection

A method for the rapid analysis of calcium and creatinine in urine has been developed using capillary zone electrophoresis without sample pretreatment other than dilution. Cations of NH3, K, Na, Mg, Ca, Li, Ba and creatinine in human urine samples could be separated within 7 min. Background electrolyte (BGE) was composed of 5 mmol/l pyridine (chromophore), 3.6 mmol/l tartaric acid and 2 mmol/l 18-crown-6, having a pH of 4.05. An indirect UV detection mode was employed at 255 nm. Efforts were made to eliminate the interaction between cations and proteins and to minimize the electromigrative dispersion (EMD) for the analytes of interest by selecting a suitable BGE and sample dilution solution. Quantitative analyses were performed for calcium and creatinine. The calibration plots showed good linearity over the concentration range of interest to clinical analysis. Data on recoveries and reproducibilities are also reported. Results for urine samples (previously collected and frozen) from a variety of healthy and pathological individuals were in good agreement with those obtained by the Technicon SMA II calcium and creatinine methods.

Kinetics and crystal structure of a mutant Escherichia coli alkaline phosphatase (Asp-369-->Asn): a mechanism involving one zinc per active site

Using site-directed mutagenesis, an aspartate side chain involved in binding metal ions in the active site of Escherichia coli alkaline phosphatase (Asp-369) was replaced, alternately, by asparagine (D369N) and by alanine (D369A). The purified mutant enzymes showed reduced turnover rates (kcat) and increased Michaelis constants (Km). The kcat for the D369A enzyme was 5,000-fold lower than the value for the wild-type enzyme. The D369N enzyme required Zn2+ in millimolar concentrations to become fully active; even under these conditions the kcat measured for hydrolysis of p-nitrophenol phosphate was 2 orders of magnitude lower than for the wild-type enzyme. Thus the kcat/Km ratios showed that catalysis is 50 times less efficient when the carboxylate side chain of Asp-369 is replaced by the corresponding amide; and activity is reduced to near nonenzymic levels when the carboxylate is replaced by a methyl group. The crystal structure of D369N, solved to 2.5 A resolution with an R-factor of 0.189, showed vacancies at 2 of the 3 metal binding sites. On the basis of the kinetic results and the refined X-ray coordinates, a reaction mechanism is proposed for phosphate ester hydrolysis by the D369N enzyme involving only 1 metal with the possible assistance of a histidine side chain.

Schistosoma mansoni: fractionation and characterization of the glycocalyx and glycogen-like material from cercariae

The glycocalyx (GCX) that covers schistosomal cercariae is a complex molecule that has immunomodulating properties. Here, we purified milligram amounts of GCX using Anguilla lectin which binds to the GCX covering the cercarial body and tail. Typically, 10 million cercariae were extracted with phenol, dialyzed, and chromatographed on a Sepharose 2B-CL column. An average of 39 mg of total carbohydrate eluted near the void volume from which 31 mg of glycogen-like material was further separated by lectin affinity chromatography. Its identity was established by compositional analysis, sensitivity to amylase digestion, and its nuclear magnetic resonance spectrum. The lectin-bound GCX was eluted with 0.1 M fucose with a final yield of 5.3 mg carbohydrate. Fucose composed 40% of the total GCX carbohydrate with lesser but approximately equal amounts of galactose, glucosamine, and galactosamine present. NMR data indicated that the amino sugars were N-acetylated. Glucose was also present but in varying amounts in different preparations of GCX. Oligosaccharides were released from GCX by hydrazinolysis and separated by electrophoresis after reductive amination to 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS). Bands comigrating with standards containing 11, 12, 16, and 17 sugar residues were detected. Thus, the GCX is a complex structure composed of oligosaccharides, probably linked to a peptide.

PBP74, a new member of the mammalian 70-kDa heat shock protein family, is a mitochondrial protein

The cloning of a cDNA encoding a new member of the highly conserved mammalian 70-kDa heat shock protein (hsp 70) family termed PBP74 was recently reported. Critical to an understanding of the function of this new hsp 70 is delineating its subcellular localization. Here we use a variety of immunological and biochemical approaches both in vitro and in vivo to demonstrate that PBP74 is imported into and resides in mitochondria. By confocal immunofluorescence microscopy PBP74 is detected in mitochondria, colocalizing with the mitochondrial 60-kDa heat shock protein. To address the inherent problem of serological cross-reactivity among the hsp70 family members, an influenza virus hemagglutinin epitope tag was introduced into the PBP74 cDNA. The epitope-tagged PBP74 protein transiently expressed in L cells localized to mitochondria. Moreover, deletion of the N-terminal 46-amino acid presequence results in a cytosolic localization of the epitope-tagged protein. Cell fractionation studies demonstrated PBP74 in purified mitochondria in a protease-protected location. After coupled transcription-translation the precursor of PBP74 is imported into isolated yeast mitochondria, where it becomes processed to the mature protein. According to a subfractionation of the mitochondria, the imported protein was found to be localized in the matrix space. Import in vitro is time- and temperature-dependent, requires matrix ATP, and is abolished upon depletion of the membrane potential across the mitochondrial inner membrane. Similarly, in mammalian cells PBP74 is synthesized as a pre-protein that requires membrane potential-dependent import into mitochondria for its maturation. Taken together, our data demonstrate that PBP74 is a mammalian mitochondrial hsp70.

Anastomotic false aneurysm following abdominal aortic aneurysmectomy and prosthetic grafting

Anastomotic false aneurysm (AFA) of the aorta is a potentially lethal complication after prosthetic grafting. Nineteen aneurysms were encountered in 18 patients within a 30-year period (1960-1991). There were 10 men and 8 women, aged 27-80 years (mean 58 years). In 14 patients, the prostheses were made of silk, in 2 were PTFE, and in 1 each Dacron or silk-Dacron cross-weaved. Patients with an intact AFA had a pulsatile abdominal mass, abdominal pain, an occluded graft and peripheral emboli. Five patients were asymptomatic. Clinical onset of AFA varied from 2 weeks to 12 years (mean 5 years). The accurate rate of diagnosis of single plane angiography was 75% (3 of 4), and computed tomography 100% (ten of ten). Ultrasound was used only once and suggested an AFA. Four AFAs were less than 5cm in diameter. Five patients refused operation and died in 2 years from rupture. Operative mortality was 11% (1 of 9). Treatment was resection of AFA and replacement with a new graft. Life-long follow-up is required for patients with an aortic aneurysm. All ratroperitoneal AFAs should be resected, since the outcome of rupture is poor.

Estrogen receptor-mediated direct stimulation of colon cancer cell growth in vitro

In vivo and epidemiological data suggest a mitogenic role for estrogens (E) in colon cancer. The presence of estrogen receptor (ER) and ER mRNA in colonic epithelium and colon cancer cells, make it necessary to explore the possible direct effects of E on colon cancer growth. In this study, a 15-mer oligodoxynucleotide (oligo) antisense to the region of the translation start codon of estrogen receptor mRNA inhibited ER expression in a mouse colon cancer cell line (MC-26), as determined by receptor binding assay. Antisense oligo also decreased ER mRNA levels in MC-26 cells. The growth-stimulatory effect of E was abolished by antisense oligo treatment, demonstrating that the ER is directly involved in the regulation of colon cancer cell growth.

[Mechanism of changes in coagulation after electric burns in rabbits]

The changes in local lesion after high-voltage electric burns ares dependent on many factors. One of the important factors is the change in coagulation. In this paper, a high-voltage electrical burn model was reproduced in rabbits for the purpose of investigating the coagulation mechanism. It was found that AT-III and PC showed elevation and declination, respectively, at 6h and 12h postburn. PAI:A and t-PA:A also showed obvious changes, while FDP showed continuous elevation at 6h up to 5d postburn. The findings probable provided the explanation of the occurrence of thrombosis at 6h to 12h postburn, and the second episode of thrombosis on the 5th day.

SmgGDS stabilizes nucleotide-bound and -free forms of the Rac1 GTP-binding protein and stimulates GTP/GDP exchange through a substituted enzyme mechanism

The Rac proteins, Rac1 and Rac2, are essential components of the NADPH oxidase system of phagocytes and regulate the actin assembly associated with membrane ruffling. These functions are controlled by the GTP-bound form of Rac. The biochemical interaction between Rac and its only known GDP-dissociation stimulator (termed smgGDS) was characterized. SmgGDS was able to stimulate the incorporation of guanosine 5'-[gamma-thio]-triphosphate GTP[gamma S] into the RhoA, Rac2, Rac1, Rap1A and CDC42Hs GTP-binding proteins, but the activity was greatest toward RhoA and Rac2. Isoprenoid modification of these proteins was not absolutely required for the interaction with smgGDS. Interestingly, the activity of smgGDS toward Rac1 could not be observed in a [3H]GDP/GTP exchange assay under conditions where it stimulated incorporation of GTP[gamma S] into Rac1. We determined that smgGDS prevented the loss of Rac1 activity during the [3H]GDP/GTP exchange assay by demonstrating the ability of smgGDS to inhibit the loss of Rac1 GTP[gamma S]-binding during incubations at 30 degrees C. This stabilizing effect was exactly counterbalanced by the ability of smgGDS to stimulate the release of [3H]GDP from Rac1, thereby producing no net observable effect in the exchange assay. SmgGDS was able to effectively stimulate the release of GDP but not GTP[gamma S] from Rac1. SmgGDS maintains Rac1 in a nucleotide-free form after release of GDP, indicating that the reaction between Rac1 and smgGDS involves a substituted enzyme mechanism.

Effect of phosphorothioate modification of oligodeoxynucleotides on specific protein binding

Phosphorothioate modification of internucleoside linkages is widely used to prevent degradation of oligodeoxynucleotide (ODN) therapeutic agents in serum and cells. This modification generally increases ODN potency, but in many instances it is associated with an increase of poorly understood nonspecific effects. In this study, we have found that both cellular retention and nonspecific protein binding are dependent upon the extent of the oligonucleotide's modification. Flow cytometry of cells treated with fluorescein-labeled single-stranded (ss) or double-stranded (ds) ODNs demonstrated that fully phosphorothioate-modified ODNs exhibit much greater cellular association than 3'-terminally modified ODNs (with three 3'-terminal phosphorothioate linkages). Additionally, gel shift assays with either ss- or ds-probes showed that fully phosphorothioate-modified ODNs also exhibit much greater cytoplasmic and nuclear protein binding than either 3'-terminally modified or unmodified ODNs. However, gel shift competition assays showed that transcription factor binding by fully phosphorothioate-modified ds-ODNs was completely nonspecific relative to 3'-terminally modified and unmodified ds-ODNs. These results suggest that the benefits derived from full phosphorothioate modification of ODNs may be negated by increases of nonspecific protein binding and associated sequence-independent effects.

The complete mitochondrial DNA sequence of the horse, Equus caballus: extensive heteroplasmy of the control region

The sequence of the mitochondrial (mt) DNA of the horse (Equus caballus) was determined. The length of the sequence presented is 16,660 bp. This figure, however, is not absolute due to pronounced heteroplasmy caused by variable numbers of the motif GTGCACCT in the control region of different molecules. Boundaries of the 13 peptide-coding genes were determined by the presence of start and stop codons, and by analogy with other eutherian mtDNAs. Three genes (COIII, NADH3 and NADH4) were not terminated by a stop codon. Comparison among the peptide-coding genes of the horse and eight other mammals suggests that the boundaries of some mt genes should be redefined. The number of repeats in the control region was determined by sequencing 77 different clones (20 direct plus 57 PCR clones). The number of repeats ranged from 2 to 29. There was a pronounced overrepresentation of clones with many repeats (22-27). Very few clones had a repeat number that was close to the mean number of repeats.

Activation of neutrophils by a chemically separated but optically coupled neutrophil population undergoing respiratory burst

Neutrophils from pig blood were used as a model system to investigate the optical communication between cells. It was found that neutrophils stimulated to undergo respiratory burst can activate a second, chemically separated, but optically coupled population of neutrophils. The response of the latter was visualized as a temporary rising of their low-level chemiluminescence and an enhanced generation of superoxide radicals detected by both the reduction of ferricytochrome c and spin trapping. The results provide evidence that a long-range optical coupling of biological significance between living cells exists.

[The effect of Sindbis virus multiplication on gene expression of host cells]

Sindbis virus (SBV) infection mediated a rapid shutoff of host cellular gene expression (mRNA synthesis and protein synthesis); however the synthesis of cellular rRNA remained at the same level as the uninfected cells. Meanwhile a cellular protein P105 was shown to be enriched in the nuclear matrix. Actionmycin D treatment after virus infection resulted in an apparent reduce in the production of viral structural proteins and infectious virions. The results presented here not only demonstrated the complexity of SBV-mediated regulation of host gene expression, but also suggested SBV nonstructural protein nsP2 and capsid protein C were possibly involved in this process.

Modulation of three types of K+ currents in canine coronary artery smooth muscle cells by NS-004, or 1-(2'-hydroxy-5'-chlorophenyl)-5-trifluoromethyl-2(3H) benzimidazolone

The effects of the cardioprotective, vasorelaxant agent NS-004 [1-(2'-hydroxy-5'-chlorophenyl)-5-trifluoromethyl-2(3H) benzimidazolone] on K+ currents of freshly isolated canine coronary artery smooth muscle cells were examined using the suction pipette method. The Ca(++)-sensitive K+ current (IK, Ca) was isolated by using a holding potential of 0 mV and 5 mM ATP in the internal perfusate. The voltage-dependent delayed rectifier K+ current (IK, DR) was recorded at potentials below 20 mV in internal solution containing 5 mM ATP. The ATP-sensitive K+ current (IK, ATP) was induced by removing ATP in the pipette solution and was measured at potentials negative to -30 mV where IK, Ca and IK, DR were absent. External application of NS-004 activated IK, Ca, which, at 80 mV, was increased from 0.28 +/- 0.03 to 1.1 +/- 0.2, to 3.2 +/- 1.0, to 5.6 +/- 1.6 and to 8.5 +/- 1.6 nA, respectively, by 12.5, 25, 50 and 100 microM NS-004. Structurally related flufenamic, niflumic and mefenamic acids, at 100 microM, also enhanced IK, Ca. The order of potency for IK, Ca activation was NS-004 >> flufenamic = niflumic > mefenamic. In contrast, NS-004 blocked IK, DR, beginning at 2 microM with 50% inhibition at 22 microM. NS-004 also inhibited IK, ATP with a Ki value of 2.4 microM and a Hill coefficient of 1.3 in 0 mM intracellular ATP. These results demonstrate that NS-004 is a more potent activator of IK, Ca than the fenamates and that it is also a relatively potent blocker of IK, DR and IK, ATP in canine coronary artery smooth muscle cells.

[An approach for PCR amplification of long DNA fragments]

The polymerase chain reaction (PCR) technique, evolved as a standard laboratory technique, has a major limitation: its inability to efficiently amplify fragments higher than 1.5 kb. In this paper, PCR conditions allowing the efficient amplification of long DNA fragments, especially a new proper buffer system, have been developed. The difference between the new PCR reaction buffer system and standard reaction system is that no KCl is included in the former. The results indicated that specificity and reproducibility for amplifying long DNA fragments by using new buffer system are satisfactory.

Age estimation by Chinese permanent teeth with image analysis

A total of 567 human teeth except third molars were studied to estimate age, using a combined method of multiple regression analysis of data from a scoring system, direct measurements with image analyser, and logarithmic transformation. As a result, the standard errors of estimate were 4.8-5.4 years in the working sample, and 2.9-5.4 years in the control sample respectively, by using a single tooth. By testing the formulae on forensic autopsy cases in Guang Dong and Guang Xi, (People's Republic of China), it is demonstrated that the standard error of estimate is 3.7 and 2.6 years respectively for any single tooth (incisor, canine, premolar or molar) except the third molar. Age determination from multiple teeth of the same individual has also been studied. As a result, according to the different age grouping, the standard errors of estimate ranged from 0.8 to 2.6 years (2 teeth from the same individual) and 0.6 to 2.3 years (3 teeth from the same individual). It is concluded that the method presented here is helpful in improving the accuracy of age determination from teeth.

Genetic differences in the locomotor response to single and daily doses of phencyclidine in inbred mouse strains

Genetic differences in the locomotor stimulant effects of both single and daily administration of phencyclidine were investigated in four inbred strains of male mice A/J, C57BL/6J, C57BL/6ByJ and BALB/cByJ. Each mouse was injected i.p. once in Experiment 1, or daily for 5 or 11 days in Experiments 2, 3 and 4. Locomotor activity was assessed with an automated photoelectric system. Significant strain differences were found in the response to a single as well as repeated doses of phencyclidine. A/J mice showed the greatest initial response to phencyclidine and developed tolerance to daily phencyclidine. C57BL/6ByJ mice showed initial resistance to acute phencyclidine, but developed sensitization to daily phencyclidine. The responses of both C57BL/6J and BALB/cByJ mice to acute phencyclidine were low to moderate, and did not change significantly following daily phencyclidine. The results of this study indicate that different genetic mechanisms are involved in responses to single and daily injections of phencyclidine.

Differing structural requirements for GTPase-activating protein responsiveness and NADPH oxidase activation by Rac

The Rac GTP-binding proteins regulate the actin cytoskeleton and the superoxide-forming NADPH oxidase of phagocytic leukocytes. These functions of Rac are determined by the GTP/GDP state of the protein, which can be modulated by GTPase-activating proteins (GAPs). The interaction of Ras with both downstream signaling targets and GAPs is mediated via an "effector" domain (amino acids 30-40). We demonstrate that the effector domain of Rac2 is required for both NADPH oxidase activation and actin assembly, but that mutations in this region do not decrease the responsiveness of Rac to GAPs. In contrast, mutations of residues 12 (Gly-->Val) or 61 (Gln-->Leu) inhibit both intrinsic- and GAP-stimulated GTP hydrolysis by Rac2. A double mutation in which both the effector domain and Q61L were modified restored NADPH oxidase activation and membrane ruffling, while the equivalent effector domain and G12V double mutation did not. The Rac2 Q61L mutant had an increased "affinity" for NADPH oxidase activation and for GAP binding as compared to the wild type or G12V proteins. These experiments suggest that Rac contains at least two "effector" interaction sites, and that changes in binding interactions at one of these sites may influence the function of the other.

Defining food components as new nutrients

When obtained form a usual diet, a food component that sustains or enhances physiological functions and/or prevents diseases is a nutrient. Isoflavones, tocotrienols, and carotenoids are candidate nutrients which may be of health benefit to humans by inhibiting cancer development and reducing risk of atherosclerosis. The amounts of some of these candidate nutrients in food are known. A carotenoid data base has been developed. Isoflavone content of soy foods ranges from 0.1 mg/g (soymilk) to 2.5 mg/g (soy protein isolate). Human bioavailability studies have also been performed with these candidate nutrients. For example, in young adult females fed a single meal containing soy milk, isoflavones were cleared from urine within 24 h after feeding, with about 15-20% of the total dose accounted for in urine and feces. The two major soy isoflavones, genistein and daidzein, differ in bioavailability, with daidzein being more readily excreted in urine. Isoflavones, tocotrienols, and carotenoids meet several criteria for classification as nutrients. But after appropriate animal testing, food analyses, and availability studies have been performed, human health-protective efficacy must be proven in long-term feeding trials, in order for potential health-enhancing food components to be classified as nutrients.

Diabetes-induced changes in the Gi-modulated muscarinic receptor-adenylyl cyclase system in rat myocardium

The inhibitory guanine nucleotide binding regulatory protein (Gi)-mediated muscarinic receptor-adenylyl cyclase system was studied in myocardium from adult male Wistar rats with 10 weeks of diabetes induced by a single intravenous injection of streptozotocin (60 mg/kg). Neither the messenger ribonucleic acid level nor the amount of Gi was changed in the streptozotocin diabetic group as compared to the control group. The activity of the adenylyl cyclase stimulated by guanyliminodiphosphate was decreased by 48% in the streptozotocin diabetic group whereas stimulated activities of adenylyl cyclase by sodium fluoride and forskolin remained unchanged. The inhibition of forskolin-stimulated adenylyl cyclase activity by carbachol was more potent in membranes from the streptozotocin diabetic group than that in membranes from the control group. The competition binding curve between (3H)- quinuclidinyl benzilate and carbachol obtained from the streptozotocin diabetic group was shifted to the left as compared to the control group. These results suggest that the myocardium of streptozotocin-induced diabetic rats exhibited an increase in Gi function as demonstrated by the increased inhibition of guanyliminodiphosphate-mediated adenylyl cyclase and the superhigh affinity for carbachol of the muscarinic receptors. As there were signs, similar to those seen in clinical heart failure, in the streptozotocin diabetic group, these results demonstrate that functional alteration of Gi might underlie, at least in part, the cardiac dysfunction that is associated with diabetes.

Microprocessor-programmed infusion of theophylline rapidly attained expected steady-state level in rabbit plasma

A self-made microprocessor-programmed (two-compartmental model) infusion controller was connected with an infusion pump, which achieved an expected steady-state plasma concentration (Cpss) rapidly (5 T1(2)alpha) and maintained the level. Theophylline was selected as an example, and its pharmacokinetic parameters of rabbits, expected Cpss, body weight (wt), and infusion time (t) were input. The programmed infusion rate (Kt) was determined by the following equation: (Kt) = Cpss.K10.Vc.wt (1 + [(K21-beta)/beta]EXP(-K21t)) and the predicted value was calculated by the formula: C(t) = Cpss X [1-EXP(-alpha t)]. The needed concentration and total volume of drug were automatically shown on the screen. The drug was automatically infused after pumping, and the plasma concentration of theophylline was measured by colorimetric method. The results showed that the median absolute value of the performance error (MAVPE) was 8.3%. Although T1(2)beta of theophylline was 6.08 h, the expected Cpss was attained in only 30 min (5 T1(2)alpha) after start of infusion and then well maintained.

[Protective effect of tetramethylpyrazine on ischemic neuronal damage in the gerbil hippocampus]

The effect of tetramethylpyrazine on ischemic neuronal damage was studied in gerbil hippocampus in the terms of histopathological change and cerebral tissue lipid peroxides. Fifteen-five Mongolian gerbils were randomly assigned to one of three groups: sham-operated as control, subjected to 12 min global cerebral ischemia followed by 7 day spontaneous circulatory reperfusion, in which animals were treated with either ip. physiological saline or 60 mg/kg of tetramethylpyrazine 30 min before ischemia and daily thereafter for 7 days. The number of survival pyramidal neurons in the CA1 was counted: 263 +/- 8 (cell/mm) in the sham-operated group, 20 +/- 6 in the ischemia group, and 189 +/- 56 in the group treated with tetramethylpyrazine. Changes in lipid peroxides, expressed as malondialdehyde (MDA), was 134.5 +/- 5.0 nmol/g tissue in the sham-operated group, 193.5 +/- 5.1 in the ischemia group, and 137.6 +/- 10.8 in the group treated with tetramethylpyrazine. These results indicate that tetramethylpyrazine has a protective effect on the ischemic neuronal damage in hippocampus. Free radicals and free calcium may play an important role in pyramidal neuron necrosis in hippocampus following cerebral ischemia.

Transcriptional suppression of the human T-cell leukemia virus type I long terminal repeat occurs by an unconventional interaction of a CREB factor with the R region

To analyze regulation of the human T-cell leukemia virus type I (HTLV-I) long terminal repeat (LTR), cell lines were generated from LTR-tax x LTR-beta-galactosidase (beta-Gal) doubly transgenic mouse fibroblastic tumors. The HTLV-I LTR directs expression of both the tax and lacZ genes, and Tax up-modulates both promoters in primary cells. However, once cells were transformed by tax, beta-Gal but not tax expression was suppressed. Supertransformation of these cells with v-src suppressed both beta-Gal and tax expression. This suppression was reversed by treatment with the tyrosine kinase inhibitor herbimycin A or protein kinase A inhibitor H8. Electrophoretic mobility shift assays demonstrated augmented binding in the R but not U3 region. This binding was competitively inhibited by a high-affinity CREB oligodeoxynucleotide and super-shifted with a specific CREB antibody. Treatment of cells with the cyclic AMP analog dibutyryl cyclic AMP also transiently increased the R region binding dramatically. In vitro DNase I footprint analysis identified a protein-binding sequence in the R region which corresponded with suppression. However, this target sequence lacked a conventional CREB-binding site. A 70.5-kDa DNA-binding protein was partially purified by affinity chromatography, along with a 49-kDa protein which reacted with CREB-specific sera. These data demonstrate that HTLV-I LTR suppression is associated with CREB factor binding in the R region, probably by direct interaction with a 70.5-kDa protein, and provide a novel mechanism for maintenance of viral latency.

Transport and interaction of nitrogen oxides and NO2 with CO2-HCO3- transporters in pancreatic acini

Recently, we showed that NO2- increases gap junction (GJ) permeability and synchronizes intracellular Ca2+ concentration oscillations in pancreatic acini (Loessburg et al., J. Biol. Chem. 268: 19769-19775, 1993). NO2- is also an end product of nitric oxide (NO) production and metabolism. Because of the effect of NO2- on GJ permeability and the possible importance of NO2- in NO metabolism and cytotoxicity, we used pancreatic acinar cells and intracellular pH (pHi) measurements to study the interaction of nitrogen oxides and NO2- with cellular proteins. Exposing cells to NO2- resulted in a concentration-dependent cytosolic acidification. The acidification did not require the transport of NO2- and was not mediated by diffusion of HNO2. Because the acidification was prevented by CO2-HCO3- and inhibition of carbonic anhydrase, it is possible that other nitrogen oxides present in a solution containing NO2- enter the cells by diffusion and interact with OH- or H2O to stably acidify the cytosol. NO2- itself is shown to be transported by the HCO3- transporters present in the plasma membrane. Thus manipulation of the cellular Cl- gradient and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) were used to show Cl-/NO2- exchange, whereas stimulation of external Na(+)-dependent amiloride-insensitive and DIDS-sensitive pHi increase in acidified cells was used to demonstrate a Na(+)-(NO2-)n cotransport. Hence NO2- can be a convenient substitute for HCO3- when studying HCO3- transport in an open system. The studies also show that cellular levels of nitrogen oxides and NO2- can be modulated by the cellular HCO3(-)-buffering system.(ABSTRACT TRUNCATED AT 250 WORDS)

Asymmetric cross-sensitization to the locomotor stimulant effects of phencyclidine and MK-801

Chronic administration of a psychomotor stimulant has been shown to produce progressively enhanced effects, a phenomenon called "reverse tolerance" or sensitization. Sensitization which develops to the psychomotor stimulant effect of a drug generalizes to drugs with similar neurochemical mechanisms of action, a phenomenon called cross-sensitization. The present study compared the psychomotor stimulant effects of phencyclidine and MK-801, examined the effects of the daily injection of phencyclidine and MK-801 on locomotor activity and investigated whether reciprocal cross-sensitization occurred between phencyclidine and MK-801. Adult female Sprague-Dawley rats were used. Their locomotor activity was measured automatically for a 2 h period following drug injection. Phencyclidine and MK-801 both increased locomotor activity. Four daily injections of phencyclidine in a dose of 3.2 mg/kg i.p., or MK-801 in a dose of 0.32 mg/kg i.p., produced sensitization to locomotor activity. Moreover, MK-801 sensitized rats showed cross-sensitization to phencyclidine. However, phencyclidine sensitized rats did not show cross-sensitization to MK-801. This finding suggests that there are significant differences in the neurochemical mechanisms underlying phencyclidine-induced and MK-801-induced sensitization. Phencyclidine sensitization may not be mediated by NMDA receptors.

Comparison of effects of margarite extract and recombinant human superoxide dismutase on paraquat-induced superoxide anion radicals in rat lung

The effects of medicinal margarite extract and recombinant human superoxide dismutase (r-h SOD) on acute paraquat intoxication were examined in the rat lung. Forty-eight Sprague-Dawley rats under pentobarbital anesthesia were randomly assigned to one of four groups receiving i.v. injection of physiological saline (control), i.v. injection of 70 mg/kg paraquat, or i.v. injection of either 50 mg/kg of margarite extract or 50,000 unit/kg of r-h SOD 10 minutes before and 1 and 2 hours after an equivalent paraquat administration. Examination of lung superoxide anion radicals (O2-.), lipid peroxides, and histopathological changes showed that paraquat significantly increased superoxide anion radicals (383% of control) reacted with CLA-phenyl. Both margarite extract and r-h SOD decreased superoxide anion radicals to 119% and 83% of control, respectively. Margarite extract, rather than r-h SOD, significantly alleviated the paraquat-induced infiltration of polymorphonuclear leukocytes and macrophages into the alveolar walls. There were no significant inter-group differences in lipid peroxides in the lung. Component analysis showed that margarite extract was rich in L- and D-arginine. The scavenging mechanism of margarite extract may be related to L-arginine but needs to be further verified in the future study.

Role of EDRF/NO in parasympathetic coronary vasodilation following carotid chemoreflex activation in conscious dogs

The role of endothelium-derived relaxing factor (EDRF) in parasympathetic coronary vasodilation following carotid chemoreflex activation induced by nicotine in conscious dogs and stimulation of the vagus nerve in anesthetized dogs was studied. Injection of nicotine (11 +/- 4 micrograms) into the carotid artery increased coronary blood flow (CBF) by 126 +/- 16% from 28 +/- 3 ml/min and reduced late diastolic coronary resistance (LDCR) by 43 +/- 4% from 3.58 +/- 0.52 mmHg.ml-1.min, accompanied by a significant increase in mean arterial pressure and a decrease in heart rate (all P < 0.01). Pacing and propranolol did not change the coronary vascular response to chemoreflex activation. There were still increases in CBF by 113 +/- 17% from 29 +/- 3 ml/min and decreases in LDCR by 41 +/- 5% from 3.13 +/- 0.52 mmHg.ml-1.min (all P < 0.01). After infusion of N omega-nitro-L-arginine (L-NNA) (30 mg/kg), the increase in CBF following chemoreflex activation was only 23 +/- 3% from 37 +/- 3 ml/min, and the fall in LDCR was 19 +/- 3% from 3.09 +/- 0.51 mmHg.ml-1.min. Stimulation of the vagus nerve showed a relationship between stimulation frequency and coronary vasodilation that was significantly inhibited by L-NNA. Thus EDRF plays an important role in mediating parasympathetic coronary vasodilation during chemoreflex activation and perhaps during many reflexes that cause vagal cholinergic vasodilation in the heart.

Filling in of Fraunhofer lines in the ocean by Brillouin scattering

We have investigated the relative contribution of Brillouin scattering to the filling in of both narrow and wide Fraunhofer lines in the ocean. The spectral behavior of the filling in was studied in two ways. First we studied Fraunhofer lines of variable width, such as the 455-nm Ba line with full-width at half-maximum (FWHM) = 0.02 nm, the 486-nm H(β) line (FWHM = 0.08 nm), and the 518-nm Mg line (FWHM = 0.11 nm). We then used the 455-nm Ba line as a narrow-line model to calculate the spectral dependence of the filling in. We found that Brillouin scattering can play a significant role in the filling in of narrow Fraunhofer lines in the ocean. We have also shown that, compared with the filling in caused by Raman scattering, the filling in caused by Brillouin scattering has less dependence on both the wavelength and ocean depth but is strongly dependent on the linewidth of the Fraunhofer line.

Role of EDRF in the regulation of regional blood flow and vascular resistance at rest and during exercise in conscious dogs

The contribution of endothelium-derived relaxing factor (EDRF) to the regulation of regional vascular resistance and tissue blood flow at rest and during acute moderate exercise was studied in chronically instrumented conscious dogs. Radioactive microspheres were injected before and during exercise to measure regional blood flow. An infusion of nitro-L-arginine (L-NA), an analogue of L-arginine, was used to inhibit the synthesis of EDRF and resulted in a significant increase in mean arterial pressure, associated with significantly elevated vascular resistance in heart, skeletal muscle, renal and splanchnic circulations and with decreases in tissue blood flow in those regions at rest. Acute exercise caused a typical redistribution of blood flow, in which there was vasodilation in heart and working skeletal muscles, accompanied by vasoconstriction in kidney and splanchnic circulations. L-NA resulted in significantly elevated vascular resistance during vasodilation in heart and working skeletal muscles and also significantly increased vasoconstriction in renal cortex, stomach, pancreas, liver, and colon during exercise. Blood flows during exercise were largely unaffected by L-NA treatment. Our results suggest that whereas EDRF functions to regulate basal vascular tone and vascular resistance during exercise, EDRF has a minor role in determining the pattern of the redistribution of tissue blood flow during exercise.

Gi-mediated muscarinic adenylyl cyclase inhibition in timolol-treated stunned porcine myocardium

The Gi-mediated muscarinic receptor-adenylyl cyclase system was examined in stunned myocardium induced by either three or five brief ischaemic periods after beta-adrenoceptor blockade by timolol (0.1 mg kg-1). The mid-left anterior descending coronary artery was occluded for 2, 10 and 2 min in four pigs, and for 2, 2, 5, 10 and 2 min in four other pigs. All the ischaemic periods were separated by 30 min of reperfusion and the biopsies were obtained 60 min after the last ischaemic period. Segment length function was measured in the ischaemic region and in the control region supplied by the left circumflex artery. In the two groups, the percentage systolic shortening was reduced equally, to 59 +/- 9 and 58 +/- 10% of control in the region subjected to ischaemia and only minimally in the control region. The biopsies from the stunned region from both groups showed: (1) no change in either the affinity for carbachol or the number of binding sites of the muscarinic receptors; (2) no alterations in messenger RNA encoding for the alpha subunit-2 of the inhibitory guanine nucleotide binding protein, as demonstrated by northern blot and solution hybridization; (3) no change in membrane-bound inhibitory guanine nucleotide binding protein, as shown by enzyme immunoassay utilizing a specific anti-peptide antibody, and (4) unchanged inhibition of stimulated adenylyl cyclase activity. These results suggest that there is an intact inhibitory guanine nucleotide binding protein-mediated muscarinic receptor adenylyl cyclase system in the stunned porcine myocardium.

Air pollution and daily mortality in residential areas of Beijing, China

The relationship between air pollution and daily mortality in 1989 was examined in two residential areas in Beijing, China. Very high concentrations of sulfur dioxide (SO2) (mean = 102 micrograms/m3, maximum = 630 micrograms/m3) and total suspended particulates (TSPs) (mean = 375 micrograms/m3, maximum = 1,003 micrograms/m3) were observed in these areas. Daily counts of deaths were regressed, using Poisson regression on the logarithm of (SO2) and/or TSPs controlling for effects of temperature, humidity, and day of week. A highly significant association was found between In(SO2) and daily mortality. The risk of total mortality was estimated to increase by 11% (95% confidence interval [95% CI] = 5%-16%) with each doubling in SO2 concentration. Separately, the association of In(TSP) with total daily mortality was positive but not significant (4% increase in mortality with each doubling in TSP; 95% CI = -2%-11%). When mortality was analyzed separately by cause, the association with a doubling in SO2 was significant for chronic obstructive pulmonary disease (29%), pulmonary heart disease (19%), and cardiovascular disease (11%), and marginally significant for the other nonmalignant causes (8%), but not statistically significant for cancer (2%). A similar association was noted for a doubling in TSP (4%, 38%, and 8% for total, chronic obstructive pulmonary disease, and pulmonary heart disease mortality, respectively), but the result was only statistically significant for chronic obstructive pulmonary disease. In the season-specific analysis, both SO2 and TSP were found to be significant predictors of total daily mortality in summer. In winter, SO2 was again significantly associated with increased mortality, but no positive association was found between TSP and mortality.(ABSTRACT TRUNCATED AT 250 WORDS)