Leptin levels in human and rodent: measurement of plasma leptin and ob RNA in obese and weight-reduced subjects

Leptin, the gene product of the obese gene, may play an important role in regulating body weight by signalling the size of the adipose tissue mass. Plasma leptin was found to be highly correlated with body mass index (BMI) in rodents and in 87 lean and obese humans. In humans, there was variability in plasma leptin at each BMI suggesting that there are differences in its secretion rate from fat. Weight loss due to food restriction was associated with a decrease in plasma leptin in samples from mice and obese humans.

Anatomic localization of alternatively spliced leptin receptors (Ob-R) in mouse brain and other tissues

Leptin's effects are mediated by interactions with a receptor that is alternatively spliced, resulting in at least five different murine forms: Ob-Ra, Ob-Rb, Ob-Rc, Ob-Rd, and Ob-Re. A mutation in one splice form, Ob-Rb, results in obesity in mice. Northern blots, RNase protection assays, and PCR indicate that Ob-Rb is expressed at a relatively high level in hypothalamus and low level in several other tissues. Ob-Ra is expressed ubiquitously, whereas Ob-Rc, -Rd, and -Re RNAs are only detectable using PCR. In hypothalamus, Ob-Rb is present in the arcuate, ventromedial, dorsomedial, and lateral hypothalamic nuclei but is not detectable in other brain regions. These nuclei are known to regulate food intake and body weight. The level of Ob-Rb in hypothalamus is reduced in mice rendered obese by gold thioglucose (GTG), which causes hypothalamic lesions. The obesity in GTG-treated mice is likely to be caused by ablation of Ob-Rb-expressing neurons, which results in leptin resistance.

Increased expression in adipocytes of ob RNA in mice with lesions of the hypothalamus and with mutations at the db locus

The gene product of the recently cloned mouse obese gene (ob) is important in regulating adipose tissue mass. ob RNA is expressed specifically by mouse adipocytes in vivo in each of several different fat cell depots, including brown fat. ob RNA is also expressed in cultured 3T3-442A preadipocyte cells that have been induced to differentiate. Mice with lesions of the hypothalamus, as well as mice mutant at the db locus, express a 20-fold higher level of ob RNA in adipose tissue. These data suggest that both the db gene and the hypothalamus are downstream of the ob gene in the pathway that regulates adipose tissue mass and are consistent with previous experiments suggesting that the db locus encodes the ob receptor. In db/db and lesioned mice, quantitative differences in expression level of ob RNA correlated with adipocyte lipid content. The molecules that regulate expression level of the ob gene in adipocytes probably are important in determining body weight, as are the molecules that mediate the effects of ob at its site of action.

Evaluation of vetiver oil and seven insect-active essential oils against the Formosan subterranean termite

Repellency and toxicity of 8 essential oils (vetiver grass, cassia leaf, clove bud, cedarwood, Eucalyptus globules, Eucalyptus citrodora, lemongrass and geranium) were evaluated against the Formosan subterranean termite, Coptotermes formosanus Shiraki. Vetiver oil proved the most effective repellent because of its long-lasting activity. Clove bud was the most toxic, killing 100% of termites in 2 days at 50 micrograms/cm2. The tunneling response of termites to vetiver oil also was examined. Vetiver oil decreased termite tunneling activity at concentrations as low as 5 micrograms/g sand. Tunneling and paper consumption were not observed when vetiver oil concentrations were higher than 25 micrograms/g sand. Bioactivity of the 8 oils against termites and chemical volatility were inversely associated. Listed in decreasing order of volatility, the major constituents of the 8 oils were: eucalyptol, citronellal, citral, citronellol, cinnamaldehyde, eugenol, thujopsene, and both alpha- and beta-vetivone. Vetivor oil is a promising novel termiticide with reduced environmental impact for use against subterranean termites.

A scaffold laden with mesenchymal stem cell-derived exosomes for promoting endometrium regeneration and fertility restoration through macrophage immunomodulation

Endometrial traumas may cause intrauterine adhesions (IUAs), leading to infertility. Conventional methods in clinic have not solved the problem of endometrial regeneration in severe cases. Umbilical cord-derived mesenchymal stem cell (UC-MSC)-based therapies have shown some promising achievements in the treatment of IUAs. However, the limitations of potential tumorigenicity, low infusion and low retention are still controversial and restricted the clinical application of MSCs. In contrast, UC-MSC-derived exosomes exhibit a similar function to their source cells and are expected to overcome these limitations. Therefore, a novel and viable cell-free therapeutic strategy by UC-MSC-derived exosomes was proposed in this study. Here, we designed a construct of exosomes and collagen scaffold (CS/Exos) for endometrial regeneration in a rat endometrium-damage model, and investigated the regeneration mechanism through macrophage immunomodulation. The CS/Exos transplantation potently induced (i) endometrium regeneration, (ii) collagen remodeling, (iii) increased the expression of the estrogen receptor α/progesterone receptor, and (iv) restored fertility. Mechanistically, CS/Exos facilitated CD163⁺ M2 macrophage polarization, reduced inflammation, and increased anti-inflammatory responses in vivo and in vitro. By RNA-seq, miRNAs enriched in exosomes were the main mediator for exosomes-induced macrophage polarization. Overall, we demonstrated that CS/Exos treatment facilitated endometrium regeneration and fertility restoration by immunomodulatory functions of miRNAs. Our research highlights the therapeutic prospects of CS/Exos for the management of IUAs. STATEMENT OF SIGNIFICANCE: Severe endometrial traumas always result in intrauterine adhesions (IUAs) and infertility. The limited outcomes by conventional methods in the clinic make it very important to develop new strategies for endometrium regeneration and fertility restoration. In this study, an exosome-laden scaffold (CS/Exos) was designed and the transplantation of CS/Exos potently induced (i) endometrium regeneration, (ii) collagen remodeling, (iii) increased the expression of the estrogen receptor α/progesterone receptor, and (iv) restored fertility. In mechanism, the construct of CS/Exos facilitated M2 macrophage polarization, reduced inflammation, and increased anti-inflammatory responses. Furthermore, miRNAs enriched in exosomes were the main mediator for exosome-induced macrophage polarization. This study highlights the therapeutic prospects of CS/Exos and the translational application for the management of severe IUAs.

Regulation of endothelial cell tissue factor expression by minimally oxidized LDL and lipopolysaccharide

Tissue factor (TF) is the predominant physiological initiator of coagulation, and its regulation is a critical aspect of endothelial cell hemostatic function. This report describes the regulation of TF mRNA expression by two physiological agonists: minimally oxidized low-density lipoprotein (MM-LDL), which may modulate endothelial hemostatic function in atherosclerosis, and lipopolysaccharide (LPS), which is a mediator of septic shock. Northern blot analysis of total RNA from human endothelial cells exposed to either MM-LDL or LPS for varying times showed that TF mRNA increased sharply at 1 hour, peaked at 2 to 3 hours, and declined to basal levels by 6 to 8 hours after treatment. The half-life of TF mRNA in MM-LDL- and LPS-exposed endothelial cells was approximately 45 minutes and 40 minutes, respectively. The rate of TF mRNA degradation was similar at 1 and 4 hours after exposure in either MM-LDL- or LPS-stimulated endothelial cells. Nuclear runoff transcription assays showed a significantly increased rate of TF gene transcription in both MM-LDL- and LPS-exposed endothelial cells. Cycloheximide inhibited the induction of TF protein activity, but it enhanced the accumulation of TF mRNA in MM-LDL- and LPS-induced endothelial cells. These results indicated that regulation of TF expression by MM-LDL and LPS in human endothelial cells occurs principally at the level of gene transcription.

IL-1beta caused pancreatic beta-cells apoptosis is mediated in part by endoplasmic reticulum stress via the induction of endoplasmic reticulum Ca2+ release through the c-Jun N-terminal kinase pathway

Endoplasmic reticulum (ER) homeostasis is crucial for beta-cell function and survival. Direct as well as indirect evidence has pointed toward Ca(2+) as an important determinant of interleukin-1beta (IL-1beta)-induced beta-cell dysfunction and apoptosis. In the present study, we show that IL-1beta-induced apoptosis and necrosis in primary rat beta-cells and MIN6 cells largely depends on ER stress, ER Ca(2+) release, and c-Jun N-terminal kinase (JNK) activation. beta-cells also showed marked sensitivity to apoptosis induced by sarcoendoplasmic reticulum Ca(2+) ATPase (SERCA) blockers, thapsigargin and cyclopiazonic acid (CPA). IL-1beta induced ER Ca(2+) release, which was paralleled by an IL-1beta-dependent induction of JNK activation and the ER stress response, including activation of PRK (RNA-dependent protein kinase)-like ER kinase (PERK). Furthermore, reduced activation of JNK, utilizing JNK inhibitor SP600125, resulted in significant protection from IL-1beta- or thapsigargin-induced apoptosis via ER stress. In conclusion, our results suggest that the IL-1beta-induced depletion of ER Ca(2+) and activation of the ER stress via JNK pathway are potential contributory mechanisms to beta-cell death.

Molecular characterization of a new excitatory insect neurotoxin with an analgesic effect on mice from the scorpion Buthus martensi Karsch

Besides the neurotoxins active on mammals, a new excitatory insect selective toxin with a mice analgesic activity was found and purified from the venom of the scorpion Buthus martensi Karsch (BmK) (Ji, Y.H., Mansuelle, P., Terakawa, S., Kopeyan, C., Yanaihara, N., Hsu, K., Rochat, H., 1996. Toxicon 34, 987; Luo, M.J., Xiong, Y.M., Wang, M., Wang, D.C., Chi, C.W., 1997. Toxicon 35, 723.). This peptide (designated as BmK IT-AP) is composed of 72 amino acid residues. Its primary structure was determined by automated Edman degradation of the N-terminal part of the reduced and S-carboxamidemethylated protein and its lysylendopeptidase degraded fragments. Based on the determined sequence, the gene specific primers were designed and synthesized for 3' and 5' RACE (rapid amplification of cDNA ends). Their partial cDNA fragments obtained by 3' and 5' RACEwere cloned and sequenced and the full length cDNA sequence of BmK IT-AP was then completed by overlapping their two partial cDNA sequences. It encodes a precursor of 90 amino acid residues: a signal peptide of 18 residues and a mature peptide of 72 residues which are consistent with the determined protein sequence of BmK IT-AP. The genomic DNA of the peptide was also amplified by PCR from the scorpion genomic DNA and sequenced, which is a first report on the genomic structure of a scorpion toxin specific for insects. Its sequence revealed an intron of 590 bp inserted in the end part of the signal peptide. The peptide caused a fast excitatory contraction paralysis on house fly larvae. Furthermore, the peptide also showed an obvious analgesic effect on mice, as assayed by using a twisting test model. This effect of BmK IT-AP well characterized at molecular level is first reported among the known scorpion insect neurotoxins.

Developmental control of promoter-specific factors responsible for the embryonic activation and inactivation of the sea urchin early histone H3 gene

We have begun an investigation of the molecular basis for the temporal embryonic expression of the early histone H3 gene of the sea urchin Strongylocentrotus purpuratus. Cloned constructs exhibit the proper temporal regulation following microinjection into one-cell zygotes of the related sea urchin species, Lytechinus pictus. Deletion analysis of the upstream promoter region of the H3 gene revealed several regions that are involved in both positive and negative control. DNase I footprinting, mobility shift, and methylation interference experiments reveal multiple sequence-specific DNA-binding proteins that interact with at least five distinct regions within 200 bp upstream of the RNA initiation site. Extracts prepared from staged embryos revealed that the ability of the factors to bind their target sequences was regulated. Proteins bound at four different sites were detected only at stages when the H3 gene was active transcriptionally. In addition, three different forms of a CCAAT-binding protein also are regulated temporally. The activity of these protein(s), however, correlates inversely with the transcriptional activity of the gene. The TATA box and CCAAT sequences are all that is required for expression of low levels of H3 transcripts with the proper temporal pattern. This approach should be useful in understanding the mechanisms used to regulate temporal patterns of gene expression during early embryogenesis.

Hormone Replacement Therapy Reverses Gut Microbiome and Serum Metabolome Alterations in Premature Ovarian Insufficiency

OBJECTIVE

We explored the gut microbiome and serum metabolome alterations in patients with premature ovarian insufficiency (POI) and the effects of hormone replacement therapy (HRT) with the aim to unravel the pathological mechanism underlying POI.

METHODS

Fecal and serum samples obtained from healthy females (HC, n = 10) and patients with POI treated with (n = 10) or without (n = 10) HRT were analyzed using 16S rRNA gene sequencing and untargeted metabolomics analysis, respectively. Peripheral blood samples were collected to detect serum hormone and cytokine levels. Spearman's rank correlation was used to evaluate correlations between sex hormones and cytokines and between the gut microbiota and serum metabolites. To further confirm the correlation between Eggerthella and ovarian fibrosis, the mice were inoculated with Eggerthella lenta (E. lenta) through oral gavage.

RESULTS

The abundance of genus Eggerthella significantly increased in the fecal samples of patients with POI compared to that observed in the samples of HCs. This increase was reversed in patients with POI treated with HRT. Patients with POI showed significantly altered serum metabolic signatures and increased serum TGF-β1 levels; this increase was reversed by HRT. The abundance of Eggerthella was positively correlated with altered metabolic signatures, which were, in turn, positively correlated with serum TGF-β1 levels in all subjects. Estrogen ameliorated ovarian fibrosis induced by E. lenta in mice.

CONCLUSIONS

The interactions between the gut microbiota, serum metabolites, and serum TGF-β1 in patients with POI may play a critical role in the development of POI. HRT not only closely mimicked normal ovarian hormone production in patients with POI but also attenuated gut microbiota dysbiosis and imbalance in the levels of serum metabolites and TGF-β1, which are reportedly associated with fibrosis. The findings of this study may pave the way for the development of preventive and curative therapies for patients with POI.

Trophoblast-Derived Extracellular Vesicles Promote Preeclampsia by Regulating Macrophage Polarization

BACKGROUND

Systemic inflammation caused by dysfunctional macrophages is a crucial pathogenetic event in preeclampsia (PE). Trophoblast-derived extracellular vesicles (T-EVs) are potent immune cell signaling modulators in pregnancy. Herein, we aimed to investigate T-EVs' effect and mechanism on macrophage polarization and its role in PE pathogenesis, which remain unclear.

METHODS

Flow cytometry and immunochemistry were used to determine placental macrophage phenotypes. T-EVs were immuno-isolated via placental alkaline phosphatase antibody and identified by transmission electron microscopy and nanoparticle tracking analysis. Quantitative real-time polymerase chain reaction and flow cytometry were used to examine the effects of T-EVs on macrophage polarization, and correlation analysis of T-EVs lipidomics and macrophages transcriptome were performed to explore how T-EVs modulate macrophages. Animal experiments were established to investigate the relationship among PE, T-EVs, and macrophages.

RESULTS

Macrophages shift from the M2 to M1 phenotype in the preeclamptic placenta. Also, T-EVs from women with PE (PE-EVs) significantly upregulated M1 gene markers and significantly downregulated CD163 expression in macrophages compared with T-EVs in women with normal pregnancies (NP-EVs). Mechanistically, correlation analysis with T-EVs lipidome and the transcriptome of macrophages treated with PE-EVs or NP-EVs indicated that 37 lipids altered in PE-EVs considerably affected classical inflammatory biological pathways in macrophages. Finally, animal experiments revealed that PE-EVs triggered PE-like symptoms in pregnant mice, which were alleviated after macrophage depletion.

CONCLUSIONS

T-EVs from women with PE could promote preeclampsia by inducing macrophage imbalance polarization, signifying a potential novel interventional target for the prevention and management of PE.

Assessing the excitable gap in reentry by resetting. Implications for tachycardia termination by premature stimuli and antiarrhythmic drugs

BACKGROUND

The shortest excitable gap during reentry may determine responses to pacing and antiarrhythmic drugs. The resetting response has been used clinically to assess the excitable gap, but it cannot directly indicate the shortest excitable gap.

METHODS AND RESULTS

We studied resetting in the in vitro canine atrial tricuspid ring using an adjustable reentry preparation in which the ring was cut and reconnected electronically with an adjustable delay to vary the cycle length and excitable gap. We reset the tachycardias using 31 delays in 12 experiments. Tachycardias were terminated by premature stimuli in 16 delays. The reset window overestimated the shortest excitable gap by 25 +/- 14 ms, and the maximum degree of advancement of tachycardia underestimated the shortest excitable gap by 22 +/- 11 ms. The slope of the increasing portion of the resetting response curve was steeper in tachycardias terminated by premature stimuli than in those not terminated (-0.69 +/- 0.2 versus -0.37 +/- 0.2, P < .01). The effective refractory period difference between the sites of pacing and of block correlated with the slope of the resetting response curve. Damped cycle length oscillation after a long return cycle during resetting was always present when there was a partially excitable gap.

CONCLUSIONS

The reset window during pacing within the circuit and the maximum degree of advancement provided equally good estimates bracketing the shortest excitable gap. The slope of the resetting response curve predicted the likelihood of termination by premature stimuli. Damped cycle length oscillation after resetting detected a partially excitable gap.

Reversal of reentry and acceleration due to double-wave reentry: two mechanisms for failure to terminate tachycardias by rapid pacing

OBJECTIVES

We sought to demonstrate mechanisms by which rapid pacing can cause conduction block without terminating reentry.

BACKGROUND

Rapid pacing can fail to terminate or can accelerate tachycardias in patients. Mechanisms for these responses are poorly understood.

METHODS

We studied reentry in the canine atrial tricuspid ring and a left ventricular ring in vitro in 12 preparations. Activations were recorded from 10 sites around the ring, and monophasic action potentials were recorded from critical sites of block. Rapid pacing at cycle lengths that intermittently caused conduction block was performed at multiple sites.

RESULTS

Action potential alternans contributed to block of an orthodromic impulse during rapid pacing. When pacing continued for two stimuli after orthodromic block, a second episode of block could reverse the direction of tachycardia. Continued pacing at this site was likely to produce block of an antidromic impulse, which may initiate double-wave reentry. Double-wave reentry could be sustained or nonsustained. Its cycle length was 56% to 77% of the single-wave cycle length. The ratio of double-wave cycle length to single-wave cycle length was inversely correlated with the relative excitable gap (p < 0.01). Double-wave reentry can be a mechanism for persistent cycle length alternation during tachycardia.

CONCLUSIONS

Successful termination of reentry by rapid pacing required block of an othrodromic impulse and stopping pacing within one stimulus after orthodromic block. Reversal of reentry makes the circuit resistant to termination from this site of pacing. Antidromic block can cause acceleration due to double-wave reentry when there is a substantial excitable gap.

Met-enkephalin-Arg6-Phe7-like immunoreactive substances mediate electroacupuncture analgesia in the periaqueductal gray of the rabbit

The present study was undertaken to investigate whether the C-terminal extended Met-enkephalin heptapeptide (Met-enkephalin-Arg6-Phe7, MEAP) played a role in mediating the analgesic effect of electroacupuncture in rabbits. MEAP and its degrading enzyme inhibitor captopril as well as antiserum against MEAP were injected into the periaqueductal gray (PAG) via a previously implanted cannula. Their effects on nociception were tested by the escape response latency (ERL) elicited by radiant heat applied on the skin of the snout. (1) Microinjection of MEAP (30-240 nmol) into PAG produced a dose-dependent analgesic effect which was 2.5 times more potent than Met-enkephalin (MEK) and 3 times less potent than morphine. The complete reversal of the analgesia elicited by 240 nmol of MEAP by a small dose of naloxone (0.1 mg/kg, i.v.) indicates that the effect of MEAP is mediated by naloxone sensitive opioid receptors. (2) In rabbits, a dose-dependent analgesia was elicited by an intra-PAG injection of captopril (60-240 nmol). A single dose of 240 nmol captopril increased ERL by more than 100%. This effect could be reversed by 30 nmol of naloxone injected into the same site, or by antiserum recognizing MEAP (1 microliter, titer 1:1500) but not by antiserum recognizing MEK (1 microliter, 1:8000) suggesting that captopril was able to protect MEAP from degradation. (3) Intra-PAG injection of 60 nmol of captopril significantly potentiated the after effect of electroacupuncture (EA) induced analgesia. This effect could be blocked either by 30 nmol (but not 7.5 nmol) of naloxone, or by 1 microliter (but not 0.1 microliter) of MEAP antiserum.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization and localization of atriopeptin in rat atrium

An antiserum specific for atriopeptin was used to characterize and localize atriopeptin-like immunoreactive material in rat atrium by radioimmunoassay and immunohistochemical techniques. The antiserum recognizes atriopeptin I, atriopeptin III, and alpha-human atrial natriuretic polypeptide, but does not recognize met-enkephalin, cholecystokinin, dynorphin A, bradykinin, substance P, or beta-endorphin. A high content of atriopeptin was found in crude extracts of rat atria, as compared to ventricles, and the atriopeptin-like immunoreactive material was found to be located exclusively in granules within atrial cardiocytes. Fractionation of the immunoreactive material by gel filtration and reverse-phase HPLC revealed the presence of multiple atriopeptins.

Extracellular Vesicle-Mediated Secretion of HLA-E by Trophoblasts Maintains Pregnancy by Regulating the Metabolism of Decidual NK Cells

Extracellular vesicles derived from trophoblasts (T-EVs) play an important role in pregnancy, but the mechanism is not entirely clear. In this study, we found that HLA-E, which is mostly confined to the cytoplasm of trophoblast cells, was secreted by T-EVs. The level of HLA-E in T-EVs from unexplained recurrent spontaneous abortion (URSA) patients was lower than that in normal pregnancy (NP) and RSA patients who had an abnormal embryo karyotype (AK-RSA). T-EVs promoted secretion of IFN-γ and VEGFα by decidual NK (dNK) cells from URSA patients via HLA-E, VEGFα was necessary for angiogenesis and trophoblast growth, and IFN-γ inhibited Th17 induction. Glycolysis and oxidative phosphorylation (OxPhos) were involved in this process. Glycolysis but not OxPhos of dNK cells facilitated by T-EVs was dependent on mTORC1 activation. Inhibition of T-EV production in vivo increased the susceptibility of mice to embryo absorption, which was reversed by transferring exogenous T-EVs. T-EVs promoted secretion of IFN-γ and VEGFα by dNK cells to maintain pregnancy via Qa-1 in abortion-prone mouse models. This study reveals a new mechanism of pregnancy maintenance mediated by HLA-E via T-EVs.

Temporal embryonic expression of the sea urchin early H1 gene is controlled by sequences immediately upstream and downstream of the TATA element

The sea urchin early histone H1 gene is expressed only during a very short interval in the life cycle of the organism. In addition to a pool of stored maternal transcripts, the gene is active from the 16-cell stage to the early blastula stage of development, at which time the gene is transcriptionally repressed. We have defined the minimal sequences required for the proper temporal expression of this gene during early embryogenesis. These sequences from -65 to +39 include the TATA element, a conserved sequence CCCACGTACGCAA (part of USE 0) just upstream of the TATA element, an Inr element at the transcription start site, and an internal sequence in the leader region of the H1 transcript. Surprisingly, we could find no role for two highly conserved elements, a GC box (USE I) and an H1-specific element (USE II), that are important in the expression of vertebrate H1 genes. The internal element functions as a positive regulator when three copies are ectopically placed upstream of an early histone H3 TATA box. A temporal regulator is localized within the USE 0 sequence CCCACGTACGCAA, and it apparently plays a role in activation and probably repression of the gene.

Termination of reentry by lidocaine in the tricuspid ring in vitro. Role of cycle-length oscillation, fast use-dependent kinetics, and fixed block

We hypothesized that drugs with rapid recovery kinetics from use-dependent sodium channel block could promote oscillatory termination of reentry by enhancing interval-dependent conduction. Mechanisms of termination were related to properties of the reentrant circuit. Nine adjustable reentrant preparations were used in which the canine atrial tricuspid ring was cut and then reconnected electronically by sensing activation on one side of the cut and pacing the other after an adjustable delay. The cycle length and diastolic interval during reentry were manipulated by changing this delay. Lidocaine (1.28 x 10(-5) mol/L) significantly increased refractoriness (94 +/- 39 ms) and the slope of the conduction curve (-0.12 +/- 0.07) at the site of block during pacing. Lidocaine terminated sustained reentry by two mechanisms. Early termination resulted from increased cycle length oscillation and refractoriness (reproducible in each experiment) but only at short delays with short initial diastolic intervals. The range of delays showing this mechanism of termination was 100 +/- 48 ms. Increased cycle-length oscillation resulted from an increased slope of the conduction curve. In eight experiments, lidocaine terminated reentry by causing fixed block after 50 minutes of drug superfusion, which prevented reentry at all delays. Fixed block occurred at one of two vulnerable sites and was transiently reversed by acetylcholine. Termination due to refractory block occurred only when the initial diastolic interval was short, and termination due to fixed block developed when there was a susceptible region with a low safety factor for propagation. Fast recovery from sodium channel block promotes oscillatory termination by increasing the slope of the conduction curve.

Formulation and pharmacokinetic studies of acyclovir controlled-release capsules

Acyclovir controlled-release capsules (CRCs) were prepared by a three-step process: (1) melt granulation of acclovir; (2) coating of granules with ethyl-cellulose, (3) incorporation of coated granules into hard gelatin capsules. In vitro release experiments showed that the main factors affecting the release rate were the mean particle size of the actylovir raw material and the amount of coating material applied. Release of acyclovir from the capsules was in accordance with the Higuchi equation. Pharmacokinetic studies in dogs after oral administration of acyclovir controlled-release capsules showed that the formulation was successful in providing slow release of aciclovir and was superior to a commercially available controlled-release formulation.

Characterization of core-shell MOF particles by depth profiling experiments using on-line single particle mass spectrometry

Materials with core-shell structures have distinct properties that lend themselves to a variety of potential applications. Characterization of small particle core-shell materials presents a unique analytical challenge. Herein, single particles of solid-state materials with core-shell structures were measured using on-line aerosol time-of-flight mass spectrometry (ATOFMS). Laser 'depth profiling' experiments verified the core-shell nature of two known core-shell particle configurations (<2 μm diameter) that possessed inverted, complimentary core-shell compositions (ZrO2@SiO2 versus SiO2@ZrO2). The average peak area ratios of Si and Zr ions were calculated to definitively show their core-shell composition. These ratio curves acted as a calibrant for an uncharacterized sample – a metal-organic framework (MOF) material surround by silica (UiO-66(Zr)@SiO2; UiO = University of Oslo). ATOFMS depth profiling was used to show that these particles did indeed exhibit a core-shell architecture. The results presented here show that ATOFMS can provide unique insights into core-shell solid-state materials with particle diameters between 0.2-3 μm.

Polymorphisms within the HLA-DRw6 haplotype. III. DQ alpha and DQ beta polymorphism associated with HLA-D

We have studied HLA-DQ encoded antigens from HLA-DRw6 homozygous cells and analyzed the DQ region at the DNA level. HLA-DQ molecules were isolated from EBV transformed B-cell lines and analyzed for DQ alpha and DQ beta polymorphism. From the same set of cells, DNA was isolated and analyzed for RFLP. Polymorphism could be detected by both techniques, i.e., on the protein level and on the DNA. The variation in pI of the DQ alpha and beta chains correlated with the polymorphism as detected by HTC typing, as did the variation in molecular weight of the bands hybridizing to DQ specific cDNA probes; identical patterns were detected for cells of one HLA-D specificity and different patterns for different HLA-D types. Additionally, DQ reactive PLT reagents were raised against DRw6 positive cells. Panel studies revealed that these DQ reactive proliferative T cells can discriminate between the polymorphic DQ antigens on cells with different HLA-D specificities.

Proarrhythmic and antiarrhythmic effects of flecainide on nonsustained reentry around the canine atrial tricuspid ring in vitro

The effect of flecainide, 0.3 mg/L and 1.0 mg/L, on inducible nonsustained reentry was studied, in vitro, in the canine tricuspid ring. Nonsustained reentry was engineered by cutting the ring and reconnecting it with an adjustable electronic delay. Delays were used that produced reentry lasting 1-3 beats (group A), 4-10 beats (group B), and 11-25 beats (group C). Reentry was initiated multiple times at each selected delay. A proarrhythmic effect, defined as a significant increase in the duration of reentry, was observed in all 14 trials at the low dose and in two of 15 trials at the high dose in seven experiments. In four more trials a transient proarrhythmic response was seen initially during exposure to the high dose. In five of seven experiments, reentry became sustained after at least one dose of flecainide. Proarrhythmic responses resulted when flecainide increased the tachycardia cycle length more than the effective refractory period and there was less cycle length oscillation after initiation. Antiarrhythmic responses resulted either from a marked increase in effective refractory period at the site of block or production of fixed block.

Biphoton holographic storage in Methyl Orange and Ethyl Orange dyes

Biphoton holograms are recorded by a He-Ne laser in Methyl Orange and Ethyl Orange dyes on exposure to a 514.5-nm argon-ion laser, and the dynamic of holographic recording is reported. The recording utilizes an unusual photochemistry that is due to either to a triplet-triplet transition from a long-lived triplet lower state of the cis configuration or a transition back to the trans state.