A model of calcium dynamics in cardiac myocytes based on the kinetics of ryanodine-sensitive calcium channels

The ryanodine-sensitive calcium channels are pivotal to signal transduction and cell function in many cell types, including cardiac myocytes. In this paper a kinetic model is proposed for these channels. In the model there are two Ca regulatory sites on the channel protein, one positive and the other negative. Cytoplasmic Ca binds to these regulatory sites independently It is assumed that the binding of Ca to the positive site is a much faster process than binding to the negative site. At steady state, the channel opening as a function of the Ca concentration is a bell-shaped curve. The model predicts the adaptation of channels to constant Ca stimulus. When this model is applied to cardiac myocytes, it predicts excitability with respect to Ca perturbations, smoothly graded responses, and Ca oscillations in certain pathological circumstances. In a spatially distributed system, traveling Ca waves in individual myocytes exist under certain conditions. This model can also be applied to other systems where the ryanodine-sensitive channels have been identified.

Refined 1.8 A resolution crystal structure of the porcine epsilon-trypsin

Porcine epsilon-trypsin is a three-chain inactivated trypsin from the limited autolysis of porcine beta-trypsin. It is cleaved at positions Lys60-Ser61 and Lys145-Ser146. The crystal structure has been determined by using the molecular replacement method, and refined at 1.8 A resolution. The R-value of final model is 0.184. Comparison with the electron density map of porcine beta-trypsin (PTRY) in complex (BBIT), and with that of native bovine beta-trypsin (HTNA), revealed no obvious changes except at the autolysis positions, and no changes at the active center were observed. The autolysis at positions Lys60-Ser61 and Lys145-Ser146 does not affect the conformation of His-57 in the active center and therefore cannot explain for a loss in porcine epsilon-trypsin activity.

3D-QSAR study on ether and ester analogs of artemisinin with comparative molecular field analysis

Comparative molecular field analysis (CoMFA), a three-dimensional quantitative structure-activity relationship (3D-QSAR) paradigm, was used to study the correlations between the physicochemical properties and the in vitro activities of a series of ether and ester analogs of artemisinin. Four alignment models were used in the CoMFA investigation. The correlations derived from CoMFA analysis with the four alignments proved all to have good predictive values. The steric field predictive model of alignment B is accordant with the experimental results of Avery M A, et al: J Med Chem 1993; 36: 4264-75. The electrostatic field predictive results of alignments A, B, and C are consistent with our previous result of quantum chemical calculation. The highest rcross2 of alignment D, indicated that the side chain of -C6-O2-O1-C10-O3-C7-O4-C12-O5- and atom C16 are important groups of artemisinin analogs for antimalarial activity.

Clonal outgrowths of T and B cells in SCID mice reconstituted with cells from mice with MAIDS

Murine acquired immunodeficiency syndrome (MAIDS), induce in mice by a defective murine retrovirus (BM5def), is characterized by development of severe immunodeficiency and polyclonal lymphoid proliferation which progress to yield oligoclonal populations of T and B cells. Oligoclonal populations transferred to SCID mice grew as clonal CD4+ T cell or B cell lineage transplants having one or more unique clonal integrations of BM5def. In some cases, spleens of single donor mice were shown to contain both B cell and T cell lineage clones that could be transferred individually after separation and were clonally unrelated. Successful transplants were obtained from oligoclonal populations as early as 63 days after infection. Mouse strains both sensitive or moderately resistant to MAIDS yielded clonal transplants.

In murine AIDS, B cells are early targets of defective virus and are required for efficient infection and expression of defective virus in T cells and macrophages

Previous studies showed that B cells and CD4+ T cells are required for induction of a murine retrovirus-induced immunodeficiency syndrome, murine AIDS. Using B6 mice deficient in mature B cells as a result of a knockout of the transmembrane exon of the immunoglobulin M gene, we found that spleen and other tissues from murine AIDS virus-infected mice did not express the defective virus (BM5def) required for induction of disease, even though helper viruses were readily detectable and BM5def proviral DNA was present. This indicates that the B-lineage cells are the primary targets for infection and expression of the defective virus and that in the absence of mature B cells, there is inefficient infection of T cells and macrophages.

The armature in the genital atrium as a new taxonomic character distinguishing females of Phlebotomus papatasi and P. duboscqi (Diptera: Psychodidae)

Descriptions are given of armatures in the genital atria of females of the two morphologically similar sandfly species, Phlebotomus papatasi and P. duboscqi. The species are distinguishable by the size and shape of the armature, the grouping of the spines in the armature and the length and shape of the spines. These characters have been shown to separate females of other closely related species of phlebotomine sandflies.

An experimental trial of artemether in treatment of Pneumocystis carinii in immunosuppressed rats

An immunosuppressed rat model was established by injecting cortisone acetate 25 mg/rat twice a week for 4 weeks and 12.5 mg/rat for another 2 weeks subcutaneously. A development of Pneumocystis carinii pneumonia (PCP) was found at the end of the 6th week in all rats. These rats were injected intramuscularly with artemether at 100 mg/kg once a day for 5 consecutive days. All rats were necropsied at the end of the 8th week. The lung impression smears were stained with Gomori's stain, and Pneumocystis carinii cysts were counted. The ultrastructural changes of trophozoite, precyst and cyst were investigated by transmission electron microscopy on the 7th day after treatment.

Phlebotomine sandflies of Kenya (Diptera: Psychodidae). IV. The armature in the genital atrium of female Larroussius as a means of identification

Descriptions are given of armatures in the genital atria of the six known Kenyan species of phlebotomine sandflies of the subgenus, Larroussius, namely Phlebotomus aculeatus, P. elgonensis, P. guggisbergi, P. longipes, P. orientalis and P. pedifer. Phlebotomus aculeatus, P. longipes and P. pedifer can be recognized by the shapes of their armatures. Differences in the length and arrangement of the spines in the armature of P. elgonensis and P. longipes are diagnostic features. The distinguishing feature of P. guggisbergi is a wide variation in spine thickness. The most notable feature of P. orientalis is the angle at which the spines lie. The appearance of the base of the spermathecal duct remains the method of choice for the identification of all six but, if this feature is not well displayed in dissected females, they can be distinguished by the armature. It is suggested that descriptions of new species should include an illustration of the armature in the genital atrium.

Studies on an artificial trypsin inhibitor peptide derived from the mung bean trypsin inhibitor: chemical synthesis, refolding, and crystallographic analysis of its complex with trypsin

The active fragment with Lys at the reactive site of mung bean trypsin inhibitor (MBILF) is composed of two peptide chains, A1 of 26 residues and A2 of 9 residues linked via two disulfide bonds. In the present study, a peptide of 22 residue comprising the sequence of chain A1 from position 3 to 24 was synthesized by the solid-phase method. This synthetic peptide with six Cys residues contains a reactive site at position Lys11I-Ser12I (I denotes an inhibitor residue). Air oxidation and HPLC purification resulted in two antitrypsin active components, SPC1 and SPC2. Neither SPC1 nor SPC2 can stoichiometrically inhibit trypsin. The Ki values of SPC1 and SPC2 are 1.2 x 10(-7) and 4.0 x 10(-8) M, respectively. The complexes of SPC1 and SPC2 with bovine beta-trypsin (BTRY) were crystallized by ammonium sulphate precipitation at pH 6.4 and 6.0, respectively. The two crystals have the same crystal form with space group P2(1)2(1)2(1) and cell dimension of a = 63.2(2) A, b = 63.5(6) A, and c = 69.8(4) A. The crystal structure of one complex, SPC1-BTRY, was determined and refined at 2.2 A resolution to a final R-value of 19.2%. From the resulting electron density map, 9 residues of SPC1, from position 9I to 17I, were identified clearly and three-dimension atomic model of the 9-residue reactive loop formed by a disulfide bridge, Cys9I-Cys17I, was built. No electron density corresponding to the other 13 residues was observed in the present map.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effects of dingduwan on electric activities of gastrointestinal smooth muscle and effect of gastrointestinal motility]

Dingduwan (DDW) is a Chinese herbal medicine. Method of modified synchronous recording was used to study the electric activities of gastrointestinal (GI) smooth muscle and the effect of GI motility treated by DDW. A dosage of 3.5 g/kg for ingestion in rats markedly increased the average amplitude of GI slow wave, the total amplitude of GI motion, the rate of GI slow wave and intestinal motion (P < 0.05), but it had no significant effects on the frequency of gastroelectric slow wave and gastric motility (P < 0.05). DDW in the dosage of 5.2 g/kg for ingestion markedly promoted the recovery of intestinal intussusception in mice (P > 0.05). The results showed that DDW markedly increased the intestinal electricity and motility more than that of stomach.

Comparison of cardiac electrophysiologic effects of experimental hypothyroidism and chronic oral amiodarone administration in dogs

A comparative study on ventricular electrophysiologic effects of experimental hypothyroidism and chronic oral amiodarone administration was made in canine models, with the application of electrical stimulation and monophasic action potential recording. The results showed similar effects possessed by hypothyroidism and amiodarone, which included prolongations in ventricular repolarization and refractoriness, an increase in ventricular fibrillation threshold, and a decrease in the incidence of reperfusion ventricular fibrillation. The differences were that hypothyroidism primarily lengthened phase 2 repolarization and had no effects on intraventricular conduction time, whereas amiodarone lengthened both phase 2 and phase 3 repolarization and suppressed myocardial conduction velocity.

Influence of H-2 class II antigens on the development of murine AIDS

Inbred strains of mice differ markedly in their relative susceptibility to the development of lymphoproliferation and immunodeficiency, a syndrome termed mouse AIDS (MAIDS), after infection with the LP-BM5 mixture of murine leukemia viruses (MuLV). The etiologic virus in this mixture is replication defective (BM5def) and encodes only a variant gag protein. Genetic determinants of resistance and susceptibility to induction of MAIDS reside both within and outside the MHC. In strains with C57BL background genes, the MHC haplotypes associated with resistance to disease include d and a, whereas haplotypes b, s, and q are associated with sensitivity. Previous studies showed that MHC class I genes (H-2Dd, H-2Ld) mapping in the D end of H-2 and other genes mapping proximal to the D end determine resistance to MAIDS. This paper examines the nature of these non-D end MHC genes using assays of MHC recombinant and transgenic mice. We demonstrate that expression of E alpha d confers significant resistance to MAIDS, even in mice that do not express H-2Dd/H-2Ld. Unexpectedly, we found that E alpha polymorphisms can significantly influence resistance, with H-2b mice bearing E alpha d as a transgene having greater resistance to MAIDS than mice bearing an E alpha k transgene. E alpha d-mediated resistance to MAIDS was associated with decreased levels of the BM5def genome in splenic DNA, suggesting that E alpha genes exert their effect by enhancing antiviral activity.

Influence of H-2 class II antigens on the development of murine AIDS

Inbred strains of mice differ markedly in their relative susceptibility to the development of lymphoproliferation and immunodeficiency, a syndrome termed mouse AIDS (MAIDS), after infection with the LP-BM5 mixture of murine leukemia viruses (MuLV). The etiologic virus in this mixture is replication defective (BM5def) and encodes only a variant gag protein. Genetic determinants of resistance and susceptibility to induction of MAIDS reside both within and outside the MHC. In strains with C57BL background genes, the MHC haplotypes associated with resistance to disease include d and a, whereas haplotypes b, s, and q are associated with sensitivity. Previous studies showed that MHC class I genes (H-2Dd, H-2Ld) mapping in the D end of H-2 and other genes mapping proximal to the D end determine resistance to MAIDS. This paper examines the nature of these non-D end MHC genes using assays of MHC recombinant and transgenic mice. We demonstrate that expression of E alpha d confers significant resistance to MAIDS, even in mice that do not express H-2Dd/H-2Ld. Unexpectedly, we found that E alpha polymorphisms can significantly influence resistance, with H-2b mice bearing E alpha d as a transgene having greater resistance to MAIDS than mice bearing an E alpha k transgene. E alpha d-mediated resistance to MAIDS was associated with decreased levels of the BM5def genome in splenic DNA, suggesting that E alpha genes exert their effect by enhancing antiviral activity.

Phlebotomine sandflies of Kenya (Diptera: Psychodidae). III. The identification and distribution of species of the subgenus Larroussius

The six species of phlebotomine sandflies of the subgenus Larroussius recorded in Kenya are Phlebotomus aculeatus, P. elgonensis, P. guggisbergi, P. longipes, P. orientalis and P. pedifer. Five are proven vectors of leishmaniasis in that country or elsewhere. Males of all six can be identified by the morphology of the aedeagus or the number and position of the hairs on the inner surface of the coxite. Additional features separating some of the species are the sizes of the palpal and antennal segments. The females have usually been considered difficult or impossible to distinguish. A comparison of the base of the spermathecal ducts is made and it is shown that all six can be identified by this character alone. A map of Kenya is given, showing the presently known distribution of the six Larroussius species. Further surveys are necessary in parts of the country that have not been systematically surveyed.

A G protein-based model of adaptation in Dictyostelium discoideum

A new model is proposed based on signal transduction via G proteins for adaptation of the signal relay process in the cellular slime mold Dictyostelium discoideum. The kinetic constants involved in the model are estimated from Dictyostelium discoideum and other systems. A qualitative analysis of the model shows how adaptation arises, and numerical computations show that the model agrees with observations in both perfusion and suspension experiments. Several experiments that can serve to test the model are suggested.

Anthroponotic cutaneous leishmaniasis in Kabul, Afghanistan: the low susceptibility of Phlebotomus papatasi to Leishmania tropica

Females of a laboratory colony of Phlebotomus papatasi from Kabul were fed through a membrane on a high dose of amastigotes of Leishmania tropica from the same place. Less than one-third of the flies became infected and only 6% developed heavy infections of the stomodaeal valve. From these observations, and previous studies by other workers, it is concluded that P. papatasi probably plays little or no part in the transmission of anthroponotic cutaneous leishmaniasis in Kabul. As in Saudi Arabia and Morocco, the most likely vector in Afghanistan is P. sergenti.

Identification of a human CD36 isoform produced by exon skipping. Conservation of exon organization and pre-mRNA splicing patterns with a CD36 gene family member, CLA-1

During an examination of different cell types for CD36 mRNA splice variants, a partial cDNA from HEL cells was isolated and characterized. This CD36 cDNA had a 309-base pair deletion following the region encoding the first putative transmembrane domain of CD36. The open reading frame of the deleted CD36 cDNA was retained and was predicted to yield a protein lacking 103 amino acid residues. The presence of this variant was confirmed in RNA pools from placental tissue by a reverse transcriptase-coupled polymerase chain reaction assay. Comparison of the HEL CD36 cDNA with the genomic sequence revealed that the mRNA represented by this variant CD36 cDNA was produced by a pre-mRNA splicing reaction that excluded exons 4 and 5. Transient expression of the variant CD36 cDNA in COS-1 cells showed that CD36 immunoreactive protein was expressed on the cell surface but lacked an antigenic epitope defined by amino acid residues 41-143. This cell surface glycoprotein (M(r) approximately 57,000) was of identical molecular weight as a CD36 isoform observed on the surface of HEL cells. The exclusion of exons during CD36 pre-mRNA processing appears to be conserved within one other CD36 gene family member, CLA-1.

Primer extension preamplification for detection of multiple genetic loci from single human blastomeres

A new technology called primer extension preamplification (PEP), which has been applied to single spermatozoa, increases the amount of polymerase chain reaction (PCR) templates by amplifying DNA of the whole genome. The current investigation was aimed at applying PEP to single human blastomeres. Two blastomeres with nuclei from arrested embryos were selected for this study. Using three different PEP protocols (experiments I, II and III), DNA from single blastomeres was amplified using 15-base oligonucleotide random primers. The efficiency of the procedure was determined by further amplifications of aliquots of the PEP products with two specific sequences. Three aliquots from each PEP product were used as PCR templates for the human X chromosome (X) or the exon 10 of the cystic fibrosis gene (CF). PCR amplified products were analysed by gel electrophoresis. In experiment I, when X primers were used, positive signals were detected in all 10 embryos (100%), 90.0% (18/20) of the blastomeres, and in 80.0% (96/120) of the replicates. When CF primers were amplified, all embryos (100%, 10/10), 90.9% (18/20) of the blastomeres and 78.3% (47/60) of the replicates were positive. In experiment II, efficiency was significantly reduced when total time for the procedure was minimized from 8 h to 5 h and 45 min. Although the time was further reduced to 4 h and 40 min in experiment III, the efficiency remained the same as in experiment I when the volume of PEP was reduced from 60 microliters (experiments I and II) to 40 microliters. One out of 132 control replicates (0.8%) was contaminated.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of two alternatively spliced 5'-untranslated exons of the human CD36 gene in different cell types

We determined the nucleotide sequence of a 2.6-kb BamHI-EcoRI fragment from the 5'-end of the human gene encoding the cell adhesion receptor, CD36. This region contains the first coding exon, exon 3, as well as two non-coding exons, exons 2a and 2b, from the 5'-flanking region. Also present in the 5'-flanking region are two Alu repeats belonging to the Alu-Sa subfamily. When the determined genomic sequence was compared to a placental cDNA sequence [Oquendo et al., Cell 58 (1989) 95-101] and to a human erythroid leukemia (HEL) cell CD36 cDNA sequence (this report), we found that exons 2a and 2b do not occur within the same mRNA, suggesting that alternative splicing occurs within the 5'-untranslated region (UTR) of human CD36 pre-mRNA. These observations were confirmed by reverse transcriptase-coupled polymerase chain reaction (RT/PCR) assays using RNA from placental tissue, HEL cells and human platelets. Exon 2b encodes two alternative translation initiation codons which may render exon 2b-containing CD36 mRNA untranslatable. To test this hypothesis, we transfected COS-1 cells with an exon 2b-containing CD36 cDNA construct. Using anti-CD36 polyclonal antibody, we were able to detect an immunoreactive protein, consistent in size with the mature protein observed in transfected COS-1 cells. Therefore, exon 2b itself is insufficient to block translation of CD36 mRNA.