Characterization of the calmodulin-binding domain of rat cerebellar nitric oxide synthase

Nitric oxide (NO) has recently been identified as an intercellular messenger which is involved in the regulation of neurotransmission, vasorelaxation, and cytotoxicity. In cerebellum and endothelium this compound is synthesized by "constitutive" nitric oxide synthases (NOS); these are Ca(2+)-calmodulin (CaM)-dependent enzymes. A potential CaM-binding domain for the CaM-dependent NOS has previously been identified in the gene sequence. In this work, a synthetic 23 residue peptide encompassing the putative CaM-binding domain of rat cerebellar NOS was studied. The constitutive NOS peptide binds to CaM in a calcium-dependent manner with 1:1 stoichiometry as determined by polyacrylamide gel electrophoresis of the peptide-CaM complex in 4 M urea. Circular dichroism studies showed that the peptide binds to CaM in an alpha-helical conformation. Binding of the constitutive NOS peptide inhibits the stimulatory effect of CaM on cyclic nucleotide phosphodiesterase. From competition experiments between the peptide and phosphodiesterase we have determined a Kd of 2.2 nM for the peptide-CaM complex. Two-dimensional NMR and circular dichroism studies were used to determine the structure of the peptide in aqueous solution. In addition, the effect of increasing amounts of trifluoroethanol on the peptide structure was investigated. It was found that the peptide can adopt an alpha-helical structure which bears close resemblance to the structure of the CaM-bound form of the CaM-binding domains of myosin light chain kinases.

Cytochrome b5 involvement in cytochrome P450 monooxygenase activities in house fly microsomes

The involvement of cytochrome b5 in different cytochrome P450 monooxygenase and palmitoyl CoA desaturase activities in microsomes from insecticide-resistant (LPR) house flies was determined using a specific polyclonal antiserum developed against house fly cytochrome b5. Anti-b5 antiserum inhibited the reduction of cytochrome b5 by NADH-cytochrome b5 reductase. The antiserum also inhibited palmitoyl CoA desaturase, methoxycoumarin-O-demethylase (MCOD), ethoxycoumarin-O-deethylase (ECOD), and benzo[a]pyrene hydroxylase (aromatic hydrocarbon hydroxylase, AHH) activities. However, methoxyresorufin-O-demethylase (MROD) and ethoxyresorufin-O-deethylase (EROD) activities were not affected by this antiserum. These results demonstrate that cytochrome b5 is involved in fatty acyl CoA desaturase activities and in certain cytochrome P450 monooxygenase activities (i.e., MCOD, ECOD, and AHH) in LPR house fly microsomes. Other cytochrome P450 monooxygenase activities (i.e., MROD and EROD) may not require cytochrome b5. The results suggest that cytochrome b5 involvement with cytochrome P450 monooxygenase activities is dependent upon the cytochrome P450 isoform involved.

Topical capsaicin treatment suppresses formalin-induced fos expression in rat spinal cord

Capsaicin (Cap) is a pharmacological tool to inactivate nociceptive afferents. The present study was undertaken to investigate the effects of topical application of Cap to sciatic nerve on the formalin-induced expression of proto-oncogene proteins c-fos in the rat spinal cord using immunohistochemical display of fos-like protein. In rats subjected to formalin injection into the hind paw, numerous fos-like immunoreactivity (FLI) neurons were found in the spinal dorsal horn, with heavy labeling in laminae I-II and V-VI. Following pretreatment of Cap, formalin-induced FLI expression was significantly abolished. It was suggested that activation of Cap-sensitive unmyelinated nociceptive afferents following formalin injection was primarily responsible for the activation of c-fos gene. Our data also provided further evidence supporting that topical application was an effective way to block the transmission of noxious primary afferents.

ELISA for the neuropeptide degrading endopeptidase 3.4.24.11 in human serum and leukocytes

We describe the development of a new ELISA for the detection of neural endopeptidase 3.4.24.11 (NEP). Neutral endopeptidase 3.4.24.11 was determined in preparations of human granulocytes, mononuclear cells (MNC), and in serum. Human recombinant NEP was used as reference. Specificity of the mAbs was tested using APAAP, FACS analysis, and Western blot analysis. Lysis of the blood cells was performed by incubating the cells with 0.4% Tween-20 and repeated freezing cycles. The minimal detectable dose for recombinant NEP was 15 pg/ml. The recovery was 94 +/- 9%. The NEP was detectable in 15 out of 20 serum samples of 20 volunteers (mean +/- SEM, 245 +/- 88 pg/ml, n = 20)) and in all granulocyte preparations (1176 +/- 138 pg/10(7) cells, n = 20)). The results were reproducible among replicates (CV = 3 +/- 1%, n = 40), dilutions (CV = 8 +/- 2%, n = 5), and assays (CV = 12 +/- 4%, n = 5). With this new ELISA, a simple and reproducible method for the measurement of NEP 3.4.24.11 is described.

Hoxa-2 mutant mice exhibit homeotic transformation of skeletal elements derived from cranial neural crest

Mice homozygous for a targeted mutation of the Hoxa-2 (Hox 1.11) gene are born with cleft palates and die within 24 hr of birth. Analysis of stained skeletons revealed that homozygous mutant animals contained multiple cranial skeletal defects, including a duplication of the ossification centers of the bones of the middle ear. Histological analysis suggested that this duplication resulted from the transformation of skeletal elements derived from the second branchial arch into more anterior structures, resulting in a duplication of Meckel's cartilage adjacent to the otic capsule. Skeletal elements normally derived from the second arch were absent in the mutants. These data provide direct experimental evidence for the existence of a branchial Hox code.

A 9-year follow-up study of the immunogenicity and long-term efficacy of plasma-derived hepatitis B vaccine in high-risk Chinese neonates

The long-term immunogenicity of and protection provided by a plasma-derived hepatitis B vaccine was determined in a cohort of 98 susceptible Chinese neonates immunized in 1982-1983. Within 24 hours of birth, 89 infants received the first of three 30-micrograms doses of vaccine (at 0, 1, and 6 months) and were subsequently followed up by testing for serological markers of hepatitis B virus and by determining levels of alanine aminotransferase annually for 9 years. After the primary series of vaccine doses, 74 (83%) of 89 subjects developed antibody to hepatitis B surface antigen (anti-HBs). At the 9-year follow-up, 51% of vaccinees still had levels of antibody of > or = 10 mIU/mL, considered the protective level. Seven responders to vaccine (9.4% of 74 evaluable patients) developed antibody to hepatitis B core antigen, and in six of these responders, levels of anti-HBs increased transiently. None of the vaccinees developed chronic carriage of hepatitis B surface antigen or clinical hepatitis. Immunization of high-risk neonates with a plasma-derived hepatitis B vaccine can induce long-lasting protective immunity that can prevent or modify primary infection for at least 9 years. Booster doses are not necessary during this period.

Measurement of membrane bound IgD and IgM on B lymphocytes

An assay system for the determination of the membrane bound IgD (mIgD) and IgM (mIgM) on B lymphocytes was developed by the combination of two new ELISA methods with the results of flow cytometry after labeling with specific antibodies. The mIgD and mIgM of B lymphocytes were prepared by incubating mononuclear cells (MNCs) in Tween 20 containing buffer and repeated freeze/thaw cycles. Optimal results were achieved with 0.2-0.4% Tween 20 and two freezing cycles. With biotin-streptavidin amplification the sensitivity of the ELISA was 30 microU/ml for IgD and 0.5 ng/ml for IgM. In healthy persons 3.5 +/- 0.5 mU mIgD were detected on 10(6) IgD+ cells and 57.1 +/- 5.9 ng mIgM on 10(6) IgM+ cells. The mIgD/mIgM ratio was 0.065 +/- 0.005 mU/ng. The developed ELISA systems utilize only commercially available reagents and therefore provide a convenient reproducible tool for determining membrane bound IgD and IgM on B lymphocytes.

K252a potentiates epidermal growth factor-induced differentiation of PC12 cells

Epidermal growth factor (EGF) induced short neurites in two different strains of PC12 cells. The length of the EGF-induced neurites was markedly increased in the presence of the protein kinase inhibitor K252a, which is known to inhibit differentiation induced by nerve growth factor (NGF). EGF-induced differentiation of PC12 required RNA synthesis and activity of the ras proto-oncogene product. EGF increased the levels of three neurofilament proteins and the mRNA level of two late response genes (SCG10 and 63) known to be induced by NGF. Together, EGF and K252a caused a greater increase in these mRNAs than did either agent alone. K252a did not alter the extent of EGF-induced autophosphorylation of the EGF receptor, but it did decrease the extent of receptor phosphorylation in the absence of added EGF. Thus, the ability of the EGF receptor to trigger neuronal differentiation may depend on the state of its phosphorylation at serine and/or threonine residues. Two other strains of PC12 did not extend neurites when exposed to EGF, even when K252a was also present. Thus, the differentiating effect of EGF on PC12 is PC12 strain-specific.

Solution conformation study of substance P methyl ester and [Nle10]-neurokinin A (4-10) by NMR spectroscopy

High-resolution proton spectra at 500 MHz of two tachykinin peptides, substance P methyl ester (SPOMe) and [Nle10]-neurokinin A (4-10), have been obtained in dimethylsulfoxide (DMSO), and for SPOMe, also in 2,2,2-trifluoroethanol (TFE)/water mixtures. Complete chemical shift assignments for these peptides were made based on two-dimensional (2D) nmr techniques, correlated spectroscopy and total COSY. J coupling measurement and nuclear Overhauser effect spectroscopy (NOESY) were then used to determine the conformation of these peptides in the various solvents. Based on the J coupling, NOE correlations, and temperature coefficients of the NH resonances, it is concluded that these two peptides exist in DMSO at room temperature as a mixture of conformers that are primarily extended. For SPOMe in TFE/water with high TFE content, however, helical structures are found to be present, and they become quite clear at temperatures between 270 and 280 K. The variation of the 13C chemical shifts of the C alpha (the secondary shift) with TFE contents corroborates this conclusion. The NOE and C alpha shifts show that the main helical region for SPOMe lies between 4P and 9G. The C-terminus segment L-M-NH2 is found to be quite flexible, which appears to be quite common for neurokinin-1 selective peptides.

Quantification of left-side intracardiac pressures and gradients using mitral and aortic regurgitant velocities by simultaneous left and right catheterization and continuous-wave Doppler echocardiography

Noninvasive determination of left-side intracardiac pressures is of clinical importance in many cardiac diseases. To test the reliability and accuracy of left-side intracardiac pressure measurements by continuous-wave Doppler echocardiography, using left-side valvular regurgitations, 47 patients with mitral regurgitation, with or without associated aortic regurgitation, underwent simultaneous Doppler and left and right catheterization. Doppler-derived left atrial and ventricular end-diastolic pressures were respectively estimated by subtracting mitral regurgitant gradient from systolic blood pressure and by diastolic blood pressure minus aortic regurgitant gradient. There were high correlations of mitral (r = 0.961) and aortic regurgitant gradients (r = 0.896) and of left atrial (r = 0.945) and ventricular end-diastolic pressures (r = 0.854) between noninvasive and invasive measurements. Also, agreement analyses showed that there was close agreement between the two technical measurements for each parameter. The present study concluded that continuous-wave Doppler echocardiography provides a reliable and accurate method for the noninvasive evaluation of left-side intracardiac pressures and gradients in patients with mitral and aortic regurgitations.

Hepatitis C virus infection in different groups of children in Wuhan area

To investigate the incidence of child's HCV infection in our area, 637 children with different background, including 65 posttransfusion cases, 419 hepatitis patients (250 cases of acute hepatitis A, 156 cases of chronic hepatitis B and 13 cases of non-A, non-B hepatitis), 50 infantile hepatitis syndrome (IHS) infants and 103 healthy day-cared children were tested for serum anti-HCV antibody (EIA) and HCV RNA (nested PCR). It was found that posttransfusion children had significantly higher anti-HCV positive rate (30.8%) and HCV infection incidence (43.1%) than hepatitis patients (4.3% and 5.3%), IHS infants (6.0% and 8.0%) and day-cared children (2.9% and 2.9%). 25 of 33 cases with posttransfusion hepatitis (PTH) developed hepatitis C, which was the leading cause of PTH (75.8%) and NANB PTH (25/30, 83.3%). The incidence of HCV infection in NANBH patients was 23.1% (3/13) which was apparently higher than that in day-cared children (P < 0.02) and lower than that in PTH patients (P < 0.001), but not statistically different from that in AHA and CHB patients (P > 0.05). Mother-infant paired study in IHS group showed that 4 pairs of mother-infant had HCV infection, one boy aged 8 months and his mother were anti-HCV positive, and another 3 pairs possessed HCV RNA in sera. 3 of 103 healthy day-cared children were found to have inapparent HCV infection, who were anti-HCV and HCV RNA positive.

The phylogenetically predicted base-pairing interaction between alpha and alpha' is required for group II splicing in vitro

The correct folding of group II introns apparently depends on multiple tertiary base-pairing interactions. Understanding the relationship between spliceosome and group II splicing systems ultimately requires a three-dimensional model for both structures. In turn, successful modeling depends at least in part on identifying tertiary base pairings. Sequence elements alpha and alpha' are partners in a potential interaction of approximately 6 base pairs that can be identified within domain 1 of most group II introns. In comparisons between related introns, alpha and alpha' maintain their potential for Watson-Crick base pairing, even though their primary sequences can vary [Michel, F., Umesono, K. & Ozeki, H. (1989) Gene 82, 5-30]. Substitutions were constructed at alpha and alpha' for a block of 6 bases each in the group II intron a5 gamma, the last intron of the COXI gene from the mitochondrial DNA of Saccharomyces cerevisiae. Each substitution was defective for self-splicing, while the compensatory double derivative was restored to active splicing. The alpha-alpha' interaction is required for the first step of splicing--that is, recognition of the 5' splice junction and transesterification with the branch site--since the derivative transcripts displayed little or no activity. The compensatory double derivative produced lariat introns and spliced exons with normal structures, showing that splicing activity and precise recognition were restored. We conclude that the alpha-alpha' base pairing is necessary for efficient self-splicing by intron a5 gamma under several conditions. This result also provides an additional constraint for any three-dimensional model of group II intron structure.

Effects of tetrandrine on functions and ultrastructure of alveolar macrophages in smoke inhalation-injured rabbits

A rabbit model with severe smoke inhalation injury was used to explore the effects of tetandrine (Tet) on the release of inflammatory mediators and the level of [Ca2+]i in alveolar macrophages (AM) as well as on the ultrastructural changes. It was found that Tet reduced the number of white blood cells (WBC) in bronchoalveolar lavage fluid, inhibited the release of LTB4 and O2-. from AM, and increased the [Ca2+]i in AM. The changes in size, pseudopod, and lysosome evacuation in AM treated with Tet were smaller than those in the AM from the untreated. These results suggest that Tet may alleviate the pulmonary injury through inhibiting the activation of AM.

The effect of shear forces externally applied to skin surface on underlying tissues

The effects of shear forces externally applied to the skin surface on the underlying tissues have been investigated. An analysis of the internal stresses and strains was conducted using a simplified model incorporating elasticity theory. Skin blood flow was measured using laser Doppler flowmetry while variable shear forces over a range of 0-250 g were applied to the skin surface. The theoretical model predicts that the application of surface shear forces alters the internal stress distribution and makes the shear and compressive components of stresses increase ahead of the surface force application point. The force resulting from concomitant application of shear and normal force determines the internal maximum stress and strain. Theoretically, the shear force should have the same effects on the underlying tissues as normal force. The experimental investigations revealed that the skin blood flow decreased roughly linearly with the increase of shear forces. When a shear force equal to the normal force was applied, the flux decreased by 45%, nearly equal to the increasing magnitude (41%) of resultant of normal and shear forces.

A peptide analog of the calmodulin-binding domain of myosin light chain kinase adopts an alpha-helical structure in aqueous trifluoroethanol

A 22-residue synthetic peptide encompassing the calmodulin (CaM)-binding domain of skeletal muscle myosin light chain kinase was studied by two-dimensional NMR and CD spectroscopy. In water the peptide does not form any regular structure; however, addition of the helix-inducing solvent trifluoroethanol (TFE) causes it to form an alpha-helical structure. The proton NMR spectra of this peptide in 25% and 40% TFE were assigned by double quantum-filtered J-correlated spectroscopy, total correlation spectroscopy, and nuclear Overhauser effect correlated spectroscopy spectra. In addition, the alpha-carbon chemical shifts were obtained from (1H,13C)-heteronuclear multiple quantum coherence spectra. The presence of numerous dNN(i, i + 1), d alpha N(i, i + 3), and d alpha beta(i, i + 3) NOE crosspeaks indicates that an alpha-helix can be formed from residues 3 to 20; this is further supported by the CD data. Upfield alpha-proton and downfield alpha-carbon shifts in this region of the peptide provide further support for the formation of an alpha-helix. The helix induced by TFE appears to be similar to that formed upon binding of the peptide to CaM.

Antisense oligodeoxynucleotide reduces brain dopamine D2 receptors: behavioral correlates

Intraventricular infusion of an antisense oligodeoxynucleotide corresponding to the rat dopamine D2 receptor mRNA reduced rat striatal D2 receptors by 485, as measured by homogenate binding assays, while D1, muscarinic, and serotonin 5-HT2 receptors were unaffected. D2 receptor autoradiography indicated a homogeneous down-regulation of about 50% throughout the striatum and over 70% in the nucleus accumbens. A random oligodeoxynucleotide failed to affect either striatal D2 or D1 receptor density. The antisense treatment inhibited the D2 receptor agonist quinpirole-induced locomotor activation, without altering grooming behavior induced by SKF38393, a D1 receptor agonist. Antisense treatment also elicited catalepsy and reduced spontaneous locomotor activity.

Determination of the side chain pKa values of the lysine residues in calmodulin

The 7 Lys residues in mammalian calmodulin (CaM) were reductively methylated with 13C-enriched formaldehyde and studied by (1H,13C)-heteronuclear multiple quantum coherence (HMQC) NMR. The apo- and Ca(2+)-forms of CaM, as well as a complex with a 22-residue peptide which comprises the CaM binding region of myosin light chain kinase were studied. The complete assignment of the two-dimensional NMR spectra was obtained by site-directed mutagenesis (Lys-->Gln) of all the Lys. The pKa values for the individual Lys could be determined by pH titration experiments. In Ca(2+)-CaM, the pKa values range from 9.29 (Lys-75) to 10.23 (Lys-77). The Lys in apo-CaM have higher pKa values than those in Ca(2+)-CaM. The binding of the myosin light chain kinase peptide gives rise to an increase of the pKa values of Lys-148 and Lys-75 by 0.5 and 0.8 pH units, respectively; this results from the relocation of their side chains to a completely solvent accessible state. The changes in the pKa values upon binding Ca2+ or the myosin light chain kinase peptide show a remarkable correlation with earlier reported chemical reactivity changes. Thus, our results indicate that pKa values, rather than structural and steric effects, play the dominant role in determining the reactivity of Lys side chains towards small electrophilic chemical modification reagents. The methodology used here could prove useful for the determination of individual pKa values in other proteins.

[Study on 125I-labeled human chorinic gonadotropin after purification through gel electrophoresis]

Radioiodination of HCG with 125I Na using chloramine-T is widely employed. However, 125I-HCG damages in storage and thus results in decrease of immunological and biological activities. When 125I-HCG was in store as long as 30 days, the immunological activity and biological activity decreased from 100% to 33.1% and 44.0%, respectively. We used polyacrylamide gel electrophoresis to purify 125I-HCG which had been kept in store for 30 days since radiolabeling, and we found the binding capacities of purified 125I-HCG increased. The combination rates of purified 125I-HCG with antibody and receptors accounted for 90.5% and 95.3% of those of 125I-HCG 1 day after radiolabeling. These results suggest that 125I-HCG which has been stored for a period since radiolabeling should be purified before use.

Nicotinic cholinoceptor-mediated excitatory postsynaptic potentials in rat nucleus ambiguus

In rat brainstem slice preparations, intracellular recording from neurons (n = 39) in the compact formation of the nucleus ambiguus (AMBc) revealed spontaneous and miniature excitatory postsynaptic potentials (EPSPs; n = 11) that, along with acetylcholine-induced depolarization, were enhanced by physostigmine (10 microM; n = 2) and blocked by dihydro-beta-erythroidine 1-5 pmol (n = 4). Retrograde neuronal tracing combined with choline acetyltransferase immunocytochemistry demonstrated that the AMBc receives a projection from a subpopulation of cholinergic neurons in the zona intermedialis reticularis parvicellularis. Electrical stimulation of this region in slices evoked fast EPSPs in AMBc neurons (n = 23) that were inhibited by dihydro-beta-erythroidine 2-5 pmol (n = 8), but not by methscopolamine 1 pmol (n = 2). The present findings strongly support the existence of a cholinergic nicotinic synapse mediating fast transmission in brainstem vagal motoneurons.

Gene mapping and sequence analysis of the unique short region of the simian herpesvirus SA 8 genome

A 10.5 kbp BamHI restriction fragment representing most of the unique short (Us) region of the genome of the simian alpha-herpesvirus SA8 was identified and cloned. Partial sequencing of this DNA fragment identified regions of sequence homology with eight open reading frames (ORFs) of HSV1 and/or HSV2. Sequence and size analysis of subcloned fragments of the SA8 Us region and comparison with homologous HSV Us sequences determined that the number, order, size, and orientation of SA8 Us ORFs are comparable to those of HSV. Based on the location of transcriptional control elements, transcription of SA8 Us genes appears to be organized into 3' co-terminal mRNA sets as in HSV, although the grouping of the gene sets is different. The SA8 US4 (gG) ORF is more similar to that of HSV2 than HSV1, both in size and predicted amino acid sequence. Complete sequences were determined for five SA8 genes which represent homologs of the HSV gD, gE, gI, US5, and US9 genes. The predicted polypeptides encoded by SA8 are similar to the corresponding HSV polypeptides. All SA8 Us genes were more closely related to those of HSV than to related gene homologs of other mammalian alpha-herpesviruses.

A new technique for post-embedding immunogold localization of vasopressin in the rat median eminence

A modified cryosubstitution method is described which simultaneously preserves the ultrastructure and antigenicity of the osmium-sensitive neuropeptide vasopressin in rat median eminences. The organs were aldehyde-fixed, osmicated, and embedded in Epon. Thin sections were no longer needed to be etched and the titer of primary antiserum was near to the light microscopic level. Furthermore ice crystallization could not be observed.