Multiple calcium channels control neurotransmitter release from rat postganglionic sympathetic nerve terminals

1. Intracellular recording techniques were used to study neurotransmitter release mechanisms in postganglionic sympathetic nerve terminals of the rat isolated anococcygeus muscle. 2. Low concentrations of the N-type calcium channel blocker omega-conotoxin GVIA (omega-CgTX GVIA) irreversibly abolished excitatory junction potentials (EJPs) evoked by trains of < or = five stimuli at 10 Hz. When the frequency of stimulation was increased (10-50 Hz) trains of stimuli evoked EJPs even in the presence of 1 microM omega-CgTX GVIA. We have termed this omega-CgTX GVIA-resistant release 'residual release'. EJP amplitude in the presence of omega-CgTX GVIA depended on both the frequency and number of stimuli in a train. 3. Residual release was inhibited by the P-type calcium channel blocker omega-agatoxin IVA (100 nM). However, even in the presence of both toxins, longer trains of stimuli could still evoke neurotransmitter release. 4. Residual release was abolished by omega-conotoxin MVIIC and by the non-specific calcium channel antagonist omega-grammotoxin SIA. Therefore, it would appear that a heterogeneous population of calcium channels is involved in mediating neurotransmitter release from these sympathetic nerve terminals.

Comparative variation of morphological and molecular evolution through geologic time: 28 S ribosomal RNA versus morphology in echinoids

The comparatively good fossil record of post-Palaeozoic echinoids allows rates of morphological change to be estimated over the past 260 million years and com pared with rates of molecular evolution. Parsimony analysis of morphological data, based predominantly on skeletal characteristics, and parsimony, distance and maximum likelihood analyses of molecular data, from the first 380 bases from the 5' end of the 28 S rRNA molecule, for 10 species of echinoid produce congruent phylogenies. The m olecular sequence chosen is dem onstrably far from saturation and sister groups have divergence times ranging from about 15 to 260 Ma. Parsimony analysis allows the great majority of molecular and morphological apomorphies to be placed in one of 18 independent geological time intervals, providing a direct measure of rates of evolution for periods in the geological past. Because most molecular fixed point m utations in our sequences cannot be polarized unambiguously by outgroup comparison (making the outgroup states effectively random), distance and parsimony analyses both tend spuriously to root the echinoid tree on the longest internal branch. A topology identical to that derived from morphological data is, however, obtained using Maximum Likelihood and also parsimony analysis where outgroup rooting is restricted to more conserved regions. This is taken as the correct topology for assessing rates of evolution. Overall, both morphological and molecular changes show a m oderately strong correlation with time elapsed, but a weaker correlation with one another. Statistically significant differences in evolutionary rate are found between some, but not all, pair-wise comparisons of sister lineages for both molecular and morphological data. The molecular clock rate for echinaceans is three times faster than that for cidaroids and irregular echinoids. Spearm an’s rank correlation test, which requires only relative m agnitude of changes to be known, suggests that morphological change has a slightly better correlation with time than does molecular change, averaged over all ten species. However, when just echinaceans are considered an extremely good correlation is found between the num ber of molecular changes and time elapsed, whereas morphological change remains poorly correlated. Thus, molecular rates approxim ate to a clocklike model within restricted echinoid elades, but vary significantly between clades. Averaging results over all echinoids produces a correlation that is no better than the correlation between morphological change and time elapsed.

Ryanodine-sensitive calcium stores involved in neurotransmitter release from sympathetic nerve terminals of the guinea-pig

1. Intracellular and focal extracellular recording techniques were used to study neurotransmitter release mechanisms in postganglionic sympathetic nerve terminals in the guinea-pig isolated vas deferens. 2. High concentrations of the selective N-type calcium channel blocker omega-conotoxin GVIA abolished the release of the neurotransmitter ATP evoked by trains of low-frequency stimuli. However, in the presence of high concentrations of the blocker, a 'residual release' persisted at higher frequencies. 3. Residual release was dependent on calcium entry through a pharmacologically distinct voltage-dependent calcium channel. 4. Residual release was inhibited by ryanodine in a use- and time-dependent manner and this inhibitory effect was potentiated by caffeine. The inhibitory effect of ryanodine on residual release was reversed by 4-aminopyridine. 5. These findings indicate that calcium-induced calcium released from intraneuronal stores plays an important role in action potential-evoked neurotransmitter release mechanisms in postganglionic sympathetic nerve terminals.

Chromosome 18 translocation (18;21) (p11.1;p11.1) associated with psychosis in one family

In the course of recruiting families with 2 schizophrenic siblings for genome screening and linkage studies, a family was found with mental retardation, schizophrenia, and/or other related psychotic illnesses in individuals who also had an unbalanced or balanced translocation between chromosomes 21-18 [t(18;21)(p11.1;p11.1)]. The pericentric region of chromosome 18 has already been noted as a possible location of a gene for bipolar psychosis. The family described here provides further evidence that this region should be examined for a candidate psychosis gene.

Acute and chronic liver toxicity resulting from exposure to chlorinated naphthalenes at a cable manufacturing plant during World War II

Historical records were used to reconstruct an outbreak of chlorance and acute liver toxicity due to chlorinated naphthalene exposure at a New York State plant which manufactured "Navy cables" during World War II. A cohort mortality study was conducted of the population (n = 9,028) employed at the plant from 1940 to 1944. Vital status was followed through December 31, 1985. The study found an excess of deaths from cirrhosis of the liver [observed (OBS) = 150; standardized mortality ratio (SMR) = 1.84; 95% confidence interval (CI) = 1.56-2.16]; cirrhosis deaths were elevated to a similar degree in the 460 individuals who had chlorance (OBS = 8; SMR = 1.51; CI = 0.65-2.98). The SMR for "non-alcoholic cirrhosis" (OBS = 83; SMR = 1.67; CI = 1.33-2.07) was similar to the SMR for "alcoholic cirrhosis" (OBS = 59; SMR = 1.96; CI = 1.49-2.53). There was no evidence for increased alcoholism in the overall cohort based on mortality from alcohol-related causes of death other than cirrhosis (SMR for esophageal cancer = 1.01 and for deaths from alcoholism = 0.99). We conclude that the excess mortality from cirrhosis of the liver observed in this cohort is due to the chronic effect of chlorinated naphthalene exposure.

The design and synthesis of 2,5-linked pyrrolinones. A potential non-peptide peptidomimetic scaffold

The de novo design and initial synthetic studies directed toward construction of a novel non-peptide scaffold for beta-strand/sheet and related secondary peptide structural mimics are described. The scaffold, consisting of a repeating array of 2,5,5-trisubstituted pyrrolinone (enaminone) units punctuated with appropriate amino acid side chains, is conceptually related to our previously successful 3,5-linked polypyrrolinone non-peptide peptidomimetic scaffold. Construction of the 2,5,5-trisubstituted pyrrolinone ring system proceeds via intramolecular condensation of an N-protected amino dione. The latter is prepared from a protected alpha-amino ketone and aldehyde via an aldol-oxidation reaction sequence.

Synthesis of potent cyclic hexapeptide NK-1 antagonists. Use of a minilibrary in transforming a peptidal somatostatin receptor ligand into an NK-1 receptor ligand via a polyvalent peptidomimetic

The endogenous peptides somatostatin (SRIF) and substance P comprise very different structures. Although both bind G-protein-coupled receptors, the SRIF receptors (SSTR 1-5) recognize SRIF and related peptides which retain its beta-turn such as the potent cyclic hexapeptide SRIF agonist L-363,301 (6a), but not substance P. Conversely the NK-1 receptor binds substance P but not the above ligands. In contrast, the beta-D-glucosides 1 and 2, designed to mimic the beta-turn of 6a, bind both receptors. This observation led us to attempt the conversion of 6a into the first potent, selective cyclic hexapeptide ligand for the NK-1 receptor. To this end, we combined design with a minilibrary approach. The goal was accomplished with surprising ease, leading to the NK-1 receptor antagonist 9 (IC50 2.0 +/- 0.4 nM). This demonstrates that peptidomimetics, incorporating in this case the promiscuous beta-D-glucose scaffold, can provide valuable clues about receptor similarities not revealed by their endogenous ligands. In addition, this work suggests that the use of libraries and rational design need not be mutually exclusive approaches to lead discovery.

Vectorially oriented monolayers of detergent-solubilized Ca(2+) -ATPase from sarcoplasmic reticulum

A method for tethering proteins to solid surfaces has been utilized to form vectorially oriented monolayers of the detergent-solubilized integral membrane protein Ca(2+) -ATPase from the sarcoplasmic reticulum (SR). Bifunctional, organic self-assembled monolayers (SAMs) possessing "headgroup" binding specificity for the substrate and "endgroup" binding specificity for the enzyme were utilized to tether the enzyme to the substrate. Specifically, an amine-terminated 11-siloxyundecaneamine SAM was found to bind the Ca(2+)-ATPase primarily electrostatically. The Ca(2+)-ATPase was labeled with the fluorescent probe 5-(2-[(iodoacetyl)amino]ethyl)aminonaphthalene-1-sulfonic acid before monolayer formation. Consequently, fluorescence measurements performed on amine-terminated SAM/enzyme monolayers formed on quartz substrates served to establish the nature of protein binding. Formation of the monolayers on inorganic multilayer substrates fabricated by molecular beam epitaxy made it possible to use x-ray interferometry to determine the profile structure for the system, which was proved correct by x-ray holography. The profile structures established the vectorial orientation of the Ca(2+)-ATPase within these monolayers, to a spatial resolution of approximately 12 A. Such vectorially oriented monolayers of detergent-solubilized Ca(2+)-ATPase from SR make possible a wide variety of correlative structure/function studies, which would serve to elucidate the mechanism of Ca(2+) transport by this enzyme.

Omega-conotoxin GVIA-resistant neurotransmitter release in postganglionic sympathetic nerve terminals

Intracellular recording techniques were used to study neurotransmitter release in the guinea-pig isolated vas deferens. Low concentrations of the irreversible and selective N-type calcium channel blocker omega-conotoxin GVIA have previously been shown to block excitatory junction potentials evoked by low frequencies (< or = 1 Hz) of nerve stimulation. Here we report a component of action potential-evoked release which is insensitive to high concentrations of omega-conotoxin GVIA. We have termed this component "residual release" and show (i) it is positively frequency-dependent, (ii) its magnitude is dependent on both the train length and interval between trains, (iii) "residual release" can be modulated through prejunctional alpha 2-adrenoceptors and (iv) "residual release" is insensitive to many calcium entry blockers but abolished by omega-grammotoxin SIA and cadmium ions. Although noradrenaline is released by nerve action potentials, residual excitatory junction potentials were abolished by alpha,beta-methylene-ATP and therefore resulted entirely from the actions of neuronally released ATP acting through postjunctional P2x-purinoceptors. The results suggest that calcium entry through a novel, pharmacologically uncharacterized voltage-dependent calcium channel is responsible for "residual release" in sympathetic nerve terminals. It seems that in response to single or short trains of nerve action potentials, N-type calcium channels dominate the release process. However, at higher frequencies other voltage-dependent calcium channels are recruited and these may have an important role to play in triggering the mechanisms underlying frequency-dependent facilitation.

Identification of haptoglobin as a natural inhibitor of trypanocidal activity in human serum

Trypanosomes are protozoan parasites of medical and veterinary importance. Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense infect humans, causing African sleeping sickness. However, Trypanosoma brucei brucei can only infect animals, causing the disease Nagana in cattle. Man is protected from this subspecies of trypanosomes by a toxic subtype of high density lipoproteins (HDLs) called the trypanosome lytic factor (TLF). The toxic molecule in TLF is believed to be the haptoglobin-related protein that when bound to hemoglobin kills the trypanosome via oxidative damage initiated by its peroxidase activity. The amount of lytic activity in serum varies widely between different individuals with up to a 60-fold difference in activity. In addition, an increase in the total amount of lytic activity occurs during the purification of TLF, suggesting that an inhibitor of TLF (ITLF) exists in human serum. We now show that the individual variation in trypanosome lytic activity in serum correlates to variations in the amount of ITLF. Immunoblots of ITLF probed with antiserum against haptoglobin recognize a 120-kDa protein, indicating that haptoglobin is present in partially purified ITLF. Haptoglobin involvement is further shown in that it inhibits TLF in a manner similar to ITLF. Using an anti-haptoglobin column to remove haptoglobin from ITLF, we show that the loss of haptoglobin coincides with the loss of inhibitor activity. Addition of purified haptoglobin restores inhibitor activity. This indicates that haptoglobin is the molecule responsible for inhibition and therefore causing the individual variation in serum lytic activity.

Killing of trypanosomes by the human haptoglobin-related protein

African trypanosomes cause disease in humans and animals. Trypanosoma brucei brucei affects cattle but not humans because of its sensitivity to a subclass of human high density lipoproteins (HDLs) called trypanosome lytic factor (TLF). TLF contains two apolipoproteins that are sufficient to cause lysis of T. b. brucei in vitro. These proteins were identified as the human haptoglobin-related protein and paraoxonase-arylesterase. An antibody to haptoglobin inhibited TLF activity. TLF was shown to exhibit peroxidase activity and to be inhibited by catalase. These results suggest that TLF kills trypanosomes by oxidative damage initiated by its peroxidase activity.

A combined morphological and molecular phylogeny for sea urchins (Echinoidea: Echinodermata)

Phylogenetic relationships of higher taxa of echinoids have been investigated using a 163 character morphological data base and molecular sequences from large and small subunit (LSU and SSU) ribosomal RNA (rRNA) genes. The complete SSU rRNA gene has been sequenced for 21 taxa, with representatives from nine of the 14 extant orders of Echinoidea. Partial LSU sequences, representing the first 400 base pairs (b.p.) from the 5' end were also sequenced for three taxa to complement an existing data base of ten taxa. The two molecular sequences provided a total of 371 variable sites, of which 143 were phylogenetically informative (compared to 145 phylogenetically informative sites from morphological data). Morphological, LSU and SSU data have been analysed separately and together. Morphological and SSU sequence data generate topologies that are not significantly in conflict (under Templeton's test), but the strong signal pairing arbaciids with clypeasteroids in the LSU derived tree marks the LSU sequence data as anomalous for this taxon. A 'total evidence' approach derived a tree very similar in topology to that derived from morphological data. Rooted on the stem group echinoid Archaeocidaris, our total evidence tree suggested relationships of higher taxa as follows: Cidaroida (Phormosomatidae (Echinothuriidae (Diadematidae ((Spatangoida (Clypeasteroida, Cassiduloida)) ((Calycina, Arbacioida) (Stomopneustidae (Glyphocidaridae (Temnopleuridae (Echinometridae (Echinidae, Stronglyocentridae)))))))))). Phylogenetic analyses run both with and without key fossil taxa yielded slightly different topologies. It is important to include fossil taxa in a phylogenetic analysis where there are long stem-group branches or where the crown group is highly derived.

Production and oxidation of indole by Haemophilus influenzae

During growth in high concentrations of iron nitrate, H. influenzae produces compounds reactive in biochemical assays for hydroxamates. Mixing experiments established that nitrate was responsible for inducing these compounds. Analysis by 1H and 13C NMR and high resolution mass spectrometry identified the active species as 2,2-bis(3'-indolyl)indoxyl. Bacterial production of the latter compound has been previously observed only in Pseudomonas aureofaciens. A mutant defective in the production of 2,2-bis(3'-indolyl)indoxyl was constructed by marker insertion. The formation of indole and 2,2-bis (3'-indolyl)indoxyl was quantitated by reverse-phase high pressure liquid chromatography during growth in high concentrations of nitrate. The mutant produced high concentrations of indole, but only minimal amounts of 2,2-bis(3'-indolyl)indoxyl, and also proved to be defective in nitrate reduction. These data suggest that indole may function as an electron donor for nitrate reductase in H. influenzae.

Design and synthesis of nonpeptide peptidomimetic inhibitors of renin

The desire to replace the amide backbone of renin inhibitors with a new scaffold led us to explore vinylogous amides (enaminones). An initial attempt proved unsuccessful, a result explained after the fact via docking experiments. Based on this lesson, we designed a different vinylogous amide scaffold which incorporated one or more pyrrolinone rings into the backbone. Three of the four compounds gave IC50S in the 0.6 to 18 microM range. These compounds did not inhibit HIV-1 protease. Taken together, the results reported herein provide insights into the role of hydrogen bonding and steric interactions for binding to renin.

Factors affecting the life span of peripheral intravenous lines in hospitalized infants

A study was undertaken to identify the effect of insertion site, cannula size and brand type, blood, and unit setting on the life span of IVs in hospitalized infants. A comparative descriptive design was used to study 250 data sets gathered from charts of infants 12 months of age and under, in the NICU, PICU, and general pediatric units at a children's medical center in the Southwest. Analysis revealed no significant difference in life span of nonelectively discontinued IVs by insertion site, cannula size, or brand type. A statistical difference was found in the life span of IVs regarding blood infusion: IVs in which blood had infused lasted longer than those without blood products. A statistical difference in IV life span was also found between the unit settings, with a longer life span for IVs on the general pediatric units than for those on the NICU. Research-based knowledge about factors that influence the life span of IVs in infants could be helpful in making practice decisions and in parent teaching.

Cancer mortality patterns among female and male workers employed in a cable manufacturing plant during World War II

A cohort mortality study was conducted among 9028 (3042 women, 5986 men) workers potentially exposed to chlorinated naphthalenes (chloracnegens structurally similar to dioxins) and asbestos in the manufacture of Navy cable during World War II. Based on mortality through December 31, 1985, standardized mortality ratios (SMRs) for all cancers was 1.03 in women (95% confidence interval [CI] = 0.9 to 1.17) and 1.18 in men (95% CI = 1.10 to 1.26). There were no significant elevations in causes of death hypothesized a prior to be associated with chlorinated naphthalene exposure (malignant neoplasms [MN] of connective tissue, liver, and lymphatic and hematopoietic organs). An excess of MN of the connective tissue was suggested for workers with over 1 year of exposure and 25 years of latency (SMR = 3.54; 95% CI = 0.97 to 9.07). Among cancer sites not hypothesized to be related a priori, three showed concordant excesses among both genders (MN of stomach; rectum; and trachea, bronchus, and lung). No significant elevations occurred in hormonally related cancers among women. Cancer mortality among 460 individuals with chloracne (431 men, 29 women) was similar to that of the entire cohort, although the chloracne subcohort showed significant excesses in two rare causes of death (MN of esophagus, SMR = 3.26; "benign and unspecified neoplasms," SMR = 4.93). Use of county referent rates decreased SMRs for stomach, rectal, and buccal cavity cancer, suggesting a role for nonoccupational risk factors. It is difficult to draw conclusions about carcinogenicity of chlorinated naphthalenes because of study limitations, most importantly, concomitant asbestos exposure and the relatively short duration of exposure to chlorinated naphthalenes among most of the cohort.

Peptide synthesis catalyzed by an antibody containing a binding site for variable amino acids

Monoclonal antibodies, induced with a phosphonate diester hapten, catalyzed the coupling of p-nitrophenyl esters of N-acetyl valine, leucine, and phenylalanine with tryptophan amide to form the corresponding dipeptides. All possible stereoisomeric combinations of the ester and amide substrates were coupled at comparable rates. The antibodies did not catalyze the hydrolysis of the dipeptide product nor hydrolysis or racemization of the activated esters. The yields of the dipeptides ranged from 44 to 94 percent. The antibodies were capable of multiple turnovers at rates that exceeded the rate of spontaneous ester hydrolysis. This achievement suggests routes toward creating a small number of antibody catalysts for polypeptide syntheses.

Vectorially oriented membrane protein monolayers: profile structures via x-ray interferometry/holography

X-ray interferometry/holography was applied to meridional x-ray diffraction data to determine uniquely the profile structures of a single monolayer of an integral membrane protein and a peripheral membrane protein, each tethered to the surface of a solid inorganic substrate. Bifunctional, organic self-assembled monolayers (SAMs) were utilized to tether the proteins to the surface of Ge/Si multilayer substrates, fabricated by molecular beam epitaxy, to facilitate the interferometric/holographic x-ray structure determination. The peripheral membrane protein yeast cytochrome c was covalently tethered to the surface of a sulfhydryl-terminated 11-siloxyundecanethiol SAM via a disulfide linkage with residue 102. The detergent-solubilized, photosynthetic reaction center integral membrane protein was electrostatically tethered to the surface of an analogous amine-terminated SAM. Optical absorption measurements performed on these two tethered protein monolayer systems were consistent with the x-ray diffraction results indicating the reversible formation of densely packed single monolayers of each fully functional membrane protein on the surface of the respective SAM. The importance of utilizing the organic self-assembled monolayers (as opposed to Langmuir-Blodgett) lies in their ability to tether specifically both soluble peripheral membrane proteins and detergent-solubilized integral membrane proteins. The vectorial orientations of the cytochrome c and the reaction center molecules were readily distinguishable in the profile structure of each monolayer at a spatial resolution of 7 A.