Effects of dietary nucleoside-nucleotide mixture on memory in aged and young memory deficient mice

Intestinal mucosa, bone marrow hematopoietic cells and brain have limited capacity for the de novo synthesis of nucleosides (NSs) and nucleotides (NTs). Whereas the role of dietary NS and NT in the former two tissues is known, it is not known in the brain. Therefore we studied the effect of dietary NS and NT mixture on memory in aged mice (Experiment 1) and young memory deficient mice (Experiment 2). Memory retention was studied by step-through type passive avoidance performance (maximum 180 seconds). In Experiment 1 aged (7 month old) senescence accelerated mice (SAM) were fed 20% casein diet (control) or this diet supplemented with 0.5% NS/NT mixture for 12 weeks. Memory was studied 1, 2 and 3 days after the electric shock (punishment). In Experiment 2, young (1 month old) memory deficient mice (Dull mice) and normal mice (ddY mice) were fed the same diets as those in Experiment 1 for 12 weeks. Memory retention was studied 1 and 3 days after the punishment. In the aged SAM the average time of avoidance and also the percentages of successful memory 2 and 3 days after the punishment were significantly higher in the NS/NT diet group than the control diet group (P < 0.05). In the Dull mice percentage of successful memory was higher in the NS/NT diet group than in the control group 3 days after the punishment, however, such an effect was not observed in the normal mice. These results suggest that insufficient endogenous supply of NSs and NTs may be responsible for the factor of memory deficiency with aging or of genetical memory deficiency, which can be improved by the dietary administration of NSs and NTs.

The methylotrophic yeast Pichia pastoris synthesizes a functionally active chromophore precursor of the plant photoreceptor phytochrome

Induction of the expression of an algal phytochrome cDNA in the methylotrophic yeast Pichia pastoris led to time-dependent formation of photoactive holophytochrome without the addition of exogenous bilins. Both in vivo and in vitro difference spectra of this phytochromic species are very similar to those of higher plant phytochrome A, supporting the conclusion that this species possesses a phytochromobilin prosthetic group. Zinc blot analyses confirm that a bilin chromophore is covalently bound to the algal phytochrome apoprotein. The hypothesis that P. pastoris contains phytochromobilin synthase, the enzyme that converts biliverdin IX alpha to phytochromobilin, was also addressed in this study. Soluble extracts from P. pastoris were able to convert biliverdin to a bilin pigment, which produced a native difference spectrum upon assembly with oat apophytochrome A. HPLC analyses confirm that biliverdin is converted to both 3E- and 3Z-isomers of phytochromobilin. These investigations demonstrate that the ability to synthesize phytochromobilin is not restricted to photosynthetic organisms and support the hypothesis of a more widespread distribution of the phytochrome photoreceptor.

Potassium currents and membrane excitability of neurons in the rat's dorsal nucleus of the lateral lemniscus

1. The contribution of voltage-activated outward potassium currents to membrane excitability of neurons in the rat's dorsal nucleus of the lateral lemniscus (DNLL) was studied in a brain slice preparation using whole cell patch-clamp and intracellular recordings. Voltage-clamp methods and pharmacological manipulations were used to examine the currents regulating membrane dynamics in DNLL. 2. A delayed sustained outward current was evoked by applying depolarizing voltage steps across the cell membrane from a holding potential of -50 mV. An additional transient outward current was evoked when the depolarizing steps were preceded by a hyperpolarizing prepulse of -110 or -120 mV. 3. The transient outward current peaked within 6.8 ms of the onset of a depolarizing pulse. It decayed with a time constant of 12.3 ms for a 60-mV depolarizing voltage shift. Half-inactivation of this current occurred at -81.3 mV. The time constant for removal of the inactivation was 17.4 ms. The transient current had a high sensitivity to 4-aminopyridine (4-AP). 4. The sustained current was activated more slowly and was more sensitive to tetraethylammonium (TEA) than the transient current. The sustained current had both Ca2+-dependent and Ca2+-independent components. The Ca2+-dependent portion emerged at potentials of about -35 mV and was activated fully at +10 mV. The Ca2+-independent component was activated at potentials more positive than -40 mV and increased in magnitude with further depolarization. Inactivation of the Ca2+-independent component was voltage dependent. Also, TEA suppressed the Ca2+-independent compound. 5. The transient current in DNLL neurons closely resembled the A current (IA) described for hippocampal and other neurons in both kinetics and pharmacology. The Ca2+-independent component of the sustained current resembled the K current (IK) described for other neurons in both its properties of activation and inactivation and its pharmacology. 6. The outward current of some DNLL neurons was found to contain a dendrotoxin-sensitive component. This component reached its peak at 6.8 ms and had voltage-sensitive time constants of decay of 25.5 and 8.5 ms with voltage steps of 40 and 60 mV, respectively. 7. Application of 4-AP and TEA markedly prolonged the spike width, abolished the fast component of the after hyperpolarization and depolarized the cell membrane. Also, the number of action potentials produced by positive current injection increased under the influence of 4-AP and TEA. Membrane excitability and spike repolarization were dependent on both 4-AP-sensitive transient and TEA-sensitive sustained currents. 8. Neurons in DNLL typically exhibit a steady discharge of action potentials in response to sustained membrane depolarization. The rate and temporal pattern of production of action potentials in these cells are determined by the combination of transient and sustained potassium channels.

Structural analysis of a biologically active echistatin analogue des(46-49)-[Ala8,37]-echistatin gamma with three disulfide bonds by 2D-NMR and computer graphics

An echistatin analogue, designated as des(46-49)-[Ala8,37]-echistatin gamma, was synthesized chemically by solid-phase peptide synthesis. The analogue was made by replacing Cys8 and Cys37 residues with two alanines and the deletion of C-terminal peptide 46-49 of echistatin gamma, resulting in an artificial polypeptide of 45 amino acids with three disulfide bonds. In the platelet aggregation assay, the analogue exhibits almost the same activity as echistatin gamma, indicating that the linear sequence of des(46-49)-[Ala8,37]-echistatin gamma contains all of the primary-structure information that is required for proper folding of this synthetic polypeptide. The tertiary structure of the analogue, as determined from high-resolution nuclear magnetic resonance (NMR) coupled with dynamic simulated annealing, is very similar to that of echistatin alpha1 which differs from echistatin gamma by 8 residues. In particular the two important sites of the Arg-Gly-Asp (RGD) loop and the C-terminal Lys45, both of which show some degree of disorder, are maintained in similar spatial orientation and proximity as those in echistatin alpha 1 even without the constraint provided by the disulfide bond of the (Cys8-Cys37) pair. These results provide new insights in further defining distinct structural features of echistatin gamma, which are involved in supporting the active polypeptide conformation to achieve biological activity in the absence of one pair of disulfide bonds.

In vitro brain slice studies of the rat's dorsal nucleus of the lateral lemniscus. III. synaptic pharmacology

1. The synaptic pharmacology of the dorsal nucleus of the lateral lemniscus (DNLL) of the rat was investigated in a brain slice preparation of the auditory midbrain. The brain slice was cut in the coronal plane and placed in a small recording chamber where warm, oxygenated saline was continuously perfused over and underneath the tissue. Intracellular recordings were made with glass microelectrodes filled with 4 M potassium acetate. Synaptic potentials were elicited by electrical stimulation of the lateral lemniscus or commissure of Probst and pharmacological effects were tested by bath application of amino acid agonists and antagonists. 2. The cells in DNLL were challenged with the excitatory amino acid (EAA) agonists, alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA), N-methyl-D-aspartic acid (NMDA) in 0 Mg2+, and L-glutamate. Each of these caused a depolarization of the cell membrane, a reduction in cell membrane resistance, and the onset of spontaneous firing. 3. Short-latency excitatory postsynaptic potentials (EPSPs) were evoked by stimulation of the lateral lemniscus in 77% of the neurons tested. The mean latency to initial depolarization was 0.9 ms. A single spike with relatively constant latency (mean 1.5 ms) was typically elicited when the strength of lemniscal stimulation was increased. A longer-latency EPSP (mean 2.9 ms) was seen in 34% of the neurons tested either with the slice in normal saline or after pharmacological block of the earlier, short-latency EPSP. The long-latency EPSP was followed by a single spike of multiple spikes with highly variable latencies (range 3.2-24 ms). In 28% of the neurons tested, both early and late EPSPs were observed in response to stimulation of a single location on the lateral lemniscus. 4. Stimulation of the commissure of Probst elicited short-latency EPSPs (mean 0.9 ms) in 37% of the neurons tested. Longer-latency EPSPs (mean 3.0 ms) were found in only 3% of the neurons in response to commissural stimulation. 5. The nonspecific EAA antagonist kynurenic acid blocked both short-and long-latency EPSPs evoked by either lemniscal or commissural stimulation. The non-NMDA antagonist 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX), at very low concentrations, blocked the short-latency EPSPs but had no effect on the longer-latency EPSPs. The short-latency EPSPs were unaffected by the NMDA antagonist D,L-2-amino-5-phosphonovaleric acid (APV). In contrast, the longer-latency EPSPs were blocked by APV, but never by CNQX. 6. DNLL neurons were affected by the inhibitory amino acid agonists gamma-aminobutyric acid (GABA) and glycine. The membrane resistance of the neurons was decreased by GABA and glycine in a solution of either normal or calcium-free saline in a concentration-dependent manner. 7. Inhibitory postsynaptic potentials (IPSPs) were elicited by stimulation of the lateral lemniscus in 53% of the neurons and the commissure of the Probst in 18% of the neurons tested. The mean latencies were 1.0 and 0.9 ms, respectively. The reversal potentials of the IPSPs were around -70 mV. 8. The IPSPs evoked by stimulation of the lateral lemniscus were blocked by the glycine receptor antagonist strychnine, but not by the GABA receptor antagonist bicuculline, whereas the IPSPs elicited by stimulation of the commissure of Probst were blocked by bicuculline but not strychnine.

Conformational study of two linear hexapeptides by two-dimensional NMR and computer-simulated modeling: implication for peptide cyclization in solution

Two linear peptides, D-leucyl-L-prolyl-L-isoleucyl-L-valyl-L-alanyl-beta-alanine (I) and D-leucyl-L-prolyl-L-isoleucyl-L-valyl-N-methyl-L-alanyl-beta-alanine (II), whose sequences were designed from protodestruxin and desmethyldestruxin B by replacing D-leucic acid with D-leucine, two cyclic hexadepsipeptides with insecticidal and immunodepressant activities, have been found to be cyclized in unusually high yields (>85%). In order to gain insight into the conformation and the relative flexibility of different constituent residues in these linear peptides, we have applied various techniques of 2D-NMR spectroscopy coupled with dynamic simulated annealing by computer modeling to establish the solution conformations of these two linear peptides. Based on the derived structures, it is found that the distances between N- and C-terminal residues of both peptides are short enough to facilitate the cyclization, thus collaborating the observation of favorable cyclization yields for both linear peptides.

Conformation of Vespa basalis mastoparan-B in trifluoroethanol-containing aqueous solution

Mastoparan-B, a tetradecapeptide isolated from the venom of the hornet Vespa basalis, belongs to the mastoparan analogs of vespid venom with the lysine residues common for all mastoparan family toxins at positions 4, 11 and 12. Here we use 1H-NMR spectroscopy and hybrid distance geometry-simulated annealing calculation to investigate its three-dimensional structure in trifluoroethanol-containing aqueous solution. The calculated structure shows that residues 3-14 adopt an amphiphilic alpha-helical structure in which the residues with hydrophilic side chains (i.e. Lys-4, Ser-5, Ser-8, Lys-11, Lys-12) are located on one side and the residues with hydrophobic side chains (i.e. Leu-3, Ile-6, Trp-9, Ala-10, Val-13, Leu-14) located on the other side of the molecule. The overall structural features a very similar to the conformation of mastoparan-X reconstituted in vesicle [Wakamatsu et al. (1992) Biochemistry 31, 5654-5660] in spite of the substitutions made for eight residues with distinctly different hydrophobicity. These substitutions lead to a larger hydrophobic moment for the alpha-helical segment and further mobilized N-terminal. This study will help reveal the conformational significance of mastoparan toxins with respect to their potency and activity in G protein regulation.

Determination of three-dimensional solution structure of waglerin I, a toxin from Trimeresurus wagleri, using 2D-NMR and molecular dynamics simulation

The solution conformation of a synthetic snake venom toxin waglerin I, has been determined by using proton nuclear magnetic resonance spectroscopy. By a combination of various two-dimensional NMR techniques, the 1H-NMR spectrum of waglerin I was completely assigned. A set of 247 interproton distance restraints was derived from nuclear Overhauser enhancement (NOE) measurements. These NOE constraints, in addition to the 2 dihedral angle restraints (from coupling constant measurements) and 7 omega torsion angel restraints for prolines, formed the basis of three-dimensional structure determined by molecular dynamics techniques. The 19 structures that were obtained satisfy the experimental restraints, and display small deviation from idealized covalent geometry. Analysis of converged structures indicates that the toxin has no special secondary structure. In the solution structure of waglerin I, the central ring region is well defined but the N- and C-termini possesses more disorder.

Effects of a program on symmetrical posture in patients with hemiplegia: A single-subject design

OBJECTIVES

Asymmetrical posture during static stance has been identified as a common problem in persons with hemiplegia. This study examined the effect of an activity-based therapy regimen on symmetric weight bearing and midline position of center of gravity (COG) in three adult subjects with hemiplegia.

METHOD

An ABAB single-subject design was used. The intervention program, including sanding in front of a standing table and play a bean bag game, was introduced for 30 min each day during each intervention phase. Quantitative measurements of the weight distribution and the midline position of COG were taken with the Balance Master System (version 2.20).

RESULTS

Visual inspection and statistical analysis of the data revealed a significant improvement in symmetric weight distribution and midline position of COG. The study suggests that this program may be a promising alternative to a variety of postural rehabilitation programs for persons with hemiplegia.

CONCLUSION

Insecurity caused by poor stabilization and abnormal reactions to body weight bearing in an antigravity position might contribute to asymmetric postures. Results of this study suggest that an activity-oriented program can be effective in helping the persons with hemiplegia achieve symmetric stances.

Atypical phytochrome gene structure in the green alga Mesotaenium caldariorum

The phytochrome photoreceptor in the green alga Mesotaenium caldariorum is encoded by a small family of highly related genes. DNA sequence analysis of two of the algal phytochrome genes indicates an atypical gene structure with numerous long introns. The two genes, termed mesphy1a and mesphy1b, encode polypeptides which differ by one amino acid in the region of overlap that was sequenced. RT-PCR studies have established the intron-exon junctions of both genes and show that both are expressed. RNA blot analysis indicates a single transcript of ca. 4.1 kb in length. The deduced amino acid sequence of the mesphy1b gene reveals that the photoreceptor consists of 1142 amino acids, with an overall structure similar to other phytochromes. Phylogenetic analyses indicate that the algal phytochrome falls into a distinct subfamily with other lower plant phytochromes. Profile analysis of an internal repeat found within the central hinge region of the phytochrome polypeptide indicates an evolutionary relatedness to the photoactive yellow protein from the purple bacterium Ectothiorhodospira halophila, to several bacterial sensor kinase family members, and to a family of eukaryotic regulatory proteins which includes the period clock (per) and single-minded (sim) gene products of Drosophila. Since mutations which alter phytochrome activity cluster within the region delimited by these direct repeats (P.H. Quail et al., Science 268 (1995): 675-680), this conserved motif may play an important role in the signal transducing function of these disparate protein families.

Conformation of polymyxin B analogs in DMSO from NMR spectra and molecular modeling

The tertiary structures of two polymyxin analogues: [formula: see text] and [formula: see text] in DMSO, from solid-phase peptide synthesis and aerobic oxidation were determined from two-dimensional NMR spectra and distance geometry calculations followed by restrained molecular dynamics simulation. The backbone of peptide I had a rectangular shape stabilized by at least two hydrogen bonds and the hydrophilic side chains of five lysine residues, and the hydrophobic side chains of Phe and Leu resided at both sides to form an amphiphilic molecule. This amphiphilic structure of I is likely to interact with lipid A mainly via a hydrophobic interaction. Compared with I, peptide II, which lacks three N-terminal amino-acid residues, exhibits neither amphiphilic property nor binding ability with lipid A.

A recombinant rice 16.9-kDa heat shock protein can provide thermoprotection in vitro

It is difficult to obtain large amounts of purified low-molecular-mass heat shock proteins (LMM HSPs), which are unique to plants, for biochemical and physiological studies. Therefore, an attempt was made to produce such a HSP by applying recombinant DNA technology. We fused the cDNA for a rice class I 16.9-kDa HSP, pTS1, to the gene for glutathione S-transferase (GST) of Schistosoma japonicum and we obtained large amounts of the fusion protein from transformed Escherichia coli cells. In addition, we found that the 16.9-kDa HSP obtained by cleavage of the recombinant protein could also form a protein complex of approximately 310 kDa under nondenaturing conditions as can the small, native, class I HSPs from heat-shocked rice seedlings. An assay in vitro to examine the thermoprotection of rice soluble proteins from heat denaturation revealed the strong stabilizing effect of the recombinant HSP.

The novel desmethyldestruxin B2, from Metarhizium anisopliae, that suppresses hepatitis B virus surface antigen production in human hepatoma cells

We have examined the antiviral activity of a crude extract prepared from the culture medium of the fungus Metarhizium anisopliae. Eight active destruxins were identified which showed strong suppressive effect on the production of the hepatitis B surface antigen (HBsAg) in human hepatoma Hep3B cells. One new compound, desmethyldestruxin B2 [1], was isolated from M. anisopliae. This structure was determined based on its nmr and mass spectral data.

In vitro brain slice studies of the rat's dorsal nucleus of the lateral lemniscus. II. Physiological properties of biocytin-labeled neurons

1. We made intracellular recordings from neurons in rat dorsal nucleus of the lateral lemniscus (DNLL), determined intrinsic and synaptic physiological properties, and labeled the cells by intracellular injection of biocytin. Biocytin-labeled neurons were reconstructed and classified according to their somatic and dendritic morphology. 2. We identified a diversity of morphological cell types in DNLL. Five main groups of neurons were recognized: multipolar; elongate I, II, and III; and round. The multipolar cells were characterized by several large dendrites with multiple branches that spread over large areas within the DNLL. The dendrites radiated equally in all directions. 3. Elongate cells were characterized by extended cell bodies with polar dendrites. In the case of elongate I and II cells, the dendrites were preferentially oriented in the horizontal plane and the dendritic branches extended across most of the cytoarchitectonic breadth of DNLL from the medial to lateral borders. The classification of elongate II was reserved for a single neuron with profuse dendritic branching that fanned out dorsoventrally along the margins of DNLL. This neuron was unique in our sample and was distinguished from the more common elongate I cells, which had less profuse dorsoventral dendritic branching. Elongate III cells had extended cell bodies, but their dendrites did not extend across the DNLL and showed no preferential orientation. 4. Round neurons had relatively small, round cell bodies and radial dendrites that extended over large areas within DNLL. These cells were quite common in our sample and are almost certainly not the same as the infrequently encountered small round cells found in Nissl-stained sections. Some biocytin-labeled neurons were difficult to classify as either multipolar, elongate I, II, or III, or round. These neurons had properties that most closely resembled elongate III cells, but they were treated separately here to minimize heterogeneity within morphological categories. 5. The intrinsic physiological properties measured in this study were uncorrelated with the morphological class of DNLL neurons. All DNLL neurons had similar current-voltage curves regardless of their anatomic category. Intracellular injection of positive current produced a sustained series of action potentials, the number of which was related to the magnitude of current injection. The interspike intervals were regular, although some cells had a tendency toward an increase or decrease in the length of the interval with prolonged current injection. The interspike intervals were regular, although some cells had a tendency toward an increase or decrease in the length of the interval with prolonged current injection. Injection of negative current produced a hyperpolarization that was proportional to the current strength.(ABSTRACT TRUNCATED AT 400 WORDS)

In vitro brain slice studies of the rat's dorsal nucleus of the lateral lemniscus. I. Membrane and synaptic response properties

1. We examined the physiological properties of neurons in the dorsal nucleus of the lateral lemniscus (DNLL) of the rat in a 400-microns tissue slice taken in the frontal plane through the auditory midbrain. The brain slice was placed in a small chamber and was perfused fully submerged in a warm, continuously circulating oxygenated saline solution. We made intracellular recordings with glass pipettes filled with 4 M potassium acetate. Synaptic potentials were evoked by electrical stimulation of either the lateral lemniscus or the commissure of Probst. 2. We tested the membrane characteristics of DNLL neurons by recording the electrical potentials produced by intracellular injection of positive or negative current. Typically, DNLL neurons had nearly linear current-voltage curves and responded to depolarizing currents with a sustained train of action potentials. Injection of intense or prolonged depolarizing currents frequently resulted in a pronounced afterhyperpolarization of the cell membrane. Intense hyperpolarizing currents were often followed by a large rebound depolarization. 3. The action potentials of most DNLL neurons were characterized by a double undershoot, i.e., the initial hyperpolarization after a spike was followed by a second, longer-latency hyperpolarization. Seventy-nine percent of the cells recorded had this type of double undershoot. The remaining cells had a single undershoot in which the postspike hyperpolarization was followed by a steady return to resting potential without any indication of a second phase of hyperpolarization. 4. Electrical stimulation of the lateral lemniscus evoked both excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) in DNLL. The EPSPs were evoked alone without any evidence of an IPSP in 67% of neurons and IPSPs were evoked alone in 6% of the neurons from which recordings were made. In 27% of the recordings both EPSPs and IPSPs were elicited in the same neuron by stimulation of a single location on the lateral lemniscus. 5. The combined EPSPs and IPSPs produced by lemniscal stimulation could often be dissociated by their different thresholds and/or different response latencies. For 35% of the neurons in which both an EPSP and IPSP were present, the IPSP had a lower threshold; for 23% of the cells, the EPSP had a lower threshold. For the remaining cells the thresholds for producing an EPSP and IPSP were the same. 6. DNLL neurons were capable of responding with great fidelity to a single pulse of stimulation delivered to the lateral lemniscus, i.e., an action potential was evoked after every stimulus.(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibition in the superior olivary complex: pharmacological evidence from mouse brain slice

1. The effects of gamma-aminobutyric acid (GABA) and glycine and their respective antagonists were determined for neurons in the mouse superior olivary complex. Brain slices (400 microns) were cut in the frontal plane and maintained in an oxygenated saline solution for physiological recording. Recordings were made from neurons in the lateral superior olive (LSO) or medial nucleus of the trapezoid body (MNTB) with glass micropipettes filled with 4 M potassium acetate. 2. Ipsilateral and contralateral synaptic responses were elicited by applying current pulses to the trapezoid body through bipolar stimulating electrodes located at positions lateral and medial to the olivary complex. Both intracellular and extracellular recordings were studied before, during, and after application of drugs to the saline bath containing the tissue slice. 3. Intracellular recordings from 10 neurons in LSO showed that GABA (1-10 mM) caused a concentration-dependent drop in membrane resistance and either reduced or blocked postsynaptic excitatory responses. Similar effects were found in five cells tested with glycine (1-10 mM). Three neurons tested with both GABA and glycine were affected by both drugs. Extracellular spikes were blocked in 53 out of 67 LSO neurons tested with GABA and 29 out of 35 neurons tested with glycine. Seventeen out of 23 neurons tested with both GABA and glycine were affected by both. 4. GABA had a powerful blocking effect on extracellularly recorded action potentials evoked by current-pulse stimulation of the trapezoid body in seven LSO neurons tested after adding the glycine receptor antagonist, strychnine (1 microM), to the bath. GABA also lowered the membrane resistance of one LSO neuron in which intracellular recordings were made in the presence of strychnine. 5. Neurons in MNTB also were affected by GABA and glycine but the proportion of sensitive cells was less than in LSO. GABA reduced membrane resistance in 6 out of 16 neurons and glycine produced a similar effect in 14 out of 26 neurons from which intracellular recordings were made. Six out of 14 neurons tested with GABA and glycine responded to both. Extracellular spikes were eliminated or reduced in amplitude by GABA in 15 out of 44 cells and by glycine in 40 out of 68 cells tested. Eleven out of 29 cells from which extracellular recordings were made were affected by both. 6. The glycine antagonist, strychnine (0.25 - 1.0 muM), blocked both ipsilateral and contralateral inhibitory postsynaptic potentials (IPSPs) in LSO.(ABSTRACT TRUNCATED AT 400 WORDS)

Modulatory effects of eicosanoids on mesangial cell growth in response to immune injury

In a rat model of glomerular mesangial cell immune injury induced by a monoclonal antibody (ER4) against the mesangial cell membrane antigen Thy 1.1 and in which mesangial cell proliferation is a prominent feature, we examined the role of arachidonate 5- and 12-lipoxygenation (LO) eicosanoids and of thromboxane (Tx) in modulating the proliferative response. Significant increments in glomerular cell proliferation, assessed by counting glomerular cells positive for the Proliferating Cell Nuclear Antigen (PCNA) and by the incorporation of [3H]thymidine ([3H]TdR) in mesangial cell outgrowths from explanted glomeruli, occurred during the mesangioproliferative phase of injury. This event was abrogated in animals depleted of leukocytes or platelets prior to administration of ER4 and in animals pretreated with the arachidonate 5-LO inhibitor MK886. Pretreatment with the Tx synthase inhibitor, Furegrelate, or the arachidonate 12-LO inhibitor, Baicalein, had no effect, indicating that eicosanoids of arachidonate 5-LO but not those of 12-LO or Tx modulate mesangial cell proliferation following immune injury. We further identified those 5-lipoxygenation eicosanoids with growth modulatory effects on cultured mesangial cells. Leukotriene (LT)C4 and D4 but not LTB4 or 5-hydroxyeicosatetraenoic (HETE) acid enhanced [3H]TdR incorporation in growth-arrested mesangial cells. This effect of LTC4 and LTD4 was abrogated by the specific protein kinase C (PKC) inhibitor calphostin C, indicating a PKC-dependent mechanism. LTC4 and LTD4 but not 5-HETE or LTB4 also increased mesangial cell mass levels of the endogenous PKC activator diacylglycerol. The observations indicate that leukocyte-derived arachidonate 5-LO eicosanoids modulate mesangial cell proliferation following immune injury. Of these LTC4 and LTD4 are the likely candidates as they promote mesangial cell growth via a PKC-dependent mechanisms.

Chemical synthesis of gamma-echistatin analogues: elucidation of status of C-terminal (45-49)

Three analogues of gamma-echistatin, des(45-49)-gamma-echistatin, des(46-49)-gamma-echistatin and des(47-49)-gamma-echistatin, were synthesized by solid-phase methodology and their biological activities were measured and compared. The results reveal that without the C-terminal (45-49) of gamma-echistatin, the folding of the protein to the final active structure is not interfered with and Lys-45 influences the inhibition of platelet aggregation.

Isolation of a cDNA encoding a 70 kDa heat-shock cognate protein expressed in vegetative tissues of Arabidopsis thaliana

A cDNA encoding a 70 kDa heat shock 'cognate' protein (hsc70) was isolated from Arabidopsis thaliana by using a rat hsc70 cDNA as probe. Sequence analysis demonstrated the conservation of functional domains and important amino acid residues among hsc70s in plants and animals. The expression of this gene was stress-inducible, and was found at a substantial level during normal growth in root, stem, leaf and flower tissues, but not in siliques. Multiple copies of this gene exist in the Arabidopsis genome.

[Chemical constituents of Rabdosia nervosa (Hemsl) C.Y. Wu et H. W. Li]

Three compounds were isolated from the stems and leaves of Rabdosa nervosa. On the basis of spectral analysis their structures were elucidated as lasiokaurin, ponicidin and oridonin respectively. These compounds were obtained from R. nervosa for the first time.

Physiological evidence for ipsilateral inhibition in the lateral superior olive: synaptic responses in mouse brain slice

The incidence of ipsilateral inhibition in the lateral superior olive (LSO) was examined in a brain slice preparation of the mouse superior olivary complex. A 400 microns brain slice was taken in the frontal plane and maintained in a warm, oxygenated saline solution. Intracellular recordings were made from the LSO with micropipettes filled with 4 M potassium acetate. Synaptic responses were elicited by electrical stimulation of the trapezoid body in different slices at various locations between the cochlear nucleus and the ipsilateral superior olivary complex (SOC). The results show that ipsilateral stimulation can evoke inhibitory as well as excitatory postsynaptic potentials. The ipsilateral IPSPs have short latencies and are elicited by stimulation of the trapezoid body at any point along its course between cochlear nucleus and LSO. Short-latency IPSPs can also be produced by direct stimulation of the ventral cochlear nucleus itself. Ipsilateral IPSPs are blocked by low concentrations of the glycine antagonist, strychnine. In addition, bath application of sodium pentobarbital in one case eliminated ipsilateral IPSPs without eliminating EPSPs. The results suggest that there is a rapidly conducting, glycinergic pathway from cochlear nucleus through the trapezoid body to the LSO on the same side of the brain. This pathway is probably served by either a direct projection from the ventral cochlear nucleus to the LSO or an indirect one from cochlear nucleus to LSO through the lateral nucleus of the trapezoid body (LNTB).

D-Aminoacylase from Alcaligenes faecalis possesses novel activities on D-methionine

D-Aminoacylase isolated from Alcaligenes faecalis DA1 has a great potential for future application in D-amino acids production. This paper reports for the first time that D-aminoacylase can reverse the catalysis direction on D-Met and deacylate N-Ac-D-Met-OMe and N-Ac-D-Met-Gly. The results provide important insights regarding the binding and affinity of substrates to the active site of this enzyme. Based on a systematic study of kinetic properties and relative reactivities for a broad range of substrates, a model to elucidate the reaction mechanism is proposed.