Chemical characterization and toxicity of dihydro derivatives of nodularin and microcystin-LR, potent cyanobacterial cyclic peptide hepatotoxins

Dihydro derivatives of nodularin (1) and microcystin-LR (4), potent cyclic peptide hepatotoxins isolated from Nodularia spumigena and Microcystis aeruginosa, respectively, were prepared by sodium borohydride reduction of the dehydroamino acid residues. The two stereoisomers of both dihydronodularin (2 and 3) and dihydromicrocystin-LR (5 and 6), isolated by reversed-phase HPLC, showed similar toxicity to each other [ip in mice, LD50 = 150 (2), 150 (3), 85 (5), and 100 (6) micrograms/kg]. The stereochemistries of the reduced amino acids obtained by acid hydrolysis of dihydronodularin and dihydromicrocystin-LR [respectively, alpha-(methylamino)butyric acid and N-methylalanine] were determined by GC on a permethylated beta-cyclodextrin capillary column as their trifluoroacetyl methyl ester derivatives. Authentic L- and DL-N-methylamino acids were prepared to compare directly with the natural amino acids. Deuterated derivatives were also prepared using sodium borodeuteride (98 atom % D), and the location (beta) and percentage (78-84%) of the deuterium incorporation were determined.

Glucokinase mutations associated with non-insulin-dependent (type 2) diabetes mellitus have decreased enzymatic activity: implications for structure/function relationships

The glycolytic enzyme glucokinase plays an important role in the regulation of insulin secretion and recent studies have shown that mutations in the human glucokinase gene are a common cause of an autosomal dominant form of non-insulin-dependent (type 2) diabetes mellitus (NIDDM) that has an onset often during childhood. The majority of the mutations that have been identified are missense mutations that result in the synthesis of a glucokinase molecule with an altered amino acid sequence. To characterize the effect of these mutations on the catalytic properties of human beta-cell glucokinase, we have expressed native and mutant forms of this protein in Escherichia coli. All of the missense mutations show changes in enzyme activity including a decrease in Vmax and/or increase in Km for glucose. Using a model for the three-dimensional structure of human glucokinase based on the crystal structure of the related enzyme yeast hexokinase B, the mutations map primarily to two regions of the protein. One group of mutations is located in the active site cleft separating the two domains of the enzyme as well as in surface loops leading into this cleft. These mutations usually result in large reductions in enzyme activity. The second group of mutations is located far from the active site in a region that is predicted to undergo a substrate-induced conformational change that results in closure of the active site cleft. These mutations show a small approximately 2-fold reduction in Vmax and a 5- to 10-fold increase in Km for glucose. The characterization of mutations in glucokinase that are associated with a distinct and readily recognizable form of NIDDM has led to the identification of key amino acids involved in glucokinase catalysis and localized functionally important regions of the glucokinase molecule.

Heterogeneous response to calcium by individual parathyroid cells

Classical stimulus-secretion theory suggests that each individual cell responds to a given stimulus. We tested this theory by determining the response of single bovine parathyroid cells to calcium with the reverse hemolytic plaque assay (RHPA), an assay that measures hormone release from individual cells. As calcium concentrations decreased, the amount of parathyroid hormone (PTH) released per cell increased, and cells were recruited to release PTH. To confirm that adequate stores of PTH were present, immunocytochemistry and in situ hybridization were performed. To test if cells that did not release PTH were capable of secretion, we performed a sequential RHPA; 47.8% of cells did not release PTH after the first stimulus. After the second exposure to low concentrations of calcium, 26.5% of these "nonsecretory" cells were able to release PTH. We conclude that parathyroid cells are homogeneous for PTH content and synthetic capability. Parathyroid cells respond to changes in extracellular calcium heterogeneously in that more PTH per cell is released, and individual parathyroid cells are "recruited" to release PTH at low calcium concentrations. In addition, parathyroid cells can be induced to secrete suggesting that cells are viable but in a depressed secretory state. Parathyroid cells may exist in an "on" or "off" secretory state.

Organometallic products from the reaction of the isoelectronic Mn(CO)5− and Cr(CO)4NO− metallate anions with bis-α-bromocyclopropyl ketone

Mn(CO)5− and Cr(CO)4NO− react with the title ketone to give organometallic products. In the chromium case, a single metallofuran product is produced. In the manganese reaction, one can isolate a series of four complexes, two of which have a structure closely related to the chromium complex. The other two complexes are assigned an acyl manganese structure. The structures of the chromium complex and one of the acyl manganese complexes have been determined by X-ray methods. One finds a distorted octahedral bonding about the metal atom in each case. The chromium complex has bond lengths very similar to those reported for a closely related manganese structure, implying a delocalization of electrons within a metallofuran ring. As expected for this mixed carbonyl nitrosyl complex, the nitrosyl group is positioned trans to the oxide bond, representing the weakest and strongest "trans-effect" substituents. The acyl manganese structures contain an Mn(CO)4 unit in contrast to the usual Mn(CO)5 acyl complexes, with the 18e− count being provided by an internal chelation with the n-electrons of the dicyclopropyl ketone group. The reaction mechanism for the formation of the complexes is postulated to involve initial bromine abstraction (two-electron reduction) by the metallate anion, with the Cr(CO)4NO− reaction being much faster compared to Mn(CO)5−. The resulting organic enolate then "back-reacts" with a carbonyl group of the just-formed metal carbonyl bromide to form a transient anionic Fischer carbene complex. Ultimately this intermediate loses the metal bromide ion with the formation of the neutral complexes.

Isolation and structures of microcystins from a cyanobacterial water bloom (Finland)

A hepatotoxic cyanobacterial (blue-green algal) water bloom was collected from a constructed water reservoir in Finland. The water bloom contained two cyanobacterial species, Microcystis aeruginosa and Aphanizomenon flos-aquae. Two hepatotoxins, 1 and 2, were isolated from extracts of lyophilized cells. The structures of 1 and 2 were assigned based upon their amino acid analyses on a Waters Pico Tag HPLC system and a chiral GC capillary column (Chirasil Val III), fast atom bombardment mass spectrometry (FABMS), high resolution FABMS, and tandem FABMS data. Toxin 1 was identical to a previously reported compound, [D-Asp3]microcystin-RR. Toxin 2 was new and was assigned the structure [D-Asp3]microcystin-YR.

Two new L-serine variants of microcystins-LR and -RR from Anabaena sp. strains 202 A1 and 202 A2

Two new microcystins, [L-Ser7]microcystin-LR (1) and [L-Ser7]microcystin-RR (2), were isolated from a filamentous fresh water cyanobacterium (blue-green alga), Anabaena sp. strain 202 A1, along with the two major toxins, [Dha7]microcystin-LR (3) and [Dha7]microcystin-RR (4) and their minor components the D-Asp variants [D-Asp3,Dha7]microcystin-LR (5) and [D-Asp3,Dha7]microcystin-RR (6). Anabaena sp. strain 202 A1 also produced another new toxin, whose structure is tentatively proposed as [D-Asp3,L-Ser7]microcystin-XR (7), where X is a leucine homologue. Anabaena sp. strain 202 A2 produced one new microcystin, 1, and three known microcystins, 3, 4, and 5. The structures of the toxins were assigned based on their amino acid analyses, and fast atom bombardment mass spectrometry data.

[A new virus of rabbit. III. Study on morphological superstructure and antigenicity of rabbit hemorrhagic disease virus (RHDV)]

In the spring 1986, an acute infectious disease occurred in Wuhan Second Producing Medical Manufactory, and the rabbit almost died. We tested the mortal symptom and confirmed rabbit Hemorrhagic Disease (RHD) as same as Huang Yinyao report. Hubei Traditional Chinese Medicine Institute appear this RHD also. After we purified virus of above two source by low speed, high speed and sucrose density gradient centrifugation, they can react with antiserum of RHDV from Nanjing Agricultural University in agar gel immunodiffusion tests. These results proved that they belong to the same serotype. Data indicate RHDV have difference morphological superstructure, viral polypeptides and especially RHDV can't react with antiserum of standard Parvovirus of rabbit and so on, so we suggest RHDV is a new virus.

Isolation and characterization of a variety of microcystins from seven strains of the cyanobacterial genus Anabaena

Hepatotoxins (microcystins) from seven freshwater Anabaena strains originating from three different Finnish lakes and one lake in Norway were isolated by high-performance liquid chromatography and characterized by amino acid analysis and fast atom bombardment mass spectrometry. All strains produced three to seven different microcystins. A total of 17 different compounds were isolated, of which 8 were known microcystins. The known compounds identified from six strains were MCYST (microcystin)-LR, [D-Asp3]MCYST-LR, [Dha7]MCYST-LR, [D-Asp3,Dha7]MCYST-LR, MCYST-RR, [D-Asp3]MCYST-RR, [Dha7]MCYST-RR, and [D-Asp3,Dha7]MCYST-RR. With the exception of MCYST-LR and [D-Asp3]MCYST-LR, this is the first time that isolation of these toxins from Anabaena strains has been reported. Three of the strains produced one to three toxins as minor components which could not be identified. Anabaena sp. strain 66 produced four unidentified toxins. The other Anabaena strains always contained both MCYST-LR and MCYST-RR and/or their demethyl variants. Quantitative differences between toxins within and between strains were detected; at times MCYST-LR and at other times MCYST-RR or demethyl derivatives thereof were the most abundant toxins found in a strain.

[A new virus of rabbit. II. Study on morphological structure and some physicochemical properties of a strain of rabbit hemorrhagic disease virus]

In this paper a strain of Rabbit Hemorrhagic Disease Virus (RHDV) was isolated and purified from the diseased rabbit livers with a method of using chloroform, two-phase of polyethylene-glycol-dextran sulfate sodium and sucrose density gradient centrifugation. Purified virus was nonenveloped, icosahedeal symmetry with a triangulation number of 3, and 33-37 nm in diameter. The capsid was composed of 32 capsomeres with central holes in an outer diameter of about 9nm. Two types of viral particles having different sedimentation coefficient, 130s and 166s could be identified after sucrose density gradient centrifugation. Probably no less than four virion proteins with molecular weight of 66.4, 65.0, 63.5, 41.0 x 10(3) dalton were detected by SDS-polyacrylamide gel electrophoresis. Viral nucleic acid was extracted from purified virus by using SDS-proteinase K-phenol. Tests with diphenylamine, formaldehyde, and staining with acridine orange as well as the curves of thermal denaturation showed that this kind of virus had a single-stranded DNA. The molecular weight of the ssDNA was approx 2.1 x 10(6) dalton as determined by electron microscopy. Data indicate that the RHDV may like the parvovirus of the family Parvoviridae.

Degenerate oligonucleotide primers for enzymatic amplification of recA sequences from gram-positive bacteria and mycoplasmas

RecA protein in gram-negative bacteria, especially in Escherichia coli, has been extensively studied, but little is known about this key enzyme in other procaryotes. Described here are degenerate oligonucleotide primers that have been used to amplify by the polymerase chain reaction (PCR) recA sequences from several gram-positive bacteria and mycoplasmas. The DNA sequences of recA PCR products from Streptococcus pyogenes, Streptococcus mutans, Enterococcus faecalis, and Mycoplasma pulmonis were determined and compared. These data indicate that the M. pulmonis recA gene has diverged significantly from recA genes of other eubacteria. It should be possible to use cloned recA PCR products to construct recA mutants, thereby providing the means of elucidating homologous genetic recombination and DNA repair activities in these organisms.

Close linkage of glucokinase locus on chromosome 7p to early-onset non-insulin-dependent diabetes mellitus

Non-insulin-dependent diabetes mellitus (NIDDM) is a major health problem, affecting 5% of the world population. Genetic factors are important in NIDDM, but the mechanisms leading to glucose intolerance are unknown. Genetic linkage has been investigated in multigeneration families to localize, and ultimately identify, the gene(s) predisposing to NIDDM. Here we report linkage between the glucokinase locus on chromosome 7p and diabetes in 16 French families with maturity-onset diabetes of the young, a form of NIDDM characterized by monogenic autosomal dominant transmission and early age of onset. Statistical evidence of genetic heterogeneity was significant, with an estimated 45-95% of the 16 families showing linkage to glucokinase. Because glucokinase is a key enzyme of blood glucose homeostasis, these results are evidence that a gene involved in glucose metabolism could be implicated in the pathogenesis of NIDDM.

Prophylactic and therapeutic effects of acupuncture on simple obesity complicated by cardiovascular diseases

In order to understand the prophylactic-therapeutic effects of acupuncture and moxibustion in simple obesity complicated by cardiovascular diseases, we have observed in 102 cases the changes of pathogenetic and hazardous factors and the regulating function of vegetative nerves on cardiovascular activities. The results showed that the therapeutic effect of acupuncture and moxibustion was good with a total effective rate of 88.24%. At the same time, acupuncture and moxibustion were found to have a benign conversion effect on the loin hip ratio (the pathogenetic factor), the arteriosclerotic index (the hazardous factor), and the vegetative nerve function of regulating the heart and blood vessels (the equilibrium indices of the vegetative nervous system). All this suggests that acupuncture is a treatment of choice for obesity and an important method of preventing and treating complicating cardiovascular diseases.

Frequency analysis of accommodation: single sinusoids

We present an experimental frequency analysis of a neurological control system, the accommodation system, using single sinusoids. Also, by means of continual experimental calibration full coverage of one subject's dynamic range, we demonstrate an AC nonlinearity saturation, which probably lies in the motor-response portion of the system; in contrast to the switching-mode nonlinearity, which probably lies in the sensory-processing portion. We offer our findings as a basis for further models. In addition, our results can be compared with studies using multiple sinusoids and transients to document how the different aspects of the accommodation system are realized given their different input conditions.

[Effects of l-tetrahydropalmatine on isolated rabbit arterial strips]

The effects of l-tetrahydropalmatine (THP) on isolated rabbit aortic, renal and superior mesenteric arterial strips were studied in comparison with verapamil (Ver). THP and Ver shifted the KCl, CaCl2, norepinephrine (NE) and 15-methyl prostaglandin F2 alpha dose-response curves to the right in a non-parallel fashion, and decreased the maximal response, showing noncompetitive antagonism. THP was less potent in dilating arterial strips than Ver. THP and Ver obviously inhibited the intracellular Ca2+-dependent component of NE-induced contraction of the aorta, but only slightly decreased the extracellular Ca2+-dependent component when the concentration of THP or Ver was very high (THP 0.1 mmol/L, Ver 10 mumol/L). The results suggest that THP, similar to Ver, mainly inhibits potential-operated calcium channels. THP and Ver were more potent in dilating renal and superior mesenteric arterial strips than aortic strips. The results indicate that the vasodilation effect of THP is similar to that of Ver and that THP probably has a calcium antagonistic effect.

Human pupillary response to ramp changes in light intensity

The dynamic behavior of the pupillary system was explored using different velocity ramp changes in light intensity. Ramp stimuli ranged in velocity from 0.02 to 8.00 log units/s and the responses were recorded from three subjects. For ramp velocity below 0.066 log units/s, the responses were mainly ramps. Above 1.0 log units/s ramp velocity, the responses were mostly steps. In the stimulus velocity range of 0.066 to 1.0 log units/s, the primary responses were step-ramps. The amplitudes of the initial step movement in step-ramp responses were found to be proportional to stimulus ramp velocity. Thus the pupillary system appears either to convert the total energy in a time interval or the rate of change of intensity of the ramp stimulus into a step signal for driving the pupillary plant output.

Dynamics of accommodation: measurements for clinical application

Accommodation dynamics have not been used in clinical diagnosis as have eye movement and pupillary dynamics; the difficulty of clinical observation is matched by limitations in measurement methods. An instrument suitable for clinical use is described that allows measurement of step response latencies and especially time constants. With computer analysis, phase plane trajectories, and noise spectra can be quickly obtained also. The utility of these dynamical parameters for clinical diagnosis is illustrated by a study of changes of time constants with age in prepresbyopia.

Prostaglandin formation in the isolated human ductus arteriosus, aorta, pulmonary and umbilical arteries

The prostaglandins comprise a large family of substances that includes primary prostaglandins, prostacyclin and thromboxane, all of which exhibit some vascular activity. The activity of each prostaglandin may be species - and organ - dependent, and the type of prostaglandin produced in a tissue is often dependent on the presence of terminal enzyme systems in that tissue. The prostaglandin endoperoxide PGH2 serves as a common intermediate for the enzymatic production of prostaglandins, thromboxanes and prostacyclin. We have obtained information on the biosynthesis of these compounds by the human ductus arteriosus, aorta, pulmonary and umbilical arteries in vitro. Vascular tissue samples were obtained from two fetuses of 16 to 18 weeks of gestation, two newborns of 26 and 35 weeks of gestation and in nine term infants. The vascular tissue samples were incubated with [1-14C]-arachidonic acid and/or [1-14C]-prostaglandin endoperoxide (PGH2). The study demonstrates the formation of prostaglandins and prostacyclins from all the vascular tissues and the formation of thromboxanes from the umbilical artery. The study implies that the above vessels contain "prostaglandin synthetase" enzymes as early as 16 weeks of gestation.

Dynamic pupillary response controlled by the pupil size effect

Pupillary escape has been described as an initial contraction followed by a slow redilatation, occurring in response to a step stimulus of low-intensity light. When the initial pupil size is small, the response to the same step stimulus is pupillary capture, a steady and sustained contraction. In this experiment a comparison was made between three modes of controlling pupil size and thereby of regulating the pupillary response: contralateral light background level, ipsilateral light background level, and accommodative level with which there is no change in retinal adaptation. All three level setting modes showed similar results in illustrating the pupil size effect. In addition, an inhibitory effect was found with both ipsilateral and contralateral light backgrounds that is independent of Weber's Law in the contralateral case. Our results lead to the formulation of a binocular model, featuring an internal parameter control whereby a signal dependent on the static pupil size regulates the gains of the parallel phasic and tonic pathways, the former responsive to transient changes of light, and the latter to background levels of light and accommodative levels. Our findings also raise interesting questions concerning the loci of these complex interactions in the simple neuroanatomy of the pupillary pathways.

Human airway monohydroxyeicosatetraenoic acid generation and mucus release

The effects of 5-, 8-, 9-, 11-, 12-, and 15-monohydroxyeicosatetraenoic acid (HETE) (0.1-100 nM) on mucous glycoprotein release from cultured human airways were determined. Each of the HETE was an active secretagogue of mucus at concentrations greater than 1-10 nM with 12- and 15-HETE, the most active. Both 5- and 9-hydroperoxyeicosatetraenoic acid (HPETE) were also active as secretagogues at 100 nM, although of somewhat lower potency. As cultured airways were capable of responding to HETE with mucous glycoprotein release, it was of interest to identify and quantitate airway HETE formation. Accordingly, airways were incubated with tracer quantities of [14C]arachidonate for 16-48 h, and the spontaneous formation of 5-, 12- and 11- and/or 15-HETE was measured by high-pressure liquid chromatography. Indeed, sizeable quantities of 11- and/or 15- greater than 5- greater than 12-HETE were generated. This HETE generation was increased by the addition of 25 micrograms/ml of arachidonate and was reduced somewhat after 18-21 d in continuous tissue culture. Reversed anaphylaxis of human airways using anti-human IgE markedly increased the HETE formation, resulting in the production of micromolar concentrations of 5- and 11- and/or 15-HETE. Thus, human airways not only are capable of responding to the presence of HETE with mucous glycoprotein release, but also generate (both spontaneously and in response to anaphylaxis) at least three species of HETE, and do so in quantities capable of acting as mucus secretagogues.

A systems model for the pupil size effect. I. Transient data

The human pupillary control system is a paradigm for linearized biological control systems. It also exhibits a series of interesting nonlinear behaviors, particularly asymmetry, "pupillary escape," and "pupillary capture." We present a nonlinear model in which a signal dependent upon pupil size is fed back internally to cause a change in system parameters related to gains and rates of light adaptation. The model was simulated on a digital computer, a variety of experimental data was well matched, and improvements over previous pupil models demonstrated. A candidate physiological mechanism for adaptive components of the model might have the form of an inverse "Henneman coded" neuronal pool.

Pupillary escape intensified by large pupillary size

Pupil responses to light are greatly influenced by initial pupil size. Small pupils, operating under photopic conditions, show tonic responses to step increases of light and high gains; thus the pupil is a good regulator of light. Large pupils, operating under mesopic or scotopic conditions show phasic responses, "pupillary escape", and smaller gains; the pupil only transiently influences retinal flux. By using accommodation level to set the size of the pupil, the mechanism of the "pupil size effect" is shown to be dependent on retinal light level only so far as retinal activity sets pupil size.

Lipoxygenase activity in rat kidney glomeruli, glomerular epithelial cells, and cortical tubules

We examined the possibility that renal glomerular and cortical tubular tissue has lipoxygenase activity in addition to the well established cyclo-oxygenase pathway of arachidonic acid metabolism. Homogenized rat kidney glomeruli, in the presence of meclofenamate (33 microM) and divalent cation ionophore A23187 (3 microM), metabolized octatritiated arachidonic acid to 12-hydroxyeicosatetraenoic acid and lesser amounts of 80 and/or 9-hydroxyeicosatetraenoic acid. These products were identified by thin layer chromatography, high performance liquid chromatography, and gas chromatography-mass spectroscopy. In order to rule out the synthesis of hydroxylated fatty acids by platelets and leukocytes entrapped in the glomeruli, we studied lipoxygenase products in glomerular epithelial cells after 9 days in cell culture. Homogenized glomerular epithelial cells converted octatritiated arachidonic acid to 12-hydroxyeicosatetraenoic acid solely. The lipoxygenase activity in cortical tubules was substantially less than in glomeruli and only 12-hydroxyeicosatetraenoic acid was synthesized. The production of hydroxyeicosatetraenoic acid by lipoxygenase inhibitors, nordihydroguaiaretic acid, 5,-homogenized glomeruli, glomerular epithelial cells, and cortical tubules was inhibited by three 8,11,14-eicosatetraynoic acid, and 1-phenyl-3-pyrazolidone. These data demonstrate that there is lipoxygenase activity in rat kidney glomeruli, glomerular epithelial cells and to a lesser extent cortical tubules, and may imply a role of the lipoxygenase products in the regulation of normal glomerular function and inflammatory disease of the kidney.

9,11-Iminoepoxyprosta-5,13-dienoic acid is a selective thromboxane A2 synthetase inhibitor

9,11-Iminoepoxyprosta-5,13-dienoic acid inhibits the thromboxane A2 synthetase in platelet and lung microsomal enzyme preparations and in intact platelets. It does not inhibit the protaglandin I2 synthetase in aorta or lung microsomes and intact Balb 3T3 fibroblasts. In lung microsomes, which contain both enzymes, 9,11-iminoepoxyprosta-5,13-dienoic acid inhibits only thromboxane A2 formation and augments prostaglandin I2 formation. This inhibitor is more selective than other reported prostaglandin endoperoxide analogs which inhibit the platelet thromboxane synthetase.