Two-kidney, two clip renovascular hypertensive rats can be used as stroke-prone rats

BACKGROUND AND PURPOSE

The cerebrovascular lesions in stroke-prone spontaneously hypertensive rats are not only dependent on high blood pressure but partly related to pressure-independent genetic factors. The aim of the present study was to observe whether spontaneous stroke occurred in renovascular hypertensive rats without a genetic deficiency.

METHODS

The 1-kidney, 1 clip (1k1c); 2-kidney, 1 clip (2k1c); and 2-kidney, 2 clip (2k2c) methods were used to induce hypertension in male Sprague-Dawley rats with a ring-shaped silver clip. Sham-operated rats were used as controls. Blood pressure and neurological symptoms were observed in the rats without any artificial inducement. Brain sections stained with hematoxylin-eosin and phosphotungstic acid-hematoxylin were examined under a microscope to determine stroke foci.

RESULTS

The attack rate of stable hypertension was 100% (55/55) in the 2k2c group, which was significantly higher than that in the 1k1c (23/30, 76.7%) and 2k1c (21/30, 70%) groups (P<0.01). None of the rats in the 2k2c group died of acute renal failure or suffered from diffuse cerebral lesions postoperatively. Forty weeks after renal artery constriction, the incidence of spontaneous stroke in the 2k2c group was 61.8% (34/55), which was significant higher than that in the 1k1c (7/30, 23.3%) and 2k1c (5/30,16.7%) groups (P<0.01). Stroke foci were not observed in normotensive controls.

CONCLUSIONS

We conclude that 2k2c renovascular hypertensive rats with proper renal artery constriction can be used as stroke-prone renovascular hypertensive rats independent of a genetic deficiency.

[Study on the determination of tung oil adulterated in vegetable oils by first derivative spectrophotometry]

A method of first derivative spectrophotometry for qualitative and quantitative analysis of tung oil adulterated in vegetable oils, including peanut oil, bean oil, rape seed oil, tea seed oil, palm oil and mixed vegetable oil, was established. The spectrum of tung oil features three valleys at 291.3, 278.3 and 266.4nm, and three peaks at 284.1, 271.5 and 260.7nm. At 291.3nm, the coefficient (deltaE(1%)1cm/deltalambda) was -1.03 x 10(3). When the concentration of tung oil adulterated in vegetable oils was downed to 0.1%, the above specialities still remain and the changes in wavelengths were not more than 0.7nm. The detection limit of the concentration of tung oil adulterated in vegetable oils was lower than 0.1%.

Characterization of the p125 subunit of human DNA polymerase delta and its deletion mutants. Interaction with cyclin-dependent kinase-cyclins

The catalytic subunit of human DNA polymerase (pol) delta was overexpressed in an active, soluble form by the use of a baculovirus system in insect cells. The recombinant enzyme was separated from endogenous DNA polymerases by phosphocellulose, Mono Q-Sepharose, and single-stranded DNA-cellulose chromatography. Recombinant DNA pol delta was also purified by immunoaffinity chromatography. The enzymatic properties of the purified catalytic subunit were characterized. The enzyme was active and possessed both DNA polymerase and associated 3' to 5' exonuclease activities. NH2-terminal deletion mutants retained polymerase activity, whereas the core and COOH-terminal deletion mutants were devoid of any measurable activities. Coinfection of Sf9 cells with recombinant baculovirus vectors for pol delta and cyclin-dependent kinase (cdk)-cyclins followed by metabolic labeling with 32Pi showed that the recombinant catalytic subunit of pol delta could be hyperphosphorylated by G1 phase-specific cdk-cyclins. When cdk2 was coexpressed with pol delta in Sf9 cells, pol delta was found to coimmunoprecipitate with antibodies against cdk2. Experiments with deletion mutants of pol delta showed that the NH2-terminal region was essential for this interaction. Coimmunoprecipitation and Western blot experiments in Molt 4 cells confirmed the interaction in vivo. Preliminary experiments showed that phosphorylation of the catalytic subunit of pol delta by cdk2-cyclins had little or no effect on the specific activity of the enzyme.

Pleiotropic Effects of Small Peptides Corresponding in Sequence to the Cytoplasmic Domain of the Influenza Virus Haemagglutinin on Influenza, Vesicular Stomatitis and Sindbis Viruses

Studies on the antiviral effects of short peptides of six to 10 amino acids that correspond in sequence to the cytoplasmic domains of enveloped virus transmembrane glycoproteins have been extended to include additional kinds of assay in order to determine a site for inhibition of virus replication. Based on these experiments, the antiviral activity previously described for a decapeptide with the influenza virus haemagglutinin HA2C-terminal sequence was not specific for influenza virus and the integrity of newly released, extracellular vesicular stomatitis virus particles was affected by the peptide. A shortened, six amino acid form of this peptide inactivated cell-free preparations of influenza, vesicular stomatitis and Sindbis viruses and also bound effectively to virus-encoded structural proteins. For this virus-protein interaction, the peptide sequence was highly specific with respect to its hydrophobicity and net ionic charge.

[Gastric emptying and intragastric distribution of liquid and solid meal in patients with systemic sclerosis]

To evaluate the gastric emptying functions in patients with systemic sclerosis (SS), gastric emptying and intragastric distribution during emptying after a liquid-solid meal were studied by single photon emission computed tomography in 11 patients without gut symptoms and in 17 healthy volunteers. In patient group, half emptying times both of proximal (pT50) and of total stomach (T50) for both meal components were significantly longer than in controls. There were significant relationships respectively between the T50 and the pT50 for both liquid and solid meal. Out of 11 cases, 9 had delayed T50 of solid, which were accompanied by delayed emptying of liquid in 8 patients. The prolongation of gastric emptying of solid correlated significantly with the duration of the disease. However, the changes of the activity-time curves in the distal stomach during emptying were not reaching significant level when compared to the controls. In conclusion despite no existence of any gut symptoms our SS patients present significant delayed gastric emptying, which may be correlated to the dysfunction of tonic contraction of the proximal stomach attributed to autonomic neuropathy.

A new hypothesis about the relationship between free radical reactions and hemorheological properties in vivo

This paper is concerned with a hypothesis that disturbance of free radical reactions may lead to abnormality of hemorheological properties in vivo, and so the free radicals generated in vivo may damage certain tissue cells indirectly by reducing the supply of oxygen and nutrients to these cells through slowing the circulation of blood. This hypothesis is based on the following evidence: A. We have found that the whole blood viscosity at low shear rate correlates to the lipid peroxidation in the patients suffering from certain cardio- or cerebrovascular diseases, and in dogs during liver ischemia reperfusion or hemorrhagic pancreatitis. B. Reports have shown that several alterations of hemorheological properties may take place as a result of free radical reactions, such as lipid peroxidation. For instance, lipid peroxidation may lead to decrease of deformability of red cells, increase of aggregation of red cells, formation of liquid thrombin, etc. C. We have demonstrated that some alterations of hemorheological properties involve the role of free radicals in rats suffering from intestinal ischemia/reperfusion. As evidence for this conclusion, superoxide dismutase (SOD) used as a specific scavenger of superoxide anion radical (O2-) can significantly prevent the intestinal ischemia/reperfusion induced changes of lipid peroxidation, red cell aggregation, Cassion's viscosity and whole blood viscosity at low shear rate in rats.

Further characterization of the kinetic folding intermediate of alpha alpha-tropomyosin and of its 142-281 subsequence

The backbone CD spectrum from 250 to 212 nm for the kinetic folding intermediate of alpha alpha-tropomyosin (alpha alpha-Tm) and nonpolymerizable alpha alpha-Tm was obtained. The spectrum shows that the intermediate is indeed alpha-helical with about 70% of the equilibrium alpha-helix content. Subsequence 142Tm281 of the alpha-tropomyosin chain has five tyrosine residues (at positions 162, 214, 221, 261, 267). Stopped flow CD at the negative peak in the tyrosine spectral region (280 nm) shows that any tyrosine residues that contribute to the spectrum in the region have already reached their final state in the fast phase of folding (< 0.04 s).

Direct measurement of oxygen free radicals following cardiac failure of ischemic dog myocardium with the electron spin resonance technique

OBJECTIVE

To determine whether the involvement of oxygen-derived free radicals in the pathogenesis of ischemic cardiac failure in dogs.

DESIGN

Free radicals were measured in normal and ischemic myocardium from dogs with cardiac failure induced by acute coronary occlusion. The changes in free radical production in ischemic myocardium (compared with normal myocardium with or without polymorphonuclear leukocytes) were studies, with plasma superoxide dismutase and malondialdehyde analyzed concurrently.

MAIN RESULTS

The results showed that the oxygen free radicals in the ischemic myocardium were about 42.5% higher than those in the normal myocardium, about 67.8% higher than those in the normal myocardium washed with normal saline and about 60.5% higher than those in the ischemic myocardium washed with normal saline (P < 0.05). Compared with controls, the concentration of malondialdehyde in ischemic dog myocardium was increased markedly. The activity of plasma superoxide dismutase was not significantly different between control dogs and dogs with ischemic cardiac failure.

CONCLUSIONS

The current results indicate that there was increased production of free radicals and peroxidative damage in ischemic myocardium of dogs with cardiac failure. Polymorphonuclear leukocytes appear to be a main source of free radicals in dog with ischemic cardiac failure.

Kinetics of folding and unfolding of beta beta-tropomyosin

The kinetics of folding from random coils to two-chain coiled coils of beta beta-tropomyosin was studied by stopped-flow CD (SFCD) in the backbone region (222 nm). Two species were studied: the reduced form and the doubly disulfide cross-linked form. The proteins were totally unfolded in 6M urea-saline buffer, then refolded by tenfold dilution into benign buffer. In the refolding medium, they spontaneously recover the two-chain coiled-coil structure. Reduced beta beta refolds in at least two stages: one or more fast phases (< 0.04 s), in which an intermediate with 71% of the equilibrium ellipticity forms, followed by a slower time-resolvable phase that completes the folding. The slow phase is first order, signifying that dimerization occurs in the fast phase. The time constant of the slow phase is 2 s at 20 degrees C and requires activation parameters of delta S not equal to = -7 +/- 0.3 cal/mol.K, delta H not equal to = 15 +/- 1 kcal/mol. These results are very similar to those previously found for the reduced genetic variant alpha alpha-tropomyosin. In contrast, refolding of doubly disulfide cross-linked beta beta is complete within the dead time (< 0.04 s), whereas the singly cross-linked alpha alpha species also displays a slow phase. The opposite process, unfolding reduced beta beta from the coiled-coil state, is complete within the dead time, as in the alpha alpha variant.

Kinetics of folding of alpha alpha-tropomyosin subsequences

The kinetics of folding random coils of alpha alpha-tropomyson (Tm) subsequences to two-chain coiled coils was studied by stopped-flow CD. Subsequences studied were those comprising residues 11-127 (11Tm127), 142-281 (142Tm281), 1-189 (1Tm189), and 190-284 (190Tm284) of the parent 284-residue alpha-tropomyosin chain. Unlike the parent, subsequences 1Tm189 and 11Tm127 fold within the dead time of the instrument (less than 0.04 s). Like the parent, subsequences 142Tm281 and 190Tm284 fold in two phases. In the fast phase, 45% and 32%, respectively, of the equilibrium helical content form. In the time-resolvable, first-order slow phase (k-1 = 2.7 s at 20 degrees C for 142Tm281 and k-1 = 2.0 s at 15 degrees C for 190Tm284), the remaining structure forms. Neither reduced 142Tm281 nor 190Tm284 show any dependence of the rate on concentration, so chain association occurs in the fast phase. Like the parent 142Tm281 forms more helical content in the fast phase when cross-linked at C-190, and the remaining structure forms slowly with rate parameters similar to those of the reduced species. Comparison of the folding behavior of C- and N-terminal subsequences with that of the parent protein suggests that the slow phase in the parent is caused by a folding bottleneck somewhere nearer the C-terminus. However, rapid association and partial folding near the N-terminus is not necessary for prompt folding, since even 190Tm284 chains associate and partially fold very rapidly (less than 0.04 s), and then complete the folding in seconds.

Kinetics of folding and unfolding of alpha alpha-tropomyosin and of nonpolymerizable alpha alpha-tropomyosin

Stopped flow CD (SFCD) kinetic studies of self-assembly of coiled coils of rabbit alpha alpha-tropomyosin and of nonpolymerizable alpha alpha-tropomyosin (NPTm) are reported. The protein was denatured in 6 M urea buffer, then renatured by 10-fold dilution into benign saline buffer. Folding was monitored by SFCD in the backbone region (222 nm). Protein chains are shown to be totally unfolded (and separated in the reduced species) in the initial denaturing medium and fully folded as two-chain coiled coils in the final benign medium. In all cases of folding in benign buffer of totally unfolded chains, two phases were found in the folding process: a fast phase (less than 0.04 s, the SFCD dead time), in which an intermediate state with about 70% of the equilibrium ellipticity forms; followed by a slower, observable phase that completes the folding. The slow phase is first order (k-1 = 1.6 s at 20 degrees C), signifying that chain association for reduced samples occurs in the fast phase. In contrast, folding in benign buffer from an initial state with 70% of the equilibrium ellipticity is all fast, suggesting that the folding intermediate is not an equilibrium species. Cross-linking at Cys-190 increases the helix content of the fast-formed intermediate state to about 85% of the equilibrium value, but leaves the rate constant of the slow phase unchanged. In NPTm, which does not form high aggregates at low ionic strength, the rate of the observable phase is almost independent of ionic strength in the range of approximately 0.15-0.6 M, but is reduced one to two orders of magnitude by further reduction to 0.026 M. In folding from totally unfolded chains, the rate is reduced less than one order of magnitude by changing the final state to about 50% folded. In contrast to folding, unfolding of alpha alpha-tropomyosin from the native state is all fast.

Prevention of myocardial reperfusion injury with free radical scavengers. An experimental study

The changes in endogenous superoxide dismutase (ESOD) during myocardial ischemia and reperfusion and the efficacy of oxygen free radical scavengers in myocardial protection were investigated in an isolated heart model connected with the recirculating nonpulsatile perfusion circuit. Subjected to a 2-hour period of global ischemia (27 C), the heart was reperfused with 37 C oxygen diluted auto-blood for 60 minutes. Superoxide dismutase plus catalase was added into the cardioplegic solution and reperfusates. ESOD activity was measured by pyrogallol method. The results of the experiment showed that ESOD activity after ischemia and reperfusion was decreased and the addition of oxygen free radical scavengers (SOD and CAT) to the cardioplegic solution and the reperfusates greatly reduced the leakage of myocardial enzymes, coronary vascular resistance, and the ultrastructural damages of the myocardium. These results suggest that the use of SOD and CAT may inhibit myocardial reperfusion injury by scavenging oxygen-derived free radicals.

Collagen induced arthritis: an experimental model for rheumatoid arthritis with involvement of both DTH and immune complex mediated mechanisms

The type II collagen induced arthritis animal model (CIA) provides opportunities to study the nature of autoimmune reactions leading to arthritis and is also a useful model for rheumatoid arthritis (RA). Thus, in similarity with RA, the CIA when induced with autologous type II collagen, shows a chronic and progressive disease course. The susceptibility to both RA and CIA are correlated to the expression of certain MHC class II allotype genes. In both diseases autoantibodies to type II collagen and rheumatoid factors are produced. Immunohistopathology of affected joints show in both diseases a dominance of activated macrophages/fibroblasts with a significant infiltration of activated T cells. We suggest here that both RA and CIA are dependent on a synergy between delayed type hypersensitivity and immune complex mediated inflammatory mechanisms and that CIA could provide a tool for studies of immunospecific reactions leading to arthritis.

Collagen induced arthritis as an experimental model for rheumatoid arthritis. Immunogenetics, pathogenesis and autoimmunity

The type II collagen (CII) induced arthritis animal model (CIA) provides opportunities to study the nature of autoimmune reactions leading to arthritis and may be used as a model for rheumatoid arthritis (RA). Thus, in similarity with RA, the CIA model, when induced with autologous CII, shows a chronic and progressive disease course. The susceptibility to both RA and CIA are correlated to the expression of certain MHC class II allotype genes. In both diseases are autoantibodies to CII and rheumatoid factors produced. Immunohistopathology of affected joints show in both diseases a dominance of activated macrophages/fibroblasts with a significant infiltration of activated T cells and an infiltration of granulocytes. We do here suggest that both RA and CIA are dependent on a synergy between delayed type hypersensitivity and immune complex mediated inflammatory mechanisms and that CIA provides opportunities for studies of immunospecific reactions leading to arthritis.

Induced suppression in spike responses to tone-on-noise stimuli in the auditory nerve of the pigeon

Spike potentials were recorded from single, afferent fibres in the pigeon auditory nerve. Pure-tone stimuli were presented in quiet and in combination with wide band noise. Presented alone, tones produced tuned response areas; noise generally drove spike rate to well above the spontaneous rate measured in quiet. When presented in combination with noise, tones up to 75 dB SPL at frequencies far from the fibre's response area had no effect on the noise-driven spike rate. As the tone frequency was shifted towards the response area, from above or below CF, suppression of the noise-driven spike rate became stronger until the tone reached the edge of the response area. Suppression of the noise-driven rate was directly proportional to the level of the tone. Within the area of response to the tone, tone-driven spike rates generally were unchanged or variably decreased (occasionally slightly increased) by tone-on-noise stimulation, depending on the relation of the tone frequency to CF and the level of the tone relative to that of the noise. Tuning properties were unaffected. It is suggested that in the pigeon, the suppression of driven spike rate during presentation of combination stimuli, which is common to all fibres, depends on the same mechanism as the suppression of spontaneous firing by tones that is observed in a proportion of fibres (Temchin, A.N. (1988), J. Comp. Physiol. A 163, 99-115; Hill et al., (1989) Hear. Res. 39, 37-48).

Excitation and suppression of primary auditory fibres in the pigeon

Spike potentials were recorded from single fibres in the auditory nerve of the pigeon. In fibres with recognizable responses to sound, spontaneous activity and properties of responses to tonal stimuli were studied in quiet background conditions. Mean spontaneous rate in the sample of fibres was 35 spikes/s. Tuning of spike response to tones was manifest as a single peak in rate at each sound pressure level (SPL) in the frequency-intensity plane. The majority of fibres showed only excitation of spike rate above spontaneous rate. Post stimulus time histograms (PSTs) in such cases were typical of excitatory responses, previously described in birds and mammals showing pronounced adaptation and post-stimulus suppression of spike rate. In most cases of excitation-only responses, however, slopes of rate functions depended on stimulus frequency. Close to characteristic frequency (CF), slopes tended to decrease with increasing SPL, whereas away from CF, slopes tended to increase with SPL. In a minority of excitation-only responses, slopes of rate functions were parallel. In some fibres, tones adjacent to the response area caused overt suppression of spontaneous firing. For these fibres, the slopes of rate functions were more-strongly frequency-dependent, being negative at low SPL when rate suppression occurred. Suppression of spontaneous activity at low SPL was non-monotonic and quite different from suppression of spike rate at stimulus intensities above rat saturation. In PSTs of suppressed spontaneous activity, rebound occurred at the termination of the tone. The results clarify previous observations of suppression of primary auditory responses in birds. We conclude that responses in the majority of auditory fibres in the pigeon are the product of opposing excitatory and suppressive influences in the cochlea, generated by single tones in quite.

Temporal synchronization in the primary auditory response in the pigeon

Spike potentials were recorded from single fibres in the auditory nerve of the pigeon. In responses elicited by tonal stimuli, the timing of each spike relative to stimulus waveform was measured and period histograms were constructed. Phase locking of spikes was estimated in terms of a synchronicity index obtained by vector addition within the period histogram. A second measure of synchrony in the spike responses was obtained, that of temporal dispersion. For a population of fibres, vector strength of phase locking decreased for frequencies above 1 kHz, as reported for several other species. Temporal dispersion, however, also decreased with frequency, indicating enhanced temporal synchrony as frequency increased within the bandwidth of phase locking. The upper frequency limit of phase locking appears to depend on irreducible jitter of biological origin in the timing of spikes. For individual fibres, the bandwidth of synchronization of spikes consistently exceeds the response area, covering in addition the areas of suppression adjacent to the response area. Spike trains suppressed by a tonal stimulus become synchronized to that stimulus. Phase angles of synchronized responses systematically change as a function of tone level, when tone frequency is above or below CF, as reported for other avian species. Synchronicity and phase angle intensity functions are quite independent of spike rate intensity functions.

A model proposing synaptic and extra-synaptic influences on the responses of cochlear nerve fibres

A unique property of sensory coding in the vertebrate auditory system is the existence of the classical form of excitatory centre-inhibitory surround in relative spike rate along the stimulus frequency dimension, in addition to a representation of temporal fine structure of high frequency periodic stimuli in the discharge pattern of primary afferent spike trains. We present a model which designates three factors that influence rate and temporal synchrony in spike responses; an excitatory factor, a suppressive factor and a synchronizing factor. The model proposes that an essential integration of bioelectric signals occurs in the primary afferent fibre. It is presumed that mean spike rate depends on mean level of membrane depolarization and synchronization depends on periodic modulation of membrane potential at the spike initiating zone. In the model, the excitatory factor is synaptically-mediated, excitatory post-synaptic potential (e.p.s.p.); the suppressive factor is negative DC polarization of the fibre membrane and the synchronizing factor is AC modulation of the fibre membrane potential. It is proposed that both the negatively-polarizing and high-frequency modulating signals are derived from extracellular current flow in the cochlea.