Captopril treatment improves the sarcoplasmic reticular Ca(2+) transport in heart failure due to myocardial infarction

Although captopril, an angiotensin-converting enzyme (ACE) inhibitor, has been shown to exert a beneficial effect on cardiac function in heart failure, its effect on the status of sarcoplasmic reticulum (SR) Ca(2+) transport in the failing heart has not been examined previously. In order to determine whether captopril has a protective action on cardiac function, as well as cardiac SR Ca(2+)-pump activity and gene expression, a rat model of heart failure due to myocardial infarction was employed in this study. Sham operated and infarcted rats were given captopril (2 g/l) in drinking water; this treatment was started at either 3 or 21 days and was carried out until 8 weeks after the surgery. The untreated animals with myocardial infarction showed increased heart weight and elevated left ventricular end diastolic pressure, reduced rates of pressure development and pressure fall, as well as depressed SR Ca(2+) uptake and Ca(2+)-stimulated ATPase activities in comparison with the sham control group. These hemodynamic and biochemical changes in the failing hearts were prevented by treatment of the infarcted animals with captopril. Likewise, the observed reductions in the SR Ca(2+) pump and phospholamban protein contents, as well as in the mRNA levels for SR Ca(2+) pump ATPase and phospholamban, in the failing heart were attenuated by captopril treatment. These results suggest that heart failure is associated with a defect in the SR Ca(2+) handling and a depression in the gene expression of SR proteins; the beneficial effect of captopril in heart failure may be due to its ability to prevent remodeling of the cardiac SR membrane.

[Analysis of the late curative effect of 432 cases with advanced squamous cell carcinoma of the maxillary sinus]

OBJECTIVE

To study the late curative effect of different methods used in the treatment of advanced squamous cell carcinoma of the maxillary sinus (SCMS).

METHODS

A retrospective analysis of 432 cases with SCMS was done. Among them, 141 cases were in stage III, 291 in stage IV, 244 were male, 188 were female, and the age ranged from 14 to 87 years. Radiotherapy, operation only and the combined treatment (radiation plus operation) were adopted.

RESULTS

The 5-year survival rates were 15.6% in radiation group, 21.7% in operation group, and 40.1% in combined group (40% in the preoperative irradiation group, and 43% in the postoperative irradiation group). The 5-year survival rates were 31.7%, 46.6% and 20% respectively for those involving structures above, below or both above and below the Ohngren line. Among the 238 cases with poor curative effect, 198 had local recurrence.

CONCLUSION

Combined treatment was the best choice for advanced SCMS. There were no significant differences in the survival rates between preoperative and postoperative radiotherapy groups. The survival rate might be improved by preoperative radiotherapy with a dose of 50 Gy, or postoperative radiotherapy with doses of 60-70 Gy. The prognosis for those with the tumor located below the Ohngren line was much better than those above the line and those both above and below the line. The key to the successful treatment for maxillary sinus carcinoma is to control the local recurrence effectively.

Multiple mechanisms for polyunsaturated fatty acid regulation of hepatic gene transcription

Dietary polyunsaturated fatty acids (PUFA) have profound effects on hepatic gene transcription leading to significant changes in lipid metabolism. Highly unsaturated n-3 PUFA suppress the transcription of genes encoding specific lipogenic enzymes and induce the expression of genes encoding specific enzymes involved in peroxisomal and microsomal fatty acid oxidation. Our studies have shown that fatty acid effects on hepatic gene expression may involve at least three distinct pathways. One pathway involves peroxisome proliferator-activated receptor (PPARalpha), a fatty acid activated nuclear receptor. PPARalpha is required for the PUFA induction of mRNAs encoding enzymes involved in fatty acid oxidation. However, PPARalpha is not required for PUFA suppression of mRNAs encoding proteins involved in lipogenesis. A second pathway involves prostanoids. In cultured 3T3-L1 adipocytes, cyclooxygenase derived 20:4 n-6 metabolites, like PGE2, suppress mRNAs encoding proteins involved in lipogenesis. However, in hepatic parenchymal cells, 20:4 n-6 suppression of lipogenic gene expression does not require a cyclooxygenase. Nevertheless, PGE2 and PGF2alpha suppress hepatic lipogenic gene expression. 20:4 n-6 cyclooxygenase products can arise from non-parenchymal cells and through a paracrine control process act on a G-protein linked receptor signaling cascade to suppress lipogenic gene expression. The fact that n-3 and n-6 PUFA suppression of lipogenic gene expression does not require PPARalpha or cyclooxygenase activity indicates the presence of a third pathway for the control of hepatic gene transcription. These studies indicate that the pleiotropic effects of PUFA on hepatic lipid metabolism cannot be attributed to a single regulatory mechanism.

[Preliminary study of a new concept for left ventricular assistance dynamic aortic valve]

Dynamic aortic valve, a novel design for left ventricular assistance is proposed. An impeller similar to the airscrew is placed in the position of aortic valve. The impeller is held by a pair of bearings in the center of a cylindrical supporting cage which is located in the lumen of the aorta ascendens. The supporting cage is attached to the valve annulus by a sewing ring of textile cuff around the outside of the cage. A rotor is fitted into the cage and connected to the impeller with a common shaft. The cage supports the aortic wall, thus prevents the rotor from founching the wall and allows the rotor to rotate freely. A stator, functioning as that of the electric motor, is located outside the aortic wall. When actuated, the magnetic field generated by the stator would drive the rotor to turning, and the axial flow of blood from ventricular to the aorta would be produced, resulting in the reduction of the ventricular load. We studied this concept in a simulating model. The result suggests that this design be reasonable. Further exploration of this concept is justified.

PRDI-BF1/Blimp-1 repression is mediated by corepressors of the Groucho family of proteins

The PRDI-BF1/Blimp-1 protein is a transcriptional repressor required for normal B-cell differentiation, and it has been implicated in the repression of beta-interferon (IFN-beta) and c-myc gene expression. Here, we show that PRDI-BF1 represses transcription of the IFN-beta promoter and of an artificial promoter through an active repression mechanism. We also identified a minimal repression domain in PRDI-BF1 that is sufficient for transcriptional repression when tethered to DNA as a Gal4 fusion protein. Remarkably, this repression domain interacts specifically with hGrg, TLE1, and TLE2 proteins, all of which are members of the Groucho family of transcriptional corepressors. In addition, the hGrg protein itself can function as a potent repressor when tethered to DNA through the Gal4 DNA-binding domain. We also find that the amino-terminal glutamine-rich domains of hGrg and TLE1 are sufficient to mediate dimerization of the two Groucho family proteins. Proteins containing only this domain can function as a dominant-negative inhibitor of PRDI-BF1 repression, and can significantly increase the IFN-beta promoter activity after virus induction. We conclude that PRDI-BF1/Blimp-1 represses transcription by recruiting a complex of Groucho family proteins to DNA, and suggest that such corepressor complexes are required for the postinduction repression of the IFN-beta promoter.

A protein disulfide oxidoreductase from the archaeon Pyrococcus furiosus contains two thioredoxin fold units

Protein disulfide bond formation is a rate limiting step in protein folding and is catalyzed by enzymes belonging to the protein disulfide oxidoreductase superfamily, including protein disulfide isomerase (PDI) in eucarya and DsbA in bacteria. The first high resolution X-ray crystal structure of a protein disulfide oxidoreductase from the hyperthermophilic archaeon Pyrococcus furiosus reveals structural details that suggest a relation to eukaryotic PDI. The protein consists of two homologous structural units with low sequence identity. Each unit contains a thioredoxin fold with a distinct CXXC active site motif. The accessibilities of both active sites are rather different as are, very likely, their redox properties. The protein shows the ability to catalyze the oxidation of dithiols as well as the reduction of disulfide bridges.

Regulation of Drosophila Adh promoter switching by an initiator-targeted repression mechanism

The stage-specific expression of the Drosophila alcohol dehydrogenase (Adh) gene is achieved through the alternate activation of two tandem promoters. The proximal promoter is active primarily during late embryonic development and early larval stages, while the distal promoter is active in late third instar larvae and adults. Here, we provide evidence that this Adh promoter switch is regulated by a zinc finger repressor protein (AEF-1) that is expressed predominantly in adult flies and targets the initiator region of the proximal promoter. We propose that AEF-1 plays a critical role in Adh promoter switching by blocking interactions between a component of the general transcription machinery and the initiator region of the proximal promoter.

Electrocardiographic Changes and Mortality Due to Myocardial Infarction in Rats With or Without Imidapril Treatment

BACKGROUND: Various angiotensin-converting enzyme inhibitors are known to improve heart function and prolong survival in patients and animals after myocardial infarction. Because myocardial infarction is known to induce arrhythmias, this study tested the hypothesis that early treatment with the angiotensin converting enzyme inhibitor imidapril reduces mortality during acute myocardial infarction because of protective effects against arrhythmogenesis. METHODS AND RESULTS: Rats were randomly divided into four groups: sham control, myocardial infarction, sham plus imidapril, and myocardial infarction plus imidapril. Myocardial infarction was produced by ligation of the left anterior descending coronary artery. Treated rats received imidapril (1 mg/kg/day) through a gastric tube beginning 1 hour after coronary occlusion; control rats received tap water. Electrocardiogram (ECGs) were recorded 1, 3, 7, and 21 days postocclusion. Infarct size and scar weight were determined at 21 days in the myocardial infarction groups with and without imidapril treatment. ECGs of untreated rats showed ST-segment changes, abnormal Q waves, premature ventricular complexes, and QT(c) prolongation 1-21 days after coronary occlusion. Total mortality in 21 days averaged 35% in untreated rats; mortality within 48 hours was 30%. On the other hand, imidapril-treated rats showed fewer ST-segment changes, fewer abnormal Q waves, and a decreased incidence of premature ventricular complexes after coronary occlusion; the ST-segment and QT(c) interval returned to basal values within 1 week after occlusion. Imidapril treatment did not affect the ECG pattern in sham-treated control animals. Total mortality in the imidapril-treated group in 21 days after infarction was 22.5%; mortality within 48 hours was 20% (P <.05 compared with the untreated infarction group). Infarct size and scar weight caused by coronary occlusion did not differ in the untreated and imidapril-treated groups. CONCLUSIONS: Early treatment with imidapril markedly decreases mortality in rats after acute myocardial infarction. The lower mortality is not associated with a decrease in infarct size but is consistent with a protective effect of the drug against arrhythmogenesis.

Dietary fat, genes, and human health

These studies show that a macronutrient like dietary fat plays an important role in gene expression. In the cases presented here, dietary fat regulates gene expression leading to changes in carbohydrate and lipid metabolism. The interesting outcome of these studies is the finding that the molecular targets for dietary fat action did not converge with the principal targets for hormonal regulation of gene transcription, like hormone receptors. Instead, PUFA-RF targets elements that play key ancillary roles in gene transcription. This is important because it shows how PUFA can interfere with hormone regulation of a specific gene without having generalized effect on overall hormonal control, i.e. PUFA effects are promoter-specific. How PUFA-RF interferes with gene transcription will require the isolation and characterization of PUFA-RF along with the tissue-specific factors targeted by PUFA-RF. A different story emerges when fatty acids activate PPAR. Based on the studies presented here and elsewhere, long chain-highly unsaturated fatty acids (like 20:5,n-3 and 22:6, n-3) or high levels of fat activate PPAR. PPAR directly activates genes like AOX, but also inhibits transcription of genes like S14, FAS, apolipoprotein CIII, transferrin. For S14, the mechanism of inhibition involves sequestration of RXR, a critical factor for T3 receptor binding to DNA. Thus, PPAR can have generalized effects on T3 action or on other nuclear receptors, like vit. D (VDR) and retinoic acid (RAR) receptors, that require RXR for action. For apolipoprotein CIII and transferrin, PPAR/RXR heterodimers compete for HNF-4 binding sites (DR + 1). In addition to HNF-4, COUP-TF, ARP-1 and RXR all bind the DR + 1 type motif. These factors are important for tissue-specific regulation of gene transcription. PPAR can potentially interfere with the transcription of multiple genes through disruption of nuclear receptor signaling leading to changes in phenotype. Clearly, more studies are required to assess the role PPAR plays in the fatty acid regulation of gene transcription and its contribution to chronic disease. Finally, it is clear that dietary fat has the potential to affect gene expression through multiple pathways. Depending on the gene examined, PUFA might augment or abrogate gene transcription which leads to specific phenotypic changes altering metabolism, differentiation or cell growth. These effects can be beneficial to the organism, such as the n-3 PUFA-mediated suppression of serum triglycerides or detrimental, like the saturated and n-6 PUFA-mediated promotion of insulin resistance. How such effects contribute to the onset or progression of specific neoplasia is unclear. However, studies in metabolism might provide important clues for this connection.

Polyunsaturated fatty acid suppression of hepatic fatty acid synthase and S14 gene expression does not require peroxisome proliferator-activated receptor alpha

Dietary polyunsaturated fatty acids (PUFA) induce hepatic peroxisomal and microsomal fatty acid oxidation and suppress lipogenic gene expression. The peroxisome proliferator-activated receptor alpha (PPARalpha) has been implicated as a mediator of fatty acid effects on gene transcription. This report uses the PPARalpha-deficient mouse to examine the role of PPARalpha in the PUFA regulation of mRNAs encoding hepatic lipogenic (fatty acid synthase (FAS) and the S14 protein (S14)), microsomal (cytochrome P450 4A2 (CYP4A2)), and peroxisomal (acyl-CoA oxidase (AOX)) enzymes. PUFA ingestion induced mRNAAOX (2.3-fold) and mRNACYP4A2 (8-fold) and suppressed mRNAFAS and mRNAS14 by >/=80% in wild type mice. In PPARalpha-deficient mice, PUFA did not induce mRNAAOX or mRNACYP4A2, indicating a requirement for PPARalpha in the PUFA-mediated induction of these enzymes. However, PUFA still suppressed mRNAFAS and mRNAS14 in the PPARalpha-deficient mice. Studies in rats provided additional support for the differential regulation of lipogenic and peroxisomal enzymes by PUFA. These studies provide evidence for two distinct pathways for PUFA control of hepatic lipid metabolism. One requires PPARalpha and is involved in regulating peroxisomal and microsomal enzymes. The other pathway does not require PPARalpha and is involved in the PUFA-mediated suppression of lipogenic gene expression.

The crystal structure of seleno-glutathione peroxidase from human plasma at 2.9 A resolution

Glutathione peroxidase belongs to the family of selenoproteins and plays an important role in the defense mechanisms of mammals, birds and fish against oxidative damage by catalyzing the reduction of a variety of hydroperoxides, using glutathione as the reducing substrate. However, the physiological role of human plasma glutathione peroxidase remains unclear due to the low levels of reduced glutathione in human plasma and the low reactivity of this enzyme. The crystal structure of human plasma glutathione peroxidase was determined by Patterson search methods using a polyalanine model modified from the known structure of bovine erythrocyte glutathione peroxidase. The structure was refined to a crystallographic R-factor of 0.228 (R(free) = 0.335) with I > 2sigma(I) reflections in the resolution range of 8 to 2.9 A. The asymmetric unit contains a dimer. Tetramers are built up from dimers by crystallographic symmetry. The subunit structure of the plasma enzyme shows the typical structure motif of the thioredoxin fold consisting of a central beta-sheet and several flanking alpha-helices. The active site selenocysteine residue is situated in the loop between beta1 and alpha1 and is located in a pocket on the protein surface. The overall structure of the human plasma enzyme is similar to that of the bovine erythrocyte enzyme. The main differences in their subunit structures are an extended N terminus and the possible existence of a disulfide bridge in the plasma enzyme. Compared to the bovine erythrocyte enzyme, a number of residues in the active site are mutated or deleted in the plasma enzyme, including all the residues that were previously suggested to be involved in glutathione binding. The observed structural differences between the two enzymes suggest differences in substrate binding and specificity.

Single-and dual-energy CT with monochromatic synchrotron x-rays

We explored the potential for clinical research of computed tomography (CT) with monochromatic x-rays using the preclinical multiple energy computed tomography (MECT) system at the National Synchrotron Light Source. MECT has a fixed, horizontal fan beam with a subject apparatus rotating about a vertical axis; it will be used for imaging the human head and neck. Two CdWO4-photodiode array detectors with different spatial resolutions were used. A 10.5 cm diameter acrylic phantom was imaged with MECT at 43 keV and with a conventional CT (CCT) at 80 kVp: spatial resolution approximately equal to 6.5 line pairs (lp)/cm for both; slice height, 2.6 mm for MECT against 3.0 mm for CCT; surface dose, 3.1 cGy for MECT against 2.0 cGy for CCT. The resultant image noise was 1.5 HU for MECT against 3 HU for CCT. Computer simulations of the same images with more precisely matched spatial resolution, slice height and dose indicated an image-noise ratio of 1.4:1.0 for CCT against MECT. A 13.5 cm diameter acrylic phantom imaged with MECT at approximately 0.1 keV above the iodine K edge and with CCT showed, for a 240 micrograms I ml-1 solution, an image contrast of 26 HU for MECT and 13 and 9 HU for the 80 and 100 kVp CCT, respectively. The corresponding numbers from computer simulation of the same images were 26, 12, and 9 HU, respectively. MECT's potential for use in clinical research is discussed.

Daily spinal cord stimulation suppresses autotomy behavior in rats following peripheral deafferentation

Autotomy in experimental animals following peripheral nerve section has been interpreted as a sign of pain corresponding to the chronic pain observed in patients with extensive nerve lesions. Such pain may be alleviated by spinal cord stimulation. In the present study, the effect of such stimulation, via chronically implanted electrodes, on autotomy behavior following sciatic nerve section was assessed in the rat. The stimulation was applied for 30 min daily during a 10-day period. There were four groups of animals, 16 in each, half of them females. Stimulating electrodes were implanted in all and one group served as control, receiving sham stimulation. In one group, the stimulation was started when autotomy was observed, one received stimulation from the day of nerve section, and in one it was begun three days before section. The onset of autotomy was significantly delayed in the latter two groups. When stimulation was applied as "treatment", autotomy ceased but reappeared after the 10-day stimulation period. The incidence and severity of autotomy was markedly delayed and reduced when the stimulation had been applied just after the nerve section or before. In the latter groups, the diminished degree of autotomy persisted for the entire observation period, lasting 60 days after the stimulation was stopped. It seems that spinal cord stimulation, albeit applied only once daily and during a limited time period, can protect the spinal cord from developing the state of hyperexcitability believed to be the major cause of autotomy behavior. Peripheral mechanisms may also play a role by the antidromic activity evoked by the stimulation in the sectioned peripheral nerve. This study shows that spinal cord stimulation, which is a commonly employed method for treating chronic neurogenic pain, may have long-lasting effects on plasticity changes in the spinal cord following peripheral nerve injury, even when the stimulation is applied for short periods of time.

Peroxisome proliferator-activated receptor alpha inhibits hepatic S14 gene transcription. Evidence against the peroxisome proliferator-activated receptor alpha as the mediator of polyunsaturated fatty acid regulation of s14 gene transcription

The peroxisome proliferator-activated receptor (PPARalpha) has been implicated in fatty acid regulation of gene transcription. Lipogenic gene transcription is inhibited by polyunsaturated fatty acids (PUFA). We have used the PUFA-sensitive rat liver S14 gene as a model to examine the role PPARalpha plays in fatty acid regulation of hepatic lipogenic gene transcription. Both PPARalpha and the potent peroxisome proliferator, WY14643, inhibit S14CAT activity in transfected primary hepatocytes. WY14643 and PPARalpha target the S14 T3 regulatory region (TRR, -2.8 to -2.5 kilobases), a region containing 3 T3 response elements (TRE). Transfer of the TRR to the thymidine kinase (TK) promoter conferred negative control to the TKCAT gene following WY14643 and PPARalpha treatment. Gel shift analysis showed that PPARalpha, either alone or with RXRalpha, did not bind the S14TRR. However, PPARalpha interfered with TRbeta/RXRalpha binding to a TRE (DR+4). Functional studies showed that co-transfected RXRalpha, but not T3 receptor beta1 (TRbeta1), abrogated the inhibitory effect of PPARalpha on S14 gene transcription. These results suggest that WY14643 and PPARalpha functionally interfere with T3 regulation of S14 gene transcription by inhibiting TRbeta1/RXR binding to S14 TREs. Previous studies had established that the cis-regulatory targets of PUFA control were located within the proximal promoter region of the S14 gene, i.e. between -220 and -80 bp. Finding that the cis-regulatory elements for WY14643/PPARalpha and PUFA are functionally and spatially distinct argues against PPARalpha as the mediator of PUFA suppression of S14 gene transcription.

Effects of spinal cord stimulation on the flexor reflex and involvement of supraspinal mechanisms: an experimental study in mononeuropathic rats

The physiological mechanisms responsible for pain relief caused by spinal cord stimulation (SCS) are essentially unknown and recent experimental data are sparse. In the present study the authors explored the possible involvement of supraspinal mechanisms in the effects of SCS applied in rats with experimental mononeuropathy produced by sciatic nerve ligation according to the method of Bennett and Xie or that of Seltzer, et al. Confirming results of a previous study undertaken by the authors, the thresholds of the early component of the flexor reflex (latency 8-12 msec), which is mediated by A fibers, were significantly lower in the nerve-ligated than in the intact leg. In halothane-anesthetized animals the spinal cord was exposed and SCS was applied with parameters similar to those used in clinical SCS. Ten minutes of SCS produced a significant elevation of the lowered threshold of the early flexor component only in the nerve-ligated leg, and this augmentatory effect of SCS persisted for 30 to 40 minutes after cessation of the stimulation. The threshold elevation amounted to between 50% and 80% of the prestimulatory value and it was related to the intensity of SCS. The threshold of the late, C-fiber-mediated component of the flexor reflex was not influenced in either of the legs. After transection of the spinal cord at the T-6 level, there was a moderate threshold increase in both the early and late components in both legs, but the threshold of the early component in the nerve-ligated leg remained lower. Spinal cord stimulation produced an almost identical threshold increase in the early component in the nerve-ligated leg with the same time course as before the transection. There was no effect on the late component of the reflex in either leg. The results indicate that this effect of SCS in mononeuropathic rats does not necessarily involve supraspinal mechanisms; instead SCS is operative at a spinal, segmental level. In view of the similarities between the effects of therapeutic SCS on cutaneous hypersensibility in patients with peripheral neuropathic pain and the effects demonstrated in neuropathic rats, the clinical pain relief achieved with SCS may be produced, at least partially, by intraspinal mechanisms.

Preemptive spinal cord stimulation reduces ischemia in an animal model of vasospasm

Spinal cord stimulation (SCS) has been increasingly used in the treatment of ischemia caused by obliterative diseases in the extremities and in the cardiac circulation. The most promising effects have been obtained when physicians suspect that a major vasospastic component underlies the ischemic symptoms (e.g., as in Raynaud's disease). Despite the clinical success of this treatment method, little is known about the mechanisms underlying the pain relief it produces and its anti-ischemic effects. Most earlier experimental studies have used normal animals or animals with cerebral vasospasm induced by injection of autologal blood into the cerebrospinal fluid space. In the present study, we applied SCS in a rat model via implanted electrodes to study the effect of preemptive stimulation on the ischemia caused by vasospasm in a neurovascular flap in the groin; the vasospasm was induced by mechanical pressure applied to the feeding artery. In rats treated with SCS, delivered with parameters similar to those used clinically, the percentage of flaps recovering normal microcirculation after the spasm was significantly higher than in the untreated control group (100 and 28%, respectively; P < 0.05), and the maximal blood flow after the ischemic episode was significantly higher in the SCS group than in the control group (127 and 51 arbitrary units, respectively; P < 0.05). The percentage of animals regaining the premanipulation circulation after the provocation of a second spasm was also greater in the SCS-treated group than in the control animals (50 and 14%, respectively; P < 0.05). Pilot studies showed that this protective effect was specific to SCS given before spasm induction, an observation corroborated by clinical experiences.(ABSTRACT TRUNCATED AT 250 WORDS)

[Protective action of Lycium barbarum L. (LbL) and betaine on lipid peroxidation of erythrocyte membrane induced by H2O2]

H2O2 was used to induce lipid peroxidation of RBC membrane in rats to observe the protective action of different ingredients of LbL and betaine on the membrane. The result shows these ingredients cna inhibit the lipid peroxidation of RBC membrane in the following order of antioxidizing power: Fructus Lycii.LbL.dry(FL/LbL.dry) > Polysaccharide FL/LbL > Residue FL/LbL > betaine.

Spinal cord stimulation in animal models of mononeuropathy: effects on the withdrawal response and the flexor reflex

Spinal cord stimulation (SCS) is efficacious for pain due to injury of peripheral nerves, and therefore models of mononeuropathy appear to be particularly suitable for an experimental approach to the study of mechanisms underlying the clinical effect of this mode of treatment in chronic neuropathic pain. Virtually all previous experimental studies on SCS have utilized acute and nociceptive types of peripheral pain stimuli to explore the attenuating effects of SCS. In the present study we made use of the two models of supposedly painful neuropathy developed by Bennett and Xie (1988) and Seltzer et al. (1990) to explore the effect of SCS applied with stimulus parameters similar to those used in clinical practice. In rats subjected to ligatures of the sciatic nerve according to these two methods, SCS was applied via chronically implanted electrodes, or acutely via a laminectomy in the lower thoracic region. In awake, freely moving animals SCS produced a marked increase of the withdrawal thresholds to innocuous mechanical stimuli in the form of von Frey filaments. This threshold elevation lasted for up to 40 min after 10 min of SCS. In about one-half of the animals there was also a moderate, but short-lasting increase in the intact leg. The degree and duration of the withdrawal threshold elevation was clearly related to the intensity of SCS which was kept below the level of which a response in the thoracic or leg musculature was produced. In a second series of experiments the effect of SCS, applied acutely via a laminectomy, on the early component (latency: 8-12 msec) of the flexor reflex was studied. As a result of nerve ligation with either of the methods used, the thresholds for evoking the early as well as the late component in the nerve-ligated leg were significantly lower than in the intact one. SCS resulted in a marked and long-lasting increase of the threshold of the early component in the nerve-ligated leg. On the intact side only a slight and short-lasting increase was observed. The late, C fibre-mediated component was not influenced by SCS. The first component of the flexor reflex is conceivably mediated by A beta-fibre activation and it presumably corresponds to the withdrawal response induced by innocuous mechanical stimuli. The lack of effect of SCS on the late reflex component indicates that it selectively influences transmission of A-fibre activity. (ABSTRACT TRUNCATED AT 400 WORDS)

Effects of fatty acids on hepatic gene expression

Polyunsaturated fatty acids (PUFA) have dramatic effects on hepatic lipid metabolism by regulating the transcription of specific genes encoding enzymes involved in glycolysis and lipogenesis. The S14 gene, a putative lipogenic protein, has been used as a model to define the molecular basis of PUFA action on hepatic gene expression. We have shown that PUFA-regulated hepatic transcription factors target cis-regulatory elements located between -220 and -80 bp upstream from the 5' end of the S14 gene. Peroxisomal proliferators (PP) also have dramatic effects on hepatic lipid metabolism through effects on gene expression. The mechanism of PP action is mediated, at least in part, through nuclear receptors, i.e. PP activated receptor (PPAR). We found that the potent PP, i.e. WY14,643, suppressed mRNAS14 and the activity of an S14CAT fusion gene in cultured primary hepatocytes. Preliminary mapping studies showed that WY14,643 cis-regulatory elements were located either within the S14 proximal promoter (-290 and +19), the S14 TRE (-2900 to -2500) or both regions. Gel shift analysis showed that PPAR did not bind S14 promoter elements. These studies suggest that PUFA- and PP-regulated factors may share common cis-acting elements within the S14 promoter. However, if PUFA control of S14 gene transcription is mediated by PPAR, this mechanism does not involve direct interaction of PPAR with the S14 proximal promoter.

Severe peripheral ischemia after vasospasm may be prevented by spinal cord stimulation. A preliminary report of a study in a free-flap animal model

Electric spinal cord stimulation (SCS) is at present used in many centers to treat ischemic pain and ischemia in peripheral vascular disease. The most promising results have been obtained in cases where a vasospastic component is dominating. The knowledge concerning the mechanisms behind these effects has been scanty, but recent experimental studies indicate that suppression of sympathetic activity and the release of vasoactive substances may be important. A problem with many of the animals studies aimed at exploring these mechanisms is that they have almost exclusively been performed on normal animals without ischemia. However, in studies of the responsiveness of local ischemia to various pharmacological substances and to electrical transcutaneous nerve stimulation, animal models with ischemic skin flaps have been used. We applied SCS via chronically implanted electrodes in a model of local vasospasm in the rat, induced by mechanical stimulation of the vessel supplying an island flap in the groin. Male Sprague-Dawley rats were used. First, a monopolar system for spinal cord stimulation, with the intraspinal cathode at vertebral level T11, was implanted in halothane anaesthesia. After about three days of recovery the rats were anaesthetized with chloral hydrate ip and a groin neurovascular flap based on the epigastric vessels was raised. Microcirculation in the flap as well as in a control area in the contralateral groin was monitored by laser Doppler technique. Vasospasm was induced by gently pinching the superficial epigastric artery with microforceps. Two groups of animals were submitted to two spasm periods, one with SCS applied for 20 min. by 50 Hz; 0.2 msec and with 2/3 of the intensity required for a motor response before the first period. The second group, receiving sham SCS, served as a control. Both degree of ischemia after spasm provocation and the time to recovery were evaluated. In general SCS affected basal flow very little. In the control group the rats demonstrated increasing vasospastic reactions with subsequent flap ischemia to the two mechanical provocations. In the experimental group a response pattern emerged indicating that pre-spasm SCS could both reduce the spasm amplitude and significantly shorten the time for restoration of a satisfactory microcirculation in the flap. Some few trials with pharmacologically induced spasm by topical application of noradrenaline onto the feeding vessel also followed the same pattern. In conclusion, SCS seems to be able to reduce vasospasm, especially if the treatment is given before the ischemic period. This approach may supply an animal model for further studies of possible mechanisms behind the microcirculatory effects of SCS.

Receptive field properties of cat retinal ganglion cells during short-term IOP elevation

PURPOSE

To examine and compare receptive field properties of cat retinal ganglion cells before and during intraocular pressure (IOP) elevation.

METHODS

Responses of cat retinal ganglion cells to two sets of specially designed light or dark spots and annuli were recorded extracellularly. Receptive field properties were studied comparatively before and during short-term constant IOP elevation induced by keeping the retinal perfusion pressure at a critical level of about 30 mm Hg.

RESULTS

All the responses, including properties of different types of receptive fields and different components of the cells' receptive fields, decreased during short-term IOP elevation. The responses of off-center cells were more tolerant of IOP elevation than those of on-center cells, whereas the responses of Y cells were less sensitive to IOP elevation than those of X cells. The responses of the centers of the receptive fields exhibited pronounced resistance to IOP elevation than those of the surround. The peak responses of the post-stimulus time histogram of all cells declined less than the mean responses during IOP elevation.

CONCLUSIONS

The varied effects of short-term IOP elevation on different types (X and Y, on-center and off-center) of retinal ganglion cells and their receptive field properties may reflect the different degrees of ischemic effects on the retinal pathways that project to the different types of ganglion cells.

An experimental animal model of spinal cord stimulation for pain

In spite of the routine usage of spinal cord stimulation (SCS) as treatment of chronic pain, there is an insufficient understanding of the mechanisms underlying its effect. The method was originally developed as a spin-off from experiments demonstrating the inhibitory control of nociceptive signals by the activation of large afferent fibers, and on the basis of these findings the gate-control theory was advanced. Later experiments showed that stimulation of the dorsal columns can inhibit the relay of nociceptive impulses to second-order neurons in the dorsal horn. It should be emphasized that all these experiments were performed with acute noxious stimuli; it is now universally recognized that SCS in patients is preferentially, or exclusively, effective for chronic neuropathic types of pain. For these and other reasons the mode of action of SCS in clinical pain cannot be inferred from these early animal experiments. In ongoing studies we have used animal models of mononeuropathy (rat) in which we have applied SCS acutely or chronically with stimulation parameters similar to those used in patients. In these animals the first component of the flexor reflex appears with a lower stimulus threshold in the nerve lesioned than in the intact, sham-operated leg. SCS was applied at the approximate level of Th-XII during 10-20 min and produced a marked augmentation of the stimulus threshold. This abnormally high threshold was not normalized until 30-60 min after the end of SCS. In awake animals SCS was applied via an implanted spinal electrode and the effect on behavior changes associated with mononeuropathy was studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on long-acting insulin: crystal structure of Arg-B31 human insulin at 2.0A resolution

The crystal structure of Arg-B31 human insulin (ABHI), a long-acting insulin derivative, has been determined at 2.0 A resolution by using X-ray diffraction analysis. The final crystallographic R factor of the structure model after the refinement is 0.189 with the bond length r. m. s deviation of 0.018 A. The refined structure of ABHI showed that the conformation of B-chain C-terminal residues was more stable than that in the native molecule. A striking structural feature of ABHI was an additional ion pair formed between Arg-B31 of molecule I and Glu-B21 of molecule II in a dimer, and three ionic bonds between the neighbouring molecules thereby appeared on the surface of ABHI hexamer. These secondary bonds generated by the insertion of the residue Arg-B31 should make the rate of dissociation of ABHI hexamer slow down when it was injected into the body and the property of protraction should be produced by a 'depot effect'. This ought to be the main structure basis of the prolonged action of ABHI. The results observed here demonstrate that the main idea we used in search for long-acting insulin is reasonable and correct which goes like this: making some additional non-covalent bonds between insulin monomers so as to slow down the dissociation of insulin oligomers and gain the protraction from a 'depot effect', which may be used as a principle in the further research. It also shows an impressive example that the experimental result reported here is in agreement with the theoretical prediction before the structural determination.

Effects of atrial natriuretic factor on patients with renovascular hypertension

Previous studies have shown the effects of atrial natriuretic factor (ANF) on rats with renovascular hypertension (RVH). In the present study low dose alpha-hANF (0.025 microgram/kg/min) was administered intravenously for 60 minutes to seven RVH patients. Results demonstrated an inhibition of renin-angiotensin-aldosterone system (RAAS), reduction of plasma catecholamine and arginine vasopressin(AVP), diuresis and natriuresis, increase of hematocrit and creatinine clearance, and slight decrease of blood pressure. These results showed that most factors involved in the establishment and maintenance of RVH are affected by ANF infusion.

[Transplantation of fetal adrenal medullary to the brain in Parkinson's disease]

The adrenal medullary tissue removed from the fetus donor aborted at the age of 24 weeks was cultured for one week. Approximately 200-300 mg tissue was placed at the head of bilateral caudate in 17 severe patients with PD. Follow-up lasted for 3 to 18 months. Improvement was observed in all patients 3 months after grafting. Clinical analysis showed that the efficacy was significant and that one of the 17 patients relapsed. The response rate of 6 to 12 months was 87.5%. Immediately after operation, the drug was withheld or decreased in dosage. The low density areas in the head of caudate nucleus was found by CT within 1 to 10 days, and disappeared one month after operation. We conclude that the human fetal adrenal medullary tissue can survive in the human brain and is associated with functional effect. Transplantation of the brain tissue is useful in the treatment of PD.