Suppression of sympathetic nervous system attenuates the development of two-kidney, one-clip Goldblatt hypertension

PURPOSE

This study tried to assess the possible contribution of the sympathetic nervous system to the onset of two-kidney, one-clip (2K-1C) Goldblatt hypertension.

MATERIALS AND METHODS

The effect of chlorisondamine administration with or without subsequent splanchnicotomy on the development of hypertension was examined in 2K-1C rats with special reference to norepinephrine synthesis.

RESULTS

The 2K-1C rats were treated either with chlorisondamine or chlorisondamine plus subsequent splanchnicotomy, so that the development of hypertension was effectively arrested for 4 weeks. An apparently high rate of release of norepinephrine in 2K-1C rats was reduced by treatment with chlorisondamine plus splanchnicotomy. A similar trend was also seen in plasma norepinephrine concentration and norepinephrine clearance, to a lesser extent. There were significant positive relationships between percent change of systolic blood pressure and apparent rate of release of norepinephrine, plasma norepinephrine concentration and norepinephrine clearance in 2K-1C rats and 2K-1C + chlorisondamine + splanchnicotomy rats. There were no significant relationships in these parameters in sham-treated rats.

CONCLUSION

Increased sympathetic innervation appears to participate in the development of 2K-1C Goldblatt hypertension.

[Mitral reconstruction in patients with infective endocarditis]

Between June 1992 and October 1993, 5 patients with infective endocarditis in native mitral valve underwent open heart surgery. The patients ranged in age from 51 to 64 years and were all males. According to NYHA functional classification, 4 patients were class II and one was class III. Surgery was indicated because of hemodynamic deterioration (2 pts), echocardiographic mobile vegetation with or without previous emboli (2 pts) and both condition (1 pt). Before surgery the patients were afebrile and had negative serum CRP and negative blood cultures for at least one week after adequate medical treatment. The leaflet lesions found in the 5 patients were vegetation (2 pts), perforation (1 pt), calcification (1 pt) and thickening (2 pts). The chordal lesions found were rupture (5 pts) and thickening (1 pt). The infective lesions did not extend to the annulus. The mitral leaflets, including all apparently infectious lesions, were resected in a V-shaped fashion and then valve reconstruction was performed. The resected parts were sutured together with anchoring chordae. The annuloplasty with Teflon-tapes was also added. Postoperatively, all 5 patients showed a dramatic improvement in hemodynamics and endocarditis did not recur during 22 to 38 months of follow-up. The patients who received the repair did not require Warfarin. This study shows that mitral valve repair is an acceptable operation in patients with infective endocarditis, giving the patients better quality of life than mitral valve replacement when (1) infectious lesion are limited to mitral leaflet and chordae, (2) there is no severe calcification of the mitral valve, (3) the infection is healed by the adequate antibiotic therapy.

Efficient method for rapid induction of aberrant crypt foci in rats with 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) induces aberrant crypt foci (ACFs) as well as colon cancer in F344 male rats. Conditions allowing rapid development of ACFs over a short period were investigated. F344 male rats were fed 400 ppm of PhIP x HCl in a low-fat diet (LF) for 2 weeks and then given a PhIP-free, high-fat diet containing PRIMEX (HF-PR) or safflower oil, or PhIP-free LF for 4 or 12 weeks. Rats fed HF-PR for 4 weeks gave the highest number of ACFs/rat (3.3) and their size in terms of aberrant crypts/ACF (2.7) was much larger than that obtained with conventional continuous feeding of PhIP for 25 weeks in the CE-2 diet. Therefore, 2 weeks of dietary exposure to 400 ppm of PhIP x HCl, followed by HF-PR for 4 weeks, is a practical and convenient method for obtaining ACFs. This protocol should be useful for studies of the early phase of colon carcinogenesis.

[Effects of age and sex on orthostatic change of blood pressure in normal persons]

Orthostatic change of systolic blood pressure was consecutively recorded using oscillometric method in 140 normal persons aged twenties to eighties and analyzed by age and sex. Systolic blood pressure generally increased after standing. The men, especially over the age of 50, failed to increase blood pressure immediately after standing (initial 1-3 minutes), and then increased. In the women, on the other hand, blood pressure generally increased after standing. The mean ratio of the blood pressure elevation for 10 minutes was higher in the women than in the men over 50 years old. Systolic blood pressure tended to fall immediately after the second supine from standing in both sexes. In conclusion, age and sex may influence orthostatic change of blood pressure.

Age-related alteration of cross-linking amino acids of elastin in human aorta

It is well known that the elastic property of human aorta decreases gradually with age. Since the cross-linking structures are responsible for this elasticity, age-related changes of cross-linking amino acids in human aorta were studied using a high-performance liquid chromatography (HPLC). Non-atherosclerotic areas of thoracic aorta of 27 autopsy cases which had no particular aortic disease were obtained. After acid hydrolysis, SEP-PAK silica-gel column and Fe3+/activated charcoal column pretreatment were carried out for analysis of desmosine (DES), isodesmosine (ISDES), neodesmosine (NEO), oxodesmosine (OXO) and isooxodesomosine (ISOXO), and for analysis of aldosine (ALD), respectively. These prepared samples were applied to the reversed-phase HPLC column. We also analyzed pyridinoline (PYR), a major cross-linking amino acid of collagen as an index of fibrosis. All cross-linking amino acids of elastin rapidly increased in infancy and then gradually decreased with age. In the middle- and old-age, the amount of OXO showed marked variety. PYR was little detected at 0-year-old, and then gradually increased with age. The crosslinks of elastin were rapidly formed in childhood and then decreased with age. These findings suggest that the relative increase of NEO, OXO or ISOXO to DES and ISDES is associated with age-related weakening and/or damage of elastin, and that the gradual shift from elastin- to collagen-dominant state is a possible cause of the loss of elasticity and the gain of stiffness in the aging aorta.

Inhibition of natural killer (NK) cell activity against varicella-zoster virus (VZV)-infected fibroblasts and lymphocyte activation in response to VZV antigen by nitric oxide-releasing agents

The addition of nitric oxide (NO)-releasing agents, S-nitroso-N-acetyl-DL-penicillamine (SNAP), 1-hydroxy-2-oxo-2,3-bis(2-aminoethyl)-1-triazene (NOC18), 30{(+/-)-(E)-ethyl-2'-[(E)-hydroxyimino]-5-nitro-3-hexenecarbam oyl} -pyridine (NOR4) significantly inhibited NK cell activity against VZV-infected cells, while antibody-dependent cell-mediated cytotoxicity (ADCC) against VZV-infected cells was unaffected. Interferon-alpha (IFN-alpha) production by non-adherent peripheral blood mononuclear cells (NPBMC) cultured with VZV-infected cells was decreased by the addition of NO-releasing agents. Lymphocyte proliferation and the expression IL-2 receptor (CD25) in response to VZV antigen were also inhibited by the addition of NO-releasing agents. These results suggest that the production of NO by an inflammatory process may lead to inhibition of NK cell- and T cell-mediated immunity to VZV infection.

Administration of granulocyte colony-stimulating factor during remission induction therapy with all-trans retinoic acid for acute promyelocytic leukemia

Granulocyte colony-stimulating factor (G-CSF) enhances the differentiation of acute promyelocytic leukemia (APL) cells induced by all-trans retinoic acid (ATRA) in vitro. Accordingly, we initiated a pilot study on G-CSF in APL patients who developed neutropenia and severe infection during remission induction therapy with ATRA. Seven out of nine treated patients displayed a marked increase in granulocyte counts without leukemic regrowth, and two displayed a dramatic decrease in leukemic blasts. However, leukemic regrowth occurred in two patients under treatment for post-ATRA relapse. Our findings suggest that administration of G-CSF combined with ATRA can improve the hematological state in APL patients not previously receiving ATRA therapy.

Appearance of beta-2-microglobulin in rat hypothalamic magnocellular neurons after hypophysectomy

To clarify the relationship between neuronal cell degeneration and MHC class-I complex expression, we have immunohistochemically examined the distribution of beta(2)-microglobulin in the hypophysectomized rat hypothalamus. In the sham-operated control rats, positive stainings were distributed only in blood vessels in the hypothalamic areas where magnocellular neurons were localized. Three days after hypophysectomy, positive stainings appeared in a large number of magnocellular neurons in the paraventricular and supraoptic nuclei. Most of such beta(2)-microglobulin-positive cells were simultaneously stained with antivasopressin serum. The pattern of distribution of positive cells and the intensity of the stainings remained unchanged at least until the 14th day. These morphological findings suggest that the process of degeneration of hypothalamic magnocellular neurons after hypophysectomy is a useful model to investigate the role of MHC class I complex in the brain.

Amitriptyline inhibits the G protein and K+ channel in the cloned thyroid cell line

We have reported that thyroid K+ channel is activated by extracellular application of the thyroid-stimulating hormone (TSH) using single channel recording method performed on cloned normal rat thyroid cell (FRTL-5) membrane. Treatment of dibutyryladenosine cyclic monophosphate (Bt2 cAMP) also activated the TSH-dependent K+ channel. These findings indicate that the thyroid K+ channel is activated through the TSH-adenosine cyclic monophosphate (cAMP)-protein kinase A system. We examined the effects of amitriptyline on TSH-guanosine triphosphate binding protein (G protein)-adenylate cyclase-cAMP-K+ channel system in the cloned normal rat thyroid cell line FRTL-5. Amitriptyline inhibited the cAMP production induced by TSH. Amitriptyline also inhibited the cAMP production induced by cholera toxin, indicating that amitriptyline inhibited the thyroid G protein. Amitriptyline had no effect on TSH-receptor binding and cAMP production by forskolin (adenylate cyclase stimulator). Amitriptyline inhibited the K+ channel activation by cAMP, indicating that the suppressing mechanism is not the inhibition of TSH receptor or G protein but the direct suppression of K+ channel. It was concluded that amitriptyline inhibited the thyroid G protein and K+ channel.

The evolution of divergences in physician supply policy in Canada and the United States

The size, geographic distribution, and specialty mix of the US physician workforce continue to interest American health policy analysts. Evidence suggests that the United States is on the verge of a serious oversupply of physicians, particularly nongeneralist physicians. Canada faces some of the same problems in physician supply, cost, and distribution as does the United States. Unlike the American states, however, the Canadian provinces, which have responsibility for financing health care, have in recent years made changes in their physician workforce policies that address these problems. Of particular note, Canadian provinces have developed policies that limit medical school enrollments, adjust the specialty training mix to better accord with needs, and establish physician practice location incentives. This article proceeds on the assumption that historical and contemporary similarities between medical care systems in Canada and the United States make comparisons between them potentially valuable. It offers a historical perspective on the evolution of workforce planning in the 2 countries and identifies 3 periods of policy development. It also compares and contrasts the relative size and specialty composition of the Canadian and US workforces and discusses how Canadian initiatives have diverged from American policy. Unless the United States devises its own coordinated workforce strategy, it will have considerable difficulty limiting physician workforce growth and influencing specialization and distribution in the future.

Inductions of Cu/Zn superoxide dismutase- and nitric oxide synthase-like immunoreactivities in rabbit spinal cord after transient ischemia

The distributions and inductions of Cu/Zn superoxide dismutase (SOD), neuronal and endothelial nitric oxide (NO) synthase (nNOS and eNOS), and nitrotyrosine (NT) were immunohistochemically examined in rabbit spinal cords after 5 and 15 min of transient ischemia. The neurons in the anterior horns (AH) were selectively lost 7 days after 15-min ischemia as compared with those of sham-operated controls. In the normal spinal cords, a number of neurons in the AHs were positive for the nNOS, and only slightly positive for the Cu/Zn SOD and the eNOS. Immunoreactivities for the proteins were induced at 8-24 h both after 5- and 15-min ischemia. In contrast, NT-like immunoreactivity was negative both in the normal and postischemic spinal cords. These results suggest that Cu/Zn SOD- and nNOS-, and eNOS-like immunoreactivities are induced, but that, even though an interaction of Cu/Zn SOD with NO could be present, NT was not detected in the motor neurons in the rabbit spinal cords after transient ischemia. Other factors could be required for NT formation found in degenerative motor neuron death in humans.

Increased vascular collagen and noncollagenous protein synthesis contributes to sustain chronic phase of two-kidney, one-clip renovascular hypertension

PURPOSE

Although the enhanced renin-angiotensin (R-A) system responsible for two-kidney, one-clip (2K-1C) hypertension is well known, there may be a shift with time so that this, hemodynamic factor plays a less important role and increased vascular resistance is predominant in sustaining hypertension. While increased vascular protein synthesis has been demonstrated in genetically hypertensive rats, we evaluated the possible relationship between vascular protein synthesis and 2K-1C hypertension with special reference to the R-A system.

MATERIALS AND METHODS

Two-kidney one-clip rats were treated with splanchnicotomy, beta-aminopropionitrile (collagen inhibitor), or captopril (angiotensin converting enzyme inhibitor) in the acute or chronic hypertensive phase. 3H-proline was injected into rats, and incorporation rates of 3H-proline into vascular collagen, noncollagenous protein and elastin were counted. The plasma level of the R-A system was assayed.

RESULTS

In the acute phase of 2K-1C hypertensive rats whose R-A system was enhanced, captopril treatment further enhanced plasma renin activity and plasma angiotensin I and suppressed plasma angiotensin II while reducing blood pressure. Synthesis of the vascular proteins was almost identical. In the chronic phase of 2K-1C hypertensive rats whose R-A system was within normal limits, increased incorporation rates of 3H-proline into noncollagenous protein or collagen of mesenteric arteries were decreased by splanchnicotomy or beta-aminopropionitrile and hypertension was lowered. Captopril failed to reduce protein synthesis.

CONCLUSIONS

An enhanced R-A system participates in the pathogenesis of the acute phase of 2K-1C hypertension while increased noncollagenous protein and collagen syntheses of small arteries appear to play some role in the etiology of the chronic phase of hypertension.

Detection of measles virus-induced apoptosis of human monocytic cell line (THP-1) by DNA fragmentation ELISA

Measles virus (wild strain, Toyoshima strain)-induced cell death is characterized by cell shrinkage, chromatin condensation, and nuclear fragmentation in a human monocytic cell line (THP-1). DNA fragmentation of measles virus-infected THP-1 cells was demonstrated by DNA agarose gel electrophoresis as well as by DNA fragmentation ELISA. When measles virus-infected THP-1 cells were cultured on monolayers of fibroblasts or human umbilical vein endothelial cells (HUVEC), the percentage of measles virus antigen-positive THP-1 cells and DNA fragmentation were significantly decreased. Addition of anti-intercellular adhesion molecule (ICAM)-1 (CD54) monoclonal antibody to culture of measles virus-infected THP-1 cells reduced significantly DNA fragmentation induced by measles virus. These findings suggest that inhibition of virus spread by fibroblasts and HUVEC reduces apoptosis, and ICAM-1 (CD54) may participate in the DNA fragmentation pathway.

Modulation of target tissue response to angiotensin II and sodium sensitivity in Japanese patients with essential hypertension

"Non-modulators" are essential hypertensive patients who fail to modulate an adrenal response, renovascular response, or both, to angiotensin II (Ang II). The aim of the present study was to characterize "non-modulators" among Japanese patients with normal-renin essential hypertension and to determine whether non-modulation is related to sodium sensitivity of blood pressure. The increase in plasma aldosterone concentration (PAC response) and the decrease in renal plasma flow (RPF response) in response to Ang II infusion (3 ng/kg/min) were assessed in 15 Japanese patients with essential hypertension who received a high sodium diet (250 mEq/d) followed by a low sodium diet (10 mEq/d). The subjects were divided into two groups (6 modulators and 9 non-modulators) based on their ability to modulate the PAC response during sodium restriction. There was no significant difference between modulators and non-modulators in electrolyte balance or in plasma Ang II levels on either diet. Changes in the PAC response during sodium restriction were significantly correlated with the change in mean blood pressure during sodium restriction (r = -0.67, p < 0.01), while changes in the RPF response were not. RPF responses in both groups decreased during sodium restriction, although an effect on the RPF response in non-modulators was unexpected. These results suggest that non-modulators do exist among Japanese patients, but that this defect does not involve both the adrenal gland and the kidney. Apparently, only non-modulation of the adrenal response is involved in the mechanism of sodium sensitivity.

Mitotic and meiotic stability of the CAG repeat in the X-linked spinal and bulbar muscular atrophy gene

X-linked spinal and bulbar muscular atrophy (SBMA) occurs due to an expansion of the trinucleotide repeat (CAG)n in the androgen receptor gene. Anticipation is relatively rare in SBMA in contrast to spinocerebellar ataxia type 1 (SCAl), and dentatorubral and pallidoluysian atrophy (DRPLA) which show obvious paternal anticipation. The differences in the CAG repeat number were compared among sperm, leukocytes and skeletal muscles of SBMA patients. In SBMA, the sperm of most patients and the skeletal muscle of all patients showed the same repeat number as their leukocytes, whereas the increase in the repeat number from leukocytes to sperm was evident in SCA1 and DRPLA patients. The higher mosaicism level in sperm compared with leukocytes was common in SBMA, SCA1 and DRPLA, and the level of sperm was lower in SBMA than in SCA1 and DRPLA. Thus, spermatogenesis was suggested to be strongly associated with paternal anticipation. The mosaicism level was smaller in SBMA than in other (CAG)n expanded disorders, and smallest in the SBMA carrier females. These findings demonstrate that the CAG repeat in SBMA is relatively stable in mitotic and meiotic, processes, and there is a possibility that the lower mosaicism level of the carrier females compared with the SBMA patients is associated with X-linked recessive inheritance.

Characteristics of Ca2+ release for activation of K+ current and contractile system in some smooth muscles

Characteristics of Ca2+ release from stores were investigated in strips from ileum and portal vein and in isolated myocytes from ileum and urinary bladder of the guinea pig with use of caffeine and 9-methyl-7-bromoeudistomin D (MBED), a potent releaser of Ca2+ from skeletal muscle sarcoplasmic reticulum. In skinned strips, 1-30 mM caffeine elicited a transient contraction, but 10-300 microM MBED did not. Pretreatment with 100 microM MBED did not affect the subsequent caffeine-induced contraction. In single cells loaded with indo 1-acetoxymethyl ester, 10 mM caffeine increased cytoplasmic Ca2+ concentration, whereas 100 microM MBED elicited a small or no increase. Under whole cell clamp, spontaneous transient outward currents through Ca(2+)-dependent K+ (BK) channels were first enhanced and then suppressed by 30 microM MBED or 5 mM caffeine. The amplitude of Ca(2+)-dependent transient K+ current on depolarization was reduced by MBED and caffeine (50% inhibitory concentrations = 20 microM and 1 mM, respectively). Other currents and single BK channel activity were not significantly affected by MBED. The Ca2+ release from stores responsible for BK channel activation may be resolved from that for the activation of the contractile system by MBED in these smooth muscle cells.

Determination of bioconcentration potential of tetrachloroethylene in marine algae by 13C

The use of stable isotope of organic-carbon, organic-13C, as a tracer for the determination of the concentration of tetrachloroethylene (PCE), CA, in Heterosigma akashiwo and Skeletonema costatum was examined. CA determined by the 13C and GC methods showed good agreement with each other. This suggests that it is reasonable and reliable to determine the bioconcentration potential of PCE in marine algae. Fitting values of bioconcentration potential parameters, including uptake rate constant k1, elimination rate constant k2 and bioconcentration factor on the basis of dry weight BCFD, were done not only to the time course for PCE uptake by the algae with the bioconcentration model, but also to experimental data for "percent inhibition(%) approximately exposure concentration of PCE approximately time" with the combined bioconcentration and probability model. The values obtained from the bioconcentration model were consistent with those from the combined bioconcentration and probability model. With the parameters (such as k1, k2, growth rate constant kG, critical concentration of HOCs in the organism resulting in growth inhibition CA* and spread factor S) the variability in toxicity (such as EC10, EC50, EC70) can be estimated from the combined bioconcentration and probability model, which fits well with the experimental observations.

[Early steroid withdrawal after kidney transplantation]

BACKGROUND

The side effects of steroid are serious problems in renal transplant patients. However, withdrawal of steroid has been controversial. We evaluated the benefits and risk of early steroid withdrawal after renal transplantation.

PATIENTS AND METHODS

The outcomes of early steroid withdrawal from triple immunosuppressive drug therapy were analyzed in four living related and one cadaveric renal transplant recipients. The dosage of steroid was gradually reduced and the time of steroid withdrawal after transplantation was 5 to 7.5 months.

RESULTS

Four Patients have been able to be free from steroid and maintained stable graft functions and normal urinary findings for 14 to 33 months after withdrawal. The findings of rejection were not observed in the graft specimens obtained by serial biopsies. One patient who received a living related graft developed an increase in serum creatinine level and proteinuria two weeks after discontinuation of steroid. The serum creatinine level returned to that before withdrawal and proteinuria disappeared by steroid readministration. Long term side effects of steroid were not observed in 4 patients with successful steroid withdrawal.

CONCLUSION

These results suggest that steroid withdrawal about 6 months after transplantation can be accomplished without jeopardizing graft function in selected renal transplant recipient and the withdrawal in the early stage is preferred for reducing the side effects. Careful and long-term follow up are required to assess the further risk and benefit of steroid withdrawal on immunosuppressive morbidity.

Quantitative endoscopic classification of esophagitis by means of computerized image processing. Part II: Experimental study

Digital processing of video-endoscopic images in esophagitis appears to be a useful method for quantifying mucosal color changes, with a potential to provide improved reproducibility in the follow up of individual cases and in comparison between patients and groups of patients. However, the sources of error such as type of equipment, the distance of the endoscope tip to the cardia, axial positioning of the endoscope in the esophagus, and the distance from the endoscope tip to the area of interest must be taken into account.

Reward expectancy in primate prefrontal neurons

The prefrontal cortex is important in the organization of goal-directed behaviour. When animals are trained to work for a particular goal or reward, reward 'expectancy' is processed by prefrontal neurons. Recent studies of the prefrontal cortex have concentrated on the role of working memory in the control of behaviour. In spatial delayed-response tasks, neurons in the prefrontal cortex show activity changes during the delay period between presentation of the cue and the reward, with some of the neurons being spatially specific (that is, responses vary with the cue position). Here I report that the delay activity in prefrontal neurons is dependent also on the particular reward received for the behavioural response, and to the way the reward is given. It seems that the prefrontal cortex may monitor the outcome of goal-directed behaviour.

Preliminary examination of the influence of incubation time or cytosolic protein concentration on dihydropyrimidine dehydrogenase activity

We examined the influence of incubation time or cytosolic protein concentration on the metabolite production of 5-fluorouracil (5FU). Although the activity of dihydropyrimidine dehydrogenase (DPDase) from rat liver is considered to be retained for up to 60 min, the production rate of 5FU metabolites was reduced, probably due to depletion of the substrate in 40 mumol/l and lower concentration of 5FU. Since the ratio of the metabolite production rate to the cytosolic protein became smaller in higher concentrations of cytosolic protein, the DPDase activity should be compared in the same concentration of cytosolic protein. The production rate of 5FU metabolites was considered to be linear up to 40 mumol/l 5FU incubated with 500 micrograms cytosolic protein. The rate of the metabolite production calculated by one-point sampling significantly correlated with the enzyme activity by the multi-point sampling method. Minimizing sampling points to determine the DPDase activity would save time and expense.

EAAT4 is a post-synaptic glutamate transporter at Purkinje cell synapses

To study cellular and subcellular localizations of the glutamate transporter EAAT4, antibody was raised against the N-terminal peptide. On immunoblotting the antibody recognized a band in membrane extracts from the cerebellum, but not from the forebrain. Immunohistochemistry revealed that its distribution was restricted to the cerebellar molecular layer, where the immunoreactivity was observed as numerous punctate stainings. Electron microscopy showed the antibody to label dendritic spines of the Purkinje cells. EAAT4 is, therefore, a Purkinje cell-specific, postsynaptic transporter. Together with dense localization of other transporter subtypes in Bergmann astrocytic membranes, Purkinje cell synapses are thus provided with distinct glutamate transporter subtypes at discrete synaptic elements, which would play important roles in regulating excitability of the Purkinje cells and protecting against excitotoxicity.

Effects of insulin on calcium metabolism and platelet aggregation

The influence of insulin on platelets in vitro has not been exhaustively investigated. To clarify whether insulin affects Ca2+ metabolism in platelets directly or through alteration of other systems regulating intracellular Ca2+ homeostasis, we examined the effect of insulin both alone and in combination with prostaglandin E1 on platelet aggregation and Ca2+ metabolism. Incubation of rat platelets with insulin reduced thrombin-induced Ca2+ influx but did not change thrombin-evoked release of Ca2+ from internal stores or the size of internal Ca2+ stores. The interactive effects of insulin with prostaglandin E1 were only additive, and insulin did not augment the effects of prostaglandin E1 on platelet Ca2+ metabolism. In contrast, insulin did not inhibit thrombin-induced platelet aggregation but did augment inhibition of platelet aggregation by prostaglandin E1. Our results suggest that insulin inhibits platelet function by both prostaglandin E1-dependent and -independent mechanisms.

Transgenic mice overexpressing glutathione peroxidase are resistant to myocardial ischemia reperfusion injury

To test the authors' hypothesis that cellular antioxidant enzymes constitute a cellular defense against acute stress, myocardial ischemia reperfusion injury in transgenic mice overexpressing the cellular glutathione peroxidase (GSHPx-1) was studied. Transgenic mice were generated using the entire mouse GSHPx-1 gene including approximately 2.0 kb 5'flanking sequence. A 400% increase of GSHPx activity was found in the hearts of transgenic mice compared with non-transgenic controls. Isolated perfused hearts were prepared from two groups of mice: transgenic overexpressed; non-transgenic controls. Hearts were perfused by Langendorff mode, and after 10 min of stabilization subjected to 30 min of ischemia followed by 20 min of reperfusion. In addition, a group of hearts were perfused for 50 min without subjecting them to ischemia and reperfusion to demonstrate the stability of heart preparation. Transgenic mouse hearts demonstrated significantly improved recovery of contractile force and the rate of contraction, compared to non-transgenic control mouse hearts. The infarct size was also lower in transgenic mouse hearts compared to those of non-transgenic controls. In concert, following ischemia, release of creatine kinase from the transgenic hearts was significantly lower than the control group. The results of this study indicate that increased GSHPx-1 expression renders the heart more resistant to myocardial ischemia reperfusion injury.