Perindopril treatment in the prevention of stroke in experimental animals

OBJECTIVE

To determine the effect of perindopril treatment and treatment withdrawal in the prevention of stroke in male stroke-prone spontaneously hypertensive rats (SPSHR).

DESIGN

After weaning at 4 weeks of age, male SPSHR were given a Japanese-style rat diet which induces stroke in these animals. Beginning at 6 weeks of age, SPSHR were treated with either distilled water (control) or different daily dosages of perindopril (1 or 4 mg/kg) by gavage for 24 weeks followed by treatment withdrawal. Additional subgroups were treated with the 4 mg/kg dose for different durations (B, 12 or 24 weeks) before treatment withdrawal. Treatment effects on blood pressure, heart rate and body weight were studied during the treatment period and after the withdrawal of the treatment. Myogenic and mechanical properties of the middle cerebral arteries were studied in control SPSHR that had developed stroke, in treated SPSHR at the end of the treatment period, and at certain intervals after the withdrawal of the treatment.

METHODS

Systolic blood pressure, heart rate and body weight of control and treated SPSHR were determined at regular intervals before, during and after the treatment withdrawal periods until they died from stroke, or until 42 or 43 weeks of age when the study was terminated. Functional studies of the cerebral arteries were carried out using a pressurized artery system. At necropsy, macroscopic and microscopic examinations were made of the kidneys and brain.

RESULTS

Untreated SPSHR usually died of stroke-related complications by 14 weeks of age. The middle cerebral arteries from these animals had lost their ability to contract in response to pressure increase. Chronic treatment of SPSHR with perindopril when initiated at 6 weeks of age attenuated the sharp blood pressure rise, and prevented the development of stroke during the treatment period. This was associated with the preservation of the myogenic response of the middle cerebral arteries to pressure increase, and the prevention of tissue damage in the kidneys and brain. After withdrawal of the treatment, SPSHR treated for a longer period (12 or 24 weeks) also survived longer than those treated for a shorter period (8 weeks). The subsequent loss of myogenic response in the middle cerebral arteries was associated with the development of stroke and death in these treatment withdrawal groups.

CONCLUSION

Chronic treatment with perindopril is beneficial for the prevention of stroke in SPSHR, through the preservation of the myogenic response properties of the cerebral arteries, and the attenuation of tissue damage in the brain and kidneys.

Direct PCR analysis for toxigenic Pasteurella multocida

A more rapid, accurate method to detect toxigenic Pasteurella multocida is needed for improved clinical diagnosis, farm biosecurity, and epidemiological studies. Toxigenic and nontoxigenic P. multocida isolates cannot be differentiated by morphology or standard biochemical reactions. The feasibility of using PCR for accurate, rapid detection of toxigenic P. multocida from swabs was investigated. A PCR protocol which results in amplification of an 846-nucleotide segment of the toxA gene was developed. The PCR amplification protocol is specific for toxigenic P. multocida and can detect fewer than 100 bacteria. There was concordance of PCR results with (i) detection of toxA gene with colony blot hybridization, (ii) detection of ToxA protein with colony immunoblot analysis, and (iii) lethal toxicity of sonicate in mice in a test set of 40 swine diagnostic isolates. Results of an enzyme-linked immunosorbent assay for ToxA agreed with the other assays except for a negative reaction in one of the 19 isolates that the other assays identified as toxigenic. In addition to accuracy, as required for a rapid direct specimen assay, toxigenic P. multocida was recovered efficiently from inoculated swabs without inhibition of the PCR. The results show that PCR detection of toxigenic P. multocida directly from clinical swab specimens should be feasible.

Effects of chronic blockade of angiotensin II receptor on the maintenance of hypertension and vascular changes in spontaneously hypertensive rats

Previous studies have shown that chronic treatment of spontaneously hypertensive rats (SHR) with angiotensin converting enzyme inhibitors is effective in causing the regression of hypertension and vascular structural changes in adult SHR. The purpose of this study was to determine the involvement of angiotensin type 1 receptors in the maintenance of hypertension and vascular changes in adult SHR. Three groups of 15-week-old male SHR were treated with three different doses of the angiotensin type 1 receptor antagonist L-158,809. After 12 weeks of treatment, average systolic blood pressure was reduced in a dose-dependent manner from 206 +/- 2 mmHg (1 mmHg = 133.3 Pa) in the control SHR to 154 +/- 7 mmHg in the 0.6 mg/kg group, 172 +/- 3 mmHg in the 0.3 mg/kg group, and 196 +/- 8 mmHg in the 0.1 mg/kg group. Withdrawal of the treatment caused a rapid rise in blood pressure within 1 week, and 14-16 weeks after treatment had been withdrawn, blood pressure of SHR treated with the highest dose had increased to 169 +/- 8 mmHg. Blood pressure of the SHR treated with the two lower doses had increased to the level of the untreated SHR. Mean blood pressure, diastolic pressure, and pulse pressure were significantly reduced in the SHR treated with 0.6 mg/kg L-158,809. The arterial media cross-sectional area and media to lumen ratio were reduced by L-158,809 treatment (0.6 mg/kg dose). Treatment did not affect body weight or heart rate. Contractile response of the mesenteric arteries to nerve or norepinephrine stimulation was not affected by the treatment. However, arteries from treated SHR did not show an angiotensin II potentiation of nerve-stimulated response, as was observed in the control SHR. We conclude that persistent control of blood pressure by treatment with L-158,809 is associated with its effects on the structure and function of the arteries in the SHR.

Lipoprotein and apolipoprotein secretion by a newborn piglet intestinal cell line (IPEC-1)

The aim of these studies was to characterize the synthesis and secretion of lipoproteins and apolipoprotein B (apo B) and apo A-I by a newborn swine intestinal epithelial cell line (IPEC-1). Differentiated cells exhibited enterocytic features, including microvilli. [3H] oleic acid was taken up and incorporated into cellular lipids and secreted into the basolateral medium in lipoproteins. Total apo B and apo A-I secreted increased with oleic acid incubation. However, cellular apo B and apo A-I content did not change. Whereas undifferentiated cells synthesized and secreted only apo B-100, both apo B-100 and apo B-48 were produced by differentiated cells. The ratio of radiolabeled apo B-48 to apo B-100 in both basolateral medium and cell homogenate increased with oleic acid treatment after 24-h steady-state labeling. However, apo B mRNA editing was unchanged, indicating posttranslational regulation of this ratio. Pulse-chase radiolabeling demonstrated no major changes in cellular or basolateral medium apolipoprotein labeling kinetics with oleic acid or dexamethasone incubation. The dissociation of apo B and apo A-I mass secretion from the secretion of radiolabeled apo B and apo A-I in response to oleic acid absorption suggests the presence of an intracellular pool of apolipoprotein with a slow turnover that is mobilized for secretion in response to fatty acid uptake.

Pathophysiology of smooth muscle in hypertension

Structural changes of the arteries in hypertension are determined by the unique genetics of the animals and by various growth promoters and growth inhibitors. Vascular smooth muscle cell growth promoting factors include fibroblast growth factor, platelet-derived growth factor, and vasoactive peptides such as norepinephrine, angiotensin II, and endothelin. Endothelial cells secrete three types of growth inhibiting factors. These are heparin--heparan sulfate, transforming growth factor beta, and nitric oxide. The effect of sympathetic innervation on vascular growth is probably dependent on its interaction with the renin-angiotensin system. In the mesenteric vascular bed, the elevated resistance in the arterial system is present in both the macroarteries and in the more distal microarteries and veins. Changes in resistance arteries include hypertrophy and reduction in outer diameter (remodelling). In the resistance arteries from human essential hypertensives, remodelling is the predominant finding. Long-term treatment with an angiotensin I converting enzyme inhibitor but not with a beta-blocker was effective in reversing this type of vascular change. Studies have suggested that in addition to angiotensin II, endothelin may play a role in vascular remodelling of resistance arteries.

Alterations in beta-adrenoceptors and polyploidy in cultured aortic smooth muscle cells from different age groups of spontaneously hypertensive rats and Wistar-Kyoto rats

OBJECTIVE

The relationship between the number of beta-adrenoceptors and polyploidy in cultured aortic smooth muscle cells derived from different age groups of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were examined.

DESIGN

The number of beta-adrenoceptors, the percentage of multinucleated cells and the incidence of polyploidy from cultured smooth muscle cells derived from SHR and WKY rats aged 3-4, 10-12 and 28-30 weeks were measured. The effect of passaging of the cells on the expression of beta-adrenoceptors and polyploidy on cultured smooth muscle cells from both SHR and WKY rats was also investigated.

METHODS

Receptor binding experiments were carried out using [125]-monoiodocyanopindolol with osmotically lysed cultured aortic smooth muscle cells to investigate the properties of vascular beta-adrenoceptors in SHR and WKY rats. The proportion of polyploid smooth muscle cells was determined by frequency distribution analyses of Feulgen DNA microdensitometric measurements.

RESULTS

The incidence of polyploid smooth muscle cells was consistently higher in cells cultured from SHR than in those from WKY rats in all three age groups, with a positive correlation between polyploidy and age in SHR. Furthermore, in all three age groups the number of beta-adrenoceptor binding sites was also higher in cultured smooth muscle cells from SHR than in those from WKY rats. There was no significant difference in the receptor affinity. The increase in beta-adrenoceptor number was associated with an increase in polyploidy, and both of these changes were positively correlated both with the age of the rats from which these cells were derived and with the number of passages.

CONCLUSIONS

Under cell culture conditions the expression of beta-adrenoceptor density increases with the number of passages in both SHR and WKY rats. Smooth muscle cells derived from older SHR and WKY rats have a greater propensity to develop polyploidy. This trend is significantly accelerated in cultured smooth muscle cells derived from SHR compared with those from WKY rats, suggesting a premature ageing process. These findings suggest that, in cultured smooth muscle cells from SHR and WKY rats, beta-adrenoceptors may influence the expression of polyploidy.

Mottled cyan opacification of the posterior cornea in contact lens wearers

PURPOSE

We studied patients who had mottled cyan-colored opacities of the cornea to better understand the cause and prognosis of this entity.

METHODS

We reviewed examinations of patients who had a mottled cyan opacification of the cornea. Risk factors, including contact lens wear and exposure to heavy metals, were analyzed. Clinical findings, pachymetry specular microscopy, and progression of the abnormality were noted.

RESULTS

Six patients who had a mottled cyan opacification at the level of Descemet's membrane were identified. These opacities were located in the peripheral and midperipheral cornea. All patients had bilateral findings, had visual acuities of 20/20 or better, and were asymptomatic. All patients had worn soft contact lenses bilaterally for periods ranging from seven to 14 years.

CONCLUSION

All patients had the similar clinical appearance of a mottled cyan opacification at the level of Descemet's membrane in the peripheral cornea. Long-term contact lens wear appears to be associated; however, the exact cause is unclear.

Perindopril treatment prolonged the lifespan of spontaneously hypertensive rats

OBJECTIVE

The effects of perindopril treatment on hypertension development and the lifespan of adult spontaneously hypertensive rats (SHR) were studied.

DESIGN

Adult male SHR (aged 15 weeks) were given once a day treatment with 4 mg/kg perindopril by gavage for 12 weeks. Littermates given distilled water were used as controls. The blood pressure and lifespan of these rats were studied.

METHODS

The systolic blood pressure (SBP), heart rate and body weight of these rats were measured at regular intervals until they died from natural causes. At necropsy macroscopic and microscopic examinations were made of various organs to determine the cause of death. Serum levels of creatinine, urea and protein were also measured.

RESULTS

Perindopril treatment resulted in the normalization of SBP after 2 weeks of treatment. Withdrawal of the treatment after 12 weeks of treatment caused an elevation of SBP, but the blood pressure of the treated SHR had remained in the normotensive range (< or = 150 mmHg). The heart rate and body weight of the SHR were not affected by the treatment. The average lifespan of the SHR was increased by 12 weeks compared with the control rats. The heart weight, brain lesions and arterial lesions were reduced by the treatment.

CONCLUSION

A 12-week treatment of adult SHR with perindopril was effective in causing a permanent prevention of hypertension, amelioration of some of the tissue damage associated with hypertension and an increase in the lifespan of these rats.

Morphology of cerebral arteries

A comparison of the major cerebral arteries between humans and rats shows many similarities, including anomalies in their general organization, the structure of these vessels at the light and electron microscope levels and their morphological changes associated with cerebral vascular diseases. The general organization of the major cerebral arteries shows the following main differences between humans and rats. In rats, the internal carotid arteries have become an integral part of the circle of Willis. In the anterior cerebral arteries, a common variation in humans is the underdevelopment of one of the two arteries, whereas in rats, buttonhole-like structures are common in one or both arteries. The anterior communicating artery present in humans is absent in rats. The olfactory artery is prominent in rats, but absent in humans. The posterior communicating artery in humans is the most variable component of the circle of Willis, being asymmetric in its origin, diameters and branches. Similarly, the posterior cerebral arteries in rats often exhibit asymmetrical origin from the basilar artery. There was some confusion in the literature regarding the name of the posterior cerebral arteries in rats, but this was caused mainly by misquotations and incorrect interpretations of the papers. In humans, most aneurysms occur in the anterior half of the circle of Willis, and the incidence is higher in females than males; the middle cerebral artery is most often the one to become occluded, and the vertebral arteries are common sites for thrombosis. The various channels that constitute collateral circulation in humans provide a margin of safety, so that in case of cerebral occlusion due to thrombosis, atherosclerosis, or vasospasm related to hemorrhage, blood supply to the affected area can be maintained through these collaterals. Collateral circulation is also present in rats. However, in rats, information on the presence of various types of aneurysms, their location and frequency in normal and experimental models of hypertension and stroke is still lacking. Cerebral arteries from humans and rats are characterized by the absence of external elastic lamina, as compared with systemic arteries. A type of multipolar cell resembling the interstitial cell of Cajal is present in the cerebral arteries of humans. Its function is unknown. Earlier reports of cerebral valves have been shown to represent intimal cushions near the branching points of the cerebral arteries. Intravascular bridges present in human cerebral arteries, have not been reported in rats. Finally, the presence of vascular remodeling, as found in the cerebral arterioles of hypertensive rats, remains to be established in the cerebral arterioles of human hypertensives.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of perindopril on hypertension and stroke prevention in experimental animals

BACKGROUND

Among the antihypertensive agents available for the treatment of hypertension, only angiotensin-converting enzyme (ACE) inhibitors have been shown to modify cardiovascular changes in structure and function.

OBJECTIVE

To study the effect of perindopril treatment on hypertension and stroke prevention in two genetic models of hypertensive rats.

DESIGN

Adult (15 weeks old) spontaneously hypertensive rats (SHR) were treated with perindopril to determine the dose- and duration-dependent effects of treatment on systolic blood pressure, and the effect of withdrawal of this treatment on blood pressure and survival. In stroke-prone SHR, treatment was initiated in young animals (six weeks), and dose- and duration-dependent effects of perindopril treatment on stroke prevention were assessed.

RESULTS

In adult SHR, perindopril caused a dose-dependent lowering of blood pressure. Blood pressure was controlled for a 24 h period with a single daily dose. The magnitude of rebound hypertension after withdrawal of treatment was negatively correlated with duration of treatment. After 12 weeks of treatment, the blood pressure of treated SHR remained normotensive without further treatment, and the life span of treated SHR was also extended. Treatment of young, stroke-prone SHR with perindopril prevented stroke in these animals during the treatment period. After withdrawal of treatment, survival of the rats was increased in animals given a longer treatment period (24 weeks versus eight or 12 weeks).

CONCLUSION

Treatment with the ACE inhibitor perindopril is effective in the prevention of hypertension and stroke in experimental animals.

Fish oil, essential fatty acids, and hypertension

A proper balance between the n-3 and n-6 series of essential fatty acids (EFAs) is essential for homeostasis and normal growth in humans. Dietary supplement with fish oil and related n-3 EFAs has been used to study their antihypertensive property in animals and humans with borderline and essential hypertension. In the animal models, chronic treatment of young animals generally only attenuated the development of hypertension. In animals with hypercholesterolemia, n-3 EFA supplement increased the incidence of atherosclerosis. In humans, chronic treatment with fish oil only produced a small reduction in blood pressure. The concerns are that the high dose of fish oil may interfere with the control of blood glucose in diabetic patients, and may cause prolonged bleeding in surgical patients. Studies on the animal models of hypertension showed that n-6 EFAs are more effective than n-3 EFAs in lowering and normalizing the blood pressure of these animals, probably through the production of tissue prostaglandins, which favour vasodilation. The antihypertensive effect of the n-6 EFAs in humans is not well known, because there are only a few studies, usually involving a very small number of patients. A possible side effects of n-6 EFAs for concern is that they might stimulate tumour development. A careful examination of these risk factors is needed before any recommendation can be made concerning the use of EFAs for the control of hypertension for humans.

Arterial hypertrophy and pressor responsiveness during development of hypertension in spontaneously hypertensive rats

BACKGROUND

In contrast to studies in isolated blood vessels, results from whole-animal studies are ambiguous regarding differences in pressor responsiveness between spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats, possibly related to the measurement of blood pressure instead of total peripheral resistance (TPR) and to differences in compensatory mechanisms.

OBJECTIVE AND DESIGN

We evaluated responses of blood pressure and TPR to two doses of the alpha 1-agonist phenylephrine during the development of hypertension and cardiovascular hypertrophy in SHR aged 8-26 weeks compared with age-matched WKY rats before and after ganglionic blockade. At 16 weeks of age more-complete dose-response curves to the alpha 1-agonist methoxamine were also constructed.

RESULTS

Over the age range studied, the SHR developed marked hypertension, related to a significant rise in TPR, and concomitantly significant cardiac hypertrophy, as well as hypertrophy of the mesenteric arterial bed. The blood pressure responses to phenylephrine were diminished in the SHR compared with the WKY rats at all ages studied, but this effect was significant only in the absence of ganglionic blockade. TPR responses were significantly less in the SHR than in the WKY rats, both with and without concomitant ganglionic blockade. In contrast, both blood pressure and TPR responses to low doses, but not higher doses, of methoxamine were enhanced in the SHR compared with the WKY rats.

CONCLUSION

These results indicate that the development of hypertension in SHR in vivo is associated with variable changes in blood pressure and TPR responses to alpha 1-receptor stimulation, depending on the alpha 1-agonist employed.

Effects of sarcoplasmic reticulum calcium pump inhibitors on vascular smooth muscle

A dysfunctioning of Ca2+ pump ATPase in the sarcoplasmic reticulum in vascular smooth muscle has been proposed as a contributing factor for the development of genetic hypertension. In this study, we determined whether in vitro inhibition of the sarcoplasmic reticulum Ca2+ pump in vascular smooth muscle tissues and cultured cells isolated from aortas of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats would elicit the known alterations of contractile function and cell growth. We found the following common vascular effects of thapsigargin and cyclopiazonic acid, which are known to be selective inhibitors of sarcoplasmic reticulum Ca(2+)-ATPase in a number of tissues including smooth muscle: (1) Both sarcoplasmic reticulum Ca2+ pump inhibitors diminished agonist-induced transient contraction in Ca(2+)-free medium (ie, contraction due to intracellular release of Ca2+) and enhanced nifedipine-sensitive contraction on readmission of Ca2+ (ie, Ca2+ influx via L-type channels); and (2) thapsigargin and cyclopiazonic acid inhibited the attachment of cultured aortic muscle cells to the substrate in a similar degree in both SHR and WKY cells, but SHR cells were more sensitive than WKY cells to the inhibition of cell proliferation by these two agents. The first effect may provide an explanation for several contractile abnormalities known to be associated with elevated cytosolic Ca2+ concentration, whereas the second effect suggests that elevation of cytosolic Ca2+ in aortic smooth muscle cells is not necessarily associated with or sufficient to account for the accelerated cellular proliferation in SHR. These results, however, further stress the functional importance of impairment of Ca2+ regulation in vascular smooth muscle cells in genetic hypertension.

Effects of the arterial vasodilator minoxidil on cardiovascular structure and sympathetic activity in spontaneously hypertensive rats

OBJECTIVE AND DESIGN

In spontaneously hypertensive rats (SHR) arterial vasodilators do not cause regression and might cause further progression of cardiac hypertrophy. To assess whether these effects extend to the vasculature, and to examine the possible mechanisms involved, cardiac and mesenteric arterial structure was evaluated with respect to changes in cardiac volume load and cardiac and arterial sympathetic activity during long-term (5- and 10-week) treatment of 16-week-old SHR with the arterial vasodilator minoxidil, alone or in combination with the diuretic hydrochlorothiazide.

RESULTS

Despite causing a persistent decrease in blood pressure in SHR, minoxidil further increased left and right ventricular weights and left ventricular internal diameter. In combination with hydrochlorothiazide, minoxidil caused concentric, rather than eccentric, left ventricular hypertrophy. In the mesenteric arterial bed of SHR, minoxidil increased the lumen of the superior mesenteric artery, and prevented further increases in the medial area of the large and small mesenteric arteries. The increase in lumen size of the superior mesenteric artery by minoxidil was abolished when hydrochlorothiazide was added to the treatment. After 10 weeks' treatment with minoxidil, noradrenaline turnover rates were still significantly increased in the left ventricle but were decreased in the mesenteric arteries in the SHR. Minoxidil increased plasma and blood volumes, the increases being largely prevented by concomitant diuretic treatment.

CONCLUSIONS

We conclude that there are regional differences in the response of the cardiovascular system to minoxidil in SHR. Some of these differences may be related to differences in regional sympathetic activity, whereas volume load appears to play a modulatory role.

Measurement of both cyclic [3H]AMP and cyclic [3H]GMP in cultured vascular smooth muscle cells labeled with [3H]hypoxanthine: use in studies of cardiovascular drugs

We describe a method for prelabeling cultured vascular smooth muscle cells that permits rapid and accurate measurements of changes in the amounts of cyclic AMP and of cyclic GMP in 5 x 10(5) cells. This procedure utilizes [3H]hypoxanthine to radiolabel both the adenine and guanine nucleotide pools and simple column chromatographic steps to isolate and separate the 3H-labeled cyclic nucleotides. The application of the method to studies of the actions of cardiovascular drugs on vascular smooth muscle cells is illustrated by measurements of the effects of isoproterenol, nitroprusside, and inhibitors of cyclic AMP phosphodiesterases on the cyclic nucleotide levels in these cells. If required, the mass amounts of cyclic AMP and cyclic GMP present could be determined by measurement of the specific radioactivities of the precursor [3H]ATP and [3H]GTP, respectively. The cyclic nucleotide values calculated by the latter method were almost identical to those obtained with larger numbers of cells using commercially available radioimmunoassays, thus validating the prelabeling assays. The method described should be applicable to any type of cultured cell that can utilize [3H]hypoxanthine to replenish its ATP and GTP pools.

The effect of lactation on glucose and lipid metabolism in women with recent gestational diabetes

OBJECTIVE

To investigate the effect of lactation in the puerperium on glucose and lipid metabolism in women with recent gestational diabetes.

METHODS

In women with recent gestational diabetes, we examined the effect of 4-12 weeks of lactation on glucose tolerance (2-hour oral glucose tolerance test) and on fasting serum lipids (total cholesterol, high-density lipoprotein [HDL] cholesterol, low-density lipoprotein [LDL] cholesterol, and triglycerides). Of 809 women tested in the puerperium, 404 elected to breast-feed and 405 did not lactate.

RESULTS

The mean (+/- standard deviation) maternal age (31.6 +/- 5.9 versus 30.5 +/- 6.3 years), body mass index (28.8 +/- 5.1 versus 28.8 +/- 4.5 kg/m2), and parity (3.0 +/- 1.6 versus 2.8 + 1.7) were not different between the lactating and nonlactating groups, respectively. Glucose metabolism improved in the lactating group, indicated by a significantly lower total area under the glucose tolerance curve (17.0 +/- 4.2 versus 17.9 +/- 5.0 g.minute/dL; P = .01), mean fasting serum glucose (93 +/- 13 versus 98 +/- 17 mg/dL; P = .0001), and mean 2-hour glucose level (124 +/- 41 versus 134 +/- 49 mg/dL; P < .01). These differences were significant after adjusting for maternal age, body mass index (BMI), and the use of insulin in pregnancy. Nursing had no effect on total cholesterol, LDL cholesterol, or triglyceride levels. However, the mean serum HDL cholesterol was elevated in the lactating group after adjusting for maternal age, BMI, and pregnancy insulin use compared with the nonlactating group (48 +/- 11 versus 44 +/- 10 mg/dL; P < .01).

CONCLUSIONS

Lactation, even for a short duration, has a beneficial effect on glucose and lipid metabolism in women with gestational diabetes. Breast-feeding may offer a practical, low-cost intervention that helps reduce or delay the risk of subsequent diabetes in women with prior gestational diabetes.

Digital blunt dissection technique to assist laparoscopic gonadectomy in inguinally located/adhered gonads

Laparoscopic gonadal removal in two patients, one with XY gonadal dysgenesis and the other with complete androgen insensitivity is described. In both cases, the gonads were either located deep in the inguinal canal or adherent in that area. Digital blunt dissection using a finger passed through the lateral lower abdominal trocar incision site (12 mm) at the mid-clavicular line of the lower abdomen, combined with external palpation/elevation of the inguinal ring, allowed rapid dissection and isolation of the desired structures and vascular pedicles.

Scanning electron microscopy of vascular smooth muscle cells from spontaneously hypertensive rats

The fine structure of vascular smooth muscle cells from large mesenteric arteries of adult (28 weeks) spontaneously hypertensive rats and Wistar-Kyoto rats was studied using scanning electron microscopy (SEM). The effect of the digestion method for SEM on tissue size and smooth muscle cell size was also studied using morphometric analysis. A significant reduction in cell size (42-43%) was present after critical point drying, based on the reduction in volume to surface ratio of smooth muscle cells. However, percent change of volume density and volume to surface ratio of smooth muscle cells after digestion and after critical point drying, was similar between the hypertensives and normotensives. Most of the tissue shrinkage occurred during the digestion process to remove the connective tissue. Overall tissue shrinkage due to the digestion method involving OsO4/HCl and subsequent processing for SEM, based on changes in the thickness of the medial wall, was similar between arteries from hypertensive (34.7%) and normotensive (31.4%). After compensating for the shrinkage, vascular smooth muscle cells from hypertensive animals were found to have a wider somal region (5.94 microns) than those from the normotensives (5.46 microns), suggesting cellular hypertrophy. We conclude that a significant reduction in size of tissue and smooth muscle cells took place when arteries were processed for SEM. For comparative study of vascular changes in hypertension involving SEM, cellular shrinkage due to processing should be included in the calculations in order to provide a reasonable estimate of the alterations.

Incidence of multinucleated and polyploid aortic smooth muscle cells cultured from different age groups of spontaneously hypertensive rats

Cell size and incidence of multinucleated, polyploid cells in cultured aortic smooth muscle cells from different age groups of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) were compared. Smooth muscle cells from SHR were generally larger than those from WKY, and the percentage of multinucleated smooth muscle cells was always higher in SHR than WKY in the three age groups of rats studied (3-4, 10-12, and 28-30 weeks). In smooth muscle cells from the 3- to 4-week group, there was a positive correlation between cell diameter and the percentage of multinucleated smooth muscle cells. Microdensitometric measurements also showed that the incidence of polyploid smooth muscle cells was always higher in SHR than WKY in the three age groups. There was a positive correlation between DNA density and nuclear area measurements in all the age groups of SHR and WKY. We conclude that cultured aortic smooth muscle cells from different age groups of SHR and WKY contained heterogeneous populations of cells and that, under our culture conditions, the polyploidy of the smooth muscle cells found in vivo was maintained in the SHR and WKY.

Morphometric study of cerebral arteries from spontaneously hypertensive and stroke-prone spontaneously hypertensive rats

OBJECTIVE

The importance of sympathetic innervation for the development of structural changes in the cerebral arteries of hypertensive animals was studied.

DESIGN

Sympathetic denervation was induced with combined treatment from birth of antibody against nerve growth factor and guanethidine. Previous studies from our laboratory showed that this procedure not only caused a permanent denervation of the mesenteric arteries, but also prevented the development of hypertension in spontaneously hypertensive rats (SHR).

METHODS

Morphometric measurement of the structural changes was carried out in the basilar, superior cerebellar, posterior cerebral and middle cerebral arteries from 28-week-old SHR, stroke-prone SHR, and normotensive Wistar-Kyoto rats. The results were compared with those obtained from cerebral arteries of sympathectomized rats.

RESULTS

Total vascular wall cross-sectional area was significantly larger in the basilar and superior cerebellar arteries from hypertensive rats compared with normotensives. The change was characterized by an increase in the number of smooth muscle cell layers. There were also differences between the two hypertensive groups in some arteries. Sympathetic denervation attenuated the development of hypertension and vascular changes in some arteries. There was a positive linear correlation between blood pressure and medial cross-sectional area, and between blood pressure and the number of smooth muscle cell layers for the four arteries analysed.

CONCLUSION

Sympathetic nerves have a trophic influence upon the remodelling of some cerebral arteries during the development of genetic hypertension.

Influence of chronic nadolol treatment on blood pressure and vascular changes in spontaneously hypertensive rats

Chronic treatment of spontaneously hypertensive rats (SHR) and Kyoto-Wistar normotensive rats (WKY) with nadolol was carried out from gestation until 28 weeks of age. Nadolol treatment caused some lowering of blood pressure but did not prevent the development of hypertension or cardiac hypertrophy in the SHR, in spite of significant beta-blockade. The lumen of large mesenteric arteries from control SHR was smaller than from WKY, and nadolol treatment increased the lumen size in the SHR. An increased number of smooth muscle cell layers present in the control SHR as compared with WKY was reduced slightly by nadolol treatment. However, the changes produced by nadolol did not reach the levels of control and treated WKY. In the aorta, the incidence of polyploid smooth muscle cells was higher in the SHR than the WKY in the control group. Nadolol treatment reduced the percentage of polyploid cells in both SHR and WKY, so that the difference between these two groups of animals was eliminated in the treated groups. The tissue level of norepinephrine in the plasma, heart, mesenteric arteries, and adrenal glands in the SHR and WKY was not affected by the treatment. We suggest that the ineffectiveness of nadolol in preventing hypertension development may be due to its lack of effect in preventing primary changes in the resistance arteries, and that the development of polyploidy of smooth muscle cells may be mediated by beta-receptors.

The effect of neonatal treatment of rats with nerve growth factor on the blood pressure and structure of the mesenteric arteries

Newborn male Wistar rats were treated with nerve growth factor daily by subcutaneous injection for 2 weeks, and control rats were treated with either cytochrome c or buffered saline. Average body weight of the treated animals was lower than that of the controls during the 2 weeks of treatment, but became similar to that of the controls thereafter. Tissue levels of norepinephrine were elevated in the brain, adrenal glands, mesenteric arteries, and vas deferens of the treated animals immediately after the treatment, but became similar in the three groups 2 weeks after the termination of the treatment. Blood pressure and heart rate were measured beginning at 4 weeks of age until 28 weeks, when the rats were sacrificed and the mesenteric arteries sampled for morphometric measurements of vessel wall dimensions. Pretreatment with nerve growth factor did not affect blood pressure, nor heart rate. Structural alteration of the three types of mesenteric arteries was also absent in the treated animals. We conclude that even though neonatal treatment of normal Wistar rats with nerve growth factor for 2 weeks induced an elevation of the norepinephrine levels in several tissues at the end of the treatment period, it was not sufficient to produce hypertension and structural alterations in the blood vessels.

Adenosine metabolism in small coronary arteries of pig

Adenosine preferentially relaxes small coronary arteries over large ones, and small bovine coronary arteries are also known to have a higher density of adenosine receptors. Here we report a possible role of adenosine metabolism in this process. Subcellular fractions, from right coronary artery (lumen diameter of 2-3 mm) of pig designated as large coronary artery and its subsequent branches (lumen diameter of 0.5-1 mm) as small coronary arteries, were prepared and characterized. In comparison to the various large artery subcellular fractions, the corresponding small artery fractions were richer in 5'-nucleotidase but poorer in adenosine deaminase. Thus a cascade of events may promote adenosine relaxation in small coronary arteries: higher activity of 5'-nucleotidase leads to production of more adenosine, larger number of receptors allows greater reactivity to adenosine, and lower adenosine deaminase level promotes prolonged action of adenosine.

Comparative effects of pravastatin and lovastatin on nighttime sleep and daytime performance

Pravastatin and lovastatin, two HMG-CoA reductase inhibitors with similar cholesterol-lowering effects, differ in their lipid solubility. The hydrophilic characteristics of pravastatin may explain why the drug has not been detected in cerebrospinal fluid. On the other hand, lovastatin, a lipophilic compound, has been detected in the cerebrospinal fluid. Previous reports have suggested that lovastatin administration may be associated with insomnia, which reflects an action in the central nervous system. The effects of the two drugs on nocturnal sleep and day-time performance in young, healthy men have been assessed in randomized, double-blind, placebo-controlled studies. Computer-based performance tests were administered on two consecutive days before drug administration and at the end of a 3-week active drug or placebo treatment period. Results from both sites were combined for analysis. Neither pravastatin nor lovastatin significantly affected nocturnal sleep or daytime sleepiness in this study population, but lovastatin significantly affected daytime performance. In subjects treated with lovastatin, the results showed that two measures of performance, divided attention (p less than 0.05) and vigilance (p less than 0.01), worsened significantly from baseline as did global performance (p less than 0.01). Performance was not affected in the pravastatin and placebo groups. These results provide preliminary evidence of an adverse effect of lovastatin on daytime performance.