Understanding barriers to preventive health actions for occupational noise-induced hearing loss

A theoretically based formative evaluation was conducted with coal miners in the Appalachian Mountains who were at high risk for noise-induced hearing loss (NIHL). The results of four focus groups indicate that despite high levels of knowledge, strong perceived severity of negative consequences, and strong perceived susceptibility to hearing loss, two main categories of barriers (environmental and individual) keep coal miners from using their hearing protection devices (HPD). Further analysis suggests that the environmental factors, rather than individual variables, more strongly influence decisions against protective actions. Recommendations and practical implications are offered.

Mechanisms involved in the blunted nitric oxide-cGMP pathway in hypertensive TGR(mREN2)27 rats

In hypertensive TGR(mREN2)27 rats (TGR), the subsensitivity of vascular guanylyl cyclase to nitric oxide could depend on oxidized heme, reduced heme content, or decreased expression of the enzyme. In this study, enzyme activity was stimulated by protoporphyrin-IX, which acts independently of heme, and expression was assessed by Western blot analysis. In TGR aorta, maximum stimulation of soluble guanylyl cyclase by protoporphyrin-IX was 40% lower than in Sprague-Dawley controls, and expression of the beta1-subunit of the enzyme was reduced by 50% (P<0.05, t-test). In conclusion, decreased expression of soluble guanylyl cyclase leads to a blunted response of the nitric oxide-cGMP (guanosine 3',5'-cyclic monophosphate) pathway in TGR aorta.

Reduced baroreflex sensitivity and blunted endogenous nitric oxide synthesis precede the development of hypertension in TGR(mREN2)27 rats

Transgenic TGR(mREN2)27 (TGR) rats are an animal model of fulminant hypertension characterized by an inverse circadian blood pressure profile. The present study addressed the contribution of nitric oxide (NO) synthesis and baroreflex function to hypertension and the inverse blood pressure pattern. NO synthesis was measured at four different times of day indirectly by excretion of NO metabolites (NOx: NO2- and NO3-) in the urine of 5- and 11-week-old TGR and Sprague-Dawley (SPRD) controls. Blood pressure, heart rate, and motor activity were recorded in age-matched rats of both strains using an implantable telemetry system. Beat-to-beat recording of blood pressure and pulse interval was performed hourly in 6-week-old animals over 24 h. From these data, baroreflex sensitivity (BRS) was calculated by linear regression of spontaneous fluctuations of blood pressure and corresponding changes of pulse interval. Baroreflex sensitivity was lower in pre-hypertensive TGR rats than in SPRD rats, and the reduction was restricted to the daily resting period. In both strains, NOx excretion showed circadian rhythmicity, with peak values during the activity period at night. Interestingly, excretion of NOx was reduced during the resting period in 5-week-old TGR rats prior to the development of hypertension. Impairment of NO synthesis and baroreflex function precede the development of hypertension in TGR rats. The reduction of both parameters was restricted to the resting period and, therefore, could be involved in the development of the inverse circadian blood pressure profile of TGR rats.

Time-resolved x-ray K-shell spectra from high density plasmas generated by ultrashort laser pulses

We present time-resolved x-ray spectra of C, F, Na, and Al, generated by focusing ultrashort frequency doubled Ti:sapphire laser pulses on solid plane targets. Using a high resolution x-ray streak camera in combination with a laser triggered accumulation system, we achieved a time resolution of 1.7 ps when adding the x-ray signal of many thousands of laser shots. K-shell resonance line emission with a duration in the range of 2-4 ps is observed. Ly alpha emission is generally observed to be faster than He alpha emission and the x-ray pulse duration is observed to decrease with increasing atomic number. A hydrodynamic code in combination with an atomic kinetics code is applied for simulation of time-resolved plasma emission, showing good agreement with experimental data.

Monolayers of derivatized poly(L-lysine)-grafted poly(ethylene glycol) on metal oxides as a class of biomolecular interfaces

We report on the design and characterization of a class of biomolecular interfaces based on derivatized poly(l-lysine)-grafted poly(ethylene glycol) copolymers adsorbed on negatively charged surfaces. As a model system, we synthesized biotin-derivatized poly(l-lysine)-grafted poly(ethylene glycol) copolymers, PLL-g-[(PEGm)((1-x)) (PEG-biotin)(x)], where x varies from 0 to 1. Monolayers were produced on titanium dioxide substrates and characterized by x-ray photoelectron spectroscopy. The specific biorecognition properties of these biotinylated surfaces were investigated with the use of radiolabeled streptavidin alone and within complex protein mixtures. The PLL-g-PEG-biotin monolayers specifically capture streptavidin, even from a complex protein mixture, while still preventing nonspecific adsorption of other proteins. This streptavidin layer can subsequently capture biotinylated proteins. Finally, with the use of microfluidic networks and protein arraying, we demonstrate the potential of this class of biomolecular interfaces for applications based on protein patterning.

Normalisation of blood pressure in hypertensive TGR(mREN2)27 rats by amlodipine vs. enalapril: effects on cardiac hypertrophy and signal transduction pathways

It is still a controversial issue whether different classes of antihypertensive drugs are equally effective in the regression of cardiac hypertrophy and associated complications. The present study compared the effects of prolonged treatment with the Ca2+-channel blocker amlodipine and the ACE inhibitor enalapril, respectively, in TGR(mREN2)27 rats (TGR), an animal model of renin-dependent hypertension. TGR were divided into three groups and received either amlodipine, enalapril or drinking water without addition, Sprague-Dawley rats (SPRD) served as normotensive control group. Cardiovascular parameters were monitored by radiotelemetry, and drug doses were titrated until 24-h blood pressure was reduced to approximately 140/90 mmHg in both active treatment groups. After 8 weeks of treatment left ventricular (LV) hypertrophy was completely reversed in both treatment groups despite a tenfold increase in plasma angiotensin II in amlodipine-treated TGR. In untreated TGR LV catecholamines were depleted, and beta1-adrenergic stimulation of adenylyl cyclase was blunted. Treatment of TGR with enalapril prevented both the depletion of tissue catecholamines and the desensitisation of LV beta1-adrenoceptors. Amlodipine had no effect on cardiac adrenergic signal transduction. Basal activity of LV soluble guanylyl cyclase was not different between TGR and SPRD, but its sensitivity to stimulation by nitric oxide was slightly reduced in TGR. Treatment had no effect on basal and stimulated guanylyl cyclase activity. The present study in an animal model of renin-dependent hypertension suggests that blood pressure reduction per se is sufficient for a regression of cardiac hypertrophy. However, beta-adrenergic desensitisation was prevented only in the enalapril-treated group, supporting a blood pressure-independent contribution of the renin-angiotensin system to the regulation of beta-adrenergic signal transduction.

Clinical trials update: highlights of the scientific sessions of the American Heart Association year 2000: Val HeFT, COPERNICUS, MERIT, CIBIS-II, BEST, AMIOVIRT, V-MAC, BREATHE, HEAT, MIRACL, FLORIDA, VIVA and the first human cardiac skeletal muscle myoblast transfer for heart failure

This article continues a series of reports summarising recent research developments pertinent to the topic of heart failure. This is a summary of presentations made at scientific sessions of the American Heart Association in November 2000. Clinical studies of particular interest to people caring for patients with heart failure include Val-HeFT, AMIOVIRT and V-MAC. New data from beta-blockers trials are reviewed, highlights from some important developments in post-infarction care, including MIRACL and FLORIDA, discussed and results of some early studies of gene therapy reported.

Clinical trials update: IMPROVEMENT-HF, COPERNICUS, MUSTIC, ASPECT-II, APRICOT and HEART

Important new studies relevant to the field of heart failure reported at the annual congress of the European Society of Cardiology (ESC), held in Amsterdam in August 2000, are reviewed. The IMPROVEMENT of Heart Failure survey investigated the knowledge and perceptions of over 1300 primary care physicians from 14 ESC member nations and the actual practice in over 11000 of their patients. Guidelines and clinical practice were compared. The survey suggested, in this large sample, that the quality of care was higher than previous smaller surveys have suggested but have also identified important deficiencies in knowledge and management that should be rectified. The COPERNICUS study demonstrated that carvedilol was remarkably well tolerated even in patients with very severe heart failure and that treatment was associated with a substantial reduction in mortality even among patients that would conventionally not be considered, by many, for beta-blocker therapy. The MUSTIC trial suggested that cardiac resynchronisation using biventricular pacing improved patients symptomatically whether or not the patient was in atrial fibrillation. Morbidity and mortality studies of cardiac resynchronisation are now underway. The ASPECT-II and APRICOT-II studies investigated the role of warfarin, aspirin and their combination for the long-term management of myocardial infarction. One interpretation of the data from these studies is that the combination of aspirin and warfarin is about as effective as warfarin alone but with a much higher incidence of side effects. Warfarin alone appeared superior to aspirin alone. In summary, the annual congress of the ESC provided important new information for clinical practice and, to date, was, by far, the most important cardiology congress in the world this year.

Circaannual rhythms and interactions of vitamin D metabolites, parathyroid hormone, and biochemical markers of skeletal homeostasis: a prospective study

Recent studies suggest a circannual pattern of bone turnover. To further investigate the underlying mechanisms, 41 healthy subjects (25-80 years old) living in a southwestern German city were studied prospectively over a period of 18 months. Participants were examined every 4 weeks, and blood and urine samples were obtained on each visit. The following parameters were measured: serum 25-hydroxyvitamin D3 [25(OH)D3], 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], and parathyroid hormone (PTH), as regulators, and serum total alkaline phosphatase (TAP), bone-specific alkaline phosphatase (BAP), urinary total pyridinoline (PYD), deoxypyridinoline (DPD), and the aminoterminal telopeptide of collagen type I (NTX), as biochemical markers of bone turnover. The presence of significant circannual rhythms for the various markers was tested using the Pharmfit method. In the total group, 25(OH)D3, 1,25(OH)2D3, and PTH as well as BAP, PYD, DPD, and NTX showed a significant seasonal variation. 25(OH)D3 revealed the highest amplitude (38.0%) with an acrophase in August. Levels of the biochemical markers and of PTH were highest in winter with amplitudes of up to 17.7% (DPD). Results were most pronounced in premenopausal women, in subjects <50 years of age, and in subjects who did show a significant individual rhythm in 25(OH)D3 levels. No differences were found regarding other anthropometric or life style factors. Correlation analyses revealed strongest associations between the amplitudes of a vitamin D metabolite and a biochemical marker in premenopausal women. We conclude that specific markers of bone turnover show significant circannual rhythms. These changes are related directly to variations in the hormonal regulation of skeletal homeostasis. In postmenopausal women and in men, other effects may superimpose the circannual variation of biomarkers of bone turnover.

Loss of 24 h rhythm and light-induced c-fos mRNA expression in the suprachiasmatic nucleus of the transgenic hypertensive TGR(mRen2)27 rat and effects on cardiovascular rhythms

Immediate early genes, especially c-fos, are thought to play an essential role in photic entrainment of circadian rhythms. A special characteristic of the transgenic hypertensive TGR(mRen2)27 rat strain, expressing an additional mouse renin2 gene, is the inverse blood pressure rhythm in relation to those in heart rate and activity resulting in internal desynchronisation of these physiological rhythms. Assessment of c-fos mRNA expression by microdissection and RT-PCR in the suprachiasmatic nucleus showed, that in contrast to normotensive Sprague-Dawley rats the 24 h and circadian rhythm of c-fos mRNA expression in TGR(mRen2)27 rats is abolished. Moreover, light-induced c-fos expression within the nucleus could be found in the normotensive controls, but was absent in transgenic hypertensive rats. The light pulse applied during the subjective night, at CT 14, significantly phase delayed rhythms in blood pressure, heart rate and activity in the normotensive rats by about 2 h, whereas in the transgenic hypertensive animals rhythms in blood pressure and heart rate were unaffected, only activity showed a slight phase shift. In conclusion, these data suggest that the transgene in TGR leads not only to a disturbance of the cardiovascular system but also influences the light entrainment response, which is accompanied by a suppressed c-fos mRNA expression in the suprachiasmatic nucleus.

A meta-analysis of fear appeals: implications for effective public health campaigns

The fear appeal literature is examined in a comprehensive synthesis using meta-analytical techniques. The meta-analysis suggests that strong fear appeals produce high levels of perceived severity and susceptibility, and are more persuasive than low or weak fear appeals. The results also indicate that fear appeals motivate adaptive danger control actions such as message acceptance and maladaptive fear control actions such as defensive avoidance or reactance. It appears that strong fear appeals and high-efficacy messages produce the greatest behavior change, whereas strong fear appeals with low-efficacy messages produce the greatest levels of defensive responses. Future directions and practical implications are provided.

Circadian rhythms in the renin-angiotensin system and adrenal steroids may contribute to the inverse blood pressure rhythm in hypertensive TGR(mREN-2)27 rats

The transgenic TGR(mREN-2)27 rat is not only characterized by fulminant hypertension, but also by a disturbance in circadian blood pressure regulation, resulting in inverse circadian blood pressure profiles. The reasons for these alterations are not very well understood at present. We therefore investigated the circadian rhythms in several hormones participating in blood pressure regulation. From TGR and Sprague-Dawley (SPRD) control rats synchronized to 12h light and 12h dark (LD 12:12) blood was collected at different circadian times (07, 11, 15, 19, 23, 03, and 07 again, 5 rats per strain and time). The activities of plasma renin and converting enzyme, as well as plasma concentrations of corticosterone and aldosterone, were determined by radioimmunoassay (RIA). SPRD rats showed significant circadian rhythms in all variables except plasma renin activity, with maxima occurring during the day. TGR rats showed significant circadian rhythmicity in plasma renin activity and corticosterone and daily variation in aldosterone; angiotensin-converting enzyme (ACE) activity did not reach statistical significance. In TGR rats, 24h means in plasma renin activity and aldosterone were approximately sevenfold and fourfold higher, respectively, than in SPRD rats. Peak concentrations in corticosterone around 15h were more than two times higher in TGR rats than in SPRD rats, whereas no differences were observed during the night. It is concluded that, in TGR rats, the overall increase in plasma renin activity and aldosterone may contribute to the elevated blood pressure. The comparatively high levels in corticosterone and plasma renin activity during daytime may be involved in the inverse circadian blood pressure profiles in the transgenic animals.

Contribution of the renin-angiotensin system to subsensitivity of soluble guanylyl cyclase in TGR(mREN2)27 rats

Soluble guanylyl cyclase activity and its stimulation by diethylamineNONOate was measured in aortae from hypertensive TGR(mREN2)27 rats (TGR) and Sprague-Dawley controls. Superoxide dismutase was added in vitro to evaluate the contribution of oxidative breakdown of nitric oxide (NO) by superoxide anions. Expression of soluble guanylyl cyclase was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR). Basal and stimulated soluble guanylyl cyclase activity was significantly reduced in TGR rats, addition of superoxide dismutase had no effect. Expression of soluble guanylyl cyclase subunits was not different between strains. The independent contribution of hypertension and the overactive renin-angiotensin system to soluble guanylyl cyclase subsensitivity was assessed after normalization of TGR's blood pressure by the Ca(2+)-channel blocker amlodipine or the angiotensin converting enzyme-inhibitor enalapril. Soluble guanylyl cyclase activity in TGR was slightly increased by amlodipine and almost completely restored by enalapril. In conclusion, TGR showed desensitized vascular soluble guanylyl cyclase, depending on their overactive renin-angiotensin system.

Experimental heart failure in rats: effects on cardiovascular circadian rhythms and on myocardial beta-adrenergic signaling

OBJECTIVES

Patients with chronic heart failure frequently show blunted circadian blood pressure profiles. The mechanisms involved in the loss of physiological day-night variation are still unclear, but a continuously active sympathetic nervous system could play a role. The present study evaluated long-term consequences of rat heart failure on cardiovascular circadian patterns in vivo, and on density and function of cardiac beta-adrenoceptor subtypes in vitro, as a marker of cardiac adrenergic drive.

METHODS

Heart failure in rats was induced by coronary artery ligation leading to infarct sizes of >30% of left ventricular circumference. Blood pressure and heart rate were monitored for 10 weeks after infarction using radiotelemetry. Density and function of cardiac beta(1) and beta(2)-adrenoceptors were measured by radioligand binding and adenylyl cyclase stimulation.

RESULTS

During the activity period at night blood pressure and heart rate were lower in rats with heart failure than in sham controls, leading to reduced night-day variation in the heart failure group. Depression of circadian rhythmicity in blood pressure was found over the whole study period, while that in heart rate occurred with a lag-time of several weeks. In failing left ventricles beta-adrenoceptors showed reduced high affinity agonist binding, a shift in the beta(1):beta(2) ratio towards the beta(2)-subtype, and decreased beta(1)-adrenergic stimulation of adenylyl cyclase. In right ventricles no differences were found between failing and control rats. The blunted nocturnal increase in blood pressure and heart rate as well as beta(1)-adrenergic desensitization were correlated with the severity of left ventricular dysfunction.

CONCLUSIONS

Heart failure in rats leads to disturbed circadian patterns in blood pressure and heart rate, and to desensitization of cardiac beta(1)-adrenoceptors, indicating chronic sympathetic overactivity.

Clinical trials update: OPTIME-CHF, PRAISE-2, ALL-HAT

This is a summary of reports of presentation made at the American College of Cardiology 49th Scientific Sessions, Anaheim, 12-15 March 2000. Studies with a particular interest for heart failure physicians have been reviewed. OPTIME-CHF: Outcomes of a Prospective Trial of Intravenous Milrinone for Exacerbations of Chronic Heart Failure. OPTIME-CHF was a randomised-controlled trial comparing a 48-h infusion of Milrinone or standard therapy in 951 patients recruited over a 2-year period. Patients were excluded if the investigator believed their clinical condition mandated inotropic therapy. Patients were randomised within 48 h of admission for an acute exacerbation of chronic heart failure to receive Milrinone or placebo infision for 48 h. Of the patients 43% were diabetics, 70% were receiving an angiotensin converting enzyme inhibitor, 25% were already on a beta-Blocker, and 34% had atrial fibrillation. There was no significant difference between the two groups in length of hospital stay during the index admission, subsequent readmissions and days in hospital over the following 60 days. Subjective clinical assessment scores were also no different. There was an average admission rate over the next year of one per patient in both groups. However, there was a significant increase in the incidence of sustained hypotension in the Milrinone group, which accounted for all of the increased adverse event rates for the active therapy. The 60-day mortality was 10% in both groups. This and previous trials of the oral formulation of Milrinone have now clearly demonstrated a lack of benefit with Milrinone in either during acute exacerbations of or in stable severe chronic heart failure [Packer M, Carver JR, Rodeheffer RJ et al. Effect of oral Milrinone on mortality in severe chronic heart failure. N Engl J Med 1991;325:1468-1475.]. Medium sized studies of Milrinone in patients with milder severities of heart failure also suggested an adverse impact on prognosis in the presence or absence of digoxin [DiBianco R, Shabetai R, Kostuk W, Moran J, Schlant RC, Wright R. A comparison of oral Milrinone, digoxin, and their combination in the treatment of patients with chronic heart failure. N Engl J Med 1989;320:677-683.]. Whether Milrinone even has a role for the management of a haemodyamic crisis requiring inotropic therapy must also be questioned.

Update of ELITE-II, BEST, CHAMP, and IMPRESS clinical trials in heart failure

The ELITE-II, BEST and CHAMP Trials were reported for the first time at the American Heart Association in November 1999. These trials provide valuable new information to guide clinical practice in the management of heart failure and of myocardial infarction, although none mandate a major change from current clinical practice. The IMPRESS trial of the vasopeptidase inhibitor, omapatrilat, indicated a promising new treatment for the management of heart failure.

Impact of a worker notification program: assessment of attitudinal and behavioral outcomes

BACKGROUND

Hundreds of worker notification programs are conducted each year to communicate occupational risks to workers. However, few attempts have been made to evaluate their effectiveness and few have described how communication theories are applied in developing notification messages. We developed and assessed the effectiveness of a worker notification program at a beryllium machining plant.

METHODS

We compared self-protective attitudinal and behavioral responses among workers in two plants: (1) an intervention plant that received beryllium risk notification and (2) a matched control plant that did not receive notification.

RESULTS

Workers receiving notification reported significantly stronger perceptions of threat and efficacy, more positive attitudes toward safety practices, and engaged in more protective behaviors than the workers at the control plant.

CONCLUSIONS

This study demonstrates the utility of applying communication theories in the development of notification messages and the results suggest that mass presentations may be just as effective, if not more so, than one-on-one notifications. Am. J. Ind. Med. 37:205-213, 2000. Published 2000 Wiley-Liss, Inc.

Preventing vehicle crashes with trains at grade crossings: the risk seeker challenge

A formative evaluation for a communication campaign to decrease rail-automobile accidents was conducted with a survey of 891 randomly selected residents in Michigan, USA. The formative evaluation was theoretically grounded in the extended parallel process model. The results of the study suggest that the majority of respondents engage in safe driving behaviors around railways. However, 10-20% reported extremely risky behaviors such as trying to 'beat the train' (labeled 'risk seekers'). Further analyses revealed that the risk seekers were disproportionately male with strong sensation seeking tendencies to engage in new and novel experiences and to avoid boredom. The results suggest that high sensation seeking tendencies cause one to experience greater frustration and exhibit greater judgment distortions around rail crossings, which in turn, cause one to try and beat the train. Specific recommendations are given for campaign developers and limitations to the study are addressed.

Down-regulation of the expression of endothelial NO synthase is likely to contribute to glucocorticoid-mediated hypertension

Hypertension is a side effect of systemically administered glucocorticoids, but the underlying molecular mechanism remains poorly understood. Ingestion of dexamethasone by rats telemetrically instrumented increased blood pressure progressively over 7 days. Plasma concentrations of Na(+) and K(+) and urinary Na(+) and K(+) excretion remained constant, excluding a mineralocorticoid-mediated mechanism. Plasma NO(2)(-)/NO(3)(-) (the oxidation products of NO) decreased to 40%, and the expression of endothelial NO synthase (NOS III) was found down-regulated in the aorta and several other tissues of glucocorticoid-treated rats. The vasodilator response of resistance arterioles was tested by intravital microscopy in the mouse dorsal skinfold chamber model. Dexamethasone treatment significantly attenuated the relaxation to the endothelium-dependent vasodilator acetylcholine, but not to the endothelium-independent vasodilator S-nitroso-N-acetyl-D,L-penicillamine. Incubation of human umbilical vein endothelial cells, EA.hy 926 cells, or bovine aortic endothelial cells with several glucocorticoids reduced NOS III mRNA and protein expression to 60-70% of control, an effect that was prevented by the glucocorticoid receptor antagonist mifepristone. Glucocorticoids decreased NOS III mRNA stability and reduced the activity of the human NOS III promoter (3.5 kilobases) to approximately 70% by decreasing the binding activity of the essential transcription factor GATA. The expressional down-regulation of endothelial NOS III may contribute to the hypertension caused by glucocorticoids.

Influence of circadian time, ageing, and hypertension on the urinary excretion of nitric oxide metabolites in rats

Urinary excretion of NO metabolites (NOx) was measured in male spontaneously hypertensive rats (SHR) and their normotensive Wistar-Kyoto controls (WKY) in two age groups: young (11 weeks) and old (58 weeks). Urine was collected every 6 h throughout 24 h with and without injection interperitoneally of N(G)-nitro-L-arginine-methyl-ester (L-NAME), 30 mg/kg, at 7:00 or 19:00 h. In addition, blood pressure changes by L-NAME were evaluated using radiotelemetry. In both strains of rats, injection of L-NAME abolished almost completely the urinary excretion of NOx, indicating that urinary NOx indeed reflect the endogenous rate of NO synthesis. Time-dependent variation in urinary NOx excretion was observed in WKY rats of both ages (analysis of variance, P<0.05), with higher excretion in the dark period. In SHR rats, time-dependent variation in NOx excretion was lost, and the overall amount of NOx excreted within 24 h was significantly lower in young SHR than in age-matched WKY rats. Moreover, blood pressure increases by L-NAME were significantly smaller in SHR than in WKY rats. In old rats of both strains, NOx excretion was reduced, and the difference between the strains disappeared. Our findings demonstrate that ageing is accompanied by a loss in NOx excretion, and suggest that hypertension in SHR leads to a reduction in NO synthesis already at young age.

Cardiovascular risk, renal hypertensive damage, and effects of amlodipine treatment in transgenic TGR(mREN2)27 rats

Transgenic rats (TGRs) TGR(mREN2)27 are characterized by fulminant hypertension, an inverse circadian blood pressure rhythm, and severe hypertensive target organ damage. In the present study, we evaluated cardiovascular risk factors, renal function, and urinary protein loss in transgenic rats before and after treatment with the calcium channel blocker amlodipine. Amlodipine was injected intraperitoneally in a dose of 5 mg/kg/day, either once daily at 8.00 h or twice daily in divided doses at 8.00 and 20.00 h. Untreated TGRs and Sprague-Dawley rats served as hypertensive and normotensive controls, respectively. Before and after 5 weeks of treatment, rats were placed in metabolic cages for sampling of urine. Prior to treatment, urinary excretion rates of protein, albumin, and Ca2+ were significantly higher in TGRs than in Sprague-Dawley controls. Urinary excretion of protein and albumin was reduced by 5 weeks of amlodipine treatment, whereas the excretion of Ca2+ was not affected. The reductions in renal proteinuria and albuminuria by amlodipine treatment were significantly correlated with the treatment-induced decrease in blood pressure. These findings indicate that blood pressure itself is an important contributor to albumin loss by the kidney in renin-dependent hypertension of TGRs.

Basal and stimulated hippocampal adenylate cyclase activity in the experimentally lesioned rat entorhinal cortex

Early stage development of Alzheimer-related neurofibrillary tangles occurs primarily in neurons of entorhinal cortex layers pre-alpha and pre-beta. These excitatory neurons project into the hippocampus. At this stage ('entorhinal' case), while neurofibrillary tangles are still absent from the hippocampus, a significant reduction in hippocampal adenylate cyclase activity has been detected. To test whether this reduction is a consequence of a deafferentation (and thus not a specifically disease-related alteration), we performed unilateral electrolytic lesions and sham-operations of the rat entorhinal cortex. The animals were killed 2, 12 and 55 days post lesion (dpl) and hippocampal adenylate cyclase activity was assayed. The major results were as follows: (1) both lesioned and unlesioned sides showed higher activity than a sham-operated control; (2) the adenylate cyclase activity of the lesioned side increased to a significantly lesser degree than that of the unlesioned side at 12 dpl; (3) this 'decrease' was attributed to changes in G protein-mediated activation of adenylate cyclase; (4) at no time point post lesion did the pattern of rat adenylate cyclase activity resemble that observed in Alzheimer's disease. Our data suggests that the loss of entorhinal afferents alone cannot explain the reduction in cyclase-activity seen in 'entorhinal' cases.