Angiotensin I converting enzyme gene cosegregates with blood pressure and heart weight in F2 progeny derived from spontaneously hypertensive and normotensive Wistar-Kyoto rats

The present investigation examines the association of angiotesin I converting enzyme (ACE) genotypes with blood pressure and heart weight in an F2 population of rats derived from a cross between spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. ACE genotype of rats in the F2 population was determined using a microsatellite polymorphism. Our investigation revealed that cardiac mass was not correlated with blood pressure at 12 weeks of age within the SHR, WKY, F1 or F2 groups of rats. In male rats, ACE genotype accounted for approximately 20% of the difference in mean blood pressure between SHR and WKY rats. There was no effect in females. It was also responsible for 21%-29% of the difference in heart weight both in female and male animals. The allele derived from the SHR parent appeared recessive to the allele from WKY parent for both heart weight and blood pressure. These results suggest that a gene in the region of the ACE locus is one of the genetic factor influencing blood pressure and heart weight in SHR.

Estimation of the number of somatostatin neurons in the striatum: an in situ hybridization study using the optical fractionator method

Somatostatin-containing neurons of the striatum constitute fewer than 5% of the total neuronal population. Their involvement in the feedforward inhibition of the spiny projection neurons, the modulation of other interneurons, and the regulation of regional blood flow indicates that this small population of neurons plays an important role in the processing of information in the striatum. As a first step in developing a quantitative structural framework within which a more rigorous analysis can be made of the functional circuitry of the striatum, we used modern unbiased stereological techniques to make estimates of the total number of neurons expressing mRNA for somatostatin in the striatum of rats. The strategy developed involved the application of the optical fractionator technique to relatively thick tissue sections that were hybridized in situ with a relatively short oligonucleotide probe conjugated to a nonradioactive reporter molecule. The approach is generally applicable to other subpopulations of in situ hybridized cells in other parts of the brain and can provide a link between molecular neurobiology and stereology. The mean total number of neurons on one side of the striatum was estimated to be 21,300. An analysis of the sampling scheme indicated that counting no more than 200 neurons in a systematic sample of not more than 15 sections per individual results in an estimate with a precision that is more than sufficient for comparative and experimental studies. The issues that must be considered when analyzing in situ hybridized tissue with modern stereological methods, the interpretive caveats inherent in the resulting data, and the unique perspectives provided by data like that presented here for striatal somatostatin neurons are discussed.

Genetic variants of proteins from the renin angiotensin system are associated with pressure load cardiac hypertrophy

1. The relationship between the angiotensinogen (AGT) T174M, angiotensin converting enzyme (ACE) insertion/deletion (I/D) and the angiotensin II type 1 receptor (AT1) genetic markers and left ventricular hypertrophy was examined in normal subjects and those with aortic stenosis. 2. Subjects with aortic stenosis had higher left ventricular systolic pressure and relative wall thickness (RWT) compared with normal. However, within aortic stenosis subjects, left ventricular RWT did not correlate with left ventricular systolic pressure or with aortic valve area. 3. In subjects with aortic stenosis, left ventricular RWT was higher in those with ACE DD (P < 0.05) or AGT T174M (P < 0.06) compared with those with the ACE II or ID genotype or AGT TT174 genotype. No relationship was observed with any of the AT1 alleles. The ACE and AGT genetic markers independently predicted left ventricular RWT in aortic stenosis. No association was observed between these genotypes and left ventricular RWT in normal subjects. 4. The data suggest that the AGT T174M and ACE I/D genotypes may act together to influence the degree of hypertrophy in subjects with aortic stenosis. 5. In patients with aortic stenosis, genetic variants of proteins from the renin angiotensin system may be at least as important as left ventricular systolic pressure in determining the degree of left ventricular hypertrophy and could therefore explain the clinical variation observed in the progression to cardiac dysfunction.

Analysis of linkage of the ACE locus with measures of cardiac hypertrophy in the spontaneously hypertensive rat

1. The effects of genetic factors on cardiac myocyte diameter and other phenotypes of heart size were determined in genetically hypertensive rats. Direct blood pressure, heartweight and cardiac myocyte size were measured at 12 weeks of age in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats and F2 males derived from these rats. The genotypes of the angiotensin converting enzyme (ACE) gene on rat chromosome 10 were determined by amplification of DNA using the polymerase chain reaction in F2 animals and were correlated with measures of phenotypes using ANOVA and t-test. 2. Significant correlations between fibre diameter and myocytes and heartweight or left ventricular weight were observed in SHR, WKY and F2 males. There was no correlation of myocyte size with systolic blood pressure in F2 rats. ACE genotype was weakly correlated with heartweight, but not correlated with myocardial fibre diameter in F2 males, suggesting that this gene may primarily cause expansion of extracellular tissue rather than cardiac myocyte size. 3. Genetic factors may influence heart size through effects on the cardiac myocyte or connective tissue elements. Our results suggest that the growth of myocardial fibres and the increase in volume of interstitial elements in the hypertrophic heart are under independent genetic control.

Alpha 1-antitrypsin deficiency alleles and blood pressure in an Australian population

1. Two deficiency alleles of alpha 1-antitrypsin (AAT) called S and Z have been previously associated with lower blood pressure levels. 2. A sample of Australian hypertensive and normotensive subjects was investigated with respect to these alleles. 3. No association of blood pressure levels with these AAT alleles was found in our study sample.

Social malleability in cowbirds: new measures reveal new evidence of plasticity in the eastern subspecies (Molothrus ater ater)

The social experiences of young Molothrus ater ater cowbirds were manipulated in a 2-year study. In the 1st year, males were housed with pairs of canaries. The males were tested in 3 social contexts. Also, vocal repertoires were recorded and played back to females. In contrast to a previous study of the M. a. artemisiae subspecies, the males did not vocalize to the canaries in courtship tests (T. M. Freeberg, A. P. King, & M. J. West, 1995) but showed incompetent courtship of female cowbirds. In their 2nd year, half of the males were housed with older males and female cowbirds, and half were housed with only females. Those exposed to older males courted much more successfully than did those deprived of such experience. All males developed new repertoires, and song potencies did not correlate across years. The data reveal intraspecific variation in the ontogeny of mate recognition but intraspecific dependence on social learning to acquire courtship skills.

Memory impaired aged rats: no loss of principal hippocampal and subicular neurons

A group of 52 male, 2-year-old Ico:WIST rats were tested on the spatial reference memory version of the Morris water maze. Their performance was rated by comparisons with the performance of 2.5-month-old control rats. Unbiased stereological estimates were made of the number of neurons in the major subdivisions of the hippocampus proper and the subiculum of the 5 aged rats with the most impaired performance, the 5 aged rats with the best performance, and 5 young control rats. There were no significant differences between the mean numbers of neurons in the various subdivisions of the hippocampal region of the impaired and nonimpaired aged groups and similarly no decreases in neuron numbers in the pooled group of aged rats relative to the control rats. The results indicate that, in rats, the structural correlates of age-related deficits in spatial memory are to be found in parameters other than the number of neurons in the hippocampus proper and the subiculum.

Translational upregulation of the c-myc oncogene in Bloom's syndrome cell lines

Previous studies have shown a constitutive increase in the levels of c-myc protein in cell lines derived from patients with the cancer-prone disorder Bloom's Syndrome (BS). We report here that this overexpression results from a specific increase in the translation of the c-myc mRNA and is not the result of either a chromosomal translocation involving the c-myc locus or an amplification of this gene. We also did not detect any increase in the stability of the c-myc protein or any significant increases in the levels of c-myc mRNA expressed in BS cells compared to control cell lines. Overall, there is a 39-80% increase in the association of the c-myc mRNA with polysomes in BS cell lines. Since, in some cases, overexpression of the c-myc protein has been shown to increase levels of the translation initiation factors eIF-4E and eIF-2 alpha, which may themselves play a role in malignant conversion, we have also examined the levels of these proteins in BS cells and found them to be either comparable or lower than those in control cell lines. These data suggest that if c-myc does contribute to the cancer predisposition phenotype in BS then it does not appear to act via an eIF-4E and eIF-2 alpha mediated pathway.

Angiotensin-converting enzyme and angiotensinogen genes in patterns of left ventricular hypertrophy and in diastolic dysfunction

1. The association of different patterns of left ventricular hypertrophy and diastolic dysfunction with angiotensin converting enzyme (ACE) genotypes or angiotensinogen dinucleotide repeat alleles were studied in human subjects. 2. Three abnormal patterns of hypertrophy (remodelled, eccentric and concentric) were associated with a history of hypertension. The presence of remodelled or concentric hypertrophy was associated with diastolic dysfunction. 3. There was no difference between the frequencies of the ACE genotypes in normotensive and hypertensive subjects, in subjects with normal ventricles and those with different patterns of left ventricular hypertrophy, nor in subjects with normal and abnormal diastolic function. Similarly, there was no difference between the relative frequencies of AGT alleles in the same clinical subgroups. 4. We conclude that in this population of hospital patients, variants of the ACE and AGT genes do not contribute to the presence of different patterns of hypertrophy or to diastolic dysfunction.

[Differential neuronal loss in the hippocampus in normal aging and in patients with Alzheimer disease]

The causal relationship between the neurodegenerative changes that accompany normal ageing and those that characterize Alzheimer's disease is unclear. The high incidence of Alzheimer's disease associated with old age and the presence of its neuropathological signs in non-demented older individuals suggest that these two phenomena involve the same neurodegenerative processes and mechanisms and that Alzheimer's disease is an extension of normal ageing. On the other hand, the identification of environmental and genetic risk factors associated with Alzheimer's disease suggests the involvement of a specific disease process that is not related to normal ageing. The resolution of this fundamental issue is of importance in the design of investigative and therapeutic strategies. In this report, we describe differences in the regional patterns of neuronal loss, in the hippocampal region of the brains of Alzheimer's patients and normal ageing subjects, that indicate that Alzheimer's disease is not the manifestation of accelerated ageing, but the expression of a distinct pathological process.

Quantification of neutrophil chemotaxis: a comparison of stereological and 51Cr-labelling methods

A stereological method has been used to estimate the number of migrated polymorphonuclear leukocytes in a multipore filter assay. The estimates have been compared to those obtained with conventional 51Cr-labelling methods. The precision of the estimates in individual subjects with the two methods was similar, and in both cases the contribution to the interindividual variance made by the methods was small compared to the biological variance. However, the 51Cr-labelling method resulted in a significant reduction in the fraction of neutrophils that migrated as well as a delay in the chemotactic response. Optimal assay conditions with regard to sample size, cell concentration, incubation time and chemoattractant fMLP concentration have been established for the stereological method and the virtues of the two techniques discussed.

Differences in the pattern of hippocampal neuronal loss in normal ageing and Alzheimer's disease

The distinction between the neurodegenerative changes that accompany normal ageing and those that characterise Alzheimer's disease is not clear. The resolution of this issue has important implications for the design of therapeutic and investigative strategies. To this end we have used modern stereological techniques to compare the regional pattern of neuronal cell loss in the hippocampus related to normal ageing to that associated with Alzheimer's disease. The loss related to normal ageing was evaluated from estimates of the total number of neurons in each of the major hippocampal subdivisions of 45 normal ageing subjects who ranged in age from 13 to 101 years. The Alzheimer's disease related losses were evaluated from similar data obtained from 7 cases of Alzheimer's disease and 14 age matched controls. Qualitative differences were observed in the regional patterns of neuronal loss related to normal ageing and Alzheimer's disease. The most distinctive Alzheimer's disease related neuron loss was seen in the CA1 region of the hippocampus. In the normal ageing group there was almost no neuron loss in this region (final neuron count in the CA1 region: 4.40 x 10(6) neurons for the Alzheimer's disease group vs 14.08 x 10(6) neurons in the normal ageing group). It is concluded that the neurodegenerative processes associated with normal ageing and with Alzheimer's disease are qualitatively different and that Alzheimer's disease is not accelerated by ageing but is a distinct pathological process.

Inhibition of human vascular smooth muscle cell growth by heparin

We examined the inhibitory effect of heparin on vascular smooth muscle cell (VSMC) outgrowth from cultured coronary artery explants of primary atherosclerotic lesions and of undiseased regions from the same patients, compared with explant outgrowth from control patients (idiopathic cardiomyopathy) with no evidence of atherosclerosis. For undiseased tissue regardless of origin, heparin significantly delayed half-maximum percentage explant outgrowth time (mean difference from control treatment 2.1 [SE 0.8] days for atherosclerosis patients and 2.3 [1.0] days for control patients). For plaque tissue, heparin had no such effect. Thus the proliferative state of the cells involved in outgrowth may influence the activity of heparin.

Felodipine, metoprolol and their combination compared with placebo in isolated systolic hypertension in the elderly

This study compared with placebo the efficacy and tolerability of optimised doses of felodipine 5-20 mg daily, metoprolol 50-200 mg daily and their combination in subjects 60 years or over with isolated systolic hypertension. The study employed a randomised double-blind crossover design with allocation of treatment order within subjects by Latin squares. For each subject, after a single-blind run-in placebo phase, there were four randomised treatment phases each of six weeks duration, with a dose titration step at three weeks if necessary. Twenty-eight subjects entered the randomised phases of the study and twenty-one completed all four phases--13 male, 8 female (ages: median 71, range 59-85 years). At the end of both the felodipine and metoprolol phases systolic and diastolic pressure were reduced at 2 hours postdose compared with the placebo phase (p < 0.001), the blood pressure reduction with felodipine (-40/-20 mmHg) being greater than that with metoprolol (-15/-9 mmHg) (p < 0.01). Immediately predose (12 hours postdose) there was a persisting reduction of supine systolic blood pressure (-17 mmHg) with felodipine (p < 0.001), but there was no significant effect of metoprolol. At both measurement times the two drugs when in combination had an additive effect on blood pressure. There was a 20% increase in reported symptoms during each of the active treatment phases. Four subjects withdrew during the randomised phases because of probable drug-related adverse events and six subjects required dosage reductions during the felodipine or combination phases.(ABSTRACT TRUNCATED AT 250 WORDS)

Renin and angiotensin-converting enzyme genotypes in patients with essential hypertension and left ventricular hypertrophy

1. The associations between left ventricular hypertrophy (LVH) and specific alleles of the renin and angiotensin-converting enzyme (ACE) genes were studied in patients with essential hypertension and normal blood pressure. 2. LVH was present in 42% of those with essential hypertension (n = 72) and 17% of those with normal blood pressure (n = 44). 3. The frequency of each renin allele was the same in hypertensive and in normotensive patients. Renin allele frequencies were also the same for those with LVH and those with normal cardiac mass. When only hypertensives were considered, renin alleles were in the same proportion for the groups with and without LVH. Similarly, ACE alleles were not associated with essential hypertension nor with elevated cardiac mass. 4. We conclude that, in this population, variations in the renin or ACE genes do not contribute significantly to the development of LVH or to essential hypertension.

Mono- and combination therapy with felodipine or enalapril in elderly patients with systolic hypertension

Using a randomised double-blind crossover design with Latin square allocation of treatments in 20 subjects (7 male, 13 female-ages: 61-87 years) with systolic hypertension, we investigated the efficacy and tolerability of once daily felodipine (extended release) 5-20 mg, enalapril 5-20 mg and their combination compared with placebo in four treatment phases each of 6 weeks duration. During each phase, doses were titrated to achieve a predose clinic supine systolic blood pressure of 140 mmHg or to a predetermined maximum dose. In both the felodipine and combination phases, predose supine and standing systolic and diastolic pressures were significantly reduced compared with the placebo phase (decrease in supine pressure: -13/-5 and -18/-7, respectively). Only predose supine diastolic pressure was significantly reduced (-3 mmHg) compared to placebo in the enalapril phase. In combination the effects of the two drugs on predose blood pressure were additive. There was a 40-60% increase in reported symptoms in the felodipine and combination phases compared with the placebo and enalapril phases. Thus, in elderly subjects with systolic hypertension, felodipine effectively reduces blood pressure throughout the dose interval but with vasodilator adverse effects. In contrast, enalapril is well tolerated but is less effective in reducing blood pressure throughout the whole dose interval.

Hippocampus of the domestic pig: a stereological study of subdivisional volumes and neuron numbers

With the aim of establishing a quantitative structural basis for comparative and experimental studies, the volumes of the hippocampal subdivisions and the total number of neurons in each subdivision were estimated in domestic pig brains using modern stereological techniques. In addition to a detailed description of the stereological methods used in the analysis, comprehensive descriptions of the architectonic boundaries of the subdivisions are included. The absolute and relative volumes of the subdivisions were compared to those of a number of other species and the relationship between the number of neurons and the volume of the subdivisions was compared to that in homologous subdivisions of laboratory rats and humans. The methodology used to estimate the volumes and the total number of neurons in the individual subdivisions were evaluated with regard to the sensitivity that they can provide in experimental studies.

Regionally specific loss of neurons in the aging human hippocampus

New highly-accurate stereological methods for estimating the total numbers of neurons in brain structures have been used to test for age-related neuron loss in the human hippocampal formation. Across the age range of 13 to 85 years, there was a substantial loss of neurons in the subiculum (52%) and in the hilus of the dentate gyrus (31%); the three remaining hippocampal subdivisions showed no significant change. These losses qualify as potential morphological correlates of senescent decline in relational memory in that they can be expected to compromise the functional integrity of a region of the brain known to be intimately involved in this type of memory. The regional pattern of neuron loss is similar in certain respects to the patterns of cell loss seen during the initial phases of ischemia and epilepsy and is fundamentally different from the pattern associated with Alzheimer's disease.

New stereological methods for counting neurons

The issue of whether or not neurons die with age is of fundamental importance for understanding senescent decline in motor, sensory, and cognitive functions. Yet after over 100 years of attempts to quantify age-related neuron loss, this fundamental issue is "swirling in controversy" and the results of numerous studies addressing this issue "rife with confusion and seemingly contradictory data" (7). This is in large part due to deficiencies in the way we have thought about what constitutes evidence for neuron loss and deficiencies in the methods that have been available for counting neurons. Over the past several years, a new generation of stereological principles have been developed that have made it possible to identify and eliminate these deficiencies. Although there are now a number of review articles that briefly describe these and other new stereological principles (4,9,13,14,15,18,23), for the most part detailed descriptions of the new principles for counting neurons are found in specialized literature and are accompanied by new terms and concepts that have overwhelmed potential users and inhibited their adoption. In this essay, I describe the principles and concepts that are involved in the new stereological approach to neuron counting and discuss why the data obtained from their application represent improvements over those obtained with previously available techniques. A practical guide to the application of the principles to counting neurons or any other cell, organelle, or object present in sectioned material has been included as an appendix.

Angiotensin-converting enzyme and regulation of blood pressure in a large Australian family

1. Animal studies have implicated the angiotensin-converting enzyme (ACE) gene as an inherited risk factor contributing towards elevation of blood pressure. 2. A polymorphism of the ACE gene, involving the presence or absence of a 287 base pair (bp) segment within the gene region, was assessed for association with high blood pressure in a large, multigeneration Australian family. The association of these alleles with hypertension in unrelated individuals was also examined. 3. There was no evidence to link the ACE gene and high blood pressure in the large family. Similarly, there was no significant association between this gene and high blood pressure in the population tested. As has been reported previously, plasma levels of the enzyme were associated with genotype. These results suggest that this gene is unlikely to be a major risk factor for hypertension in this group.

Structural influences on resistance in the hindlimb vascular bed of the renal hypertensive rabbit

1. The contribution of arteriolar structural change to hindlimb vascular resistance was examined in the renal wrap hypertensive rabbit. 2. Haemodynamic variables were recorded at rest and after maximal vascular dilation using sodium nitroprusside and peripheral autonomic effector blockade. In the same animals at the end of experiments, morphometric measurements of hindlimb muscle arterioles were made. 3. Mean arterial pressure (MAP) and hindlimb vascular resistance were elevated in hypertensive animals compared with normotensive animals at rest and after maximal dilation. 4. Lumen area and lumen diameter were reduced whereas wall area and wall area to lumen area ratio were increased in hypertensive animals compared with normotensive animals. 5. In the renal wrap model of hypertension, the reduction in lumen area of arterioles, < 200 microns in diameter, is sufficient to explain the increase in haemodynamic resistance.

POLYMORPHISMS OF CANDIDATE GENES IN ESSENTIAL HYPERTENSION

1. Family and population studies have reported that blood pressure has a heritability of 30-50%, but simple genetic models do not readily explain the patterns of inheritance of hypertension. 2. Restriction fragment length polymorphisms were used to study allele frequencies of a selection of candidate genes that may be important in determining the genetic component of hypertension. These included the genes for renin, haptoglobin, neuropeptide Y and cardiac myosin beta heavy chain. 3. There was no significant association between alleles at any of these loci and the presence of hypertension in this population, suggesting that the contribution of variation at these loci to the genetic component of the variance in hypertension may be quite small.

Primary leiomyosarcoma of the heart: a rare cause of obstruction of the left ventricular outflow tract

Primary cardiac tumours are rare and frequently only diagnosed post-mortem. Recent improvements in non-invasive imaging techniques have led to an increasing number being diagnosed in life, allowing surgical resection. We report a primary leiomyosarcoma presenting with obstruction of the left ventricular outflow tract.

Unbiased stereological estimation of the total number of neurons in thesubdivisions of the rat hippocampus using the optical fractionator

A stereological method for obtaining estimates of the total number of neurons in five major subdivisions of the rat hippocampus is described. The new method, the optical fractionator, combines two recent developments in stereology: a three-dimensional probe for counting neuronal nuclei, the optical disector, and a systematic uniform sampling scheme, the fractionator. The optical disector results in unbiased estimates of neuron number, i.e., estimates that are free of assumptions about neuron size and shape, are unaffected by lost caps and overprojection, and approach the true number of neurons in an unlimited manner as the number of samples is increased. The fractionator involves sampling a known fraction of a structural component. In the case of neuron number, a zero dimensional quantity, it provides estimates that are unaffected by shrinkage before, during, and after processing of the tissue. Because the fractionator involves systematic sampling, it also results in highly efficient estimates. Typically only 100-200 neurons must be counted in an animal to obtain a precision that is compatible with experimental studies. The methodology is compared with those used in earlier works involving estimates of neuron number in the rat hippocampus and a number of new stereological methods that have particular relevance to the quantitative study of the structure of the nervous system are briefly described in an appendix.