Biomedical subjects

M J West

Publications and source records attributed to M J West.

At least 91 records · Page 5Linked to original sources

PubMed1989

Comparative quantitative study of the hippocampal region of two closely related species of wild mice: interspecific and intraspecific variations in volumes of hippocampal components.

To investigate the structural changes in the hippocampal region (subiculum, Ammon's horn, and area dentata) associated with speciation, the volumes of homologous components of this region of the forebrain were compared in the two closely related murine rodent species, Apodemus flavicollis (yellow-necked wood mice) and A. sylvaticus (long-tailed field mice), and in two geographically separated groups of A. sylvaticus. With the exception of the mossy fiber zone, no significant differences were found in the relative sizes of the components of Ammon's horn. Significant interspecific differences were found in the deep subiculum, in the intermediate (medial perforant path) and deep (commissural-associational) zones of the molecular layer of the area dentata, and in the hilus. A significant intraspecific difference was found in the combined intermediate and superficial (medial and lateral perforant path) zone of the dentate molecular layer. Differences found in the relative size of the hilus and the mossy fiber zone of Ammon's horn were complementary in that the combined volumes of these zones, which are both terminal fields of dentate granule cells, did not differ in the species. This finding provides evidence that the distribution of the terminal field of a projection system can be altered while the size of the terminal field is maintained. Within the hippocampal region, components of Ammon's horn appear well suited for quantitative comparative studies that span taxonomic units beyond the species level. In agreement with previous quantitative studies, differences in the volumes of components of Ammon's horn found in species of different orders are more likely to reflect phylogenetic trends rather than changes resulting from specializations of the particular species used. This is not true for the subiculum and the components of the area dentata. Experimentally induced changes in the connectivity of the hippocampal region are discussed in terms of the structural changes which may be responsible for the quantitative differences observed between the two species studied here.

Animals↗

PubMed1989

Optimal size of cuff bladder for indirect measurement of arterial pressure in adults.

This study tested the hypothesis that a sphygmomanometer cuff bladder long enough to encircle the arm in most adults ('obese cuff') would provide a more accurate and precise estimate of intra-arterial pressure than the usual 'standard' cuff bladder. In 53 patients undergoing diagnostic coronary angiography (35 males, 18 females, aged 36-79 years), indirect blood pressure, measured in the left arm with a random-zero sphygmomanometer, was compared with simultaneously measured femoral intra-arterial pressure. Duplicate indirect measurements were made with each of two cuffs containing bladders measuring 39 x 15 cm ('obese') and 23 x 12 cm ('standard'). The obese cuff bladder encircled 80% or more of the arm circumference in all subjects, whereas the standard cuff bladder met this requirement in only 19% of the subjects. For both systolic and diastolic pressure there was marked interindividual variability in the differences between indirect and direct measurements with both cuffs. With the obese cuff there was no systematic error in the diastolic blood pressure measurement. The standard cuff consistently overestimated diastolic pressure by 7.7 +/- 8.3 mmHg (mean +/- s.d.). For both cuffs, the difference between indirect and direct diastolic pressure increased with arm size (P less than 0.05). Both cuffs underestimated systolic blood pressure, the obese cuff by 15.5 +/- 11.7 mmHg and the standard cuff by 7.6 +/- 12.1 mmHg. These systolic blood pressure underestimates were greater at higher blood pressures (P less than 0.01) and with smaller arms (P less than 0.05). Age was not related to measurement error with either cuff.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Accuracy of the Takeda TM-2420 ambulatory blood pressure monitor.

1. The accuracy of blood pressure measurement with the Takeda TM-2420 ambulatory blood pressure monitor and the TM-2020 data recorder have been assessed by comparison with simultaneous measurements taken using auscultation and direct femoral artery measurements. 2. Systolic blood pressure was underestimated by the TM-2420 by a mean of 10 mmHg (s.d. = 6, 95% confidence interval (CI) = -13 to -7) over the range of pressures measured by auscultation. It was underestimated by 23 mmHg (s.d. = 12, 95% CI = -28 to -18) compared with direct femoral artery measurements. 3. Diastolic pressure measurements were similar to those obtained by auscultation. When compared with direct femoral artery recordings, diastolic pressure was overestimated by about 5 mmHg (s.d. = 4, 95% CI = 3.4-6.6), which is consistent with indirect readings, taken with a 'standard' cuff (inflatable bladder 23 cm X 12 cm). 4. The TM-2420/2020 is thus suitable for ambulatory measurements of blood pressure when diastolic pressure is the criterion of interest.

Angiocardiography↗

PubMed1989

Proximate regulation by mothers: a demonstration of how differing styles affect young children's behavior.

An earlier observational study of mothers and toddlers in the supermarket revealed differential success of 2 styles of maternal behavior. A proactive style of preempting opportunities for misbehavior, in contrast to a reactive style of responding only after misbehavior occurred, was correlated with a lower incidence of undesirable child acts. Here, the 2 styles were studied in the laboratory to explore their function further. In an analog of the supermarket situation, mothers behaved proactively and reactively in trials in which the task was to prevent their 2- or 3-year-old children from playing with desirable toys. Children responded to proactive behavior by engaging in acceptable behaviors longer and by violating fewer rules. The 2-year-old children were less able to comply with the rules. The data illustrate the role parents play in promoting and supporting the development of compliance and self-regulation in children.

Attention↗

PubMed1989

Dose-dependent bimodal effect of low-level lead exposure on the developing hippocampal region of the rat: a volumetric study.

The hippocampal region is known to accumulate experimentally applied and environmentally occurring lead and to be implicated in lead-induced behavioral deficits. With the intention of investigating morphological changes resulting from the lower range of exposures that produce behavioral alterations in laboratory animals, the volumes of hippocampal components were determined in groups of rats exposed from postnatal days 0-21 to different concentrations of lead through the maternal water supply (initially 109 ppm, subsequently replicated with 109, 218, 436 and 872 ppm). Significant effects were found in the mossy fiber zone, the granule cell layer and the commissural-associational zone of the dentate molecular layer of the group exposed to 109 ppm lead and the pyramidal cell layer of regio inferior (CA3) of Ammon's horn in the group exposed to 218 ppm lead. These results provide evidence that lead primarily affects newly formed neuronal components. In contrast to the results of previous studies, which used larger exposures to lead, the components affected in the group exposed to 109 ppm increased in volume. In addition, no significant effects were observed in the groups exposed to 436 and 872 ppm. Based on these findings and additional evidence from the literature, it is concluded that lead has a dose dependent bimodal influence on developing hippocampal components. While the volumetric changes related to lead were of the same magnitude and direction in the initial and replication studies, the absolute volumes of the affected hippocampal components were different. The differences in "baseline" values in the two studies are more likely related to differences in prenatal conditions.

Animals↗

PubMed1988

Female visual displays affect the development of male song in the cowbird.

The role of social stimulation in avian vocal learning is well documented. The separate contribution of social, as opposed to vocal, stimulation has been difficult to address, however, because in almost all cases both tutor and pupil sing. The opportunity to isolate such effects arose in cowbirds (Molothrus ater ater) after discovering that males housed with non-singing female cowbirds made vocal changes which related directly to the female preferences for native song. Here we report how females communicate with males about songs. We describe a visual display by females, a wing stroke, that is elicited by specific vocalizations. The songs that trigger wing strokes are in turn highly effective releasers of copulatory postures, and thus this previously unnoticed female display has biological significance. The data not only provide the first evidence of the tutorial role of male-female interactions during song ontogeny, they also clearly implicate visual stimulation in song learning, a process that has until now been assumed to be affected only by auditory information.

Animals↗

PubMed1988

Estimating the number of granule cells in the dentate gyrus with the disector.

A practical example is given of how a newly developed stereological estimator of particle number, the disector, can be used to make estimates of neuron number in the dentate gyrus of rats. The estimates are free of biases related to lost caps, overprojection and assumptions about size, shape and orientation of the objects that are counted. The disector principle and the practical considerations relating to histological preparations and sampling are presented.

Animals↗

PubMed1988

Vocalizations of juvenile cowbirds (Molothrus ater ater) evoke copulatory responses from females.

The functional attributes of the vocalizations produced by young male cowbirds during their first fall and winter, termed "vocal precursors," were tested by playing the sounds back to female cowbirds. Five classes of vocalizations were tested: subsong, plastic, formatted, and stereotyped song, and songs of nonconspecifics. Females responded selectively to the four classes of cowbird vocalizations. Stereotyped songs evoked the most responding but the key eliciting element was the inclusion of note clusters, which first occurred in plastic song. The data suggest that juvenile cowbirds possess vocalizations capable of evoking biologically relevant responses from companions early in development.

Animals↗

PubMed1988

Limitations of the technique of pressure microinjection of excitatory amino acids for evoking responses from localized regions of the CNS.

The aim of this study, performed on anaesthetized cats and rabbits, was to test the assumption that pressure microinjections of excitatory amino acids cause long-lasting excitation of neurones located close to the injection site. Unitary action potentials or antidromic field potentials were recorded from respiratory or 'reticular' neurones in the medulla oblongata and from phrenic motoneurones at different distances from the injection site. Injection of 10-150 nl (5-150 nmol) of L-glutamate or DL-homocysteic acid into these areas resulted in complex and widespread neuronal events. Generally, more distant neurones (500-1300 microns) were excited for variable periods of time (3-15 min), while neurones in the vicinity of the injection site (0-500 microns) showed, after a brief period of excitation time, a long-lasting (up to 30 min) decrease in excitability or silencing of discharge, probably due to a depolarizing block and disturbances in the ionic composition of the extracellular space. These findings show that interpretation of physiological responses following such injections should not be based on an assumption of local neuronal excitation. Some recommendations regarding the use of this technique are made.

Action Potentials↗

PubMed1988

Central serotonergic mechanisms in hypertension.

Serotonin-containing neurons in the central nervous system are grouped into a number of discrete and distinctive collections with cell bodies in the brainstem and projections passing to many regions of the brain and spinal cord. Evidence is presented that activation of one projection of serotonin-containing neurons from the midbrain to the hypothalamus elevates arterial pressure. Evidence is also presented that activation of a projection descending from the lateral B3 serotonin cell group to the spinal cord elicits a pressor response that is accompanied by increased release of serotonin in the spinal cord and is independent of the C1 adrenaline-containing neurons that lie close by. In contradistinction, experiments are described demonstrating that activation of the midline group of B3 serotonin cells in the raphe nucleus causes a fall in arterial pressure, consistent with the view that different groups of serotonin neurons in the brain and spinal cord participate in the control of blood pressure in diverse ways and can have different effects on blood pressure. Finally, experiments are described showing that the hypotensive action of methyldopa is mediated in part through central serotonin nerves.

5,7-Dihydroxytryptamine↗

PubMed1988

Automated non-invasive measurement of cardiac output: comparison of electrical bioimpedance and carbon dioxide rebreathing techniques.

Two commercial automated, non-invasive systems for estimation of cardiac output were evaluated. Values of cardiac output obtained by electrical bioimpedance cardiography (BoMed NCCOM3 machine) were compared with values derived from an indirect Fick technique that uses carbon dioxide rebreathing (Gould 9000 IV system) during 103 simultaneous measurements made at rest in 19 randomly selected subjects and on exercise in 11 subjects. Cardiac output values obtained with impedance cardiography were significantly correlated with those measured by the indirect Fick method, although there was a wide scatter with over 73% of the readings lying outside the limits defined by the line of identity +/- 20%. This correlation was greatly reduced when stroke volume index was used instead of cardiac output. Indirect Fick results were linearly related to oxygen uptake both at rest and on exercise, while impedance cardiography results did not correlate with oxygen uptake. Impedance cardiography gave consistently lower results for cardiac output than indirect Fick at all levels of exercise. Both machines were easy to use and produced acceptable mean (SE) coefficients of variation (BoMed NCCOM3 7.7 (1.0)%, Gould 9000 IV 10.6 (1.4)%). Further validation is required before either of these machines can be recommended as an alternative to invasive monitoring in clinical practice.

Adolescent↗

PubMed1988

Enalapril and atenolol in essential hypertension: attenuation of hypotensive effects in combination.

In 16 patients with essential hypertension the effects of enalapril 20 mg once daily were compared with those of atenolol 50 mg once daily, with the two drugs in combination and with placebo using a double-blind cross-over design with allocation of treatment order by randomised Latin squares. For each patient there were four treatment phases, each of four weeks duration, which together comprised a 2 x 2 factorial experiment. All blood pressure parameters were reduced in the three active treatment phases compared to placebo (p less than 0.001). Supine blood pressures (group means) were 171/97 (placebo), 147/85 (enalapril), 154/84 (atenolol) and 144/78 (enalapril plus atenolol) (S.E.M. +/- 2/+/- 1-ANOVA), and standing blood pressures were 170/105 (placebo), 146/92 (enalapril), 154/92 (atenolol) and 147/86 (enalapril plus atenolol) (S.E.M. +/- 3/+/- 1). In the combination phase there was an additional hypotensive response but the potential fully additive effects of the two agents were attenuated by 30-50%. The mechanism of the attenuated hypotensive effect of the combined agents has not been determined. Plasma atrial natriuretic peptide (ANP) concentration was doubled in the presence of atenolol (P less than 0.01) suggesting that ANP may contribute to the hypotensive effect of the beta-blocker.

Aldosterone↗

PubMed1987

Volumes of the components of the hippocampus in the aging F344 rat.

Much of the recent data on cells, synapses, and other structures in the dentate gyrus and hippocampus as a function of age are packing density or volume fraction data. In order to estimate total numbers, volumes, or surface areas of cells, synapses, vessels, etc., as a function of age, the total volumes of the subregions of the dentate gyrus and hippocampus must be known. The volumes of these subregions, visualized with the Timm stain, have been determined in 24 F344 rats from 4 to 37 months of age. Volumes of the various structures showed age-related increases which were statistically significant for the perforant path zone of the dentate gyrus molecular layer, as well as the total molecular layer, the hilus, and regio inferior and total mossy fiber systems. If the 4-month age group is eliminated from consideration, only the ratio of the volume of the mossy fiber zones to the volume of the perforant path zones of the dentate molecular layer increases significantly with age. Our general finding of lack of volumetric reorganization of the subdivisions of the hippocampal region between 12 and 37 months suggests that studies of the packing densities of structures in most of these zones may be considered comparable across ages, assuming comparability of sampling regions.

Aging↗

PubMed1987

Asymmetry in the hippocampal region specific for one of two closely related species of wild mice.

The volumes of the components of the left and right hippocampal regions were compared in male, adult specimens of the two closely related species of wild mice, Apodemus flavicollis (yellow-necked wood mice) and Apodemus sylvaticus (long-tailed wood mice). In one of the species, Apodemus flavicollis, the component containing the deep layers of the subiculum was found to be significantly larger in the hippocampal region of the left side than it was in that of the right side. No other significant asymmetries were found in the hippocampal components of the two species. These findings indicate that significant asymmetries in localized brain regions can arise during a single speciation event.

Animals↗

PubMed1987

Inhibition of vasodepressor neurons in the caudal ventrolateral medulla of the rabbit increases both arterial pressure and the release of neuropeptide Y-like immunoreactivity from the spinal cord.

The role of bulbospinal neuropeptide Y (NPY)-containing neurons of the rostral ventrolateral medulla in the rabbit in mediating the increase in blood pressure that occurs during inhibition of cells in the caudal ventrolateral medulla was investigated in urethane-anaesthetized rabbits. In the present experiments bilateral injections of the GABA agonist, muscimol, into the caudal ventrolateral medulla elicited a slowly-developing rise in arterial pressure that was maximal 15 min after the injection. Accompanying this increase in arterial pressure was an increase in the release of NPY-like immunoreactivity (NPY-LI) into the spinal subarachnoid space. This pattern of response is similar to that seen after direct chemical stimulation of the NPY-containing cells of the rostral ventrolateral medulla. Taken together, these findings suggest that tonically active neurons in the caudal ventrolateral medulla exert their effects by inhibiting sympathoexcitatory NPY-containing neurons whose cell bodies are situated in the rostral ventrolateral medulla.

Animals↗

PubMed1987

Different outcomes of synergy between song production and song perception in the same subspecies (Molothrus ater ater).

Here we report data requiring a reinterpretation of published results on the female cowbird's (Molothrus ater ater) ability to identify male song (King, A. P., and West, M. J. (1983). Female perception of cowbird song: A closed developmental program. Dev. Psychobiol., 16:335-342). Previously we stated that naive females, given extensive social experience with males from a distant cowbird subspecies, showed the same degree of preference for native song as did naive females reared with local males: extensive experience with another subspecies produced no evidence of postnatal modifiability. The procedure used to probe for modifiability did not, however, expose the different groups of females to comparable levels of stimulation because the females differentially affected the behavior of their male companions. We must therefore amend our conclusion about the modifiability of females. In addition, we report data on populational differences within the M.a. ater subspecies in the female's ability to influence heterosubspecific males, but data that are consistent with the more general pattern of synergistic effects during song development.

Animals↗

PubMed1987

Settling nature and nurture into an ontogenetic niche.

All organisms inherit parents' genes, but many also inherit parents, peers, and the places they inhabit as well. We suggest the term ontogenetic niche to signify the ecological and social legacies that accompany genes. A formal name is needed to give the idea of the inherited environment equal status with its conceptual cognates; nature and nurture. We argue here that increased recognition of the inherited environment facilitates unification efforts within the developmental sciences by emphasizing the affinity, rather than opposability, of ontogenetic processes.

Animals↗

PubMed1987

A quantitative evaluation of the neurotoxic effect of silver on the volumes of the components of the developing rat hippocampus.

The volumes of the components of the hippocampus of rats subjected to subcutaneous injections of silver during the first 4 postnatal weeks were compared to those of littermate controls. Of the 14 components measured, only the pyramidal cell layer was found to be significantly smaller in the treated animals. These findings indicate that the perikaria of the pyramidal cells are either the first elements in the developing hippocampus to show signs of silver toxicity or that they are the selective sites of silver neurotoxicity. The volumetric approach is shown to be a sensitive means by which small localized neurotoxic effects can be detected.

Animals↗