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Biomedical subjects

I Davies

Publications and source records attributed to I Davies.

At least 73 records · Page 4Linked to original sources
PubMed1981

The influence of age on the hypothalamo-neurohypophyseal system of the mouse: a quantitative ultrastructural analysis of the posterior pituitary.

A quantitative ultrastructural study of the posterior pituitary was undertaken. The posterior pituitary is the storage of the hormones vasopressin and oxytocin. Female C57BL/Icrfat mice which were under conditions of normal hydration were sampled at 8 and 32 months of age. There was a slight age-related decline in the volume fraction of cellular components with a corresponding increase in perivascular space. The proportion of neurosecretory endings and swellings showing autophagic activity (Dellman type II Herring bodies) increased significantly in the senescent mouse. The total pituicyte population showed a significant decrease in volume fraction, but with a significant increase in electron-dense types. Of the subcellular parameters examined, only the diameter of the neurosecretory granules showed a significant age-related decrease, the volume fraction remaining unaltered. The animals used in this study were from stocks found to be in a constant oestrus-metoestrus-like state unlikely to obscure changes in pituitary morphology. Over-all, the morphology of the posterior pituitary of the senescent female mouse under physiologically defined resting conditions indicates maintenance of the status quo.

Aging↗
PubMed1981

A comparative morphometric analysis of the component tissues of the urethra in young and old female C57BL/ICRFAt mice.

Histologic preparations of the urethras of 3 and 30-month-old virgin female C57 mice were stereologically analyzed with a light microscope with an eyepiece grid. Serial sections of entire urethras were stained and divided into ten representative regions; the component tissues of each region were analyzed. There was no significant change with age in the total muscle component in each region. The muscle, however, was divided into two types: muscle with and muscle without the infiltration of collagen fibers. The amount of muscle with collagen infiltration was significantly increased in some regions of the urethra in the 30-month-old group. There was no age-associated significant difference in the vascular or connective tissue components of the urethra. A difference in the glandular component was recorded in one region only, because of change in the ducts of the clitoral glands. We noted differences in the lumen and its epithelium that were attributable to the more open urethral lumen in the young group in certain regions.

Aging↗
PubMed1980

The influence of age on the hypothalamo-neurohypophyseal system of the mouse: a quantitative ultrastructural analysis of the supraoptic nucleus.

A quantitative study of various morphological parameters in endocrine cells of the neuroendocrine region of the laboratory mouse was carried out. The supraoptic nucleus of the hypothalamo-neurohypophyseal system synthesises the hormones vasopressin and, to a lesser extent, oxytocin, and transports them to the posterior pituitary. Female C57BL/Icrfat mice at 8 and 26 months of age, free of macroscopic pathology, were sampled when in a physiologically defined resting state. No significant differences in the volume fractions of most cell and subcellular components could be detected at the two ages studied; however, significant increases in the volume fractions of hormone-containing granules and lipofuscin (aging pigment) were demonstrated in older animals. These observations are similar to those made on rat endocrine pancreas also in the resting state. The notion that these hormone-secreting cells are "protected" to some extent from the aging process, and may have some of the qualities of "pace-maker" cells, is discussed.

Aging↗
PubMed1979

Influence of diet on chromatin organization in insect mid-gut cells, and its implications for the understanding of aging in this model system.

Female Sarcophaga bullata were fed on three different dietary combinations: liver/water; sugar/water; and sugar/liver/water. These diets resulted in different survival patterns for the insect, with the longest lifespans being expressed on the last treatment. The Feulgen-DNA values for mid-gut cell nuclei were determined using a scanning and integrating microdensitometer. The cell nuclei of the mid-gut reacted to the presence of nutrients by an increase in the extinction values for Feulgen-DNA when compared to the unfed state. There were also significant differences between the various treatments in the extent of the activation shown by the mid-gut cells. The dietary regimes resulting in the longest lifespan showed a complete and uniform activation of the mid-gut epithelium, whereas other treatments did not. These observations suggest that changes in the chromatin organization occur with diet, and that maximum Feulgen-DNA extinctions occur (i.e. chromatin uncoiled and supporting transcription) on the sugar/liver/water diet. Nuclei showing maximum extinctions do not show an age-related change between 3 and 12 days of life. However, if the nuclear activation is partial, or incomplete, then age-related reversals in chromatin condensation take place.

Aging↗
PubMed1978

Changes in the EEG as the subject learns to recall.

The EEG was monitored from posterior leads located above the left and right hemispheres, while the subject learned to recall visually presented 9-digit strings. Processing of material to be recalled led to systematic and progressive activation of the left hemisphere together with an increasing ratio in the EEG activity of the two hemispheres. As performance improved with practice, the initial activation (during the first six digits) was followed by deactivation just prior to recall. This is interpreted as reflecting a shift from active processing (rehearsal) to passive processing (echoic buffer storage). Subjects who recalled well more activated in the left hemisphere than in the right and the level of EEG activity in the left hemisphere during early trials predicted overall recall performance throughout the task. Activity in the right hemisphere was unresponsive to the presentation of material and unrelated to performance. This study shows therefore that: (i) rehearsal for short term recall is a function of left hemisphere activity, (ii) individual differences in left hemisphere activity predict performance, and finally (iii) dynamic changes in brain organisation accompany an overall improvement in performance.

Brain↗
PubMed1978

The influence of age and dementia of the neurone population of the mammillary bodies.

In a study on the influence of age and senile dementia on the mammillary bodies, the medial mammillary nucleus was examined in 15 brains from young (control), normal aged and demented females. Neurone populations, volumes and cell densities were estimated. Individual variation was high in all the groups studied. Normal ageing and dementia were accompanied by a substantial loss of volume but no significant loss of neurones, resulting in a considerable increase in cell density. No significant differences were detectable between the normal aged group and the demented group. These findings are in agreement with other investigators who have found no neuronal loss with age in discrete nuclear structures.

Adult↗
PubMed1977

The effect of diet on the ultrastructure of the mid-gut cells of Nasonia vitripennis (Walk.) (Insecta: Hymenoptera) at various ages.

The ultrastructure of mid-gut cells of female Nasonia fed on a diet of 10% sterile sucrose is described. There are extensive alterations in cell organelles, particularly the mitochondria, rough endoplasmic reticulum (R.E.R.) and lipid inclusions, when compared to similar insects fed a normal diet of dipteran pupae. A proportion of the mitochondria found in the apical cell region are enlarged in size and contain electron-dense granules. The remaining mitochondria are smaller, but also contain electron-dense granules. Cytochrome-c oxidase activity appears to be absent from the enlarged mitochondria. The R.E.R. appears reduced in many cells of the 1 day old, sugar-fed insects, however, this component fluctuates throughout the remaining life span. The lipid inclusions prominent in the 1 day old, pupae-fed insects are not present in sucrose-fed females of the same age, but lipid deposition was recorded later in the life span. There are many large residual bodies and cytolysosomes present in the old, sugar-fed insects. These changes in ultrastructure are discussed in relation to diet and longevity.

Aging↗
PubMed1977

The ultrastructure of the mid-gut cells of Nasonia vitripennis (Walker) (Hymenoptera, Pteromalidae).

The ultrastructure of the mid-gut cells of female Nasonia vitripennis is described. The mid-gut consists of a uniform, single-cell epithelium. The cells of different gut regions were analysed using morphometric techniques in order to determine any differences in the components. The structure of the cells is described in the unfed animal, and after varying periods of feeding on host body-fluids. Tissues were sampled after 12 h and 24 h of feeding on host body-fluids and after 24 h feeding/24 h starvation. The cells were found to be complex and contain an organelle component that allows solute-transport and extensive lipid synthesis. A limited cytochemical analysis involving the lysosomal marker enzyme-acid phosphatase--and the respiratory enzyme--cytochrome oxidase was carried out.

Acid Phosphatase↗
PubMed1977

The effect of age on the ultrastructure of the mid-gut cells of the hymenopteran Nasonia vitripennis (Walk.) (Hymenoptera, Pteromalidae).

The ultrastructure of the mid-gut cells of aged female Nasonia vitripennis is described. The mid-gut is a shrunken and distorted organ in the aged animal. The individual cells are highly disorganised and the organelle components are altered. The small lipid droplets formed in the apical cell region do not coalesce to form the large central lipid inclusions characteristic of the young animal. The rough endoplasmic reticulum is reduced and some of the mitochondria enlarge. The mid- and apical cell regions also contain large numbers of cytolysosomes. The basal cell region is essentially unchanged, but the channels formed by the infolded basal plasma membranes are dilated. The changes observed are discussed in relation to previous observations on other insect species.

Aging↗
PubMed1975

The structure of the rectal papilla in a parasitoid hymenopteran Nasonia vitripennis (Walker) (Hymenoptera Pteromalidae).

The ultrastructure of the rectal papillae of the parasitoid hymenopteran, Nasonia vitripennis (Walk), is described. These organs in this insect consist of four distinct cell types arranged as a closed, hollow cone. The majority of the cells are present in the raised cone, and are characterised by large numbers of mitochondria arranged in a membranous labyrinth. A series of cells form a collar around the base of the cone. Junction cells have been identified which are present at the point of insertion of the cone into the rectal epithelium. The base of the cone consists of cells with elaborately folded plasma membranes facing both the central cavity of the cone, and the haemolymph. The structure of this rectal papilla is compared with those found in other insects.

Animals↗
PubMed1975

A study of the effect of diet on the life-span of Nasonia vitripennis (Walk.) (Hymenoptera, Pteromalidae).

The effect of diet on the life-span of female Nasonia vitripennis (Walk.) has been investigated. Life-tables were constructed for these insects fed on dipteran puparia and on 10% sucrose; Further experiments were performed involving the transfer of females from the sucrose diet to puparia at different ages. The converse experiment was also carried out. From this work it was shown that the insect is capable of a greatly extended life if fed sucrose for all, or part of its life-span. However, transfer from puparia to sucrose after 15 days allows an increased survival for only a small percentage of the population. The results are discussed with regard for the age at transfer and to the reproductive physiology of the insect.

Animals↗
PubMedDate not supplied

A morphometric and cytochemical analysis of aging changes in the flight muscle of Nasonia vitripennis (Walk) (Hymenoptera, pteromalidae).

A morphometric and cytochemical analysis was carried out on the effect of age and diet on the flight muscles of Nasonia vitripennis (Walk). A significant decline in mitochondrial volume with age is revealed in pupae-fed insects, but this is not recorded in sucrose-fed insects. There is also a significant decline in the activity of cytochrome oxidase in sucrose-fed, but not in pupae-fed, insects. It is concluded that the sucrose diet caused a delay in the ultrastructural deterioration of the flight muscles.

Aging↗