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Biomedical subjects

S Mackay

Publications and source records attributed to S Mackay.

16 recordsLinked to original sources
PubMed1992

An investigation of the migratory potential of mouse oocytes in vitro.

This investigation was undertaken to determine the potential of mouse oocytes for migratory activity using bisected ovaries in vitro. Bisection allowed larger medullary oocytes to be brought nearer to the surface; in this way the migratory potential of all oocytes could be studied. Observations were made following 48 h culture to allow for recovery from any initial traumatic effects resulting from bisection. Ovaries were explanted from fetuses at d 15 postcoitum and from neonatal and postnatal mice (d 1-7, 11, 12 and 14 of life) and examined by scanning and transmission electron microscopy. Oocytes were extruded from the surface and a sequence of events was inferred. Cells superficial to the oocyte sloughed off, exposing the oocytes which showed the migratory phenotype as they emerged onto the surface. Here each oocyte became rounder and was finally extruded, leaving a 'crater'. Scanning electron microscopy of the explant surface allowed counts to be made of emergent oocytes. The number of explants showing emergent oocytes was at a maximum when ovaries were removed at the end of the first week postnatum; the mean number of oocytes emerging from each also peaked at this time. Numbers of migratory oocytes declined in ovaries aged 11 d at explantation and by d 14 only 66% of explants showed oocytes at the surface. The distribution of oocytes of various sizes at the surface suggests that both small cortical oocytes and larger medullary oocytes can express the migratory phenotype. Transmission electron microscopy verified structural integrity of the emerging oocytes and revealed their relationship to underlying cells.

Animals↗
PubMed1992

Do beans and oat bran add to the effectiveness of a low-fat diet?

The effects of consuming an increased amount of soluble fibre as oat bran or beans were examined in 40 free-living hypercholesterolaemic men and women. The subjects were initially established on a low-fat background diet (29% of energy from fat) and then 55 g low-fibre oat bran, 55 g high-fibre oat bran or 80 g mixed cooked beans were added to their diet in random order for 6 week periods. Body weight and overall composition of the diet did not change. Plasma cholesterol and low-density lipoprotein cholesterol (LDL-C) were unchanged. High-density lipoprotein cholesterol (HDL-C) was significantly higher on all three intervention diets than on the lower fibre run-in diet. Supplementation of a moderately low-fat diet with palatable quantities of oat bran or beans without changing the overall fat intake does not appear to significantly lower cholesterol but may have a benefit by increasing HDL-C and reducing the ratio of LDL-C to HDL-C.

Adult↗
PubMed1992

Oocyte numbers are reduced in developing mouse ovaries cultured in testis-conditioned medium.

Reduced numbers of oocytes were present in fetal ovaries of 13 d post coitum (dpc) mice, cultured for 4 d in medium conditioned (-CM) for 2 d by 13 dpc testes, compared with ovaries maintained in standard unconditioned medium. This effect was abolished by heat-inactivation of the testis-CM. Electrophoretic analysis of conditioned media revealed differences between testis-CM and ovary-CM. Ovarian differentiation was otherwise unaffected by the testis-CM and gonadal volume was not significantly reduced. Organisation of ovigerous cords proceeded, even though the full complement of oocytes was absent, and connective tissue septa developed normally between the small cords. The reduction in oocyte numbers occurred without any inhibition of müllerian duct development. Since others, using transgenic mice, have shown, that higher concentrations of antimüllerian hormone are required to decrease oocyte numbers than are necessary for duct regression, our results suggest that an additional factor is involved in producing this modified effect.

Animals↗
PubMed1991

Control of anthocyanin biosynthesis in flowers of Antirrhinum majus.

The intensity and pattern of anthocyanin biosynthesis in Antirrhinum flowers is controlled by several genes. We have isolated six cDNA clones encoding enzymes in the pathway committed to flavonoid biosynthesis and used these to assay how the regulatory genes that modify colour pattern affect the expression of biosynthetic genes. The biosynthetic genes of the later part of the pathway appear to be co-ordinately regulated by two genes, Delila (Del), and Eluta (El), while the early steps (which also lead to flavone synthesis) are controlled differently. This division of control is not the same as control of anthocyanin biosynthesis by the regulatory genes R (S) and C1 in maize aleurone, and may result from the adaptive significance of different flavonoids in flowers and seeds, reflecting their attractiveness to insects and mammals respectively. El and del are probably involved in transcriptional control and both genes appear to be able to repress expression of some biosynthetic genes and activate expression of others.

Anthocyanins↗
PubMed1991

Morphological development and fate of the mouse mesonephros.

A study has been made of the development of mesonephric tubules in the mouse to investigate the possible transdifferentiation of tubule epithelial cell to gonadal somatic cells and/or adrenal cortical cells. Immunohistochemical localisation of laminin was carried out to study the development of basal laminae. Cells at the ventral aspect of mesonephric tubules did not show an epithelial phenotype during the period of somatic cell population of the gonadal blastema; a basal lamina appeared ventrally only after this period. Therefore, it is not necessary to postulate transdifferentiation of these cells.

Adrenal Cortex↗
PubMed1989

Mouse gonadal differentiation in vitro in the presence of fetal calf serum.

Other workers have shown that fetal calf serum (F.C.S.) inhibits the differentiation of the rat testis, and disrupts established testicular cords, in vitro. To investigate the possibility of a serum effect in the mouse, indifferent urogenital complexes and differentiated gonads were removed from sexed fetuses and cultured for 7 days in medium with or without the addition of fetal calf serum. Cultures were assessed by light and electron microscopy. Testicular and ovarian differentiation occurred in the presence of fetal calf serum. Serum did not prevent basal lamina development in testicular cords of explants cultured to the equivalent of day-17 control testes.

Animals↗
PubMed1989

Primordial germ cells and gonadal development in the golden hamster.

We present results of a light and electron microscopical study of the developing hamster gonad. Two main problems have been examined: the source of somatic cells contributed to the developing gonad and the possible presence of nuage in germ cells. Nuage has been previously reported in hamster oocytes at meiosis; its possible presence at earlier stages and in male germ cells, especially meiotic spermatocytes, was investigated. The mesonephros was found to be the major source of somatic cells to the developing gonad, though a contribution from the coelomic epithelium could not be excluded, and interstitial tissue appeared to arise from mesenchymal cells. The presence of nuage associated with nuclear pores and mitochondria in hamster oocytes from Day 15 p.c. onwards has been confirmed. New findings are the association of nuage with intercellular bridges and its presence at earlier stages, including Day 8 p.c., and in male germ cells especially at the time of the entry to meiosis.

Animals↗
PubMed1986

The differentiation of mouse gonads in vitro: a light and electron microscopical study.

Indifferent urogenital complexes were excised from mouse foetuses assessed by developmental criteria as day 10.5 or 11. After 4 or 6-7 days in culture, complexes were fixed and examined by light and electron microscopy. The effect of culturing sexed complexes in mixed sex groups was investigated. The effect of the presence or absence of foetal calf serum in the culture medium was considered. No evidence of inhibition of one sex by the other was found. Ovaries developed further in cultures than testes.

Animals↗
PubMed1975

Semi-flexible sockets for amputation below the knee.

A semi-flexible socket fitted to a series of 47 consecutive below-knee amputees is evaluated, and the problems in assessing prosthetic components and appropriate methodology are discussed. The results suggest that this type of socket deserves wider use and further evaluation in active amputees, where comfort, perspiration control or the condition of the skin is interfering with the patient's function.

Amputation, Surgical↗
PubMedDate not supplied

Different levels of food restriction have opposite effects on adipocyte cellularity and lipoprotein-lipase activity in obese rats.

The effects of several levels of chronic energy restriction on epididymal and perirenal adipose tissue cellularity and lipoprotein lipase activity, serum glucose and insulin and hepatic enzyme activities were studied in lean Fa/- and genetically obese fafa rats. The restricted rats were compared to rats fed ad libitum 24/24h or 8/24h. Restricting time of feeding was associated with increases in fat cell number in the lean, increases in perirenal adipose tissue fat cell size and serum insulin in the obese and increases in lipoprotein lipase activity in both phenotypes. Mild food restriction (-25%) had similar effects in the obese: perirenal adipose tissue fat cell size and serum insulin levels were even higher but fat cell hyperplasia was reduced. Restriction by 50% normalized lipoprotein lipase activity and markedly reduced fat cell size in the lean; in the obese, lipoprotein lipase activity and insulin levels were similar to or lower than those of the corresponding ad libitum 24/24h group but fat cell hypertrophy was not particularly affected. Restriction by 75% in the obese prevented adipocyte hyperplasia. Furthermore, lipoprotein lipase activity in adipose tissue was normalized, serum insulin and lipids being within normal limits. However, these animals had large adipocytes and were still fat.

Adipose Tissue↗