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R McClean

Publications and source records attributed to R McClean.

9 recordsLinked to original sources
PubMed2006

An investigation into the similarities and differences governing the cryopreservation success of koala (Phascolarctos cinereus: goldfuss) and common wombat (Vombatus ursinus: shaw) spermatozoa.

The aim of this study was to determine the relative cryopreservation success of koala and wombat spermatozoa and to investigate reasons for their respective post-thaw survival by examining the sperm's response to a range of osmotic media and determining the presence and distribution of F-actin. An hypothesis was proposed that F-actin may be imparting a degree of structural inflexibility to the koala sperm plasma membrane; hence, exposure of spermatozoa to cytochalasin D (5 microM), a F-actin depolymerisation agent, should result in increased plasticisation of the membrane and greater tolerance of cell volume changes that typically occur during cryopreservation. In experiment 1, koala (n = 4) and wombat (n = 4) spermatozoa packaged in 0.25 mL straws were cryopreserved using two freezing rates (fast-3 cm above liquid N2 interface; slow-6 degrees C/min in a freezing chamber) and two glycerol concentrations (8 and 14% v/v) in a tris-citrate glucose buffer with 15% (v/v) egg yolk. Wombat spermatozoa showed better (P < 0.01) post-thaw survival (% motile, % intact plasma membranes, % decondensed sperm heads) than koala spermatozoa. When exposed to media of varying osmolality, koala spermatozoa were less tolerant (% intact plasma membrane) of hyper-osmotic conditions (920 and 1410 mOsmol/kg) than wombat spermatozoa. F-actin was localised using a monoclonal antibody but only found in the wombat sperm head. When koala and wombat spermatozoa were exposed to media of varying osmolality, cytochalasin D had no beneficial effect on sperm survival (% intact plasma membranes). This study has demonstrated that wombat spermatozoa are highly tolerant of cryopreservation when compared to koala sperm but that spermatozoa from both species show greatest post-thaw survival when frozen slowly in 14% glycerol. Koala sperm are also particularly susceptible to hyper-osmotic environments but lack of detectable F-actin in the koala spermatozoan suggests that poor cryopreservation success in this species is unlikely to be associated with F-actin induced plasma membrane inflexibility.

Actins↗
PubMed2004

Sperm membrane fatty acid composition in the Eastern grey kangaroo (Macropus giganteus), koala (Phascolarctos cinereus), and common wombat (Vombatus ursinus) and its relationship to cold shock injury and cryopreservation success.

Marsupial spermatozoa tolerate cold shock well, but differ in cryopreservation tolerance. In an attempt to explain these phenomena, the fatty acid composition of the sperm membrane from caput and cauda epididymides of the Eastern grey kangaroo, koala, and common wombat was measured and membrane sterol levels were measured in cauda epididymidal spermatozoa. While species-related differences in the levels of linolenic acid (18:3, n-6) and arachidonic acid (20:4, n-6) were observed in caput epididymal spermatozoa, these differences failed to significantly alter the ratio of unsaturated/saturated membrane fatty acids. However in cauda epididymidal spermatozoa, the ratio of unsaturated/saturated membrane fatty acids in koala and kangaroo spermatozoa was approximately 7.6 and 5.2, respectively; substantially higher than any other mammalian species so far described. Koala spermatozoal membranes had a higher ratio of unsaturated/saturated membrane fatty acids than that of wombat spermatozoa (t = 3.81; df = 4; p < or = 0.02); however, there was no significant difference between wombat and kangaroo spermatozoa. The highest proportions of DHA (22:6, n-3), the predominant membrane fatty acid in cauda epididymidal spermatozoa, were found in wombat and koala spermatozoa. While species-related differences in membrane sterol levels (cholesterol and desmosterol) were observed in cauda epididymidal spermatozoa, marsupial membrane sterol levels are very low. Marsupial spermatozoal membrane analyses do not support the hypothesis that a high ratio of saturated/unsaturated membrane fatty acids and low membrane sterol levels predisposes spermatozoa to cold shock damage. Instead, cryogenic tolerance appears related to DHA levels.

Animals↗
PubMed1995

Autres pays, autres coeurs? Dietary patterns, risk factors and ischaemic heart disease in Belfast and Toulouse.

The WHO MONICA project monitors trends and determinants in cardiovascular disease to relate classical risk factor changes to trends in incidence rates. The Belfast and Toulouse MONICA centres have also collaborated in dietary studies. Both centres have validated incidence and attack rates for ischaemic heart disease using coronary event registration. These data confirm that the disease in middle-aged men is between three and four times as common in Belfast as in Toulouse. Risk factor surveys show some differences between the centres, but the overall risks assessed by two multiple logistic function scoring systems were identical. A weighed dietary survey revealed no important difference in macronutrient intake, although carbohydrate and saturated fat intake in Belfast was significantly higher. Protein, dietary cholesterol and polyunsaturated fat, particularly linoleic acid intake, was significantly higher in Toulouse, as was consumption of wine, cheese, fruit and vegetables, but not potatoes. The Northern Irish diet is typically Northern European, but although the diet in Toulouse has some features of the Mediterranean diet, it is not appreciably different from that in Belfast in terms of total fat intake. Major differences are present for several food items, and in general these differences add support to the antioxidant hypothesis.

Antioxidants↗
PubMed1992

Comparison of dietary intakes in four selected European populations.

The composition of diet and food intakes in four selected European populations were compared. Dietary data (from the World Health Organization Project on Monitoring Trends and Determinants in Cardiovascular Disease) were measured by record methods and were available for middle-aged men in Finland (n = 653), France (n = 1128), Northern Ireland (n = 356), and southern Germany (Augsburg region; n = 899). Nutritional variables--which are independent of the absolute energy intake, such as the percentage supply of energy from macronutrients and the ratio of polyunsaturated to saturated fatty acids--were on the whole similar. However, striking differences were found in food intake and in the percentage supply of fat from different foods. The results indicate that detailed knowledge of consumption figures is necessary to develop prudent and acceptable nutrition intervention programs.

Adult↗
PubMed1990

Sources of fat in the northern Irish diet.

The Belfast MONICA Project carried out the joint European Economic Community WHO MONICA Project nutrition study (EURONUT) in 1985-1986 in 401 males subjects (45-64 years) using 3-day weighed records. This resulted in 356 reliable records which were analysed. The mean energy intake was 2369 Kcals (9.9 MJ) with 38% of energy (including alcohol) derived from fat (16.5% from saturated fat, 14.0% from monounsaturated fat, 4.8% from polyunsaturated fat), 14.2% from protein, 43.2% from carbohydrate and 4.0% from alcohol. The mean total fat was 100.3 g (saturated fat 43.5 g, monounsaturated fat 36.9 g, polyunsaturated fat 12.5 g), with a P:S ratio of 0.32. The sources of the different kinds of fat and cholesterol are presented as cumulative percentages of the total. This is a useful way of identifying those foods which contribute chiefly to fat in the diet, and it should have important implications for the monitoring of progress towards meeting dietary guidelines.

Cholesterol, Dietary↗
PubMedDate not supplied

Actin localisation and the effect of cytochalasin D on the osmotic tolerance of cauda epididymidal kangaroo spermatozoa.

This study examined the hypothesis that filamentous actin associated with the complex cytoskeleton of the kangaroo sperm head and tail may be contributing to lack of plasma membrane plasticity and a consequent loss of membrane integrity during cryopreservation. In the first study, the distribution of G and F actin within Eastern Grey Kangaroo (EGK, Macropus giganteus) cauda epididymidal spermatozoa was successfully detected using DNAse-FITC and a monoclonal F-actin antibody (ab205, Abcam), respectively. G-actin staining was most intense in the acrosome but was also observed with less intensity over the nucleus and mid-piece. F-actin was located in the sperm nucleus but was not discernable in the acrosome or sperm tail. To investigate whether cytochalasin D (a known F-actin depolymerising agent) was capable of improving the osmotic tolerance of EGK cauda epididymal spermatozoa, sperm were incubated in hypo-osmotic media (61 and 104 mOsm) containing a range of cytochalasin D concentrations (0-200 microM). Cytochalasin D had no beneficial effect on plasma membrane integrity of sperm incubated in hypo-osmotic media. However, when EGK cauda epididymidal sperm were incubated in isosmotic media, there was a progressive loss of sperm motility with increasing cytochalasin D concentration. The results of this study indicated that the F-actin distribution in cauda epididymidal spermatozoa of the EGK was surprisingly different from that of the Tammar Wallaby (M. eugenii) and that cytochalasin-D does not appear to improve the tolerance of EGK cauda epididymidal sperm to osmotically induced injury.

Acrosome↗