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Biomedical subjects

M G Wade

Publications and source records attributed to M G Wade.

At least 19 recordsLinked to original sources
PubMed2000

The effect of aging on adaptive eye-hand coordination.

Perceptual-motor adaptability of older adults (65 and older) was assessed. Participants in two groups (younger, 20-36 years, and older, 67-87 years) pointed 100 times at a straight-ahead visual target while looking through laterally displacing prisms, with the hand visible early in the pointing movement. Aftereffect tests were administered after adaptation. Each group was then split into decay and readaptation subgroups in which respective treatments were given twice. After each treatment, aftereffect tests were readministered. Eye-hand total shift was significantly smaller for older participants, proprioceptive shift was not statistically smaller for older participants, and visual shift did not appear. Readaptation produced greater reduction in aftereffects than did decay; this effect was the same for both groups. The main conclusion is that perceptual-motor adaptability declines with advancing age.

Adult↗
PubMed1999

Reproductive effects of tris(4-chlorophenyl)methanol in the rat.

Tris(4-chlorophenyl)methanol (TCPM) is a global contaminant of unknown origin that is structurally related to the endocrine modulating pesticides 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and Dicofol. Therefore, the potential reproductive toxic effects of TCPM were investigated in sexually mature male Sprague Dawley rats (n = 20) treated with 1.0, 10.0 or 100 ppm of TCPM mixed in the diet for 28 days. The calculated TCPM intake was 0.0, 0.1, 1.2 and 12.4 mg/kg/day, respectively. Serum concentrations of follicle stimulating hormone (FSH) in terminal blood samples were significantly (P < 0.02) elevated in the highest dose group compared to the controls. In contrast, dietary exposure to TCPM had no effect on circulating levels of luteinizing hormone (LH), testosterone (T) and the T/LH ratio. Incubation of MCF-7 cells with increasing concentrations of TCPM failed to either induce proliferation or to block the proliferative effect induced by estradiol indicating that TCPM is neither estrogenic or anti-estrogenic. Relative binding affinity studies using androgen receptors from the prostate revealed that TCPM has a binding affinity comparable to 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE), the principle metabolite of DDT. In addition, the calculated Ki (0.62 microM) for TCPM is lower than the reported Ki's for the antiandrogenic pesticides p,p'-DDE and vinclozolin. Although TCPM binds with the androgen receptor in vitro, the absence of both an effect on serum T levels and morphological changes in the testis suggests that the mechanism of action for elevated FSH levels seen in vivo may not involve an antiandrogenic effect of TCPM at the dose level used in this study. The no adverse effect level for reproductive effects of TCPM is 10 ppm which is equivalent to a calculated intake of 1.2 mg/kg/day.

Animals↗
PubMed1997

Effects of culturing bovine oocytes either singly or in groups on development to blastocysts.

In vitro maturation, fertilization and culture (IVM/IVF/IVC) of cattle oocytes from individual cows requires adapting existing culture protocols so that small numbers of oocytes can be cultured. The culture of single oocytes is desirable for correlating the relationship between follicular properties with oocyte developmental competence or for facilitating ovum pick-up procedures. In Experiment 1 we compared group and single culture under cell-free conditions on embryo development; significantly higher (P<0.001) rates of cleavage (66.4 vs 47.6%) and blastocyst formation (7.5 vs 0.5%) were observed in the group cultured oocytes. In Experiment 2 we compared group and single oocyte co-culture with granulosa cells. Although there was no effect of oocyte number on the percentage cleaving (73.1 vs 66.6%), there were significantly higher blastocyst yields (37.4 vs 10.1%) and blastocyst cell numbers (91.6 vs 66.2) in group-cultured oocytes. In Experiment 3 we examined the effect of group size (1, 5, 10, 20 and 40 oocytes) in a co-culture system using granulosa cell monolayers. The results show a difference in cleavage rates between the single cultured oocytes (66.8%) and each group of cultured oocytes, with the highest cleavage rate (81.5%) obtained in the 20-oocyte group. The blastocyst yield from both cleaved and total oocytes showed that group culture of 20 or 40 oocytes resulted in the highest number of blastocysts (32.5%), with smaller group sizes yielding significantly (P<0.05) fewer blastocysts. In Experiment 4 we examined the effects of co-culture on the development of single vs group-cultured oocytes. The results showed no significant difference (P>0.05) in the cleavage rate between single and group culture systems. No blastocysts were formed with single oocytes cultured without monolayers, while the blastocyst formation rate for those co-cultured with granulosa cells was 12.4%. Blastocyst formation was significantly higher (P < 0.006) in group co-culture on monolayers (24.2 vs 8.5%). These data indicate that oocytes cultured in groups are developmentally more competent and suggest that for optimum development oocytes need some undefined paracrine activity that is absent from the culture medium in addition to coculture with granulosa cells, which enhances development to the blastocyst stage of both group and singly cultured oocytes.

Journal Article↗
PubMed1997

Influence of ovine oviducal amino acid concentrations and an ovine oestrus-associated glycoprotein on development and viability of bovine embryos.

This study examined the effects of incorporating an ovine oviducal oestrus-associated glycoprotein (oEGP) and amino acids, at the concentrations present in the ovine oviduct around the time of oestrus, on in vitro production and subsequent viability of bovine embryos. The first experiment compared the influence of ovine oviducal concentrations of amino acids with MEM and BME amino acids. There was no treatment effect on cleavage rate (74.9% vs. 75.5%), but there was a higher (P < 0.05) blastocyst yield (30.4 vs. 25.2) and a shorter time (P < 0.05) to blastocyst formation (7.16 +/- 0.64 vs. 7.27 +/- 0.56 days) following use of oviducal concentrations of amino acids. Experiment 2 examined the influence of oEGP in combination with each of the amino acid treatments. oEGP had no effect on cleavage or blastocyst yield within amino acid treatments. Day of blastocyst formation significantly influenced nuclei numbers (P < 0.001) with higher numbers being obtained on day 7 than on either day 6 or day 8. There was also a significant (P < 0.01) interaction between day of blastocyst formation and amino acid treatment on blastocyst nuclei numbers. The third experiment studied the effects of the amino acid treatments on embryo viability. There was no effect of amino acid treatment of embryos on pregnancy rates (34.5 vs. 44.4%) following transfer of days 6 and 7 blastocysts to synchronized recipients. oEGP did not influence any of the parameters of bovine embryo development that were measured, suggesting that effects of this protein observed on ovine embryos are species specific. It is concluded that ovine oviducal amino acid concentrations are beneficial to blastocyst development in vitro but do not have any further beneficial effect following transfer of blastocysts to recipients.

Amino Acids↗
PubMed1997

The role of vision and spatial orientation in the maintenance of posture.

This article reviews and analyzes the role of vision and spatial orientation in maintaining posture and balance. The key issues that relate to the development of postural control across the life span are discussed. Use of vision as a critical source of information that specifies spatial orientation in the environment is considered. We argue that the visual system functions as part of the perception-action cycle as promoted in ecological psychology by James Gibson. We compare and contrast theory and evidence of both standard and ecological accounts of how the visual system perceives the information and the findings relative to the role of the retinal vision in processing and acting on information related to motion. Changes in the ambient optical array (optical flow) as a non-force field are compared with gravity-based perturbations relative to the possible influence of the non-force field to changes in the motor system. Finally, a summary of some of our own work is presented, with comments about implications for further research and possible applications to clinical practice.

Humans↗
PubMed1995

Optical flow, spatial orientation, and the control of posture in the elderly.

Stabliographic techniques were used to better understand the role of the visual system in the perceptual motor activity of older people as it relates to the maintenance of postural control. The central research question was to determine the sensitivity of the subject's visual system to changes in three standard conditions of optical flow generated by an experimental moving room. Any movement that was present as a function of this optical flow field was recorded on a force platform and expressed in movement of a computed center-of-pressure variable. Movement of the center of pressure was recorded in a baseline condition and in the experimental conditions, and the data were analyzed with respect to differences in the three conditions of optical flow and between both younger and older subjects. The older subject group exhibited less stability than the younger subjects in response to the baseline conditions; and, after adjusting for baseline movement, the center-of-pressure motions of younger and older subjects, in response to the experimental conditions, were compared. No reliable differences were present between younger and older subjects for the radial optical flow condition; in the lamellar flow condition, older subjects moved significantly more than younger subjects; and, in the combined condition (global), the movement of the older subjects was significantly greater than that of the younger subjects for all motion variables recorded. The results are interpreted and discussed both in terms of their implication for falling in the elderly and in the context of an ecological interpretation of the role of vision in maintaining postural stability while both stationary and in motion.

Accidental Falls↗
PubMed1995

Influence of the muscarinic agonist carbachol on intracellular Ca2+ in chicken granulosa cells: I. Dependence on follicular maturation.

The present study addressed the influence of follicular development on carbamylcholine chloride (Cch)-induced Ca2+ transients and inositol 1,4,5-trisphosphate (IP3) production in granulosa cells isolated from the first (F1), third (F3), and fifth and sixth (F5,6) largest follicles. Intracellular free calcium, [Ca2+]i, was measured in fura-2-loaded cells about 20-36 h after their isolation. The percentage of cells responding to a maximal stimulatory concentration of Cch (0.2 mM) was higher in the F1 (89%) granulosa cells than in cells from the F3 (68%) and the F5,6 (72%) follicles. Most of the Ca2+ transients that were elicited in F1 granulosa cells were characterized by large (696 +/- 119 nM), fast (260 +/- 55 nM/sec) increases in [Ca2]i followed by a slow, uneven decrease in [Ca2+]i to the resting concentration. In contrast, Cch-induced changes in [Ca2+]i in F3 and F5,6 granulosa cells were generally both smaller (154 +/- 37 nM and 165 +/- 37 nM, respectively) and slower (36 +/- 25 nM/sec and 46 +/- 16 nM/sec, respectively) than those observed in cells from the largest follicle. Removal of external Ca2+ did not alter the large, fast increases in [Ca2+]i; however, it nearly blocked the slow responses observed in F3 and F5,6 cells. IP, production was elevated in 3H-myo-inositol-loaded F1 granulosa cells after 1 min of Cch (0.2 mM) treatment, whereas inositol bisphosphate (IP2) production and inositol monophosphate (IP) production were elevated only after longer incubations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Visual regulation of gait in bipedal locomotion: revisiting Lee, Lishman, and Thomson (1982).

This study expanded the database regarding the visual regulation of gait in the long jump approach (LJA) in the direction of novice long jumpers. It showed that the pattern of visual influence on gait adjustments was similar for novices and experts. This was taken to indicate that visual regulation of gait in the LJA is not a specially trained skill as much as it is a natural means of controlling gait. The study also showed that novices' step lengths were regulated principally by modifying vertical impulse. This finding replicated that of an influential study by D. N. Lee, J. R. Lishman, and J. A. Thomson (1982). Results are discussed with respect to the prevailing ecological notion that the optical variable tau provides principal informational support for regulation of gait in the LJA.

Adolescent↗
PubMed1994

Release and steroidogenic actions of polyunsaturated fatty acids in the goldfish testis.

The aim of the present study was to examine the role of several polyunsaturated fatty acids (PUFA) in the control of steroidogenesis in the goldfish testis. The release of fatty acids from testis tissue in response to the protein kinase C activator phorbol-12-myristate-13-acetate (PMA) and calcium ionophore A23187 was studied. After a 2-h incubation, goldfish testis tissue released detectable amounts of several fatty acids, particularly docosahexaenoic acid (DHA). Treatment with PMA (100 nM) and A23187 (1 microM) increased the release of arachidonic acid (AA) and, to a lesser extent, of eicosapentaenoic acid (EPA). Further experiments showed that AA (100 and 400 microM) and, to a lesser extent, eicosatrienoic acid (ETA; 400 microM)--but not EPA or DHA (both 400 microM)--stimulated testicular testosterone (T) production via an indomethacin (INDO; 40 microM)--sensitive pathway, suggesting that these effects may be mediated through conversion to prostaglandins (PG). E-series PGs formed directly from ETA, AA, or EPA (PGE1, PGE2, or PGE3, respectively) all stimulate T production, with relative potencies of PGE2 > PGE1 > PGE3. The inability to detect ETA release from testis incubates and the limited effect of EPA on steroid production suggest that PGE2 represents the predominant E-series PG formed under physiological conditions in the goldfish testis. The steroidogenic action of AA was blocked by treatment with EPA or DHA, and this effect is due, partly, to inhibition of PGE2 formation from AA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Arachidonic acid and prostaglandin E2 stimulate testosterone production by goldfish testis in vitro.

Studies were conducted to determine the effects of arachidonic acid (AA) and its metabolites on testosterone (T) production by goldfish testis pieces. AA (25-400 microM) stimulated a dose-related increase in T production and this effect was potentiated by cyclic nucleotide phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. T production in response to AA was elevated after 2 hr and continued to increase up to 24 hr. The stimulatory effect of AA was strongly inhibited by indomethacin and ibuprofen which block cyclooxygenase activity, whereas nordihydroguaiaretic acid, a lipoxygenase inhibitor, had no effect. Eicosatetraynoic acid, which inhibits both cyclooxygenase and lipoxygenase activity, also attenuated AA-stimulated T production. Together, these results suggest that AA effects on T production are mediated by metabolite(s) of the cyclooxygenase pathway. Several cyclooxygenase products stimulate T production; their relative potency was PGE2 = PGE1 >> PGI2 > PGF2 alpha while PGD2 had no effect. Lipoxygenase products of AA metabolism, including 5-, 11-, 12- and 15-hydroxyeicosatetraenoic acid had no effect on T production. AA, PGE2, and hCG increased cAMP production, suggesting that these compounds mediate T production through the actions of the same signaling molecule. In support of this contention, PGE2 had no additive effect on T production stimulated by a maximal dose of hCG. These data suggest that a cyclooxygenase metabolite of AA, likely PGE2, is involved in the control of steroidogenesis in the goldfish testis.

Animals↗
PubMed1991

The control of testicular androgen production in the goldfish: effects of activators of different intracellular signalling pathways.

The putative roles of different signal transduction pathways in the regulation of testicular androgen production in goldfish were investigated. In addition to the role of the gonadotropin-adenylate cyclase pathway, which was studied using human chorionic gonadotropin and forskolin, we determined the effects of changes in intracellular calcium content and protein kinase C activation on androgen production using calcium ionophore A23187 and phorbol 12-myristate 13-acetate (PMA), respectively. Testis fragments incubated in vitro respond to hCG in a time- and dose-dependent manner with a resultant increase in the secretion of testosterone (T) and 11-ketotestosterone (11-KT). Although ineffective alone, PMA (400 nM) and A23187 (4000 nM) stimulate a small but significant increase (3-fold above basal) in T production. This response is minor compared to the up to 200-fold increase in T secretion observed in response to either hCG or forskolin. PMA (25-400 nM) alone and A23187 (250-4000 nM) alone inhibit the stimulatory actions of hCG on T production. Unlike PMA, the inactive phorbol 4 alpha-phorbol didecanoate, which does not activate PKC, had no effect on hCG-stimulated T production. PMA and A23187 did not influence the effects of forskolin on T production, suggesting that the compounds exert their effects prior to adenylate cyclase activation. In summary, the present studies suggest that in addition to the stimulatory actions of the adenylate cyclase second messenger system, changes in intracellular calcium content and protein kinase C activation may modulate testicular androgen production in the goldfish.

Animals↗
PubMed1984

Training reaction and movement times of moderately and severely mentally retarded persons in aiming movements.

The effect of information feedback of movement components on the reaction time (RT) and movement time (MT) of mentally retarded adults performing a discrete movement aiming task was investigated. We anticipated that specific training and informational feedback on the RT portion of the RT-MT task would more effectively reduce RT, despite aiming requirements of the movement. Results suggested that specific training and feedback on RT decreased both RT and MT components of the task, whereas specific training on MT reduced only MT. The data were discussed with respect to the differential effects of training on subject populations at varying levels of intellectual capacity.

Adult↗
PubMed1982

Coincident timing behavior of young mentally retarded workers under varying conditions of target velocity and exposure.

The degree to which response complexity affects the ability of moderately mentally retarded adults to perform on a coincident timing task was examined. In Experiment 1 subjects were required to depress a key to estimate accurately the arrival of a moving target at a predetermined coincident point. Analyses of both constant and variable error scores suggested that subjects had difficulty inhibiting their responses and that an optimal exposure distance for the task existed. In Experiment 2 subjects were required to make a movement response to the target. Subjects made more constant errors in this experiment but improved when provided maximum target preview. These mixed findings are discussed in terms of subjects' impulsivity and their sensitivity to the characteristics of the display.

Adult↗
PubMed1981

Training moderately and severely mentally retarded adults to improve reaction and movement times.

Two experiments were conducted to examine the degree to which mentally retarded adults can be trained to improve their reaction time (RT) and movement time (MT). A discrete aiming task that had both RT and MT components was utilized in Experiment 1. Only MT improved significantly across the 15 training days, and this performance level was maintained after 5 months without practice. In Experiment 2 the extent to which RT can be trained in the absence of the spatial-temporal constraints of the aiming response was examined. Reaction time decreased significantly for both the training and training-plus-feedback groups over a 10-day training period. The findings demonstrate the role of response complexity in response-initiation processes for retarded adult workers.

Adult↗
PubMed1980

Coincidence anticipation of young normal and handicapped children.

Two coincident-timing experiments examined the role of three different target velocities and display extents and three age levels of normal and retarded children. Subjects made a ballistic response to a target moving horizontally across their visual field. In the first experiment there were generally no clear differences between normal and retarded children on the task, with subjects having difficulty for both the slow and fast target speeds. In the second experiment, with target velocity held constant, no significant differences were reported between normal and handicapped children, although the longer the subjects were allowed to view the target the more accurate they were. The data were discussed in terms of the response strategies to perform anticipatory ballistic movements. An ecological issue was raised which suggested that children as well as adults make their most accurate anticipations when confronted with velocity problems that have been experienced in their everyday world.

Journal Article↗
PubMed1979

Temporal anticipation of response initiation by mentally retarded persons.

The ability of retarded persons to anticipate a signal to initiate discrete movements of varying complexity was investigated in two experiments. The results revealed an interaction between temporal anticipation and response complexity. Experiment 1 showed no reduction in reaction time (RT) in discrete aiming movements when the foreperiod was changed from a random interval to a fixed interval (1 or 3 seconds). Reaction time did not vary with length of the interval or the difficulty of the movement. Experiment 2 showed a reduction of RT to a simple release response at a fixed 1-second warning interval. The findings reflect the difficulty retarded persons have in programming more complex movements and the interaction of temporal anticipation in this response-initiation process.

Adult↗
PubMed1978

Decision time and movement time as a function of response complexity in retarded persons.

The decision time (reaction time [RT]) and movement time of retarded persons as a function of the amplitude and precision of a discrete movement in both simple and choice RT paradigms was examined. The results showed that RT for retarded persons was considerably longer and more variable than for nonretarded persons. Movement difficulty only elevated RT with both populations in the choice RT paradigm, and the RT regression coefficient for the retarded subjects was considerably greater than that for the the nonretarded group. Retarded subjects' movement time was significantly slower than that of the nonretarded subjects. Movement difficulty elevated movement time for both populations, as defined by Fitts's (1954) law. The slope of the movement-time regression coefficients was significantly higher for retarded persons and did not change across 5 days of practice. These findings suggest that information-processing differences in motor skills between populations can be attributed to response parameters.

Achievement↗