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E L Smith

Publications and source records attributed to E L Smith.

At least 109 records · Page 6Linked to original sources
PubMed1990

Orientation bias of neurons in the lateral geniculate nucleus of macaque monkeys.

The purpose of this investigation was to analyze the influence of stimulus orientation on the responses of individual neurons in the monkey's lateral geniculate nucleus (LGN). Our specific goals were to assess the prevalence and the degree of orientation tuning in the monkey LGN and to determine if the preferred stimulus orientations of LGN neurons varied as a function of receptive-field position. The primary motivation for this research was to gain insight into the receptive-field configuration of LGN neurons and consequently into the neural mechanisms which determine the spatial organization of LGN receptive fields in primates. In both the parvocellular and magnocellular layers, the responses of the majority of individual neurons to sine-wave gratings varied as a function of stimulus orientation. The influence of stimulus orientation was, however, highly dependent on the spatial characteristics of the stimulus; the greatest degree of orientation bias was observed for spatial frequencies higher than the cell's optimal spatial frequency. On a population basis, the degree of orientation bias was similar for all major classes of LGN neurons (e.g. ON vs. OFF center; parvocellular vs. magnocellular) and did not vary systematically with receptive-field eccentricity. At a given receptive-field location, LGN neurons, particularly cells in the parvocellular laminae, tended to prefer either radially oriented stimuli or stimuli oriented more horizontally than their polar axis. Our analyses of the orientation-dependent changes in spatial-frequency response functions, which was based on the Soodak et al., (1987; Soodak, 1986) two-dimensional, difference-of-Gaussian receptive-field model, suggested that the orientation bias in LGN neurons was due to an elongation of the receptive-field center mechanism which in some cases appeared to consist of multiple subunits. Direct comparisons of the orientation-tuning characteristics of LGN cells and their retinal inputs (S potentials) indicated that the orientation bias in the monkey LGN reflects primarily the functional properties of individual retinal ganglion cells. We conclude that orientation sensitivity is a significant property of subcortical neurons in the primate's geniculo-cortical pathway.

Action Potentials↗
PubMed1990

Bone mechanical properties after exercise training in young and old rats.

The effects of a 10-wk training regimen on the mechanical properties of the femur and humerus were evaluated in 2.5- and 25-mo-old Fischer 344 female rats. The rats trained on a rodent treadmill 5 days/wk for 10 wk. Duration, grade, and speed increased until the rats maintained 1 h/day at 15% grade and either 15 m/min (old rats) or 36 m/min (young rats). Excised bones were mechanically tested with a 3-point flexure test for mechanical properties of force, stress, and strain. Fat-free dry weight (FFW) and moment of inertia were also obtained. With aging, similar increases were observed in both the femur and humerus for FFW, moment of inertia, and force. Ultimate stress was reduced in the senescent femur while strain was elevated; a similar but nonsignificant trend was observed in the humerus. Irrespective of age, training increased FFW in the femur and, to a lesser degree, in the humerus. Breaking force was elevated for both bones after training. In young and old bones, the training-induced differences in bone mass and force were similar, despite differences in training intensity. In the old trained rats, femur ultimate stress was greater than that in control rat femurs and similar to that in young rat femurs. The results of the present study indicate that training effects were not limited by age.

Aging↗
PubMed1989

Comparison of the form(s) of cytochrome P-450 induced by ethanol and glutethimide in cultured chick hepatocytes.

In this study, using a combination of immunological and enzymatic characterizations, we compared the forms of cytochrome P-450 induced by ethanol and glutethimide in primary cultures of chicken embryo hepatocytes. Recently we purified a cytochrome P-450 of 50K molecular weight from chicken embryo liver using glutethimide as a prototypic inducer. Antibodies to both this chicken cytochrome P-450 and to rabbit cytochrome P-450 form 3a from the IIE subfamily detected microsomal proteins of 50K induced by either ethanol or glutethimide in cultured chick embryo hepatocytes, indicating the antigenic homology of these subfamilies of cytochromes P-450 among different animal species. However, the antibody to glutethimide-induced chick cytochrome P-450 of 50K inhibited p-nitrophenol hydroxylase and benzphetamine demethylase activities 85-90% in microsomes from both ethanol- and glutethimide-treated cells, indicating similar epitopes whose integrity is required for catalytic activity. In contrast, antibodies to rabbit cytochrome P-450 form 3a had little to no effect on these same microsomal activities. Both ethanol and glutethimide induced microsomal p-nitrophenol and aniline hydroxylase activities in cultured chick embryo hepatocytes. In microsomes from ethanol-treated cells, the turnover of p-nitrophenol per cytochrome P-450 was 2-fold greater than that induced by glutethimide treatment, suggesting that ethanol is inducing a form of cytochrome P-450 that has greater catalytic activity with this substrate than glutethimide-induced forms. Thus, in cultured chick embryo hepatocytes, ethanol may induce cytochromes P-450 from both the IIB and IIE subfamilies.

Animals↗
PubMed1989

The effects of reverse monocular deprivation in monkeys. I. Psychophysical experiments.

Monkeys had one eye closed at about 30 days of age for 14, 30, 60, or 90 days, then opened, and the fellow eye closed for another 120 days. The animals then had at least 10 months of binocular visual experience before behavioral training and testing were begun. All subjects were used in a series of psychophysical investigations during the next two years. The results of the behavioral studies indicated that the initially deprived eyes (IDE) of the two monkeys that were subjected to initial deprivation periods of 14 or 30 days recovered normal or near-normal spatial contrast sensitivity. In contrast, the two animals which underwent longer periods of initial deprivation showed incomplete recovery, especially for high spatial frequency stimuli. All of the monkeys exhibited a reduction in spatial contrast sensitivity for their reverse deprived eyes (RDE); the earlier the onset of the reverse-deprivation procedures (i.e., the shorter the initial period of deprivation), the greater the deficit in the RDE's spatial contrast sensitivity. Measurements of temporal contrast sensitivity showed that all of the subjects' IDEs had normal or near-normal sensitivity levels. However, the reverse-deprivation procedures initiated at 90 days of age or earlier produced a frequency-dependent reduction in the RDE's temporal modulation sensitivity. The measures of increment-threshold spectral sensitivity revealed that only the RDE of the monkey that had the shortest initial deprivation period had an abnormal spectral sensitivity function. The results demonstrate that many of the severe behavioral deficits produced by early monocular form deprivation can be recovered via reverse-deprivation procedures. However, depending upon the length of the initial deprivation period and the age at which the reversal procedure is initiated, the second deprivation period can also adversely affect the functional capacity of the RDE.

Animals↗
PubMed1989

The effects of reverse monocular deprivation in monkeys. II. Electrophysiological and anatomical studies.

Monkeys had one eye closed at about 30 days of age for 14, 30, 60, or 90 days, then opened, and the fellow eye closed for another 120 days. The animals then had at least 10 months of binocular visual experience before extensive behavioral training and testing were carried out. In terminal experiments concluded more than 18 months later, microelectrode investigations of the striate cortex demonstrated that there was almost a complete absence of binocular neurons in all animals. The initially deprived eyes (IDEs) dominated the majority of cortical neurons, even when soma size measurements of lateral geniculate neurons indicated that the LGN cells driven by the IDE had not regained their normal size. The monkeys which had significant interocular differences in spatial vision also exhibited abnormalities in the distribution of the metabolic enzyme, cytochrome oxidase (CO), within the striate cortex. These results demonstrate that many of the severe alterations in cortical physiology and eye dominance produced by early monocular form deprivation can be reversed, with recovery of normal cortical function, via the reverse-deprivation procedure.

Animals↗
PubMed1989

Dual photon absorptiometry of the proximal tibia.

Bone mineral content (BMC) and bone mineral density (BMD) of the proximal tibia were determined by dual photon absorptiometry on 44 women, aged 23-87 years. The area of the tibia measured was a 2.01 cm region immediately distal to the medial and lateral tuberosities. Values of BMC ranged between 5.09 and 14.57 g and BMD between 0.380 and 1.180 g/cm2. Both tibial BMC and BMD declined with age and tibial BMD was significantly correlated with lumbar spine (r = 0.70), femoral neck (r = 0.73), and femoral trochanter (r = 0.74). However, the large standard errors of estimate (SEE) (0.08-0.14 g/cm2) do not allow for reliable prediction in an individual of other skeletal sites by the tibia. Repeated measurements demonstrated that dual photon absorptiometry of the proximal tibia is a reliable measurement and may be a useful tool in the monitoring of therapeutic or intervention modalities in those individuals with skeletal diseases in whom measurement of the lumbar spine or proximal femur may not be possible.

Absorptiometry, Photon↗
PubMed1989

Deterring bone loss by exercise intervention in premenopausal and postmenopausal women.

This study investigated the efficacy of 4 years of exercise intervention in deterring bone loss in middle-aged women, and is a correction and extension of previously published data. Sixty-two control subjects (mean age 50.8) and 80 exercise subjects (mean age 50.1) completed a 4-year study. Subjects exercised three times a week, 45 minutes per session. Bilateral radius, ulna, and humerus bone mineral content (BMC) and width (W) were measured on each subject 11 times over the 4-year period. The two groups did not differ initially in age, height, or weight, but the control group had a greater maximum VO2 (ml/kg/min) than the exercise group. Slopes and intercepts of the bone variables vs. time were determined for each subject, and these values were used for between-group comparisons of loss. The control group BMC and BMC/W declined significantly in all three bones in both arms. The exercise group rate of decline was significantly less than that of the control group for 12 of the 18 bone variables. The greatest effect of the exercise intervention was on the ulna and radius. Exercise subjects lost significantly less than control subjects in left and right ulna and radius BMC and BMC/W, and left ulna and radius W. Lesser differences between groups were observed in the humerus. BMC and W loss rates of the left humerus were reduced in the exercise group, with no difference between exercise and control subjects in the other humerus variables. To determine if menopausal status influenced the response to exercise, we analyzed the difference between groups for premenopausal and postmenopausal subjects separately. Regardless of menopausal status, exercise subjects had lower bone loss rates than control subjects. In both premenopausal and postmenopausal subjects, exercise reduced bone loss significantly for 10 of the 18 bone variables. It can be concluded that physical activity significantly reduces bone loss in the arms of middle-aged women.

Adult↗
PubMed1989

Effects of chronic optical defocus on the kitten's refractive status.

Lid closure initiated early in life produces axial myopia in a variety of species. However, it is currently not known what aspects of the anomalous visual experience associated with lid closure disrupt the emmetropization process and cause abnormal ocular axial elongation. This study was designed to determine if a degradation in the quality of the spatial characteristics of the retinal image was sufficient to produce an experimental myopia. Optical rearing procedures were employed to defocus one eye of developing kittens, and retinoscopic and ultrasonic procedures were used to evaluate the effects of chronic optical defocus on the kitten's refractive status. Different defocusing lens designs and rearing protocols were included to evaluate variables that may have confounded previous investigations. The major finding is that early chronic optical defocus results in axial myopia. The prevalence and magnitude of the induced refractive errors were dependent on the magnitude of optical defocus, but they were not affected by the sign or form of the defocusing lens. The results demonstrated that the potential for a clear retinal image is important for regulating normal ocular growth and maintaining a near emmetropic refractive status.

Animals↗
PubMed1989

Contribution of the retinal ON channels to scotopic and photopic spectral sensitivity.

Visual information encoded by the middle-wavelength-sensitive (MWS) and long-wavelength-sensitive (LWS) cones in the primate retina are processed by both depolarizing (ON) and hyperpolarizing (OFF) bipolar cells. In contrast, signals from the short-wavelength-sensitive (SWS) cones and dark-adapted rod photoreceptors are thought to be carried almost exclusively by ON bipolar cells (Gouras & Evers, 1985). Consequently, it would be expected that functional inactivation of the retinal ON channels at the bipolar cell level would produce selective deficits in visual functions mediated by rods and SWS cones. We have examined this hypothesis by injecting rhesus monkeys with 2-amino-4-phosphonobutyric acid (APB), a pharmacological agent that reduces the responsiveness of retinal ON neurons, and psychophysically measuring the changes in spectral sensitivities. Under adaptation conditions that isolated rod function, APB caused, as expected, a substantial loss in rod-mediated spectral sensitivity. However, under photopic conditions, cone-mediated spectral sensitivity, including that associated with the SWS cones, was relatively unaffected. These results demonstrate distinct organizational differences between the rod and cone systems; specifically, they indicate that the rod system is more dependent upon retinal ON channels than the cone system. Our failure to find a selective visual deficit related to SWS cone function under photopic viewing conditions suggests that the OFF system can mediate stimulus detection throughout the visible spectrum and that the ability of the OFF system to process signals from the SWS cones has been underestimated.

Aminobutyrates↗
PubMed1989

Calcium supplementation and bone loss in middle-aged women.

This 4-y study investigated the effects of a calcium carbonate supplement on bone loss in 169 women aged 35-65 y, randomly assigned to placebo and treatment (1500 mg Ca/d) groups in a double-blind design. Bone mineral content (BMC) and width (W) were measured bilaterally on the radius, ulna, and humerus. BMC and BMC/W loss rates were consistently lower in treatment than in control subjects. Loss was significantly reduced in the left and right humerus and the right radius. In premenopausal subjects, only left humerus BMC loss was significantly reduced by Ca supplementation. In postmenopausal treatment subjects, BMC and BMC/W bone loss was reduced in all 12 (bilateral radius, ulna, and humerus) of the bone variables measured, 5 at p less than 0.01 and 2 at p less than 0.05. Ca supplementation counteracted a large portion of the additional bone loss attributable to menopause in this population.

Absorptiometry, Photon↗
PubMed1989

Organizational analysis: tool for the clinical nurse specialist.

It has been asserted that nurse leaders must have the knowledge base and skills necessary to intervene effectively in complex organizational systems. In order to facilitate the acquisition of this knowledge and skill, one graduate nursing program preparing clinical nurse specialists (CNSs) uses an organizational analysis that students complete during their clinical experience. This article presents a description of the process and the benefits derived from doing the analysis both for graduate nursing students and practicing CNSs.

Education, Nursing, Graduate↗
PubMed1988

Effect of 17 alpha-ethynylestradiol on the induction of cytochrome P-450 by 3-methylcholanthrene in cultured chick embryo hepatocytes.

This study investigated the effects of estrogens on the induction of cytochrome P-450 by polycyclic aromatic hydrocarbons in primary cultures of chick embryo hepatocytes. Exposure to polycyclic aromatic hydrocarbons, such as 3-methylcholanthrene led to 2- to 3-fold increases of cytochrome P-450. The amount of cytochrome P-450 induced by 3-methylcholanthrene was increased 40-50% when the synthetic estrogen, 17 alpha-ethynylestradiol, was also present. The rate of decay of cytochrome P-450 in the presence of cycloheximide as measured spectrophotometrically was similar in cells previously treated with either 3-methylcholanthrene or 3-methylcholanthrene plus 17 alpha-ethynylestradiol, suggesting that 17 alpha-ethynylestradiol did not affect the stability of the 3-methylcholanthrene-induced cytochrome P-450. In contrast, 17 alpha-ethynylestradiol did not potentiate the induction of cytochrome P-450 by phenobarbital-like inducers, such as 2-propyl-2-isopropylacetamide, as indicated by a lack of increase in both the content of cytochrome P-450 and benzphetamine demethylase activity. The naturally occurring estrogens, 17 beta-estradiol and estrone, and the synthetic estrogen, diethylstilbestrol, did not affect cytochrome P-450 induction by 3-methylcholanthrene, suggesting that the effect of 17 alpha-ethynylestradiol was not mediated via the estrogen receptor. We investigated whether the amount of cytochrome P-450 increased in the presence of 17 alpha-ethynylestradiol was the same or different from that induced by 3-methylcholanthrene. Treatment with 17 alpha-ethynylestradiol alone resulted in a small increase in ethoxyresorufin deethylase activity. The enzymatic activities of 7-ethoxyresorufin and aryl hydrocarbon hydroxylase, when expressed per cytochrome P-450 content, were identical in microsomes from cells treated with either 3-methylcholanthrene or the combination of 3-methylcholanthrene and 17 alpha-ethynylestradiol. The data suggest that the additional cytochrome P-450 induced by the combination of 17 alpha-ethynylestradiol and 3-methylcholanthrene was the same isozyme as that induced by 3-methylcholanthrene alone.

Animals↗
PubMed1988

A novel approach for the evaluation and treatment of psoriasis. Oral or topical use of 1,25-dihydroxyvitamin D3 can be a safe and effective therapy for psoriasis.

We investigated the effects of 1,25-dihydroxyvitamin D3 (1,25-(OH)2-D3) on cultured fibroblasts and keratinocytes from patients with psoriasis and treated 17 patients with psoriasis with orally or topically administered 1,25-(OH)2-D3. Cultured fibroblasts from three of five patients showed a normal response to the antiproliferative activity of a physiologic dose of 1,25-(OH)2-D3, whereas fibroblasts from the other two had a partial resistance to the drug. Cultured keratinocytes from two patients with psoriasis possessed nuclear receptors for 1,25-(OH)2-D3 and the drug caused a dose-dependent inhibition of proliferation and induction of terminal differentiation of these cells similar to effects in normal cultured keratinocytes. Ten of 14 patients with moderate to severe psoriasis who received oral 1,25-(OH)2-D3 showed significant clearing of their hyperkeratotic plaques. Three patients had complete clearing that was sustained with maintenance therapy, but four patients received little or no benefit from the therapy. By the administration of 1,25-(OH)2-D3 as a single oral dose at bedtime, larger doses of the drug could be tolerated without evidence of hypercalciuria or hypercalcemia. Three patients who received topical 1,25-(OH)2-D3 showed a rapid response with complete clearing after 6 weeks of therapy. Therefore, these preliminary findings suggest that orally or topically administered 1,25-(OH)2-D3 may be a safe and effective alternative therapy for the treatment of psoriasis.

Administration, Cutaneous↗
PubMed1988

Light resistance and stretching exercise in elderly women: effect upon flexibility.

Decreased range of motion (ROM) due to disuse limits the older adult's ability to perform daily activities. The flexibility of five joints of 46 women (aged 65 to 89 years) was measured by goniometer before and after a 25-week exercise program. Three groups were formed: a control group who did no exercise (C) (n = 13), a group who exercised with light weights (EW) (n = 17), and a group who exercised with no weights (EN) (n = 16). Subjects who exercised (EN and EW) gained significantly greater ROM in ankle plantar flexion, shoulder flexion, shoulder abduction, and left neck rotation than C subjects. No significant differences were found between groups in hip flexion, right neck rotation, wrist flexion or extension, or ankle dorsiflexion. The only difference between exercise treatments was that the EN group gained significantly more ROM in shoulder abduction than the EW. The use of arm weights may have limited shoulder ROM during exercise, resulting in less improvement for shoulder abduction. Comparison with data from other studies suggests age-related loss in flexibility at the shoulder joint. Exercise generally increased shoulder ROM and may be capable of reversing loss in flexibility due to disuse.

Aged↗
PubMed1988

Light resistance and stretching exercise in elderly women: effect upon strength.

Forty-seven elderly women (63 to 88 years of age, mean = 71 years) were studied to determine the effect of a 25-week light resistance and aerobic exercise program upon arm and leg strength. Three groups were formed: nonexercising controls (C, n = 12), exercise (EN, n = 18) and exercise with light weights on on the wrists and ankles (EW, n = 17). Exercise was performed for one hour, three times/week. Subjects were pretested and posttested for maximal isokinetic muscle strength (angular velocity 60 degrees/sec) for elbow flexion and extension, shoulder internal and external rotation, and knee flexion and extension. Dunn planned contrasts were used to compare C vs exercise groups combined (EN + EW) and EN vs EW. No significant differences were found among groups at baseline. EN + EW improved significantly (p less than 0.05) more than C in elbow extension (17%), shoulder internal rotation (14%), shoulder external rotation (9%), and knee flexion (20%). No significant differences were found between EN and EW. These data indicate that elderly women can achieve substantial gains in the strength of arm and leg musculature as a result of regular light resistance and aerobic exercise, but that the use of light weights on the wrists and ankles for added resistance did not enhance this effect.

Aged↗