Functional effects of bilateral form deprivation in monkeys

Psychophysical methods were used to study the effects of binocular form deprivation, initiated at 1 month of age, on the visual sensitivities of young monkeys. All the monkeys reared with bilateral form deprivation for 7 weeks or longer had reduced spatial contrast sensitivity for both eyes. Although the contrast sensitivity deficits of the bilaterally form-deprived monkeys generally were larger for one eye than the other, the magnitudes of the deficits were small compared with those produced by similar periods of unilateral form deprivation. For other monocular vision functions investigated, temporal contrast sensitivity and increment-threshold spectral sensitivity, the data for the bilaterally form-deprived animals showed only minor variations from those of the control monkeys. However, none of the bilaterally form-deprived monkeys had binocular vision on either measures of binocular summation or stereodetection, even if the animal had normal monocular vision functions. Therefore, these results show that monocular sensory deficits caused by abnormal early visual experience as a result of bilateral form deprivation are much less severe than those caused by unilateral form deprivation. The differences in the severity of visual deficits may be attributed to the consequences of anomalous binocular competition associated with unilateral form deprivation that was minimized during bilateral form deprivation. Thus, these results illustrate that anomalous binocular competition is more detrimental to the developing visual system of infants than direct deprivation per se.

Bilateral form deprivation in monkeys. Electrophysiologic and anatomic consequences

The response characteristics of neurons in the striate cortex are described for rhesus monkeys that underwent bilateral form deprivation by surgical closure of the eyelids starting within the first month of life and lasting for 2, 6, 7, 13, or 16 weeks. The monkeys had been tested for visual deficits resulting from these experimental deprivations. Single-unit recordings from the striate cortices of these animals showed a single significant abnormality; the absence of excitatory binocular input. Whereas, 76% of the neurons in the foveal striate cortex of the normal animals were binocular, fewer than 20% of the neurons in the experimental monkeys were binocular. However, each eye was well represented by monocular cells. As demonstrated in oblique microelectrode penetrations, the cortical eye-dominance zones for each eye appeared to be of equal width with sharp transitions at the monocular boundaries. The sizes of the cells of the lateral geniculate nuclei were smaller (-15%) than those in controls. Binocular form deprivation early in life has its most obvious effect on the physiology and function of cortical binocular neurons and secondarily on the size of neurons of the lateral geniculate nucleus.

A histomorphometric study of cortical bone activity during increased weight-bearing exercise

To quantify cortical bone response to weight-bearing exercise, bone size, mineral content, and formation were measured at the femoral midshaft in swine. Bone formation was measured histomorphometrically on the periosteal, endosteal, and osteonal surfaces. Sedentary adult crossbred sows (3 years, 229 kg) were randomly assigned to basal (B, n = 6), control (C, n = 7), or trained (T, n = 7) groups. The basal and control groups did not exercise and were killed initially (B) or after 20 weeks (C). The trained group walked on a treadmill 20 minutes/day at 5 km/h and 5% grade, 5 days/week for 20 weeks. Bone length, area, or fat-free dry weight was not different with time (B versus C) or with training (C versus T). Periosteal modeling was stimulated by walking. Periosteal formation surface and mineral apposition rate (MAR) were greater in trained than control femora. No effects of walking were measured on the endosteal surface. Intracortical remodeling was not affected by walking. The number of labeled osteons (22.4 cm-2) was not different among groups, but osteonal MAR was greater in trained (1.18 microns/day) than control (0.96 mu/day) femora. Walking for 20 weeks in the previously sedentary sows was not a sufficient stimulus to create differences in gross measures of bone size or mineral content but did increase periosteal and intracortical MAR. The primary effect of increased exercise appeared to be osteoblast activation.

Effect of training on VO2max, thigh strength, and muscle morphology in septuagenarian women

The purpose of this study was to determine the effects of a long-term (50 wk) combined aerobic-resistance training program on maximal oxygen consumption (VO2max, thigh strength, and vastus lateralis fiber morphology in healthy septuagenarian women (mean age = 72 +/- 6 yr). Subjects volunteered to be in either an exercise (Ex; N = 17) or control (Con; N = 10) group. Con subjects were 34% less active in winter than in summer, Ex subjects maintained their summer activity level on exercise days in winter. Initial, intermediate (20 wk), and final (50 wk) measurements were made for isokinetic knee extension/flexion strength; VO2max and morphological measurements from a muscle biopsy were made at the initial and final times only. Both groups gained in leg strength (Ex = +6.5%; Con = +7.8%; P less than or equal to 0.05) during the summer; in the winter the Ex group maintained leg strength and the Con group declined 12.2% (P less than or equal to 0.05). The fast-twitch muscle fiber area (Type IIb) increased 29% (P less than or equal to 0.001) in the Ex group and declined 26% (P = 0.014) in the Con group. VO2max increased only in the Ex group (16%; P less than 0.001). We conclude that healthy septuagenarian women can increase aerobic capacity, leg strength, and Type IIb muscle fiber area with a long-duration, combined aerobic-resistance exercise program.

Muscular strength and bone density with weight training in middle-aged women

Previous research has demonstrated positive correlations between bone mass and both physical activity and muscular strength. There is a paucity of information describing the specific type of exercise which most benefits the human skeleton. The effects of a 1 yr weight training program on 18 middle-aged women participating in an endurance dance program (E + W) compared with 17 other women in the endurance dance program only (E) and with 19 sedentary controls (C) were studied by measuring muscular strength and bone mineral density (BMD). Eighteen women in the E + W group demonstrated increases in all strength measurements, whereas the E and C groups either had smaller increases or had declined. A significant group x test interaction term, indicating that groups responded differently over time, was observed for nondominant isokinetic elbow flexion measured through the range of motion at a constant velocity of 60 degrees.s-1 (P less than 0.05), nondominant isokinetic elbow extension at 180 degrees.s-1 (P less than 0.01), and nondominant isokinetic elbow flexion at 180 degrees.s-1 (P less than 0.05). BMD did not change significantly except that a significant group x test interaction term appeared for the radius ultradistal site (P less than 0.01). BMD of the humerus and femoral Ward's triangle increased nonsignificantly in both E and E + W over the year. This weight training program increased muscular strength but did not increase measured bone mass.

Disruption of binocularly correlated signals alters the postnatal development of spatial properties in cat striate cortical neurons

1. Extracellular single-cell recording techniques were employed to investigate the effects of ocular misalignment on the postnatal development of the spatial response properties of striate cortical neurons. The primary objective of the study was to gain insight into the neural basis of strabismic amblyopia. 2. Two basic rearing strategies were used to study specific aspects of experimental strabismus in developing kittens. In one group, strabismus was optically induced by fitting kittens with goggles that held a 15-diopter base-in prism in front of one eye (MP) or both eyes (BP) between the ages of 4 wk and 4 mo. In the second group, a unilateral esotropia was surgically induced at 3 wks of age either by the simple resection of the lateral rectus muscle tendon (tenotomy) or by a more drastic procedure that involved removing sections of the lateral rectus and superior oblique muscles (myectomy). In addition, the eyelids of the nondeviating eyes of these kittens were sutured closed (ESO/MD). The first rearing paradigm isolated the effects of conflicting visual inputs on neural development, whereas the second procedure isolated the effects of anomalous ocular motility by producing a misalignment without putting the deviated eye at a competitive disadvantage. 3. The recording experiments were conducted when the animals were greater than or equal to 9 mo of age. A total of 445 striate cortical neurons were isolated and quantitatively studied in 17 cats (3 MPs, 3 BPs, 5 ESO/MDs, 3 goggle-reared controls, and 3 normals). In addition, we analyzed the distribution of preferred stimulus orientations of 1,205 single units that had been studied qualitatively in our previous investigation of 42 kittens reared with optically induced strabismus. 4. As expected, the proportion of binocularly driven units was reduced in both MP and BP cats. The great majority of units in ESO/MD animals were exclusively driven or highly dominated by the open deviating eye. 5. Prism-reared animals showed physiological deficits in spatial resolution, contrast sensitivity, contrast gain, and peak firing rate. These effects were manifest in both eyes, although there was always an interocular asymmetry in the deficits observed in the two eyes. In MP animals, the units dominated by the treated eye, which was contralateral to the recording hemisphere, were on the average more severely affected. The interocular asymmetry was smaller in BP cats; however, two of the three BP animals also showed a greater deficit in those units dominated by the contralateral eye.(ABSTRACT TRUNCATED AT 400 WORDS)

Physical activity effects on bone metabolism

The incidence of osteoporotic fractures rises exponentially with age and is increasing faster than the demographic increase in the aging population. Physical activity has great potential to reduce the risk for osteoporotic fractures. Three independent but interactive factors contribute to the risk of fractures: bone strength, the risk of falling, and the effectiveness of neuromuscular response that protects the skeleton from injury. Exercise can reduce fracture risk not only by preventing bone loss, but by decreasing the risk of falling and the force of impact by improving strength, flexibility, balance, and reaction time. Extreme inactivity causes rapid bone loss of up to 40%, while athletic activity results in bone hypertrophy of up to 40%. Exercise intervention programs have reduced bone loss or increased bone mass in both men and women of various ages and initial bone status. These benefits have been shown for arm bone mineral content, total body calcium, spine, calcium bone index, tibia, and calcaneus. In both middle-aged and elderly women, physical activity intervention reduced bone loss or increased bone mass. The mechanisms for maintenance of skeletal integrity rely on a cellular response to hormonal and mechanical load stimuli. Studies in animal models show that training affects cellular activity. In osteoporotics, cellular erosion is increased and mineral apposition rate (MAR) decreased compared with normal age-matched controls. In contrast to this, sows trained on a treadmill 20 min per day for 20 weeks had greater active periosteal surface, periosteal MAR, and osteonal MAR than untrained sows.

Refractive-error changes in kitten eyes produced by chronic on-channel blockade

The dependence of the emmetropization process on retinal ON-channel activity was examined in developing kittens by making regular intravitreal injections of D,L-2-amino-4-phosphonobutyric acid (APB). In comparison to sham-injected control eyes, the APB-treated eyes had shorter axial lengths and were more hyperopic. Since chronic atropinization did not alter the development of the APB-induced hyperopia, these anomalous refractive errors are not the result of altered accommodative function. The axial hyperopia observed in the APB-treated eyes indicates that the mechanisms responsible for normal axial elongation are dependent to some extent on ON-channel activity and that, even in the presence of a clear retinal image, OFF-channel activity, by itself, is not sufficient to regulate the normal emmetropization process.

Behavioral studies of the sensitive periods of development of visual functions in monkeys

The age-dependent effects of monocular form deprivation on psychophysically determined visual functions were investigated in rhesus monkeys. Monocular form deprivation was initiated at various ages from 1 to 25 months and maintained for 18 months. The effects of form deprivation varied across the visual functions evaluated. Absolute scotopic sensitivity was depressed by form deprivation initiated only at 1 or 2 months of age. Photopic, increment-threshold spectral sensitivity functions showed alterations in sensitivity levels for monkeys treated at 5 months of age or earlier, with no effect thereafter. Monocular form deprivation at 1 to 5 months of age resulted in profound deficits in spatial modulation sensitivity. The effects on spatial vision decreased systematically as the age of onset was delayed from age 6 to 18 months. Finally, binocular summation measures revealed an absence of binocular vision even for the monkey form-deprived at 25 months of age, i.e. the experimental treatment series failed to define the upper limit of the age-range for the effects of monocular form deprivation on binocular summation mechanisms. Comparisons of the age-dependent effects of monocular form deprivation across the various functions demonstrated that the sensitive period, i.e. the period of life during which a visual function may be altered by monocular form deprivation, was different for each of the psychophysical measures of visual function.

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.

Spatio-temporal interactions and the spatial phase preferences of visual neurons

We recorded single neuron responses in the cat's lateral geniculate nucleus (LGN) and visual cortex to compound stimuli composed of two sinusoidal gratings in a 2:1 frequency ratio. To probe visual receptive field symmetry, we varied the relative spatial phase of the two components and measured the effect on neuronal responses. We expected that on-center LGN neurons would respond best to gratings combined in positive cosine (bright bar) phase, while off-center LGN neurons would respond best to gratings combined in negative cosine (dark bar) phase. When drifting stimuli were used, cells' phase preferences were roughly 90 deg away from the expected values; when stationary, contrast-modulated stimuli were used, phase preferences were as originally predicted. Computer simulations showed that this discrepancy could be explained by taking into account the cells' temporal properties. Thus, tests using drifting stimuli confound the spatial structure of visual neural receptive fields with their temporal response characteristics. A small sample of data from cortical neurons reveals the same confound.

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.

Hepatic alcohol dehydrogenase activity in chick hepatocytes towards the major alcohols present in commercial alcoholic beverages: comparison with activities in rat and human liver

We have compared hepatic alcohol dehydrogenase activities in chick, rat and human liver with the major alcohols in commercial alcoholic beverages. 1. Chick and rat hepatic alcohol dehydrogenase was greater when assayed at a physiological pH in buffer containing chloride ions, as compared with the activity in pyrophosphate buffer at alkaline pH. 2. In contrast to reports of instability of ADH to freezing, we found the enzyme from all three species stable to freezing in 0.25 M sucrose. 3. Rat liver enzymatic activity was unstable in the presence of substrate, where as that of chick and human was not. 4. For all three species, the Km of hepatic ADH for substrate decreased with increasing chain length of alcohols. In both chick and human samples, the Vmax values for the higher chain alcohols were similar to that with ethanol, while in rat samples, ADH activity was dramatically lower with the higher chain alcohols compared to ethanol.

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.

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.

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.

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.

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.

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.

Soil surface features as indicators of rangeland site productivity

Criteria for the classification of Red Earth soils into groups reflecting differences in their productive potenrial were investigated on three sites near Cobar, New South Wales. Five features were shown to be useful by cluster and discriminate analysis of an extensive data set. A field-based classification using six very similar criteria was also tested and shown to agree with the cluster method. Laboratory tests for stability and fertility of the surface soil layer from each class indicated a significant difference between classes, and a narrow range of values for an individual class. Herbage production on quadrats over the range of soil surface condition also consistently reflected the classification. When the method was tested with three personnel previously unfamiliar with the criteria, good agreement with the original experimental set was obtained.

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.

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.

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.