Microscopic artifact found during examination of the skin: plant hair of Viburnum dentatum.

Examination of skin specimens with microscopic techniques requires differentiation of pathogenic structures from artifact. While preparing potassium hydroxide preparations for fungal identification or immersion oil preparations for scabies identification, we have recently seen several examples of a bizarre stellate or cruciform plant structure. These artifactual particles were identified as plant hairs from Viburnum dentatum, or arrowwood. Clinicians and laboratory technicians should be aware of this artifact in order to interpret microscopic skin specimens appropriately.

Thigmomorphogenesis: the effect of mechanical perturbation on plants.

Thigmomorphogenetic responses occur in many environmental settings. The most pronounced effects are found under conditions of extremely high rates of turbulent wind or water flow. However, it is an ubiquitous phenomenon, since mechanical perturbations are to be encountered under all but the most stringent laboratory conditions. Our present understanding of these phenomena is the result of studies at the ecological, anatomical, physiological, biochemical, biophysical and molecular biological levels.

Eye movement disorders in men with isolated hypogonadotropic hypogonadism.

The eye movement abnormalities in two men with isolated hypogonadotropic hypogonadism were studied clinically and electro-oculographically. Both demonstrated striking saccadic dysmetria. Subsequent neuroradiologic investigation confirmed atrophy of the cerebellar vermis in one of the patients. This is in concert with other midline structural abnormalities described in patients with isolated hypogonadotropic hypogonadism and suggests that this syndrome may arise from a genetically linked developmental abnormality of midline central nervous system structures.

Neurologic findings in men with isolated hypogonadotropic hypogonadism.

We studied the neurologic abnormalities in 41 men with isolated hypogonadotropic hypogonadism. Findings included anosmia, hyposmia, mirror movements, ocular motor abnormalities, cerebellar dysfunction, and pes cavus foot deformity. One-third of the subjects had a family history of delayed sexual maturation. Patients with a family history of delayed sexual maturation had a significantly higher incidence of olfactory dysfunction, mirror movements, and pes cavus foot deformity. Our data suggest that isolated hypogonadotropic hypogonadism and its accompanying neurologic abnormalities may arise from a genetically linked developmental abnormality of CNS structures.

A screening method using tissue culture for evaluation of potential retinal adhesives.

Several adhesives have been tested for their potentially toxic effects on embryonic retinal tissue. The authors have characterized the effects of the adhesives on neurofilament extension and also on surgical-wound "re-knitting." While none of the adhesives in the sample (including those in current surgical use) seem to be ideal, the model advanced has application for the continuing development of better 'bio-adhesives'. The most immediate application is within the field of vitreoretinal surgery in situations where conventional procedures currently seem inadequate.

Attenuating effects of diazepam on the electroretinogram of normal humans.

Response/log I curves were obtained under conditions of dark-and light-adaptation in seven normal male volunteers. For each subject, a baseline electroretinogram (ERG) was recorded. In the same afternoon, a second ERG was obtained after 0.05 mg/kg diazepam, and a third ERG was recorded following 0.10 mg/kg diazepam. Under conditions of dark-adaptation, the following dose-dependent changes were identified: 1) Diazepam attenuated the rod b-wave peak amplitude and increased its implicit time; 2) The dark-adapted longer wavelength cone a-wave and 'blue cone' b-wave showed an increased implicit time; 3) All oscillatory potentials showed an increased implicit time. Under conditions of light-adaptation, dose-dependent decreases in peak amplitude and delays in implicit time were observed for the a- and b-waves. The effects of diazepam on the human ERG were more profound under conditions of light- than dark-adaptation.

Spatial contrast sensitivity: effects of age, test-retest, and psychophysical method.

Spatial contrast sensitivity was tested twice in normal subjects from five age groups by using each of two different psychophysical methods. Results obtained by the method of adjustment showed a decline in sensitivity with increasing age at all spatial frequencies. In contrast, the forced-choice procedure yielded results indicating an age-related decline predominantly at high spatial frequencies, with the magnitude of the decline being generally similar to that obtained earlier by a tracking method [Vision Res. 23, 689 (1983)]. The decline that we observed cannot be due to pupillary changes with age, since this factor was controlled. Moreover, we suggest that the high-spatial-frequency decline in contrast sensitivity, although it is comparatively small, is too large to be due to changes in lens density. We therefore suggest that a neural component is responsible. In addition, interactions among the age of the subject, the spatial frequency used, and the psychophysical method used suggest that the method of adjustment should be avoided for age-related studies of vision.

Ophthalmic midline dysgenesis in Kallmann syndrome.

Partial coloboma, observed only with transillumination techniques, occur in 16% of male patients diagnosed with Kallmann syndrome. This sign represents an additional midline defect in this multisystem disorder noted for midline dysgenesis. Its high incidence may be helpful in the diagnosis of this disorder although it does not appear to be the harbinger of any other ocular abnormality.

Ganzfeld electroretinographic findings in parkinsonism: untreated patients and the effect of levodopa intravenous infusion.

Two groups of patients with primary Parkinsonism were studied with the ganzfeld electroretinogram (ERG): seven patients who had never received dopamimetic agents, and six patients given an infusion of levodopa following a period of medication withdrawal. Patients in the first category had a subtle increase in the latency of their short-wavelength sensitive cone response recorded from the retina ipsilateral to their more symptomatic side. Most patients in the second category demonstrate an improvement in their ERG when the responses recorded following levodopa infusion were compared with baseline responses obtained during the period of medication withdrawal. These results suggest that one role of retinal dopamine may be maintenance of normal retinal responsiveness to flash stimuli.

Chronic eyelid closure and its effect upon the human cone and rod electroretinogram.

The human rod and cone systems have different spectral and adaptive sensitivities. Ganzfeld electroretinogram responses show that chronic eyelid closure, such as extensive symblepharon, can lead to dark-adaptation of the rods but simultaneously permit light-adaptation of the cones of the same eye. This effect is due to the red-filtering properties of the closed eyelid and the differential sensitivity of the two photoreceptor systems to the long wavelengths.

Attenuating actions of diazepam on the photomyoclonic reflex.

The photomyoclonic reflex (PMR), consisting of a one- or two-component blink reflex associated with the flash electroretinogram (ERG), is sensitive to the acute effect of intravenously administered diazepam. In the 29% (two of seven) of normal volunteers who had a PMR, diazepam reduced it to a nonobservable level. Diazepam also had a significant attenuating effect on the a- and b-waves of the ERG; the magnitude of attenuation in normal volunteers, however, probably would not alter a clinical diagnosis based on ERG. These two findings together predict that individuals known to have a marked PMR may have the diagnostic risk associated with these specious artifacts reduced by receiving diazepam before clinical ERG studies are begun.

The effect of metoclopramide on the Ganzfeld electroretinogram.

Antecedent light flashes enhance the amplitude of the electroretinogram (ERG) oscillatory potentials, but do not modify other ERG responses nor dark-adaptation sensory thresholds. Metoclopramide infusion (i.v.) has a generally attenuating effect on the ERG, which is more evident under conditions of dark- than light-adaptation. Metoclopramide decreases the peak amplitude of the rod b-wave and the dark-adapted cone b-wave in a similar manner; it also significantly increases the implicit time of the rod b-wave, but not of the dark-adapted cone b-wave. In addition metoclopramide reverses the enhancement of the oscillatory potentials by the antecedent light flashes.

Temporary loss of foveal contrast sensitivity associated with panretinal photocoagulation.

Snellen visual acuity and spatial contrast sensitivity measurements were used to monitor changes in foveal vision in two patients undergoing argon laser panretinal photocoagulation (PRP) in both eyes for proliferative diabetic retinopathy. Foveal edema developed in one of the four eyes. The remaining three eyes showed no signs of foveal edema, but developed temporary losses in high spatial frequency contrast sensitivity during the closely spaced PRP treatments. Since Snellen visual acuity remained stable at the prelaser level, these results indicate the need for more sensitive measures of visual resolution to monitor foveal integrity in patients undergoing PRP.

Thigmomorphogenesis: field and laboratory studies of Abies fraseri in response to wind or mechanical perturbation.

Field- and greenhouse-grown Abies fraseri (Pursh) Poir. (Fraser fir) were analyzed for wind- or mechanically-induced flexure changes. These changes included inhibition of stem and needle elongation, reinforcement of branch bases around the stem, and increased radial growth in the direction of the mechanical perturbation (MP). Mature trees exposed to high wind conditions were severely flag-formed. These modified tree crowns had a lower drag than crowns of non-flag formed trees in wind-tunnel tests. In both field-grown and greenhouse-grown A. fraseri, MP induced a decrease in flexibility and increased elasticity of the stems. The increased radial growth of the stems overrode the increase in elasticity, resulting in the overall decrease in flexibility. The increase in radial growth caused by wind or mechanical flexure was due to greater cell divisions of the vascular cambium, resulting in increased numbers of tracheids. The decrease in stem elongation in these trees was due, at least in part, to a decrease in tracheid length. The potential biological and mechanical significance of these induced growth changes in trees are addressed. The data support the thigmomorphogenetic theory, which states that plants respond to wind and other mechanical perturbations in a way that is favorable to the plant for continued survival in windy environments.

Thigmomorphogenesis: anatomical, morphological and mechanical analysis of genetically different sibs of Pinus taeda in response to mechanical perturbation.

Twenty-three open pollinated families (half-sibs) and four controlled pollinated families (full-sibs) of Pinus taeda L. (loblolly pine) were grown in a greenhouse and analyzed for changes induced by mechanical perturbation (MP). These changes included inhibition of stem and needle elongation, bracing of branch nodes, and increased radial growth in the direction of the MP. Inhibition of stem elongation was the least variable feature measured. Leaf extension and stem diameter were highly variable between half-sibs. MP induced increased drag in greenhouse grown P. taeda in wind-tunnel tests. In P. taeda, MP induced decreased flexibility and increased elasticity and plasticity of the stem. The increased radial growth of the stems overrode the increase in elasticity, resulting in an overall decrease in flexibility. MP trees had a higher rupture point than non-MP controls. Increased radial growth is a result of more rapid cell divisions of the vascular cambium, resulting in increased numbers of tracheids. The decreased leader growth is partly due to a decreased tracheid length in response to MP.

Thigmomorphogenesis: the role of ethylene in the response of Pinus taeda and Abies fraseri to mechanical perturbation.

Ethylene production was monitored for 48 h in two half-sibs of Pinus taeda L. grown in the greenhouse and given mechanical perturbation (MP) by flexing; and for 22 h in Abies fraseri (Pursh) Poir. grown in the field and exposed to wind-mediated MP. Both species produced a peak of ethylene 18 h after MP. Seedlings of P. taeda exposed to MP for the duration of the growing season (preconditioned) produced less ethylene compared to non-MP controls, with a peak production at 8 h. One half-sib which responded to MP by an increase in radial growth produced 16 times more ethylene than another half-sib which had no significant change in radial growth. Preconditioned A. fraseri produced no significant quantities of ethylene after MP. The production of wound ethylene appears to be different from MP-induced ethylene. When an ethylene-generating solution was applied to P. taeda seedlings, it mimicked many of the morphological and mechanical characteristics of MP seedlings. The putative role of ethylene in the thigmomorphogenetic response is addressed.

Abnormal retinal function associated with fenretinide, a synthetic retinoid.

Five patients with basal cell carcinoma received fenretinide. Two patients while receiving the drug had evidence of abnormal rod photoreceptor function that reversed rapidly on cessation of therapy. We speculate that fenretinide may interfere with the binding of vitamin A to opsin or with the transport of vitamin A.

A pea mutant for the study of hydrotropism in roots.

Plant roots grow in the direction of increasing soil moisture, but studies of hydrotropism have always been difficult to interpret because of the effect of gravity. In this study it was found that roots of the mutant pea ;Ageotropum' are neither gravitropic nor phototropic, but do respond tropically to a moisture gradient, making them an ideal subject for the study of hydrotropism. When the root caps were removed, elongation was not affected but hydrotropism was blocked, suggesting that the site of sensory perception resides in the root cap.

Bone measurement by enhanced contrast image analysis: ovariectomized and intact Macaca fascicularis as a model for human postmenopausal osteoporosis.

This paper presents an image enhancement and analysis system (DARWIN) based on an inexpensive microcomputer and applies the system to two bone morphometry problems relevant to postmenopausal osteoporosis. Using ovariectomized and intact female Macaca fascicularis as a model, we examined the radiodensity of the sixth lumbar vertebra and the cross-section area of the right femur. Significantly lower bone density was observed in the vertebral segments of the ovariectomized animals. No significant differences were observed in comparisons of the femoral cross sections. The reduction in radiographic density of the ovariectomized animals' vertebrae is similar to that observed in postmenopausal women, supporting the use of female cynomolgus macaques as models of bone loss in postmenopausal osteoporosis.