Biology of azospirillum-sugarcane association: enhancement of nitrogenase activity

Azospirillum brasilense was reisolated from associations with callus tissue cultures of sugarcane and compared with stock cultures of the inoculated bacterium and related strains. Although the reisolate had a growth rate similar to stock cultures, it exhibited a severalfold increase in maximum specific activity of nitrogenase. The reisolate and the parent culture had similar ultrastructure. The general ultrastructure of Azospirillum is described. The bacterium was capsulated when grown on nitrogen-free nutrient agar plates and on callus, but was not capsulated when growing in a subsurface zone in N-free semisolid nutrient agar, except rarely in aging cultures. Capsulation may be a protective mechanism against unfavorable pO(2) under dinitrogen-fixing conditions. Pleomorphism occurred in capsulated forms, and the ultrastructure of these forms is described.

Efficacy of electrotactile vestibular substitution in patients with bilateral vestibular and central balance loss

Patients with bilateral vestibular loss (BVL) of both central and peripheral origin experience multiple problems with balance and posture control, movement, and abnormal gait.Wicab, Inc. has developed the BrainPort balance device to transmit head position/orientation information normally provided by the vestibular system to the brain through a substitute sensory channel: electrotactile stimulation of the tongue. Head-orientation data (artificially sensed) serves as the input signal for the BrainPort balance device to control the movement of a small pattern of stimulation on the tongue that relates to head position in real-time. With training, the brain learns to appropriately interpret the information from the device and utilize it to function as it would with data from a normal-functioning natural sense. Ina total of 40 subjects trained with the BrainPort, 18 have been tested using standardized quantitative measurements of the treatment effects. A specialized set of exercises, testing, and training procedures has been developed that may serve as the course of intensive physical therapy with the BrainPort balance device. Our results demonstrate consistent positive and statistically significant balance rehabilitation effects independent of aging and etiology of balance deficit.

Efficacy of electrotactile vestibular substitution in patients with peripheral and central vestibular loss

Vestibular dysfunction of either central or peripheral origin can significantly affect balance, posture, and gait. We conducted a pilot study to test the effectiveness of training with the BrainPort balance device in subjects with a balance dysfunction due to peripheral or central vestibular loss. The BrainPort balance device transmits information about the patient's head position via electrotactile stimulation of the tongue. Head position data is sensed by an accelerometer and displayed on the tongue as a pattern of stimulation. This pattern of stimulation moves forward, backward, and laterally on the tongue in direct response to head movements. Users of the device were trained to use this stimulation to adjust their position in order to maintain their balance. Twenty-eight subjects with peripheral or central vestibular loss were trained with the BrainPort balance device and tested using the following standardized quantitative measurements of the treatment effects: Computerized Dynamic Posturography (CDP) using the Sensory Organization Test (SOT), Dynamic Gait Index (DGI), Activities-specific Balance Confidence Scale (ABC), and Dizziness Handicap Inventory (DHI). All subjects had chronic balance problems and all but one had previously participated in vestibular rehabilitation therapy. The scores on the clinical tests upon entry into the study were compared to their scores following training with the BrainPort balance device. Our results exhibit consistent positive and statistically significant improvements in balance, posture and gait. These results exceed what could normally be achieved in three to five days of traditional balance training alone. Since this was not a controlled study, we are unable to distinguish the degree to which these improvements are attributable to training with the BrainPort balance device versus the balance exercises performed by all subjects as a part of the BrainPort training sessions. Nonetheless, after training with the BrainPort balance device, all subjects demonstrated significant improvements in performance beyond what might be expected from conventional vestibular rehabilitation therapy.

Severe Corneal Toxicity After Topical Fluoroquinolone Therapy

PURPOSE

To describe 2 cases of sterile corneal ulcers that persisted after several weeks of therapy with topical moxifloxacin 0.5% but that resolved when antibiotic therapy was changed.

METHODS

Small case series.

RESULTS

Both cases presented here describe corneal ulcers that persisted and showed signs of worsening during weeks of frequent topical dosing with moxifloxacin. Descemet folds and an atypically large amount of stromal edema were present in both cases, and there appeared to be possible endothelial dysfunction as well. There was no sign of bacterial, viral, or fungal infection in either case. In both cases, healing began a few days after moxifloxacin was discontinued, and topical gatifloxacin and corticosteroids were initiated.

CONCLUSION

These cases suggest that moxifloxacin may interfere with the healing of corneal ulcers.

The afferent neural response to electrotactile stimuli: preliminary results

We recorded action potentials from three RA fibers innervating primate fingerpad, while applying electrotactile (electrocutaneous) stimulation. Negative pulses required 1.3-1.5 times more current than positive ones for entrainment. The strength-duration time constant was approximately 151 micros. Suprathreshold sinusoidal vibration synchronized to 30-Hz electrotactile pulses changed the electrotactile entrainment current slightly, indicating a possible electrical-mechanical transduction interaction.

Form perception with a 49-point electrotactile stimulus array on the tongue: a technical note

Form perception with the tongue was studied with a 49-point electrotactile array. Five sighted adult human subjects (3M/2F) each received 4 blocks of 12 tactile patterns, approximations of circles, squares, and vertex-up equilateral triangles, sized to 4x4, 5x5, 6x6, and 7x7 electrode arrays. Perception with electrical stimulation of the tongue is better than with fingertip electrotactile stimulation, and the tongue requires 3% (5-15 V) of the voltage. The mean current for tongue subjects was 1.612 mA. Tongue shape recognition performance across all sizes was 79.8%. The approximate dimensions of the electrotactile array and the dimensions of compartments built into dental retainers have been determined. The goal is to develop a practical, cosmetically acceptable, wireless system for blind persons, with a miniature TV camera, microelectronics, and FM transmitter built into a pair of glasses, and the electrotactile array in a dental orthodontic retainer.

Retrospective analysis of a novel method of transscleral suture fixation for posterior-chamber intraocular lens implantation in the absence of capsular support

PURPOSE

To determine the safety and efficacy of an alternative method for transscleral fixation of a secondary posterior-chamber intraocular lens (pcIOL) during penetrating keratoplasty.

METHODS

Eighty-nine eyes that underwent secondary pcIOL implantation by using a modified transscleral suture-fixation technique during penetrating keratoplasty were retrospectively evaluated. The surgical technique used suture fixation to the surface of the sclera 5 mm posterior to the limbus, with the knot buried beneath Tenon's capsule and conjunctiva. Patient records were reviewed for postoperative complications, including suture erosion, pcIOL subluxation, vitreous hemorrhage, and retinal detachment. Mean follow-up was 24.4 months, with a range of 4-68 months.

RESULTS

All eyes had successful fixation of their pcIOL immediately after surgery. Three (3.3%) eyes had graft failure. Six (6.7%) of 89 eyes showed evidence of suture erosion or partial exposure. Postoperative suture breakage occurred in two (2.2%) eyes. Posterior-segment complications included retinal detachment in one (1.1%) eye, vitreous hemorrhage in one (1.1%) eye, and limited choroidal hemorrhage in two (2.2%) eyes. Median visual acuity at 1-year follow-up was 20/70 (range, 20/25 to light perception).

CONCLUSION

This transscleral fixation technique provides a straightforward alternative to previously described techniques. Suture erosion, IOL dislocation, and posterior-segment complications occurred at relatively low rates compared with other pcIOL implantation techniques.

Bilateral monocular diplopia associated with lid position during near work

PURPOSE

To describe a common pattern of topographic changes and clinical signs of six patients presenting with a complaint of monocular diplopia after reading and to investigate the cause of this topographic disturbance.

METHODS

PATIENT POPULATION

Subject group of six patients with monocular diplopia complaints after reading and 20 patients without such complaints. Examinations performed before and after a reading period of 30 min: videokeratoscopic examination, red reflex examination, position of the lids in primary gaze and in reading position.

DATA ANALYSIS

inspection of keratoscopic rings, qualitative analysis of topography maps, comparison of SAI and SRI of control and subject groups before and after reading, comparison of lid position of control and subject group.

RESULTS

Half of the subject group and none of the control group developed subtle ring distortions of keratoscopic rings. SAI and SRI values increased significantly in the subject group compared with the control group (p = 0.02 and p < 0.001, respectively) corresponding to the development of a focal distortion in the entrance pupil of the videokeratoscopic image. Each subject developed a horizontal band on red reflex located at the superior, middle, or inferior aspect of the pupil after near work. Two controls developed faint bands in the red reflex outside the entrance pupil. The interpalpebral fissure in down gaze was narrower in the subject group compared with the control group (p = 0.001).

CONCLUSIONS

Some individuals may develop monocular diplopia after reading. We hypothesize that during near work these corneal topographic alterations occur primarily related to the position of the lids and tear film interaction with the corneal surface.

Cavernous hemangioma of the retina, cutaneous angiomas, and intracranial vascular lesion by computed tomography and nuclear magnetic resonance imaging

In a 32-year-old man with a right-sided retinal cavernous hemangioma and cutaneous angiomas, computed tomography and nuclear magnetic resonance imaging confirmed the presence of cerebrovascular lesions. This supports the inclusion of cavernous hemangioma of the retina in the established group of neuro-oculo-cutaneous phacomatoses.

Rubella retinopathy and subretinal neovascularization

A case of rubella retinopathy associated with macular scarring from subretinal neovascularization is presented. Ophthalmoscopic findings included diffuse mottling of the retinal pigment epithelium throughout the macula and into the postequatorial areas, atrophic "rings" around both optic discs, and a solid white and slightly raised macular cicatrix in the right eye. The patient has been followed for three years; her visual acuity remains at 20/20 and there has been no change in the appearance of her retinae. Rubella retinopathy should be considered in the differential diagnosis of young patients with subretinal neovascularization.

L-arabinose metabolism in Azospirillum brasiliense

An oxidative pathway by which L-arabinose is converted to alpha-ketoglutarate in crude extracts of Azospirillum brasiliense is demonstrated. Specific activities of enzymes involved in the pathway were determined, and several pathway intermediates were identified.

Choroidoretinal vascular anastomoses

Three cases of choroidoretinal anastomosis had unusual etiologic and hemodynamic features. In two cases the anastomoses, one caused by ocular histoplasmosis and one by diabetic maculopathy, shunted retinal venous drainage into the choroid. In the third case, the congenital arterial choroidoretinal anastomosis should probably be termed retinochoroidal arteriovenous anastomosis. Prospective photographic and fluorangiographic studies of these patients suggest that our understanding of many basic features of retinal-choroidal circulatory hemodynamics is incomplete.

Isolation of Azospirullum from diverse geographic regions

We have isolated Azospirillum (Spirullum lipoferum) from roots of grasses of several genera collected from a number of tropical and subtropical-temperate locations. Pure cultures were obtained from a small percentage of samples; no higher percentage was secured from tropical than from other grasses. Acetylene reduction and distinctive growth in N-free soft agar deeps were inadequate to identify this genus, although helpful in initial screening. Fluorescent antibody tests with antiserum against characterized strains were helpful. There is some evidence that this genus of bacteria may be favored in the rhizoplane.

Ophthalmomyiasis interna posterior. Subretinal tracks and intraocular larvae

Only seven cases of identifiable intraocular botfly larva infestation have been reported in North America--five since 1969. Two additional cases, both from the same institution, are documented here. The offending maggot or larva was visible in both instances. The findings in each case were diagnostically and morphologically striking. The characteristic funduscopic finding of subretinal tracks, along with the appearance of the larva--encysted in one patient and free-floating in the other-deserves emphasis, since this condition is not always benign and may not be as rare as previously assumed.

Nitrogen Fixation in Grasses Inoculated with Spirillum lipoferum

Field-grown pearl millet (Pennisetum americanum) and guinea grass (Panicum maximum), lightly fertilized and inoculated with Spirillum lipoferum, produced significantly higher yields of dry matter than did uninoculated controls. Up to 42 and 39 kilograms of nitrogen per hectare were replaced by inoculation for pearl millet and guinea grass, respectively. The data demonstrate that nitrogen fixation by these grass-Spirillum systems is efficient and is achieved at a reasonable energy cost to the plant.