Experimental upper bound and theoretical expectations for parity-violating neutron spin rotation in 4He

Neutron spin rotation is expected from quark-quark weak interactions in the standard model, which induce weak interactions among nucleons that violate parity. We present the results from an experiment searching for the effect of parity violation via the spin rotation of polarized neutrons in a liquid 4He medium. The value for the neutron spin rotation angle per unit length in 4He, d ϕ / d z = [ + 2.1 ± 8.3 (stat.) - 0.2 + 2.9 (sys.) ] × 10 - 7 rad/m, is consistent with zero. The result agrees with the best current theoretical estimates of the size of nucleon-nucleon weak amplitudes from other experiments and with the expectations from recent theoretical approaches to weak nucleon-nucleon interactions. In this paper we review the theoretical status of parity violation in then → + 4He system and discuss details of the data analysis leading to the quoted result. Analysis tools are presented that quantify systematic uncertainties in this measurement and that are expected to be essential for future measurements.

A slow neutron polarimeter for the measurement of parity-odd neutron rotary power

We present the design, description, calibration procedure, and an analysis of systematic effects for an apparatus designed to measure the rotation of the plane of polarization of a transversely polarized slow neutron beam as it passes through unpolarized matter. This device is the neutron optical equivalent of a crossed polarizer/analyzer pair familiar from light optics. This apparatus has been used to search for parity violation in the interaction of polarized slow neutrons in matter. Given the brightness of existing slow neutron sources, this apparatus is capable of measuring a neutron rotary power of dϕ/dz = 1 × 10(-7) rad/m.

Immediate shrinkage of optociliary shunt vessels after fractionated external beam radiation for meningioma of the optic nerve sheath

Fractionated stereotactic radiation has become the standard treatment of meningioma of the optic nerve sheath. The mechanism responsible for improvement in visual function is unclear, because neuroimaging after treatment usually shows no discernable change in tumor appearance. We report immediate regression of optociliary shunt vessels in a patient after radiation treatment of an optic nerve sheath meningioma. This observation indicates that radiation treatment can cause rapid reduction of optic nerve compression, even without appreciable reduction in the size of the meningioma.

Substance dependence and other psychiatric disorders among drug dependent subjects: race and gender correlates

Persons in drug treatment with drug dependence were interviewed with the NIMH Diagnostic Interview Schedule to ascertain DSM-III-R disorders. Lifetime prevalence rates were 64% for alcohol dependence, 44% for antisocial personality disorder (ASPD), 39% for phobic disorders, 24% for major depression, 12% for dysthymia, 10% for generalized anxiety disorder, 3% for panic disorder, 3% for mania, 3% for obsessive compulsive disorder, 2% for bulimia, 1% for schizophrenia, and 1% for anorexia. When stratified by race and age, significant main effects were seen, but there were no significant interactions except in "any non-substance disorder" and in the mean number of non-substance use disorders. Caucasians had a higher mean number of drug dependence disorders and higher overall rates of "any other" disorder than African-Americans, and Caucasians and males had higher mean numbers of non-substance use disorders than African-Americans and females, respectively. This was related to rates of alcohol, cannabis, and hallucinogen dependence, and ASPD rates that were higher among men than women and higher among Caucasian respondents than African-American for alcohol, cannabis, hallucinogen, opiate and sedative dependence, major depression, dysthymia, and generalized anxiety disorder. In contrast, women had higher rates than men of amphetamine dependence, phobic disorder, major depression, dysthymia, panic disorder, obsessive compulsive disorder, and mania. African-Americans had higher rates than Caucasians of amphetamine, cocaine, and phencyclidine dependence, but for no comorbid disorders were the rates higher among African-Americans than Caucasians. The differences according to gender in rates of disorders among substance dependent persons are consistent with the results of general population surveys, but the differences in rates according to race are in contrast to these same community surveys. Limitations in the utility of the concept of race as a valid category diminish the generalizability of the findings; however, one possible explanation is differential treatment seeking in African-American and Caucasian populations that would result in the differences seen.

Emergence of ocular dominance columns in cat visual cortex by 2 weeks of age

Previous anatomic studies of the geniculocortical projection showed that ocular dominance columns emerge by 3 weeks of age in cat visual cortex, but recent optical imaging experiments have revealed a pattern of physiologic eye dominance by the end of the second week of life. We used two methods to search for an anatomic correlate of this early functional ocular dominance pattern. First, retrograde labeling of lateral geniculate nucleus (LGN) inputs to areas of cortex preferentially activated by one eye showed that the geniculocortical projection was already partially segregated by eye at postnatal day 14 (P14). Second, transneuronal label of geniculocortical afferents in flattened sections of cortex after a tracer injection into one eye showed a periodic pattern at P14 but not at P7. In the classic model for the development of ocular dominance columns, initially overlapping geniculocortical afferents segregate by means of an activity-dependent competitive process. Our data are consistent with this model but suggest that ocular dominance column formation begins between P7 and P14, approximately a week earlier than previously believed. The functional and anatomic data also reveal an early developmental bias toward contralateral eye afferents. This initial developmental bias is not consistent with a strictly Hebbian model for geniculocortical afferent segregation. The emergence of ocular dominance columns before the onset of the critical period for visual deprivation also suggests that the mechanisms for ocular dominance column formation may be partially distinct from those mediating plasticity later in life.

Rapid identification of ocular dominance columns in macaques using cytochrome oxidase, Zif268, and dark-field microscopy

Strabismus induces an abnormal pattern of alternating light and dark columns of cytochrome oxidase (CO) activity in macaque striate cortex. This pattern may arise because visual perception is suppressed in one eye to avoid diplopia. To test whether CO activity is reduced in the ocular dominance columns of the suppressed eye, we performed monocular enucleation to co-label the ocular dominance columns with Zif268 immunohistochemistry in seven exotropic adult Macaca fascicularis. This approach was unsuccessful, for two reasons. First, Zif268 yielded inconsistent labelling, that was usually greater in the enucleated eye's ocular dominance columns, but was sometimes greater in the intact eye's columns. Therefore, Zif268 was not a reliable method for identifying the ocular dominance columns serving each eye. Second, in three control animals we found that a brief survival period following monocular enucleation (needed for Zif268 levels to change) was long enough to alter CO staining. For example, a survival time of only 3 h was sufficient to induce CO columns, indicating that the activity of this enzyme fluctuates more rapidly than realized previously. Independent of these findings, we have also discovered that acute monocular enucleation produces a vivid pattern of ocular dominance columns visible in unstained or CO-stained sections under dark-field illumination. The ocular dominance columns of the acutely enucleated eye appear dark. This was verified by labelling the ocular dominance columns with [3H]proline. Dark-field illumination of the cortex after acute monocular enucleation offers a new, easy method for identifying the ocular dominance columns in macaques.

The cortical representation of shadows cast by retinal blood vessels

PURPOSE

We inquired whether the representation of angioscotomas could be detected in the primary (striate) visual cortex.

METHODS

In 12 normal squirrel monkeys, the ocular fundi were photographed and retinal vascular landmarks were projected onto a tangent screen for calibration. Each animal then underwent monocular enucleation under general anesthesia. Animals were perfused after 8 to 10 days, and flat-mounted sections of striate cortex were processed for the metabolic enzyme cytochrome oxidase (CO).

RESULTS

In each animal, the cortical region corresponding to the blind spot appeared as a 3 x 2 mm oval in the CO staining pattern. It stood out because it received input from only 1 eye. In 9 of 12 animals, the representation of the major retinal vessels was also visible, for the same reason. In our best examples, CO sections showed about 10 thin lines radiating from the blind spot representation. Some could be traced for 15 mm, all the way to the vertical meridian. Vessels only 12 minutes of arc in diameter were represented in the cortex. Each angioscotoma representation in the cortex could be matched with its corresponding retinal vessel in the fundus.

CONCLUSIONS

Our findings show that (1) the visual field map in layer IVc is more precise than indicated by physiological studies, and (2) visual experience must refine the final pattern of geniculocortical projections, given that the retinal vessels can produce a shadow only after birth.

Akinetopsia from nefazodone toxicity

PURPOSE

To investigate two cases of selective impairment of motion perception (akinetopsia) induced by toxicity from the antidepressant nefazodone, a new drug that blocks serotonin reuptake and antagonizes 5-HT2 receptors.

METHODS

Case reports.

RESULTS

A 47-year-old man receiving nefazodone (Serzone; Bristol-Meyers Squibb, New York, N.Y.) (100 mg twice daily), reported a bizarre derangement of motion perception. Moving objects were followed by a trail of multiple "freeze-frame" images, which dissipated promptly when motion ceased. A 48-year-old woman receiving nefazodone (400 mg daily at bedtime) reported a similar phenomenon, with visual trails following moving objects. In both patients, vision returned to normal after the dosage of nefazodone was reduced or eliminated.

CONCLUSIONS

Nefazodone toxicity can result in akinetopsia, characterized by the inability to perceive motion in a normal, smooth fashion; persistence of multiple, strobelike images; and visual trails behind moving objects. In this rare syndrome, stationary elements are perceived normally, indicating that nefazodone causes selective impairment of pathways involved in motion processing in the visual system.

Metabolic mapping of suppression scotomas in striate cortex of macaques with experimental strabismus

Misalignment of the ocular axes induces double vision and rivalry. To prevent these unpleasant sensations, most subjects fixate preferentially with one eye and suppress entirely the deviating eye or else suppress portions of the visual field of either eye. To explore the mechanism of visual suppression, a divergent strabismus (exotropia) was induced in six normal, adult Macaca fascicularis by disinserting the medial rectus muscles. After 4-8 weeks, each animal was chaired to measure its exotropia and to determine its ocular fixation preference. Five of the monkeys developed a clearly dominant eye. It was injected with [(3)H]proline. Alternate sections from flat-mounts of striate cortex were then processed either for autoradiography to label the ocular dominance columns or for cytochrome oxidase (CO) to assess local metabolic activity. Two CO patterns were seen, often in the same cortex. The first consisted of thin dark columns alternating with wide pale columns. This pattern arose from reduced CO activity in the suppressed eye's monocular core zones and both eyes' binocular border strips. The second pattern consisted of thin pale bands from reduced metabolic activity in both eyes' border strips. The thin dark-wide pale CO pattern was more widespread in the three animals with a strong fixation preference. The dark CO columns usually fit in register with the ocular dominance columns of the fixating eye, suggesting that perception was suppressed in the deviating eye. In most animals, however, the correlation switched in peripheral cortex contralateral to the deviating eye, implying local suppression of the fixating eye's temporal retina (beyond 10 degrees), as reported in humans with divergent strabismus. In the two animals with a weak fixation preference, pale border strips were found within the central visual field representation in both hemispheres. This CO pattern was consistent with alternating visual suppression. These experiments provide the first anatomical evidence for changes in cortical metabolism that can be correlated with suppression scotomas in subjects with strabismus.

COVOL: an interactive program for evaluating second virial coefficients from the triaxial shape or dimensions of rigid macromolecules

An interactive program is described for calculating the second virial coefficient contribution to the thermodynamic nonideality of solutions of rigid macromolecules based on their triaxial dimensions. The FORTRAN-77 program, available in precompiled form for the PC, is based on theory for the covolume of triaxial ellipsoid particles [Rallison, J. M., and S.E Harding. (1985). J. Colloid Interface Sci. 103:284-289]. This covolume has the potential to provide a magnitude for the second virial coefficient of macromolecules bearing no net charge. Allowance for a charge-charge contribution is made via an expression based on Debye-Hückel theory and uniform distribution of the net charge over the surface of a sphere with dimensions governed by the Stokes radius of the macromolecule. Ovalbumin, ribonuclease A, and hemoglobin are used as model systems to illustrate application of the COVOL routine.

Monocular core zones and binocular border strips in primate striate cortex revealed by the contrasting effects of enucleation, eyelid suture, and retinal laser lesions on cytochrome oxidase activity

In primate striate cortex, geniculocortical afferents in layer IVc terminate in parallel stripes called ocular dominance columns. We propose that this segregation of ocular inputs generates a related but distinct columnar system of monocular core zones alternating with binocular border strips. Evidence for this functional parcellation was obtained by comparing the effects of enucleation, eyelid suture, and retinal laser lesions on cytochrome oxidase (CO) activity in eight macaques. Enucleation produced a high-contrast pattern of dark and light columns in layer IVc, corresponding precisely to the ocular dominance columns, whereas eyelid suture produced a low-contrast pattern of thin dark columns alternating with wide pale columns. [3H]Proline eye injection showed that the thin dark columns corresponded to the core zones of the open eye's ocular dominance columns. The wide pale columns resulted from loss of CO activity in the sutured eye's core zones and within both eyes' border strips. Loss of CO activity within both eyes' border strips suggested that these regions are binocular. To confirm our findings, we compared different CO patterns in the same cortex by making retinal laser lesions in four animals. They produced a CO pattern tantamount to "focal" enucleation, although contrast was low when laser damage was confined to the outer retina. CO levels in cortical scotomas remained severely depressed for months after retinal lesions, even when the other eye was enucleated. This observation provided little anatomical support for the notion of topographic plasticity after visual deafferentation. In a single human subject with macular degeneration, CO revealed a low-contrast pattern of ocular dominance columns, resembling the pattern in monkeys with laser-induced photoreceptor damage.

Intraocular coccidioidomycosis diagnosed by skin biopsy

OBJECTIVE

To describe ocular findings in 2 patients with disseminated coccidioidomycosis diagnosed by skin biopsy.

METHODS

The clinical and histopathologic findings of the 2 patients were reviewed retrospectively.

RESULTS

One patient had a unilateral, granulomatous iridocyclitis with multiple iris nodules and a large vascularized anterior chamber mass, in the setting of pulmonary, cutaneous, and skeletal infection by Coccidioides immitis. The second patient developed papilledema and multifocal chorioretinitis accompanied by pulmonary, cutaneous, and meningeal C immitis infection. In each case, examination of the skin biopsy specimen revealed C immitis spherules. Treatments included local and systemic amphotericin B and oral fluconazole.

CONCLUSIONS

Although rare, intraocular involvement can occur in the setting of disseminated coccidioidomycosis. A thorough systemic evaluation and biopsy of suspicious skin lesions can aid in the diagnosis.

Effect of early monocular enucleation upon ocular dominance columns and cytochrome oxidase activity in monkey and human visual cortex

We examined cytochrome oxidase (CO) activity in striate cortex of four macaque monkeys after monocular enucleation at ages 1, 1, 5, and 12 weeks. These animal experiments were performed to guide our interpretation of CO patterns in occipital lobe specimens obtained from two children who died several years after monocular enucleation during infancy for tumor. In the macaques, the ocular dominance columns were labelled by injecting [3H]proline into the remaining eye. After enucleation at age 1 week, ocular dominance columns were eliminated in layer IVc(beta), resulting in a uniform pattern of autoradiographic label and CO staining. However, columns could still be seen in wet, unstained sections and with the Liesegang silver stain. Autoradiographs through layers IVc(alpha) and IVa showed residual, shrunken columns belonging to the missing eye, indicating that enucleation has less drastic effects in these layers. In the two human cases, enucleation at age 1 week also resulted in uniform CO staining in layer IVc. In the macaque after enucleation at age 5 weeks, ocular dominance columns belonging to the missing eye were severely narrowed, but still occupied 20% of layer IVc(beta). CO revealed wide, dark columns alternating with thin, pale columns in layer IVc(beta). The CO pattern and the columns labelled by autoradiography matched perfectly. After enucleation at age 12 weeks, only mild shrinkage of ocular dominance columns occurred. Enucleation at ages 1, 5, and 12 weeks did not alter the pattern of thin-pale-thick-pale stripes in V2. The main findings from this study were that (1) CO histochemistry accurately labels the boundaries of columns in layer IVc(beta) of macaque striate cortex after early monocular enucleation, making it a suitable technique for defining the critical period for plasticity of ocular dominance columns in human striate cortex; (2) enucleation causes more severe shrinkage of ocular dominance columns than eyelid suture; (3) early monocular enucleation obliterates ocular dominance columns in layer IVcbeta, but their pattern remains visible in wet sections and with the Liesegang stain; and (4) enucleation does not affect CO staining in V2.

Warning on inaccurate Rosenbaum cards for testing near vision

The Rosenbaum card is the most widely used handheld card for measuring near visual acuity. It was developed by Dr. J. George Rosenbaum of Cleveland, Ohio, for testing vision at the bedside of patients after cataract surgery. Millions of copies of the Rosenbaum card have been distributed free by drug companies or sold by medical supply firms. Most versions of the Rosenbaum card are inaccurate because the numbers are not scaled properly to the Snellen system. This article reviews the history of the Rosenbaum card, briefly summarizes issues raised by near vision testing, and provides standards for the manufacture of Rosenbaum near cards.

Pattern of ocular dominance columns and cytochrome oxidase activity in a macaque monkey with naturally occurring anisometropic amblyopia

Unilateral eyelid suture, a model for amblyopia induced by congenital cataract, produces shrinkage of the deprived eye's ocular dominance columns in the striate cortex. Loss of geniculocortical projections are thought to account for the poor vision in the amblyopic eye. It is uncertain whether ocular dominance columns become shrunken in other forms of amblyopia. We examined the striate cortex in a pigtailed macaque with natural anisometropia discovered at age 5 months. Amblyopia in the left eye was documented at 1 year by behavioral testing. At age 6 years, the left eye was injected with [3H]proline and the striate cortex was processed for autoradiography and cytochrome oxidase (CO). The ocular dominance columns in layer IVc labelled with [3H]proline were normal. CO staining showed a novel pattern of thin dark bands in layer IV. These bands occupied the core zones at the center of the ocular dominance columns. Their appearance resulted from relative loss of CO activity along the borders of the ocular dominance columns, regions specialized for binocular processing. These findings indicate that not all forms of amblyopia are accompanied by shrinkage of ocular dominance columns. The unusual pattern of CO staining in layer IVc reflected a subtle alteration in metabolic activity which may have resulted from impairment of binocular function in anisometropic amblyopia.

Timing of the critical period for plasticity of ocular dominance columns in macaque striate cortex

Visual deprivation induced by monocular eyelid suture, a laboratory model for congenital cataract, results in shrinkage of ocular dominance columns serving the closed eye. We performed monocular suture in macaques at ages 1, 3, 5, 7, and 12 weeks to define the critical period for plasticity of ocular dominance columns. After a minimum survival of 8 months, complete montages of [3H]proline-labeled columns were reconstructed from flat-mounts of striate cortex in both hemispheres. In any given monkey, visual deprivation induced the columns throughout striate cortex (V1) to retract the same distance from their original borders in layer IVcbeta. After deprivation, the widest columns remained in the foveal representation and along the V1/V2 border, where columns are widest in control animals. The narrowest deprived columns belonged to the ipsilateral eye, especially along the horizontal meridian and in the periphery, where columns are narrowest in control animals. At the earliest age that we tested (1 week), visual deprivation reduced the columns to fragments. These fragments always coincided with a cytochrome oxidase patch, or a short string of patches, in the upper layers. More severe column shrinkage occurred in layer IVcbeta (parvo) than layer IVcalpha (magno). The geniculate input to the patches in layer III (konio) appeared normal after deprivation, despite loss of CO activity. Surprisingly, the blind spot representation of the open eye was shrunken by monocular deprivation, although binocular competition is absent in this region. Our principal finding was that eyelid suture at age 1 week caused the most severe column shrinkage. With suture at later ages, the degree of column shrinkage showed a progressive decline. Deprivation commencing at age 12 weeks caused no column shrinkage. These results imply that primate visual cortex is most vulnerable to deprivation during the first weeks of life. Our experiments should provide further impetus for the treatment of children with congenital cataract at the earliest possible age.

Transneuronal retinal input to the primate Edinger-Westphal nucleus

The Edinger-Westphal nucleus of the oculomotor nuclear complex provides preganglionic parasympathetic innervation to the pupil. We labelled its retinal input by transneuronal autoradiography after an eye injection of [3H]proline in the macaque monkey. The primary retinal projection to the pretectum terminated in the ipsilateral and contralateral olivary nuclei. These nuclei were intensely labelled and sharply delimited, with a mean diameter of 590 microm and a rostrocaudal length of 2.52 mm. The caudal half of the olivary nucleus on each side broke into multiple clumps of label. Fragments of label also surrounded each olivary nucleus. The exact pattern of pretectal labelling varied considerably among animals and even from side to side in the same animal. In 5 of 6 monkeys, label from the olivary nucleus reached the Edinger-Westphal nucleus transneuronally. In transverse sections, the Edinger-Westphal label appeared as a circular patch located on either side of the midbrain ventral to the cerebral aqueduct in the central gray matter. It averaged 230 microm in diameter and 610 microm in length. In Nissl-stained sections, the autoradiographic label corresponded to a distinct nucleus comprised of neurons that were smaller than neurons in nearby somatic subdivisions of the oculomotor complex. The mean area of Edinger-Westphal neurons was 295 microm2. Transneuronal retinal input to the Edinger-Westphal nucleus mediating pupillary constriction terminates in a single, well-defined cell group in the midbrain.

Myelin patterns in V1 and V2 of normal and monocularly enucleated monkeys

A pattern of alternating light and dark columns was observed in wet, unstained sections of macaque striate cortex after monocular enucleation. The columns were clearest in layer IV, but could be detected through the full thickness of the cortex. Subsequent processing for cytochrome oxidase (CO) showed that the light columns in wet sections viewed under darkfield illumination matched the ocular dominance columns serving the enucleated eye. These columns labeled preferentially with an antibody to myelin basic protein, suggesting that greater myelin content accounted for their brighter appearance. However, when sections were counterstained with luxol fast blue, Gallyas and Woelcke myelin techniques, the enucleated eye's columns appeared pale. It is unclear why classical myelin stains and myelin basic protein immunohistochemistry yielded opposite results. Discrepant patterns of myelin distribution were also found in normal animals using different myelin stains. Luxol fast blue showed homogeneous staining in layer IVc of macaque striate cortex, but the Gallyas stain revealed a pattern of thin pale bands alternating with wide dark bands, matching the pattern seen with the Liesegang stain. The CO patches in layers II and III fit in register with the wide dark myelin bands. In layers II and III of striate cortex, the Gallyas and luxol fast blue methods both labeled the CO patches. However, in squirrel monkey V2 the Gallyas stain labeled the pale CO stripes, whereas luxol fast blue labeled the dark CO stripes. These results indicate that pattern of myelin staining in visual cortex can vary according to the choice of technique, and may not reflect the true distribution of myelin. Studies of myeloarchitecture should employ a variety of myelin techniques, including examination of unstained sections, to obtain the most accurate picture of cortical myelin content.

Wilbrand's knee of the primate optic chiasm is an artefact of monocular enucleation

PURPOSE

The anterior chiasmal syndrome consists of a temporal hemianopia or complete visual field loss in one eye, plus a superior temporal hemianopia in the other eye. The superior temporal hemianopia in the other eye is thought to result from injury to Wilbrand's Knee of the optic chiasm. Wilbrand's Knee is a loop of decussating fibers which detours into the contralateral optic nerve before entering the optic tract. I studied the organization of fibers in the optic chiasm of monkeys and humans to verify the existence of Wilbrand's Knee and to elucidate further the pattern of visual field loss seen from lesions of the sellar region.

METHODS

The primary optic pathway was labelled in monkeys by injection of [3H] proline into one eye, followed by autoradiography. There were 8 intact Rhesus monkeys and 3 intact squirrel monkeys. In addition, the optic pathway was studied in the Rhesus monkey 6 months and 4 years after monocular enucleation. The optic chiasm was also examined using myelin stains in specimens obtained post-mortem from 3 patients. The patients had lost 1 eye 5 months, 2 years, and 28 years prior to their deaths. Finally, clinical observations were recorded in 3 patients with the anterior chiasmal syndrome.

RESULTS

In normal Rhesus and squirrel monkeys, optic nerve fibers crossed the optic chiasm without entering the contralateral optic nerve. After short-term monocular enucleation, fibers from the normal optic nerve were drawn closer to the entry zone of the degenerating optic nerve, but Wilbrand's Knee was still absent. After long-term enucleation, a typical Wilbrand's Knee was induced to form. In the human, Wilbrand's Knee was absent 5 months after monocular enucleation, but emerged in the two cases involving long-term enucleation, in a fashion analogous to the monkey. The case reports describe 3 patients with variants of the anterior chiasmal syndrome from parasellar tumors.

CONCLUSIONS

Wilbrand's Knee does not exist in the normal primate optic chiasm. It forms gradually over a period of years following monocular enucleation, presumably from shrinkage of the optic chiasm caused by atrophy of fibers from the enucleated eye. Therefore, the superior temporal hemianopia in the "other eye" seen in the anterior chiasmal syndrome cannot be due to compression of Wilbrand's Knee. I propose that it occurs from combined compression of the optic chiasm and one (or both) optic nerves.

The ELLIPS suite of macromolecular conformation algorithms

This paper describes a series of four programmes for the PC based on ellipsoidal representations of macromolecular shape in solution using Universal shape functions, ELLIPS1 is based on simple ellipsoid of revolution models (where two of the three axes of the ellipsoid are fixed equal to each other). If the user types in a value for a shape function from sedimentation or other types of hydrodynamic measurement, it will return a value for the axial ratio of the ellipsoid. ELLIPS2 is based on the more general triaxial ellipsoid with the removal of the restriction of two equal axes. The user enters the three semi-axial dimensions of the molecule or the equivalent two axial ratios and ELLIPS2 returns the value of all the hydrodynamic shape functions. It also works of course for ellipsoids of revolution. ELLIPS3 and ELLIPS4 do the reverse of ELLIPS2, that is they both provide a method for the unique evaluation of the triaxial dimensions or axial ratios of a macromolecule (and without having to guess a value for the so-called "hydration") after entering at least three pieces of hydrodynamic information: ELLIPS3 requires EITHER the intrinsic viscosity with the second virial coefficient (from sedimentation equilibrium, light scattering of osmometry) and the radius of gyration (from light or x-ray scattering) OR the intrinsic viscosity with the concentration dependence term for the sedimentation coefficient and the (harmonic mean) rotational relaxation time from fluorescence depolarisation measurements. ELLIPS4 evaluates the tri-axial shape of a macromolecule from electro-optic decay based Universal shape functions using another Universal shape function as a constraint in the extraction of the decay constants.

Intrinsic variability of ocular dominance column periodicity in normal macaque monkeys

Little is known about intrinsic variation from animal to animal in the periodicity of columnar systems within various regions of the mammalian cerebral cortex. To address this issue, complete mosaics of the ocular dominance columns were reconstructed from flat-mounts of the left and right striate cortex (V1) in six normal adult macaques (Macaca fascicularis). To identify the columns, we enucleated the right eye and subsequently processed striate cortex for cytochrome oxidase (CO) activity. Average column areas for the intact eye and the missing eye were nearly equal, confirming that monocular enucleation in adult macaques produces negligible column shrinkage. The contralateral eye's columns occupied more territory than the ipsilateral eye's columns, even in the central visual field representation (0 degree to 8 degrees), where they predominated by 52 to 48%. The column mosaics showed remarkable variation in periodicity. The number of column pairs along the V1/V2 border ranged from 101 sets in one monkey to 154 sets in another. Average column width along the V1/V2 border ranged between 670 and 395 microns, a nearly twofold difference. The widest columns were found in the foveal representation. This high degree of innate variability should be taken into account when considering the effects of various sensory manipulations (e.g., strabismus, anisometropia), which have been reported to alter the periodicity of ocular dominance columns. We found pronounced intrinsic variation in the width and number of ocular dominance columns in a sample of six M. fascicularis, indicating that the number of hypercolumns within a given cortical area can range widely among normal members of the same species.

Anatomical demonstration of ocular dominance columns in striate cortex of the squirrel monkey

The squirrel monkey is the only primate reported to lack ocular dominance columns. Nothing anomalous about the visual capacity of squirrel monkeys has been found to explain their missing columns, leading to the suggestion that ocular dominance columns might be "an epiphenomenon, not serving any purpose" (Livingstone et al., 1995). Puzzled by the apparent lack of ocular dominance columns in squirrel monkeys, we made eye injections with transneuronal tracers in four normal squirrel monkeys. An irregular mosaic of columns, averaging 225 microns in width, was found throughout striate cortex. They were double-labeled by placing wheat germ agglutinin-horseradish peroxidase into the left eye and [3H]proline into the right eye. The tracers labeled opposite sets of interdigitating columns, proving they represent ocular dominance columns. The columns were much clearer in layer IVc alpha (magno-receiving) than IVc beta (parvo-receiving). In the lateral geniculate body, the parvo laminae showed extensive mixing of ocular inputs, suggesting that increased label spillover contributes to the blurred columns in layer IVc beta. The cytochrome oxidase (CO) patches were organized into distinct rows, but they bore no consistent relationship to the ocular dominance columns. These experiments indicate that ocular dominance columns are less well segregated in squirrel monkeys than macaques, but they are present. This fact is pertinent to a recent study reporting that ocular dominance columns are absent in normal squirrel monkeys, but induced to form by strabismus (Livingstone, 1996).

Pattern of ocular dominance columns in human striate cortex in strabismic amblyopia

Previous experiments in animals have shown that early unilateral eyelid suture, a model of amblyopia induced by cataract, causes shrinkage of ocular dominance columns serving the deprived eye in the striate cortex. It is unknown whether the ocular dominance columns are affected in amblyopia produced by strabismus. We examined specimens of striate cortex obtained postmortem from a 79-year-old woman with a history of amblyopia in her left eye (20/800) since age 2 from accommodative esotropia. Four years prior to her death, she suffered an ischemic infarct of the left optic disc. This injury to the left optic disc made it possible to label the ocular dominance columns using cytochrome oxidase histochemistry. The pattern of ocular dominance columns was reconstructed throughout most of the right striate cortex. No shrinkage of columns was found. In the left cortex only half the column mosaic was labelled, because the patient had some residual vision in the temporal retina of her left eye. The columns within the labelled portion of the overall mosaic appeared normal. These findings indicate that shrinkage of ocular dominance columns does not occur in humans with amblyopia caused by accommodative esotropia. The ocular dominance columns are probably no longer susceptible to shrinkage at the age when most children with this condition begin to develop amblyopia.

Central retinal artery occlusion after manipulation of the neck by a chiropractor

PURPOSE

To document a case of central retinal artery occlusion after chiropractic treatment.

METHODS

An 87-year-old man suffered a central retinal artery occlusion immediately after chiropractic neck manipulation.

RESULTS

A magnetic resonance angiogram showed an atherosclerotic plaque in the ipsilateral carotid artery, which probably shed emboli during cervical joint mobilization.

CONCLUSION

The carotid arteries should be approached carefully in patients with known or suspected atherosclerotic disease of the carotid arteries.

An adult-like pattern of ocular dominance columns in striate cortex of newborn monkeys prior to visual experience

In macaque monkeys, the geniculocortical afferents serving each eye segregate in layer IVc of striate cortex during early life into a pattern of alternating inputs called ocular dominance columns. It has been disputed whether visual experience is necessary for the formation of ocular dominance columns. To settle this issue, fetal monkeys were delivered prematurely by Caesarean section at embryonic day 157 (E157), 8 d before the end of normal gestation. To avoid light exposure, the Caesarean section and all subsequent feedings and procedures were done in absolute darkness, using infrared night-vision goggles. Tritiated proline was injected into the right eye 1 d after delivery (E158). One week later at postnatal age 0 (P0), the equivalent of a full-term pregnancy (E165/P0), alternate sections of unfolded and flattened visual cortex were prepared for autoradiography or cytochrome oxidase (CO). All three newborns studied at E165/P0 had well segregated ocular dominance columns organized into the characteristic mosaic present in adults. In the upper layers, a mature pattern of CO patches (also known as blobs or puffs) was visible, aligned with the ocular dominance columns in layer IVc. Every other row of patches in layers II, III was labeled by [3H]proline. In V2, a distinct system of alternating thick-pale-thin-pale CO stripes was present. These findings indicate that stimulation of the retina by light is not necessary for the development of columnar systems in the visual cortex. Ocular dominance columns, patches, and V2 stripes all are well formed before visual experience. Even the thalamic input to the patches in the upper layers of striate cortex is segregated by eye in newborns.

Salvage of vision after hypotension-induced ischemic optic neuropathy

No effective treatment has been established for nonarteritic anterior ischemic optic neuropathy. Although most cases occur spontaneously, acute hypotension plays a clear role in a subset of patients. We examined three patients with severe visual loss from ischemic optic neuropathy induced by hypotension. The first patient developed anterior ischemic optic neuropathy after excessively rapid correction of malignant hypertension. In the second patient, anterior ischemic optic neuropathy occurred after an episode of orthostatic hypotension from systemic hypovolemia. The third patient developed anterior ischemic optic neuropathy after becoming hypotensive during a routine hemodialysis session. Measures were undertaken immediately to reverse the hypotension in all three patients. This intervention resulted in partial recovery of vision in each patient.

Neurovisual findings in the syndrome of spontaneous intracranial hypotension from dural cerebrospinal fluid leak

BACKGROUND

Spontaneous intracranial hypotension has been considered a rare clinical entity, with less than 75 cases reported in the medical literature. With the advent of magnetic resonance imaging (MRI), spontaneous intracranial hypotension currently is being recognized more frequently. The authors report the neurovisual manifestations of this disorder in a consecutive series of three patients.

METHODS

Each patient underwent clinical examination, computerized visual field testing, and MRI. After treatment, each patient was re-examined, and MRI was repeated.

RESULTS

Two patients had transient visual obscurations and unusual binasal visual field defects on automated perimetry. A third patient had diplopia from an abducens nerve paresis. After treatment of spontaneous intracranial hypotension, these findings improved or resolved.

CONCLUSIONS

This case series, and a review of previously reported cases, indicates that neurovisual problems are common in patients with spontaneous intracranial hypotension. Findings may include diplopia from sixth nerve paresis, transient visual obscurations, blurred vision, visual field defects, photophobia, and nystagmus.

Amblyopia induced by anisometropia without shrinkage of ocular dominance columns in human striate cortex

Amblyopia can be induced by opacity of the ocular media (e.g., cataract), misalignment of the ocular axes (strabismus), or unequal refractive error in the eyes (anisometropia). Experiments in monkeys have shown that early monocular eyelid suture, a model of amblyopia caused by cataract, results in shrinkage of the eye's ocular dominance columns in striate cortex. This reduction of the geniculocortical projection from the deprived eye has been thought to explain in part the mechanism of amblyopia. We labeled the ocular dominance columns in monkeys with amblyopia by using cytochrome oxidase histochemistry. In animals rendered amblyopic by early unilateral eyelid suture, no pattern of cytochrome oxidase activity appeared in layer IVc. Outside layer IVc, alternating rows of light and dark patches were present; the pale patches fit in register with the shrunken ocular dominance columns of the deprived eye, which were labeled by autoradiography. Subsequent removal of one eye caused a striking cytochrome oxidase pattern to emerge in layer IVc that correlated precisely with the shrunken (deprived eye) and expanded (normal eye) ocular dominance columns. This correlation was shown by injecting one eye with [3H]proline. It has remained unsettled whether other forms of amblyopia are accompanied by shrinkage of ocular dominance columns. To address this issue, in an analogous clinical case, we examined the pattern of cytochrome oxidase activity in a human subject with a history of anisometropic amblyopia who suffered a lesion of one optic nerve shortly before death. The ocular dominance columns were normal in width, indicating that some forms of amblyopia occur without shrinkage of ocular dominance columns.

Free air in the cavernous sinus as an incidental finding

Free air within the cavernous sinus was discovered incidentally on a computed tomographic (CT) scan. We suggest that air bubbles were introduced inadvertently when contrast material was injected just prior to CT scanning. On a repeat CT scan 16 days later, the air had disappeared.

Sudden visual field constriction associated with optic disc drusen

We report two patients with optic disc drusen who suffered sudden, concentric constriction of the visual field. Visual acuity remained normal. The involved discs showed no swelling, hemorrhage, or other evidence of anterior ischemic optic neuropathy. We are unable to explain the mechanism or the pattern of visual field loss in these unusual cases.

Decompression of the optic nerve sheath for vision-threatening papilledema caused by dural sinus occlusion

Obstruction of the dural sinuses produces a clinical syndrome that resembles pseudotumor cerebri. In these patients, unremitting papilledema can cause blindness. We performed decompression of the optic nerve sheath in four patients who had occlusion of the dural sinuses. The operation achieved rapid relief of papilledema and recovery of vision. In three patients, fenestration of the nerve sheath of only one eye resulted in resolution of papilledema in both eyes. The procedure appears to relieve papilledema by filtering small quantities of cerebrospinal fluid into the orbit. It did not lower cerebrospinal fluid pressure in three patients who underwent lumbar puncture after surgery. Optic nerve sheath decompression is an effective operation for salvage of vision in patients with obstruction of the dural sinuses.

Wolfram syndrome: evidence of a diffuse neurodegenerative disease by magnetic resonance imaging

Wolfram syndrome is an autosomal recessive disorder beginning in childhood that consists of four cardinal features: optic atrophy, diabetes mellitus, diabetes insipidus, and neurosensory hearing loss. Aside from these features, the clinical picture is highly variable and may include other neurologic abnormalities such as ataxia, nystagmus, mental retardation, and seizures. We present two unrelated patients with Wolfram syndrome, both of whom had the four cardinal features and several other neurologic abnormalities. MRIs showed widespread atrophic changes throughout the brain, some of which correlated with the major neurologic features of the syndrome.

Hemianopsia from occipital lobe abscess after dental care

We treated four patients who developed a homonymous hemianopsia from a bacterial abscess in the occipital lobe of the brain. All four patients were treated successfully by surgical drainage of the abscess and administration of parenteral antibiotics for at least six weeks. Despite cure of the brain abscess, each patient was left with a permanent residual homonymous visual field defect. Cultures from the abscess fluid in three of the four patients grew oral flora. Moreover, each patient had a history of dental care two to four weeks before the onset of visual symptoms. A history of recent dental treatment in a patient with a new hemianoptic field defect should alert the ophthalmologist to the possibility of a bacterial abscess in the occipital lobe.