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 the n → + 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.

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.

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.

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.

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.

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.

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.