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Biomedical subjects

J Wallman

Publications and source records attributed to J Wallman.

At least 55 records · Page 3Linked to original sources
PubMed1989

Multiple distinct intracranial tumors: association of pinealoma and craniopharyngioma. Case report.

We report the case of a patient with multiple primary brain neoplasms. A pinealoma was treated with radiotherapy and surgical resection in 1983. In 1987, a craniopharyngioma was resected surgically. Various possible determinants of multiple brain tumors have been described in the literature and are discussed. The possibility of an unknown underlying pathologic mechanism predisposing to multiple malignancies must be considered, but we are unable to conclude that this particular occurrence is more than a random chance finding.

Adult↗
PubMed1989

Covalent binding to alpha-macroglobulins of a protein with free SH groups produced by activated B cells: blocking by D-penicillamine and gold compounds.

alpha 2-Macroglobulin (alpha 2M) complexed with proteinases or modified by the action of amines has been shown to affect immune responses in vitro, though as yet the mechanisms are poorly understood. Supernates from rabbit lymphoid cells cultured in medium with normal rabbit serum and 35S-methionine (or 14C-leucine) were found to contain intensely radiolabeled alpha-macroglobulins (alpha M) (alpha 1 and alpha 2) on electrophoresis. When human alpha 2 M, instead of rabbit serum, was added to cultures, it also appeared radiolabeled, suggesting that lymphocyte-produced proteins (LyP) formed complexes with serum alpha M. These alpha M-associated LyP were produced in greater quantity when lymphocytes were cultured in the presence of mitogens; they were not produced by cells cultured in the presence of cycloheximide; they were produced primarily by B cells rather than T cells or macrophages. Pretreatment of serum or alpha M with methylamine, enhanced rather than inhibited the formation of LyP-alpha M complexes, a finding which is contrary to that expected if the LyP were a proteinase. Since this methylamine treatment of alpha M also results in the generation of free SH groups from the internal thioester bonds of alpha M, the formation of disulfide bonds between LyP and alpha M was considered. Indeed, (a) the LyP-alpha M complex formation was inhibited by N-ethylmaleimide, aurothiomalate, sodium aurothioglucose or D-penicillamine; (b) blocking the SH groups with NEM, of either culture fluid supernates or serum, had an inhibitory effect on the formation of these complexes; (c) the LyP-alpha M complexes were dissociated by sodium dodecyl sulfate (SDS) only after their reduction with 2-mercaptoethanol (2-ME). Thus, a disulfide bond was formed between alpha M and LyP with free SH groups (SH-LyP). Molecular sieving by high performance liquid chromatography (HPLC) of the serum-free radiolabeled supernates indicated that SH-LyP eluted at a position corresponding to a polypeptide of mol. wt of about 22,000. However, SDS-PAGE of the 22,000 mol. wt HPLC fraction showed that the major protein was approximately mol. wt 11,000 under both reducing and non-reducing conditions. In addition, the SH-LyP reduced by 2-ME from its binding site on alpha 2M had a mol. wt of about 11,000 in SDS-PAGE, suggesting that it was a non-covalent homodimer of mol. wt 11,000 polypeptides. We suggest that alpha 2M as well as SH-LyP may affect the immune system by functioning as SH-reactive agents.

Animals↗
PubMed1988

Response properties of dorsolateral pontine units during smooth pursuit in the rhesus macaque.

1. The anatomical connections of the dorsolateral pontine nucleus (DLPN) implicate it in the production of smooth-pursuit eye movements. It receives inputs from cortical structures believed to be involved in visual motion processing (middle temporal cortex) or motion execution (posterior parietal cortex) and projects to the flocculus of the cerebellum, which is involved in smooth pursuit. To determine the role of the DLPN in smooth pursuit, we have studied the discharge patterns of 191 DLPN neurons in five monkeys trained to make smooth-pursuit eye movements of a spot moving either across a patterned background or in darkness. 2. Four unit types could be distinguished. Visual units (15%) discharged in response to movement of a large textured pattern, often in a direction-selective fashion but not during smooth pursuit of a spot in the dark. Eye movement neurons (31%) discharged during sinusoidal smooth pursuit in the dark with peak discharge rate either at peak eye position or peak eye velocity, but they showed no response during background movement or during other visual stimulation. These units continued to discharge when the target was extinguished (blanked) briefly, and the monkey continued to make smooth eye movements in the dark. The majority (54%) of our DLPN units discharged during both smooth pursuit in the dark and background movement while the monkey fixated. Blanking the target during smooth pursuit revealed that these units fell into two distinct classes. Visual pursuit units ceased discharging during a blank, suggesting that they had only a visual sensitivity. Pursuit and visual units continued to discharge during the blank, indicating that they had a combined oculomotor and visual sensitivity. 3. Ninety-five percent of the units that discharged during smooth pursuit were direction selective. These units had rather broad directional tuning curves with widths at half height ranging from 65 to 180 degrees. Many preferred directions for DLPN units were observed, although the vertical and near-vertical directions predominated. 4. Most units that responded to large-field background movement were direction selective. During sinusoidal movement of a large-field background, half of them also discharged in relation to stimulus velocity, whereas others did not.

Action Potentials↗
PubMed1987

Local retinal regions control local eye growth and myopia.

In chicks, visual deprivation leads to myopia and enlargement of the vitreous chamber of the eye. When chicks were raised with white translucent occluders over their eyes so that either the nasal half, the temporal half, or all of the retina was visually deprived, the resulting myopia (median = -15 diopters) was limited to the deprived part of the retina, regardless of which half of the retina was visually deprived; the nondeprived part remained nearly emmetropic. Correspondingly, the vitreous chamber was elongated only in the region of the visual deprivation, resulting in eyes with different asymmetric shapes depending on which retinal region was deprived. These results argue for a local regulation of ocular growth that is dependent on vision and suggest a hypothesis to explain the epidemiological association of myopia in humans with large amounts of reading. Because most nonfoveal retinal neurons have large receptive fields, they cannot resolve the individual letters on the printed page; this may lead to their activity being less during reading than during most other forms of visual stimulation. Thus, the impoverished stimulus situation of reading may lead to myopia, as do other types of visual form deprivation.

Animals↗
PubMed1987

Developmental aspects of experimental myopia in chicks: susceptibility, recovery and relation to emmetropization.

Chicks deprived of form-vision in the lateral part of their visual fields become severely myopic largely because of elongation of the vitreous chamber. The myopia mostly affects the visually deprived nasal retina; the nondeprived temporal retina is unaffected. These changes occur most rapidly early in life, being evident then after only 3 days of visual restriction. The susceptibility declines with age, being proportional to the rate of increase of axial length. Recovery from this myopia occurs if the visual restriction is removed during the first 6 weeks of life, as a result of the cessation of elongation of the vitreous chamber. The rate of recovery is directly related to the degree of myopia and inversely related to age. The pattern of changes in refractive status and variability argue for the probable existence of an active mechanism regulating eye growth in a manner dependent on refractive error, thereby producing emmetropization.

Accommodation, Ocular↗
PubMed1987

Changes in corneal curvature during accommodation in chicks.

Evidence is presented for an active corneal component of accommodation in chicks. Using anesthetized chicks, consistent increases in corneal curvature were observed during accommodation produced either by electrical stimulation of the Edinger-Westphal nucleus or by topical application of 0.4% nicotine sulfate to the cornea. Electrical stimulation produced a mean accommodative amplitude of 9.2 diopters (D) and a change in corneal power of 3.9 D whereas nicotine treatment elicited 15.1 D of accommodation and 6.1 D of change in corneal power. The change in corneal power increased proportionately with accommodative amplitude up to about 10 D of total accommodation where the corneal power change appeared to level off at approximately 6 D. This limit to corneal curvature change implies that it plays a proportionately greater role in the lower range of accommodation.

Accommodation, Ocular↗
PubMed1987

Visual deprivation causes myopia in chicks with optic nerve section.

Deprivation of form vision restricted to a region of the retina produces myopia and axial elongation only in that region. We asked whether this control of eye growth by the presence or absence of visual stimuli might take place entirely within the eye. Chicks with neonatal optic nerve section, wearing an occluder that deprived one half of the retina of form vision, had vitreous chamber elongation and myopia both restricted to the deprived region. Chicks with optic nerve section but without occluders had eyes smaller than normal with severe hyperopia. These results suggest that two different mechanisms may control eye growth, one within the eye and the other in the brain.

Animals↗
PubMed1987

Different visual deprivations produce different ametropias and different eye shapes.

To compare the effects on the postnatal development of the eye of both total and partial form deprivation in diurnally reared chicks and of dark-rearing, chicks were reared with occluders covering one eye from hatching for up to 6 weeks. In diurnally reared birds, both total and partial form deprivation resulted in severe axial myopia and increased eye size. These effects were greatest for the eyes of chicks raised with total form deprivation; they had highly curved corneas and very deep anterior and vitreous chambers. In addition, the amount of myopia produced in eyes with total form deprivation was the same at 2 and 6 weeks, whereas eyes with partial form deprivation showed substantial remission even with the occluders left on. The partially deprived eyes developed a striking shape asymmetry: the posterior globe only became enlarged in the deprived region of the retina. The eyes of dark-reared chicks, regardless of whether or not an occluder was worn, also were enlarged but were hyperopic owing to a severe flattening of the cornea. This hyperopia was slow to develop compared to the myopia produced in the diurnally reared visually restricted eyes. Finally, the shape of the posterior globe of these hyperopic eyes was no different from that of normal eyes.

Animals↗
PubMed1986

Nasal airway obstruction: CT assessment.

Twenty-one cases of nasal airway obstruction were analyzed using computed tomography (CT) at the Children's Hospital in Boston between 1980 and 1984. Seven of these patients had stenosis of the entire nasal passage, two had stenosis of the anterior nasal cavity, and 12 had atresia of the posterior choanae. The spectrum of these abnormalities and the optimum technique for CT scanning are discussed.

Child↗
PubMed1985

Accessory optic system and pretectum of birds: comparisons with those of other vertebrates.

We compare the functional and anatomical organization in birds and other vertebrates of the accessory optic nuclei and of those pretectal nuclei implicated in optokinetic responses. In all vertebrate groups, the neurons in these nuclei respond most strongly to slow large-field visual motion in particular directions; the several nuclei differ in the direction of stimulus motion that evokes the best response. These nuclei are essential for optokinetic nystagmus (OKN) in all species examined; the pretectum is necessary for horizontal OKN and the accessory optic nuclei for OKN in other directions. At least in the accessory optic system of birds, the directional parcellation is not well-developed at hatching and requires visual experience to develop normally. There is evidence that the accessory optic system may play a role in transforming the visual motion signal from retinal coordinates into vestibular or oculomotor coordinates. In regard to anatomical connections, in all vertebrate groups studied, the accessory optic and pretectal nuclei project either directly or indirectly to the cerebellum; in addition, the accessory optic system and pretectum are extensively reciprocally connected. In some groups, but not in others, projections have been discovered from the accessory optic system and pretectum to the extraocular motor nuclei and from the accessory optic system to both the vestibular complex and the interstitial nucleus of Cajal.

Animals↗
PubMed1985

Treatment of craniopharyngiomas in children: 1972-1981.

Between 1972 and 1981, 37 children with craniopharyngioma were cared for at Children's Hospital, Boston. In this paper, the results of treatment with radiation therapy after conservative operations are compared with those following an initial attempt to excise the tumor. Radiation therapy was equally, if not more, effective than attempted excision in controlling subsequent tumor growth. Although this was not a controlled study, the complications of each approach are indicated, and it is inferred that conservative operations combined with radiation therapy offer less risk for psychosocial impairment than does attempted tumor excision when patients are considered as a group. The ultimate effect that either approach might have on quality of life remains to be defined, and therapy must still be individualized to the particular clinical problem.

Child↗
PubMed1985

Directional asymmetries of optokinetic nystagmus: developmental changes and relation to the accessory optic system and to the vestibular system.

To investigate the relation of the directional organization of the accessory optic system (AOS) to that of its principal behavioral output, optokinetic nystagmus (OKN), we measured the eye velocity during OKN in response to 14 directions of stimulus motion, including horizontal, vertical, cyclorotational (rotations about the optic axis), and intermediate directions in both neonatal and older chickens. We found substantial and consistent OKN asymmetries between opposite directions of stimulus motion when the stimuli were viewed monocularly; the asymmetries were largest to combinations of cyclorotational and vertical stimulus motion and to horizontal stimulus motion. The highest gain of OKN in the older animals was in response to two directions of stimulus motion: horizontal temporal-to-nasal and a combination of excyclorotation and downward. In addition, OKN to upward moving stimuli was consistently better than to downward stimuli. The association of high OKN gain in the older animals with the pattern of visual motion produced by head movements exciting the contralateral anterior semicircular canal suggests a possible vestibular organization of the optokinetic system. The response pattern of the newly hatched chickens differed in three ways from that of the older animals: in the non-horizontal stimulus directions the best direction was to upward and excyclorotational stimulus motion; the horizontal asymmetry was somewhat less strong; and the OKN gain to high velocity horizontal stimulus motion was lower. The change in directional pattern of OKN over the first weeks of life appears related to a corresponding change in anatomy of the AOS.

Animals↗
PubMed1985

Functional postnatal changes in avian brain regions responsive to retinal slip: a 2-deoxy-D-glucose study.

The postnatal development of two avian brain areas, the nucleus of the basal optic root (nBOR) and the lentiform nucleus of the mesencephalon (LM), was studied using the 2-deoxy-D-glucose (2-DG) method. Previous studies have shown that these nuclei respond to whole field visual motion, which is used for optokinetic eye movements. In the present study vertical whole field visual motion presented to one eye resulted in the accumulation of 2-DG label in the contralateral nBOR in both hatchlings and 3-week or older chicks. In hatchlings the nBOR was diffusely labeled whether upward or downward motion was used as the test stimulus, whereas in older birds the label was localized within different subdivisions of the nBOR depending on the direction of vertical motion: upward motion resulted in concentration of 2-DG label in the dorsal nBOR, whereas downward motion resulted in label in the ventral nBOR. Horizontal whole field visual motion presented to one eye resulted in 2-DG label in the contralateral LM and in the lateral portion of the contralateral nBOR in animals of both ages. In hatchlings, visual motion in both temporal-to-nasal and nasal-to-temporal directions resulted in labeling of both subdivisions of the LM, LM magnocellularis (LMmc) and LM parvocellularis. In older birds, temporal-to-nasal motion resulted in labeling of only the LMmc, whereas nasal-to-temporal motion produced labeling in both subdivisions. These results strongly suggest that the nBOR and LM continue to develop their response properties postnatally and that different functional units become separated within particular subdivisions of the nuclei. Conceivably, the functional segregation within the nBOR is due to an intrinsic reorganization, whereas functional changes in the LM may be due to the postnatal development of a projection from the telencephalon.

Aging↗
PubMed1985

Conjugate and disjunctive saccades in two avian species with contrasting oculomotor strategies.

We have recorded with the magnetic search coil method the spontaneous saccades of two species of predatory birds, which differ in the relative importance of panoramic and foveal vision. The little eagle (Haliaetus morphnoides) hunts from great heights and has no predators, whereas the tawny frogmouth (Podargus strigoides) hunts from perches near the ground, is preyed upon, and frequently adopts an immobile camouflage posture. We find that both birds spend most of the time with their eyes confined to a small region of gaze, the primary position of gaze; in this position, the visual axes are much more diverged in the frogmouth than in the eagle, thereby giving it a larger total field of view at the expense of its binocular field. Both species, however, can align their visual axes, thereby gaining a binocular view of targets in the frontal visual field. The eagle makes saccades 10 times as frequently as the frogmouth, and in most of its saccades the eyes move in the same direction, although the eye movements are generally not conjugate; in most frogmouth saccades, on the other hand, the eyes move in opposite directions. We discuss these phenomena in terms of their saccadic mechanisms and their possible adaptiveness. We also report two incidental observations: in certain circumstances, the frogmouth shows no sign of having a vestibulo-ocular reflex, and the eagle, although the quintessential foveate animal, shows extreme directional asymmetries of monocularly evoked optokinetic nystagmus.

Animals↗
PubMed1983

Paired receiver operating characteristic curves and the effect of history on radiographic interpretation. CT of the head as a case study.

The use of a statistical technique for paired comparisons using receiver operating characteristic (ROC) curves is illustrated by studying the extent to which clinical history altered the interpretation of computed tomographic (CT) examinations of the head. Eighty-nine CT examinations of the head were presented in random order to four readers, first with minimum history (age and sex) and then several weeks later with complete neurological history as of the time the CT examination had been obtained. Using a paired ROC analysis, a small but significant (p less than .05) improvement was detected for the interpretations in the presence of complete history; for readings without history the average area was 94.4% and for readings with history it was 97.7%.

Brain Diseases↗