A computational model for the overall pattern of ocular dominance.

In layer IV of the primary visual cortex, in both the macaque monkey and the cat, geniculocortical terminals representing the two eyes are segregated into alternating zones known as ocular dominance bands. Viewed tangentially, in the monkey these bands take the form of a series of branching parallel stripes that run roughly perpendicular to the border of striate cortex. In the cat, the overall ocular dominance pattern consists of irregularly branching, beaded bands that exhibit no predominant orientation. If the striking differences in the appearance of these two patterns reflect important differences in the basic rules governing cortical ocular dominance, then this poses a problem for attempts to formulate general principles of visual cortical organization. However, it has been suggested that the differences in the appearance of the ocular dominance patterns in these two species could result simply from known differences in the boundary conditions of their geniculocortical pathways. This article describes the formulation and testing of a single computational model that accurately predicts the quite dissimilar ocular dominance patterns in cats and monkeys. This model also generalizes to predict the different ocular dominance patterns observed in young and old three-eyed frogs, supporting the notion that the overall pattern of ocular dominance is governed by a common set of rules. The significance of these results is discussed in terms of previous models, which have focused largely on local processes underlying the development of ocular dominance segregation. Although the present model is not a developmental one, it does shed some light on potential mechanisms for establishing retinotopy in striate cortex and on possible developmental relationships between the geniculostriate pathway and intrinsic modularity of the striate cortex.     

Plasma amine oxidase activities in Norrie disease patients with an X-chromosomal deletion affecting monoamine oxidase

Summary Two individuals with an X-chromosomal deletion were recently found to lack the genes encoding monoamine oxidase type A (MAO-A) and MAO-B. This abnormality was associated with almost total (90%) reductions in the oxidatively deaminated urinary metabolites of the MAO-A substrate, norepinephrine, and with marked (100-fold) increases in an MAO-B substrate, phenylethylamine, confirming systemic functional consequences of the genetic enzyme deficiency. However, urinary concentrations of the deaminated metabolites of dopamine and serotonin (5-HT) were essentially normal. To investigate other deaminating systems besides MAO-A and MAO-B that might produce these metabolites of dopamine and 5-HT, we examined plasma amine oxidase (AO) activity in these two patients and two additional patients with the same X-chromosomal deletion. Normal plasma AO activity was found in all four Norrie disease-deletion patients, in four patients with classic Norrie disease without a chromosomal deletion, and in family members of patients from both groups. Marked plasma amine metabolite abnormalities and essentially absent platelet MAO-B activity were found in all four Norrie disease-deletion patients, but in none of the other subjects in the two comparison groups. These results indicate that plasma AO is encoded by gene(s) independent of those for MAO-A and MAO-B, and raise the possibility that plasma AO, and perhaps the closely related tissue AO, benzylamine oxidase, as well as other atypical AOs or MAOs encoded independently from MAO-A and MAO-B may contribute to the oxidative deamination of dopamine and 5-HT in humans.     

Acyclovir treatment of herpes simplex encephalitis: experience in a district hospital

Herpes simplex encephalitis may be underdiagnosed in Britain. We report eight patients treated at one hospital over three years. Fever, impaired consciousness or focal neurological signs were seen in all patients at presentation but herpes simplex encephalitis was rarely considered as the initial diagnosis. The electroencephalogram was the only initial investigation that was abnormal in each case and was the most useful test in establishing a clinical diagnosis. The diagnosis was confirmed by laboratory methods in each case. Following acyclovir treatment five patients were able to resume normal activities, one patient has moderate disability and two patients died. Three patients showed clinical evidence of relapse but two improved after further treatment with acyclovir. Herpes simplex encephalitis is a treatable condition and should be considered in all patients presenting with fever and neurological signs. The electroencephalogram is usually abnormal and the changes may be characteristic of the condition.     

The use of blood components in patients with malignancy

Many recent improvements in the management of patients with malignancy would have been impossible without parallel improvements in our ability to support patients through periods of severe bone marrow aplasia produced by the disease or aggressive therapy of the disease. The purpose of this article is to review the use of transfusion of platelets, erythrocytes, and granulocytes in the treatment of these patients.

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Resumen Muchos de los recientes adelantos en el manejo de pacientes con neoplasias malignas habrían sido imposibles sin un desarrollo paralelo en la capacidad de proveer soporte en el curso de severa aplasia de la medula ósea producida por la enfermedad misma o por terapia antineoplásica agresiva. El propósito de este artículo es revisar el uso de las transfusiones de plaquetas, eritrocitos, y granulocitos en el manejo de estos pacientes.

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Résumé De nombreuses améliorations récentes du traitement des malades atteints d'une affection maligne auraient été impossibles sans des améliorations parallèles du traitement des épisodes d'aplasie médullaire grave produits par l'affection elle-même ou par les agents thérapeutiques agressifs employés pour les traiter. Le but de l'article est de passer en revue l'emploi respectif des plaquettes, des érythrocytes et des granulocytes pour traiter ces malades.

     

The agreement and repeatability of tear meniscus height measurement methods.

PURPOSE: This study investigated the agreement and repeatability of five techniques of measuring tear meniscus height (TMH). METHODS: Pairs of TMH measurements were obtained from one eye of 25 normal subjects with five techniques: optical coherence tomography in cross-section (OCT) and optical pachymetry in cross-section (PACH), without fluorescein; and 5 minutes after the instillation of fluorescein, optical pachymetry en-face (SL-F) and in cross-section (SL-X), and video capture en-face (VC). These 10 measurements were taken on different days within a period of 21 days. Additionally, immediately successive replicates were taken at the first visit when VC was used, allowing for the separation of technique repeatability from true day-to-day variation in TMH. RESULTS: Ninety-five percent confidence intervals for the mean TMH and 95% repeatability coefficients for repeated testing on separate occasions were: 0.25 to 0.29 mm, 0.14 mm--OCT, 0.30 to 0.36 mm, 0.13 mm--PACH, 0.27 to 0.34 mm, 0.092 mm--SL-F, 0.35 to 0.41 mm, 0.19 mm--SL-X, and 0.30 to 0.38 mm, 0.088 mm--VC. Reported repeatability coefficients are averages because, despite a relatively narrow experimental range, the measurements of low TMH were generally more repeatable than those of large TMH. Ninety-five percent limits of agreement were wide for all pairwise comparisons and included zero, indicating that the methods used in this study are interchangeable when taking single recordings, at least on subjects without dry eye. CONCLUSIONS: The average TMH of the five techniques was similar, although OCT and SL-X tended to record lower and higher values, respectively. However, their agreement for single recordings was poor, an inevitable consequence of the low intertest repeatability found for all methods. A much improved repeatability for immediate replicates indicated that this, in turn, was principally caused by a large day-to-day variation in TMH rather than measurement error.     

Polycythaemia and neuroblastoma

The treatment of primary proliferative polycythaemia (polycythaemia rubra vera) may include radioactive phosphorus (P32) in conjunction with venesection. Acute leukaemia or carcinoma can be associated with the use of P32. We present a case of primary proliferative polycythaemia treated by repeat venesection together with P32 whose follow-up was complicated by the development of malignant neuroblastoma.     

Characteristics of chloride-dependent incorporation of glutamate into brain membranes argue against a receptor binding site

Although membrane sites from brain, labelled with [3H]glutamate (Glu) under sodium-free conditions, are thought to represent excitatory receptors, certain anomalous characteristics of the kinetics of apparent binding raised the question of whether transport might contribute to this process, prompting a closer examination of it. Hyperosmolar media and low incubation temperatures (4 degrees C) both led to decreases in the apparent specific binding of [3H]glutamate to membranes from the brain of the rat in the presence of chloride. Furthermore, only 15% of the [3H]glutamate, bound at 37 degrees C, was dissociable when the membranes were then cooled to 4 degrees C. The binding of [3H]glutamate was increased in the presence of certain dipeptides such as L-phenylalanyl-L-glutamate (Phe-Glu); and the binding augmented by the presence of Phe-Glu, was also sensitive to temperature and osmolarity of the incubation buffer. Sonication of membranes in 5 mM glutamate increased the apparent binding of [3H]glutamate and abolished the stimulatory effect of Phe-Glu. These findings are consistent with the hypothesis that chloride-dependent association of [3H]glutamate with membranes from brain reflects, in part, a sequestration process, which may be driven by glutamate exchange.     

Social class, marital status, and cancer of the uterine cervix in England and Wales, 1950-1983.

STUDY OBJECTIVE--The aim was to investigate whether trends in mortality from cancer of the cervix uteri by age, marital status, and social class are compatible with current beliefs about the epidemiology of the disease. DESIGN--Data on mortality from cancer of the cervix for single and married women by age and social class were obtained from the Registrar General's Decennial Supplements on occupational mortality for the years 1950-53, 1959-63, 1970-72, and 1979, 1980, 1982, and 1983. Age standardised mortality rates were calculated directly by social class and marital status. SETTING--The data relate to all cases of carcinoma of the cervix reported in England and Wales in the years studied. MAIN RESULTS--There was a marked convergence of mortality between single and married women over the period within every social class grouping examined. The social class differential, however, remained essentially unchanged for both single and married women considered separately. CONCLUSIONS--Trends in mortality by marital status appear to reflect accurately the changes in the pattern of marriage and sexual behaviour that have taken place in the post-war period, whereas the patterns of other risk and protective factors such as screening explain these trends less well. In contrast, it seems likely that factors other than patterns of sexual behaviour and screening operate to maintain the social class differential in England and Wales.     

An analysis for menstrual data with time-varying covariates

This paper concerns the analysis of menstrual data; in particular, methodology to identify variables that contribute to the variability of menstrual cycles both within and between women. The basis for the proposed methodology is a parameterization of the mean length of a menstrual cycle conditional upon the past cycles and covariates. This approach accommodates the length-bias and censoring commonly found in menstrual data. Data from a longitudinal study of menstrual patterns and other variables among Lese women of the Ituri Forest, Zaire, illustrate the methodology. A small simulation illustrates the bias caused by incorrectly deleting the censored cycles.