The effects of X monosomy on brain development: Monozygotic twins discorcant for Turner's syndrome

Monosomy for the X chromosome is the most frequent cause of Turner's syndrome, a common clinical syndrome associated with particular physical and neurobehavioral features. The results from comprehensive assessment of prepubertal monozygotic female twins discordant for X monosomy are presented. Zygosity was established with DNA Fingerprinting and no evidence of chromosomal mosaicism was seen in either child. Physical features in the affected twin were relatively mild with respect to the full spectrum of physical malformations and disabilities associated with Turner's syndrome. The neurobehavioral phenotypes of the twins were compared. Although both sisters scored in the superior range of intelligence, the affected twin's Performance IQ was 18 points less than her sister, whereas Verbal IQ showed only a 3-point difference between the sisters. Other relative differences were noted within the executive, visuospatial, and visuomotor domains of function. Behavioral evaluation indicated greater problems with attention, hyperactivity, and anxiety in the affected twin. Quantitative analysis of brain anatomy revealed evidence of both general and regional effects of X monosomy on neurodevelopment. Cerebrospinal fluid volume was increased by 25% in the affected twin compared with her sister with a corresponding decrease in gray matter volume. The right frontal, right parietal–occipital, and left parietal-perisylvian regions showed the greatest discrepancy between the sisters with respect to increased cerebrospinal fluid and decreased gray matter volumes in the twin with X monosomy. Differences in the posterior fossa were also noted with a 50% relative increase in the volumes of the fourth ventricle and cisterna magna and a 10 to 15% relative reduction in size of the cerebellar vermis, pons, and medulla in the affected twin. The association between the neurobehavioral and neuroanatomical findings in the affected twin is discussed. The unique nature of the naturally occurring genetic phenomenon seen in this twin pair provides an opportunity to more fully elucidate the neurobehavioral phenotype associated with X monosomy and Turner's syndrome.     

Evolution of a form of pure alexia without agraphia in a child sustaining occipital lobe infarction at 21/2 years

The progress of cognitive visual dysfunction over an 8-year period of a child who sustained bilateral occipital-lobe infarctions at the age of 21/2 years is described. She survived with normal intelligence and went on to attend mainstream school. She manifested many features of cognitive visual impairment and, in particular, developed a form of pure alexia without agraphia. She achieved some letter-by-letter reading but no sight vocabulary development, including to her own name. She learned to write imaginatively employing phonetically true spelling but cannot read what she has written. Her progress and the difficulties encountered during the management of her condition are discussed in this first case report of the evolution of pure alexia without agraphia in childhood. The features of this syndrome in the developing child who has never developed the capacity to read are contrasted with that seen in affected adults.     

Clinical effectiveness of dermatomal evoked cerebrally recorded somatosensory responses

Among 129 patients with spine pain and radiculopathy in both the cervical and lumbar region, there were significant differences between the upper and lower extremity DSER groups, noting the higher number of normal studies by our criteria in the upper extremities as compared to the lower extremities. This difference may be due to the intertwining of the "nerve circuitry" of the input pathways. It appears that the dermatomal somatosensory evoked response is a study of low sensitivity and of high specificity.     

Renal clearance and protein binding of melphalan in patients with cancer

Summary The renal clearance of melphalan and the fraction unbound in plasma were determined after intravenous infusion of 5 mg/m² over 5 min in nine patients with cancer to obtain information regarding the mechanism of renal handling of melphalan. Four of the patients underwent bone marrow transplantation and also received an IV dose of 220 mg/m². Total melphalan clearance after the 5 mg/m² dose ranged from 66.0 to 272 ml/min per m²; the percentage of the dose excreted unchanged in urine, from 2.5% to 92.8%; renal clearance, from 4.1 to 188 ml/min per m²; the fraction unbound in plasma, from 0.0598 to 0.460; and t_1/2, from 39.4 to 84.3 min. Unbound melphalan clearance and renal clearance calculated from the unbound fraction in plasma for each patient ranged from 441 to 3356 ml/min per m² and 15 to 961 ml/min per m² respectively and were not related to serum albumin, serum creatinine or creatinine clearance. The percentage of the dose exctreted and melphalan renal clearance were not related to urine flow. There was evidence of active secretion of melphalan in the kidney an possible reabsorption. There were no significant paired differences in melphalan disposition between the high- and low-dose studies. Highly variable renal clearance involving active secretion may contribute in part to large interpatient differences in the total plasma clearance of melphalan in patients with cancer.This study was supported by a grant from The Queen Elizabeth Hospital Research Foundation     

Research activities in toxicology and toxicological requirements of the FDA for food and color additives

The Center for Food Safety and Applied Nutrition of the Food and Drug Administration has published guidelines for the safety assessment of direct food and color additives. These guidelines are to be updated beginning in 1988. The safety of a food and color additive must be established prior to marketing by an evaluation of probable exposure of consumers and appropriate toxicological information. "Safe" and "safety" are defined as a reasonable certainty that a substance is not harmful under the intended conditions of use. A number of tests are used in determining the safety of food additives. Some of these are: subchronic toxicity studies, chronic toxicity studies, carcinogenicity, reproduction, teratogenicity, and occasionally short-term tests for carcinogenicity. The Center also has a research program in toxicology which in part focuses on diet/toxicity interaction and risk assessment. Examples of such activities are investigation of the teratogenicity of textured vegetable protein and of the potential of zinc to prevent or ameliorate such effects, the development of whole rat embryo cultures as a model to investigate the mechanisms by which teratogens may act, and a program in pharmacokinetics and molecular toxicology to aid in studying assumptions underlying risk assessment.     

Pediatric solid-organ transplant recipients carry chronic loads of Epstein-Barr virus exclusively in the immunoglobulin D-negative B-cell compartment

Solid-organ transplant recipients are at risk for development of lymphoproliferative diseases. The purpose of this study was to examine the distribution of Epstein-Barr virus (EBV) load in the peripheral blood of pediatric transplant recipients who had become chronic viral load carriers (>8 copies/10(5) lymphocytes for >2 months). A total of 19 patients with viral loads ranging from 20 to 5,000 viral genome copies/10(5) lymphocytes were studied. Ten patients had no previous diagnosis of posttransplant lymphoproliferative disease (PT-LPD), while nine had recovered from a diagnosed case of PT-LPD. No portion of the peripheral blood viral load was detected in the cell-free plasma fraction. Viral DNA was found in a population of cells characterized as CD19(hi) and immunoglobulin D negative, a phenotype that is consistent with the virus being carried exclusively in the memory B-cell compartment of the peripheral blood. There was no difference in the compartmentalization based upon either the level of the viral load or the past diagnosis of an episode of PT-LPD. These results have implications for the design of tests to detect EBV infection and for the interpretation and use of positive EBV PCR assays in the management of transplant recipients.     

alpha-Methyldopa and the erythrocyte membrane.

To test the hypothesis that complement-mediated cell lysis and cell-mediated cytotoxicity operate by analogous mechanisms, cell membranes from two antibody-dependent cytotoxicity systems were examined by electron microscopy after negative staining. Ring-shaped membrane lesions generally similar to, but larger than, those previously described for complement lysis were observed. These findings are in agreement with recent measurements of larger functional pores for ADCC than complement.     

Circulating T-cell populations during mercuric chloride-induced nephritis in the Brown Norway rat.

Fluorescence-activated cell sorter analysis was used to study the peripheral lymphocyte populations during mercuric chloride (HgCl2)-induced autoimmune nephritis in the Brown Norway (BN) rat. Sequential studies showed a transient loss of T cells from peripheral blood attributable to decreases in the percentage of T-helper cells. In addition, there was a decrease in the percentage of T-cytotoxic/suppressor cells prior to the appearance of circulating anti-GBM antibodies, followed by elevated levels of T-suppressor cells during down-regulation of the response. This method may allow closer inspection of the events linking changes in T-cell populations and induction and termination of an autoimmune response.     

The immediate consequences of middle cerebral artery occlusion on GABA synthesis in mouse cortex and cerebellum.

The effect on gamma-aminobutyric acid (GABA) synthesis of focal ischaemia in the right cortex of the mouse was investigated by performing a right middle cerebral artery (MCA) occlusion. Synthesis of GABA was determined by measurement of the rate of GABA accumulation in tissue following injection of amino oxyacetic acid (AOAA; 30 mg/kg, i.p.). Five min following the MCA occlusion, the rate of GABA synthesis in the right (ischaemic) cortex was decreased by approximately 70% compared to either the left cortex or the right cortex of untreated controls. The basal GABA concentration was however unaffected. Four hours after the occlusion the rate of GABA synthesis was similar in the right and left cortex. The rate of GABA accumulation in the cerebellum was unchanged at both times after the right MCA occlusion compared with untreated control mice. The data suggest that there is a rapid but short lasting decrease in GABA synthesis following an ischaemic insult and it is suggested that this might be associated with the EEG spiking activity that occurs at this time.     

Phenotypic differences within the AB blood type of the feline AB blood group system

Flow cytometry immunolabeling, tube agglutination tests, and thin-layer chromatography immunostaining with two different anti-A monoclonal antibodies (anti-A mAb1 and anti-A mAb2) and one anti-B mAb were used to demonstrate differences in expression of the A and B antigens among erythrocytes from type A and four different type AB cats. Although the flow cytometric patterns of reactivity and agglutination scores for erythrocytes from types A and B cats detected with the anti-A and anti-B mAbs were consistent, reactivity among erythrocytes of different type AB cats was variable. By flow cytometric analysis, 99.9% of type A erythrocytes, no type B erythrocytes, 2.5–4.0% of erythrocytes from type AB cats 1, 3, and 4, and 60.7% of erythrocytes from type AB cat 2 had detectable A antigen when anti-A mAb1 was used. In contrast, 86.4% of type A erythrocytes, no type B erythrocytes, 20.2–38.0% of erythrocytes from type AB cats 1, 3, and 4, and 68.5% of erythrocytes from type AB cat 2 had detectable A antigen when anti-A mAb2 was used. In addition, 86.9% of type B erythrocytes, no type A erythrocytes, 83.1–96.8% of erythrocytes from type AB cats 1, 3, and 4, and 73.0% of erythrocytes from type AB cat 2 had detectable B antigen when the anti-B mAb was used. Agglutination scores of type AB cats were comparable to the percent binding on flow cytometry. Thin-layer chromatography immunostains confirmed differences in the amount of A antigen between erythrocyte glycolipids of type A and AB cats and those of type AB cats 1 and 2. These results suggest that at least two different phenotypes exist within the feline AB blood type, which differ in the amount of A antigen expressed on the erythrocyte surface.