The "temporal processing deficit" hypothesis in dyslexia: new experimental evidence

The notion that developmental dyslexia may result from a general, nonspecific, defect in perceiving rapidly changing auditory signals is a current subject of debate (so-called "temporal processing deficit" hypothesis). Thirteen phonological dyslexics (age 10-13 years) and 10 controls matched for chronological and reading age were compared on a temporal order judgment (TOJ) task using the succession of two consonants (/p/-/s/) within a cluster. In order to test the relevance of the temporal deficit hypothesis, the task also included two additional conditions where either the two stimuli were artificially slowed or the interstimulus interval was expanded. As expected, the TOJ performance was significantly poorer in dyslexics than in controls. Moreover, in the "slowed speech" condition dyslexics' performance improved to reach the normal controls' level, whereas no significant improvement occurred when increasing the interstimulus interval. Finally dyslexics' performances, especially on the slowed condition, were found correlated with several tests of phonological processing (phoneme deletion, rhyme judgment, and nonword spelling tasks). These results lend support to the general temporal deficit theory of dyslexia.

Intensive training of phonological skills in progressive aphasia: a model of brain plasticity in neurodegenerative disease

Three patients with a typical syndrome of nonfluent primary progressive aphasia (Mesulam's syndrome) were trained daily with a remediation protocol including auditory exercises specifically designed to involve several aspects of phonological processing, a domain known to be specifically affected in the condition. The speech content of the exercises was based on the temporal theory of phonological processes according to which increasing the duration of formant transition should facilitate phoneme discrimination and phoneomic awareness. Significantly improved performance on the trained tasks was demonstrated in the three patients. Improvement further generalized to other tasks such as nonword repetition and reading. We conclude that such results (1) argue for using intensive focused therapy of language impairment in neurodegenerative disorders, (2) may constitute a good model of brain plasticity in neurodegenerative disorders in general, and (3) support theories of phonological processing emphasizing temporal features of the auditory signal.

Dyslexia: cultural diversity and biological unity

The recognition of dyslexia as a neurodevelopmental disorder has been hampered by the belief that it is not a specific diagnostic entity because it has variable and culture-specific manifestations. In line with this belief, we found that Italian dyslexics, using a shallow orthography which facilitates reading, performed better on reading tasks than did English and French dyslexics. However, all dyslexics were equally impaired relative to their controls on reading and phonological tasks. Positron emission tomography scans during explicit and implicit reading showed the same reduced activity in a region of the left hemisphere in dyslexics from all three countries, with the maximum peak in the middle temporal gyrus and additional peaks in the inferior and superior temporal gyri and middle occipital gyrus. We conclude that there is a universal neurocognitive basis for dyslexia and that differences in reading performance among dyslexics of different countries are due to different orthographies.

Pharmacokinetic and pharmacodynamic analysis of sedative and amnesic effects of lorazepam in healthy volunteers

This study describes for the first time the pharmacokinetic and pharmacodynamic modeling of the psychomotor and amnesic effects of a single 2-mg oral dose of lorazepam in healthy volunteers. Twelve healthy volunteers were included in this randomized, double-blinded, placebo-controlled two-way crossover study. The effect of lorazepam was examined for a battery of tests that explored mood, vigilance, psychomotor performance, and memory. The pharmacokinetic and pharmacodynamic modeling of these tests was performed using the indirect response model. Vigilance and psychomotor performance were significantly impaired. Short-term memory was not affected, but a paradoxical tendency to improvement of the score was observed 0.4 hours after drug intake. Significant impairment was observed for immediate and delayed cued verbal recall, for immediate and delayed free recall, and for picture recognition as well as for visual-verbal recall, but not for cued visual-spatial recall or priming. Globally, the different effects were greatest between 0.4 to 3 hours after dosing. However, the time course profile of the recovery period suggests a possible dissociation between the kinetics of the effects of lorazepam on vigilance, psychomotor performance, and visual episodic memory, on the one hand, and on verbal episodic memory, on the other. The pharmacokinetic and pharmacodynamic model used two compartments with first-order absorption to describe the lorazepam concentrations and an indirect response model with inhibition or stimulation of Kin to describe the effects. The mean values for calculated median effective concentration (EC50) derived from the pharmacokinetic and pharmacodynamic modeling of the different tests ranged from 11.3 to 39.8 ng/mL. According to these EC50 values, lorazepam seemed to be more potent on the delayed-recall trials than on the immediate-recall trials; similar observations were made concerning the free-recall versus cued-recall trials. The previously stated results suggest that the tests performed in this study represent sensitive measurements of the effects of lorazepam on the central nervous system. Moreover, the parameter values derived from pharmacokinetic and pharmacodynamic modeling, especially, the EC50 values, may provide sensitive indices that can be used to compare the central nervous system effects of benzodiazepines.

Startle response: epileptic or non-epileptic? The case for "flash" SMA reflex seizures

A 19-year-old woman complained of long-standing, frequent, debilitating brusque movements triggered by unexpected stimuli. She was neurologically normal and neuroimaging was also normal. Conspicuous startle reactions were easily reproduced under EEG and video monitoring: the interictal EEG was normal, the ictal recordings doubtful; clinically, the startle reaction was asymmetric, with elevation of the left limbs. The diagnosis of hyperekplexia and startle epilepsy were discussed. We learned that she had been evaluated at age 3-4 months for spontaneous, generalised tonic-clonic seizures and "infantile spasms", in fact for early-onset startle reactions triggered by noise or contact, in association with prominent EEG changes. A full remission had been achieved under ACTH therapy, but the startle reactions had reappeared at around age six. The patient was successfully treated with carbamazepine. The history, clinical and neurophysiological data led us to discuss the diagnosis of hyperekplexia and startle epilepsy. We concluded that the patient had an unusual form of cryptogenic focal epilepsy originating from the supplementary motor area, presenting as strictly stimulus-triggered "flash" seizures.

Hepatitis C virus infection in a community in the Nile Delta: risk factors for seropositivity

The purpose of this study was to identify risk factors for hepatitis C virus (HCV) infection in a rural village in the Nile Delta with a high prevalence of antibodies to HCV (anti-HCV). One half of the village households were systematically selected, tested for anti-HCV, and interviewed: 973 of 3,999 (24.3%) subjects were anti-HCV-positive (reflecting prior HCV infection but not necessarily current liver disease), with nearly equal prevalence among males and females. Anti-HCV prevalence increased sharply with age among both males and females, from 9.3% in those 20 years of age and younger to >50% in those older than 35, suggesting a cohort effect with reduced transmission in recent years. Multivariate regression was used to estimate independent effects of risk factors on seropositivity. Among those over 20 years of age, the following risk factors were significantly associated with seropositivity: age (P <.001); male gender (odds ratio [OR] = 2.5, 95% CI = 1.3-4.7); marriage (OR = 4.1, 2.4-6.9); anti-schistosomiasis injection treatment (OR = 2.0, 1.3-2.9); blood transfusion (OR = 1.8, 1.1-2.9), invasive medical procedure (surgery, catheterization, endoscopy, and/or dialysis) (OR = 1.5, 1.1-1.9); receipt of injections from "informal" health care provider (OR = 1.3, 1.0-1.6); and cesarean section or abortion (OR = 1.4, 1.0-1.9). Exposures not significantly related to anti-HCV positivity in adults included: history of, or active infection with, Schistosoma mansoni, sutures or abscess drainage, goza smoking in a group, and shaving by community barbers. Among those 20 years old or younger, no risk factors were clearly associated with anti-HCV positivity; however, circumcision for boys by informal health care providers was marginally associated with anti-HCV (OR = 1.7, 1.0-3.0). Prevention programs focused primarily on culturally influenced risks in rural Egyptian communities are being implemented and evaluated.

A longitudinal study of callosal atrophy and interhemispheric dysfunction in relapsing-remitting multiple sclerosis

OBJECTIVES

To determine if callosal atrophy and interhemispheric dysfunction can be detected in the early stages of relapsing-remitting multiple sclerosis (MS) and to evaluate their progression in relation to the disability and evolution of lesions seen on magnetic resonance imaging during a 5-year period.

METHODS

We compared 30 patients who had clinically definite early-onset replasing-remitting MS and mild disability with control subjects. Regional and segmental callosal size and extent of white matter abnormalities on magnetic resonance imaging, as well as performance on tasks exploring interhemispheric transfer of motor, auditory, and sensory information were assessed. Patients with MS were evaluated at baseline and after 5 years. Physical disability was determined at both times using the Expanded Disability Status Scale score.

RESULTS

Patients with MS were seen with significant callosal atrophy and functional impairment of interhemispheric transfer at baseline that worsened during the 5-year study. A significant correlation was found between the magnitude of disability and the severity of morphological and functional callosal involvement at baseline. This association persisted at year 5. Baseline clinical characteristics such as age and prestudy relapse rate were unrelated to callosal size or interhemispheric performance. However, the number of baseline T2-weighted lesions was correlated with callosal involvement and this relation persisted at year 5.

CONCLUSION

Patients who had relapsing-remitting MS in the early stages of the disease and mild disability had significant callosal involvement that progressed over time. The relationship between disability, T2-weighted lesions load, and degree of morphological and functional callosal impairment confirm the potential value of using callosal dysfunction as a surrogate marker of disease progression in MS.

The neurological basis of developmental dyslexia: an overview and working hypothesis

Five to ten per cent of school-age children fail to learn to read in spite of normal intelligence, adequate environment and educational opportunities. Thus defined, developmental dyslexia (hereafter referred to as dyslexia) is usually considered of constitutional origin, but its actual mechanisms are still mysterious and currently remain the subject of intense research endeavour in various neuroscientific areas and along several theoretical frameworks. This article reviews evidence accumulated to date that favours a dysfunction of neural systems known to participate in the normal acquisition and achievement of reading and other related cognitive functions. Historically, the first arguments for a neurological basis of dyslexia came from neuropathological studies of brains from dyslexic individuals. These early studies, although open to criticism, for the first time drew attention towards a possible abnormality in specific stages of prenatal maturation of the cerebral cortex and suggested a role of atypical development of brain asymmetries. This has prompted a large amount of subsequent work using in vivo imaging methods in the same vein. These latter studies, however, have yielded less clear-cut results than expected, but have globally confirmed some subtle differences in brain anatomy whose exact significance is still under investigation. Neuropsychological studies have provided considerable evidence that the main mechanism leading to these children's learning difficulties is phonological in nature, namely a basic defect in segmenting and manipulating the phoneme constituents of speech. A case has also been made for impairment in brain visual mechanisms of reading as a possible contributing factor. This approach has led to an important conceptual advance with the suggestion of a specific involvement of one subsystem of vision pathways (the so-called magnosystem hypothesis). Both phonological and visual hypotheses have received valuable contribution from modern functional imaging techniques. Results of recent PET and functional MRI studies are reported here in some detail. Finally, one attractive interpretation of available evidence points to dyslexia as a multi-system deficit possibly based on a fundamental incapacity of the brain in performing tasks requiring processing of brief stimuli in rapid temporal succession. It is proposed that this so-called 'temporal processing impairment' theory of dyslexia could also account for at least some of the perceptual, motor and cognitive symptoms very often associated with the learning disorder, a coincidence that has remained unexplained so far.

Evaluation of global DNA hypomethylation in human colon cancer tissues by immunohistochemistry and image analysis

BACKGROUND

Global hypomethylation of DNA is frequently observed in human tumours. This alteration is detected in early adenomas in colorectal tumorigenesis. Information is currently acquired after extraction of DNA from tissues, digestion with nucleases, and analysis by reverse phase chromatography, or treatment with restriction enzymes followed by gel electrophoresis analysis and Southern hybridisation with radiolabelled probes.

AIMS

The purpose of our work was to evaluate the global methylation status of DNA in malignant lesions without loosing the histopathological features of the samples.

PATIENTS

The investigation was performed on paired normal-tumour tissues from 13 patients undergoing surgical resection of colorectal adenocarcinomas.

METHODS

Antibodies raised against 5-methylcytidine can be used to label methyl rich regions in interphase nuclei. This technique was adapted to the study of paraffin embedded tissues and an immunohistochemical method was developed to assess the global methylation status of individual nuclei while preserving cell morphology and tissue architecture. Computer assisted quantification of the staining intensity was performed on malignant and normal zones of human colon tissues to test the correlation between the immunolabelling signal and the respective histological patterns observed.

RESULTS

Qualitative and quantitative differences were observed and measured between the normal and malignant part of each sample. Morphologically altered nuclei displayed densely labelled spots within faintly labelled areas whereas normal nuclei were darker and uniformly stained. Image analysis allowed calculation of the average integrated optical density of the nuclei in both types of tissues, demonstrating a constant and significantly lower intensity for the former type of cells.

Validation of the Frenchay Activities Index in a general population aged 16 years and older

OBJECTIVES

To assess the validity and reliability of the Frenchay Activities Index (FAI) and to establish age and sex norms in people at or over the age of 16 years.

DESIGN AND SETTING

Postal questionnaire survey to 1280 people randomly selected from 8 Health Authority patient registers in England.

MAIN OUTCOME MEASURES

FAI scores, subscale scores by age and sex, health status, perceived level of activity, and subjects' opinions on how well the FAI reflected their activities. Test-retest reliability was measured in 1 Health Authority.

RESULTS

The response rate was 49%. Men scored lower than women overall and on the domestic activities subscale. Respondents between the ages of 16 and 24 years and those over 85 years had the lowest FAI scores. FAI scores were related to self-reported health status, self-reported levels of activity, and presence of long-standing illness/disability. The FAI has high test-retest reliability. Qualitative data suggested that items such as sport, physical exercise, and caring for children should be included to make the FAI suitable for a wider age range.

CONCLUSION

The FAI has good construct validity, particularly in middle-aged and elderly people, and is reliable. For the FAI to be valid in nonstroke populations, items specific to younger people must be incorporated into it. We have established preliminary age and sex norms that should be interpreted with caution, given the low response rate.

Hepatitis C virus (HCV) infection in a community in the Nile Delta: population description and HCV prevalence

This report describes a cross-sectional survey of the prevalence of antibodies to hepatitis C virus (anti-HCV) in a rural Egyptian community in the Nile Delta. One half of the village households were systematically selected and examined by questionnaire and testing sera for anti-HCV and HCV RNA. Blood samples were obtained from 3, 888 (75.4%) of 5,156 residents >/=5 years of age; an additional 111 samples were obtained from children younger than 5 years. Overall, 973 (24.3%) of 3,999 residents were anti-HCV-positive, and the age- and gender-adjusted seroprevalence was 23.7%. Anti-HCV prevalence increased sharply with age, from 9.3% in those 20 years of age and younger to >50% in those older than 35 years. Currently or previously married individuals were more likely to be seropositive than those never married, controlling for age (Mantel-Haenszel risk ratio = 1.8; 95% CI: 1.3, 2.6). Of the 905 anti-HCV-positive samples tested, 65% were also positive for HCV RNA. Active schistosomal infection was not associated with anti-HCV status; however, history of antischistosomal injection therapy (reported by 19% of anti-HCV positives) was a risk for anti-HCV (age-adjusted risk ratio = 1.3; 95% CI: 1.2, 1.5). This study, the largest community-based survey to date, supports earlier reports of high levels of anti-HCV among adults in rural areas of Egypt, although many of those who are seropositive will not have active liver disease. The large reservoir of HCV infection in the community provides an opportunity to investigate risk factors for transmission, the natural history of infection and effectiveness of preventive methodologies, and raises concern about the prospect of an increasing incidence of chronic liver disease in the coming decades.

Developmental dyslexia: re-evaluation of the corpus callosum in male adults

Using a new method based upon the measurement of four angles, we analyzed the corpus callosum of 23 adult male dyslexics and 25 age-matched controls on MRI sagittal scans. Two out of the four angles measured showed significant differences between the groups that are consistent with previous findings concerning the size of the corpus callosum in dyslexics. In particular, posterior regions are concerned, displaying a lowered corpus callosum in dyslexics. These findings are discussed in relation to cortical parietal asymmetries and possible hormonal events, referring to the testosterone hypothesis, that could occur in utero or in the perinatal period in the dyslexic population.

Prevalence of antibodies to hepatitis E in two rural Egyptian communities

A population-based serosurvey in two rural Egyptian communities was used to assess age-specific prevalence of antibody to hepatitis E virus (anti-HEV). One community is in the Nile Delta (11,182 inhabitants; 3,997 participants) and the other in Upper Egypt (10,970 inhabitants; 6,029 participants). Samples were tested for anti-HEV with a commercial enzyme-linked immunoassay (ELISA) based on antigens derived from open reading frame (ORF)2 and ORF3. Although there was a clear difference in sensitivity among the lots of the commercial test used, it was still possible to determine the seroprevalence. The seroprevalence of anti-HEV exceeded 60% in the first decade of life, peaked at 76% in the second decade and remained above 60% until the eighth decade. Prevalence of this magnitude is among the highest reported in the world, with an age-specific pattern more similar to hyperendemic hepatitis A virus transmission than generally described. Lot-to-lot variation in the sensitivity of the commercial ELISA kit highlights a problem when comparing seroepidemiologic studies of different populations.

[Cognitive and emotional disorders in multiple sclerosis. Can a management strategy be envisioned?]

There is a lack of precise data concerning the natural history of cognitive disorders in multiple sclerosis (MS), but recent neuropsychological studies have demonstrated that the incidence of such disorders in MS appears to be frequent (40-65% of cases), and have shown in particular that recent memory, conceptual reasoning, attention, executive functions, visuospatial perception and information processing speed are negatively affected. In contrast, language functions, general intelligence and implicit memory appear to be relatively well preserved. Although the presence and the degree of cognitive disorders does not seem to be directly linked to disease duration or to the extent of physical disability, the relationship between cognitive decline and brain lesions detected by magnetic resonance imaging (MRI) is still a subject of discussion. The prevalence of emotional and affective disorders is difficult to estimate. Their frequency has only rarely been investigated, and the lack of data on the natural history of these disorders and those factors which they have in common (the psychosocial consequences of this chronic and disabling disease, cognitive impairment, and brain lesions) further complicate the determination of treatment strategy. The adoption of appropriate strategies could limit the negative impact of this disease on the social functioning of MS patients.

Quality control for parasitologic data

Accuracy of data is of paramount concern for all research. The task of providing objective assurances of accuracy of parasitologic data for a large, multi-center epidemiologic research project in Egypt (Epidemiology 1, 2, 3 [EPI 1, 2, 3]) presented a unique set of challenges undertaken jointly by the Ministry of Health's Qalyub Center for Field and Applied Research with technical assistance from Tulane University (New Orleans, LA). The EPI 1, 2, 3 project was part of large bilateral research program, the Schistosomiasis Research Project, undertaken jointly by the governments of Egypt and the United States. This paper describes the nature of the quality control system developed to accomplish this task, presents results and discusses the findings.

The epidemiology of schistosomiasis in Egypt: summary findings in nine governorates

Health questionnaires and parasitologic examinations of urine and stool were evaluated from a stratified random sample of 89,180 individuals from 17,172 households in 251 rural communities in 9 governorates of Egypt to investigate the prevalence of, risk factors for, and changing pattern of infection with Schistosoma sp. in Egypt. A subset, every fifth household, or 18,600 subjects, had physical and ultrasound examinations to investigate the prevalence of and risk factors for morbidity. Prevalence of S. haematobium in 4 governorates in Upper Egypt in which it is endemic ranged from 4.8% to 13.7% and averaged 7.8%. The geometric mean egg count (GMEC) ranged from 7.0 to 10.0 ova/10 ml of urine and averaged 8.1. Age stratified prevalence of infection peaked at 15.7% in the 10-14-year-old age group and decreased to 3.5-5.5% in all groups more than 25 years of age. Age-stratified intensity of infection peaked at approximately 10.0 ova/10 ml of urine in the 5-14-year-old age groups and was about half that in all groups more than 25 years of age. Males had higher infection rates and ova counts than females in all age groups. Schistosoma mansoni was rare in Upper Egypt, being consequential in only Fayoum, which had a prevalence of 4.3% and an average intensity of infection of 44.0 ova/g of stool. Risk factors for S. haematobium infection were male gender, an age <21 years old, living in smaller communities, exposures to canal water; a history of, or treatment for, schistosomiasis, a history of burning micturition or blood in the urine, and reagent strip-detected hematuria or proteinuria. The more severe grades (II and III) of ultrasonography-detected periportal fibrosis (PPF) were rare (15 of 906) in these schistosomiasis haematobia-endemic governorates. Risk factors for morbidity (ultrasonography-detected urinary bladder wall lesions and/or obstructive uropathy) were similar to those for infection, with the exception that risk progressively increased with age. Subjects with active S. haematobium infections were 3 times as likely as those without active S. haematobium infections to have urinary tract morbidity. The prevalence of S. mansoni in 5 governorates in Lower Egypt, where it is endemic, ranged from 17.5% to 42.9% and averaged 36.4%. The GMEC ranged from 62.6 to 93.3 eggs/g of stool and averaged 81.3. Age-stratified prevalence of infection peaked at 48.3% in the 15-19-year-old age group, but averaged 35-45% in all groups more than 10 years of age. The intensity of infection was highest in the 10-14-year-old age group, and showed a range of 70-85 eggs/g of stool in those > or =5 years of age. Males had higher infection rates and ova counts than females in all age groups. Schistosoma haematobium was rare in these governorates; Ismailia (1.8%) had the highest infection rate. Risk factors for S. mansoni were male gender, an age >10 years old, living in smaller communities, exposures to canal water, a history of, or treatment for, schistosomiasis or blood in the stool, detection of splenomegaly by either physical examination or ultrasonography, and ultrasonography-detected PPF. The more severe grades (II and III) accounted for 463 (13.3%) of the 3,494 having ultrasonography-detected PPF. Risk factors for morbidity (ultrasonography-detected PPF) were similar to those for infection except that inhabitants of smaller communities were not at increased risk. Active S. mansoni infection increased the odds ratio (OR) of having PPF by 1.37. In comparison with others with normal-size livers, subjects having hepatic enlargement in either the midclavicular line or the midsternal line detected by physical examination or ultrasonography had a reduced risk (ORs = 0.64-0.72) of PPF. The prevalences of lesions detected by ultrasonography were 23.7% for enlargement of right lobe of the liver, 11.3% for enlargement of left hepatic lobe, 20.6% for splenomegaly, and 50.3% for PPF. Schistosoma mansoni has almost totally replaced S. haematobium in Lower E

The epidemiology of schistosomiasis in Egypt: Qalyubia Governorate

The primary objectives of this study, carried out in Qalyubia Governorate in Egypt (south-central Nile Delta), were to continue tracking historical trends of infection prevalence of Schistosoma mansoni and S. haematobium, determine whether satellites (ezbas) of mother villages differed significantly with respect to schistosomiasis transmission, and to asses schistosomiasis-induced morbidity on a population basis using ultrasonography. Our study revealed that S. haematobium has virtually disappeared from Qalyubia governorate, and that S. mansoni prevalence continues to decline slowly (17% in 1991 compared with 19% in 1990). The prevalence of intestinal schistosomiasis was actually higher in the mother villages than in the ezbas of the same villages, indicating that prevalence based on surveys of villages alone did not (at least for Qalyubia) cause underestimates of true prevalence. (A mother village is the large village in an area that includes hamlets or ezbas. In many areas, the infection rate in ezbas is significantly higher than in the larger central village.) Ultrasonographic studies revealed that less than 3% of the population had stage 2 or stage 3 periportal fibrosis, commonly associated with chronic schistosomiasis mansoni. This low level of morbidity was consistent with earlier data from Qalyubia, which also showed a low level of S. mansoni-induced morbidity in this governorate.

Developmental dyslexia: atypical cortical asymmetries and functional significance

Using brain magnetic resonance imaging, we measured in 16 young developmental dyslexic adults and 14 age-matched controls cortical asymmetries of posterior language-related areas, including Planum temporale and parietal operculum cortical ribbon, and of the inferior frontal region related in the left hemisphere to speech processing. In addition, we assessed the sulcal morphology of the inferior frontal gyrus in both groups according to a qualitative method. The dyslexic subjects also performed specific tasks exploring different aspects of phonological and lexical-semantic processes. Results showed that: (1) contrary to most results reported in the literature, there is a lack of any morphological difference relative to Planum temporale asymmetry between the two groups; (2) there are significant differences between dyslexic and control subjects relative to frontal areas; (3) concerning the parietal region, there is a more asymmetrical pattern towards the left side in dyslexic subjects than in controls; and (4) relations in dyslexic subjects between parietal asymmetry coefficient and the level of performance in a phonological task have a particular reliance on verbal short-term memory, frontal asymmetry and performance in a non-word reading task. Considering these results it is suggested that phonological segmentation skills may relate to frontal lobe morphology, while phonological memory-based impairment in people with dyslexia may rather relate to parietal lobe morphology.

Pharmacokinetic-pharmacodynamic analysis of mnesic effects of lorazepam in healthy volunteers

AIMS

To describe the pharmacokinetic-pharmacodynamic modelling of the psychomotor and mnesic effects of a single 2 mg oral dose of lorazepam in healthy volunteers.

METHODS

This was a randomized double-blind, placebo-controlled two-way cross-over study. The effect of lorazepam was examined with the following tasks: choice reaction time, immediate and delayed cued recall of paired words and immediate and delayed free recall and recognition of pictures.

RESULTS

The mean calculated EC50 values derived from the PK/PD modelling of the different tests ranged from 12.2 to 15.3 ng ml-1. On the basis of the statistical comparison of the EC50 values, the delayed recall trials seemed to be more impaired than the immediate recall trials; similar observations were made concerning the recognition vs recall tasks.

CONCLUSIONS

The parameter values derived from PK/PD modelling, and especially the EC50 values, may provide sensitive indices that can be used, rather than the raw data derived from pharmacodynamic measurements, to compare CNS effects of benzodiazepines.

DNA global hypomethylation in EBV-transformed interphase nuclei

In tumors, DNA is often globally hypomethylated compared to DNA extracted from normal tissues. This observation is usually made after extraction and exhaustive digestion of DNA followed by analysis of nucleosides by chromatography or digestion with restriction enzymes, gel analysis, and hybridization. This approach provides an average value which does not give information on the various cell subpopulations included in heterogeneous samples. Therefore an immunochemical technique was set up with the aim of demonstrating, in a population of mixed cells, the possibility of detecting the presence of individual nuclei containing hypomethylated DNA, on a cell-by-cell basis. Monoclonal antibodies to 5-methylcytidine were used to label cells grown in vitro. Under appropriate fixation and permeabilization conditions, interphase nuclei were labeled. Quantitative differences in the labeling were detected between Epstein-Barr virus-transformed cells and normal peripheral blood monocytes by flow cytometry analysis. Similar differences were observed by fluorescence microscopy. Both results were confirmed by Southern transfer and hybridization of DNA fragments generated by restriction enzyme digestion. This observation, which is in accordance with the occurrence of global DNA hypomethylation in tumors as established by chromatography, opens the field for the analysis of fresh tumor samples by flow cytometry and microscopy.

[Divergent asymmetries of the temporo-parietal cortical areas: anatomo-functional correlations and evolutionary and developmental implications]

Human brains present a clear asymmetry of the postero-lateral cortical area, so called "planum temporale" (Geschwind and Levitsky). This asymmetry is on favour of the left brain. A similar asymmetry is observed on the parietal operculum. MRI studies of 37 healthy volunteers have shown a clear difference between individuals. Mixing the index of temporal and parietal asymmetry, the authors consider four types: the most frequent pattern concerns 90% of right handed. For the others, 10% there are left handed as right handed. On conclusion, planum as many asymmetry and opercular asymmetry can be divergent, and both canan to determines handedness.

Preparation and characterization of ofloxacin microspheres for the eradication of bone associated bacterial biofilm

Biodegradable polymers for localized delivery of antibiotics have emerged as an important approach to treating orthopaedic infections. In chronic forms of osteomyelitis which are thought to be associated with bacterial biofilm, localized delivery of a suitable antibiotic is desirable. This paper describes the formulation and in vitro evaluation of biodegradable ofloxacin microspheres for the eradication of bone associated bacterial biofilm infections. Ofloxacin microspheres were formulated using poly(glycolic acid-co-DL-lactic acid) (PGLA) by the emulsion solvent evaporation technique. The effects of process parameters such as phase volume, poly(vinyl alcohol) (PVA) concentration, and viscosity grade of the polymer during preparation on encapsulation efficiency (EEF) and in vitro release profiles were investigated. An increase in the phase volume or volume fraction from 21 to 35% at a constant internal phase volume resulted in an increase in EEF from 34 to 74%. Increasing PVA concentration from 0.25 to 2.5% w/v at a constant phase volume or volume fraction did not have an effect on the EEF. Ofloxacin release from the microsopheres was biphasic with an initial burst release followed by a slow release phase. An optimum slowing down of release was observed when the phase volume was 29%. Above and below this phase volume, release of ofloxacin was higher. The higher the viscosity grade of the polymer used for the preparation of microspheres, the higher the PVA concentration needed to prepare microspheres with slower release. The study indicates that various rates of ofloxacin release is possible by varying formulation conditions. This should provide a means for formulating sustained release microspheres of antibiotics for the treatment of biofilm infections associated with the bone.

Diabetes mellitus in Egypt: glycaemic control and microvascular and neuropathic complications

We performed a cross-sectional, population-based survey of persons 20 years of age and older living in Cairo and surrounding rural villages. The purpose was to describe glycaemic control and the prevalence of microvascular and neuropathic complications among Egyptians with diagnosed diabetes, previously undiagnosed diabetes, impaired glucose tolerance, and normal glucose tolerance. A total of 6052 households were surveyed. The response rate was 76% for the household survey and 72% for the medical examination. Among people with previously diagnosed diabetes, mean haemoglobin A1c, was 9.0%. Forty-two per cent had retinopathy, 21% albuminuria, and 22% neuropathy. Legal blindness was prevalent (5%) but clinical nephropathy (7%) and foot ulcers (1%) were uncommon in persons with diagnosed diabetes. Among people with diagnosed diabetes, microvascular and neuropathic complications were associated with hyperglycaemia. Retinopathy was also associated with duration of diabetes; albuminuria with hypertension and hypercholesterolaemia; and neuropathy with age, female sex, and hypercholesterolaemia. Albuminuria was as common in people with previously undiagnosed diabetes (22%) as those with diagnosed disease (21%). Mean haemoglobin A1c was lower (7.8%) and retinopathy (16%) and neuropathy (14%) were less prevalent in people with previously undiagnosed disease. Ocular conditions, blindness, and neuropathy were prevalent in the non-diabetic population. The microvascular and neuropathic complications of diabetes are a major clinical and public health problem in Egypt.

Comparative dissolution studies for mefenamic acid-polyethylene glycol solid dispersion systems and tablets

The purpose of this study was to enhance the dissolution of mefenamic acid (MFA) through the formation of solid dispersion systems, and to compare the dissolution of the unformulated dispersions with those of formulated dispersions in tablets. Solid dispersions of MFA were prepared in polyethylene glycol 3350 (PEG) as a binary system, and PEG and Tween 20 (TW) as a ternary system by the melt method. The dispersions were characterized by dissolution, scanning electron microscopy, and powder x-ray diffraction studies. A decrease in MFA composition in the binary dispersion systems from 50 to 5% w/w resulted in a 50% increase in the dissolution rate during the period of study, and this was threefold higher than that of pure MFA. Incorporation of TW in the preparation of ternary dispersion systems resulted in a further increase in MFA dissolution. A sevenfold increase in MFA dissolution was observed when the ternary system composition was MFA/PEG/TW 4.7:93:2.3 (% w/w). Scanning electron microscopy and x-ray diffraction pictures showed an increase in size and decrease in crystallinity of the dispersions, respectively. Compression of the dispersions into tablets did not have any effect on the dissolution of the drug from the dispersions. Compression of pure MFA and Avicel PH 101, which was used as a diluent and disintegrant, resulted in a threefold increase in dissolution. However, the dissolution of the uncompressed mixture was identical to that of pure MFA. Thus, further processing of the solid dispersions into tablets did not decrease the rate of dissolution of the drug in the dispersions. This may be very important in the formulation of solid dispersions as tablets, which could lead to a reduction in the dose of practically water-insoluble drugs.

[Corpus callosum disconnection syndromes and functional organization or the corpus callosum in adults]

Knowledge concerning the role of the corpus callosum derives from the study of patients with lesions of spontaneous or surgical origin. Three major aspects are defined: interhemispheric elementary transfer of symmetrically organized messages, complex transfer of asymmetrically organized information, interhemispheric transfer and complex behaviors. Symptoms are both complex and rather limited; they can be missed if they are not specifically searched for.