Biomedical subjects

N Makris

Publications and source records attributed to N Makris.

51 records · Page 3Linked to original sources

PubMed1998

Precise segmentation of the lateral ventricles and caudate nucleus in MR brain images using anatomically driven histograms.

This paper demonstrates a time-saving, automated method that helps to segment the lateral ventricles and caudate nucleus in T1-weighted coronal magnetic resonance (MR) brain images of normal control subjects. The method involves choosing intensity thresholds by using anatomical information and by locating peaks in histograms. To validate the method, the lateral ventricles and caudate nucleus were segmented in three brain scans by four experts, first using an established method involving isointensity contours and manual editing, and second using automatically generated intensity thresholds as an aid to the established method. The results demonstrate both time savings and increased reliability.

Adult↗

PubMed1997

Reduced subcortical brain volumes in nonpsychotic siblings of schizophrenic patients: a pilot magnetic resonance imaging study.

Substantial evidence suggests that nonpsychotic relatives of schizophrenia patients manifest subtle abnormalities in communication, eye movements, event-related potentials, and neuropsychological processes of attention, reasoning, and memory. We sought to determine whether adult relatives without psychosis or schizophrenia spectrum diagnoses might also have structural brain abnormalities, particularly in subcortical regions found to be impaired in patients with schizophrenia itself. Subjects were six sisters of schizophrenic patients and eleven normal female controls. Sixty contiguous 3 mm coronal, T1-weighted 3D magnetic resonance images (MRI) of the entire brain were acquired on a 1.5 Tesla magnet. Cortical and subcortical gray and white matter was segmented using a semiautomated intensity contour mapping algorithm. Volumes were adjusted for total brain volumes. Adjusted gray matter subcortical volumes were significantly smaller in relatives than in controls in total hippocampus, right amygdala, right putamen, left thalamus, and brainstem. Relatives had significantly enlarged left and total inferior lateral ventricles. These results, though preliminary, suggest that some never-psychotic relatives of schizophrenic patients have abnormal brain structure. If replicated in a larger sample including both sexes, these results would suggest that the genetic liability to schizophrenia is also expressed as structural brain abnormalities.

Adolescent↗

PubMed1997

Morphometry of in vivo human white matter association pathways with diffusion-weighted magnetic resonance imaging.

The precise characterization of cortical connectivity is important for the understanding of brain morphological and functional organization. Such connectivity is conveyed by specific pathways or tracts in the white matter. Diffusion-weighted magnetic resonance imaging detects the diffusivity of water molecules in three dimensions. Diffusivity is anisotropic in oriented tissues such as fiber tracts. In the present study, we used this method to map (in terms of orientation, location, and size) the "stem" (compact portion) of the principal association, projection, and commissural white matter pathways of the human brain in vivo, in 3 normal subjects. In addition, its use in clinical neurology is illustrated in a patient with left inferior parietal lobule embolic infarction in whom a significant reduction in relative size of the stem of the left superior longitudinal fasciculus was observed. This represents an important method for the characterization of major association pathways in the living human that are not discernible by conventional magnetic resonance imaging. In the clinical domain, this method will have a potential impact on the understanding of the diseases that involve white matter such as stroke, multiple sclerosis, amyotrophic lateral sclerosis, head injury, and spinal cord injury.

Cerebral Cortex↗

PubMed1997

Acute effects of cocaine on human brain activity and emotion.

We investigated brain circuitry mediating cocaine-induced euphoria and craving using functional MRI (fMRI). During double-blind cocaine (0.6 mg/kg) and saline infusions in cocaine-dependent subjects, the entire brain was imaged for 5 min before and 13 min after infusion while subjects rated scales for rush, high, low, and craving. Cocaine induced focal signal increases in nucleus accumbens/subcallosal cortex (NAc/SCC), caudate, putamen, basal forebrain, thalamus, insula, hippocampus, parahippocampal gyrus, cingulate, lateral prefrontal and temporal cortices, parietal cortex, striate/extrastriate cortices, ventral tegmentum, and pons and produced signal decreases in amygdala, temporal pole, and medial frontal cortex. Saline produced few positive or negative activations, which were localized to lateral prefrontal cortex and temporo-occipital cortex. Subjects who underwent repeat studies showed good replication of the regional fMRI activation pattern following cocaine and saline infusions, with activations on saline retest that might reflect expectancy. Brain regions that exhibited early and short duration signal maxima showed a higher correlation with rush ratings. These included the ventral tegmentum, pons, basal forebrain, caudate, cingulate, and most regions of lateral prefrontal cortex. In contrast, regions that demonstrated early but sustained signal maxima were more correlated with craving than with rush ratings; such regions included the NAc/SCC, right parahippocampal gyrus, and some regions of lateral prefrontal cortex. Sustained negative signal change was noted in the amygdala, which correlated with craving ratings. Our data demonstrate the ability of fMRI to map dynamic patterns of brain activation following cocaine infusion in cocaine-dependent subjects and provide evidence of dynamically changing brain networks associated with cocaine-induced euphoria and cocaine-induced craving.

Adult↗

PubMed1996

Location of lesions in stroke patients with deficits in syntactic processing in sentence comprehension.

Sixty patients, 46 with left-hemisphere strokes and 14 with right-hemisphere strokes, and 21 normal control subjects were tested for the ability to use syntactic structures to determine the meaning of sentences. Patients enacted thematic roles (the agent, recipient and goal of an action) in 12 examples of each of 25 sentence types, which were designed to test a wide variety of syntactic operations. Both right-and left-hemisphere damaged patients performed worse than control subjects on syntactically complex sentences, and left-hemisphere patients performed worse than right-hemisphere patients. Eighteen patients with left-hemisphere strokes underwent CT scanning to image the perisylvian association cortex. There was no difference between the performance of patients with anterior and posterior lesions, and no correlation between the degree of impairment and the size of lesions in different regions of the perisylvian cortex. These results are consistent with the view that syntactic processing involves an extensive neural system, whose most important region is the left perisylvian cortex. When these results are combined with those of other studies, the picture that emerges is one in which, within this cortical region, this system manifests features of both distributed and localized processing.

Adult↗

PubMed1995

Analysis of lesions by MRI in stroke patients with acoustic-phonetic processing deficits.

We tested 10 aphasic stroke patients for the ability to discriminate and identify English phonemes. All patients underwent MRI and had their scans analyzed morphometrically. Patients with impairments in acoustic-phonetic processing tended to have lesions involving the left posterior supramarginal gyrus and the bordering parietal operculum, an observation further supported by regression and correlation analyses. These results are interpreted as evidence that the region including the left posterior supramarginal gyrus and parietal operculum plays a significant role in acoustic-phonetic processing.

Adult↗

PubMed1994

Effects of new brochures on blood donor recruitment and retention.

BACKGROUND: Currently, donors may arrive at blood collection sites without prior knowledge of eligibility and deferral criteria. STUDY DESIGN AND METHODS: The effects of distributing newly developed recruitment brochures 2 weeks in advance of blood drives and the provision of brochures on temporary deferral at the taking of health history were examined in four southeastern regional blood collection centers. Twenty-four similar pairs of worksites, with employee-only recruitment, were randomly assigned to a control (C) or experimental (E) group. Information about sponsor recruitment strategies, worksite factors, and first-time, repeat, and temporarily deferred donors was obtained at three collection drives per site over a 1-year period. Drive 1 was used as a baseline. Two weeks before Drives 2 and 3, the recruitment brochures were distributed to all Group E employees, with temporary deferral brochures provided as needed when the health history was taken. RESULTS: No significant differences between groups or drives were found in the total percentage of employees recruited or returning as a result of recruitment or deferral brochure distribution (Wilcoxon's signed rank test and t test). Substantiating previous observations by donor recruiters, the study results showed decreased donations during vacation periods and busier times at the workplace. Loudspeaker announcements led to decreased donations; increased donations followed special appeals in relation to a specific patient, an accident, or a natural disaster. CONCLUSION: The brochures may have encouraged previous donors to return, but their use did not significantly increase the recruitment of new donors or the return of temporarily deferred donors.

Blood Donors↗

PubMed1994

Hysterosalpingography and hysteroscopy in female infertility.

A total of 323 women of reproductive age (19-40 years) were submitted to a complete investigation of infertility routinely including hysterosalpingography and hysteroscopy. In 177 cases (54.7%) no pathological conditions were found by either of the applied methods, while in 65 cases (20.1%) similar abnormalities were observed by hysterosalpingography and hysteroscopy with a global correlation of 74.8%. Hysterosalpingography also presented false positive results in 11.7% and false negative ones in 13.3% of all the studied cases. In conclusion, the combined use of these techniques in infertility investigation gives complete and accurate information about the uterine cavity, despite the disadvantages of hysterosalpingography due to false positive and false negative results.

Adult↗

PubMed1994

Assessing clinical severity in children with sickle cell disease. Preliminary results from a cooperative study.

PURPOSE: Although it is clear that sickle cell disease is curable with bone marrow transplantation, there are few objective criteria that are helpful in the identification of suitable candidates for this aggressive and potentially life-threatening procedure. This disease is characterized by a highly variable clinical course, and there is a need to intervene with marrow transplant before the onset of disease-mediated chronic organ damage. These factors high-light the need for a clinical severity index that can prospectively identify patients who are at high risk for a turbulent clinical course and a poor prognosis. PATIENTS AND METHODS: We used the Cooperative Study of Sickle Cell Disease data base to identify features of the disease in early childhood (i.e., < 2 years of age) that are associated either with significant morbidity later in childhood or early mortality. Our study population includes the 1,944 children who entered the study before 12 years of age. Univariate analysis showed that factors associated with the occurrence of cerebrovascular accident (51 patients) include hematocrit, rate of change of pocked red cell count, and polymer fraction at 40% oxygen saturation (PF40). Only low hematocrit was predictive of death in this pediatric cohort (45 disease-related deaths). RESULTS: Our ability to identify other potential factors that correlate with these outcome measures is limited by their small numbers. Hence, it was necessary to designate a different endpoint whose relationship with various clinical and laboratory parameters could be assessed. To accomplish this, a distribution of acute events, which were defined as any episode of pain or acute chest syndrome, was calculated. Also, the age-specific "expected" event rate, defined as the mean number of events per patient-year of observation, was determined. CONCLUSIONS: The relationship between various aspects of sickle cell disease and high positive deviance from the expected event rate will be assessed in a cohort of 519 children who entered the study prior to 7 months of age and were followed beyond their second birthday.

Adolescent↗

PubMed1993

Operative hysteroscopy.

OBJECTIVE: Analysis of the obtained results after operative hysteroscopy for several intrauterine abnormalities. METHOD: Thirty women with uterine problems (7 polyps, 16 endometrial, 5 endocervical adhesions and 2 lost IUDs) were submitted to operative hysteroscopy under general anesthesia by using fine rigid auxiliary instruments at Lito Private Maternity Hospital and the 1st Department of Obstetrics and Gynecology of Athens University during 1991. RESULT: The adhesiolysis was successful in all the 21 cases with 5 subsequent pregnancies to date, the hysteroscopic excision of the 7 polyps was uneventful and the removal of the 2 lost IUDs was done by using a special forceps for foreign bodies. CONCLUSION: Operative hysteroscopy presented excellent results intra-operatively, post-operatively and in the routine follow-up by diagnostic hysteroscopy 3 months after intervention.

Adult↗

PubMed1989

Prevalence rate of cerebrovascular disease in the rural population of northwest Peloponnese, Greece. A direct epidemiological study.

In a direct (door-to-door) epidemiological study, the prevalence rate of cerebrovascular disease in the rural population of northwest Peloponnese, Greece, was found to be 995 strokes per 100,000 inhabitants over 20 years of age. This number is considerably lower than the prevalence rate (1,417 strokes per 100,000 inhabitants over 20 years of age) found in the urban population of the same county (Patras, Greece).

Adult↗

PubMed1982

Cefuroxime prophylaxis in caesarean section.

A double-blind, randomized prospective study was carried out in 96 women in labour requiring caesarean section to assess the value of antibiotic prophylaxis with cefuroxime compared with placebo. Forty-six patients received 750 mg cefuroxime intravenously before and every 8 hours for the first 72-hours post-operatively; the other 50 women received placebo injections. A significant decrease in post-operative morbidity was observed in the drug-treated group, there were far fewer endometrial, urinary and pulmonary injections, and those who received prophylactic cefuroxime had less days of hospitalization than the placebo-treated group. No serious side-effects were observed.

Cefuroxime↗

PubMedDate not supplied

Advanced application of magnetic resonance imaging in human brain science.

Magnetic resonance imaging (MRI) has revolutionized the practical demands of clinical neurology. This technology promises now to advance neurology in theoretical and applied realms of fundamental human brain science. We emphasize here two domains in which these advances will occur. The first is volumetric morphometry of the human brain. With MRI the multiple levels of processing of the brain may be characterized in terms of their absolute volumes and their relative sizes, perspectives indispensable for our understanding of the development and operation of neural systems. Volumetric morphometry also promises substantial increases in the specificity and sensitivity of neurological diagnosis, particularly where applied to disorders where structural abnormalities will be reflected only in volumetric abnormalities. The second direction of advance considered here is application of MRI in cortical mapping in support of cognitive neuroscience. In this application MRI provides means to map at high resolution the distribution of subcomponents of neural systems activated by behavioral paradigms. This line of investigation will carry forward rapidly our understanding of how the information processing algorithms of the brain are mapped upon the coordinates of the various gray matter structures of the brain. Among the practical consequences of this application will be a reasoned design of surgical field in tumor and epilepsy surgery.

Adult↗

PubMedDate not supplied

The selective impairment of the perception of first-order motion by unilateral cortical brain damage.

First-order (Fourier) motion consists of stable spatiotemporal luminance variations. Second-order (non-Fourier) motion consists instead of spatiotemporal modulation of contrast, flicker, or spatial frequency. In spite of extensive psychophysical and computational analysis of the nature and relationship of these two types of motion, it remains unclear whether they are detected by the same mechanism or whether separate mechanisms are involved. Here we report the selective impairment of first-order motion, on a range of local and global motion tasks, in the contralateral visual hemifield of a patient with unilateral brain damage centered on putative visual areas V2 and V3 in the medial part of the occipital lobe. His perception of second-order motion was unimpaired. As his disorder is the obverse of that reported after damage in the vicinity of human visual area MT (V5), the results support models of motion processing in which first- and second-order motion are, at least in part, computed separately at the extrastriate cortical level.

Aged↗

PubMedDate not supplied

Possible health effects of high manganese concentration in drinking water.

Three areas in the same region of northwest Peloponnesos, Greece, that had varying concentrations of manganese (Mn) in drinking water were selected for study. The Mn concentrations in areas A, B, and C were 3.6-14.6 micrograms/l, 81.6-252.6 micrograms/l, and 1 800-2 300 micrograms/l, respectively. A random sample (62 in area A, 49 in area B, and 77 in area C) of males and females who were at least 50 y of age were submitted to a thorough neurological examination and their whole-blood Mn and hair Mn concentrations were determined. Although all areas were similar with respect to social and dietary characteristics, significant differences were observed for prevalence of chronic manganese poisoning (CMnP) symptoms and hair Mn concentration. The means (both sexes) of neurological scores were 2.7, 3.9, and 5.2, respectively, for areas A, B, and C (Kruskal-Wallis, chi 2 = 6.44, 2 df, p less than .05 for males; chi 2 = 7.8, 2 df, p less than .05 for females). Hair Mn concentrations were also significantly different, the means for which were 3.51, 4.49, and 10.99 micrograms/g dry weight, respectively (both sexes [p less than .001 for each sex separately]). These results indicate that progressive increases of Mn concentration in drinking water are associated with progressively higher prevalences of neurological signs of CMnP and Mn concentration in hair of older persons.

Aged↗