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Biomedical subjects

J A Sanders

Publications and source records attributed to J A Sanders.

At least 19 recordsLinked to original sources
PubMed1999

Effect of head-down tilt on brain water distribution.

Vascular and tissue fluid dynamics in the microgravity of space environments is commonly simulated by head-down tilt (HDT). Previous reports have indicated that intracranial pressure and extracranial vascular pressures increase during acute HDT and may cause cerebral edema. Tissue water changes within the cranium are detectable by T2 magnetic resonance imaging. We obtained T2 images of sagittal slices from five subjects while they were supine and during -13 degrees HDT using a 1.5-Tesla whole-body magnet. The analysis of difference images demonstrated that HDT leads to a 21% reduction of T2 in the subarachnoid cerebrospinal fluid (CSF) compartment and a 11% reduction in the eyes, which implies a reduction of water content; no increase in T2 was observed in other brain regions that have been associated with cerebral edema. These findings suggest that water leaves the CSF and ocular compartments by exudation as a result of increased transmural pressure causing water to leave the cranium via the spinal CSF compartment or the venous circulation.

Adult↗
PubMed1998

Evidence for cerebellar-frontal subsystem changes in children treated with intrathecal chemotherapy for leukemia: enhanced data analysis using an effect size model.

BACKGROUND: Following brain insult in early childhood, the later maturing neocerebellum and frontal lobes frequently show abnormalities. OBJECTIVE: To investigate the morphologic characteristics and function of a proposed cerebellar-frontal subsystem in children treated for acute lymphoblastic leukemia (ALL) with intrathecal methotrexate using quantitative magnetic resonance imaging, neuropsychological measures, nonlinear multiple regression analysis, and a statistical effect size model that augments interpretive validity of nonsignificant statistical findings, particularly from small sample size studies. DESIGN: Comparison and relationship of magnetic resonance imaging morphometry of cerebellar lobuli I-V and VI-VII and prefrontal cortices, and performance on 5 neuropsychological tests assessing visual-spatial attention, short-term memory, and visuomotor organization and coordination between childhood survivors of ALL and a matched control group. PARTICIPANTS: Ten childhood survivors of ALL treated between 1982 and 1989 with standard 3-year intrathecal chemotherapy, and matched control subjects. MAIN OUTCOME MEASURES: Morphometric results of cerebellar lobuli I-V and VI-VII and prefrontal cortices, and results of Trail-Making Tests, Rey-Osterreith Complex Figure Test, WISC-III Coding. RESULTS: Significant effect size model values for outcome measures in the ALL group support deficits in lobuli VI-VII and prefrontal cortices, and neuropsychological performance. Multiple regression analysis results were consistent with hypothesized involvement of a cerebellar-frontal brain subsystem. CONCLUSION: Treatment of children with ALL with intrathecal methotrexate before 5 years of age has structural and functional effects on the developing neocerebellar-frontal subsystem.

Adolescent↗
PubMed1996

Proton magnetic resonance spectroscopy in patients with glial tumors: a multicenter study.

The authors represent a cooperative group of 15 institutions that examined the feasibility of using metabolic features observed in vivo with 1H-magnetic resonance (MR) spectroscopy to characterize brain tumors of the glial type. The institutions provided blinded, centralized MR spectroscopy data processing long with independent central review of MR spectroscopy voxel placement, composition and contamination by brain, histopathological typing using current World Health Organization criteria, and clinical data. Proton 1H-MR spectroscopy was performed using a spin-echo technique to obtain spectra from 8-cc voxels in the tumor and when feasible in the contralateral brain. Eighty-six cases were assessable, 41 of which had contralateral brain spectra. Glial tumors had significantly elevated intensities of choline signals, decreased intensities of creatine signals, and decreased intensities of N-acetylaspartate compared to brain. Choline signal intensities were highest in astrocytomas and anaplastic astrocytomas, and creatine signal intensities were lowest in glioblastomas. However, whether expressed relative to brain or as intratumoral ratios, these metabolic characteristics exhibited large variations within each subtype of glial tumor. The resulting overlaps precluded diagnostic accuracy in the distinction of low-and high-grade tumors. Although the extent of contamination of the 1H-MR spectroscopy voxel by brain had a marked effect on metabolite concentrations and ratios, selection of cases with minimal contamination did not reduce these overlaps. Thus, each type and grade of tumor is a metabolically hetero-geneous group. Lactate occurred infrequently and in all grades. Mobile lipids, on the other hand, occurred in 41% of high-grade tumors with higher mean amounts found in glioblastomas. This result, coupled with the recent demonstration that intratumoral mobile lipids correlate with microscopic tumor cell necrosis, leads to the hypothesis that mobile lipids observed in vivo in 1H-MR spectroscopy may correlate independently with prognosis of individual patients.

Adolescent↗
PubMed1996

Low birth weight in urban Harare.

OBJECTIVES: 1. To measure the incidence of low birth weight from all institutional deliveries in a defined catchment area of urban Harare. 2. To estimate the relative proportions of preterm and small for gestational age (SGA). DESIGN: The study was descriptive and was conducted during the last three months of 1986. SETTING: The low risk maternity units in three high density suburbs, Highfield, Glen Norah and Glen View and the referral centre Harare Central Hospital. SUBJECTS: All babies born to women residing in the study areas in the maternity clinics and those transferred to the referral hospital were identified and weighed. MAIN OUTCOME MEASURES: For low birthweight babies gestation was estimated by the Dubowitz method and perinatal outcome was recorded. RESULTS: During the three month study period in 1986, 2,056 babies in total were born; 223 (10.8%) of which were low birthweight. Of these 65 (44%) were preterm and 55 (37%) were SGA. CONCLUSION: The findings show a lower percentage of low birthweight and SGA babies than in many developing countries but higher than the norm for developed countries. The study demonstrates a need for resources to prevent low birthweight delivery and improve care for low birthweight babies.

Female↗
PubMed1995

1H MR spectroscopy in patients with metastatic brain tumors: a multicenter study.

In a cooperative study involving six clinical MR centers, localized 1H MR spectroscopy was used to characterize untreated metastatic brain tumors (40 cases, 45 lesions). Cubic volumes (3.4 or 8 cm3) filled for more than 50% by metastatic brain tissue were examined by single-voxel double spin echo MRS, by using chemical shift selective imaging (CHESS) pulses for water suppression and TE = 135 ms. Choline (Cho), creatine (Cr) and N-acetyl aspartate (NAA) levels in brain metastases of mammary carcinoma (n = 13), lung cancer (n = 11) and melanoma (n = 10) were similar. Metastasis NAA/Cho signal intensity ratio varied between 0.00 and 1.17, compared with 2.68 +/- 0.56 (SD) in lobus occipitalis and 1.94 +/- 0.63 in corpus nuclei caudati region (P < 0.0001, both). 1H MR spectroscopy, although not suited to recognize the primary tumor of metastases, could serve as a clinical test for excluding (metastatic) tumor as cause of solitary focal brain disorders that are hard to diagnose with current imaging methods.

Adult↗
PubMed1995

Mapping function in the human brain with magnetoencephalography, anatomical magnetic resonance imaging, and functional magnetic resonance imaging.

Integrated analyses of human anatomical and functional measurements offer a powerful paradigm for human brain mapping. Magnetoencephalography (MEG) and EEG provide excellent temporal resolution of neural population dynamics as well as capabilities for source localization. Anatomical magnetic resonance imaging (MRI) provides excellent spatial resolution of head and brain anatomy, whereas functional MRI (fMRI) techniques provide an alternative measure of neural activation based on associated hemodynamic changes. These methodologies constrain and complement each other and can thereby improve our interpretation of functional neural organization. We have developed a number of computational tools and techniques for the visualization, comparison, and integrated analysis of multiple neuroimaging techniques. Construction of geometric anatomical models from volumetric MRI data allows improved models of the head volume conductor and can provide powerful constraints for neural electromagnetic source modeling. These approaches, coupled to enhanced algorithmic strategies for the inverse problem, can significantly enhance the accuracy of source-localization procedures. We have begun to apply these techniques for studies of the functional organization of the human visual system. Such studies have demonstrated multiple, functionally distinct visual areas that can be resolved on the basis of their locations, temporal dynamics, and differential sensitivity to stimulus parameters. Our studies have also produced evidence of internal retinotopic organization in both striate and extrastriate visual areas but have disclosed organizational departures from classical models. Comparative studies of MEG and fMRI suggest a reasonable but imperfect correlation between electrophysiological and hemodynamic responses. We have demonstrated a method for the integrated analysis of fMRI and MEG, and we outline strategies for improvement of these methods. By combining multiple measurement techniques, we can exploit the complementary strengths and transcend the limitations of the individual neuro-imaging methods.

Brain↗
PubMed1995

Haemolytic uraemic syndrome following Shigella dysenteriae type 1 outbreak in Zimbabwe: a clinical experience.

Shigella dysenteriae type 1 related dysentery outbreak in Zimbabwe at the end of 1992 has been associated with an increase in the frequency of haemolytic uraemic syndrome (HUS). In order to document this new clinical experience a retrospective study was undertaken to document clinical and laboratory features, treatment and outcome of children with HUS. During the period January 1993 to June 1994, 96 children with HUS were seen at the referral hospitals in Harare. Severe and prolonged anaemia was a common feature and 80 pc of the children were given blood transfusions. Severe anaemia (HB < 6g/dl) was however, present in 50 pc of the children prior to death. Leucocytosis (white blood cell count > 20 x 10(9)/L) was present in 87 pc of the children on admission and there was no association between the level of leucocytosis and anuria. Anuria was present in 37 (39 pc) and was associated with a mortality of 68 pc. Peritoneal dialysis was performed in 26 (27 pc) patients. Major neurological complications were seen in a third of the children. Thirty eight children died, an overall case fatality rate (CFR) of 40 pc. Earlier recognition, prompt and comprehensive supportive therapy may improve the immediate survival in children with HUS in Zimbabwe.

Child↗
PubMed1993

Neuromagnetic mapping of brain function.

Magnetic source imaging, a technique that combines magnetoencephalography (MEG) and magnetic resonance (MR) imaging, was used to localize the somatosensory and auditory cortex in seven healthy subjects. Functional neuromagnetic data were obtained with a 37-channel biomagnetometer. Structural MR imaging data were obtained with a 1.5-T superconducting imager. Coordinates used in defining MEG and MR imaging space were reconciled to produce magnetic source images that displayed the putative locations of somatosensory and auditory activity in relation to brain anatomy. Sources of somatosensory activity were typically localized to the postcentral gyrus; sources of auditory activity were localized to the superior temporal plane. Extension of these results to patients with tumors (or other disorders) that distort normal brain anatomy has the potential to make noninvasive magnetic source imaging examinations clinically useful in guiding neurosurgical interventional procedures.

Adult↗
PubMed1991

Purification, immunochemical characterization, and immunohistochemical localization of rat hepatic aryl sulfotransferase IV.

Aryl sulfotransferases catalyze the formation of sulfuric acid esters from a diverse group of endogenous and xenobiotic organic chemicals. The isoenzyme of aryl sulfotransferase in livers of male Sprague-Dawley rats that exhibits the most varied substrate specificity is aryl sulfotransferase IV. A new method for the purification to homogeneity of aryl sulfotransferase IV was developed that, when compared with previously described procedures, provided a greater than 10-fold increase in total yield of enzyme/g of tissue. Homogeneous aryl sulfotransferase IV was used to prepare polyclonal antibodies in male New Zealand White rabbits. Results of immunochemical analyses demonstrated that these antibodies reacted with only a single protein in rat hepatic 100,000 x g supernatant fractions and, further, that the immunoreactive protein had the isoelectric point and subunit molecular mass characteristic of aryl sulfotransferase IV. Immunohistochemical analyses demonstrated that aryl sulfotransferase IV is present in hepatocytes throughout the liver, although centrilobular cells contain a significantly greater (p less than 0.01) amount of aryl sulfotransferase IV than do either midzonal or periportal cells, in which similar levels of the enzyme are found.

Animals↗
PubMed1989

Differentiation of adolescent activity participation.

The sex typing or lack of it among 133 adolescent activities was investigated. Twenty-seven percent (32) of the activities on an Adolescent Activity Questionnaire showed very clear participation differences for male and female adolescents (11 to 18 years old). The initial two factors extracted in a principal components factor analysis were easily interpreted as feminine and masculine activities. Discriminant function analysis of 15 items from the first three factors yielded an 8-item function on the basis of which every sample member was correctly classified as male or female. Masculine activities included more sports-related activities and activities dealing with mechanics and building, whereas feminine activities were domestic in nature and included more sedentary activities (e.g., reading, writing in diaries).

Adolescent↗
PubMed1989

Rhabdomyolysis detected by bone imaging.

Rhabdomyolysis involves necrosis of skeletal muscle and may arise from multiple conditions both traumatic and nontraumatic. Bone imaging with Technetium-99m phosphates is a very sensitive indicator of acute muscle damage and may be used to visualize the extent of rhabdomyolysis and its resolution. A case of alcohol-induced rhabdomyolysis is presented.

Alcoholism↗
PubMed1989

Klebsiella pneumoniae osteomyelitis: demonstration by three-phase radionuclide bone imaging.

The Klebsiella pneumoniae bacillus is a rare cause of acute hematogenous osteomyelitis of long bones. Bony involvement usually develops from a bacteremia associated with a Klebsiella pulmonary or urinary tract infection. Diabetes mellitus, alcoholism, or cirrhosis are predisposing conditions to the development of this form of osteomyelitis. A case report follows in which two sites of Klebsiella osteomyelitis were demonstrated by three-phase bone imaging in a patient with both diabetes and alcoholism.

Adult↗
PubMed1985

Staging of lung cancer. A cost-effectiveness analysis.

Previous reports found the 67Ga scan highly accurate in staging lung cancer. In the present study the cost-effectiveness of the 67Ga scan was measured and compared with that of routine tests (radionuclide liver and bone scans, brain CT scan) used to stage lung cancer. In 160 patients, the 67Ga scan had a lower sensitivity, specificity, and negative predictive value than the combination of routine tests in detecting metastatic disease. The 67Ga scan was less accurate than the appropriate routine test in establishing the presence of liver, bone, and brain metastases. In the mediastinum the 67Ga scan was not more accurate than the chest radiograph. The average cost to accurately stage a patient by 67Ga scan was $812.12 and by routine tests was $737.60. The cost for metastatic disease was $1,417.70 by 67Ga scan and $1,287.70 by routine tests. It is concluded that at our institution the use of 67Ga scan to stage lung cancer is not cost-effective.

Bone Neoplasms↗
PubMed1985

Progressive paresis in sheep due to delayed neurotoxicity of triaryl phosphates.

This report describes the history, signs, histopathology, and diagnosis of a delayed neurotoxicity in Suffolk sheep caused by transmission oil. The signs of toxicity included hyperexcitability, a stiff gait, tetraparesis and inability to maintain sternal recumbency. The circumstances involved in exposure to the transmission oil were determined. Histopathology revealed widespread degeneration of axons in the spinal cord, especially their more distal portions.

Animals↗