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Biomedical subjects

S Weis

Publications and source records attributed to S Weis.

104 records · Page 6Linked to original sources
PubMed1986

Cortex perfusion index: a sensitive detector of acute rejection crisis in transplanted kidneys.

Damage to the renal cortical microcirculation, an early event in the course of acute rejection crisis (ARC), usually precedes measurable functional derangements in the transplanted kidney. Direct assessment of cortical blood flow by radionuclide renography may provide a sensitive and reliable index to the diagnosis of ARC, with particular regard to the differential diagnosis of ARC and ATN. Computer generated time-activity curves of global, cortical, and medullary renal blood flow were analyzed in 67 instances (35 patients) of renal allograft dysfunction and correlated with needle biopsy of these kidneys. No increase in cortex perfusion index (CPI), i.e., decrease in cortical perfusion, was found when the patients were suffering from ureteral obstruction or drug and viral nephropathy (mean perfusion index (PI) increase (8%). In contrast, a marked increase in CPI of 193% was noted in ARC. Global and medullary PI increased only 116%. As a result, global and medullary PI were capable of diagnosing ARC in only 73% and 55% of the cases, respectively, whereby cortex PI correctly diagnosed ARC in 94% of the cases. Selective analysis of cortical perfusion may thus enhance the accuracy of [99mTc]DTPA scans (radionuclide renograph) for the early detection of ARC and in differentiating ARC from nonimmunological causes of kidney allograft dysfunction.

Graft Rejection↗
PubMed1986

Morphometric analysis of the human corpus callosum fails to reveal sex-related differences.

No observations of sex differences in the splenium of the human corpus callosum are made. In the data there is no support for the concept that sex related functional hemispherical discrepancies are due to differences in area and width of the splenium of corpus callosum. However variability within a sex is often larger than the variability between the two sexes. The results are discussed with regard to a neurobiological theory of schizophrenia.

Aged↗
PubMed1984

A lack of interocular transfer of spatial conditional discrimination in pigeons.

Pigeons were monocularly trained to peck one of two keys according to the color of the keys. In one task two keys were horizontally mounted on the front panel of the experimental chamber, and in the other task two keys were mounted vertically. Pigeons did not show interocular transfer of either task. The failure of the transfer was discussed in terms of role of visuomotor integration in interocular transfer of learning.

Animals↗
PubMed1983

Evidence for bilateral vagal innervation of postganglionic parasympathetic neurons in chicken heart.

Stimulation of the cervical vagus nerves caused an output of acetylcholine (ACh) from the isolated chicken heart, which almost exclusively was released from the postganglionic neurons: (+)-tubocurarine (3 X 10(-14) M) reduced the output to 12 +/- 6% (n = 7) of the control. Stimulation of the two nerve trunks ws equally effective in releasing ACh.--Evidence that a large number of postganglionic neurons receives bilateral innervation was based on two experimental series. (1). The sum of the ACh outputs evoked by unilateral (separate) nerve stimulation of the right and the left vagus was higher than the bilaterally evoked output (100%) and increased with increasing frequencies (10, 20 and 40 Hz) from 115 +/- 13% to 131 +/- 9% (n = 13). In the presence of 10(-4) M 4-aminopyridine, unilaterally evoked output (40 Hz) was further increased from 131 to 176 +/- 5% (n = 21).--(2.) In the presence of 4-aminopyridine plus hemicholinium-3 (2 X 10(-5) M), unilateral nerve stimulation at 40 Hz evoked an output of ACh that decreased from 477 to 79 pmol g-1 min-1 during a 20 min-period of stimulation due to transmitter depletion. Thereafter output of ACh evoked by stimulation of the contralateral nerve was reduced by 73% as compared to the control value (475 pmol g-1 min-1; output without the preceding 20 min-stimulation).--It is concluded that a large number of parasympathetic postganglionic neurons of the chicken heart receives a dual excitatory input from both right and left vagus nerve.

Acetylcholine↗
PubMed1983

Spurious hyperchloremia and decreased anion gap in hyperlipidemia.

A patient with overt lipemia presented with hyponatremia, hyperchloremia, and a negative anion gap. The hyperchloremia and negative gap resulted from overestimation of chloride levels due to a light-scattering effect in the colorimetric assay, an effect that was reproducible in vitro. In a prospective study, this effect produced substantial overestimations at even modest degrees of hyperlipemia. This effect expands the differential diagnosis of a decreased gap, adds to the list of technique-dependent artifacts in lipemia, and, if present, must be recognized for a patient's fluid and electrolyte status to be accurately defined.

Adult↗
PubMedDate not supplied

A method for the quantification of the size of liver metastases.

A method for the quantification of the size of liver metastases based on stereologic principles is presented. This evaluation procedure was applied retrospectively to routine computerized tomography (CT) scans of the liver and allowed reliable estimation of the volume of liver metastases. Furthermore, the data were used to create three-dimensional (3D) representations of the examined organ by computer reconstruction.

Adult↗
PubMedDate not supplied

Cytochrome c oxidase defects of the human substantia nigra in normal aging.

Based on morphological, biochemical, and molecular biologic analyses, degeneration of the dopaminergic nigrostriatal system has been reported to occur with normal aging. In the present study, the substantia nigra of 36 human brains with normal aging was investigated by means of morphometry and immunohistochemistry. The anteromedial (Am), anterointermediolateral (Ail), posteromedial (Pm), and posterolateral (Pl) nuclei of the substantia nigra were analyzed using antibodies directed against the subunits II/III of cytochrome c oxidase (COX), the complex IV of the respiratory chain. The numerical density of melanin-positive neurons with COX defects was significantly increased in the four investigated nuclei, namely Am, Ail, Pm, and Pl. These cells did not show any histologic signs of degeneration. The numerical density of melanin-positive neurons without COX defects was decreased with aging. The data of the present study indicate that complex IV defects of neurons in the substantia nigra might be one cause of neuronal dysfunction occurring during aging.

Adult↗
PubMedDate not supplied

Evaluation of gemfibrozil therapy: predictive response from lipoprotein subfraction analysis.

Subjects with high-density lipoprotein cholesterol (HDL-C) values of less than 47 mg/dL (mean 35.6 +/- 5.5 mg/dL) were selected for this study to examine relationships between plasma lipids, lipoprotein components, and the outcome of gemfibrozil therapy. Changes in plasma lipoprotein subfractions were determined to better understand the previously observed variability of the responses in both HDL-C and triglycerides to gemfibrozil. Based on the data collected, an attempt was made to identify pretreatment lipid parameters that may be predictive regarding the efficacy of gemfibrozil therapy. Serum samples were analyzed at the outset and after the conclusion of 12 weeks of gemfibrozil therapy. Because the HDL-C response to therapy was highly variable, the data from patients were separated into two groups, responders (>20% increase in HDL-C) and nonresponders (<20% increase in HDL-C). The lipid components of lipoprotein subfractions were evaluated using multiple regression analysis yielding predictive models that show the relationship between specific lipoprotein subfractions and the percentage change in HDL-C and posttreatment triglyceride levels. Group classification was then predicted with 78% accuracy using specific lipoprotein subfractions to estimate an individual's percentage change in HDL-C. The major difference between the responder and nonresponder groups was their respective correlations between triglyceride-lowering and changes in HDL-C. In the responder group, there was a significant correlation between the changes in HDL-C and the lowering of triglycerides (r = 0.61, p = 0.03), whereas the nonresponder group showed no such correlation (r = 0.17, p = 0.52). The predictive model also proved to be highly accurate in forecasting the effectiveness of the triglyceride-lowering action of gemfibrozil in this group of patients.

Adult↗
PubMedDate not supplied

Down syndrome: MR quantification of brain structures and comparison with normal control subjects.

For quantification of brain structures from MR scans, a novel, powerful stereologic tool known as Cavalieri's principle was applied. This tool enables an objective estimation of volume. The method was applied to detect differences in various brain structures between persons with Down syndrome and control subjects. On the basis of absolute values, smaller volumes for the whole brain, cerebral cortex, white matter, and cerebellum were seen in persons with Down syndrome. Similar results were observed when a normalization procedure, based on the volume of cranial cavity, was used. Stereologic determinations of the volumes of brain structures from MR images can reliably identify volume differences between persons with Down syndrome and control subjects.

Adult↗
PubMedDate not supplied

Morphometric analysis of the corpus callosum using MR: correlation of measurements with aging in healthy individuals.

PURPOSE: To analyze changes of the human corpus callosum and MR midsagittal brain structures during normal aging. METHODS: A morphometric evaluation strategy for quantification of these brain structures on MR scans was developed. This computerized measuring program did allow the acquisition of more than 100 one- and two-dimensional parameters. RESULTS: During normal aging, the anterior parts of the corpus callosum (genu and anterior parts of the trunk) were significantly decreased, suggesting alterations of frontal and temporal interhemispheric fiber systems. Further changes were seen in callosal thickness and callosal width of the anterior parts of the corpus callosum. The profile area of the telencephalon was significantly reduced during normal aging. The size of the mesencephalon showed age-specific changes. CONCLUSIONS: The proposed computer program proved to be a powerful and reliable tool to get objective and reproducible quantitative data of corpus callosum and midsagittal brain structures. Specific age changes were found in the corpus callosum, indicating alteration of the frontotemporal interhemispheric fiber systems.

Adult↗
PubMedDate not supplied

Vascular changes in the cerebral cortex in HIV-1 infection: I. A morphometric investigation by light and electron microscopy.

The microvasculature of the cerebral cortex in AIDS brains was investigated by means of stereology at the light and electron microscopic levels. Stereologic parameters for microvessels were determined in formalin-fixed autopsy tissue of 24 AIDS patients and of 35 age- and sex-matched controls. At the light microscopic level these encompassed the measurement of the diameter, volume fraction, surface area density, and length density; at the electron microscopic level profile area, perimeter, diameter of capillaries, endothelial cells, pericytes, and basal lamina as well as the mean thickness of the basal lamina were measured. In AIDS brains a significant increase in the diameter of cortical vessels was noted. The surface area density (Sv) and volume fraction (Vv) of microvessels were likewise significantly increased in AIDS brains. No changes were noted for the length density (Lv) which also indicates that no changes in the number of vessels occur in HIV-1 infection. Ultrastructural thinning of the basal lamina was a consistent finding. Vacuoles occurred in the basal lamina of capillaries and increased in number and size in AIDS brains. Using morphometric methods, significant changes of cortical vessels are detectable at the light and electron microscopic level. These changes most probably represent the morphological substrate of an altered blood-brain-barrier in AIDS brains and may account for the reported hypoperfusion demonstrated in SPECT analyses.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Kaposi's sarcoma in the cerebellum of a patient with AIDS.

A case of Kaposi's sarcoma in the left cerebellar hemisphere of a patient with AIDS is presented. The lesion was not detected with imaging techniques in the patient who, during the clinical course, did not show neurological signs and symptoms. This small nodular lesion was only revealed at autopsy. This rare finding is an example of the broad spectrum of central nervous system involvement in HIV-1-infected individuals.

Acquired Immunodeficiency Syndrome↗