Characterization of cerebral infarction by multicomponent analysis of transverse magnetization decay curves.

RATIONALE AND OBJECTIVES. Individual components of the transverse magnetization decay curve (TDC) were assessed for their ability to characterize ischemia in photochemically induced cerebral infarcts. METHODS. Fifty rats were randomly divided into equal-sized experimental and control groups, which were subdivided into groups studied at five different time points, ranging from 6 hours to 22 days. All the rats received transcalvarial irradiation with 560-nm light. Five rats in each time group also received a sensitizing dye before irradiation. In these latter animals, lesions of uniform size and location developed. Lesions were compared with tissue of similar volume and location from the contralateral cortex of the experimental animals and with tissue from both hemispheres of the control animals. TDCs of all the samples were measured and fit with mono- and bi-exponential functions. RESULTS. Unlike the control tissue, infarcted tissue displayed definitive two-component TDC behavior. The time course of the bi-exponential parameters yielded information unavailable from mono-exponential analyses. CONCLUSIONS. Bi-exponential analysis of TDCs may have diagnostic use as a more sensitive indicator of cerebral infarction than mono-exponential analyses.     

Use of computerized CT analysis to discriminate between Alzheimer patients and normal control subjects

A newly developed computerized technique was used to analyze the CT scans of 49 patients with dementia of the Alzheimer type and 31 normal control subjects. Nine brain regions distributed across five CT slices were evaluated for each individual. For the purpose of analysis, the patients and controls were divided into an exploratory set and a test set. Several discriminant functions were conducted on the exploratory set and applied to the test set. The combination of variables that focused on regions in the temporal lobe was most accurate in differentiating Alzheimer patients from controls (94%). This degree of accuracy was achieved only when subjects younger than 65 years old were analyzed separately from those 65 years old and older. The newly developed computer software program was able to discriminate between independently selected groups of Alzheimer patients and control subjects. The program was most effective when the analysis emphasized regions in the temporal lobe and when subjects younger than 65 years old were analyzed separately from those 65 years old and older.     

Contralateral approach to bilateral and ophthalmic aneurysms

In a previous survey, we found a high incidence of fatal rupture of an unclipped aneurysm in patients with multiple aneurysms. To deal with this problem, we introduced a more vigorous technique that accesses aneurysms previously considered unapproachable during one operating session. Attempts were made to clip middle cerebral and ophthalmic aneurysms contralateral to the operative exposure. We have successfully clipped contralateral aneurysms of the posterior communicating artery when bilateral aneurysms were present. We have also used this contralateral approach successfully with single ophthalmic and proximal carotid aneurysms that pointed medially. We review the cases of 39 patients with 43 intracranial aneurysms operated from the contralateral side and present the surgical technique in relation to the angiographic findings.     

The clinical value and risks of lung biopsy in children with congenital heart disease

A retrospective review was made of 59 open lung biopsy specimens taken between 1984 and 1988 from children with congenital heart disease who were at risk for pulmonary vascular disease. Thirty-seven patients (ranging in age from 3.5 months to 23 years; median age, 14 months) had a primary left-to-right shunt (group A) and 22 patients (ages 1 to 15 years) had palliated cyanotic heart disease (group B). Forty-five of the lung biopsy specimens were requested as frozen sections. In both groups lung biopsy specimens were graded by the Heath-Edwards classification and correlated against preoperative hemodynamic data and outcome. In group A patients, carefully measured pulmonary vascular resistance and pulmonary/systemic vascular resistance ratio were reliable indicators of the structural state of the pulmonary vascular bed, obviating the need for routine lung biopsy. Pulmonary/systemic vascular resistance ratios greater than 0.45 accurately predicted all patients with irreversible pulmonary vascular disease, and pulmonary vascular resistance greater than 7 units.m2 accurately predicted all but one case of disease. Reversibility of pulmonary vascular changes is not synonymous with immediate postoperative survival: Fatal postoperative pulmonary hypertensive crises occurred in the presence of reversible pulmonary disease. Of those considered for the Fontan procedure, a mean pulmonary artery pressure less than 30 mm Hg and pulmonary vascular resistance less than 3 units.m2 correlated with Heath-Edwards grade I or normal lung biopsy results. In 36% of group B patients, reliable assessment of pulmonary vascular resistance could not be made, indicating a possible need for open lung biopsy procedures. When lung biopsy procedures were used as an isolated procedure, they were more dangerous (20% mortality, 13% morbidity) than previously reported. Intraoperative frozen sections are not adequate to accurately assess pulmonary vascular changes (9% error); serial paraffin sections are required.     

Role of nitric oxide in modulating neurotransmitter release from rat striatum

The effect of the nitric oxide synthase inhibitor N-nitro- -arginine methyl ester (L-NAME) on the basal and stimulation-evoked release of dopamine (DA) and acetylcholine (ACh) was investigated in rat striatum. The experiments were carried out in isolated superfused striatal slices, loaded with either [³H]-dopamine or [³H]-choline.We have found that L-NAME reduced the elecrical field stimulation-evoked release of DA, while its enantiomer N-nitro-D-arginine methyl ester (D-NAME) was ineffective. In the presence of the nitric oxide (NO) precursor -arginine L-NAME failed to influence DA release. Furthermore, treatment with the N-methyl- -aspartate (NMDA) receptor antagonist MK-801 completely reversed the effect of L-NAME on striatal DA release. In contrast, L-NAME had no effect on either the basal or the stimulation-evoked ACh release in any experimental conditions studied.Our data indicate that endogenously produced NO is involved in the modulation of striatal DA, but not in ACh release. Furthermore, it seems likely that the modulatory effect of NO is linked to activation of presynaptic NMDA receptors located on the striatal dopaminergic nerve terminals.     

Feedback Stimulation of Somatodendritic Serotonin Release: A 5-HT3 Receptor-Mediated Effect in the Raphe Nuclei of the Rat

Slices from rat midbrain containing the raphe nuclei and from hippocampus were prepared, loaded with [³H]5-HT and superfused and the resting and the electrically stimulated [³H]5-HT release was measured. The 5-HT₃ receptor agonist 2-methyl-5-HT (1 to 10 μmol/l) increased the resting tritium outflow in superfused raphe nuclei slices, EC₅₀ 5.3 μmol/l. The 2-methyl-5-HT-induced increase of tritium outflow was an external Ca²⁺-independent process and was not altered by reserpine pretreatment but it was reversed by addition of the 5-HT uptake inhibitor fluoxetine (1 μmol/l). The 5-HT₃ receptor antagonists ondansetron and GYKI-46 903 (1 μmol/l) did not antagonize the stimulatory effect of 2-methyl-5-HT on resting tritium outflow. 2-Methyl-5-HT in lower concentration increased the electrically induced tritium overflow from raphe nuclei slices (EC₅₀ 0.56 μmol/l) and also from hippocampal slices preloaded with [³H]5-HT. These effects were reversed by 1 μmol/l of ondansetron and GYKI-46903. The 5-HT₃ receptor antagonists (1 μmol/l) were without effects on depolarization-evoked [³H]5-HT release at 2 Hz stimulation, when 10 Hz stimulation was used, ondansetron and GYKI-46 903 reduced the tritium overflow from raphe nuclei slices. These data indicate that 5-HT₃ receptors positively alter depolarization-induced somatodendritic 5-HT release in the raphe nuclei. They also show that 2-methyl-5-HT is able to evoke 5-HT release not only from vesicles but also from cytoplasmic stores via a transporter-dependent exchange process.     

Assessment of bedside umbilical vein balloon septostomy using two-dimensional echocardiographic guidance in transposition of great arteries

The effectiveness of "bedside" balloon atrial septostomy via the umbilical vein using 2-dimensional echocardiography was compared to the traditional femoral vein approach using fluoroscopy in a series of neonates with transposition of great arteries from March, 1984 to April, 1987. There were 7 neonates who had balloon septostomy performed at the "bedside" (Group I) compared to 13 who had the procedure performed in the catheterization laboratory (Group II). Group II consisted of 7 newborns who had elective femoral vein catheterization under fluoroscopy (Group IIA) and 6 who failed "bedside" umbilical vein balloon septostomy and subsequently had the femoral vein approach under fluoroscopy (Group IIB). Results showed that adequacy of balloon septostomy was not related to the approach used, with 4 of 7 in Group I and 9 of 13 in Group II with an adequate atrial tear and clinical response. The Delay time to septostomy (i.e. time elapsed from initial assessment to commencement of balloon septostomy) and Procedure time (i.e. time taken to complete the balloon septostomy) was significantly shorter for Group I (mean time = 0.7 hours and 0.26 hours respectively) compared with Group IIA (mean time = 2.6 hours and 1.8 hours) and Group IIB (mean time = 2.4 hours and 1.4 hours). Of note, there was no significant increase in Delay time between Group IIA and IIB.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of endothelial cell migration with a novel in vitro assay system

In this study we introduce a novel in vitro 'oil-drop' assay system for the measurement of endothelial cell (EC) migration, based on the original concept of the Teflon fence assay (Pratt et al., 1984; Am. J. Pathol. 117: 349–354). An aliquot of 15–20,000 human umbilical vein EC (HUVEC) is pipetted through a layer of mineral oil. The cells readily attach, spread and migrate on the surface of a matrix-coated tissue culture dish as a confluent circular monolayer. Migration is measured as the net increase in the total area covered at 24 hours. We have used this system to quantify EC migration on matrices composed of a mixture of type I collagen and either von Willebrand factor (vWF) or fibronectin (FN) in the presence or absence of tumor necrosis factor (TNF). Plating efficiency on both vWF/collagen and FN/collagen, measured by counting cells after attachment and spreading, is about 80%. With this method, migration on vWF/collagen was about 6.4 mm² and 5.3 mm² for TNF-treated and untreated HUVEC, respectively. HUVEC migration on FN/collagen was slightly greater – 6.4 mm² and 6.5 mm² with and without TNF treatment, respectively. During the 24 hour time period, HUVEC numbers increased 30–40% on vWF/collagen, and 60–80% on FN/collagen, with increased proliferation observed with TNF- treatment. EC proliferation could be completely inhibited by 2 mM hydroxyurea. This assay system has proven useful in our studies to quantify cell migration and proliferation.