Amoeboid Microglial Cells and not Astrocytes Synthesize TNF-alpha in Swiss Mouse Brain Cell Cultures

The role of tumour necrosis factor (TNF-alpha) in brain physiology and pathology has been the focus of several studies. However, the source of this lymphokine in the central nervous system and the regulation of its synthesis is still poorly understood. We have therefore used purified astrocytes and brain macrophages in culture to compare the abilities of these two cell types to synthesize TNF-alpha and its mRNA. We find that, in the Swiss mouse, no significant TNF activity or TNF-alpha mRNA are produced by astrocytes, even following activation with lipopolysaccharides (LPS). On the other hand, purified microglial cells express a cytotoxic activity able to kill TNF-sensitive LM cells. Part of this activity is released into the culture medium and part remains bound to the membrane after mild paraformaldehyde treatment, demonstrating the existence in the culture of the soluble and membrane-bound forms of TNF activity. The fact that amoeboid microglial cells, and not astrocytes, are the actual source of TNF in brain cultures was further demonstrated by Northern blot analysis and in situ hybridization using a TNF-alpha specific oligonucleotide probe. The definition of the cell type which, in the CNS, is responsible for TNF synthesis will allow the regulation of this lymphokine to be analysed and opens the way for a better understanding of the interactions between amoeboid microglial cells and the other cell types which make up the nervous system.     

Study of the Complex Between the Contrast Agent lobitridol (Xenetix®) and Elastase (PPE): A Model for Hydrophobic Site Protection in Drug-Protein Interactions

Purpose. The concept of Hydrophilic Sphere Stabilization, or Hydrophobic Shielding, has been postulated in the synthesis of biocompatible contrast agents in vascular imaging. To improve the safety of these polyiodinated agents, interactions with protein hydrophobic sites in biomacromolecules should be kept as low as possible. In order to evaluate the level of interactions with proteins, we have selected the serine proteinase Elastase, in presence of Iobitridol (Xenetix^®), as a model. Methods. The complex between Iobitridol and Pancreatic Porcine Elastase was investigated by X-ray diffraction techniques, on saturated monocrystals, using the synchrotron radiation at 0.98. Results. In contrast to Iohexol, which displays several interactions including one in the active site, Iobitridol is unable to interact directly with elastase. Only one partially occupied site is found in between two molecules of the crystal packing. Conclusions. The validation of the 'hydrophobic shielding' concept, which was at the origin of the design of the Iobitridol molecule, has been proven to be an essential feature in minimizing in vivo protein interactions.     

Effects of [3H]-BIDN,a novel bicyclic dinitrile radioligand for GABA-gated chloride channels of insects and vertebrates

1. The radiolabelled bicyclic dinitrile, [³H]-3,3-bis-trifluoromethyl-bicyclo[2.2.1]heptane-2,2-dicarbonitrile ([³H]-BIDN), exhibited, specific binding of high affinity to membranes of the southern corn rootworm (Diabrotica undecimpunctata howardi) and other insects. A variety of γ-aminobutyric acid (GABA) receptor convulsants, including the insecticides heptachlor (IC₅₀, 35±3 nM) and dieldrin (IC₅₀, 93±7 nM), displaced [³H]-BIDN from rootworm membranes. When tested at 100 μM, 1-(4-ethynylphenyl)-4-n-propyl-2,6,7-trioxabicyclo[2.2.2]octane(EBOB), 4-t-butyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane-1-thione (TBPS), 1-phenyl-4-t-butyl-2,6,7-trioxabicyclo[2.2.2]octane (TBOB) and picrotoxin failed to displace 50% of [³H]-BIDN binding to rootworm membranes indicating that the bicyclic dinitrile radioligand probes a site distinct from those identified by other convulsant radioligands.
2. Dissociation studies showed that dieldrin, ketoendrin, toxaphene, heptachlor epoxide and α and β endosulphan displace bound [³H]-BIDN from rootworm membranes by a competitive mechanism.
3. Rat brain membranes were also shown to possess a population of saturable, specific [³H]-BIDN binding sites, though of lower affinity than in rootworm and with a different pharmacological profile. Of the insecticidal GABAergic convulsants that displaced [³H]-BIDN from rootworm, cockroach (Periplaneta americana) and rat brain membranes, many were more effective in rootworm.
4. Functional GABA-gated chloride channels of rootworm nervous system and of cockroach nerve and muscle were blocked by BIDN, whereas cockroach neuronal GABA_B receptors were unaffected.
5. Expression in Xenopus oocytes of either rat brain mRNA, or cDNA-derived RNA encoding a GABA receptor subunit (Rdl) that is expressed widely in the nervous system of Drosophila melanogaster resulted in functional, homo-oligomeric GABA receptors that were blocked by BIDN. Thus, BIDN probes a novel site on GABA-gated Cl⁻ channels to which a number of insecticidally-active molecules bind.

     

Diurnal and nocturnal blood pressure drops in patients with focal ischemic glaucoma

Background: The purpose of this study was to assess the role of arterial hypotension in the pathogenesis of certain types of glaucoma. Methods: We compared diurnal and nocturnal fluctuations in blood pressure by using an ambulatory recording over a 24-h period in two different groups of patients: one of 16 patients with focal ischemic glaucoma (FIG) and another of 16 patients with primary open angle glaucoma (POAG). Results: Inpatients with FIG, compared to those with POAG, we found: lower diastolic blood pressure (BP; 75.7 vs 82.5 mmHg, P < 0.05), systolic BP (121.7 vs 131.2 mmHg, P < 0.05) and mean BP (90.5 vs 101.5 mmHg, P < 0.05) over 24 h; lower diurnal diastolic BP (78.1 vs 85.5 mmHg, P < 0.05), and systolic BP (124.6 vs 134.2 mmHg, P < 0.05); greater nocturnal systolic BP variability (8.2% vs 6.2%, P < 0.05); and a greater percentage of diurnal low readings (14.53% vs 2.8%, P<0.05), compared with the literature limits (101/61 mmHg). However, the number of nocturnal low readings was not different for either group. Conclusion: It is important to detect arterial hypotension — one of the components of the vascular factor — during examination of a patient with normal-pressure glaucoma. This is one element in preserving the best possible perfusion of the optic nerve.     

Interventional Radiology for Treating Soft Tissue Sarcomas

The role of interventional radiology for soft tissue sarcomas is only occasionally addressed in the literature. However, different techniques such as embolization, selective chemotherapy, chemoembolization, and acrylic cement osteoplasty can be helpful with the primary tumor, recurrences, and metastases. This article discusses these techniques and their complications in treatment of soft tissue sarcomas.     

Hemodynamic effects of medical antishock trousers during mechanical ventilation

Purpose

To compare the hemodynamic effects of medical antishock trousers (MAST) inflation in mechanically ventilated patients with normal and poor left ventricular function.

Methods

Twelve patients requiring respiratory support were divided into two groups according to baseline transesophageal echocardiography (TEE) measurements: normal left ventricular dimensions and fractional area of contraction (FAC=61 ± 5%) (n=7) and dilated cardiomyopathy with reduced FAC (21 ± 1%) (n=5). All patients were studied when two successive levels of load (mild load by inflation of the leg compartment of MAST at 50 cmH₂O and high load by adding the abdominal compartment of MAST inflated at 30 cmH₂O) were applied. Global left ventricular systolic function was assessed on the TEE transgastric short-axis view. End-systolic wall stress (ESWS) was used as an indicator of left ventricular afterload.

Results

Total respiratory, lung and chest wall compliances were reduced by 48%, 51% and 27% respectively at the high load level (P < 0.05). Whereas no hemodynamic changes occurred at mild load, the high load level produced an increase in left ventricular afterload as evidenced by concomitant increases in diastolic arterial blood pressure (66 ± 6 to 79 ± 6 mmHg,P < 0.05) and ESWS (69 ± 12 to 74 ± 12 Kdyn·cm^?2·m^?2,P < 0.05). In patients with dilated cardiomyopathy, this increase in afterload impaired the left ventricular systolic function and end-systolic area increased (19.0 ± 2.5 to 21.4 ± 2.9 cm²·m^?2,P < 0.05) while FAC decreased (22 ± 2 to 16 ± 2%,P < 0.05). Left ventricular end-diastolic area remained unchanged during the study in both groups.

Conclusion

MAST inflation impairs respiratory mechanics and global left ventricular systolic function in cardiac patients without changes in left ventricular preload.     

Supine Bicycle Exercise Echocardiography: A Potent Immediately Available Tool for Detection and Localization of Myocardial Ischemia for the Initial Cardiologist

Background: Exercise echocardiography (EE) is being used increasingly as an investigative technique now that dynamic images can be captured digitally. Its equivalent reliability with scintigraphic methods has been demonstrated in a hospital setting. This study analyzes its impact on daily practice. Materials and Methods: Standardized progressive stress was produced by supine bicycle ergometry. Echocardiographic images of complete cardiac cycles were obtained in standard apical and parasternal short-axis views before, during, and after maximum effort, and digitized for simultaneous analysis of synchronized images at rest and during exercise. Two hundred sixteen patients (175 men and 41 women; mean age 58 ± 10 years) were studied. Results: Image quality was suboptimal in 4 cases. In the remaining 212 cases, ischemia was detected in 91 cases, and the test was negative in 114 cases and doubtful in 7 cases. Control by selective coronary angiography, as indicated by the clinical situation, was performed in 52 cases. In this particular group, EE showed 87% sensitivity, which is significantly higher than the 59% recorded for conventional exercise testing (P > 0.0001). Conclusions: EE by bicycle ergometer in the supine position is a valid, noninvasive investigative technique that can be used in an outpatient situation (feasibility 95%) since it is readily available. Its value appears to be greatest in cases in which exercise ECG is not conclusive. A negative result enables the initial cardiologist to reassure the patient immediately, which has been demonstrated in the literature to have favorable prognostic value.     

Respiratory and ventilatory management of critically ill children during transport

As more and more pediatric intensive care units are established throughout the country, transport systems for critically ill children assume increasing importance. This article concerns the personnel, equipment, and other requirements for a transport system and reviews the respiratory and ventilatory management of pediatric patients during transport.