Differing Neurochemical and Morphological Sequelae of Global Ischemia: Comparison of Single- and Multiple-Insult Paradigms

The purpose of this investigation was to investigate pathomechanisms responsible for the deleterious effects of repeated episodes of brief forebrain ischemia. Halothane-anesthetized male Wistar rats were subjected to either (a) a single 15-min period or (b) three 5-min periods (separated by 1 h) of global forebrain ischemia by bilateral carotid artery occlusions plus hypotension (50 mm Hg), followed by various periods of recirculation. Brain temperature was normothermic throughout. In one series of rats, extracellular levels of glutamate, glycine, and gamma-aminobutyric acid (GABA) were measured in the dorsolateral striatum (n = 6-8 per group) and lateral thalamus (n = 4-6 per group) by microdialysis and HPLC before and during ischemia and during 3-5 h of recirculation. In a parallel series of rats (n = 6 per group), ischemic cell change was quantified at 2 (dark neurons), 24, or 72 h following either single or multiple ischemic insults. A single 15-min ischemic period led to massive glutamate release (13-fold increase; p = 0.001), which returned to normal by 20-30 min of recirculation and remained normal thereafter. By contrast, in rats with three 5-min periods of ischemia, the glutamate level rise with each repeated insult (four- to 4.5-fold; p < or = 0.02) was smaller than that observed during the single 15-min insult, but a late sustained rise (five- to six-fold; p < 0.05) occurred at 2-3 h of recirculation. Brief ischemia-induced elevations of glycine and GABA levels were detected in both the single- and multiple-insult groups, with normalization during recirculation. In contrast, the excitotoxic index, a composite measure of neurotransmitter release ([glutamate] x [glycine]/[GABA]), differed markedly following single versus multiple insults (p = 0.002 by repeated-measures analysis of variance) and increased by seven- to 12-fold (p < 0.05) at 1-3 h following the third insult. The total amount of glutamate released was 3.3-fold higher in the multiple-insult than in the single-insult group (p < 0.02). At 2 h of recirculation, histopathological analysis of dorsolateral striatum showed a significantly greater frequency of dark neurons in the multiple- than in the single-insult group (p < 0.05 by analysis of variance). In the thalamus, a higher frequency of ischemic neurons was seen in the multiple-than in the single-insult group at all intervals studied. Thus, in rats with multiple ischemic insults, accelerated ischemic damage was found in the striatum, and severe ischemic injury was documented in the thalamus.(ABSTRACT TRUNCATED AT 400 WORDS)     

Purification and partial characterization of immobilization antigens from Ichthyophthirius multifiliis.

Ichthyophthirius multifiliis, a parasitic ciliate of freshwater fishes, was found to have surface antigens (Ag) which elicited immobilizing antibodies (Ab) when injected into rabbits. An effort was made to purify and characterize these Ag (referred to as immobilization Ag) because of their potential role in protective immunity in fishes. Mice immunized with theront cilia were used for production of immobilizing monoclonal antibodies (MAb). Hybridomas were screened by indirect immunofluorescent light microscopy and immobilization of live parasites. Six hybridomas producing immobilizing MAb were cloned. Immobilizing MAb were used to affinity purify Ag solubilized with Triton X-114 and Na deoxycholate. Two membrane protein Ag of approximately 48 and 60 kDa were identified. Immobilizing MAb failed to react with these Ag on Western blots and, conversely, MAb that reacted with the Ag on Western blots did not immobilize live organisms. These results suggest that immobilization required native conformational epitopes which were altered by Western blotting procedures. Individual MAb reactive on Western blots recognized both the 48- and 60-kDa proteins indicating the presence of common epitopes. Affinity purified Ag elicited immobilizing antisera when injected into rabbits, mice, and channel catfish.     

Primary listerial infections are exacerbated in mice administered neutralizing antibody to macrophage colony-stimulating factor.

The serum and tissue levels of macrophage colony-stimulating factor (M-CSF) are elevated in mice during a primary immunologic response to infection by Listeria monocytogenes. Experiments were performed to determine the specific role of M-CSF in the resolution of listerial infections. The bulk of Listeria injected into a mouse i.v. is deposited in the liver. The expression of M-CSF mRNA in the liver increased markedly within 2 h postinfection. Maximum expression was dependent upon the dose of Listeria inoculated. The administration of anti-M-CSF mAb reduced the percentage of Mac-1+ mononuclear phagocytes subsequently found in the livers of infected animals. This reduction correlated inversely with an increase in the number of Listeria associated with both the parenchymal and NPC populations. These results suggest that M-CSF may play an important role in the primary immunologic response to Listeria in the liver by stimulating the production, mobilization, and/or biologic activity of Mac-1+ mononuclear phagocytes.     

Selectable plasmid vectors with alternative and ultrasensitive histochemical marker genes

Three different histochemical marker genes--E. coli beta-galactosidase gene (lacZ), Drosophila alcohol dehydrogenase gene (ADH) and human placenta alkaline phosphatase gene (ALP)--were cloned into a eukaryotic expression vector also containing the neomycin resistance gene. After calcium phosphate transfection and G418 sulfate selection of recipient BALB/c 3T3 cells, stable transfectants were pooled for histochemical staining. The lacZ-bearing cells produce aqua blue staining for beta-galactosidase; ADH-bearing cells, blue-black staining for alcohol dehydrogenase; and ALP-bearing cells, red staining for alkaline phosphatase. Cells carrying different marker genes can be easily differentiated by double-staining protocols. In addition, various photographic films can be used to enhance the colors of specific histochemically tagged cell classes. These plasmid vectors, providing selectability with the neomycin resistance gene and ultrasensitivity of alternative histochemical marker genes, will be very effective in virtually any biological system requiring analyses of multiple cell clones or classes in culture model systems or in situ.     

Preparation of enteric-coated microspheres of Mycoplasma hyopneumoniae vaccine with cellulose acetate phthalate: The effect of swine serum on micromeritic properties

Summary Cellulose acetate phthalate was used to prepare the Mycoplasma hyopneumoniae vaccine (MHV) microspheres using a solvent evaporation method. Swine serum was used as an additive in the antigen to form the core materials. The addition of serum had a significant effect on surface topography of the MHV microspheres. By using this modified solvent evaporation method, the recoveries of antigens in the MHV microspheres were generally over 90% of the weight and antigenicity of antigens originally added in the formulation.     

Transbilayer distribution and mobility of phosphatidylinositol in human red blood cells

The present studies describe the distribution of phosphatidylinositol (PI) within the membrane bilayer of the human red blood cell (RBC) as well as its transbilayer mobility. The membrane bilayer distribution was determined by measuring the hydrolysis of PI in the exterior leaflet of the RBC membrane using a PI-specific phospholipase C and by extraction of PI from the exterior leaflet using bovine serum albumin. The transbilayer mobility of PI was measured by following the fate of radiolabeled PI which was first incorporated into the outer leaflet of the RBC membrane. Our results indicate that PI is asymmetrically distributed in the membrane, with approximately 80% located in the inner and 20% in the outer leaflet of the bilayer. The rate of transbilayer mobility of PI is similar to that for certain molecular species of phosphatidylcholine and much slower than that reported for the aminophospholipids in the RBC membrane.     

Differential scanning calorimetry study of mixed-chain phosphatidylcholines with a common molecular weight identical with diheptadecanoylphosphatidylcholine

To examine the thermotropic phase behavior of various mixed-chain phosphatidylcholines in excess water and to compare it with the known behavior of identical-chain phosphatidylcholines, we have carried out high-resolution differential scanning calorimetric (DSC) studies on aqueous dispersions of 10 different mixed-chain phosphatidylcholines. These lipids, C(16):C(18)PC, C(18):C(16)PC, C(15):C(19)PC, C(19):C(15)PC, C(14):C(20)PC, C(20):C(14)PC, C(13):C(21)PC, C(21):C(13)PC, C(12):C(22)PC, and C(22):C(12)PC, have a common molecular weight which is the same as that of C(17):C(17)PC, an identical-chain phosphatidylcholine with a molecular weight of 762.2. When the values of any of the thermodynamic parameters (Tm, delta H, and delta S) of the mixed-chain phosphatidylcholines and C(17):C(17)PC are plotted against the normalized chain-length difference (delta C/CL), a linear function with negative slope is obtained provided that the value of delta C/CL is within the range of 0.09-0.4. The linear relationship suggests that these mixed-chain phospholipids are packed in the gel-state bilayer similar to the bilayer structure of C(17):C(17)PC at T less than Tm; however, the negative slope suggests that the conformational statistics of the hydrocarbon chain and the lateral lipid-lipid interactions of these phosphatidylcholines in the gel-state bilayer are perturbed proportionally by a progressive increase in the chain-length inequivalence between the two acyl chains within each lipid molecule. When the value of delta C/CL for mixed-chain phosphatidylcholines reaches the range of 0.44-0.55, the thermotropic phase behavior deviates markedly from that of less asymmetric phosphatidylcholines, suggesting that these highly asymmetric lipids are packed into mixed interdigitated bilayers at T less than Tm. The heating and cooling pathways of aqueous dispersions prepared from the 10 mixed-chain phospholipids are also discussed.