Production of macromolecular activators of phagocytosis by lysed platelets.

Macromolecular activators of phagocytosis from platelets (MAPP: 1-MAPP and s-MAPP) are released from activated fresh platelets and enhance leukocyte phagocytosis via the Fcgamma receptors. In this study, production of MAPP was investigated in lysate of freeze-thawed stored platelets (PL). Incubation of PL and thrombin with precursors of MAPP (pre-MAPP: pre-1-MAPP and pre-s-MAPP) produced 1-MAPP and s-MAPP, whereas products released from stored platelets by stimulation with thrombin or collagen did not produce MAPP after incubation with pre-MAPP. The action of thrombin in MAPP formation with PL and pre-MAPP was inhibited by antithrombin III and heparin, and sequential incubation studies indicated that the key site of action of thrombin was on a component of PL. Other serine proteases such as trypsin could be substituted for thrombin in this reaction, whereas the action of thrombin was specific when whole platelets were used instead of PL. Gel filtration of PL before and after treatment with thrombin suggested that a macromolecule in PL (PMA-I) is digested by thrombin and liberates a 700 to 800 Da substance (PMA-II) which converts pre-MAPP to MAPP.

Ultrastructural and permeability features of microvessels in the olfactory bulbs of SAM mice.

The ultrastructural features of microvessels showing increased permeability to intravenously injected horseradish peroxidase (HRP) were examined in the olfactory bulbs of senescence-accelerated prone mice (SAMP8), which showed age-related deficits in learning and memory, and senescence-accelerated resistant mice (SAMR1), which did not show the age-related deficits. HRP was visualized with tetramethyl benzidine (TMB) and diaminobenzidine (DAB) for light and electron microscopic examination, respectively. In the olfactory bulbs of 13-month-old SAMP8 mice, the staining reaction with TMB for HRP appeared in the neuropil of central area (granule cell layer and subependymal layer), in the pia mater and in the vascular wall. Some vessels located in the central area showed several changes observed at the ultrastructural level. The cytoplasm of the endothelial cells, especially in the arterioles, was segmentally thickened and contained numerous vesicles and vacuoles, some of which were HRP positive. The endothelial cell surface was occasionally undulated with microvillous protrusions. Membranous inclusions within the basal lamina, suggesting the cellular (presumably pericytal) degeneration, were frequently observed, especially in venules. The collagen deposits were occasionally observed in the subendothelial space of some vessels. Perivascular cells with vacuolated inclusions or lipid-like droplets were present around some vessels in the central area of the olfactory bulbs of aged SAMP8 mice. On the other hand, in the microvessels located in the areas negative for HRP-TMB reaction, except the vessel walls, the cytoplasm of the endothelial cells with smooth luminal surface was flattened and some vesicles located there contained HRP-DAB reaction product. Weak staining reaction with TMB for HRP appeared also in the central area of the olfactory bulbs of 3-month-old SAMP8 mice and 3- and 13-month-old SAMR1 mice. The cytoplasm of the endothelial cells in the olfactory bulbs of these mice was focally thickened and contained some cytoplasmic vesicles. Occasionally, the endothelial cell surface was moderately undulated with few microvillous protrusions. Membranous inclusions within the basal lamina were not observed in these animals. These findings indicate that the endothelial cells and pericytes in some vessels located in the central area of the olfactory bulb of aged SAMP8 mice, which show staining reaction with TMB for HRP, are ultrastructurally changed, suggesting their altered functions.

Blood-brain barrier damage in reperfusion following ischemia in the hippocampus of the Mongolian gerbil brain.

Vascular permeability to intravenously injected horseradish peroxidase (HRP) was qualitatively examined in the hippocampus of ischemic Mongolian gerbil brains by light and electron microscopy. After 30 min of right common carotid artery occlusion followed by 90 min of reperfusion, the animal was perfused with a fixative and killed. Before the perfusion of the fixative, HRP was injected into the femoral vein. HRP was visualized with tetramethyl benzidine (TMB) and diamino-benzidine (DAB) for light and electron microscopy, respectively. Staining reaction with TMB for HRP appeared in medial or dorsal portions of the operated side of the hippocampus, especially around some vessels along the hippocampal fissure. Ultrastructural examination in the vessels along hippocampal fissure revealed that the endothelial cytoplasm contained HRP-filled vesicles or vacuoles in close proximity to the basal lamina, and seemed to be slightly electron-dense. Swollen pericytes, swollen astrocytic foot processes and perivascular cells with HRP-filled cytoplasm were also observed in that area. In this study, it was clearly demonstrated that intravascular macromolecules leaked transendothelially, through vessel walls in the hippocampal fissure, from the blood stream in the medial portions of the hippocampus during reperfusion following ischemia. These findings suggest that the blood-brain barrier in some vessels along the hippocampal fissure in the medial parts of the hippocampus is more vulnerable to ischemic insults than those in other brain areas.

Age-related changes in the brain transfer of blood-borne horseradish peroxidase in the hippocampus of senescence-accelerated mouse.

Age-related changes in the brain transfer of blood-borne horseradish peroxidase (HRP) were examined by light microscopy in senescence-accelerated prone mice (SAMP8) and senescence-accelerated resistant mice (SAMR1). The intracerebral HRP transferred from the blood stream was reacted with tetramethyl benzidine (TMB) and the area showing the presence of HRP-TMB reaction products was morphometrically evaluated. Areas containing HRP reaction products in the medial CA1 region and medial dentate gyrus of the hippocampus were observed in 3- and 13-month-old SAMP8 and SAMR1. The mean percentage of the positive area for the HRP to the area of interest was significantly higher in the rostral portion of the hippocampus in 13-month-old than in 3-month-old SAMP8. On the other hand, age-related changes in the area positive for HRP-TMB reaction products in the cortices and the caudal portion of the hippocampus in SAMP8 were not observed. In addition, positive staining reaction for HRP was also observed in the dorsal portion of the thalamus of 13-month-old SAMP8. There were no significant age-related changes in the area positive for HRP-TMB reaction products in rostral and caudal portions of the cortices and the hippocampus of SAMR1. These findings suggest that blood-borne macromolecules have access to the medial and rostral portion of the hippocampus, that this phenomenon becomes more pronounced during the process of senescence in the SAMP8 brain and, moreover, that intravascular macromolecules have access to the dorsal portion (periventricular area) of the thalamus of 13-month-old SAMP8.

A novel function of transferrin as a constituent of macromolecular activators of phagocytosis from platelets and their precursors.

Macromolecular activators of phagocytosis from platelets (MAPP:s-MAPP, 1500kDa and 1-MAPP, 300kDa) are glycoproteins released from human platelets and activate leukocyte phagocytosis via the Fc gamma receptors. Their production can be shown in CPD-stored platelets which have lost MAPP releasing activity by incubation with plasma-derived precursos of MAPP (pre-MAPP : pre-s-MAPP, 150kDa and pre-l-MAPP, 300kDa) in the presence of Ca++. Partial amino acid sequence analysis of s-MAPP revealed that it had homogeneity with transferrin (TF). Affinity chromatography using anti TF immunosorbent column showed that all of pre-MAPP and MAPP had immunoreactivity with anti TF antibodies. S-MAPP and 1-MAPP rich preparations from platelet release products lost their activity after treatment with ATP at acidic pH, in which condition iron atoms could be removed from holo-transferrin molecules. In the experiment using polymerized TF and stored platelets, it was shown that platelets incubated with dimer and tetramer TF could produce MAPP function. These results suggest that dimer and tetramer transferrin are precursors of s-MAPP and 1-MAPP, respectively and that iron atoms are necessary for their phagocytosis activating function.

Age-related changes in barrier function in mouse brain II. Accumulation of serum albumin in the olfactory bulb of SAM mice increased with aging.

Brain transfer rate (BTR) and brain to plasma concentration ratio (BPCR) of radiolabelled human serum albumin injected intravenously were calculated to evaluate the brain transfer of serum albumin in the cerebral cortex, the right hemi-brain and the olfactory bulb of senescence accelerated prone mice (SAMP8) and senescence accelerated resistant mice (SAMR1). BTR and BPCR in SAMP8 and SAMR1 were significantly higher in the olfactory bulb than in the cerebral cortex or the right hemi-brain. Age-related significant changes in BTR and BPCR were observed in the olfactory bulb of SAMP8 and SAMR1. These findings suggest that the barrier function to serum albumin in the olfactory bulb of SAMP8 and SAMR1 is not so tight as it is in the cerebral cortex and becomes weaker with age and that the age-related changes are manifested at a younger age in SAMP8 than in SAMR1.

Recovery of macromolecular activators of phagocytosis from platelets (MAPP) producing and releasing function in stored human platelets.

Macromolecular activators of phagocytosis from platelets (MAPP) were not released from platelets prepared from platelet concentrates (PC) obtained after anticoagulation with CPD solution and stored for more than 48 h. The MAPP activity which had escaped into the plasma disappeared after 72 h of storage. After incubation in dialyzed and Ca(2+)-supplemented plasma prepared from the same PC or from fresh peripheral blood, the platelets obtained after storage for 72 h released both MAPP (l-MAPP and s-MAPP) upon thrombin stimulation. Gel filtration studies of the plasma revealed that l-MAPP and s-MAPP were produced from the platelets incubated in plasma fractions corresponding to l-MAPP and s-MAPP, respectively. These observations suggest that platelets accumulate precursors of MAPP, pre-MAPP comprising pre-l-MAPP and pre-s-MAPP, in the presence of Ca2+, and produce and release MAPP when stimulated with thrombin.

Cerebral cysticercosis: a case report.

A case of cerebral cysticercosis is reported in a 49-year-old female who presented with headache, nausea, and vomiting. Lumbar CSF showed the findings of mild aseptic meningitis. CT scan revealed an enlargement of the left ambient cistern and a small cystic lesion in the left frontal cortex. MRI demonstrated multilobular cysts in the left ambient cistern with enhancement of their capsules, which compressed and distorted the midbrain. The cysts were surgically excised, and histological examination of the specimen disclosed characteristic features of cysticercus with viable larva. An excellent value of MRI in the diagnosis of intracisternal cysticercosis is emphasized.