Fine particulate matter exposure during pregnancy and infancy and incident asthma

1. Download : Download high-res image (240KB)
2. Download : Download full-size image

     

Increased fluidity of Plasmodium berghei-infected mouse red blood cell membranes detected by electron spin resonance spectroscopy

The fluidity of Plasmodium berghei-infected mouse red cell membranes is increased over that of uninfected cells at both 24°C and 37°C. This was demonstrated by electron spin resonance spectroscopy using the hydrocarbon spin labels 2-dodecyl-2′,5,5′-trimethyloxazolidine-N-oxyl and 2-heptyl-2′ -hexyl-5,5′-dimethyloxazolidine-N-oxyl to label regions of the bilayer near its surface, and deeper within the hydrocarbon region, respectively. Arrhenius plots of the ‘empirical motion parameter’ (R_i) obtained from 2-heptyl-2′-hexyl-5,5′-dimethyloxazolidine-N-oxyl-labeled cells versus temperature over the range from 0 to 45°C showed an hysteretic behavior of the spin labels in the membranes of both mature and immature uninfected cells. Such hysteretic behavior was consistently lacking in membranes of infected cells. These differences in membrane fluidity and spin label behavior are interpreted to reflect biochemical modifications of the red cell membrane which occur with infection by the malarial parasite.     

Effects of parathyroid hormone and calcitonin on Na+, Cl−, K+, Mg2+ and Ca2+ transport in cortical and medullary thick ascending limbs of mouse kidney

The effect of parathyroid hormone (PTH) on transepithelial Na⁺, Cl^–, K⁺, Ca²⁺ and Mg²⁺ transport was investigated in isolated perfused cortical thick ascending limbs (cTAL) and that of human calcitonin (hCT) was tested in both cortical and medullary thick ascending limbs (mTAL) of the mouse nephron. The transepithelial ion net fluxes (J _x) were determined by electron probe analysis of the perfused and collected fluids. Simultaneously, the transepithelial voltage (PD_te) and resistance (R _te) were recorded. In cTAL segments, PTH and hCT significantly stimulated the reabsorption of Na⁺, Cl^–, Ca²⁺ and Mg²⁺. hCT generated a net K⁺ secretion towards the lumen and PTH tended to exert the same effect. Neither PD_te nor R _te were significantly altered by either PTH or hCT. However, in the post-experimental period a significant decrease in PD_te was noted. Time control experiments carried out under similar conditions revealed a significant decrease in PD_te with time, which could have masked the hormonal response. In mTAL segments, Mg²⁺ and Ca²⁺ transport was close to zero. hCT did not exert any detectable effect on either PD_te or J _Cl ^–, J _Na ⁺ J _K ⁺, J _Mg ²⁺ and J _Ca ²⁺ in these segments. In conclusion, our data demonstrate that PTH and hCT stimulate NaCl reabsorption as well as Mg²⁺ and Ca²⁺ reabsorption in the cTAL segment of the mouse. These data are in agreement with and extend data obtained in vivo in the rat.     

Psammoma bodies and optically clear nuclei in bronchiolo-alveolar cell carcinoma. Diagnosis by fine needle aspiration biopsy with histologic and ultrastructural confirmation

The fine needle aspiration cytology of two cases of bronchiolo-alveolar cell carcinoma of the lung having unusual features is reported. One case demonstrated numerous psammoma bodies in the cytologic smears, whereas the other case showed an abundance of cells with optically clear nuclei. Both peripherally located tumors were resected and confirmed as primary bronchiolo-alveolar cell carcinoma by histologic and ultrastructural examination. We believe this to be the first report describing these unusual features of bronchiolo-alveolar cell carcinoma diagnosed by fine needle aspiration cytology. Presented is a discussion of psammoma bodies and optically clear nuclei seen in primary and metastatic tumors of the lung. This will aid in the diagnosis of these cases.     

Ultrastructure,function and composition of smooth muscle

Filamentous myosin is present in both relaxed (myosin light chains unphosphorylated) and contracted (light chains phosphorylated) vascular smooth muscle. The organization of myosin and actin filaments and the insertion of the latter on cytoplasmic and plasma membrane bound dense bodies is consistent with a mini sarcomere-like organization and a sliding filament mechanism of contraction in smooth muscle. Mitochondria are high capacity, low affinity Ca stores in smooth muscle. They do not play a role in the regulation of cytoplasmic Ca²⁺ at physiological levels. The localization and Ca content of the junctional sarcoplasmatic reticulum (SR) is consistent with this organelle being the major intracellular source of activator Ca released by excitatory transmitters. Repeated contractions in the absence of extracellular Ca²⁺ (thought to represent recycling of intracellular activator Ca²⁺) can be demonstrated if the excitatory agent is not allowed to remain in contact with the smooth muscle throughout relaxation; the demonstration of “recycling” is facilitated if the efflux of cellular Ca²⁺ is blocked. The rise in total cytoplasmic calcium measured with electron probe analysis during a maintained (30 min) contracture in rabbit portal-anterior mesenteric vein smooth muscle (∼0.9 mmol/kg dry cytoplasm) is greater than the amount of Ca that could be bound to calmodulin.     

“Dark” (compacted) neurons may not die through the necrotic pathway

Dark neurons were produced in the cortex of the rat brain by hypoglycemic convulsions. In the somatodendritic domain of each affected neuron, the ultrastructural elements, except for disturbed mitochondria, were remarkably preserved during the acute stage, but the distances between them were reduced dramatically (ultrastructural compaction). Following a 1-min convulsion period, only a few neurons were involved and their environment appeared undamaged. In contrast, 1-h convulsions affected many neurons and caused swelling of astrocytic processes and neuronal dendrites (excitotoxic neuropil). A proportion of dark neurons recovered the normal structure in 2 days. The non-recovering dark neurons were removed from the brain cortex through two entirely different pathways. In the case of 1-h convulsions, their organelles swelled, then disintegrated and finally dispersed into the neuropil through large gaps in the plasma membrane (necrotic-like removal). Following a 1-min convulsion period, the non-recovering dark neurons fell apart into membrane-bound fragments that retained the compacted interior even after being engulfed by astrocytes or microglial cells (apoptotic-like removal). Consequently, in contrast to what is generally accepted, the dark neurons produced by 1-min hypoglycemic convulsions do not die as a consequence of necrosis. As regards the case of 1-h convulsions, it is assumed that a necrotic-like removal process is imposed, by an excitotoxic environment, on dark neurons that previously died through a non-necrotic pathway. Apoptotic neurons were produced in the hippocampal dentate gyrus by intraventricularly administered colchicine. After the biochemical processes had been completed and the chromatin condensation in the nucleus had reached an advanced phase, the ultrastructural elements in the somatodendritic cytoplasm of the affected cells became compacted. If present in an apparently undamaged environment such apoptotic neurons were removed from the dentate gyrus through the apoptotic sequence of morphological changes, whereas those present in an impaired environment were removed through a necrotic-like sequence of morphological changes. This suggests that the removal pathway may depend on the environment and not on the death pathway, as also assumed in the case of the dark neurons produced by hypoglycemic convulsions.     

Substantia nigra damage induced by ischemia in hyperglycemic rats

Summary Preischemic hyperglycemia induced by feeding or glucose infusion worsens the brain damage and the clinical outcome following ischemia of a given duration and density, and characteristically causes postischemic seizure activity. Light microscopy has previously showed that, in the rat, transient hyperglycemic ischemia induced by bilateral carotid occlusion in combination with arterial hypotension causes a uni- or bilateral lesion in the pars reticulata of the substantia nigra. Since this region has a central role in preventing seizure discharges the present study was carried out to determine the ultrastructural characteristics of this lesion. In rats with 10 min of transient hyperglycemic ischemia followed by recirculation for 1 to 18 h, the pars reticulata of the substantia nigra showed signs of status spongiosus, as well as extensive nerve cell alterations. These changes were observed after all recovery periods studied. The spongiotic appearance was mainly caused by swelling of dendrites and, to a lesser degree, by astrocytic swelling. The dendrites were expanded at all recovery times but the severity increased during the later periods of recirculation. These swollen dendrites contained severely expanded mitochondrias and endoplasmic reticulum. The cytoskeletal elements showed disordered lining of microtubules. Two major types of nerve cell alterations were present: a pale and a dark variety. The pale type was the most frequent cell alteration. It occurred in all experimental groups and at all time points. Redistribution of the nuclear chromatin and of cytoplasmic organelles as well as swelling of the same type as in the dendrites were the essential changes. The dark neurons were much fewer in number and occupied a peripheral position in the pars reticulata. Astrocytic foot processes appeared to be dilated around the dark neurons. Swelling of astrocyte processes was most pronounced in the 1 h recovery animals. Both types of neurons showed severe mitochondrial alterations of the type observed in dendrites. Occasionally, mitochondrial alterations were found in astrocytic processes as well. Blood vessel alterations were lacking. Previous studies have shown that in this model of ischemia the substantia nigra has a relatively well-preserved blood perfusion. In view of this the extensive histopathological lesions are surprising. We speculate that the lesions primarily involve excitotoxic damage to dendrites, with pronounced lactic acidosis playing a contributory role in causing axonal and glial pathology as well.Supported by grants from the Swedish Medical Research Council (project 12X-03020 and project 14X-263) and from the U.S. Public Health Service via the N.I.H. (grant No. 5 RO1 NS07838)     

Transplantation of Pacinian corpuscles of the rat into the brain

Summary In adult inbred rats of the AVN strain, branches of the crural interosseous nerve were dissected out from donors and transplanted into the brain of recipients, together with a cluster of Pacinian corpuscles, (either into a suction cavity or the cerebral cortex) into a slit 1–2 mm deep. The grafts were fixed and processed for electron microscopy 10 days to 6 months after the operation, and their ultrastructure was examined. Sporadic axons of small diameter grew into the nerve branches of some of the grafts from 11 days onward, and became myelinated during the 2nd month after the operation, but none of the transplanted Pacinian corpuscles became reinnervated. The corpuscles, however, survived denervation and grafting. Most of them retained a well-preserved inner core and an intact capsule, consisting of a normal complement of 29.2±1.0 (mean ±SE) capsular layers (n=8), as did the corpuscles previously examined after denervation in situ. Some of the corpuscles underwent degenerative changes, presumably due to a delayed or restricted revascularization. In this group of corpuscles, the inner core underwent disintegration and was gradually replaced by collagen fibrils, whereas the capsule remained preserved but the number of its layers eventually reduced by 40%. It is assumed that the lack of reinnervation of the grafted Pacinian corpuscles was due to the paucity of regenerating axons, and their failure to form correct projections along those Schwann cell columns connected with the corpuscles.     

Ultrastructure of carbon disulphide neuropathy

Summary Adult Wistar rats were exposed to carbon disulphide (CS₂) vapour at a concentration of 2.4 mg/l of air for 5 days a week (6h a day), and the ultrastructure of peripheral nerves, neuromuscular junctions and muscles was investigated after 6 months of exposure to CS₂. Numerous giant axons, i.e. paranodal or internodal swellings, were seen in the peripheral nerves. At the swollen paranodes, the myelin sheath was thinned, in other regions large intramyelinic vacuoles indicative of more dramatic demyelination were observed at axonal enlargements. Axonal enlargements consisted essentially of whorls of tightly packed neurofilaments. A number of nerve fibres underwent complete degeneration, but at the same time there was evidence of nerve regeneration. Nerve terminals were affected in a similar way following CS₂ exposure. At neuromuscular junctions, filamentous swellings of nerve terminals preceded their degeneration and eventual denudation of synaptic gutters. As a rule, the postsynaptic part of neuromuscular junctions remained unimpaired by CS₂ treatment. Muscles were affected by both atrophy and degeneration. Clusters of dense and lamellar bodies and numerous autophagosomes indicative of direct myotoxic effect of CS₂ were frequently encountered in the investigated muscles. Some muscle fibres apparently underwent necrosis judging from the occurrence of myotubes characteristic of muscle degeneration and regeneration.The pathomorphology of CS₂ neuropathy resembles that of other toxic neuropathies which presumably have a common origin in impaired energy metabolism.     

A possible paracellular route for the resolution of hydrocephalic edema

Summary Considering the possibility of a paracellular route for edema resolution we studied the microvasculature of the subependymal and subcortical white matter in hydrocephalic rats. Normal adult rats were used as controls. After injection of kaolin suspension into the cisterna magna, the animals were killed at intervals of 1, 2, 4, and 8 weeks. In hydrocephalic rats at 1 week after kaolin injection, widening of the interendothelical cleft between the tight junction (dehiscence) was seen in 27 of 76 (35%) vessels. At 2 weeks after kaolin injection, the number of the dehiscences had increased (39/7:56%) and some were enlarged, forming interendothelial blisters. At 4 weeks in hydrocephalic rats, both dehiscences and blisters were still prominent (45/7363%) and at 8 weeks the dehiscences were still prominent, but the number of the blisters had decreased (25/8131%). The blisters and dehiscences were most pronounced in the corpus callosum and occipital regions. Following i.v. injection of horseradish peroxidase, the interendothelial dehiscences and blisters were completely devoid of the marker substance. These findings indicate that in obstructive hydrocephalus the tight junctions may constitute part of a paracellular pathway for the resorption of interstitial edema fluid.