Tissue factor, its inhibitor, and the thrombogenicity of two new synthetic membranes

BACKGROUND: The aim of the study was to compare the effect of new high-flux hemodialysis membranes made from polyacrylonitrile (AN69ST) and polysulfone (Helixone) on the plasma levels of tissue factor (TF) and tissue factor pathway inhibitor (TFPI) playing a key role in hemostasis. Established thrombogenicity markers were also determined. METHODS: In a clinical prospective randomized study, 10 patients were examined using either membrane at the start and at minutes 15, 60, and 240 of hemodialysis. RESULTS: Increases in the plasma TF levels reached significance at the end of hemodialysis with both membranes, with the Helixone also after 15 min. TFPI levels tended to rise significantly from minute 15 onward while not differing from baseline at the end of the procedure. Judging by the increase in thrombin-antithrombin III complexes, both membranes significantly activated coagulation at the end of hemodialysis. Platelet factor 4 levels, released during thrombocyte and endothelial stimulation, were elevated from the start of procedures. There were no significant differences between the AN69ST and the Helixone in any of the assessed markers. CONCLUSIONS: The AN69ST and Helixone membranes do not differ in their effects on TF and TFPI or even in established thrombogenicity markers.     

Unilateral 5,7-dihydroxytryptamine lesions of the dorsal raphe nucleus (DRN) and rat rotational behaviour

A unilateral lesion in the dorsal raphe nucleus (DRN) resulted in a decreased concentration of 5-hydroxytryptamine (5-HT) in the ipsilateral striatum (CS), anterior cortex and substantia nigra (SN), a loss of [³H]5-HT uptake sites in the cortex and striatum and a selective in 5-HT turnover in the substantia nigra. The directly acting 5-HT agonist 5-methoxy-N,N-dimethyltryptamine induced contralateral turning behaviour in the lesioned animals, whilst the 5-HT releasing agent, p-chloroamphetamine, induced ipsilateral rotation. All rotational behaviour was blocked by haloperidol and the turning behaviour in response to 5-MeODMT was blocked by methysergide. The data presented suggest that the DRN innervates the SN and CS differentially and that nigral 5-HT receptors become supersensitive after denervation of the DRN-SN pathway.     

Hyoscine-resistant peristalsis in guinea-pig ileum

The effect of hyoscine on the peristaltic activity of the proximal and distal ileum of the guinea-pig was studied. Hyoscine strongly impaired peristalsis as indicated by the elevation of the threshold pressure and by the increased number of incomplete peristalses and blockades. Functional activity of the circular musculature was more markedly impaired. However, particularly in the distal ileum, complete peristalses occurred even after 70 min exposure to hyoscine at a concentration of 10^?6 g/ml. A tenfold increase in hyoscine concentration failed to producedfurther impairment of peristaltic activity and of the oral reflex contraction. The activity which remained in the presence of hyoscine was blocked by methysergide and by d-tubocurarine. The hypothesis is advanced that once the muscarinic receptors have been blocked, increased radial stretch of the circular coat results in activation of a separate, tetrodotoxin sensitive, excitatory nervous pathway, which is sufficient to maintain a discrete degree of peristaltic activity.     

Comparison of ultrastructural changes in proximal and distal segments of transected giant fibers of the cockroach Periplaneta americana

When the giant axons of the cockroach Periplaneta americana are transected the proximal segment (the part connected to the soma) regenerates by tip sprouting and the distal segment degenerates. The initial ultrastructural response (24-48 h post-transection) occurring in the cut ends of the proximal and distal segments are similar. This response includes the disappearance of neurotubules; appearance of amorphous material in the axoplasm and a gradual accumulation of large numbers of small mitochondria, vesicles of various sizes and smooth endoplasmic reticulum. The axolemma in the region of organelle accumulation invaginates and glial processes are present in the invagination. The similarity of the changes that occur in the cut ends of the proximal and distal segments indicates that the primary reaction to axotomy is of a local nature and does not depend on the soma. Two to four days after transection, the cut end of the distal axonal segment reveals signs of degeneration. These include the appearance of swollen mitochondria, lysosomes, myelinated bodies and shrinking of the axon. In addition there is a massive proliferation of glial processes around the degenerating axons. Sprouting from the tip of the proximal segment starts 5--7 days post axotomy. Sprouts were identified as profiles containing few neurotubules, many vesicles and abundant smooth endoplasmic reticulum. 'Growth cone-like' structures were identified. The ultrastructural reorganization of the cut end of the proximal segment is discussed in relation to changes in membrane properties of the regenerating tip, as previously described by us.     

Activities of enzymes of the hexose monophosphate pathway in nervous system tumors induced by ethylnitrosourea

Summary The activities of three enzymes of the hexose monophosphate pathway (HMP) were measured in frozen samples of rat cerebral cortex and ethylnitrosourea-induced tumors of the rat nervous system. Results show that in most tumors, adequate amounts of glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), and transketolase (TK) were present so as not to be ratelimiting for utilization of the HMP. When enzyme activities were expressed on the basis of fresh weight, TK was increased in most tumors as compared with cerebral cortex; G6PDH and 6PGDH were more variable, showing either higher or lower activities in tumors as compared to control. Tumors in general had a lower protein content than cerebral cortex. When activities were expressed in terms of this protein content, mean values for the dehydrogenases in all groups of tumors were higher than the average value in cortex, indicating that G6PDH and 6PGDH were spared in tumors relative to other proteins. TK activities in tumors, expressed in terms of cytosol protein were lower than or in the same range as cortex. Increased activities of HMP enzymes in some tumors indicated that the potential activity of the HMP in some (but not all) tumors of the nervous system is greater than that of cerebral cortex.     

Experimentally induced enlargement of the uncrossed retinotectal pathway in rats

The present experiments investigate the effects of neonatal lesions upon projection patterns of the uncrossed retinotectal pathway in albino rats. The results indicate that enlargement of the terminal field from one eye can be induced either by a contralateral optic tract lesion or by removal of the opposite eye at birth. The extent of the enlargement is more prominent in the latter case. If an optic tract lesion is accompanied by eye enucleation on the side ipsilateral to the tract lesion, the uncrossed retinotectal projection from the remaining eye will undergo further enlargement. However, optic fiber counts show that such an enlargement of the terminal field is not due to a significant increase in the number of uncrossed optic axons which contribute to the enlarged projection, but rather to an increased terminal arbor of individual axons (as shown by results from fiber counts). While a severe ganglion cell loss was observed in the retina contralateral to a tract lesion, a substantial population of cells persists in the ganglion cell layer and the number of cells appears much higher than the number of uncrossed optic axons arising from the same eye. The implications of these findings are discussed in relation to results reported in previous studies.     

Toxocara canis and lead alter consummatory behavior in mice

Ingestion of palatable and unpalatable solutions was measured in adult mice to which had been administered the common parasite of the dog, Toxocara canis alone, or in combination with lead. In addition, response to hot plate and susceptibility to electroconvulsive seizure were also measured. Results from the palatability test indicated that either lead or Toxocara may alter the mouse's mode of interacting with its environment. However, the two agents in combination interacted in their effects on consummatory behavior. Results from the hot plate and ECS measures were less clear with respect to how lead and/or Toxocara influence temperature reactivity and seizure susceptibility. Histological examination of the CNS in parasite infected animals revealed Wallerian Type degeneration of fiber pathways including the corpus callosum, olfactory tract, and cerebellar penduncles.     

AKT activation predicts outcome in breast cancer patients treated with tamoxifen

Oestrogen receptor (ERalpha) expression is a strong predictor of response to endocrine therapy. The PI3K/AKT/mTOR signal transduction pathway has been implicated in endocrine resistance in vitro. The present study was carried out to test the hypothesis that AKT activation mediates tamoxifen resistance in clinical breast cancer. Immunohistochemistry (IHC) using AKT1-3, pan-AKT, pAKT (Thr-308), pAKT (Ser-473), pER (Ser-167), and pHER2 antibodies was performed on 402 ERalpha-positive breast carcinomas from patients treated with tamoxifen. High pAKT (Ser-473) activity (p = 0.0406) and low AKT2 expression (p = 0.0115) alone, or in combination [high pAKT (Ser-473)/low AKT2; 'high-risk' patient group] (p = 0.0014), predicted decreased overall survival in tamoxifen-treated patients with ERalpha-positive breast cancers. There was no significant association between tumour levels of AKT expression or activity and disease-free survival (DFS); however, the 'high-risk' patient group was significantly more likely to relapse (p = 0.0491). During tamoxifen treatment, neither AKT2 nor pAKT predicted DFS. Finally, activation of AKT, via phosphorylation, was linked to activation of both HER2 and ERalpha in this patient cohort. The data presented here show that the PI3K/AKT/mTOR pathway is associated with relapse and death in ERalpha-positive breast cancer patients treated with tamoxifen, supporting in vitro evidence that AKT mediates tamoxifen resistance. Patients with a 'high-risk' expression profile were at increased risk of death (hazard ratio 3.22, p = 0.002) relative to 'low-risk' patients, highlighting the potential that tumour profiling, with multiple IHC markers predictive of therapeutic response, may improve patient selection for endocrine therapies, eg tamoxifen or aromatase inhibitor-based treatments.     

Cortical origin of functional recovery in the somatosensory cortex of the adult mouse after thalamic lesion

To study the degree and time course of the functional recovery in the somatosensory cortex (SI) after an excitotoxic lesion in the adult mouse thalamus, metabolic activity was determined in SI at various times points post-lesion. Immediately after the lesion, metabolic activity in the thalamically deafferented part of SI was at its lowest value but increased progressively at subsequent time points. This was seen in all cortical layers; however, layers I and Vb recovered more rapidly than layers II, III, IV, Va and VI. Removal of the mystacial whiskers corresponding to the deafferented area, 5 weeks after cortical recovery, produced a subsequent 32% drop in metabolic activity, demonstrating peripheral sensory activation of this part of the cortex. Tracing experiments revealed that the deafferented cortex did not receive a novel thalamic input but that cortico-cortical and contralateral barrel cortex projections to this area were reinforced. We conclude that the cortical functional recovery after a thalamic lesion is, at least partially, due to modified cortico-cortical and callosal projections to the deafferented cortical area.     

Entorhinal cortex entrains epileptiform activity in CA1 in pilocarpine-treated rats

Layer III neurons of the medial entorhinal cortex (mEC) project to CA1 via the temporoammonic pathway and exert a powerful feed-forward inhibition of CA1 pyramidal neurons. The present study evaluates the hypothesis that disrupted inhibition of CA1 pyramidal neurons causes an eased propagation of entorhinal seizures to the hippocampus via the temporoammonic pathway. Using a method to induce a confined epileptic focus in brain slices, we investigated the spread of epileptiform activity from the disinhibited mEC to CA1 in control and pilocarpine-treated rats that had displayed status epilepticus and spontaneous recurrent seizures. In pilocarpine-treated rats, the mEC showed a moderate layer III cell loss and an enhanced susceptibility to epileptiform discharges compared to control animals. Entorhinal discharges propagated to CA1 in pilocarpine-treated rats but not in controls. Disconnecting CA3 from CA1 did not affect the spread of epileptiform activity to CA1 excluding its propagation via the trisynaptic hippocampal loop. Mimicking the invasion of epileptiform discharges by repetitive stimulation of the temporoammonic pathway caused a facilitation of field potentials in CA1 that were contaminated by population spikes and afterdischarges in pilocarpine-treated but not control rats. Single cell recordings of CA1 pyramidal neurons revealed a dramatic loss of feed-forward inhibition and the occurrence of strong postsynaptic excitatory potentials in pilocarpine-treated rats. Excitatory responses in CA1 were characterized by multiple NMDA receptor-mediated afterdischarges and a strong paired-pulse facilitation in response to activation of the temporoammonic pathway. Our results suggest that, irrespective of the enhanced seizure-susceptibility of the mEC in epileptic rats, the loss of feed-forward inhibition and the enhanced NMDA receptor-mediated excitability CA1 pyramidal cells ease the spread of epileptiform activity from the mEC to CA1 via the temporoammonic pathway bypassing the classical trisynaptic hippocampal loop.