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Studies with animal seizure models have indicated that changes in temporal and spatial expression of voltage-gated sodium channels may be important in the pathology of epilepsy. Here, by using in situ hybridisation with previously characterised subtype-selective oligonucleotide probes [Whitaker et al. (2000) J. Comp. Neurol. 422, 123-139], we have compared the cellular expression of all four brain alpha-subunit sodium channel mRNAs in "normal" and epileptic hippocampi from humans. Neuronal cell loss was observed in all regions of the hippocampus of diseased patients, indicating that sclerosis had occurred. Losses of up to 40% compared to post-mortem controls were observed which were statistically significant in all regions studied (dentate gyrus, hilus, and CA1-3). To assess mRNA levels of the different alpha-subtypes in specific subregions, control and diseased tissue sections were hybridised to subtype-specific probes. To quantify any changes in expression while allowing for cell loss, the sections were processed for liquid emulsion autoradiography and grain counts were performed on populations of individual neurones in different subregions. No significant differences were found in the expression of type I and VI mRNAs. In contrast, a significant down-regulation of type II mRNA was observed in the epileptic tissue in the remaining pyramidal cells of CA3 (71+/-7% of control, P<0.01), CA2 (81+/-8% of control, P<0.05) and CA1 (72+/-6% of control, P<0.05) compared with control tissue. Additionally, a significant up-regulation in type III mRNA in epileptic CA4 pyramidal cells (145+/-7% of control, P<0.05) was observed. It is not clear whether these changes play a causal role in human epilepsy or whether they are secondary to seizures or drug treatment; further studies are necessary to investigate these alternatives. However, it is likely that such changes would affect the intrinsic excitability of hippocampal neurones.

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Antisera directed against unique peptide regions from each of the human brain voltage-gated sodium channel alpha subunits were generated. In immunoblots these were found to be highly specific for the corresponding recombinant polypeptides and to recognise the native holoprotein in human brain membrane preparations. These antisera were used to perform a comparative immunohistochemical distribution analysis of all four brain sodium channel subtypes in selected human CNS regions. Distinct but heterogeneous distribution patterns were observed for each of the alpha subunits. In general, these were complimentary to that previously shown for the corresponding human mRNAs. A high degree of conservation with respect to the distribution found in rat was also evident. The human alpha subunit proteins exhibited distinct subcellular localisation patterns. Types I, III and VI immunoreactivity was predominantly in neuronal cell bodies and proximal processes, whereas type II was concentrated along axons. This is similar to rat brain and suggests the different the sodium channel subtypes have distinct functions which are highly conserved between human and rodents. A notable difference was that the type III protein was detected in all human brain regions examined, unlike in rat brain where expression in adults is very restricted. Also in contrast to rat brain, the human type VI protein was not detected in axons of unmyelinated neurons. These differences may reflect true species variation and could have important implications for understanding the function of the sodium channel subtypes and their roles in human disease.

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The type III voltage-gated sodium channel was cloned from human brain. The full-length cDNA has 89% identity with rat type III, and the predicted protein (1951 amino acids) has 55 differences. The expression pattern of human type III mRNA was determined in adult brain tissue and, in contrast to rat, was detected in many regions, including caudate nucleus, cerebellum, hippocampus and frontal lobe. The human type III channel was stably expressed in Chinese hamster ovary (CHO) cells and its biophysical properties compared to the human type II channel using identical conditions. The voltage dependence and kinetics of activation were found to be similar to that of type II. The kinetics of inactivation of the two human subtypes were also similar. However, type III channels inactivated at more hyperpolarized potentials and were slower to recover from inactivation than type II. When expressed in human embryonic kidney (HEK293T) cells, type III channels produced currents with a prominent persistent component, which were similar to those reported for rat type II [Ma et al. (1997) Neuron, 19, 443-452]. However, unlike type II, this was prominent even in the absence of coexpressed G-proteins, suggesting type III may adopt this gating mode more readily. The distinct properties of the channel, together with its wide distribution in adult brain, suggest that in humans, type III may have important physiological roles under normal, and perhaps also pathological conditions.

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The distribution of mRNAs encoding voltage-gated sodium channel alpha subunits (I, II, III, and VI) and beta subunits (beta1 and beta2) was studied in selected regions of the human brain by Northern blot and in situ hybridisation experiments. Northern blot analysis showed that all regions studied exhibited heterogenous expression of sodium channel transcripts. In situ hybridisation experiments confirmed these findings and revealed a predominantly neuronal distribution. In the parahippocampal gyrus, subtypes II and VI and the beta-subunit mRNAs exhibited robust expression in the granule cells of the dentate gyrus and pyramidal cell layer of the hippocampus. Subtypes I and III showed moderate expression in granule cells and low expression in the pyramidal cell layer. Distinct expression patterns were also observed in the cortical layers of the middle frontal gyrus and in the entorhinal cortex. In particular, all subtypes exhibited higher levels of expression in cortical layers III, V, and VI compared with layers I and II. All subtypes were expressed in the granular layer of the cerebellum, whereas specific expression of subtypes I, VI, beta1, and beta2 mRNAs was observed in Purkinje cells. Subtypes I, VI, and beta1 mRNAs were expressed, at varying levels, in the pyramidal cells of the deep cerebellar nuclei. These data indicate that, as in rat, human brain sodium channel mRNAs have a distinct regional distribution, with individual cell types expressing different compliments of sodium channels. The differential distribution of sodium channel subtypes suggest that they have distinct roles that are likely to be of paramount importance in maintaining the functional heterogeneity of central nervous system neurons.

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The efficacy of three hypertonic saline solutions for treating dialysis-induced hypotension in a randomized, blinded, crossover clinical trial of 10 patients (a minimum of three cycles per solution) was compared. Dialysis-induced hypotension, defined as a decrease in systolic blood pressure of at least 10 mm Hg or systolic blood pressure less than 100 mm Hg, was treated with an iv bolus of either 10 mL of 23% saturated hypertonic saline, 30 mL of 7.5% hypertonic saline, or 30 mL of 7.5% saline with 6% dextran 70, each containing similar osmolar loads of 80, 80, and 100 mosM, respectively. All three solutions raised systolic blood pressure within 5 min (mean pretreatment systolic blood pressure, 87 mm Hg; mean posttreatment systolic blood pressure, 101 mm Hg; P < 0.05). The magnitude of the increase was greater with saturated hypertonic saline (15 mm Hg) and dextran 70 (17 mm Hg) compared with that with hypertonic saline (9 mm Hg; P < 0.05). At 10 min, dialysis-induced hypotension was less frequent with saturated hypertonic saline (incidence, 9%) compared with hypertonic saline (45%). Beyond 10 min, however, there was a trend toward a lower incidence of further dialysis-induced hypotension with dextran 70. There were no side effects. Given equal osmole loads, the more concentrated solution produced a greater increase in systolic blood pressure. The addition of an oncotic agent such as dextran may prolong the blood pressure response beyond 10 min. It was concluded that hypertonic saline solutions safely and effectively treat dialysis-induced hypotension.

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Improved and reliable methods for assessing glomerular filtration rate (GFR) in intensive care patients are needed in light of known deficiencies using creatinine clearance. We compared simultaneous two-hour clearances of inulin (CIn), creatinine (CCr), and 99mTc-diethylenetriaminepentaacetic acid (CDTPA) in 18 medical or surgical intensive care patients (range, 49 to 92 years old) with blood urea nitrogen (BUN) levels greater than 17.9 mmol/liter (0.5 mg/ml), serum creatinine levels greater than 150 mumol/liter (0.02 mg/ml), or estimated Cockcroft clearance less than 60 ml/min. Patients had severe renal dysfunction with average GFR of 35 ml/min (range, 2 to 69 ml/min). CDTPA and CCr correlated significantly with CIn, although CDTPA tended to provide a closer approximation. Cockcroft clearance (32 +/- 4 ml/min) was grossly similar to CDTPA and CIn and correlated significantly, especially when weight was calculated using actual as opposed to ideal body weight. In a subset of 13 patients with CIn less than 30 ml/min, only CDTPA was significantly correlated with CIn. In patients in the intensive care unit, CDTPA provides a rapid, accurate, and inexpensive clinical assessment of GFR, even at very low GFRs.

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A patient with unilateral gross hematuria was found to have mesangial proliferation and IgM deposition on renal biopsy, consistent with the entity of primary renal hematuria. This case refutes previous assumptions that renal biopsy is normal in patients with unilateral hematuria. Glomerular lesions may be more common than previously suspected in the setting of unilateral hematuria. Renal biopsy can be useful both to define the natural history of unilateral hematuria and prevent repeated diagnostic procedures in patients with abnormal biopsies.

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