Lurcher mice exhibit potentiation of GABA(A)-receptor-mediated conductance in cerebellar nuclei neurons in close temporal relationship to Purkinje cell death

In heterozygous Lurcher mice (Lc/+), the Purkinje cells (PCs) degenerate almost totally during postnatal development. On the other hand, their projection target, the deep cerebellar nuclei (DCN), shows few signs of degeneration and seems to play an important role in maintaining a residual cerebellar function in Lc/+. We asked whether the DCN in Lc/+ develop cellular adaptations allowing them to cope with the loss of GABAergic PC input. Using whole-cell patch-clamp recordings, we measured inhibitory postsynaptic currents from DCN of Lc/+ and wild-type mice (WT). In experiments on phenotypically striking Lc/+ studied well after the onset of the PC degeneration, we found enlarged average synaptic conductances (g(syn)) compared with WT. We next investigated postnatal mice before and after the onset of PC death. In younger animals </= postnatal day (p) 13, no difference was found in g(syn) between the two groups. At p14, g(syn) in Lc/+ showed an increase, while those in WT stayed on the level found in younger animals. A peak-scaled nonstationary fluctuation analysis suggests that an increase in the average number of channels open at peak is the basis for the change in g(syn). The changes in g(syn), suitable to increase the efficacy of GABAergic transmission, occur in close temporal relationship to PC death and, thus, may reflect a functional adaptation to the loss of the DCN's main GABAergic afferents.

Efficacy and short-term plasticity at GABAergic synapses between Purkinje and cerebellar nuclei neurons

Although the entire output of the cerebellar cortex is conveyed to the deep cerebellar nuclei neurons (DCNs) via the GABAergic synapses established by Purkinje cells (PCs), very little is known about the strength and dynamic properties of PC-DCN connections. Here we show that activation of PC-DCN unitary connections induced large conductance changes (11.7 nS) in DCNs recorded in whole cell patch configuration in acute slices, suggesting that activity of single PCs might significantly affect the output of its target neurons. Based on the large unitary quantal content (18) inferred from calculations of PC-DCN quantal size (0.65 nS) and the near absence of failures in synaptic transmission during control conditions, we conclude that PC-DCN connections are highly multi-sited. The analysis of dynamic properties of PC-DCN synapses demonstrated remarkable paired pulse depression (PPD), maximal at short intervals (paired pulse ratio of 0.15 at 7-ms interval). We provide evidence that PPD is presynaptic in origin and release-independent. In addition, multiple pulse stimulation revealed that PC-DCN synapses exhibited larger sensitivity to dynamic than to steady signals. We postulate that the, otherwise paradoxical, combination of marked short-term depression with strong multi-sited connections is optimal to transfer dynamic information at unitary level by performing spatial average of release probability across the numerous release sites. This feature could enable these synapses to encode presynaptic time-varying signals of single PCs as moment-to-moment changes in synaptic strength, a capacity well suited to the postulated role of cerebellum in control of temporal aspects of motor or cognitive behaviors.

Trioxsalen in the presence of UVA is able to induce nuclear factor kappa B binding activity in HaCaT keratinocytes

It has been described that treatment of cells with high dose psoralen and UVA induce the production of reactive oxygen species (ROS) leading to DNA damage. Transcription factor nuclear factor kappa B (NFkappaB) plays a crucial role in regulating not only cell growth but also cell differentiation, and ROS seem to be partly involved in these mechanisms. The aim of this research was to find out the effect of a combined treatment with trioxsalen (TMP)/UVA on NFkappaB binding activity in HaCaT keratinocytes. HaCaT keratinocytes were treated with 27 microg/l TMP. This concentration did not affect the proliferation rates, nor was it toxic, as shown by cytotoxicity assays. After treatment with TMP with or without UVA (1 J/cm(2)), NFkappaB binding activity in nuclear protein extracts was measured by electrophoretic mobility shift assays. The effect on cytokines and cytokine receptor genes was investigated using cDNA expression arrays. An inhibitory effect on NFkappaB binding activity was found between 30 and 60 min after TMP supplementation of the culture media. UVA irradiation induced a 2-fold increase in NFkappaB binding activity in TMP supplemented HaCaT keratinocytes compared with the non-irradiated control. In addition, NFkappaB binding activity was higher after UVA irradiation with TMP than in UVA irradiated cells in the absence of TMP. TGF-alpha, IL-1R, IL-2Ralpha, IL-12beta and PDGF expression was induced by UVA. However, all of them except PDGF were inhibited by combined TMP/UVA treatment. Using an inhibitor of NFkappaB activation, we found out that under these conditions, these cytokines or cytokine receptor genes are apparently not regulated by NFkappaB. Our results indicate that a combined TMP/UVA treatment of HaCaT keratinocytes induces NFkappaB binding activity, and that this is a synergistic effect. The investigated cytokines, and cytokine receptor genes do not seem to be NFkappaB regulated; however, TMP shows anti-inflammatory capacities in vitro.

Effects of UVA and L-ascorbic acid on nuclear factor-kappa B in melanocytes and in HaCaT keratinocytes

Nuclear factor-kappaB (NFkappaB) is a pleiotropic transcriptional activator, which is a sensitive transcriptional factor for free radicals and activates multiple target genes. UVA is very efficient in inducing free radicals in human skin cells. L-ascorbic acid is regarded as a scavenger of UVA-induced free radicals in human keratinocytes. In epidermis, melanocytes and keratinocytes play an important protective role against skin photodamage. In the present study, we aimed to investigate the role of NFkappaB on photodamage in melanocytes and keratinocytes. Normal human melanocytes (NHM) and HaCaT keratinocytes were treated with UVA (500 mJ/cm(2), 1,000 mJ/cm(2)) and/or L-ascorbic acid (100 microM, 250 microM). NFkappaB binding activity was analysed by electrophoretic mobility shift assay. NFkappaB binding activity was increased by UVA irradiation in HaCaT keratinocytes, but it was not affected in NHM. On the other hand, L-ascorbic acid decreased NFkappaB binding activity both in UVA-irradiated and in non-irradiated NHM. In contrast, NFkappaB binding activity in HaCaT keratinocytes was increased after treatment with L-ascorbic acid. In addition, L-ascorbic acid synergistically induced NFkappaB binding activity with UVA irradiation. The contrary response on NFkappaB binding activity in NHM and HaCaT keratinocytes indicated that the redox regulation might be different on photoprotective action in melanocytes and keratinocytes.

Serotonergic control of cerebellar mossy fiber activity by modulation of signal transfer by rat pontine nuclei neurons

Serotonergic modulation of precerebellar nuclei may be crucial for the function of the entire cerebellar system. To study the effects of serotonin (5-HT) on neurons located within the pontine nuclei (PN), the main source of cerebellar mossy fibers, we performed standard intracellular recordings from PN neurons in a slice preparation of the rat pontine brain stem. Application of 5 microM 5-HT significantly altered several intrinsic membrane properties of PN neurons. First, it depolarized the somatic membrane potential by 6.5 +/- 3.5 mV and increased the apparent input resistance from 49.5 +/- 14.6 to 62.7 +/- 21.1 MOmega. Second, 5-HT altered the I-V relationship of PN neurons: it decreased the inward rectification in hyperpolarizing direction, but increased it when depolarizing currents were applied. Third, it decreased the rheobase from 0.32 +/- 0.14 to 0.24 +/- 0.14 nA without affecting the firing threshold. Finally, the amplitude of medium-duration after hyperpolarizations was reduced from -14.9 +/- 2.0 to -12.3 +/- 2.4 mV. Together, these 5-HT effects on the intrinsic membrane properties result in an increase in excitability and instantaneous firing rate. In addition, application of 5 microM 5-HT also modulated postsynaptic potentials (PSPs) evoked by electric stimulations within the cerebral peduncle. The amplitude, maximal slope, and integral of these PSPs were reduced to 46.2 +/- 23.4%, 45.7 +/- 23.7%, and 61.4 +/- 28.4% of the control value, respectively. In contrast, we found no change in the decay and voltage dependence of PSPs. To test modulatory effects on short-term synaptic facilitation, we applied pairs of electrical stimuli at intervals between 10 and 1,000 ms. 5-HT selectively enhanced the paired-pulse facilitation for interstimulus-intervals >20 ms. The alteration of paired-pulse facilitation points to a presynaptic site of action for 5-HT effects on synaptic transmission. Pharmacological experiments suggested that pre- and postsynaptic effects of 5-HT were mediated by two different kinds of 5-HT receptors: changes in intrinsic membrane properties were blocked by the 5-HT(2) receptor antagonist cinanserin while the reduction of PSPs was prevented by the 5-HT(1) receptor antagonist cyanopindolol. In conclusion, 5-HT increases the excitability of PN neurons but decreases the synaptic transmission on them. The selective enhancement of synaptic facilitation may, however, allow high-frequency inputs to effectively drive PN neurons, thus the PN may act as a high-pass filter during periods of 5-HT release.

MEA-Tools: an open source toolbox for the analysis of multi-electrode data with MATLAB

Recent advances in electrophysiological techniques have created new tools for the acquisition and storage of neuronal activity recorded simultaneously with numerous electrodes. These techniques support the analysis of the function as well as the structure of individual electrogenic cells in the context of surrounding neuronal or cardiac network. Commercially available tools for the analysis of such data, however, cannot be easily adapted to newly emerging requirements for data analysis and visualization, and cross compatibility between them is limited. In this report we introduce a free open source toolbox called microelectrode array tools (MEA-Tools) for the analysis of multi-electrode data based on the common data analysis environment MATLAB (version 5.3-6.1, The Mathworks, Natick, MA). The toolbox itself is platform independent. The file interface currently supports files recorded with MCRack (Multi Channel Systems, Reutlingen, Germany) under Microsoft Windows 95, 98, NT, and 2000, but can be adapted to other data acquisition systems. Functions are controlled via command line input and graphical user interfaces, and support common requirements for the analysis of local field potentials, extracellular spike activity, and continuous recordings, in addition to supplementary data acquired by additional instruments, e.g. intracellular amplifiers. Data may be processed as continuous recordings or time windows triggered to some event.

Tight junction proteins: a novel class of integral membrane proteins. Expression in human epidermis and in HaCaT keratinocytes

Tight junction proteins comprise a novel group of integral membrane proteins necessary for cell-to-cell contacts and responsible for the barrier function in epithelial and endothelial cells in various tissues. The tight junction membrane domain contains at least three distinct proteins, named occludin, claudin and junctional adhesion molecule. Claudins are products of a gene family consisting of more than 20 members. We investigated mRNA expression of occludin and 13 different claudins in neonatal foreskin, adult skin and cultivated HaCaT keratinocytes by the Northern blot technique, and performed immunohistochemical staining of adult skin for occludin, claudin 1 and claudin 2. Occludin, claudin 1 and claudin 3 mRNAs were expressed in human neonatal and adult keratinocytes as well as in HaCaT keratinocytes. All other tested claudins were negative. Immunohistochemical staining of adult skin was positive for occludin in the intercellular space of the granular layer, and for claudin 1 in the inter-cellular space of the spinosum layer and basal layer, but negative for claudin 2 in all skin layers. Claudin 1 was also positive in the outer root sheath of hair follicles. Our results indicate that occludin, claudin 1 and claudin 3 are involved in cell-to-cell contacts between keratinocytes in human epidermis, although their functional importance remains unknown.

Early investigation of silver-coated Silzone heart valves prosthesis in 126 patients

BACKGROUND AND AIM OF THE STUDY

Permanent silver (Silzone) coating of the sewing cuff of St. Jude Medical prosthetic heart valves may reduce the rate of prosthetic valve endocarditis (PVE). However, the incidence of paravalvular leaks and stroke in patients after implantation of Silzone-coated heart valve prostheses is largely unknown.

METHODS

Complications were analyzed among 126 consecutive patients (78 males, 48 females; mean age 64.7 years; range: 40-80 years) who received Silzone-coated prostheses at our institution between February 1998 and December 1999. Among patients, 94 had aortic valve replacement, 29 mitral valve replacement, and three had aortic and mitral valve replacement. Concomitant cardiac procedures (mainly coronary bypass) were performed in 47 patients (37.3%).

RESULTS

Hospital mortality was 1.6% (2/126) and freedom from valve-related mortality 99.2+/-0.9%. Total follow up was 137.4 patient-years, and 98.4% complete. Strokes or transitory ischemic attacks (TIAs) occurred in four cases (two strokes, two TIAs; stroke rate 1.5%/year; 95% CI 0.4-2.6%/year; stroke+TIA rate 3%/year; 95% CI 0.4-5.25%/year). There was no case of prosthetic valve dysfunction or PVE. Freedom from reoperation due to procedure-associated complications was 97.6% (one aortic dissection, two major bleeds). Paravalvular leak was detected in 19 cases, and graded trivial or mild in 17 cases (11 grade 0-I, six grade I), and moderate in two cases (grade I-II in one, grade II in one). No patient needed reoperation due to paravalvular leak. Left ventricular (LV) function was normal in 80 cases, but was impaired mildly in 20 cases, moderately in 16, and severely in eight. Bicycle exercise testing in 92 patients (73%) showed median exercise performance (81.4+/-23.9% of normal) after correction for age and weight. Cerebral magnetic resonance imaging was performed in 64 patients (50.8%); median MRI score was 2.0+/-1.8 according to a 12-scaled score system.

CONCLUSION

The overall incidence of echocardiographic paravalvular leak graded more than trivial or mild was low (1.6%) in patients followed for a mean of 1.1+/-0.5 years (range: 1-27 months) after valve replacement with Silzone-coated heart valve prostheses. No patient required reoperation due to paravalvular leak; moreover, the stroke rate (1.5%/year) was low in these patients. The present data indicated no significant disadvantages or higher rate of complications related to silver coating compared with other, non-silver-coated prostheses. Future investigation is needed to determine long-term outcome.

Dynamic modulation of mossy fiber system throughput by inferior olive synchrony: a multielectrode study of cerebellar cortex activated by motor cortex

We investigated the effects of climbing fiber synchrony on the temporal dynamics of mossy fiber system throughput in populations of cerebellar Purkinje cells (PCs). A multielectrode technique was used in ketamine-anesthetized rats that allowed both complex and simple spikes (CSs and SSs) to be recorded from multiple PCs simultaneously in lobule crus IIa. Stimulation of the tongue area of the primary motor cortex (TM1) was used to evoke cerebro-cerebellar interaction. At the single PC level, robust short-term interactions of CSs and SSs were observed after TM1 stimulation that typically consisted of an immediate depression and subsequent enhancement of SS firing after the occurrence of a CS. Such modulations of SS rate in a given PC were as robustly correlated to the CSs of simultaneously recorded PCs as they were to the CS on its own membrane-and did not require a CS on its own membrane-indicating a network basis for the interaction. Analyses of simultaneously recorded PCs using the normalized joint perievent time histogram demonstrated that CS and SS firing were dynamically correlated after TM1 stimulation in a manner that indicated strong control of mossy fiber system throughput by CS synchrony. For < or =300 ms after TM1 stimulation, most PCs showed episodic modulations in SS rate that appeared to be entrained by the population rhythm of climbing fiber synchrony. SS rhythmicity also was modulated dynamically by CSs, such that it was depressed by CSs and facilitated by their absence. Like the modulations in SS rate, a given PC's modulation in SS rhythmicity did not require it to fire a CS but was, on those instances, equally correlated to the synchronous CSs of other PCs. The data indicate that the climbing fiber system controls the temporal dynamics of SS firing in populations of PCs by using synchrony to engage intracerebellar circuitry and modulate mossy fiber system throughput.

Regulation of renal tubular cell apoptosis and proliferation after ischemic injury to a solitary kidney

The time course and regulation of apoptosis and cellular regeneration after 30 minutes of acute ischemic injury to a single kidney was elucidated in rats at five time points over 20 weeks. The fraction of apoptotic cells was most prominent at 1 day after the insult in the distal tubule (8% +/- 4% vs 0% +/- 0%, acute renal failure [ARF] vs sham, respectively) and was still elevated at 7 days (2% +/- 2% vs 0% +/- 0%). At that time, the whole kidney mRNA expression of the apoptosis inhibitory genes bcl-xL and bcl-2, as well as that of the apoptosis promotor bax, was significantly reduced. Immunohistochemistry of kidney specimen showed suppression of bcl-2 in the distal tubule but up-regulation in the proximal tubule, whereas bax protein was more strongly expressed in the distal tubule. Cellular proliferation started at day 1 and continued over the following 20 weeks, leading to severe tubular dilation and kidney failure. These data indicate that differential regulation of bcl-2 family members contributes to the early apoptotic clearance of lethally injured tubular epithelial cells after ischemic injury to a solitary kidney.

Virulence-associated genes in avian pathogenic Escherichia coli (APEC) isolated from internal organs of poultry having died from colibacillosis

Escherichia coli infections are responsible for significant losses in the poultry industry in many parts of the world. The pathogenesis and the role of virulence factors are not yet totally elucidated. We, therefore, examined 150 E. coli strains isolated from visceral organs of poultry having died from colibacillosis for the presence of virulence-associated genes by PCR. The E. coli strains were investigated for the presence of a total of 17 virulence-associated genes described for diarrheagenic (stx1/2, eae, hlyEHEC, estl, eltI, astA, cdtb), septicemic (hlyA, papC, cnf1/2, fyuA, irp2) and avian pathogenic E. coli (APEC; iucD, tsh, fimC, and hlyE as well as stx2f). Seven genes were significantly distributed among APEC strains, while most of the other investigated genes could be demonstrated only sporadically or not at all. FimC (Type I fimbriae) was detected with the highest prevalence in 92.7% of the isolates. Most of the strains harboring iucD (88.7%) also gave positive results for tsh (85.3%). Genes fyuA (ferric yersiniabactin uptake) (66.0%) and irp2 (iron-repressible protein) (68.0%), necessary for Yersinia to acquire iron in the mouse infection model, were regularly detected in combination. Moreover, we found papC (pyelonephritis-associated pili) in 30.0% and astA (enteroaggregative heat stable toxin) in 17.3% of the field strains. A significant amount of strains (57.3%) harbored a combination of iucD, tsh, fimC, fyuA and irp2 virulence-associated genes, presumably rendering these strains particularly virulent. These findings provide novel insights into the presence and distribution of virulence-associated genes in avian pathogenic E. coli field strains, which will help to more comprehensively characterize APEC in future epidemiological studies. It is assumed that the existence of two iron acquisition systems points towards their important role in virulence. Furthermore, we suggest that characterization of the respective phenotypes in infection models will provide substantial information to better understand the pathogenesis of colibacillosis in poultry.

Characterization of antiapoptotic activities of Chlamydia pneumoniae in human cells

Chlamydia pneumoniae is an obligate intracellular bacterium which frequently causes airway infection in humans and has been implicated in atherosclerosis. Here we show that infection with C. pneumoniae protects HeLa human epithelioid cells against apoptosis induced by external stimuli. In infected HeLa cells, apoptosis induced by staurosporine and CD95-death-receptor signaling was strongly reduced. Upon treatment with staurosporine, generation of effector caspase activity, processing of caspase-3 and caspase-9 and cytochrome c redistribution were all profoundly inhibited in cells infected with C. pneumoniae. Bacterial protein synthesis during early infection was required for this inhibition. Furthermore, cytochrome c-induced processing and activation of caspases were inhibited in cytosolic extracts from infected cells, suggesting that a C. pneumoniae-dependent antiapoptotic factor was generated in the cytosol upon infection. Infection with C. pneumoniae failed to induce significant NF-kappaB activation in HeLa cells, indicating that no NF-kappaB-dependent cellular factors were involved in the protection against apoptosis. These results show that C. pneumoniae is capable of interfering with the host cell's apoptotic apparatus at probably at least two steps in signal transduction and might explain the propensity of these bacteria to cause chronic infections in humans.

Effects of CYP7A1 overexpression on cholesterol and bile acid homeostasis

The initial and rate-limiting step in the classic pathway of bile acid biosynthesis is 7alpha-hydroxylation of cholesterol, a reaction catalyzed by cholesterol 7alpha-hydroxylase (CYP7A1). The effect of CYP7A1 overexpression on cholesterol homeostasis in human liver cells has not been examined. The specific aim of this study was to determine the effects of overexpression of CYP7A1 on key regulatory steps involved in hepatocellular cholesterol homeostasis, using primary human hepatocytes (PHH) and HepG2 cells. Overexpression of CYP7A1 in HepG2 cells and PHH was accomplished by using a recombinant adenovirus encoding a CYP7A1 cDNA (AdCMV-CYP7A1). CYP7A1 overexpression resulted in a marked activation of the classic pathway of bile acid biosynthesis in both PHH and HepG2 cells. In response, there was decreased HMG-CoA-reductase (HMGR) activity, decreased acyl CoA:cholesterol acyltransferase (ACAT) activity, increased cholesteryl ester hydrolase (CEH) activity, and increased low-density lipoprotein receptor (LDLR) mRNA expression. Changes observed in HMGR, ACAT, and CEH mRNA levels paralleled changes in enzyme specific activities. More specifically, LDLR expression, ACAT activity, and CEH activity appeared responsive to an increase in cholesterol degradation after increased CYP7A1 expression. Conversely, accumulation of the oxysterol 7alpha-hydroxycholesterol in the microsomes after CYP7A1 overexpression was correlated with a decrease in HMGR activity.

Apolipoprotein E epsilon 4 is associated with rapid progression of multiple sclerosis

OBJECTIVE

The apolipoprotein E (APOE) polymorphism is known to impact on various neurologic disorders and has differential effects on the immune system and on CNS repair. Previous findings concerning a possible modulation of the clinical course of MS have been inconsistent, however.

METHODS

In a cross-sectional study, the authors investigated 374 patients with clinically definite MS and a disease duration of at least 3 years and related their clinical and demographic findings to the allelic polymorphism of the APOE gene. The genotype distribution of patients with MS was compared with a cohort of 389 asymptomatic, randomly selected elderly volunteers.

RESULTS

The authors found no significant differences in the distribution of genotypes between patients with MS and controls. However, patients with MS with the epsilon4 allele (n = 85) had a significantly higher progression index of disability (0.46 +/- 0.4 versus 0.33 +/- 0.26; p < 0.004) and a worse ranked MS severity score (5.1 +/- 1.9 versus 5.7 +/- 1.7; p = 0.05) than their non-epsilon4 counterparts, despite significantly more frequent long-term immunotherapy in epsilon4 carriers (74% versus 58%; p < 0.007). The annual relapse rate in epsilon4 carriers (0.87 +/- 0.56) was significantly higher than in patients with MS without an epsilon4 allele (0.71 +/- 0.47; p = 0.03).

CONCLUSIONS

These results suggest no effect of the APOE genotype on susceptibility to MS, but indicate an association of the APOE epsilon4 allele with a more severe course of the disease.

Two types of neurons in the rat cerebellar nuclei as distinguished by membrane potentials and intracellular fillings

Classically, three classes of neurons in the cerebellar nuclei (CN), defined by different projection targets and content of transmitters, have been distinguished. However, evidence for different types of neurons based on different intrinsic properties is lacking. The present study reports two types of neurons defined mainly by their intrinsic properties, as determined by whole-cell patch recordings. The majority of cells (type I, n = 63) showed cyclic burst firing whereas a small subset (type II, n = 7) did not. Burst firing was used to distinguish the two types of neurons because, as it turned out, pharmacological interference could not be used to convert the non-bursting cells to bursting ones. Some of the membrane potentials exclusively present in type I neurons, such as sodium and calcium plateau potentials, low-threshold calcium spikes, and a slow calcium-dependent afterhyperpolarization, were found to contribute to the generation of burst firing. Other membrane potentials of type I neurons were not obviously related to the generation of bursts. These were 1) the lower amplitude and width of the action potential during spontaneous activity, 2) a sequence of afterhyperpolarization-afterdepolarization-afterhyperpolarization following each spike, and 3) the high spontaneous firing rate. In contrast, type II neurons lacked slow plateau potentials and low threshold spikes. Their action potentials showed higher amplitude and width and were followed by a single deep afterhyperpolarization. Furthermore, they showed a lower firing rate at rest. In both types of neurons, a delayed inward rectification was present. Neurons filled with neurobiotin revealed that the sizes of the somata and dendritic fields of type I neurons comprised the whole range known from Golgi studies, whereas those of the few type II neurons recovered were found to be in the lowest range. In view of their size and scarcity, we propose that type II neurons may correspond to CN interneurons.

Spatial arrangement of cerebro-pontine terminals

Understanding the interaction of the cerebral cortex and cerebellum requires knowledge of the highly complex spatial characteristics of cerebro-cerebellar signal transfer. Cerebro-pontine fibers from one neocortical site terminate in several sharply demarcated patches across large parts of the pontine nuclei (PN), and fibers from different neocortical areas terminate in the same pontine region. To determine whether projections from segregated neocortical sites overlap in the PN, we studied double anterograde tracing of cerebro-pontine terminals from large parts of rat neocortex. In none of these experiments, including double injection into two functionally related areas, were we able to demonstrate overlapping patches, although close spatial relationships were always detected. This non-overlapping distribution is consistent with a compartmentalized organization of the cerebro-pontine projection and may be the basis of the fractured type of maps found in the cerebellar granular layer. The critical distance between two sites on the neocortical surface that project to non-overlapping patches in the PN was found to be 600 microm, by using double injection within the whisker representation of the primary somatosensory area. This matches the diameter of dendritic trees of layer 5 projection neurons, indicating that non-overlapping populations of neocortical projection neurons possess non-overlapping patches of pontine terminals. Estimations based on this critical distance and the pontine volume anterogradely labeled by one injection site indicate that the size of the PN may be well suited to accommodate a complete set of non-overlapping pontine patches from all possible neocortical sites.

The contribution of adhesion molecule expression in donor kidney biopsies to early allograft dysfunction

BACKGROUND

Renal allograft rejection is associated with the expression of adhesion molecules on vascular endothelial and tubular epithelial cells.

METHODS

To assess whether the number of cell adhesion molecules expressed in donor kidneys can predict early rejection or delayed graft function, kidney biopsies from 20 living and 53 cadaveric kidney donors were obtained before engraftment into the recipients and the expression of the cell adhesion molecules intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and endothelial leukocyte adhesion molecule (E-selectin) were determined by immunohistochemistry.

RESULTS

All biopsies from living donors showed significantly lower expression of ICAM-1 and VCAM-1 compared to biopsies from cadaveric donors. There was no difference in the expression of adhesion molecules on tubular cells between transplants with primary function compared to allografts with early rejection in living donated kidneys (ICAM-1: 2+/-8 vs. 3+/-8%; VCAM-1: 9+/-7 vs. 1+/-1%), as well as in cadaveric kidneys (ICAM-1: 38+/-29 vs. 39+/-38%; VCAM-1: 55+/-27 vs. 48+/-29%). The expression of ICAM-1 molecules on tubular cells was determined to be a predictor for the occurrence of delayed graft function in cadaveric kidneys (ICAM-1: 65+/-24* vs. 38+/-29% delayed graft versus primary graft function). No delayed graft function occurred in recipients of living donated kidneys.

CONCLUSIONS

These data suggest that adhesion molecule expression in donor biopsies is not a predictor for early allograft rejection, but can be used as a marker for the development of postischemic acute renal allograft failure.

[Tracheostomy valve with integrated cough flap for improving hands-free speech in laryngectomized patients--development and clinical applications]

BACKGROUND

Following successful voice restoration after laryngectomy either by a voice prosthesis, a surgical shunt or microvascular laryngoplasty, a further goal in rehabilitation is the insertion of a tracheostoma valve, which enables the patient to speak without using his fingers for closure of the tracheostoma. One important disadvantage of the tracheostoma valves, which are available today, is the necessity of removal of the valve in case of coughing, because the valve could be thrown from the stoma by the strong air flow during coughing. As many laryngectomies suffer from chronic bronchitis, this coughing problem is one of the reasons why only few patients could be provided with this useful aid.

METHOD

At the department of biomedical engineering of the faculty of medicine at the university of Groningen, the Netherlands, 1994 two prototypes of a tracheostoma valve with an integrated cough lid were developed. These devices contain two separate valve systems: the normal speaking valve and a special coughing valve, which opens at a certain air flow and closes automatically after the coughing attack. Thus no manipulations are necessary during coughing, the patient can speak undisturbed. The ADEVA company (Lübeck, Germany) undertook the industrial production of this new type of tracheostoma valve creating different modifications of the prototype #2.

PATIENTS

In four series with 6-8 patients per group the modified tracheostoma valves were tested clinically and the occurring faults or lack of correct function eliminated by small changes in the production.

RESULTS

Meanwhile a suitable model for routine use is available, which was tested in 30 patients so far. This suitability was achieved by improvements in the valve mechanism, the valve seal and the adjustment mechanisms for the individual pressure level of the speaking and the coughing valve.

CONCLUSION

The newly developed tracheostoma valve with integrated coughing lid (Window, ADEVA-medical Company, Lübeck, Germany) provides further improvement in speech rehabilitation of laryngectomies. The low acceptance of tracheostoma valves, which enable the patient to speak without using his fingers for closure of the tracheostoma, possibly may be raised by this new aid.

[Coronary artery bypass graft dysfunction--clinical presentation, laboratory and electrocardiographic parameters]

The recurrence of symptoms after coronary artery bypass surgery is often caused by bypass-dysfunction. In this study we tried to determine factors related to the long-term patency of arterial and venous bypass grafts. We evaluated all patients with bypass grafts undergoing coronary angiography in the year 1998 at our hospital (163 patients, mean age 67 years, mean interval since the operation 79 months, a total of 341 venous bypasses (VBP), 386 peripheral venous anastomoses and 85 arterial (LIMA = left internal mammarial artery) bypasses. The data were collected by a retrospective analysis of the hospital records. Statistics were performed using the Wilcoxon-Mann-Whitney-U test. After an interval of 53 months LIMA-bypasses were patent without stenosis in 92%. Symptoms were caused in only 2% by a dysfunction of the LIMA-graft. The patency of venous bypass grafts decreased with time (5 years after the operation 74% were patent without stenosis, 5-10 years 56%, more than 10 years 35%, p < 0.01). We found clear relations between the function of the venous grafts and the clinical presentation (patent grafts without stenosis in 43% with acute coronary syndromes, in 57% with stable angina [p = 0.08] and in 86% with atypical angina [p < 0.0001 for the difference between each of the first two and the last syndrome]), the resting-ECG (65% patent VBP without stenosis with normal ST-segments and 49% with abnormal ST-segments, p < 0.01), the body-mass-index (70% patent VBP without stenosis with a BMI < 25 and 56% with a BMI > 30, p = 0.05) and the erythrocyte sedimentation rate after 2 hours (79% patent VBP with an ESR < or = 20 mm vs. 64% with an ESR > 49 mm, p = 0.02). The function of VBP after coronary artery bypass graft (CABG)-procedure depends primarily upon the interval since the operation. In addition, we found correlations with clinical presentation, resting-ECG, body-mass-index and erythrocyte-sedimentation rate as a possible marker of inflammation in bypass-atherosclerosis. Therefore, inflammatory processes seem to play an important role in the development of venous graft dysfunction.

Diabetes mellitus and islet cell specific autoimmunity as adverse effects of immunsuppressive therapy by FK506/tacrolimus

The induction of diabetes has been recognised as adverse effect of the immunsuppressive drug FK506/Tacrolimus. The aim of this study was to clarify whether insulinopenia or insulin resistance dominates and whether islet cell autoantibodies are present in patients treated by FK506. We investigated 58 patients 1-3 years after liver transplantation while under therapy with FK506 or CsA and prednisolone (0-7.5 mg) for basal blood glucose levels and islet-cell specific autoantibodies. A subgroup of 20 patients on FK506, 10 patients on cyclosporin and 15 healthy volunteers were metabolically tested by oGTT. Five patients had diabetes pre-transplantation. After transplantation, 9/28 FK506-treated patients developed newly diagnosed diabetes compared to 0/25 cyclosporin-treated patients (p<0.01). Both patient groups showed significantly higher fasting blood glucose, insulin or C-peptide levels compared to controls. Through the oGTT, FK506-treated patients without diabetes, but not cyclosporin-treated patients, had higher C-peptide levels compared to controls (p<0.05). Five/32 patients on FK506 compared to 0/26 patients on cyclosporin (p<0.05) had islet cell specific autoantibodies, mainly ICA without GAD- or IA2-Ab, a feature described for latent autoimmune diabetes in adults. ICA positivity was correlated to the diabetes associated HLA haplotype DR4/DQ*0302 (p<0.05). Although the interpretation of our metabolic data in patients with concomitant liver disease and prednisolone therapy has limitations, we suggest insulin resistance caused by treatment with FK506. However, manifestation of diabetes was associated with relative insulinopenia rather than insulin resistance in patients on FK506. Immunsuppressive therapy by FK506 was not able to suppress islet cell autoimmunity, and may even induce it in genetically predisposed patients.

Impaired phosphate handling of renal allografts is aggravated under rapamycin-based immunosuppression

BACKGROUND

Impaired phosphate handling of the renal allograft is a common problem and of multifactorial origin. The aim of the study was to elucidate whether a rapamycin- or a mycophenolate-based immunosuppressive therapy aggravates the renal phosphate leak in kidney transplant recipients.

METHODS

Renal phosphate handling was determined in thirty-eight cadaveric allograft recipients, with good renal function at 8, 12, 20 and 28 weeks after transplantation. Nineteen patients (group 1) received triple immunosuppression with rapamycin, cyclosporine and prednisolone, nineteen other transplant recipients received mycophenolate mofetil, cyclosporine and prednisolone immunosuppression (group 2), and six healthy subjects (group 3) served as controls. After 12 weeks of stable graft function, group 1 patients were divided further into two subgroups. Ten patients were kept on their immunosuppressive regimen (group 1A), whereas the remaining nine randomly chosen subjects had their cyclosporine withdrawn; they were thus maintained on a dual immunosuppression regimen with prednisolone and a higher dosage of rapamycin (group 1B).

RESULTS

Renal phosphate reabsorption was significantly lower in group 1 at 8 and 12 weeks after transplantation as compared with groups 2 and 3. At 20 weeks after transplantation, patients with rapamycin-based immunosuppression (groups 1A and 1B) continued to exhibit hypophosphataemia and impaired renal phosphate handling. Group 1B had the lowest TmP/ GFR compared with all groups. At 28 weeks, renal phosphate reabsorption and plasma phosphate levels were no longer different between patient groups and controls.

CONCLUSION

These data suggest that rapamycin-based immunosuppression prolongs the phosphate leak of the allografted kidney, leading to low serum phosphate levels during the first weeks after transplantation.