Novel KChIP2 isoforms increase functional diversity of transient outward potassium currents

Kv4.3 channels conduct transient outward K⁺ currents in the human heart and brain where they mediate the early phase of action potential repolarization. KChIP2 proteins are members of a new class of calcium sensors that modulate the surface expression and biophysical properties of Kv4 K⁺ channels. Here we describe three novel isoforms of KChIP2 with an alternatively spliced C-terminus (KChIP2e, KChIP2f) or N-terminus (KChIP2g). KChIP2e and KChIP2f are expressed in the human atrium, whereas KChIP2g is predominantly expressed in the brain. The KChIP2 isoforms were coexpressed with Kv4.3 channels in Xenopus oocytes and currents recorded with two-microelectrode voltage-clamp techniques. KChIP2e caused a reduction in current amplitude, an acceleration of inactivation and a slowing of the recovery from inactivation of Kv4.3 currents. KChIP2f increased the current amplitude and slowed the rate of inactivation, but did not alter the recovery from inactivation or the voltage of half-maximal inactivation of Kv4.3 channels. KChIP2g increased current amplitudes, slowed the rate of inactivation and shifted the voltage of half-maximal inactivation to more negative potentials. The biophysical changes induced by these alternatively spliced KChIP2 proteins differ markedly from previously described KChIP2 proteins and would be expected to increase the diversity of native transient outward K⁺ currents.     

Sensitivity of B16 melanoma sublines to lymphokine-activated killer cells as determined by 51Cr-release and clonogenic assays

The aim of this study was to compare the differential sensitivities of B16 melanoma sublines to LAK cells by means of the standard 51Cr release assay and a clonogenic assay, which measures both cell survival and proliferation. LAK cells, generated after 4 days incubation with 150 international units (IU)/ml of interleukin-2 (IL-2), showed both cytolytic and anti-proliferative activities against B16 targets. Using an 18 h 51Cr release assay, murine LAK cells showed the highest cytolytic activity against B16 parental cells compared to B16-F1, B16-F10, B16-FLR and B16-BL6 sublines at effector/target (E/T) ratios ranging from 6/1 to 100/1. Purified adherent LAK (A-LAK) cells showed greater cytolytic activity against B16 parental cells and other B16 sublines compared to LAK cells, but otherwise the pattern of reactivity was similar. Using a clonogenic assay, the surviving fraction of B16 parental cells co-cultivated with LAK cells decreased to 0 at an E/T ratio of 50/1, while a 400/1 ratio was required to achieve a similar reduction of B16-F1, B16-F10, B16-FLR, and B16-BL6 sublines. No differences in subline sensitivity were seen with the 51Cr release assay, but these were observed using the clonogenic assay. An inverse linear relationship existed between % surviving fraction, as determined by the clonogenic assay, and cytolytic activity, as determined by the 51Cr release assay. Our data indicate that the clonogenic assay can detect differences in target cell sensitivity that otherwise are undetectable by the standard 51Cr release assay. The clonogenic assay may prove useful in delineating the long-term anti-adherent and anti-proliferative properties of effector cells from their cytolytic activity.     

Histopathological aspects of Dengue-2 virus infected mice tissues and complementary virus isolation

The difficulty in studying dengue virus (DENV) infection in humans and in developing a virus vaccine is the absence of a suitable animal model which develops the full spectra of the Dengue haemorrhagic fever (DHF) and Dengue shock syndrome (DSS). Despite the fact that viruses have been found in various animal tissues, we isolated DENV from tissues of adult BALB/c mice, inoculated with DENV serotype 2 (DENV-2) obtained from human serum. Viruses were ultrastructurally identified and immunolocalized by immunofluorescence techniques in C6/36 mosquito cell cultures, inoculated with tissues (liver, lung, kidney and cerebellum) macerate supernatant from mice, 48 h post-infection (p.i.). These organs, collected at the same stage of infection, were examined histologically. The histopathological analysis revealed focal alterations in all tissues examined. Liver contained focal ballooned hepatocytes, but without modifying the average diameter of the majority of hepatocytes. Sinusoidal lumen was significantly diminished at this stage but portal and centrolobular veins became congested. Lungs exhibited hemorrhagic foci in the alveolar space, vascular congestion and focal alveolitis. Cerebellar tissue showed rare foci of neuronal compactation (Purkinje cells) and perivascular oedema. In kidneys it was observed an increase in glomerular volume with augmented endocapillary and mesangial cellularity, with reactivity to anti-IgM in all glomeruli of infected mice. In conclusion, DENV-2 was found in all tissues examined early in the evolution of infection. Presence of viruses in tissues has mainly led to hemodynamic alterations with generalized vascular congestion and increased permeability, and mast cell recruitment in lungs. The latter could participate in the vascular modifications in tissues.     

A prospective study of the accuracy of preoperative computed tomographic staging of patients with biopsy-proven rectal carcinoma

From June 1983 to January 1986, 91 patients with biopsy-proven adenocarcinoma of the rectum had computed tomographic scans of the pelvis performed before treatment as part of a "sandwich" radiotherapy-surgery regimen. Two experienced diagnostic radiologists performed locoregional staging of all scans according to the University of California at San Francisco criteria; one of these radiologists repeated this staging at a later time to test the reproducibility of a single observer. Staging was performed without the use of any other radiographic studies or of any clinical information except the patients' age, sex, and the diagnosis of rectal carcinoma, to test the value of computed tomographic scans alone for staging. Agreement between the two stagings performed by the first observer was 51 percent, and interobserver agreement was only 37 percent. Agreement with Dukes' staging was only 33 percent. Therefore, preoperative pelvic computed tomographic scanning of primary rectal adenocarcinoma should not be relied upon for staging or for the selection of patients for treatment options.     

Ultraviolet exposure in the environment of welding work sites

It has been checked if the "limits of the acceptable doses of ultraviolet radiation of monochromatic radiation at the workplace" (NIOSH-standard of USA) are adhered to in the vicinity of welders' work stations in a factory hall. For recording of UV-doses polysulphon films have been used. According to these investigations non-welders are exposed to doses of UV-radiation which exceed the limits recommended by about eight times. Clinical examinations of these persons showed chronic damage of the external parts of the eyes in a higher percentage than in a control group. It is pointed to the necessity of taking protective measures to shield persons working in the vicinity of welding job sites from ultraviolet radiation.     

Effects of taprostene,a stable prostacyclin analogue,on haemodynamics,platelet function and arachidonate metabolism in healthy volunteers

Summary In order to assess the effect of taprostene on haemodynamics, platelet function and arachidonate metabolism in 4 healthy volunteers an intravenous infusion of 25 ng · kg^–1 · min^–1 was given for 6 h.During the infusion period systolic blood pressure dropped from 130 to 111 mm Hg and diastolic blood pressure from 77 to 69 mm Hg. The heart rate rose from 77 to 84 beats/min.During the taprostene infusion the slope and height of the ADP and collagen induced platelet aggregation curves were significantly inhibited and the sensitivity of platelets to PGI₂ and PGE₁ was increased.Plasma and serum thromboxane B₂, conversion of exogenous radiolabelled arachidonic acid, WU-test, circulating endothelial cell count, concentration of platelet factor 4, -thromboglobulin, malondialdehyde and the PGI₂-synthesis stimulating plasma factor did not show any clear drug-related alteration.It is concluded that infusion of taprostene 25 ng · kg^–1 · min^–1 caused measurable inhibition of platelet function ex vivo.     

Enhanced survival of glioma bearing rats following boron neutron capture therapy with blood-brain barrier disruption and intracarotid injection of boronophenylalanine

Boronophenylalanine (BPA) has been used for boron neutron capture therapy (BNCT) of brain tumors in both experimental animals and humans. The purpose of the present study was to determine if the efficacy of BNCT could be enhanced by means of intracarotid (i.c.) injection of BPA with or without blood-brain barrier disruption (BBB-D) and neutron irradiation using a rat brain tumor model. For biodistribution studies, F98 glioma cells were implanted stereotactically into the brains of Fischer rats, and12 days later BBB-D was carried out by i.c. infusion of 25% mannitol (1.373 mOsmol/ml), followed immediately by i.c. administration of 300, 500 or 800 mg of BPA/kg body weight (b.w.). At the 500 mg dose a fourfold increase in tumor boron concentration (94.5 g/g) was seen at 2.5 hours after BBB-D, compared to 20.8 g/g in i.v. injected animals. The best composite tumor to normal tissue ratios were observed at 2.5 hours after BBB-D, at which time the tumor: blood (T: Bl) ratio was10.9, and the tumor: brain (T: Br) ratio was 7.5, compared to 3.2 and 5.0 respectively for i.v. injected rats. In contrast, animals that had received i.c. BPA without BBB-D had T: Bl and T: Br ratios of 8.5 and 5.9, respectively, and the tumor boron concentration was 42.7g/g. For therapy experiments, initiated 14 days after intracerebral implantation of F98 glioma cells, 500 mg/kg b.w. of BPA were administered i.v. or i.c. with or without BBB-D, and the animals were irradiated 2.5 hourslater at the Brookhaven Medical Research Reactor with a collimated beam of thermal neutrons delivered to the head. The mean survival time for untreated control rats was 24 ± 3 days, 30 ± 2 days for irradiated controls, 37 ± 3 days for those receiving i.v. BPA, 52 ± 15 days for rats receiving i.c. BPA without BBB-D, and 95 ± 95 days for BBB-D followed by i.c. BPA and BNCT. The latter group had a 246% increase in life span (ILS) compared to untreated controls and a 124% ILS compared to that of i.v. injected animals. These survival data are the best ever obtained with the F98 glioma model and suggest that i.c. administration of BPA with or without BBB-D may be useful as a means to increase the efficacy of BNCT.     

Non-responsiveness to hepatitis B vaccination in haemodialysis patients: association with impaired TCR/CD3 antigen receptor expression regulating co-stimulatory processes in antigen presentation and recognition

The study was undertaken to evaluate the relationship betweennon-responsiveness to hepatitis B (HBV) vaccination in haemodialysedpatients and HBs antigen (Ag) presentation and recognition dependingon TCR/CD3 receptors expression. We have found that the causeof the blunted response to HBV vaccination is multifactorialand seems to be associated with the following: (1) A reducednumber of TCR/CD3 antigen receptor complexes on freshly isolateduraemic CD4 T cells, especially in non-responders. (2) The bluntedproliferative response of uraemic CD4 T cells isolated fromnon-responders and stimulated for 6 days by autologous monocytespresenting HBsAg was associated with the decreased density ofthe TCR/CD3 receptors. (3) Moreover, in uraemic non-respondersthe expression of adhesion and accessory molecules on monocytes(intercellular adhesion molecule-1/ ICAM-1, HLA-DR/Ia/) wassignificantly decreased following the culture with autologousmonocytes serving as HBsAg-presenting cells. CD4 molecules andlymphocyte function antigen-1ß /LFA-1ß/on helper-inducer T cells were increased before and after theculture. (4) These findings were also associated with a diminishedbinding capacity of IL-1ß and IL-6 to their receptorson helper-inducer T cells. (5) IL-2, IFN- and IL-4 productionwas decreased in uraemic non-responders, especially after 72h of the culture. (6) Inhibited proliferation of helper-inducerT cells in uraemic non-responders was only partially reversiblein the presence of exogenous IL-1ß, IL-6, IL-2 andIFN-. (7) HLA typing of uraemic non-responders was associatedwith extended haplotype: HLA A1, B8, DR3, DR7, DQ2.     

Congenital muscular dystrophy and severe central nervous system atrophy in two siblings

Severe degenerative features of the nervous system of a hitherto unknown kind, associated with a neuromuscular disorder with histopathological features of congenital muscular dystrophy, are reported in two female siblings. The clinical profile was characterized by generalized hypotonia followed by spastic tetraplegia, contractures, polyneuropathy, lack of cognitive development and progressive microcephaly. There was no involvement of the eyes. Neuropathological examination of the brain of one sibling, who died at the age of 30 months, revealed subtotal loss of neurons in the cerebral and cerebellar cortex and in the ventral pons, and secondary loss of myelin in the cerebral and cerebellar subcortical white matter. Sural nerve biopsy in the other sibling, who had a similar neurological affection, showed a lack of large myelinated fibers.This investigation is part of the research program Disorders of the Neuromuscular System of the University of Nijmegen