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J Albrecht

Publications and source records attributed to J Albrecht.

At least 91 records · Page 5Linked to original sources
PubMed1994

Similarities of the in vivo and in vitro effects of mercuric chloride on [3H]ouabain binding and potassium activation of Na+/K(+)-ATPase in isolated rat cerebral microvessels.

A previous study revealed that a single i.p. administration of 6 mg/kg body wt. of mercuric chloride (MC) durably inhibits the rat cerebral microvascular Na+/K(+)-ATPase activity [1]. In this study, cerebral microvessels isolated 18 h after MC treatment were compared to those obtained from control rats and subsequently treated or not treated with MC in vitro, with regard to: (a) [3H]ouabain binding to, and (b) K(+)-activation kinetics of, the Na+/K(+)-ATPase. Microvessels from MC-treated rats showed a decrease of [3H]ouabain binding down to 62% of the control binding, and the same degree of inhibition was attained in microvessels treated in vitro with 5 microM MC. Analysis of the K(+)-activation kinetics of Na+/K(+)-ATPase revealed a decrease of Vmax from the control value of 13.1 to 7.67 mumol/mg/h in microvessels from MC-treated rats and 6.07 mumol/mg/h in microvessels treated in vitro with 5 microM MC, with no change in Km in either case. The similarity of the effects of in vivo and in vitro treatments suggests that the inhibition of the cerebromicrovascular Na+/K(+)-ATPase following in vivo administration of MC results from a direct interaction of Hg2+ with the enzyme.

Animals↗
PubMed1994

K(+)-, hypoosmolarity-, and NH4(+)-induced taurine release from cultured rabbit Müller cells: role of Na+ and Cl- ions and relation to cell volume changes.

The release of preloaded radiolabeled taurine (TAU) from cultured rabbit Müller cells [14-21 days in vitro (DIV)] was measured before and after treatment with the following stimuli: 1) isoosmotic 65 mM KCl; 2) a medium made hypoosmotic by uncompensated lowering of Na+ by 40-100 mM; and 3) NH4Cl ranging from 0.25 to 5 mM. The same stimuli were tested for their effect on the cell volume by the 3-O-methyl-D-glucose (OMG) uptake method of Kletzien et al. (Anal Biochem 68:537, 1975). Hypoosmotic media and 65 mM KCl stimulated TAU release, and the release was well correlated with the increase of cell volume. The stimulatory effect of 65 mM KCl was abolished by isotonic removal of Cl- or Na+, and omission of either ion markedly enhanced the basal release of TAU. The results are roughly consistent with the characteristics of the swelling-induced TAU release reported for cultured astrocytes and neurons of various CNS regions, and also for freshly isolated, nondissociated retina. Taken together, the results are indicative of a significant role of TAU release from Müller cells, in the osmosensory response of the retina. Ammonium chloride stimulated TAU release in a dose-dependent manner, a significant stimulation being already observed at 0.5 mM, a concentration that is frequently measured in brain during acute hyperammonemia. The effect of NH4Cl was strictly chloride dependent at 0.5-2 mM, but partly Cl- independent at 5 mM. The Kletzien's method did not appear to be well suited for measuring cell volume in the presence of ammonium ions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Demonstration of URR-duplication variants of human papillomavirus type 6 in paraffin-embedded tissue sections of one condyloma acuminatum and one Buschke-Loewenstein tumour.

Human papillomavirus type 6 (HPV 6) induces condylomata acuminata and laryngeal papillomas. Occasionally, HPV 6 may also be found in low-grade verrucous carcinomas. In some tumours, genetic analysis revealed the presence of HPV 6 variants with rearrangements, mostly DNA duplications, within the upstream regulatory region (URR). In this study, we analysed 98 formalin-fixed, paraffin-embedded condylomata acuminata obtained from 54 patients for the presence of URR-duplication variants of HPV 6. HPV 6 DNA could be amplified by polymerase chain reaction (PCR) from 40 samples. One condyloma acuminatum contained a HPV 6 genome with rearranged URR. Analysis using restriction enzyme cleavage suggested a DNA duplication within the URR of approximately 200 bp, spanning the Hpa II site at nt 7863 and the Dde I site at nt 7843 but not involving the Rsa I site at nt 7633. In addition, we analysed the distribution of the already characterized URR-duplication variant HPV 6AC1B within different paraffin-embedded tissue sections of a Buschke-Loewenstein tumour. No correlation could be demonstrated between the presence of the rearranged genome and malignant histological changes. This result and the demonstration of an URR-duplication variant in a typical condyloma acuminatum suggest that duplications within the URR of HPV 6 are not directly related to malignant progression of HPV 6-induced tumours.

Base Sequence↗
PubMed1994

Ammonia added in vitro, but not moderate hyperammonemia in vivo, stimulates glutamate uptake and H(+)-ATPase activity in synaptic vesicles of the rat brain.

The uptake of radiolabelled neurotransmitters: glutamate (GLU), GABA, and dopamine (DA) and the activity of the vacuolar type H(+)-pumping ATPase (H(+)-ATPase), were measured in crude synaptic vesicles treated in vitro with a neurotoxic (3 mM) dose of NH4+ (acetate or chloride), or isolated from rats with a moderate increase of brain ammonia (to approximately 0.6 mM) induced by i.p. administration of ammonium acetate (HA rats) or a hepatotoxin-thioacetamide (HE rats). In vitro treatment with ammonium salts increased the sodium-independent, chloride-dependent uptake of GLU but did not stimulate the uptake of GABA or DA. The in vitro treatment also stimulated the H(+)-ATPase activity. Since H(+)-ATPase generates the electrochemical gradient driving synaptic vesicular neurotransmitter transport, its stimulation by ammonia may have facilitated GLU uptake. However the GLU specificity of the effect must be related to other factors differentially affecting GLU uptake and the uptake of other neurotransmitters. Enhanced GLU accumulation in the synaptic vesicles may contribute to the increase of synaptic GLU exocytosis previously reported to accompany acute increases of brain ammonia to toxic levels. However, GLU uptake and H(+)-ATPase activity, but also the uptake of GABA and DA, were unchanged in synaptic vesicles prepared from rats with HA or HE. This indicates that changes in GLU and/or GABA release reported for moderate hyperammonemic conditions must be elicited by factors unrelated to the synaptic vesicular transport of the amino acids.

Ammonia↗
PubMed1994

Long-term treatment with ammonia affects the content and release of taurine in cultured cerebellar astrocytes and granule neurons.

High (50 mM) K+ stimulated the release of preloaded [3H]taurine from cultured cerebellar astrocytes and granule neurons with a delayed onset and only when the stimulus was applied in isoosmotic, but not in hypertonic (50 mM sucrose) medium. The process thus exhibited characteristics typical for the osmosensory or osmoregulatory response noted in a variety of nerve cell cultures. Addition of 1 mM NH4Cl to the astrocytic culture for 24 h increased the unstimulated release of [3H]taurine. However, this increase was not suppressed in a hypertonic medium, thus differing from the response accompanying regulatory volume decrease in astrocytes exposed to hypoosmolar or high potassium media. In accordance with the enhanced unstimulated release of [3H]taurine, addition of 1 mM NH4Cl decreased by 15% the taurine content in these cells. However, the addition abolished the stimulatory effect of 50 mM K+ on [3H]taurine release, indicating a loss of the osmosensory response of the cells. By contrast, treatment of granule neurons with 1 mM NH4Cl for 24 h remained without effect on any of the components of [3H]taurine release. However, the treatment increased the taurine content in granule neurons by 43%. This increase resembles the response usually noted in astrocytes adapted to hyperosmotic medium and may at least in part, reflect adaptation of the neurons to the slight increase in medium osmolarity due to the addition of ammonium chloride. The results are consistent with the selective vulnerability of astrocytes to hyperammonemic conditions, adding credence to earlier morphological observations.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗
PubMed1994

Clinical predictors of response to recombinant interferon-alpha treatment in patients with chronic non-A, non-B hepatitis (hepatitis C). The Hepatitis Interventional Therapy Group.

Chronic non-A, non-B hepatitis (NANBH) is a common and often progressive liver disease. Based on current serological tests, hepatitis C virus (HCV) infection is responsible for most cases. Interferon-alpha (IFN) treatment at a dose of 3 x 10(6) units given three times per week for 24 weeks has been shown to be effective in normalizing serum alanine aminotransferase (ALT) levels and reducing hepatic inflammation in approximately 40% of these patients. The purpose of this study was to identify pretreatment characteristics in patients with chronic hepatitis C(CH-C) which would best predict a favourable response to IFN treatment (normalization of serum ALT). One hundred and sixty-three adult patients who had participated in a large multicentre treatment trial were included in the study group; 84 had been treated with 3 x 10(6) units of recombinant IFN-alpha-2b (rIFN) subcutaneously three times per week for 24 weeks and 79 patients had been treated with 1 x 10(6) units rIFN in the same dosage schedule. Forty-one pretreatment historical, clinical, laboratory and histological variables were evaluated. In addition, early biochemical improvement during treatment was evaluated as a predictor of ultimate response. Univariate analysis identified six variables (dose, dose m-2, weight, body surface area, ongoing ethanol use, white blood cell count and the presence of symptoms) as potential predictors of response (two-tailed, P < 0.15). By multivariate analysis, however, only the 3 x 10(6) dose of rIFN was independently predictive of response (P < 0.01). When the analysis of response was confined to those patients who received treatment with 3 x 10(6) units of rIFN, seven variables [body weight, surface area, dose m-2, current ethanol use, serum albumin and the presence of chronic persistent hepatitis (CPH) on entry liver biopsy] were more frequent in patients who responded to therapy. In a multivariate model, only CPH and body weight predicted an increased likelihood of response (P < 0.01). However, the model was not a sensitive predictor of response as only 18% of the study group had CPH on liver biopsy. A decrease in serum ALT levels within the first 12-16 weeks of rIFN treatment was found to be the strongest indicator of an ultimate response to treatment. Thus, assessment of early response to IFN treatment is the only practical means of predicting complete response and avoiding prolonged and unnecessary therapy in those with little chance of response.

Adult↗
PubMed1994

Differential regulation of the JE gene encoding the monocyte chemoattractant protein (MCP-1) in cervical carcinoma cells and derived hybrids.

Malignant human papillomavirus type 18 (HPV18)-positive cervical carcinoma cells can be reverted to a nonmalignant phenotype by generation of somatic cell hybrids with normal human fibroblasts. Although nontumorigenic hybrids, their tumorigenic segregants, and the parental HeLa cells have similar in vitro properties, inoculation only of nontumorigenic cells into nude mice results in a selective suppression of HPV18 transcription which precedes cessation of cellular growth. Our present study, aimed at understanding the differential regulation in vitro and in vivo, shows that the JE gene, encoding the monocyte chemoattractant protein (MCP-1), is expressed only in nontumorigenic hybrids. Although the gene, including its regulatory region, is intact, no JE (MCP-1) mRNA is detected in the tumorigenic segregants and in other malignant HPV-positive cervical carcinoma cell lines. Tests of several monocyte-derived cytokines showed that only tumor necrosis factor alpha strongly induces the JE (MCP-1) gene in nontumorigenic cells and that this is accompanied by a dose-dependent reduction of HPV transcription. The JE (MCP-1) up-regulation occurs within 2 h and does not require de novo protein synthesis. The response to tumor necrosis factor alpha seems to be mediated by an NF-kappa B-related mechanism, since the induction can be completely abrogated by pretreating the cells with an antioxidant such as pyrrolidine dithiocarbamate. Interestingly, cocultivation of nonmalignant hybrids with monocyte-enriched fractions from human peripheral blood also results in an induction of the JE (MCP-1) gene and a concomitant suppression of HPV18 transcription. Neither effect is observed in malignant cells. These data suggest that JE (MCP-1) may play a pivotal role in the intercellular communication by triggering an intracellular pathway which negatively interferes with viral transcription in HPV-positive nontumorigenic cells.

Base Sequence↗
PubMed1994

Changes of activity and ultrastructural localization of alkaline phosphatase in cerebral cortical microvessels of rat after single intraperitoneal administration of mercuric chloride.

Inorganic mercury salts administered systemically at low mg/ml doses produce neurotoxic effects without penetrating the cerebral microvascular endothelial cells which form the blood-brain barrier (BBB). This phenomenon promoted investigations testing a hypothesis relating inorganic mercury-induced brain dysfunction to its interference with the BBB transport. In the present study, we tested the effect of a single i.p. administration of mercuric chloride (MC) (6 mg/kg body weight) on the activity and ultrastructural localization of cerebral alkaline phosphatase (AP), a cerebromicrovascular marker enzyme primarily located on luminal plasmalemma of endothelial cells. At 1h after MC administration, light microscopy revealed a virtual absence of AP in cerebral cortical layers II and III, and its dramatic reduction in the remaining layers. Electron microscopy confirmed the disappearance of the AP reaction product from luminal endothelial cell membranes, and luminal phasmalemma revealed pinocytic vesicles and invaginations likely to manifest changes in BBB transport. At 18h post-treatment, a moderate enzyme activity appeared on abluminal endothelial plasmalemma and on basement membrane, but remained absent from luminal plasmalemma. A similar picture persisted through day 5 post-treatment. The inhibition and subsequent translocation of AP activity from luminal to abluminal site and the accompanying ultrastructural changes are typical of the formation of "leaky" microvessels, previously reported for a variety of neuropathological conditions associated with BBB damage.

Alkaline Phosphatase↗
PubMed1994

Coping and communication among parents and children with human immunodeficiency virus and cancer.

Coping strategies and communication of three groups of 20 preschool children and their parents were compared. One group was composed of children infected with the human immunodeficiency virus (HIV) who displayed clinical symptoms of the disease; the second group was composed of children diagnosed with cancer; and the third group was composed of healthy children. Results indicated that the parents of children with life-threatening illnesses reported greater degrees of wishful thinking than did control subjects. Furthermore, parents of children with HIV reported more wishful thinking than did parents of children with cancer. Finally, significantly more children with cancer were aware of their diagnosis than were children with HIV. The findings in this study suggest coping and communication difficulties for parents and children with HIV.

Adaptation, Psychological↗
PubMed1994

Laboratory diagnosis of radicular and pseudoradicular syndromes in cerebrospinal fluid (CSF): reliability of methods in consideration of pathogenetic aspects. Report on section "CSF diagnosis" of 4th Klagenfurter Neurology Workshop Conference on radicular and pseudoradicular syndromes, Klagenfurt, Austria, August 28-29, 1992.

Laboratory tests may be used to confirm the clinical differentiation of pseudoradicular syndromes and radicular syndromes. In the presence of pseudoradicular syndromes, CSF and blood samples yield no positive results with either non-specific or specific methods. Radicular syndromes give rise to positive findings; using non-specific methods they can be subdivided into inflammatory and non-inflammatory forms, with and without blood-nerve barrier impairment. Non-specific quantities of CSF routine diagnosis are total protein, albumin, leukocyte counts and differential cell count, L-lactate, intrathecal -IgG, -IgA, -IgM and immunoglobulin-class oligoclonal bands. Oligoclonal bands enable the highly sensitive differentiation of non-inflammatory from subacute-chronically inflammatory forms of radicular syndromes. Most of the specific quantities are the subject of current research, e.g. bacterial antigens, D-lactate, cultivation tests, polymerase chain reaction tests and pathogen-specific oligoclonal bands. Pathomechanisms affecting the permeability of the blood-nerve barrier to increasing concentrations of protein and to leukocyte subsets possibly explain the CSF findings in radicular and pseudoradicular syndromes.

Diagnosis, Differential↗
PubMed1994

Quantitative detection of hepatitis C virus RNA with a solid-phase signal amplification method: definition of optimal conditions for specimen collection and clinical application in interferon-treated patients.

To determine the optimal conditions for preparation of serum specimens for quantitative hepatitis C virus RNA determination, patient samples were processed such that differences in time from clot formation to centrifugation, centrifugation to separation of serum and collection of serum until freezing could be independently assessed. The effects of multiple cycles of freezing and thawing were also determined. There was progressive and significant loss of hepatitis C virus RNA activity when the time from the formation of the clot until centrifugation was longer than 2 hr. This reduction reached 32% after 6 hr and 49% after 24 hr. If centrifugation was performed immediately after formation of the clot, loss of hepatitis C virus RNA activity was reduced to less than 10% even though the serum remained unseparated from the clot for up to 6 hr. Centrifugation of blood through a paraffin plug (serum separator tube) prevented loss of hepatitis C virus RNA activity for up to 24 hr. There was no loss of hepatitis C virus RNA activity with up to three freeze-thaw cycles. When patient specimens were prepared under these optimal conditions, the sensitivity of the quantitative branched DNA signal amplification assay in patients with hepatitis C virus infection was 83% and the specificity in patients with liver disease was 100%. Fluctuations in hepatitis C virus RNA levels were shown to correlate with biochemical changes observed in patients treated with recombinant interferon-alpha 2b. These data demonstrate that improper or inconsistent methods of serum preparation may result in falsely low and unreliable levels of hepatitis C virus RNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine Transaminase↗
PubMed1993

Loss of GABAB binding sites in the cerebral cortex of rats with acute hepatic encephalopathy.

The binding of [3H]GABA to GABAA and GABAB binding sites was measured in cerebral cortical membranes derived from control rats and rats with acute hepatic encephalopathy (HE) induced with a hepatotoxin, thioacetamide. HE did not affect the kinetic parameters (KD and Bmax) for the GABAA binding site. However, HE decreased Bmax (but not KD) for the GABAB binding site to 32% of the control level, indicating a substantial loss of GABAB receptors. Since GABAB receptors control the cerebral cortical release of the amino acid neurotransmitters glutamate and GABA, the loss of GABAB receptors is likely to contribute to the array of disturbances of glutamatergic and GABAergic neurotransmission known to accompany HE.

Acute Disease↗
PubMed1993

Stimulation of D-aspartate efflux by mercuric chloride from rat primary astrocyte cultures.

Mercuric chloride (HgCl2; MC) was shown to increase D-aspartate release from preloaded astrocytes in a dose-dependent fashion. Two sulfhydryl (-SH) protecting agents, a cell membrane non-penetrating compound, reduced glutathione (GSH), and the membrane-permeable dithiothreitol (DTT), were found to inhibit the stimulatory action of MC on the efflux of radiolabeled D-aspartate. MC-induced D-aspartate release was completely inhibited by the addition of 1 mM DTT or GSH during the actual 5 min perfusion period with MC (5 microM). However, when added after MC treatment, this inhibition could not be sustained by GSH, while DTT fully inhibited the MC-induced release of D-aspartate. Neither DTT nor GSH alone had any effect on the rate of astrocytic D-aspartate release. Accordingly, it is postulated that the stimulatory effect exerted by MC on astrocytic D-aspartate release is associated with vulnerable -SH groups located within, but not on the surface of the cell membrane. Omission of Na+ from the perfusion solution did not accelerate MC-induced D-aspartate release, suggesting that reversal of the D-aspartate carrier can not be invoked to explain MC-induced D-aspartate release. Furthermore, MC did not appear to be associated with astrocytic swelling.

Animals↗
PubMed1993

Ultrastructural evidence that mercuric chloride lowers the threshold for glutamate neurotoxicity in an organotypic culture of rat cerebellum.

Separate exposure of organotypic cultures, derived from newborn rat cerebellum, to non-toxic concentration of either 100 microM glutamate (GLU) or 1 microM mercuric chloride (MC), for as long as 3 days, produced no distinct ultrastructural changes in neurons and glial cells. By contrast, simultaneous exposure to both agents resulted, as early as after 30 min, in microvacuolar degeneration of neurons and later on in postsynaptic abnormalities, typically accompanying excitotoxic lesions but not heavy metal-induced lesions. The results indicate that MC at low micromolar concentrations lowers the threshold for GLU neurotoxicity.

Animals↗
PubMed1993

Hyperammonemia and hepatic encephalopathy stimulate rat cerebral synaptic mitochondrial glutamate dehydrogenase activity specifically in the direction of glutamate oxidation.

The effects of hepatic encephalopathy (HE) due to thioacetamide (TAA)-induced liver failure and hyperammonemia (HA) produced by repeated i.p. administration of ammonium acetate on the activity of glutamate dehydrogenase (GlDH) in the direction of glutamate (Glu) synthesis from--(GlDH-NADH) or its oxidation to alpha-ketoglutarate (alpha-KG) (GlDH-NAD), respectively, were examined in non-synaptic and synaptic mitochondria from rat cerebral hemispheres. In non-synaptic mitochondria, HE and HA stimulated the GlDH-NADH activity by, respectively, 33% and 49%, but neither condition affected the GlDH-NAD activity. In synaptic mitochondria, HE and HA decreased the GlDH-NADH activity by, respectively, 31% and 28%, but stimulated the GlDH-NAD activity by as much as 90% (HE) and 100% (HA). Kinetic assays revealed that HA increased the Vmax of the synaptic mitochondrial GLDH-NAD by 105%, without affecting the Km for Glu. The stimulation of GlDH-NAD favors the oxidation of synaptic Glu to alpha-KG, and may represent an adaptive response serving to counteract hyperammonemia-induced decrease of cerebral alpha-KG production in other metabolic pathways.

Ammonia↗
PubMed1993

The role of sulfhydryl groups and calcium in the mercuric chloride-induced inhibition of glutamate uptake in rat primary astrocyte cultures.

Inhibition by mercuric chloride (MC) of the astrocytic uptake of the excitotoxic neurotransmitter L-glutamate (L-GLU) has been postulated to contribute to MC neurotoxicity. In the present study, we analyzed the ability of two sulfhydryl (SH)-protecting agents: a cell membrane non-penetrating compound-reduced glutathione (GSH), and the membrane permeable dithiothreitol (DTT), to reverse the inhibitory action of MC on the initial rate of uptake of radiolabelled GLU (100 microM) in primary cultures of rat astrocytes. MC at 5 microM concentration reduced the uptake to 46% of control when present in the incubation medium during the 5 min of actual uptake, and to 27% of control when astrocytes were preincubated for 30 min in HEPES buffer containing MC prior to GLU uptake measurements. GLU uptake inhibition caused by 30 min preincubation with MC was partly relieved by the addition of 1 mM DTT during the actual 5 min uptake period. However, this inhibition could not be reversed by 1 mM GSH. Accordingly, it is postulated that the inhibitory effect exerted by MC on GLU uptake is associated with vulnerable SH groups located within, but not on the surface of the cell membrane. Neither 5 microM N-ethylmaleimide (NEM) nor 5 microM or 25 microM iodoacetate (IA) affected GLU uptake, indicating steric hindrance of the access of these two sulfhydryl reagents to the SH groups critical for the uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗