A60 SIGNIFICANCE OF IBD DIAGNOSIS IN THE BC COLON SCREENING PROGRAM

Background

There has been evidence of incidental inflammatory bowel disease (IBD) diagnosis in otherwise asymptomatic patients during colonoscopy to follow-up a positive fecal immunochemical test (FIT). Little is known about the significance of subclinical disease and its progression in this population.

Aims

To determine the incidence and outcome of subclinical IBD in a colon screening program. We hypothesize that the proportion of patients receiving biologic or surgical intervention would be low.

Methods

IBD cases were identified using the BC Colon Screening Program (BCCSP) database; pilot program at 3 sites from 01/2009–11/2013, and province-wide from 11/2013- 12/2017. Inclusion criteria: diagnosis of IBD at BCCSP colonoscopy performed for positive FIT. Exclusion criteria: prior IBD diagnosis, microscopic colitis. Data obtained through chart review included: demographics, endoscopy and histology reports, and medical/surgical treatment.

Results

Of 93,994 colonoscopies, 608 were diagnosed with IBD (0.65%) (Figure 1). Chart review of 245 cases at 10 institutions was performed. 65 patients were excluded. Of the 180 cases included, the average age at diagnosis was 59.6 years and 58.9% were male. 70.6% of patients were Caucasian, 12.2% were East Asian, and 7.8% South-east Asian. 49.4% were diagnosed with Crohn’s disease (CD), 33.9% with Ulcerative Colitis (UC), and 16.7% with indeterminate colitis, with a median follow-up of 25.5 months (0–85.9 months). 62.8% of patients received treatment, with 17.8% requiring biologic therapy, and 1.7% requiring surgical intervention.

Conclusions

This is the largest study assessing subclinical IBD in a colon screening program, with IBD incidence comparable to other publications in this population. However, the high proportion of patients diagnosed with CD is a novel finding. Also, subclinical IBD is not as benign as previously reported as nearly 20% of patients required biologics and/or surgical intervention.

Funding Agencies

None

Good servant, bad master: sulfide influence on partial nitritation of sewage

When applying partial nitritation (PN) to anaerobically pre-treated sewage, ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) will be exposed to dissolved sulfide and methane. Both sulfide and methane may inhibit nitrification. To gain knowledge necessary for sustaining PN under these conditions, we exposed an AOB enrichment and a mixed nitrifying culture to dissolved sulfide and methane. In the mixed nitrifying culture, sulfide selectively inhibited NOB activity (K_I,AOB1 = 150 mg-S L^-1, K_I,NOB = 10 mg-S L^-1) which shows that sulfide may help establish PN. The AOB enrichment showed similar K_I,AOB2 (130 mg-S L^-1), but nitritation activity lagged longer than the time necessary to remove sulfide from the liquid. This demonstrates that feeding of sulfide into established PN should be avoided. Methane inhibition of AOB enrichment was assessed in batch assays with 10 mg-CH₄ L^-1. As compared to control without methane, AOB enrichment activity was identical. Up to 51% of methane was converted to methanol, thus reducing the greenhouse gas emissions.

Sagopilone (ZK-EPO, ZK 219477) for recurrent glioblastoma. A phase II multicenter trial by the European Organisation for Research and Treatment of Cancer (EORTC) Brain Tumor Group

Background: Sagopilone (ZK 219477), a lipophylic and synthetic analog of epothilone B, that crosses the blood–brain barrier has demonstrated preclinical activity in glioma models.

Patients and methods: Patients with first recurrence/progression of glioblastoma were eligible for this early phase II and pharmacokinetic study exploring single-agent sagopilone (16 mg/m² over 3 h every 21 days). Primary end point was a composite of either tumor response or being alive and progression free at 6 months. Overall survival, toxicity and safety and pharmacokinetics were secondary end points.

Results: Thirty-eight (evaluable 37) patients were included. Treatment was well tolerated, and neuropathy occurred in 46% patients [mild (grade 1) : 32%]. No objective responses were seen. The progression-free survival (PFS) rate at 6 months was 6.7% [95% confidence interval (CI) 1.3–18.7], the median PFS was just over 6 weeks, and the median overall survival was 7.6 months (95% CI 5.3–12.3), with a 1-year survival rate of 31.6% (95% CI 17.7–46.4). Maximum plasma concentrations were reached at the end of the 3-h infusion, with rapid declines within 30 min after termination.

Conclusions: No evidence of relevant clinical antitumor activity against recurrent glioblastoma could be detected. Sagopilone was well tolerated, and moderate-to-severe peripheral neuropathy was observed in despite prolonged administration.

Deep endometriosis, including intestinal involvement--the interdisciplinary approach

Deep endometriosis is a disease which may involve all organs of the pelvis. The lesion is most often located at the backside of the uterus, involving the uterosacral ligaments and/or the rectovaginal septum. The involvement of adjacent organs, e.g. bowel, ureter, and bladder, makes an interdisciplinary approach necessary. There is a correlation between the radicalness of endometriosis resection and the postoperative improvement of complaints. In a series of 202 patients with deep endometriosis including the bowel we performed a segmental resection with anterior anastomosis including radical excision of all endometriotic lesions. The follow-up of 142 patients shows a significant improvement of pelvic pain (96%), dyschezia (88%), and dyspareunia (87%). Of 95 patients with a desire for children, 50% became pregnant. The postoperative complication rate was low. A leakage of anastomosis was seen in six cases (3%).

Die laparoskopische Therapie der Darmendometriose und der Stellenwert der medikamentösen Therapie

Patients with severe endometriosis involving the rectovaginal septum and bowel makes surgery necessary. The laparoscopic approach offers the possibility to perform the complete resection with minimal invasive techniques. Small lesions can be removed by full-thickness-resection. Large nodules make a segmental resection necessary. Deep lesions are resected with stapling devices. Nodules in the sigmoid ore removed by laparoscopic assisted hand-sewn anastomosis.

RESULTS

Between 3/96 and 7/03 142 patients with severe endometriosis involving the bowel have been treated laparoscopically. The pre-operative complains have been reduced as following: dyschezio: 88%, dyspareunia 87%, chronic pelvic pain 96%, disturbance of sexuality 75%. The complication rate was minimal: leakage of the anastomosis n=4 (2.8%), paraproctial abscess 2 (1.4%), blood transfusion 1 (0,7 %), severe stenosis of the anastomosis 6 (4.2%).

CONCLUSION

Laparoscopic approach is a safe and effective technique to treat deep infiltrating endometriosis with bowel involvement. The hormonal treatment of bowel endometriosis is used in patients with minimal symptoms. The postoperative treatment becomes necessary in incomplete operations or in patients with severe adenomyosis and infertility.

Anti-inflammatory antioxidants attenuate the expression of inducible nitric oxide synthase mediated by advanced glycation endproducts in murine microglia

Advanced glycation endproducts (AGEs) accumulate on long-lived protein deposits including beta-amyloid plaques in Alzheimer's disease (AD). AGE-modified amyloid deposits contain oxidized and nitrated proteins as markers of a chronic neuroinflammatory condition and are surrounded by activated microglial and astroglial cells. We show in this study that AGEs increase nitric oxide production by induction of the inducible nitric oxide synthase (iNOS) on the mRNA and protein level in the murine microglial cell line N-11. Membrane permeable antioxidants including oestrogen derivatives (e.g. 17beta-oestradiol) thiol antioxidants (e.g. (R+)-alpha-lipoic acid) and Gingko biloba extract EGb 761, but not phosphodiesterase inhibitors such as propentophylline, prevent the up-regulation of AGE-induced iNOS expression and NO production. These results indicate that oxygen free radicals serve as second messengers in AGE-induced pro-inflammatory signal transduction pathways. As this pharmacological mechanism is not only relevant for Alzheimer's disease, but also for many chronic inflammatory conditions, such membrane-permeable antioxidants could be regarded not only as antioxidant, but also as potent therapeutic anti-inflammatory drugs.

Neuronal and glial coexpression of argininosuccinate synthetase and inducible nitric oxide synthase in Alzheimer disease

The enzyme argininosuccinate synthetase (ASS) is the rate limiting enzyme in the metabolic pathway leading from L-citrulline to L-arginine, the physiological substrate of all isoforms of nitric oxide synthases (NOS). ASS and inducible NOS (iNOS) expression in neurons and glia was investigated by immunohistochemistry in brains of Alzheimer disease (AD) patients and nondemented, age-matched controls. In 3 areas examined (hippocampus, frontal, and entorhinal cortex), a marked increase in neuronal ASS and iNOS expression was observed in AD brains. GFAP-positive astrocytes expressing ASS were not increased in AD brains versus controls, whereas the number of iNOS expressing GFAP-positive astrocytes was significantly higher in AD brains. Density measurements revealed that ASS expression levels were significantly higher in glial cells of AD brains. Colocalization of ASS and iNOS immunoreactivity was detectable in neurons and glia. Occasionally, both ASS-and iNOS expression was detectable in CD 68-positive activated microglia cells in close proximity to senile plaques. These results suggest that neurons and astrocytes express ASS in human brain constitutively, whereas neuronal and glial ASS expression increases parallel to iNOS expression in AD. Because an adequate supply of L-arginine is indispensable for prolonged NO generation, coinduction of ASS enables cells to sustain NO generation during AD by replenishing necessary supply of L-arginine.

Arginine metabolism and the synthesis of nitric oxide in the nervous system

The biochemistry and physiology of L-arginine have to be reconsidered in the light of the recent discovery that the amino acid is the only substrate of all isoforms of nitric oxide synthase (NOS). Generation of nitric oxide, NO, a versatile molecule in signaling processes and unspecific immune defense, is intertwined with synthesis, catabolism and transport of arginine which thus ultimately participates in the regulation of a fine-tuned balance between normal and pathophysiological consequences of NO production. The complex composition of the brain at the cellular level is reflected in a complex differential distribution of the enzymes of arginine metabolism. Argininosuccinate synthetase (ASS) and argininosuccinate lyase which together can recycle the NOS coproduct L-citrulline to L-arginine are expressed constitutively in neurons, but hardly colocalize with each other or with NOS in the same neuron. Therefore, trafficking of citrulline and arginine between neurons necessitates transport capacities in these cells which are fulfilled by well-described carriers for cationic and neutral amino acids. The mechanism of intercellular exchange of argininosuccinate, a prerequisite also for its proposed function as a neuromodulator, remains to be elucidated. In cultured astrocytes transcription and protein expression of arginine transport system y(+) and of ASS are upregulated concomittantly with immunostimulant-mediated induction of NOS-2. In vivo ASS-immunoreactivity was found in microglial cells in a rat model of brain inflammation and in neurons and glial cells in the brains of Alzheimer patients. Any attempt to estimate the contributions of arginine transport and synthesis to substrate supply for NOS has to consider competition for arginine between NOS and arginase, the latter enzyme being expressed as mitochondrial isoform II in nervous tissue. Generation of NOS inhibitors agmatine and methylarginines is documented for the nervous system. Suboptimal supply of NOS with arginine leads to production of detrimental peroxynitrite which may result in neuronal cell death. Data have been gathered recently which point to a particular role of astrocytes in neural arginine metabolism. Arginine appears to be accumulated in astroglial cells and can be released after stimulation with a variety of signals. It is proposed that an intercellular citrulline-NO cycle is operating in brain with astrocytes storing arginine for the benefit of neighbouring cells in need of the amino acid for a proper synthesis of NO.

Acquisition of blood--tissue barrier--supporting features by hepatic stellate cells and astrocytes of myofibroblastic phenotype. Inverse dynamics of metallothionein and glial fibrillary acidic protein expression

A number of similarities between astrocytes and hepatic stellate cells (HSC) rose the question whether or not the protective barrier features of blood-tissue interface may be provided by HSC as well. To test this hypothesis, we investigated the presence of metallothionein (MT), a functional marker of blood--brain barrier, in HSC in situ and in cell culture and compared the results with those obtained with astrocytes. The dynamics of MT expression in cultured astrocytes and HSC was investigated by simultaneous labelling of the cells with a monoclonal antibody (MAb MT) against a lysine-containing epitope of the cadmium-induced monomer of MT-I from rat liver and antiserum against glial fibrillary acidic protein (GFAP). Cell activation was estimated by the presence of smooth muscle alpha-actin (SMAA). In immunoblotting, MAb MT recognized monomeric MT protein and proteins in the 30-kDa range; both bands were pronounced in brain and barely visible in liver homogenates. In situ, MAb MT reacted with very few perivascular cells situated in the parenchyma of the liver. Double immunolabelling of brain slices with MAb MT and antiserum against GFAP showed large areas of brain containing cells expressing both MT and GFAP. However, there were also regions in the brain where the cells produced solely GFAP or MT. In liver cell culture, MT was absent from HSC and hepatocytes in early periods of cultivation, during which the cells maintained their original features; however, MT was expressed strongly in HSC during their activation under prolonged culture conditions. Inversely, in astrocytes MT was expressed during early culturing and disappeared from the cells together with SMAA in late culture when GFAP was upregulated. These results suggest that the acquisition of myofibroblastic features by perivascular cells empowers them to establish a protective blood-tissue permeability barrier. In addition, this study shows that, at least in cell culture, an enrichment of perivascular cells in GFAP results in the disappearance of protective functions.

Metabolism of a 20-methyl substituted series of vitamin D analogs by cultured human cells: apparent reduction of 23-hydroxylation of the side chain by the 20-methyl group

We describe here for the first time the effect of introducing a 20-methyl group on the side-chain metabolism of the vitamin D molecule. Using a series of 20-methyl-derivatives of 1alpha,25-(OH)2D3 incubated with two different cultured human cell lines, HPK1A-ras and HepG2, previously shown to metabolize vitamin D compounds, we obtained a series of metabolic products that were identified by comparison to chemically synthesized standards on HPLC and GC-MS. 24-Hydroxylated-, 24-oxo-hydroxylated-, and 24-oxo-23-hydroxylated products of 20-methyl-1alpha,25-(OH)2D3 were observed, but the efficiency of 23-hydroxylation was low as compared with that of the natural hormone and, in contrast to 1alpha,25-(OH)2D3, no truncated 23-alcohol was formed from the 20-methyl analog. These data, taken together with results from other analogs with changes in the vicinity of the C17-C20 positions, lead us to speculate that such changes must alter the accessibility of the C-23 position to the cytochrome P450 involved. Using the HepG2 cell line, we found evidence that the 24S-hydroxylated product of 20-methyl-1alpha,25-(OH)2D3 predominates, implying that the liver cytochrome involved in metabolism is a different isoform. Studies with a more metabolically resistant analog of the series, 20-methyl-Delta(23)-1alpha,25-(OH)2D3, gave the expected block in 23- and 24-hydroxylation, and evidence of an alternative pathway, namely 26-hydroxylation. 20-Methyl-Delta(23)-1alpha,25-(OH)2D3 was also more potent in biological assays, and the metabolic studies reported here help us to suggest explanations for this increased potency. We conclude that the 20-methyl series of vitamin D analogs offers new perspectives into vitamin D analog action, as well as insights into the substrate preferences of the cytochrome(s) P450 involved in vitamin D catabolism.

Synthesis and biological activities of a new series of secosteroids: vitamin D phosphonate hybrids

By a structural combination of phosphonate and bisphosphonate moieties with the vitamin D skeleton a series of new vitamin D analogs was synthesized. Derivatives with 24beta-hydroxy- or 24-keto groups exerted considerable vitamin D activities in vitro while the hypercalcemic potentials were significantly reduced as compared to 1alpha,25-dihydroxyvitamin D(3) (calcitriol). Whereas the 24-hydroxy analogs did not influence bone formation in vivo in dosages below the hypercalcemic threshold, the 24-ketones were found to induce synthesis of new bone matrix in non-hypercalcemic doses. Vitamin D bisphosphonate hybrids, on the other hand, which did not elicit substantial vitamin D activities in vitro and tend to decrease serum calcium levels in vivo clearly induced osteoid formation in rats, indicating a mechanism of action different to calcitriol.

Effect of amifostine on neuroblastoma during high dose chemotherapy: in vivo and in vitro investigations

Amifostine (Ethyol, WR-2721) has been clinically used in combination with high dose therapy of neuroblastoma stage 4 with melphalan, carboplatin and VP-16 in 14 patients. The amifostine group was compared to a historical control group of 24 comparably-treated patients. There were no significant differences regarding the time of hematological recovery, the duration of hospitalization, the duration of antibiotic treatment and the extent of renal toxicity. However, in contrast to four patients of the control group, no patient in the amifostine group developed such severe mucositis that artificial ventilation became necessary. Pretreatment of neuroblastoma cell lines for 30 minutes with amifostine and the free thiol(WR-1065) did not reduce the cytotoxic effects of melphalan, carboplatin and VP-16. Evidence was obtained that the uptake of the activated thiol could be achieved by a polyamine transporter. Taken together, the data do not support the use of amifostine in high dose chemotherapy of neuroblastoma prior to autologous stem cell transplantation. However, amifostine may be more effective in conventional neuroblastoma therapy where protection of bone marrow stem cells is necessary.

Transport of L-citrulline in neural cell cultures

Uptake of L-[(14)C]citrulline was studied in cell culture models of the main neural cell populations, in astroglia-rich primary cultures derived from neonatal rat brain, in rat glioma cells C6-BU-1, in cells of the murine microglial clone N11 and in the glioma x neuroblastoma hybrid cell line 108CC15 with neuronal properties. For comparison, cells of the peripheral macrophage cell line RAW 264.7 were also investigated. A saturable component of uptake was found in all cases with K(M) values between 0.4 and 3.4 mM and V(max) values between 15 and 35 nmol.min(-1).(mg protein)(-1). A nonsaturable component dominated uptake at high concentrations of extracellular citrulline. Rates of uptake of L-citrulline were not affected when Na(+) or Cl(-) were omitted from the incubation medium or in the presence of depolarizing concentrations of K(+). Saturable uptake of citrulline was strongly inhibited by an excess of histidine or beta-2-aminobicyclo-(2.2.1)-heptane-2-carboxylic acid; excess amounts of arginine, creatine, glutamate, cysteic acid or N-methyl-alpha-aminoisobutyric acid did not reduce citrulline uptake. Preincubation of the cells with bacterial lipopolysaccharide and interferon gamma did not stimulate transport of citrulline. The results suggest that at physiological concentrations citrulline is taken up by neural cells with the help of transport system L for large neutral amino acids. Therefore, in the brain, effective utilization of extracellular citrulline as part of an intercellular trafficking of intermediates of an NO/citrulline cycle depends on the concentrations of all neutral amino acids present.

New vitamin D receptor agonists with decreased metabolic stability

The aim of the study was the development of vitamin D receptor agonists with decreased metabolic stability for the topical treatment of psoriasis and related hyperproliferative skin diseases. Calcitriol analogues 1, 2, 3, all of which contain modifications in the side chain, were synthesized. The obtained analogues were full agonists when the induction of CD14 expression in HL-60 cells, the induction of 5-lipoxygenase activity in Mono Mac 6 cells, and the inhibition of phytohemagglutinin (PHA)-stimulated lymphocyte proliferation were studied. The EC(50) value of the most active compound 1 was 1.2 nM in the CD14 assay and 1 nM in the 5-lipoxygenase assay, whereas calcitriol gave EC(50) values in these assays of 3.7 and 9 nM, respectively. In the lymphocyte proliferation assay, compound 1 and calcitriol had IC(50) values of 0.3 and 2.8 nM, respectively. All three compounds had receptor binding affinities similar to that of calcitriol. The compounds showed a decreased metabolic stability in rat liver homogenates and had a 50-fold lower affinity for the vitamin D-binding protein than calcitriol, which suggests that calcitriol analogues are metabolized more rapidly after systemic uptake or application. When injected into rats, the analogues displayed an approximately 100-fold lower hypercalcemic effect than calcitriol. In summary, our study presents three new and potent vitamin D receptor agonists with interesting profiles for development as antipsoriatic drugs.

The regeneration of reduced glutathione in rat forebrain mitochondria identifies metabolic pathways providing the NADPH required

Metabolic pathways underlying the regeneration of reduced glutathione were investigated in acutely isolated metabolically active mitochondria from rat forebrain. The application of hydrogen peroxide to the organelles was accompanied by a transient increase in glutathione disulfide. The recovery of reduced glutathione was significantly improved in the presence of alternatively succinate, malate, citrate, isocitrate, or beta-hydroxybutyrate. Inhibition of succinate dehydrogenase by malonate abolished the beneficial effect of succinate on the reduction of glutathione disulfide but did not influence the effect of isocitrate. Fluorocitrate, an inhibitor of aconitase, blocked the effect exerted by citrate but did not inhibit the effects of malate or beta-hydroxybutyrate. Uncoupling of the respiratory chain by carbonyl cyanide m-chlorophenylhydrazone prevented the beneficial effect of beta-hydroxybutyrate but did not abolish the improved reduction of mitochondrial glutathione disulfide in the presence of malate and isocitrate. These results suggest that NADP+-dependent isocitrate dehydrogenase as well as malic enzyme and nicotinamide nucleotide transhydrogenase contribute to the regeneration of NADPH required for the reduction of glutathione disulfide in brain mitochondria.

Common myofibroblastic features of newborn rat astrocytes and cirrhotic rat liver stellate cells in early cultures and in vivo

Double-immunolabelling techniques were employed to investigate the distribution of smooth muscle alpha-actin (actin) in glial fibrillary acidic protein (GFAP)-positive cells in rat brain during early postnatal development and maturation and in glial primary culture derived from newborn rat brain. In addition the expression of desmin was studied in the glial primary cultures as a function of the differentiation of the cells. Comparison of the cultured astroglial cells at an early age with hepatic stellate cells derived from CCl4-induced cirrhotic rat liver, revealed features of the astrocytic cytoskeleton characteristic of myofibroblastic cells, i.e., strong expression of both myofibroblastic markers, actin and desmin. In astroglial cells with an initial morphology reminiscent of fibroblasts the non-filamentous perinuclear immunoreaction of GFAP increased with time at the expense of actin and, partially, desmin. GFAP filaments were spread throughout the cytoplasm of the cells which acquired stellate morphology. The alterations in the morphology of the cells and the distribution and intensity of staining for GFAP and actin during the differentiation of astrocytes in culture were similar to those observed in astrocytes during the maturation of the brain. In astrocytes from a newborn brain as well as in cirrhotic hepatic stellate cells, the area of immunoreaction of GFAP was reduced and confined mainly to the nuclear region. In contrast, the cells expressed actin throughout the cytoplasm. These findings may hint at a similar function of these regionally specialized perivascular myofibroblastic cells in a normal brain and diseased liver and at inverse organ-specific functions which the cells fulfill under non-pathological conditions in vivo.

Induction of argininosuccinate synthetase in rat brain glial cells after striatal microinjection of immunostimulants

The enzyme argininosuccinate synthetase (ASS) initiates the metabolic pathway leading from L-citrulline to L-arginine, the only physiological substrate of all isoforms of nitric oxide synthases. The presence of ASS in glial cells in vivo was investigated by immunohistochemical methods in a model of rat brain inflammation. Phosphate-buffered saline or a mixture of bacterial lipopolysaccharide and interferon-gamma was injected into the left striatum, and animals were killed 24 hours later. Ipsilateral and contralateral sides of brain sections were incubated with an antiserum against ASS or antibodies against cell-specific markers. In the three areas examined, striatum, corpus callosum, and cortex, a strong induction of ASS immunoreactivity was observed in glial cells after injection of immunostimulants. A detailed quantitative analysis of double-stained sections revealed that ASS was almost exclusively expressed in reactive, ED1-positive microglial cells/brain macrophages in immunostimulant- or sham-injected ipsilateral sides of the sections. Furthermore, ASS/ED1 costaining was observed in perivascular cells. Colocalization of ASS with astroglial marker glial fibrillary acidic protein was given only occasionally after immunostimulation. ASS-positive neurons were detected in control and experimental animals; staining intensity was comparable in both cases. The results suggest that neurons express ASS constitutively, whereas the enzyme is induced in glial cells in response to proinflammatory stimuli. This finding is the first demonstration of an induction of a pathway auxiliary to generation of nitric oxide in brain in response to immunostimulants and provides new insight into neural arginine metabolism.

pH-dependent gating of ROMK (Kir1.1) channels involves conformational changes in both N and C termini

ROMK channels (Kir1.1) are members of the superfamily of inward rectifier potassium channels (Kir) and represent the channels underlying K+ secretion in the kidney. As their native counterparts, Kir1.1 channels are gated by intracellular pH, with acidification leading to channel closure. Although a lysine residue (Lys80) close to the first hydrophobic segment M1 has been identified as the pH sensor, little is known about how opening and closing of the channel is accomplished. Here we investigate the gating process of Kir1.1 channels exploiting their state-dependent modification by water-soluble oxidants and sulfhydryl reagents. Mutagenesis of all intracellular cysteines either alone or in combination revealed two residues targeted by these reagents, one in the N terminus (Cys49) and one in the C terminus (Cys308) of the channel protein. Both sites reacted with the thiol reagents only in the closed state and not in the open state. These results indicate that pH-dependent gating of Kir1.1 channels involves movement of protein domains in both N and C termini of the Kir1.1 protein.

Argininosuccinate synthetase: localization in astrocytes and role in the production of glial nitric oxide

An antiserum raised against the peptide representing the partial sequence 196-222 of mouse liver argininosuccinate synthetase (ASS) was used to detect and localize the enzyme in cells of neural primary cultures. No ASS immunoreactivity was detected by Western blotting in homogenates of mouse pure astroglial cultures and rat astroglia-rich cultures. However, when the cultures had been treated with bacterial lipopolysaccharide, interferon-gamma, or a combination of both, ASS immunoreactivity was disclosed. Immunocytochemical examination of rat astroglia-rich cultures revealed a colocalization of ASS with the astroglial marker glial fibrillary acidic protein (GFAP) in many cells. However, there were some GFAP-positive cells showing no specific staining for ASS, and vice versa. Colocalization of ASS with the inducible isoform of nitric oxide synthase in the same cell was shown only occasionally; nitric oxide synthase was predominantly expressed in microglial cells. In rat neuron-rich primary cultures astroglial cells as well as neurons expressed ASS. Cells of mouse pure astroglial cultures were able to synthesize arginine and, consequently, nitric oxide from citrulline, but not from ornithine. The findings demonstrate that ASS is expressed in astroglial cells under conditions that stimulate long-lasting production of nitric oxide; a functional role of this enzyme in the latter process is implicated.

Inability of rat alveolar macrophages to recycle L-citrulline to L-arginine despite induction of argininosuccinate synthetase mRNA and protein, and inhibition of nitric oxide synthesis by exogenous L-citrulline

In the present study it was tested whether rat alveolar macrophages (AMphi) convert L-citrulline to L-arginine to maintain nitric oxide (NO) synthesis under conditions of limited availability of L-arginine. Rat AMphi (0.5 x 10(6) cells/well, cultured for 20 h in the absence or presence of 1 microg/ml lipopolysaccharides, LPS), were incubated for 6 h in amino acid-free Krebs solution and nitrite accumulation was determined as a measure of NO synthesis. After culture in the absence of LPS, nitrite in the incubation media was at the detection limit, independent of the addition of L-arginine or L-citrulline. AMphi, cultured in the presence of LPS, produced about 4 nmol per 10(6) cells and 6 h nitrite, and L-arginine enhanced nitrite accumulation in a concentration-dependent manner, maximally about threefold (EC50: 55 microM). In LPS-treated AMphi L-citrulline (up to 10 mM) failed to enhance nitrite accumulation, but rather inhibited it by about 50% in the presence of 100 microM L-arginine, i.e. when NO synthesis was enhanced. L-Arginine in the culture medium was 3H-labelled and its metabolism analysed by HPLC. In medium of AMphi exposed to LPS [3H]-L-arginine was reduced by about 60% after a 20-h culture period and this was almost balanced by an almost equal increase in [3H]-L-citrulline and [3H]-L-ornithine, i.e. L-arginine was markedly consumed. When [14C]-L-citrulline was added to the culture medium of AMphi, no significant formation of [14C]-L-arginine could be detected. On the other hand, argininosuccinate synthetase mRNA (by RT-PCR) and protein (by Western blot) was marginally detectable in control AMphi, but clearly induced after exposure to LPS. Finally, L-citrulline was shown to inhibit L-arginine uptake in a concentration dependent manner, by about 50% at 10 mM. In conclusion, although the expression of argininosuccinate synthetase in rat AMphi can be induced by LPS, AMphi appear not to be able to recycle significant amounts of L-citrulline to L-arginine to maintain sustained NO synthesis. On the contrary, at high concentrations L-citrulline can reduce NO synthesis, and this effect appears to be caused by inhibitory effects on L-arginine uptake.

Mitochondrial malic enzyme: purification from bovine brain, generation of an antiserum, and immunocytochemical localization in neurons of rat brain

To elucidate the cellular location of mitochondrial malic enzyme in brain, immunocytochemical studies were performed. For this purpose, mitochondrial malic enzyme was purified to apparent homogeneity from bovine brain and used for the immunization of rabbits. Subjecting the antiserum to affinity purification on immobilized antigen as an absorbent yielded a purified immunoreactive antibody preparation, which was characterized by probing cytosolic and mitochondrial fractions of bovine and rat brain in western blotting. As neither cross-reactivity with cytosolic malic enzyme nor immunoreactivity against other proteins could be observed, the antibody preparation was found suitable for immunocytochemistry. By using sections of perfusion-fixed rat brain, considerable resolution was achieved at the light-microscopic level. Distinct and specific staining of neurons was observed; in contrast, no staining of astrocytes and possibly unspecific staining within the nuclei of oligodendrocytes were obtained. From these data, it is concluded that mitochondrial malic enzyme is located in neurons; however, in astrocytes, the enzyme appears to be either lacking or present at a much lower level. A protective role against oxidative stress in neurons is proposed for mitochondrial malic enzyme.

Malic enzyme isoforms in astrocytes: comparative study on activities in rat brain tissue and astroglia-rich primary cultures

Anion exchange chromatography on diethylaminoethyl cellulose was optimized to separate the cytosolic and mitochondrial isoforms of malic enzyme from rat brain. Extracts of adult rat brain and of astroglia-rich primary cultures derived from the brains of newborn rats were analyzed for their content of the two isozymes. In the case of brain tissue 45% of malic enzyme activity was due to the cytosolic isoform. In contrast, in extracts from astroglia-rich primary cultures more than 95% of the total activity was associated with the cytosolic isozyme. From these data it is concluded that the cytosolic rather than the mitochondrial isoform of malic enzyme has prominent functions in astroglial metabolism.

Metabolic pathways for glucose in astrocytes

Cultured astroglial cells are able to utilize the monosaccharides glucose, mannose, or fructose as well as the sugar alcohol sorbitol as energy fuel. Astroglial uptake of the aldoses is carrier-mediated, whereas a non-saturable transport mechanism is operating for fructose and sorbitol. The first metabolic step for all sugars, including fructose being generated by enzymatic oxidation of sorbitol, is phosphorylation by hexokinase. Besides glucose only mannose may serve as substrate for build-up of astroglial glycogen. Whereas glycogen synthase appears to be present in astrocytes as well as neurons, the exclusive localization of glycogen phosphorylase in astrocytes and ependymal cells of central nervous tissue correlates well with the occurrence of glycogen in these cells. The identification of lactic acid rather than glucose as degradation product of astroglial glycogen appears to render the presence of glucose-6-phosphatase in cultured astrocytes an enigma. The colocalization of pyruvate carboxylase, phosphenolpyruvate carboxykinase and fructose-1,6-bisphosphatase points to astrocytes as being the gluconeogenic cell type of the CNS.

Expression of the Na+-D-glucose cotransporter SGLT1 in neurons

In brains of the rabbit, pig, and human, expression of the high-affinity Na+-D-glucose cotransporter SGLT1 and of the protein RS1, which alters the activity of SGLT1, was demonstrated. In situ hybridization showed that SGLT1 and RS1 are transcribed in pyramidal cells of brain cortex and hippocampus and in Purkinje cells of cerebellum. In neurons of pig brain SGLT1 protein was demonstrated by western blotting with synaptosomal membranes and by immunohistochemistry, which showed SGLT1 in pyramidal and Purkinje cells. To test whether SGLT1 in neurons may be activated during increased D-glucose consumption, an epileptic seizure was induced in rat brain, and the uptake of specific nonmetabolized substrates of SGLT1 [[14C]methyl-alpha-D-glucopyranoside ([14C]AMG)] and of Na+-independent transporters [2-deoxy-D-[14C] glucose ([14C]2-DG)] was analyzed by autoradiography. During the seizure the uptake of AMG and 2-DG was increased in the focus. Within two hours after the seizure 2-DG uptake in the focus returned to normal. In contrast, the AMG uptake in the focus area was still increased 1 day later. The data show that the high-affinity Na+-D-glucose cotransporter SGLT1 is expressed in neurons and can be up-regulated.

ATP-induced oscillations of cytosolic Ca2+ activity in cultured astrocytes from rat brain are modulated by medium osmolarity indicating a control of [Ca2+]i oscillations by cell volume

Oscillations of cytosolic Ca2+ activity ([Ca2+]i) induced by stimulation with ATP in rat astrocytes in primary cultures were analysed. Astrocytes, prepared from the brains of newborn rats, loaded with the fluorescent Ca2+ indicator fura-2/AM, were continuously stimulated with ATP (10 microM). ATP caused a large initial [Ca2+]i peak, followed by regular [Ca2+]i oscillations (frequencies 1-5/min). Astrocytes were identified by glial fibrillary acidic protein staining of cells after [Ca2+]i recording. The oscillations were reversibly blocked by the P2 purinoceptor antagonist suramin (30 microM). Influx of extracellular Ca2+ and mobilization of Ca2+ from intracellular stores both contributed to the oscillations. The effects of hypertonic and hypotonic superfusion medium on ATP-induced [Ca2+]i oscillations were examined. Hypertonic medium (430 mOsm) reversibly suppressed the ATP-induced oscillations. Hypotonic medium (250 mOsm), in spite of having heterogeneous effects, most frequently induced a rise in [Ca2+]i or reversibly increased the frequency of the oscillations. Thus, a change in cell volume might be closely connected with [Ca2+]i oscillations in astrocytes indicating that [Ca2+]i oscillations in glial cells play an important role in regulatory volume regulation in the brain.

Presence of argininosuccinate synthetase in glial cells as revealed by peptide-specific antisera

The presence and the possibility of induction of argininosuccinate synthetase in a glial cell line were investigated. For this purpose, antisera were produced against peptides representing partial sequences 196-222 and 337-349, respectively, of the mouse liver enzyme. Both antisera were shown to be monospecific for argininosuccinate synthetase. In Western blot experiments, immunoreactivity was found in mouse liver and brain homogenates. Only weak immunoreactivity was detectable in homogenates of cultured glioma cells, C6-BU-1. However, when the glioma cells were treated with either bacterial lipopolysaccharide, interferon-gamma, or a combination of both, argininosuccinate synthetase immunoreactivity was increased. The findings demonstrate that this enzyme is present in glial cells and is induced under conditions which stimulate persistent production of nitric oxide. The antisera will be a valuable tool for further investigations on arginine synthesis in brain as well as peripheral cells.

Effect of astroglial cell swelling on pH of acidic intracellular compartments

A variety of pathological conditions lead to swelling of astrocytes, which in turn stimulates ion release by activation of ion channels at the plasma membrane. In the present study, acridine orange and fluorescein isothiocyanate coupled to dextran (FITC-dextran) have been used to examine the effect of cell swelling on pH in acidic compartments of cultured astroglial cells. Both NH4Cl (2 mM) and chloroquine (10 microM), known to alkalinize acidic cellular compartments, led to the expected increase in acridine orange fluorescence intensity. Similar, albeit smaller, effects were elicited by a reduction of extracellular osmolarity (-80 mOsm) and treatment of the cells with glutamate (l mM), manoeuvres which enhanced cell volume. Determination of changes in the FITC-dextran fluorescence ratio (485/440 nm) allowed quantification of the pH changes in lysosomal compartments. Treatment with NH4Cl, reduced extracellular osmolarity and glutamate increased lysosomal pH by 0.65 +/- 0.07, 0.85 +/- 0.14 and 0.25 +/- 0.07, respectively. Measurement of cytosolic pH using 2',7',-bis-(2-carboxyethyl)-5- (and -6) carboxyfluorescein (BCECF) demonstrated a pronounced acidification following cell swelling, observed with both reduced extracellular osmolarity (by 0.23 +/- 0.05 pH units) and 1 mM glutamate (by 0.26 +/- 0.02 pH units). In conclusion, pH within lysosomes and possibly other acidic cellular compartments of astrocytes is increased by cell swelling, which may have important consequences for astrocyte function.

Potent gene regulatory and antiproliferative activities of 20-methyl analogues of 1,25 dihydroxyvitamin D3

The biological active form of vitamin D3, 1,25-dihydroxyvitamin D3 (VD), regulates cellular growth and differentiation. This provides the hormone with an interesting therapeutic potential. However, hypercalcemia is a side effect, which is caused by VD's classical action, the regulation of calcium homeostasis. This made the need for VD analogues with selectively increased cell regulatory properties. Studies with 20-epi analogues pointed out the importance of the carbon-20 position and led to the development of 20-methyl derivatives of VD. In this report the biological properties of the compounds ZK161422 and ZK157202, which are 20-methyl- and 20-methyl-23-eneanalogues, respectively, have been analyzed in comparison with VD. Both compounds show about 2-fold lower affinity to the VD receptor (VDR) than VD. However, compared to VD, their antiproliferative effect is up to 30-fold higher on human peripheral blood mononuclear cells and even up to 300-fold higher on human breast cancer MCF-7 cells. Whereas the hypercalcemic effect for ZK157202 is also increased 10-fold, ZK161422 has the same calcium-mobilizing potency as VD. Moreover, ZK161422, but not ZK157202, showed preference for gene activation from a promoter carrying a VD response element with a palindromic arrangement of two hexameric receptor binding sites spaced by 9 nucleotides (IP9) rather than for activation from a response element formed by a direct repeat spaced by 3 nucleotides (DR3). This observation supports a model, in which promoter selectivity reflects the selectively increased antiproliferative effect of VD analogues.

Biogenesis of thermogenic mitochondria in brown adipose tissue of Djungarian hamsters during cold adaptation

After cold exposure, cytochrome c oxidase (COX) activity increased about 2.5-fold within 2 weeks in the brown adipose tissue (BAT) of Djungarian hamsters. The mRNAs for COX subunits I and III and the 12 S rRNA, encoded on mitochondrial DNA (mtDNA), as well as mRNAs for COX subunits IV, Va and mitochondrial transcription factor A, encoded in the nucleus, were unchanged when expressed per unit of total tissue RNA. However, since total tissue RNA doubled per BAT depot, while total DNA remained unchanged, the actual levels of these transcripts were increased within BAT cells. In contrast, the abundance of mRNA for uncoupling protein was increased 10-fold, indicating specific activation of this gene. In addition, the maximal rate of protein synthesis analysed in a faithful in organello system was increased 2.5-fold in mitochondria isolated from BAT after 7 days of cold exposure. We conclude from these data that the biogenesis of thermogenic mitochondria in BAT following cold adaptation is achieved by increasing the overall capacity for synthesis of mitochondrial proteins in both compartments, by increasing their mRNAs as well as the ribosomes needed for their translation. In addition, the translational rate for COX subunits as well as all other proteins encoded on mtDNA is increased. Thus the pool of subunits encoded on mtDNA required for assembly of respiratory chain complexes is provided. By comparison with other models of increased mitochondrial biogenesis, we propose that thyroid hormone (generated within BAT cells by 5'-deiodinase, and induced upon sympathetic stimulation), which is a well known regulator of the biogenesis of mitochondria in many tissues, is also the major effector of these adaptive changes in BAT.

Studies on fructose metabolism in cultured astroglial cells and control hepatocytes: lack of fructokinase activity and immunoreactivity in astrocytes

Astroglia-rich primary cultures derived from the brains of newborn rats can be grown in the presence of sorbitol or fructose. In the present study, evidence was obtained by enzymatic analysis and immunocytochemistry that fructose is further metabolized to fructose-6-phosphate and that fructokinase is lacking in the astrocytes. In contrast, fructose-1-phosphate as well as fructokinase immunoreactivity could be detected in cultured hepatocytes. Considerable amounts of astroglial glycogen were synthesized from fructose. Lactate release in fructose-fed cultures was still 30% that of glucose-fed cells and was abolished in the presence of 2-deoxyglucose. No glycogen was synthesized when sorbitol, which is converted intracellularly to fructose, replaced glucose in the incubation medium. However, lactate release from sorbitol-fed cultures was still significant and was not abolished by 2-deoxyglucose. The results are compatible with the idea of astroglial glycogen being a store of lactate rather than glucose. Furthermore, the results demonstrate that sorbitol is an adequate substrate for astroglial glycolysis but, in contrast to fructose, cannot be utilized for the buildup of glycogen stores.

Stimulation of arginine transport and nitric oxide production by lipopolysaccharide is mediated by different signaling pathways in astrocytes

Transport of L-arginine and generation of nitrite in microglia-free astroglial cultures derived from neonatal mouse brain were stimulated by bacterial lipopolysaccharide (LPS) in a time- and dose-dependent manner. LPS stimulated arginine transport between 1.3- and 2.5-fold; half-maximal stimulation was obtained with 0.3 micrograms/ml LPS. Acceleration of transport was detectable within 6 h of incubation with LPS. Cycloheximide or actinomycin D neutralized the effect of LPS. Stimulation of generation of nitrite was reduced when the cells were incubated simultaneously with LPS and either genistein or diethyldithiocarbamate, inhibitors of protein tyrosine kinase and nuclear transcription factor kappa, respectively. However, stimulation of arginine transport was not reduced in the presence of these compounds. Dexamethasone inhibited stimulation of nitric oxide (NO) production but not of arginine transport. Protein kinase C inhibitor staurosporine had no effect on either process. The results suggest that LPS-stimulated acceleration of arginine transport in astrocytes requires protein as well as RNA synthesis. Induction of synthesis of an astroglial cationic amino acid transport system appears to be mechanistically independent from stimulation of intracellular NO production.

Lactate transport in cultured glial cells

Uptake of L-lactate was investigated with a radioactive tracer method in cultured rat glioma cells and in astroglia-rich primary cultures derived from rat brain. In the glioma cells, a saturable component of uptake was identified with half-maximal uptake occurring at 1.0 +/- 0.4 mM lactate. In addition, a non-saturable component dominated the uptake at high concentrations of lactate. In astroglia-rich primary cultures, no saturable component of uptake could be detected in the concentration range studied (0.1-15 mM). In conclusion, lactate uptake at physiological concentrations is predominantly mediated in the glioma cells by a carrier-dependent process, whereas in astroglial cells, simple diffusion appears to be the dominant way of lactate transport.

Transport of L-arginine in cultured glial cells

Uptake of radiolabelled L-arginine was studied in four different kinds of glial cultures, in astroglia-rich primary cultures derived from neonatal rat and mouse brains, in pure murine astrocyte cultures, and in rat glioma cells C6-BU-1. A saturable component of uptake was found in all cases with KM values between 15 and 35 microM and Vmax values between 0.8 and 2.5 nmol.min-1.(mg protein)-1. In addition, in all cell types a non-saturable component dominated total uptake at high concentrations of extracellular arginine. Rates of uptake of arginine were not affected when Na+ or Cl- were absent from the incubation buffer. Carrier-mediated uptake of arginine was reduced by depolarizing concentrations of K+ and strongly inhibited by an excess of lysine or ornithine. Histidine, asparagine, glutamine, citrulline, creatine, NG-nitro-L-arginine, NG-monomethyl-L-arginine, or L-canavanine inhibited L-arginine transport to various degrees. Uptake of arginine was not reduced in the presence of serine or alanine cysteic acid, N-methyl-alpha-aminoisobutyric acid, or 2-aminobicyclo-(2.2.1)-heptane-2-carboxylic acid. Rates of uptake of arginine were increased when cells had been preloaded with lysine. Preincubation of primary cultures, but not glioma cells, with bacterial lipopolysaccharide stimulated transport of arginine by increasing the Vmax value of uptake. This stimulation was dependent on protein synthesis. The results suggest that, at physiological concentrations, arginine is taken up into the glial cells with the help of the transport system "y+" for basic amino acids. In glial primary cultures, uptake of arginine appears to be regulated by compounds which also exert influence on nitric oxide synthesis.

Utilization of mannose by astroglial cells

Uptake and metabolism of mannose were studied in astroglia-rich primary cultures derived from neonatal rat brains. A saturable component of mannose uptake was found with half-maximal uptake at 6.7 +/- 1.0 mM mannose. In addition, a non-saturable component dominated the uptake at high concentrations of mannose. Glucose, cytochalasin B, or phloretin in the incubation buffer inhibited the carrier-mediated uptake of mannose. Within the astroglial cells mannose is phosphorylated to mannose-6-phosphate. In cell homogenates, the KM value of mannose-phosphorylating activity was determined to be 24 +/- 7 microM. The Vmax value of this activity is only 40% that of glucose-phosphorylating activity. Mannose-6-phosphate was converted to fructose-6-phosphate by mannose-6-phosphate isomerase. The specific activity of this enzyme in homogenates of astroglial cultures was higher than that of hexokinase. Two products of mannose utilization in astroglial cells are glycogen and lactate. The amounts of each of these products increased with increasing concentrations of mannose. In contrast to the generation of lactate, that of glycogen from mannose was enhanced in the presence of insulin. In conclusion, we suggest that mannose is taken up into the cells of astroglia-rich primary cultures by the glial glucose transporter and is metabolized to fructose-6-phosphate within the astroglial cells.

Uptake of L-lactate by cultured rat brain neurons

The uptake of L-lactate was investigated in neuronal primary cultures derived from embryonic rat brain with a radioactive tracer method. After preincubation of the cells in glucose-free buffer for 30 min, uptake increased with time for at least 10 min. A saturable component of uptake was found with half-maximal uptake at 10 mM lactate. This saturable component was abolished in the presence of 10 mM alpha-cyano-4-hydroxcinnamic acid. In addition, a non-saturable component dominated the uptake at high concentrations of lactate. Uptake was accelerated with decreasing pH, and was inhibited considerably by pyruvate. It is concluded that neurons are endowed with a lactate transport system which resembles in its properties the monocarboxylate carrier of peripheral tissues.

Purification of cytosolic malic enzyme from bovine brain, generation of monoclonal antibodies, and immunocytochemical localization of the enzyme in glial cells of neural primary cultures

Cytosolic malic enzyme (EC 1.1.1.40) was purified from bovine brain 5,600-fold to a specific activity of 47 U/mg. The enzyme is a homotetramer with a subunit molecular mass of 60 kDa and an isoelectric point of 6.2. Mouse monoclonal antibodies raised against this enzyme were purified and shown to be monospecific, as indicated by immunoblotting. Immunocytochemical examination of rat astroglia-rich primary cultures at the light microscopic level revealed colocalization of cytosolic malic enzyme with the astroglial marker glial fibrillary acidic protein. Also, a colocalization with the oligodendroglial marker myelin basic protein was found. Neurons in rat neuron-rich primary cultures did not show positive staining. The data suggest that cytosolic malic enzyme is a glial enzyme and is lacking in neurons.

Replacement of glucose by sorbitol in growth medium causes selection of astroglial cells from heterogeneous primary cultures derived from newborn mouse brain

Primary cultures derived from the brains of newborn mice are quantitatively dominated by astroglial cells, but contain also oligodendroglial, phagocytic and ependymal cells. When confluent cultures are fed with glucose-free growth medium containing 25 mM sorbitol for 14 days, oligodendroglial, phagocytic and ependymal cells are eliminated from the culture, as judged by morphological and immunocytochemical criteria. The remaining cells stain positively for vimentin and glial fibrillary acidic protein and, therefore, can be considered as astroglial cells. Inoculation of freshly dissociated mouse brain cells in the absence of glucose in a sorbitol-containing medium is not possible; however, feeding of the cultures from day 2 on with sorbitol instead of glucose results in a pure astroglial culture at confluency. Therefore glucose-free growth medium supplemented with sorbitol can be considered a selective medium for astroglial cells in primary mouse glial cultures.

myo-inositol transport in mouse astroglia-rich primary cultures

Uptake of radiolabeled myo-inositol was studied in astroglia-rich primary cultures derived from neonatal mouse brains. The uptake was saturable in the presence of Na+ with a Km of 25 microM and a Vmax of 60 pmol.min-1.(mg protein)-1, suggesting a high-affinity transport system for myo-inositol in astroglial cells. In addition, a Na(+)-independent, nonsaturable component was found. Carrier-mediated uptake was not inhibited by cytochalasin B (50 microM), but was reduced by depolarizing concentrations of K+ and, to different extents, in the presence of phloretin, ouabain, or amiloride (1 mM each). scyllo-Inositol, glucose, and galactose also reduced myo-inositol uptake; inhibition by the two hexoses was not reversed in the presence of 0.4 mM sorbinil. On the other hand, uptake of 2-deoxyglucose was not inhibited by high concentrations of myo-inositol. Preincubation of the cells with glucose-free or inositol-free medium stimulated uptake of myo-inositol and preincubation with 25 mM glucose in the presence of 0.4 mM sorbinil had no effect on the rate of uptake. The results suggest that myo-inositol is taken up into the astroglial cells by a transport mechanism that is distinct from that of glucose and probably is an active one. Sorbitol pathway activity does not interfere with myo-inositol uptake.

Increased nonshivering thermogenesis, brown fat cytochrome-c oxidase activity, GDP binding, and uncoupling protein mRNA levels after short daily cold exposure of Phodopus sungorus

In their natural environment, burrowing rodents experience rather fluctuating ambient temperatures and are acutely cold exposed only for short periods outside their burrows. The effect of short daily cold exposure on basal metabolic rate, nonshivering thermogenesis, brown fat thermogenesis, and uncoupling protein mRNA was studied in the Djungarian hamster, Phodopus sungorus. They were kept at 23 degrees C and exposed to 5 degrees C daily either for one 4-h period or twice for 2 h (in 12-h intervals). At the same time control hamsters were kept continuously either at thermoneutrality (23 degrees C) or at 5 degrees C. Two 2-h cold exposures daily were sufficient to increase basal metabolic rate and nonshivering thermogenesis to the same level as continuous cold exposure, whereas one 4-h cold period per day did not result in a significant increase of both parameters. Brown fat thermogenesis (as measured by cytochrome-c oxidase activity and GDP binding to the mitochondrial uncoupling protein) increased to the same extent by both treatments with short daily cold exposure. However, this increase was less than in the chronically cold-exposed hamsters. A similar result was found for uncoupling protein mRNA: both short-term cold-exposed hamsters increased uncoupling protein mRNA levels to a similar extent, but less than after chronic cold treatment. It is concluded that short daily cold exposures are sufficient to cause adaptive increases of the capacity of metabolic heat production as well as brown fat thermogenic properties.

Sorbitol pathway activity and utilization of polyols in astroglia-rich primary cultures

Astroglia-rich rat primary cultures can be grown in a glucose-free medium containing 25 mM sorbitol. After 10 days under these conditions, the total number of cells and DNA content are reduced to 50-60% of those of control cultures, but remain constant thereafter. The specific activities of the sorbitol pathway enzymes, sorbitol dehydrogenase and aldose reductase, are increased 2.5-fold and unchanged, respectively, if the cells are grown in the presence of sorbitol instead of glucose. Treatment with the aldose reductase inhibitor sorbinil does not decrease the number of cells cultured in the glucose-free medium in the presence of sorbitol. Fructose is as good a substrate for the glial cells as sorbitol, whereas out of a number of other polyols tested only xylitol can support the primary cultures for more than 3 days. Neither neuron-rich rat brain primary cultures nor rat glioma cells can be cultured in the sorbitol-containing medium in the absence of glucose. With sorbitol substituting for glucose in the culture medium, effects of glucose deprivation on cellular functions like sugar transport and metabolism can be investigated in glial cultures for an extended period of time.

Short photoperiod and cold activate brown fat lipoprotein lipase in the Djungarian hamster

Activation of lipoprotein lipase (LPL) in brown fat of the Djungarian hamster ensures substrate supply for nonshivering thermogenesis. Cold acclimation [5 degrees C ambient temperature (Ta)] in long photoperiod [light-dark (LD) 16:8] increased brown fat LPL activity from 4.7 to 22.7 nmol oleate.mg-1.min-1 within 1 day. Slight reduction of this high LPL activity was observed during prolonged cold exposure for up to 4 wk. Deacclimation (transfer from 5 to 23 degrees C Ta) caused total inactivation of brown fat LPL within 4 days. Short photoperiod (LD 8:16) also stimulates brown fat LPL activity. Its effect can be summarized by three different observations. At thermoneutrality short photoperiod elevated LPL activity to 7.1 instead of 4.7 nmol.mg-1.min-1 observed in long photoperiod. Second, at low ambient temperature short photoperiod reinforces the effect of cold acclimation. Maximum LPL activity of cold-exposed Djungarian hamsters averaged 23.7 nmol.mg-1.min-1 in long photoperiod and was elevated to 35.5 nmol.mg-1.min-1 in short photoperiod. Third, inactivation of LPL during deacclimation was delayed in short photoperiod. These results demonstrate that photoperiod as well as ambient temperature may be cooperatively used as environmental cues for seasonal acclimation of brown fat substrate supply for nonshivering thermogenesis.

Characteristics of sorbitol uptake in rat glial primary cultures

Uptake of [U-14C]sorbitol was studied in astrogliarich rat primary cultures. Initial rate of sorbitol uptake is proportional to sorbitol concentration between 20 microM and 400 mM. Sorbitol transport is not inhibited by glucose, fructose, and a variety of structurally related polyols, or by cytochalasin B, an inhibitor of glucose transport. Phloretin, phlorizin, filipin, and n-hexanol, all compounds that alter the properties of biological membranes, and the sulfhydryl reagent p-chloromercuribenzoate inhibit sorbitol uptake to various degrees. Variation in the concentrations of extracellular Na+ and K+ does not affect transfer of sorbitol across the cell membrane. It is concluded that sorbitol is taken up into glial cells by a diffusion process, not involving a carrier and probably not through the lipid bilayer, but through a proteinaceous channel-like structure.

[Oral submucosal pseudosarcomatous nodular fasciitis. Case report]

A case of enoral submucosal pseudosarcomatous fasciitis is described to demonstrate the possible localisation of this lesion in the oral cavity and correlated diagnostic problems. It is a rapid, local invasive growing, self-limiting tumor which seldom exceeds a diameter of 1-2 cm. Malign transformation and metastatic spread did not occur when the tumor was excised. A simple surgical excision is the adequate treatment. The knowledge of this lesion seems to be important for different-diagnostic exclusion of malignant mesenchymal tumors and to prevent in this way a too extended surgical therapy.