Helicobacter pylori Infection and Gastric Autoimmune Diseases: Is There a Link?

Background. Helicobacter pylori is thought to be involved in atrophic body gastritis. We explored the prevalence of H. pylori infection in asymptomatic subjects with gastric parietal cell antibodies, as well as in patients with pernicious anemia, to evaluate a possible role of H. pylori gastric infection in gastric autoimmunity. Patients and Methods. We studied 79 consecutive asymptomatic subjects with parietal cell antibodies, 24 patients with pernicious anemia, and 66 parietal cell antibody‐negative controls. All patients underwent gastric biopsies for histology and detection of H. pylori. Red blood cell count and volume, serum levels of gastrin, pepsinogen I, iron, folic acid, vitamin B₁₂, and circulating antibodies to H. pylori and to intrinsic factor were also determined. Results. We found an atrophic body gastritis in 14 of the 79 asymptomatic subjects with parietal cell antibodies (18%) and in 2 of the 66 controls (3%) (p = .01). Mean levels of gastrin were increased (p < .0001), while those of pepsinogen were reduced (p < .001) compared with controls. H. pylori was identified at the gastric level and/or circulating anti‐H. pylori antibodies were detected in 46 parietal cell antibody‐positive subjects (58%) compared with 26 controls (39%) (p = .03). In patients with pernicious anemia we found an atrophic body gastritis in 18 of 24 cases (75%) (p < .001 vs. controls). Mean levels of gastrin were markedly increased (p < .0001) and those of pepsinogen I decreased (p < .0001) relative to controls. Only five of these patients (21%) had evidence of H. pylori infection compared with 46 of the parietal cell antibody‐positive subjects (58%) (p = .003) and 26 of the controls (39%). Considering all patients with gastric autoimmunity (i.e. with parietal cell antibodies and/or with pernicious anemia), H. pylori was found in 44 of 72 of those without atrophy (61%) but in 6 of 31 with gastric body atrophy (19%) (p < .001), indicating that H. pylori infection is greatly reduced when gastric acid secretion decreases. Conclusions. The frequent detection of H. pylori infection in subjects with early gastric autoimmunity, indicated by the presence of parietal cell antibodies, suggests that H. pylori could have a crucial role in the induction and/or the maintenance of autoimmunity at the gastric level.     

The influence of environment,sex, and innate timing mechanisms on body temperature patterns of free-ranging black-tailed prairie dogs (Cynomys ludovicianus)

Mechanisms that influence body temperature patterns in black-tailed prairie dogs are not well understood. Previous research on both free-ranging and laboratory populations of black-tailed prairie dogs (Cynomys ludovicianus) has suggested that reductions in ambient temperature and food and water deprivation are the primary factors that stimulate torpor in this species. In other species, however, torpor has been shown to be influenced by a multitude of factors, including innate circadian and circannual timing mechanisms, energy status, and reproductive behaviors. Our objective was to clarify the influence of weather, sex, and intrinsic timing mechanisms on the body temperature patterns of free-ranging black-tailed prairie dogs. We monitored body temperatures of eight adult (>1 yr) prairie dogs from November 1999 to June 2000. Prairie dogs showed distinct daily and seasonal body temperature patterns, which reflected changes in ambient temperatures that occurred during these periods. These patterns of daily and seasonal heterothermy suggest that body temperature patterns of black-tailed prairie dogs may be driven by an innate timing mechanism. All prairie dogs entered torpor intermittently throughout winter and spring. Torpor bouts appeared to be influenced by precipitation and reductions in ambient temperature. Our results also suggest that reproductive behaviors and circadian timing may influence torpor in this species.     

Stereoselective single-dose kinetics of citalopram and its metabolites in rats

The single-dose kinetics of the enantiomers of citalopram (CIT) and its metabolites, demethylcitalopram (DCIT) and didemethylcitalopram (DDCIT), were investigated after administration of 10, 20, or 100 mg/kg (s.c.) rac-CIT to rats. Samples from serum and two brain regions were collected 1, 3, 10, or 20 h postdose for HPLC analysis. In the 100 mg/kg rats, the enantiomeric (S/R) serum concentration ratios of CIT decreased during the study period (0.93 at 1 h vs. 0.59 at 20 h; P < 0.001). In the 10 and 20 mg/kg rats, the decrease in serum S/R CIT ratios was not so evident as in the 100 mg/kg rats. In all three groups the S/R CIT ratio was almost the same in the brain as in serum, although both CIT enantiomer levels in the brain were found to be 5-10 times higher than the levels in serum. The serum and brain metabolite levels were low in the 10 and 20 mg/kg rats, whereas the levels increased during the study period in the 100 mg/kg rats. In conclusion, the CIT enantiomers were shown for the first time to be stereoselectively metabolized after single-dose administration to rats, as previously shown in steady-state dosing studies in humans and rats.     

Immunomodulatory effects of probiotic bacteria DNA: IL-1 and IL-10 response in human peripheral blood mononuclear cells

A new therapeutic approach for inflammatory bowel diseases is based on the administration of probiotic bacteria. Prokaryotic DNA contains unmethylated CpG motifs which can activate immune responses, but it is unknown whether bacterial DNA is involved in the beneficial effects obtained by probiotic treatment. Peripheral blood mononuclear cells (PBMC) from healthy donors were incubated with pure DNA of eight probiotic strains and with total bacterial DNA from human feces collected before and after probiotic ingestion. Cytokine production was analyzed in culture supernatants. Modification of human microflora after probiotic administration was proven by polymerase chain reaction analysis. Here we show that Bifidobacterium genomic DNA induced secretion of the antiinflammatory interleukin-10 by PBMC. Total bacterial DNA from feces collected after probiotic administration modulated the immune response by a decrease of interleukin-1 beta and an increase of interleukin-10.     

Stereospecificity of myo-inositol hexakisphosphate dephosphorylation by a phytate-degrading enzyme of Escherichia coli

Using a combination of high-performance ion chromatography analysis and kinetic studies, the stereospecificity of myo-inositol hexakisphosphate dephosphorylation by the phytate-degrading enzyme P2 of Escherichia coli was established. High-performance ion chromatography revealed that the phytate-degrading enzyme P2 of E. coli degrades myo-inositol hexakisphosphate by stepwise dephosphorylation via D/L-Ins(1,2,3,4,5)P(5), D/L-Ins(2,3,4,5)P(4), D/L-Ins(2,4,5)P(3) or D/L-Ins(1,2,4)P(3), D/L-Ins(1,2)P(2) or Ins(2, 5)P(2) or D/L-Ins(4,5)P(2) to finally Ins(2)P or Ins(5)P. Kinetic parameters for myo-inositol pentakisphosphate hydrolysis by E. coli and wheat phytase, respectively, showed that the myo-inositol pentakisphosphate intermediate produced either by the phytate-degrading enzyme of wheat or E. coli are not identical. The absolute configuration of the myo-inositol pentakisphosphate isomer produced by the E. coli enzyme was determined by taking into consideration that wheat phytase produces predominantly the D-Ins(1, 2,3,5,6)P(5) isomer (Lim, P.E., Tate, M.E., 1973. The phytases: II. Properties of phytase fraction F(1) and F(2) from wheat bran and the myo-inositol phosphates produced by fraction F(2). Biochim. Biophys. Acta 302, 326-328). The data demonstrate that the phytate-degrading enzyme P2 of E. coli dephosphorylates myo-inositol hexakisphosphate in a stereospecific way by sequential removal of phosphate groups via D-Ins(1,2,3,4,5)P(5), D-Ins(2,3,4,5)P(4), D-Ins(2,4,5)P(3), Ins(2,5)P(2) to finally Ins(2)P (notation 6/1/3/4/5).     

Parenteral nutrition with lipid or glucose suppresses liver growth and response to GH in adolescent male rats

Our aim was to investigate the effects of modifying the carbohydrate-to-lipid ratio of parenteral nutrition (PN) on body composition and the anabolic actions of insulin-like growth factor I (IGF-I) and growth hormone (GH). Adolescent male Sprague-Dawley rats were randomized to receive 7 days of GH, IGF-I (3.5 mg. kg(-1). day(-1) for both) or placebo while receiving high-carbohydrate PN (CHO-PN), high-lipid PN (L-PN), or an oral diet (chow) (the PN protocols were isonitrogenous and isocaloric). PN impaired muscle growth, which was reversed by GH in the CHO-PN group only (P < 0.03). PN increased carcass lipid (P < 0.02), the effect being greater in the L-PN than in the CHO-PN group (P < 0.001). Visceral lean tissue growth was significantly impaired by PN (P < 0.001). IGF-I reversed this impairment, but GH had no effect. PN impaired the normal increase in hepatic protein and DNA (P < 0.001) and produced liver steatosis (P < 0.001). However, this steatosis was less in L-PN than in CHO-PN (P < 0.001). Serum IGF-I and the acid-labile subunit (ALS) were decreased by PN (P < 0.001) and were not affected by GH during PN treatment. However, GH significantly increased serum ALS concentrations in the chow-fed rats (P = 0.032). In conclusion, modifying the CHO-to-L ratio of PN had no significant effect on IGF-I action, but CHO-PN increased the peripheral effect of GH. L-PN increased carcass lipid significantly and decreased hepatic steatosis. Nevertheless, PN caused significant liver steatosis and profound impairment of hepatic cell growth, which was associated with relative hepatic GH resistance.     

Activity and stability of hyperthermophilic enzymes: a comparative study on two archaeal β-glycosidases

Sβgly and CelB are well-studied hyperthermophilic glycosyl hydrolases, isolated from the Archaea Sulfolobus solfataricus and Pyrococcus furiosus, respectively. Previous studies revealed that the two enzymes are phylogenetically related; they are very active and stable at high temperatures, and their overall three-dimensional structure is very well conserved. To acquire insight in the molecular determinants of thermostability and thermoactivity of these enzymes, we have performed a detailed comparison, under identical conditions, of enzymological and biochemical parameters of Sβgly and CelB, and we have probed the basis of their stability by perturbations induced by temperature, pH, ionic strength, and detergents. The major result of the present study is that, although the two enzymes are remarkably similar with respect to kinetic parameters, substrate specificity, and reaction mechanism, they are strikingly different in stability to the different physical or chemical perturbations induced. These results provide useful information for the design of further experiments aimed at understanding the structure–function relationships in these enzymes. Received: May 20, 1999 / Accepted: January 10, 2000     

Recombining germline-derived CDR sequences for creating diverse single-framework antibody libraries

We constructed a single-chain Fv antibody library that permits human complementarity-determining region (CDR) gene fragments of any germline to be incorporated combinatorially into the appropriate positions of the variable-region frameworks VH-DP47 and VL-DPL3. A library of 2 x 109 independent transformants was screened against haptens, peptides, carbohydrates, and proteins, and the selected antibody fragments exhibited dissociation constants in the subnanomolar range. The antibody genes in this library were built on a single master framework into which diverse CDRs were allowed to recombine. These CDRs were sampled from in vivo-processed gene sequences, thus potentially optimizing the levels of correctly folded and functional molecules, and resulting in a molecule exhibiting a lower computed immunogenicity compared to naive immunoglobulins. Using the modularized assembly process to incorporate foreign sequences into an immunoglobulin scaffold, it is possible to vary as many as six CDRs at the same time, creating genetic and functional variation in antibody molecules.     

Characterization of the Porphyridium cruentum Chl a-binding LHC by in vitro reconstitution: LHCaR1 binds 8 Chl a molecules and proportionately more carotenoids than CAB proteins

The Porphyridium cruentum light harvesting complex (LHC) binds Chl a, zeaxanthin and -carotene and comprises at least 6 polypeptides of a multigene family. We describe the first in vitro reconstitution of a red algal light-harvesting protein (LHCaR1) with Chl a/carotenoid extracts from P. cruentum. The reconstituted pigment complex (rLHCaR1) is spectrally similar to the native LHC I, with an absorption maximum at 670 nm, a 77 K fluorescence emission peak at 677 nm (ex. 440 nm), and similar circular dichroism spectra. Molar ratios of 4.0 zeaxanthin, 0.3 -carotene and 8.2 Chl a per polypeptide for rLHCaR1 are similar to those of the native LHC I complex (3.1 zeaxanthin, 0.5 -carotene, 8.5 Chl a). The binding of 8 Chl a molecules per apoprotein is consistent with 8 putative Chl-binding sites in the predicted transmembrane helices of LHCaR1. Two of the putative Chl a binding sites (helix 2) in LHCaR1 were assigned to Chl b in Chl a/b-binding (CAB) LHC II [Kühlbrandt et al. (1994) Nature 367: 614–21]. This suggests either that discrimination for binding of Chl a or Chl b is not very specific at these sites or that specificity of binding sites evolved separately in CAB proteins. LHCaR1 can be reconstituted with varying ratios of carotenoids, consistent with our previous observation that the carotenoid to Chl ratio is substantially higher in P. cruentum grown under high irradiance. Also notable is that zeaxanthin does not act as an accessory light-harvesting pigment, even though it is highly likely that it occupies the position assigned to lutein in the CAB LHCs.This revised version was published online in October 2005 with corrections to the Cover Date.     

Effects of 4wk of hindlimb suspension on skeletal muscle mitochondrial respiration in rats

Yajid, Fatima, Jacques G. Mercier, Béatrice M. Mercier, Hervé Dubouchaud, and Christian Préfaut.Effects of 4 wk of hindlimb suspension on skeletal musclemitochondrial respiration in rats. J. Appl.Physiol. 84(2): 479-485, 1998.We investigated inrats the effect of 4 wk of hypodynamia on the respiration of mitochondria isolated from four distinct muscles [soleus,extensor digitorum longus, tibial anterior, and gastrocnemius(Gas)] and from subsarcolemmal (SS) and intermyofibrillar (IMF)regions of mixed hindlimb muscles that mainly contained the four citedmuscles. With pyruvate plus malate as respiratory substrate, 4 wk ofhindlimb suspension produced an 18% decrease in state3 respiration for IMF mitochondria compared with thosein the control group (P < 0.05). TheSS mitochondria state 3 were notsignificantly changed. Concerning the four single muscles, themitochondrial respiration was significantly decreased in the Gasmuscle, which showed a 59% decrease in state3 with pyruvate + malate(P < 0.05). The other musclespresented no significant decrease in respiratory rate in comparisonwith the control group. With succinate + rotenone, there was nosignificant difference in the respiratory rate compared with therespective control group, whatever the mitochondrial origin (SS, orIMF, or from single muscle). We conclude that 4 wk of hindlimbsuspension alters the respiration of IMF mitochondria in hindlimbskeletal muscles and seems to act negatively on complex I of theelectron-transport chain or prior sites. The muscle mitochondria mostaffected are those isolated from the Gas muscle.