A novel integron-like element carrying the metallo-beta-lactamase gene blaIMP

A plasmid-mediated metallo-beta-lactamase gene was cloned from a carbapenem-resistant Serratia marcescens strain, AK9373. The metallo-beta-lactamase gene was identical to the blaIMP, and it was located in the space between an integrase-like gene and an aac(6')-Ib-like gene. The deduced amino acid sequence for the putative integrase gene showed considerable identity (60.9%) to that of the Escherichia coli integrase reported. Sequences similar to the GTTRRRY and an atypical 59-base element containing a 67-bp inverted repeat sequence, which were peculiar to the integrase-dependent recombination, were also conserved in the flanking regions of the blaIMP gene. These findings imply that the metallo-beta-lactamase gene in S. marcescens AK9373 is carried by a novel integron-like element that is mediated by a transferable large plasmid.

Aging effect on neutral amino acid transport at the blood-brain barrier measured with L-[2-18F]-fluorophenylalanine and PET

Neutral amino acids (NAAs) are transported from the blood to the brain using the same carrier system in a competitive fashion. The purpose of this study is to establish a method for evaluating neutral amino acid transport at the blood-brain barrier (BBB) in humans and to examine the aging effect of amino acid transport.

METHODS

A dynamic PET study with L-(2-18F)-fluorophenylalanine (18F-Phe) was performed in 14 normal volunteers (age 21-71 yr; mean +/- s.d., age range 48.0 +/- 17.1 yr). By using a two-compartment model analysis and a weighted integration technique, the influx rate constant K1, the efflux rate constant k2 and distribution volume Vd of 18F-Phe were estimated in various brain structures.

RESULTS

The value of K1 was inversely correlated with plasma NAA concentration (r = -0.69, p < 0.01). The cerebellum showed the highest value of K1, while the white matter showed the lowest. There was no significant change in K1 during aging. The value of k2 was significantly increased with age.

CONCLUSION

No decline of K1 during aging indicated that NAA transport from the blood to the brain is a limiting process of age in amino acid incorporation. Fluorine-18-Phe PET imaging is a feasible method to study NAA transport at the BBB in vivo in humans and can be applied to pathological conditions of the brain.

The immediate phase of c-kit ligand stimulation of mouse bone marrow-derived mast cells elicits rapid leukotriene C4 generation through posttranslational activation of cytosolic phospholipase A2 and 5-lipoxygenase

c-kit ligand (KL) activated mouse bone marrow-derived mast cells (BMMC) for the dose- and time-dependent release of arachidonic acid from cell membrane phospholipids, with generation of leukotriene (LT) C4 in preference to prostaglandin (PG)D2. KL at concentrations of 10 ng/ml elicited half-maximal eicosanoid generation and at concentrations of > 50 ng/ml elicited a maximal generation of approximately 15 ng LTC4 and 1 ng PGD2 per 10(6) cells, with 20% net beta-hexosaminidase release 10 min after stimulation. Of the other cytokines tested, none, either alone or in combination with KL, elicited or modulated the immediate phase of mediator release by BMMC, indicating strict specificity for KL. Activation of BMMC in response to KL was accompanied by transient phosphorylation of cytosolic phospholipase A2 and reversible translocation of 5-lipoxygenase to a cell membrane fraction 2-5 min after stimulation, when the rate of arachidonic acid release and LTC4 production were maximal. BMMC continuously exposed to KL in the presence of IL-10 and IL-1 beta generated LTC4 in marked preference to PGD2 over the first 10 min followed by delayed generation of PGD2 with no LTC4 over several hours. Pharmacologic studies revealed that PGD2 generation in the immediate phase depended on prostaglandin endoperoxide synthase (PGHS)-1 and in the delayed phase on PGHS-2. Thus, KL provided a nonallergic stimulus for biphasic eicosanoid generation by mast cells. The immediate phase is dominated by LTC4 generation with kinetics and postreceptor biosynthetic events similar to those observed after cell activation through the high affinity IgE receptor, whereas the delayed phase of slow and selective PGD2 production is mediated by induction of PGHS-2.

Role of mucosal microcirculation in gastric lesions induced by lateral hypothalamic lesions in rats

To evaluate the pathophysiology underlying gastric mucosal lesions induced by lateral hypothalamic (LH) lesions, we investigated the changes in acid secretion, gastric mucosal blood flow, gastric mucus and mucosal integrity in the corpus during the 4 h period and 48 h after the production of bilateral electrolytic LH lesions in male Sprague-Dawley rats. Gastric mucosal lesions were macroscopically produced 24 h (63%) and 48 h (83%) after LH lesions, although there were no visible lesions at 7 h. Gastric acid secretion was significantly increased 48 h after LH lesions, compared with that in the control group. Gastric mucosal blood flow and transmucosal potential difference (PD) in the LH lesion group immediately decreased after LH lesions and did not recover during 4 h and at 48 h. On the contrary, in the control group, gastric mucosal blood flow decreased after the brain surgery but soon recovered, and there was no significant change in PD. LH lesions resulted in the reduction of intramucosal mucus to 50% 3 h after LH lesions. Moreover, we exposed the stomach to 10 mmol/L taurocholic acid (TCA) 3 h after LH lesions to examine the disruption in gastric mucosal defensive function in rats with LH lesions. The recovery of the reduced PD by TCA was slow and gastric mucosal lesions were easily formed in the LH lesion group. These results suggest that gastric mucosal ischaemia after lesioning of LH immediately results in the disruption of mucosal defensive function before the formation of visible gastric lesions, and predisposes to the formation of gastric mucosal lesions by a delayed increase in acid secretion.

Interleukin 4 suppresses c-kit ligand-induced expression of cytosolic phospholipase A2 and prostaglandin endoperoxide synthase 2 and their roles in separate pathways of eicosanoid synthesis in mouse bone marrow-derived mast cells

Mouse bone marrow-derived mast cells (BMMCs) developed with interleukin 3 (IL-3) can be stimulated by c-kit ligand (KL) and accessory cytokines over a period of hours for direct delayed prostaglandin (PG) generation or over a period of days to prime for augmented IgE-dependent PG and leukotriene (LT) production, as previously reported. We now report that IL-4 is counterregulatory for each of these distinct KL-dependent responses. BMMCs cultured for 4 days with KL + IL-3 or with KL + IL-10 produced 5- to 7-fold more PGD2 and approximately 2-fold more LTC4 in response to IgE-dependent activation than BMMCs maintained in IL-3 alone. IL-4 inhibited the priming for increased IgE-dependent PGD2 and LTC4 production to the level obtained by activation of BMMCs maintained in IL-3 alone with an IC50 of approximately 0.2 ng/ml. IL-4 inhibited the KL-induced increase in expression of cytosolic phospholipase A2 (cPLA2) but had no effect on the incremental expression of PG endoperoxide synthase 1 (PGHS-1) and hematopoietic PGD2 synthase or on the continued baseline expression of 5-lipoxygenase, 5-lipoxygenase activating protein, and LTC4 synthase. BMMCs stimulated by KL + IL-10 for 10 h exhibited a delayed phase of PGD2 generation, which was dependent on de novo induction of PGHS-2. IL-4 inhibited the induction of PGHS-2 expression and the accompanying cytokine-initiated delayed PGD2 generation with an IC50 of approximately 6 ng/ml. IL-4 had no effect on the expression of PGHS-2 and the production of PGD2 elicited by addition of IL-1 beta to the combination of KL + IL-10. IL-4 had no effect on the immediate phase of eicosanoid synthesis elicited by KL alone or by IgE and antigen in BMMCs maintained in IL-3. Thus, the counterregulatory action of IL-4 on eicosanoid generation is highly selective for the induced incremental expression of cPLA2 and the de novo expression of PGHS-2, thereby attenuating time-dependent cytokine-regulated responses to stimulation via Fc epsilon receptor I and stimulation via c-kit, respectively.

Mechanism of Helicobacter pylori-associated gastric mucosal injury

Helicobacter pylori infection is associated with gastric mucosal damage and the infiltration of neutrophils. Myeloperoxidase from neutrophils produces hypochlorous acid, which yields monochloramine in the presence of ammonia produced by urease enzyme of Helicobacter pylori. The target cells of gastric mucosal damage are gastric mucosal cells and endothelial cells. We therefore tested the hypothesis that ammonium, hypochlorous acid, and monochloramine damage the target cells. We studied the in vitro cytotoxic effects of ammonium chloride, sodium hypochlorite, monochloramine, and activated neutrophils on the target cells. Cytotoxicity was measured by a 51Cr-release assay. Ammonium chloride, sodium hypochlorite, and monochloramine were toxic to labeled cells in a concentration dependent manner. The toxicity of these agents was in the order monochloramine > sodium hypochlorite >> ammonium chloride. Incubation of labeled cells with activated neutrophils, Helicobacter pylori, and urea resulted in cytolysis. These cytotoxicities were significantly inhibited by the scavenger of hypochlorous acid, taurine. Monochloramine is more toxic to the target cells than ammonium chloride. Although ammonium chloride at neutral pH by itself has little direct damaging effect on the gastric mucosa, it is damaging to the gastric mucosa through a reaction with hypochlorous acid, suggesting that it plays a role in Helicobacter pylori-associated gastric damage.

Prevention of autoimmune symptoms in autoimmune-prone mice by elimination of B-1 cells

Our recent studies on an autoantibody-transgenic mouse line demonstrated that peritoneal B-1 cells are responsible for autoimmune symptoms. However, whether B-1 cells in the peritoneum are generally involved in the pathogenesis of autoimmune disease remains controversial. To test the possible involvement of peritoneal B-1 cells in autoimmune symptoms of autoimmune-prone NZB mice, we eliminated the peritoneal cells by hypotonic shock with repeated i.p. injection of distilled water every 7 days into neonatal or 8-week-old NZB mice. By this treatment, B-1 cells, which self-renew within the peritoneal cavity, are expected to be preferentially eliminated, while other peritoneal cells can be easily supplied from bone marrows after this treatment. Indeed, in distilled water-treated old NZB mice, the number of B-1 cells decreased in spleen as well as in lamina propria of the gut but the numbers of conventional B cells and T cells did not change. Moreover, the production of autoantibodies against erythrocytes significantly decreased and the occurrence of autoimmune hemolytic anemia was reduced in 12-month-old treated NZB mice. Similarly, the elimination of peritoneal cells of NZB/NZW (NZB/W) F1 mice by water injection decreased anti-DNA IgG antibodies in the sera and reduced the pathological changes of the kidney. These results suggest that peritoneal B-1 cells may be a source of autoantibody-producing cells in autoimmune diseases of NZB and NZB/W F1 mice.

The rat neutrophil low-affinity Fc receptor for IgG: molecular cloning and functional characterization

A complementary DNA (cDNA) clone encoding rat Fc gamma receptor II (Fc gamma RII) was isolated from rat neutrophils and characterized. The cDNA encodes a type I transmembrane protein with 285 amino acids having an extracellular domain consisting of two immunoglobulin-like domains (179 amino acids), a transmembrane domain (26 amino acids), and a cytoplasmic domain (47 amino acids). The nucleotide sequences are identical to that of recently cloned Fc gamma RII from rat mast cells. This protein was expressed on FcR-negative Chinese hamster ovary (CHO) cells. The characterization of cDNA-transfected CHO cells clearly indicated that the protein encoded by the cDNA clone binds guinea-pig IgG1 and IgG2 complexes and unexpectedly binds monomeric rat IgG1, but not IgG2. Furthermore, the affinity for immune complexes was significantly augmented by protease treatment of transfectants. In addition, endocytosis of immune complex was noted in transfectants.

Biological effects of active oxygen on an X-ray-sensitive mutant mouse cell line (SL3-147)

The biological effects of active oxygen species were examined in a mutant mouse cell line (SL3-147) that is deficient in the repair of DNA double-strand breaks. This mutant cell line shows different sensitivities to X-rays, hydrogen peroxide, paraquat and menadione when compared to the wild-type cell line (LTA). SL3-147 was more sensitive to X-rays, hydrogen peroxide and paraquat, but was less sensitive to menadione in side by side comparisons to LTA cells. The greater number of DNA double-strand breaks in SL3-147 appears to account for the line's greater sensitivity to X-rays and paraquat. DNA damage other than double-strand breaks or injury to non-DNA targets, however, is responsible for the differences between LTA and SL3-147 in their sensitivities to hydrogen peroxide and menadione.

Neurochemical changes related to ageing in the senescence-accelerated mouse brain and the effect of chronic administration of nimodipine

The levels of neurotransmitters and related metabolic enzyme activities in the brain of young-adult (3 months old), aged (11 months old) and nimodipine-administered (11 months old) senescence-accelerated mouse (SAM) were compared. Nimodipine, a calcium antagonist, was administered orally for 5 months. Acetylcholine (ACh), serotonin (5-HT) and dopamine (DA) levels all decreased with age but this decrease was attenuated by nimodipine. Choline acetyltransferase and choline esterase activities increased with age, and nimodipine enhanced their activities. Tryptophan hydroxylase activity was not affected by age or nimodipine administration. Monoamine oxidase-A activity increased with age, and was decreased by nimodipine administration. These results suggest that SAM rapidly undergoes neurochemical changes which are considered to be part of the normal aging process, and these changes were attenuated by chronic administration of nimodipine.

[A pharyngeal carcinoma after resection of a upper esophageal web]

Dysphagia suddenly progressed in a 69-year-old woman who had a 50-year history of intermittent difficulty in swallowing solid food. A thick circumferential who in the upper esophagus was extensive enough to be the cause of dysphagia. There was another thin semicircular web in the pharynx. Bouginage resulted in only 6-months relief of symptoms, and the same esophageal who was reformed with the same severe symptoms 3 years later. Surgical resection of the esophageal web was performed. Extensive pharyngeal carcinoma was found 4 years after surgery. She died of heart failure during combination therapy of irradiation and chemotherapy.

Effects of antiepileptic drugs on EEG background activity in children with epilepsy: initial phase of therapy

The effects of antiepileptic drugs (AED) on EEG background activity were evaluated in 37 newly treated children with epilepsy, compared with 46 age-matched healthy controls. Before AED therapy, the children with epilepsy, both partial (treated with carbamazepine, CBZ group) and generalized seizures (treated with valproic acid, VPA group), already exhibited significant slowing of EEG with increased delta and decreased alpha power. Following 3 to 6 months of AED therapy, this EEG slowing was enhanced in the CBZ group and reduced in the VPA group. Following 1 year of AED therapy, an increase in frequency was recognized in the CBZ group. These results suggest that 1) most children with epilepsy already exhibit slowing of the EEG at the onset of seizures, which may reflect CNS developmental deficit, 2) the short-term effects on EEG are different between CBZ and VPA, and 3) EEG development with age continues under continuous AED administration. The EEG background activity in children with epilepsy is affected by many factors, which include the underlying CNS dysfunction of the epilepsy itself and also AED therapy (type of AEDs, duration of therapy, etc).

Rapid calculation of regional cerebral blood flow and distribution volume using iodine-123-iodoamphetamine and dynamic SPECT

Iodine-123-iodoamphetamine (IMP) is commonly used as a flow tracer for SPECT due to its large first-pass extraction fraction. Significant clearance from the brain, however, causes changes in distribution and underestimation of CBF values when a conventional microsphere model is applied to prolonged data acquisition. We have developed a rapid method to calculate CBF images in which clearance effects are taken into account.

METHODS

A dynamic SPECT scan was obtained from five subjects (four patients with cerebral infarctions and one healthy volunteer) following intravenous injection of IMP lasting 1 min. The arterial input function was obtained by frequent blood sampling and measurement of the octanol extraction ratio. The dynamic images were weighted and integrated so that the look-up table procedures yielded values of CBF and distribution volume (Vd) simultaneously.

RESULTS

Calculated values for CBF and Vd were consistent with those determined by nonlinear least squares fitting [CBF: Y = 1.03X-0.30 (ml/100 ml/min), r = 0.998, p < 0.001; Vd: Y = 0.99X-0.11 (ml/ml), r = 0.99, p < 0.001] and calculated CBF correlated significantly with CBF measured by PET [Y = 0.85X-0.15 (ml/100 ml/min), r = 0.92, p < 0.001].

CONCLUSION

This technique is valid for estimating CBF.

Species-specific mechanism in rat Leydig cell tumorigenesis by procymidone

To clarify the mechanism of species difference in the induction of testicular interstitial cell tumor (ICT, Leydig cell tumor) between rats and mice, male Sprague-Dawley rats and ICR mice were fed procymidone at dietary concentrations of 700, 2000 or 6000 ppm and 1000, 5000, or 10,000 ppm, respectively, for 3 months. The Leydig cell functions were evaluated by serum testosterone and luteinizing hormone (LH) levels, testosterone levels in the testis, LH levels in the pituitary, the capacity of the testis to respond to gonadotropin stimulation, i.e., the production of testosterone in vitro, and by the testicular binding of labeled human chorionic gonadotropin (hCG). Measurement of testosterone and LH levels in rat serum, the testis, or the pituitary showed that both hormones were enhanced throughout the 3-month treatment period. The hypergonadotropism was associated with the increase of interstitial cell response to hCG in vitro for up to 3 months. As with rats, both serum and pituitary LH were increased in mice at 4 weeks but not at 13 weeks. However, in contrast to rats, no significant increase in testosterone was observed in mice either in vivo or ex vivo during the course of the study. This suggests a difference between the rat and mouse in the response of the Leydig cell to the LH stimulation associated with procymidone administration. These differences in the response of interstitial cells to procymidone may be the basis for the distinct species responses to procymidone-induced Leydig cell tumorigenesis. The sustained response of the Leydig cells to stimulation in the rat results in chronic hyperplasia and subsequent benign tumor formation, while the attenuated response of Leydig cells in the mouse is associated with neither hyperplasia nor neoplasia.

Primary intracranial plasma-cell granuloma: a case report and review of the literature

BACKGROUND

Plasma-cell granulomas, which are characterized by the non-neoplastic proliferation of plasma cells, are primarily found in the lungs and upper respiratory tracts, and are extremely rare in the central nervous system.

METHODS

An intracranial tumor of an 11-year-old boy was evaluated by histologic and radiologic examination.

RESULTS

An 11-year-old boy had a 2-month history of mild headache and nausea. A computed tomography scan showed a round, slightly high-density mass surrounded by marked edema in the left frontal lobe. On magnetic resonance imaging (MRI), the mass had a slightly high signal intensity on the T1-weighted image and marked low signal intensity on the T2-weighted image. It was heterogenously enhanced with gadolinium-DTPA. Microscopic examination demonstrated a non-neoplastic mixed cell population with a predominance of plasma cells. Immunohistochemical staining revealed that it was characterized by a polyclonal plasma cell population.

CONCLUSION

Our extensive search of the literature indicated this to be the ninth reported case of intracranial plasma cell granulation. The MRI was very useful for evaluating the extent of the intracranial lesions. The tumor was removed surgically and did not recur during a 2-year follow-up with no radiation therapy.

Granulomatous lesions caused by Pseudomonas aeruginosa in the ostrich (Struthio camelus)

Granulomatous lesions were observed in imported ostriches aged 3 months. Clinically, the birds showed lassitude, incoordination, and inappetence. At necropsy, yellowish white nodules often accompanied by a pseudodiphtheritic membrane were found in the oral, pharyngeal, tracheal and air sac mucosae, the lungs, oesophageal serosa, and abdominal peritoneum. Histopathological examination revealed purulent granulomatous lesions containing central bacterial colonies with an outer shell and club formation. The bacteria were small Gram-negative bacilli, which showed positive immunohistochemical staining for Pseudomonas aeruginosa. The bacterial colonies were positive for chicken IgM. Clubs around the colonies were negative for P. aeruginosa and chicken IgM. Such findings have not previously been reported in the ostrich.

Critical amino acids responsible for conferring calcium channel characteristics are located on the surface and around beta-turn potentials of channel proteins

Calcium ion is thought to be one of the initial signals in the process of synaptic modification. Various reports have described that the critical amino acids responsible for determining calcium permeability of ion channels are glutamic acid, glutamine, arginine, and asparagine. By using a computational method (MacPROT) distinguishing transmembrane, globular, and surface sequences of proteins, the present work predicts that the critical amino acids exist within surface regions of the proteins. Furthermore, occurrence of beta-turn probabilities can be predicted around these critical residues by the protein conformational prediction method of Chou and Fasman. The results suggest that the critical amino acids exist at hydrophilic spaces or canals of membranous channel proteins and that the redirection potential of the protein chain induced by the turn structures provides the conformational change requisite for the ion selectivity and gating (opening/closing) of the channels.

Neutrophil-independent myocardial dysfunction during an early stage of global ischemia and reperfusion of isolated hearts

The effect of global ischemia and reperfusion on the expression of cytokine genes and cell adhesion molecules by myocardial tissues and neutrophils was studied by using the Langendorff model. Although cardiac function deteriorated after reperfusion of ischemic hearts, there was no evidence of inflammation and myocardial degeneration, which is in contrast to previous findings that neutrophil-mediated inflammation is a critical step in post-ischemic reperfusion injury in regional ischemia. Flow cytometry analysis demonstrated that the global ischemia and reperfusion did not affect the expression of adhesion molecules on neutrophils. We also examined the expression of various cytokines which are involved in inflammatory responses. Only interleukin 1 alpha was induced after the reperfusion of the ischemic hearts. These results suggest that neutrophils barely contribute to the myocardial dysfunction and IL-1 alpha may play a role in post-ischemic myocardial dysfunction during the early stage of reperfusion.

Effect of chronic L-dopa administration on serum luteinizing hormone levels in male rats

We examined whether the repeated oral administration with a high dose of L-3-(3,4-dihydroxyphenyl)-alanine (L-DOPA) in 0.5% carboxymethyl cellulose increases serum luteinizing hormone (LH) levels in male rats. Serum LH levels were increased 4 h after a single administration of 1000 mg/kg L-DOPA to male rats, and returned to control levels within 8 h after administration. Four hours after a single administration, serum LH levels were significantly increased by L-DOPA at 1000 mg/kg, but not at 20, 100 or 200 mg/kg. Decreases in body weight and relative weight of the prostate were observed after 7 and 14 days of administration of 1000 mg/kg per day L-DOPA, but no changes were observed in weight of the testis, epididymis or seminal vesicle. The administration of L-DOPA at 500 or 1000 mg/kg per day for 7 or 14 days resulted in increased basal serum LH levels and decreased basal serum prolactin levels 24 h after the last administration. Serum testosterone levels tended to be higher in treated than in control rats. The levels of two metabolites of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), in rats treated with 500 mg/kg per day tended to be slightly higher than those in control rats after 7 days of administration. Levels of DA, DOPAC and HVA were significantly increased after 7 and 14 days of administration of 1000 mg/kg per day and after 14 days of administration of 5000 mg/kg per day. The level of norepinephrine, but not its metabolite 3-methoxy-4-hydroxyphenylglycol, was significantly increased after only 7 days of administration of 1000 mg/kg per day. No significant changes were observed in levels of 5-hydroxytryptamine or its metabolite 5-hydroxyindole-3-acetic acid with administration of 500 or 1000 mg/kg per day. These findings suggest that a prolonged treatment with a high dose of L-DOPA in male rats induces release of LH from the pituitary, resulting in sustained elevation of LH levels in peripheral circulation.