Developmental regulation of beta-galactoside alpha 2,6-sialyltransferase in small intestine epithelium

A striking biochemical alteration to the epithelium of the small intestine upon weaning is the loss of microvillar sialic acids. Antibody and cDNA probes to the beta-galactoside alpha 2,6-sialyltransferase (SiaT-1, EC 2.4.99.1) were used to characterize the expression of this sialyltransferase in the small intestine of suckling rats. SiaT-1 mRNA and protein in the intestinal epithelium are rapidly lost upon weaning, in agreement with the loss of mucosal sialic acids and general sialyltransferase activity. Developmental repression of SiaT-1 is manifested in a proximal to distal gradient; SiaT-1 mRNA and protein are lost first from the duodenum and persist the longest in the ileum. We have previously documented that SiaT-1 gene expression can be transcriptionally initiated from a number of distinct tissue-specific promoter regions. Here, by criteria of mRNA mobility on agarose gels, primer extension analysis, and differential Northern hybridization, we show that the promoter previously considered to be liver-specific is operative in SiaT-1 expression in the small intestine of suckling animals. Comparison of this SiaT-1 promoter region with promoter regions of other genes exhibiting dual intestine-hepatic tissue specificity revealed a number of striking sequence similarities. Regulatory implications and consequences of small intestinal SiaT-1 expression in suckling but not in weaned animals are discussed.

Effect of aging, position, and temperature on the threshold volume triggering pharyngeal swallows

BACKGROUND/AIMS

Swallows triggered by direct stimulation of pharyngeal structures may help to prevent aspiration by emptying the pharynx. The aims of this study were to compare the biomechanical events of the pharyngeal and primary swallow, determine the threshold volume of liquid required to trigger the pharyngeal swallows, and determine the effect of aging, position, and temperature on this threshold volume.

METHODS

Concurrent manometry, video fluoroscopy, and video endoscopy were used to study young and elderly healthy volunteers.

RESULTS

During pharyngeal swallows, in contrast to primary swallows, the free portion of the tongue did not make contact with the hard palate. In addition, pharyngeal swallows did not result in oral bolus clearance. All other biomechanical events, including deglutitive glottal function, were similar in both types of swallows. The threshold volume for pharyngeal swallows in young volunteers was significantly smaller than in the elderly (P < 0.01). Temperature and position did not have significant effects on threshold volume.

CONCLUSIONS

Swallowing is readily induced by water stimulation of the pharynx. Pharyngeal swallows do not induce lingual peristalsis or clearance of oral content. The threshold volume of the pharyngeal swallow is significantly higher in the elderly than in the young, but it is not affected by body position or bolus temperature.

[Establishment of immuno-PCR technique for the detection of tumor associated antigen MG7-Ag on the gastric cancer cell line]

The gastric cancer associated antigen McAb MG7-Ag was detected by means of a newly established method, termed immuno-PCR. A McAb-recombinant DNA chimeric molecule was made which possesses bispecific binding affinity for antigen that had been immobilized on microtiter wells and the segment of the attached DNA was amplified by PCR. The antigen of gastric cancer cell line KATO III was monitored by this method. Analysis of PCR products by agarose gel electrophoresis after staining with ethidium bromide allowed as few as 20 cells to be detected readily and reproducibly. Immuno-PCR showed a 10(4) enhancement in detection sensitivity compared with ELISA assay. When the same numbers of cells (2 x 10(6)/ml) were immobilized and then the serial diluted chimeric molecule was added, 3.8 x 10(-14) moles and 3.0 x 10(-11) moles were needed to give positive results with the immuno-PCR and ELISA assay, respectively. Therefore, immuno-PCR could give an enormous amplification capability with good specificity, and has a sensitivity much higher than any existing techniques for antigen detection.

Chemical studies of Chinese licorice-roots. I. Elucidation of five new flavonoid constituents from the roots of Glycyrrhiza glabra L. collected in Xinjiang

From the air-dried roots of Glycyrrhiza glabra L. (Leguminosae) collected in Xinjiang province, China ("Shinkyo-Kanzo" in Japanese), five new flavonoid compounds named glucoliquiritin apioside (1) (a flavonone bisdesmoside), prenyllicoflavone A (5) (a bisprenylflavone), shinflavone (7) (a prenylated pyranoflavanone), shinpterocarpin (9) and 1-methoxyphaseollin (12) (both pyranopterocarpans), were isolated together with eight known saponins, seven known flavonoid glycosides, and eleven flavonoids. The structures of the new compounds have been elucidated on the basis of their chemical and physicochemical properties.

Presynaptic muscarinic receptors modulate acetylcholine release from rat antral mucosal/submucosal nerves

The purpose of the present studies was to determine whether autoinhibition of acetylcholine release could be demonstrated in vitro from mucosal/submucosal neurons in rat antrum. Rat antral mucosal/submucosal tissues preloaded with [3H]choline were perifused and [3H]acetylcholine release measured under basal and stimulated conditions. Carbachol inhibited both spontaneous and evoked (electrical field stimulation, KCl) acetylcholine release from rat antral tissues: 1 x 10(-5) M carbachol inhibited basal [3H]ACh release maximally to -38.2 +/- 3.1% (P < 0.001 vs control). The nonselective muscarinic antagonist atropine enhanced both basal and stimulated acetylcholine release and abolished carbachol-induced inhibition of acetylcholine release. Pirenzepine, a muscarinic M1 receptor antagonist, inhibited acetylcholine release and did not alter carbachol-induced inhibition of acetylcholine release. In conclusion, acetylcholine release from rat antral mucosal/submucosal neurons is regulated negatively by a presynaptic feedback mechanism involving M2 and/or M3 receptors, while presynaptic M1 receptors facilitate release of neurotransmitter.

Evidence that prostaglandin E2 can block calcium-activated 86Rb efflux from rat brain synaptosomes via a protein kinase C-dependent mechanism

The effects of prostaglandin E2 (PGE2) on 86Rb efflux from rat brain synaptosomes were studied to explore its role in nerve ending potassium (K+) channel modulation. A selective dose-dependent inhibition of the calcium-activated charybdotoxin-sensitive component of efflux was found upon application of PGE2. No significant effect was seen on basal and voltage-dependent components over the concentration range of 10(-8) to 10(-5) M. The protein kinase C (PKC) inhibitors H-7 (10 microM) and staurosporine (100 nM), as well as prolonged preincubation (90 min) with 4 beta-phorbol 12,13-dibutyrate, which has been reported to down-regulate PKC, abolished the PGE2-induced inhibition, whereas HA1004 (10 microM) and Rp-3',5'-cyclic phosphorothioate (100 nM), which are relatively more selective for protein kinase A than PKC, did not. 4 beta-Phorbol 12,13-dibutyrate (100 nM), an activator of PKC, produced a similar inhibition of the Ca(2+)-dependent component of 86Rb efflux but also had no effect on the basal and voltage-dependent components. These data suggest that PGE2 can inhibit rat brain nerve ending calcium-activated 86Rb efflux, and this inhibition may involve PKC activation.

Inhibition of a K+ current by beta-dendrotoxin in primary and subcultured vascular smooth muscle cells

beta-Dendrotoxin (beta-DTX), a polypeptide component of Eastern Green Mamba snake venom, inhibits a slow voltage-activated 86Rb efflux from synaptosomes, suggesting that beta-DTX inhibits K+ channels. The effects of beta-DTX on the K+ currents in primary cultured and subcultured (passages 8-12) rat tail artery vascular smooth muscle cells (VSMCs) were studied using the whole-cell patch-clamp technique. A delayed rectifier K+ current was observed in both types of cells. The current, which was relatively insensitive to tetraethylammonium, was activated at -40 to -30 mV and showed almost no inactivation. beta-DTX (1-1000 nM) decreased the outward K+ current. The effect was concentration dependent and reversible by washout but did not depend on the frequency of stimulation (use dependence) or the membrane potential. beta-DTX was more effective in primary cultured cells than in subcultured cells. K+ channels in primary cultured cells were maximally (45%) inhibited by 1 microM beta-DTX compared with 35% inhibition in subcultured cells. The concentration producing half-maximal inhibition was 5.1 x 10(-8) M for primary cells and 7.1 x 10(-8) M for subcultured cells. The delayed rectifier current was not affected by alpha-DTX, a blocker of the fast-inactivating outward K+ current (IA). These results clearly demonstrate that beta-DTX is a novel antagonist of the delayed rectifier K+ current in primary and subcultured rat tail artery VSMCs.

The N-glycosidase mechanism of ribosome-inactivating proteins implied by crystal structures of alpha-momorcharin

BACKGROUND

alpha-Momorcharin (alpha MMC) is a type I ribosome-inactivating protein. It inhibits protein synthesis by hydrolytically removing a specific adenine residue from a highly conserved, single-stranded loop of rRNA.

RESULTS

Here we describe the determination and refinement of the crystal structures of alpha MMC in the native state and in complexes with the product, adenine, and a substrate analogue, formycin 5'-monophosphate (FMP) at high resolution. Both adenine and the base of FMP are tightly bound; the ribose of bound FMP adopts a strained, high-energy conformation, which may mimic the structure of the transition state.

CONCLUSIONS

These structures indicate that residues Tyr70, Glu160 and Arg163 of alpha MMC are the most critical for catalysis. We propose that the strained conformation of the ribose in the target adenosine weakens the glycoside bond. Partial protonation mediated by Arg163 then facilitates N-glycoside bond cleavage, leading to the formation of an oxycarbonium ion intermediate which is stabilized by the negatively-charged Glu160. Tyr70 adopts subtly different conformations in the three structures implying that it may be important in substrate recognition and perhaps catalysis.

Identification and characterization of the esophagoglottal closure reflex in a feline model

To identify a suitable animal model and to delineate the neural pathway and target organs of the esophagoglottal closure reflex we studied three species. Study showed the existence of an esophagoglottal closure reflex in cats. The presence of this reflex could not be documented in the opossum. In monkeys, because of the inadequacy of the available recording devices, its presence could not be ascertained. In the feline model, the closure response of the vocal folds to the abrupt generalized and segmental distension of the esophagus was similar to that of the humans. Study findings indicate that among glottal adductor muscles at least interarytenoid and lateral cricoarytenoid muscles are involved as target organs of the esophagoglottal closure reflex. Decerebration did not change the frequency of glottal closure response to esophageal distension, supporting the notion that this reflex is completely under brain stem control. Bilateral cervical vagotomy abolished the glottal closure induced by esophageal distension indicating that this reflex is mediated by the vagus nerve. Upper esophageal sphincter (UES) pressure response to esophageal distension by air was variable, suggesting that glottal and UES response to esophageal distension, although closely coordinated, are not dependent on one another. In summary, an esophagoglottal closure reflex exists in feline species, and many similarities in the elicitation and mediation of this reflex have been found with that of humans. This model could be used for further physiological studies.

Alpha-lactalbumin possesses a distinct zinc binding site

It has been proposed that the binding of Zn2+ to alpha-lactalbumin switches the conformation to one akin to a state intermediate in the folding of the protein. However, the high resolution x-ray crystal structure of human alpha-lactalbumin-Zn2+ complex at 1.7-A resolution (pH 7.6) does not reveal any significant change in conformation from the native state. The Zn2+ ion binds specifically in the "cleft" of alpha-lactalbumin (the region which forms the active site of the homologous protein lysozyme). This may suggest a possible role for Zn2+ binding in lactose synthase complex. The coordination of the Zn2+ ion involves a symmetry-related molecule in the crystal, the crystal contacts being stabilized by a SO4(2-) ion bound at the interface between three molecules.

Saponin and sapogenol. L. On the constituents of the roots of Glycyrrhiza uralensis Fischer from Xinjiang, China. Chemical structures of licorice-saponin L3 and isoliquiritin apioside

From the air-dried roots of Glycyrrhiza uralensis Fischer collected in Xinjiang province, China ("Shinkyo-Kanzo" in Japanese), a new oleanene-type triterpene oligoglycoside named licorice-saponin L3 and a new chalcone oligoglycoside named isoliquiritin apioside were isolated together with glycyrrhizin, 18 alpha-glycyrrhizin, apioglycyrrhizin, araboglycyrrhizin, licorice-saponins A3, E2, G2, and H2, and six known flavonoid glycosides. On the basis of chemical and physicochemical evidence, the structures of licorice-saponin L3 and isoliquiritin apioside were elucidated as 3 beta-[alpha-L-rhamnopyranosyl(1-->2)-alpha-L-arabinopyranosyl(1--> 2)-beta-D-glucuronopyranosyloxy]-22 beta-acetoxy-24-hydroxyolean-12-en-30-oic acid (1) and 4-O-[beta-D-apiofuranosyl(1-->2)-beta-D- glucopyranosyl]isoliquiritigenin (6), respectively.

Saponin and sapogenol. XLIX. On the constituents of the roots of Glycyrrhiza inflata Batalin from Xinjiang, China. Characterization of two sweet oleanane-type triterpene oligoglycosides, apioglycyrrhizin and araboglycyrrhizin

Two sweet oleanane-type triterpene oligoglycosides named apioglycyrrhizin and araboglycyrrhizin were isolated from the air-dried roots of Glycyrrhiza inflata Batalin, collected in Xinjiang province (Shinkyo-Kanzo in Japanese), together with glycyrrhizin (3), licorice-saponins A3 (8), G2 (10), and H2 (11) and known flavonoid glycosides. On the basis of chemical and physicochemical evidence, the structures of apioglycyrrhizin and araboglycyrrhizin have been determined to be expressed as 3-O-[beta-D-apiofuranosyl(1-->2)-beta-D- glucuronopyranosyl]glycyrrhetic acid (1) and 3-O-[alpha-L- arabinopyranosyl(1-->2)-beta-D-glucuronopyranosyl]glycyrrhet ic acid (2), respectively. During the course of these studies, it has been found that the hydroxyl groups in the oligosaccharide moiety of the glucuronide saponins may be partially methylated by prolonged treatment with diazomethane in methanol. The sweetness of the saponins hitherto isolated from various Glycyrrhizae Radix has been examined and a structure-sweetness relationship, as compared with glycyrrhizin, has been found.

Effect of age and bolus variables on the coordination of the glottis and upper esophageal sphincter during swallowing

We studied 1) the effect of age and bolus variables on a) the coordination of deglutitive vocal cord adduction and upper esophageal sphincter (UES) relaxation and b) the duration of deglutitive vocal cord adduction; 2) the effect of the presence of a manometric catheter across the UES on the deglutitive glottal function; and 3) the temporal relationship between deglutitive vocal cord closure and swallow-induced apnea. We studied 10 young (23 +/- 2 yr) and 10 healthy elderly (73 +/- 2 yr) volunteers by concurrent videoendoscopy, UES manometry, respirography, and submental surface electromyography. In both groups the onset of vocal cord adduction preceded the onset of UES relaxation, deglutitive apnea, and submental electromyogram swallowing signal. In both groups, bolus volume and temperature did not have any significant effect on the duration of deglutitive vocal cord adduction. In both young and elderly volunteers, water swallows, compared with dry swallows, significantly shortened the interval between the onset of deglutitive vocal cord adduction and the onset of UES relaxation. In conclusion, coordination between deglutitive glottal and UES function, as well as the duration of deglutitive vocal cord adduction, is preserved in the elderly. Bolus volume and temperature do not have a modulatory effect on the duration of vocal cord closure, but water swallow shortens the interval between the onset of glottal closure and UES relaxation. This shortened interval may contribute to the safety of the airway during swallowing of liquid volumes.

Retinal detachment and degeneration in response to subretinal perfluorodecalin in rabbit eyes

Perfluorocarbon liquids, including perfluorodecalin (PFD), are useful intraoperative tools in complicated vitreoretinal surgery, such as for giant retinal tears, PVR and intraocular foreign bodies. Due to its high specific gravity (1.91 g/cm3) subretinal complications of PFD may occur. The consequences of subretinal PFD were studied in 23 albino rabbits (28 eyes). Using glass micropipettes (outer diameter of tip 100-120 microns), we injected 50-100 microliters PFD subretinally via the vitreous space. The same volume of BSS was injected into 18 control eyes. Eyes were monitored by indirect ophthalmoscopy and examined by light and electron microscopy at 1, 2 and 3 days, and 1, 2, 4 and 12 weeks. Progressive retinal detachments with newly formed retinal breaks in the inferior quadrants developed in 26 of 28 eyes. As early as 1 day postoperatively, subretinal PFD induced loss of outer and inner segments. Local retinal necrosis occurred in 4 eyes 5-7 days after surgery. A marked vacuole formation in retinal layers and PFD emulsification were regularly seen. The control eyes healed spontaneously. Toxic, mechanical and barrier effects may have caused the retinal damage. We advocate that all PFD be removed from the eye at surgery.

Effect of aging and bolus variables on pharyngeal and upper esophageal sphincter motor function

Effect of aging, bolus volume, temperature, and consistency on the pharyngeal peristalsis, as well as the effect of aging on the upper esophageal sphincter (UES) resting pressure and its response to esophageal distension by air and balloon, were studied in 14 young and 12 healthy elderly volunteers. In both age groups there was no significant volume or temperature effect on amplitude, duration, or velocity of the pharyngeal peristalsis. Compared with water swallows, mashed potato swallows resulted in a significant increase in the amplitude and duration of the hypopharyngeal peristaltic pressure wave (P < 0.05). For water swallows, the amplitude and duration of the peristaltic pressure wave in the hypopharynx were significantly increased in the elderly compared with the young group (P < 0.01). UES resting pressure in the elderly measured 43 +/- 5 (SE) mmHg and was significantly less than that of the young (71 +/- 8 mmHg; P < 0.01). Magnitude of the UES pressure decrease because of esophageal distension by air, as well as magnitude of its pressure increase because of esophageal balloon distension, was similar among young and elderly. 1) Contrary to common expectations, the parameters of the pharyngeal peristaltic pressure wave do not deteriorate in the elderly in their seventh and eighth decade. 2) Compared with the young, hypopharyngeal pressure wave amplitude and duration are significantly increased in the elderly. This increase could be caused by an adaptation response to a pharyngeal outflow compromise. 3) Pharyngeal peristaltic pressure wave amplitude and duration, but not its velocity, are modulated by the bolus consistency. This modulatory mechanism is preserved in the elderly. 4) Although UES resting pressure is significantly decreased in the elderly, its pressure response to esophageal distension by air and balloon is preserved.

Determinants of intrabolus pressure during esophageal peristaltic bolus transport

Previous manometric studies of esophageal fluid bolus transport in humans have generally ignored the hydrodynamic distinction between intrabolus pressure and pressure within the lumen-occluded, contracting esophageal segment. In this study we obtained concurrent esophageal videofluoroscopic and intraluminal manometric recordings in supine normal volunteers using different bolus volumes and viscosities and abdominal compression. Intrabolus pressure increased with bolus volume, viscosity, and abdominal compression. Esophageal diameter increased with larger bolus volumes, and this increase was correlated with increases in intrabolus pressure. Intrabolus pressure was highest in the bolus tail. Peak intraluminal pressures > 20 mmHg above basal intrabolus pressure almost invariably were associated with effective peristalsis, whereas values of this pressure differential < 20 mmHg frequently were associated with ineffective peristalsis and retrograde bolus escape. Intrabolus pressure can serve as an important indicator of the forces resisting peristaltic transport and the occurrence of ineffective bolus transport.

Calcitonin gene-related peptide mediates capsaicin-induced neuroendocrine responses in rat antrum

BACKGROUND

Calcitonin gene-related peptide (CGRP) is a 37-amino acid peptide localized to primary sensory afferent nerves in the rat stomach. The actions of CGRP in regulating antral neuroendocrine function were examined in vitro through the use of capsaicin, an agent capable of evoking neuropeptide release from peripheral sensory nerve endings. These results were compared with the effects of exogenous CGRP and CGRP antagonist, CGRP8-37.

METHODS

Rat antral mucosal/submucosal fragments were incubated in either static or dynamic perifusion experiments. Media were assayed for gastrin, somatostatin, CGRP, and acetylcholine.

RESULTS

Capsaicin, like exogenous CGRP, stimulated antral somatostatin release and inhibited both gastrin release and acetylcholine discharge. Low dose capsaicin (1 x 10(-5) mol/L) caused significant stimulation of CGRP release: 33 +/- 0.2 vs. 14 +/- 1 pg/mL protein; P < 0.001. Tetrodotoxin blocked capsaicin-induced inhibition of acetylcholine release and prevented partially capsaicin-mediated stimulation of CGRP release. The CGRP receptor antagonist CGRP8-37 prevented capsaicin-induced D-cell stimulation and inhibition of G-cell secretion and cholinergic discharge.

CONCLUSIONS

The effects of capsaicin-induced changes in antral D- and G-cell secretion and acetylcholine discharge are due primarily to release of CGRP. Antral CGRP release from primary sensory afferent nerve terminals may act as a local effector substance to regulate antral neuroendocrine function.

[Enhanced malignancy of tumor cells by the interaction with host cells reactive to foreign body]

We examined factors promoting malignant progression using a weakly malignant variant cell line, ER-1, derived from c-SST-2, a rat mammary carcinoma. ER-1 cells were converted to a highly malignant phenotype (highly tumorigenic, metastatic, invasive in vitro) by the in vitro/in vivo interaction with host cells reactive to foreign body. Epidermal growth factor (EGF) and transforming growth factor-beta (TGF-beta) produced by host reactive cells, transiently enhanced the tumorigenicity and in vitro invasiveness of ER-1 cells into an endothelial cell monolayer. The host reactive cells also produced oxygen radicals and induced mutations in ER-1 cells. It is speculated that mutations induced by host reactive cells cause cellular diversification, including the emergence of highly malignant variant cells whose growth is selectively promoted by growth factors such as EGF and TGF-beta.

Effects of some tricyclic psychopharmacons and structurally related compounds on motility of Proteus vulgaris

A simple test for the evaluation of drugs interfering with bacterial motility was established with Proteus vulgaris. With this model, promethazine, 7-hydroxy-chlorpromazine, imipramine, 7,8-dioxochlorpromazine and acridine orange were shown to exert significant motility and swarming inhibitory action on Proteus vulgaris strains at subinhibitory concentrations. Quinidine enhanced the antimotility effect of promethazine. The antimotility effect of promethazine was synergized by proton pump inhibitors omeprazole and abscissic acid, but antagonized by extracellular potassium and sodium ions.

Coordination of deglutition and phases of respiration: effect of aging, tachypnea, bolus volume, and chronic obstructive pulmonary disease

The effects of aging, tachypnea, bolus volume, and chronic obstructive pulmonary disease on the coordination of swallowing with the phases of respiration were studied by concurrent respirography and submental surface electromyography. Study findings showed that in young healthy volunteers, during rest, there is preferential coupling of subconscious swallowing with the expiratory phase of continuous respiration. This preferential coupling of swallowing with expiration was found to increase relative to other phases of respiration during water swallows and tachypnea (P < 0.05). Respiratory phase occurrence of swallowing and postdeglutitive resumption of respiration during exacerbation of chronic obstructive pulmonary disease was found to be significantly different compared with the basal state (P < 0.05). Respiratory phase occurrence of subconscious swallowing in the elderly was found to be different from the young (P < 0.05). Position had no significant effect on the coordination of swallowing and phases of respiration. We concluded that in resting young volunteers the majority of deglutitions are coupled with the expiratory phase of swallowing. This coupling is increased in frequency by the presence of a liquid bolus and tachypnea. And finally, age and chronic obstructive pulmonary disease alter this coordination significantly.

Malignant progression of a mouse fibrosarcoma by host cells reactive to a foreign body (gelatin sponge)

The QR regressor tumour (QR-32), a fibrosarcoma which is unable to grow progressively in normal syngeneic C57BL/6 mice, was able to grow progressively in 13 out of 22 mice (59%) when it was subcutaneously coimplanted with gelatin sponge. We established four culture tumour lines from the resultant tumours (QRsP tumour lines). These QRsP tumour lines were able to grow progressively in mice even in the absence of gelatin sponge. The ability of QRsP tumour cells to colonise the lungs after intravenous injection and to produce high amounts of prostaglandin E2 (PGE2) during in vitro cell culture was much greater than that of parent QR-32 cells. These biological characteristics of QR-32 cells and QRsP tumour cells were found to be stable for at least 6 months when they were maintained in culture. We also observed that QR-32 cells were able to grow progressively in five out of 12 (42%) mice after coimplantation with plastic non-adherent peritoneal cells obtained from mice which had been intraperitoneally implanted with gelatin sponge. These host cells reactive to gelatin sponge increased the production of high amounts of PGE2 by QR-32 cells during 48 h coculture. Preliminary in vitro studies implicated the involvement of hydrogen peroxide and hydroxyl radical as some of the factors necessary to induce QR-32 cells to produce high amounts of PGE2 and to accelerate tumour progression.