Exendin-4, glucagon-like peptide-1 receptor agonist, enhances isoflurane-induced preconditioning against myocardial infarction via caveolin-3 expression.

OBJECTIVE: To investigate the cardioprotective effects of isoflurane and exendin-4 against myocardial ischemia/reperfusion injury and the signaling pathways through which these effects are mediated. MATERIALS AND METHODS: For infarct size measurements, anesthetized mice were subjected to 30 min of coronary artery occlusion followed by 2 h of reperfusion. Wild-type or caveolin-3 knockout mice received isoflurane, exendin-4, or isoflurane with exendin-4 before ischemia index determination. Caveolin-3 expression in the heart was measured by immunoblotting. RESULTS: Myocardial infarct size was smaller in the isoflurane- [1.0 minimum alveolar concentration (MAC)] or exendin-4- (30 ng/kg i.v.) treated groups than the controls. Infarct size was not affected by isoflurane at 0.5 MAC or 3 ng/kg i.v. exendin-4, but the combination of these treatments reduced infarct size. Pharmacological preconditioning (isoflurane at 1.0 MAC, 30 ng/kg i.v. exendin-4, or isoflurane at 0.5 MAC with 3 ng/kg i.v. exendin-4) increased caveolin-3 protein expression in the heart after infarct induction. The cardioprotective effects of isoflurane, exendin-4, and isoflurane with exendin-4 were abolished in caveolin-3 knockout mice. CONCLUSIONS: The combination of isoflurane and exendin-4 reduced infarct size, but it was not more effective than either agent alone, and the cardioprotective effects of these agents are mediated by caveolin-3 expression.

Expression of cell adhesion molecules at the collapse and recovery of haematopoiesis in bone marrow of mouse.

After bone marrow transplantation (BMT) and lethal irradiation, vascular endothelial cells play an important role in the homing of haematopoietic cells and recovery of haematopoiesis. We investigated the expression of mucosal addressin cell adhesion molecule-1 (MAdCAM-1), vascular cell adhesion molecule-1 (VCAM-1) and fibronectin in the endothelial cells of bone marrow in a collapsed state after lethal irradiation and in a recovery state after BMT in mice. After lethal irradiation, the expression of MAdCAM-1, VCAM-1 and fibronectin increased on the luminal surface of endothelial cells. In the recovery state, the expression of MAdCAM-1 and VCAM-1 was increased from 2 to 4 days after BMT, but fibronectin levels remained constant, except for a temporary increase at 4 days after BMT. The number of homing cells, however, was markedly decreased in parallel with the reduction in the haematopoietic compartment at 2 and 4 days after lethal irradiation. Next, to analyse the influence of fibronectin expression after BMT on homing activity, we performed double BMT experiment. The number of homing cells in double BMT experiment maintained high level from 2 h to 2 days after secondary BMT. Our data suggest that homing of bone marrow cells is activated until fibronectin-mediated endothelial cell repair and that transplanted haematopoietic stem/progenitor cells inhibit fibronectin expression for endothelial cell repair until the homing is completed. Therefore, the homing of haematopoietic cells in bone marrow depends on the condition of the bone marrow endothelial cells, as well as the cell adhesion molecules.

Distribution of lectin-bindings in the testis of the lesser mouse deer, Tragulus javanicus.

The distribution of lectin bindings in the testis of the smallest ruminant, lesser mouse deer (Tragulus javanicus), was studied using 12 biotinylated lectins specific for d-galactose (peanut agglutinin PNA, Ricinus communis agglutinin RCA I), N-acetyl-d-galactosamine (Dolichos biflorus agglutinin DBA, Vicia villosa agglutinin VVA, Soybean agglutinin SBA), N-acetyl-D-glucosamine and sialic acid (wheat germ agglutinin WGA, s-WGA), D-mannose and d-glucose (Lens culinaris agglutinin LCA, Pisum sativum agglutinin PSA, Concanavalin A Con A), L-fucose (Ulex europaeus agglutinin UEA I), and oligosaccharide (Phaseolus vulgaris agglutinin PHA-E) sugar residues. In Golgi-, cap-, and acrosome-phase spermatids, lectin-bindings were found in the acrosome (PNA, RCA I, VVA, SBA, WGA and s-WGA), and in the cytoplasm (PNA, RCA I, VVA, SBA, WGA, LCA, PSA, Con A and PHA-E). s-WGA binding was confined to the spermatid acrosome, but other lectins were also observed in spermatocytes. In spermatogonia, VVA, WGA, Con A, and PHA-E bindings were observed. Sertoli cells were intensely stained with DBA and Con A, and weakly with PHA-E. In interstitial Leydig cells, RCA I, DBA, VVA, Con A, PSA, LCA, WGA and PHA-E were positive. UEA I was negative in all cell types including spermatogenic cells. Unusual distribution of lectin-bindings noted in the testis of lesser mouse deer included the limited distribution of s-WGA only in the spermatid acrosome, the distribution of DBA in Sertoli cells, Leydig cells and lamina propria, and the absence of UEA I in all type cells. The present results were discussed in comparison with those of other animals and their possible functional implications.

Breed differentiation among Japanese native chickens by specific skull features determined by direct measurements and computer vision techniques.

1. Inter-breed morphological comparisons were made among 11 breeds of Japanese native chickens (Gifujidori, Hinaidori, Shokoku, Totenko, Tomaru, Satsumadori, Shamo, Koshamo, Koeyoshi, Chabo and Nagoya), White Leghorn, broiler chickens (Chunky) and red junglefowl collected in the Philippines, based on results of direct measurements and analysis by computer vision techniques of the skull. 2. Analysis of direct measurements identified two groups of chicken: a small type that included the Chabo, Koshamo, red junglefowl, Gifujidori and Shokoku and a large type that included the remaining breeds studied. These groupings were made based on size determined both in the first (PC1) and second principal component (PC2). The greatest length of the cranium and condylobasal length greatly contributed to the morphological differences between these two groups. 3. Analysis by computer vision techniques, however, identified three groups: the Bantam group (which includes red junglefowl), Shokoku group and Shamo group. White Leghorn clustered within the Shokoku group while the broiler chicken belonged to the Shamo group. The region around the junction of the neural cranium and the visceral cranium contributed greatly to the morphological differences among breeds, both in the PC1 and PC2.

Novel erythrocyte pits in the small tropical ruminant, lesser mouse deer.

We examined unique erythrocyte pits of the peripheral blood and bone marrow in the lesser mouse deer, Tragulus javanicus, using scanning electron microscope (SEM) and transmission electron microscope (TEM). Under the SEM observation, the pit was observed as a hole on both mature erythrocytes of the peripheral blood and immature erythrocytes of the bone marrow. By the TEM, the mature erythrocytes had a vacuole, which showed complicated shape and occupied considerable space within the cytoplasm. The vacuole was communicated extracellularly by perforation, which corresponded to the hole on the cell surface. In the bone marrow, erythroblast and reticulocytes have a cytoplasmic vacuole. This abnormal feature of the erythrocytes is peculiar to the mouse deer, and not found in other tropical ruminants. Despite the disadvantage of volume loss from the small erythrocytes, the mouse deer were healthy and showed no signs of anaemia.

A light and electron microscopical study of the Tragulid (mouse deer) placenta.

The Tragulidae are the living relics of the basal ruminant stock. They have a diffuse placenta, with no aggregations of the placental villi into localised placentomes characteristic of all other ruminants. Despite this difference, this ultrastructural and immunocytochemical investigation demonstrates that in Tragulus the trophoblast binucleate cell (BNC) plays the same central role in development and structure as in all other ruminants. It shows an identical development and ultrastructure, produces granules reactive with bovine placental lactogen and pregnancy associated glycoprotein antibodies, and migrates when mature through the trophoblast tight junction to fuse into a mosaic of syncytial plaques from which the granules are released to the mother and which have replaced the uterine epithelium. Unlike the persistent plaques in the sheep and goat placenta, in Tragulus they are transient, dying by apoptosis with the fragments phagocytosed by the trophoblast. This brings the trophoblast into direct endotheliochorial apposition to maternal tissue until BNC migration and fusion replace the dead plaque. This intimate fetomaternal confrontation has not been shown in any other ruminant, and could be a relic of the evolutionary development of the synepitheliochorial from the original basic eutherian endo- or hemo-chorial placenta.

Immunolocalization of gastrin-releasing peptide (GRP) in the uteroplacenta of the mouse deer.

The considerable phylogenetical differences between mouse deer and other ruminants have been established by means of DNA sequence analysis and anatomical observations. To clarify the physiological role of the uteroplacenta of the mouse deer, immunohistochemical observation was attempted by using GRP, which has been suggested as a novel regulatory peptide in the female reproductive tract, as an indicator to compare with other ruminants. Strong positive reactions for the GRP were detected in the uterine glands of the pregnant animals, but not in the non-pregnant ones. Although the placenta of the mouse deer is categorized as a diffuse placenta that is different from other ruminants' polycotyledonary placenta, in terms of GRP immunoreactivity, the mouse deer placenta can be classified as a synepithecholial placenta like the other ruminants'. The secretion of GRP from the uterine glands is of some importance to the fetus in the mouse deer.

Morphological study of the transition of haematopoietic sites in the developing mouse during the peri-natal period.

The transition of fetal haematopoietic sites in mice was examined histologically from 12.5-day embryos (E12.5) until 10 days of age (D10), and the expression of the adhesive molecules VCAM-1 and fibronectin was examined immunohistologically. Erythropoiesis occurred in the liver (E12.5-18.5), spleen (E18.5-D4) and bone marrow (D6-10), in that sequence. Even at D10, some erythropoiesis occurred in the liver, and more so in the spleen, although the active haematopoietic site was the bone marrow. Similarly, granulopoiesis of neutrophils occurred in the liver, spleen and bone marrow in turn. Granulopoiesis still occurred in the spleen at D10, but no neutrophils were found in the liver after D4. VCAM-1 appeared in the liver, spleen and bone marrow in parallel with active erythropoiesis and granulopoiesis. The co-expression of VCAM-1 and fibronectin was recognized in the endothelial cells of the sinus at the onset of haematopoiesis. This study showed that haematopoiesis in the liver, spleen and bone marrow overlapped peri-natally, although it shifted sequentially. VCAM-1 appears to be closely associated with erythropoiesis and granulopoiesis, and the co-expression of VCAM-1 and fibronectin plays a role in inducing haematopoietic stem cells to move to the tissues.

An ultrastructural study on the Leydig and Sertoli cells in the immature lesser mouse deer (Tragulus javanicus).

Leydig and Sertoli cells of the immature lesser mouse deer testes, obtained in East Malaysia, were observed using light and transmission electron microscopy (TEM). The testes were fixed in 5% glutaraldehyde, post-fixed in 1% OsO4, dehydrated in ethanol, and embedded in Araldite M. Serial semi-thin sections were cut, stained with toluidine blue and observed using light microscopy. Serial ultra-thin sections were cut, stained with uranyl acetate and lead citrate, and examined using TEM. As a result, ultrastructurally, two types of underdeveloped filament bundles were infrequently recognized in Leydig cells, but not in other testicular cells. One type was the underdeveloped bundles of actin filaments (approximately 5 nm in diameter), which were found in the nucleus of Leydig cells. The other type was the underdeveloped bundles of intermediate filaments (approximately 10 nm in diameter), which were found in the cytoplasm of Leydig cells. A multivesicular nuclear body (MNB)--specifically present in the Sertoli cell nucleus of ruminant testes--was infrequently observed. The MNB is situated in the vicinity of nuclear membrane, still in an underdeveloped stage.

Anatomical and histological characterization of the female reproductive organs of mouse deer (Tragulidae).

The Tragulidae may be a type that represents the earliest ruminant families to evolve. The female reproductive organs including ovary, oviduct, uterus and placenta were anatomically and histologically investigated. The structures of the ovary and oviduct were very similar to other ruminants. However, the gross structure of the placenta was diffuse and thus noticeably different from other ruminants which are polycotyledonary. Histologically, the placenta of Tragulidae appears to be epitheliochorial and therefore similar to other ruminants. Numerous trophoblastic binucleated cells which are characteristic of all other ruminants were observed. These results suggest that the placenta of Tragulidae is a transitional type between diffuse epitheliochorial and polycotyledonary synepitheliochorial categories.

Afferent and efferent connections of the nucleus geniculatus lateralis ventralis demonstrated by WGA-HRP in the chick.

Fibre connections of the chick nucleus geniculatus lateralis ventralis (GLv) were investigated using the axonal tracing method with wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). After an injection of WGA-HRP into the GLv, many labelled neurons were observed in layer i of the stratum griseum et fibrosum superficiale (SGFS) in the ipsilateral tectum opticum (TO) and in the nucleus lentiformis mesencephali (LM). In the TO-GLv projection, cells of origin were located in the deeper part of layer i of the TO and were topographically distributed along the direction from the rostrodorsal part to the caudoventral part of the TO relating to a rostrocaudal axis of the GLv. In the LM-GLv connection, the dorsal and ventral parts of the LM connected reciprocally with the rostral and caudal halves of the GLv, respectively. In contrast, in the GLv efferent connection, labelled axon terminals spread widely in the ipsilateral area pretectalis without any clear topographical arrangement.

Afferent and efferent connections of the nucleus rotundus demonstrated by WGA-HRP in the chick.

Organization of the fibre connections in the chick nucleus rotundus (Rt) was investigated by an axonal tracing method using wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). After an injection of WGA-HRP into the Rt, labelled neurones were observed in the striatum griseum centrale (SGC) in both sides of the tectum (TO) and in the ipsilateral nucleus subpretectalis/nucleus interstito-pretecto-subpretectalis (SP/IPS). Labelled fibres and terminals were also found in the ipsilateral ectostriatum (Ect). These fibre connections were topographically organized rostrocaudally. In the TO-Rt projection, the rostral and the dorsocaudal parts of the Rt received afferents from the superficial part of the SGC, the middle part of the Rt received afferents from the intermediate part of the SGC, and the ventrocaudal part of the Rt received mainly fibres from the deep part of the SGC. These topographic projections were accompanied by a considerable number of diffuse projections to the thalamic regions surrounding the Rt. In addition, the rostral and middle caudal parts of the Rt received afferents from the lateral and medial parts of the SP/IPS, respectively, and respective parts of the Rt sent efferents to the lateral and medial parts of the Ect.

Peculiar bundles of filaments in Leydig cells of the lesser mouse deer (Tragulus javanicus): an ultrastructural study.

Leydig cells of lesser mouse deer (Tragulus javanicus) testes were observed using light and transmission electron microscopies. Sexually mature lesser mouse deer were obtained in East Malaysia. The testes were perfused with 5% glutaraldehyde, postfixed with 1% OsO4, dehydrated in ethanol and embedded in Araldite. The semithin sections were cut, stained with toluidine blue and observed under light microscopy. The ultrathin sections were cut, stained with uranyl acetate and lead citrate, and examined using a JEM-1200 transmission electron microscope. As a result, two types of filament bundles were frequently recognized in Leydig cells, but not in other testicular cells. These bundles were clearly seen at even a light microscopic level. One type was bundles of actin filaments (approximately 5 nm in diameter). These structures were found not only in the cytoplasm but also in the nucleus. The other type was bundles of intermediate filaments (approximately 10 nm in diameter). These structures were found only in the cytoplasm. The existence of filament bundles has never been reported in the testicular cells of another mammalian species. Thus, while bundles of actin and intermediate filaments are specifically present in the Leydig cells of the lesser mouse deer, their functions are still unclear.

Anatomical relationship between enkephalin-containing neurones and caecum-projecting neurones in the chicken intestinal nerve.

The anatomical relationship between enkephalin-immunoreactive neurones and caecum-projecting neurones in the intestinal nerve of Remak (INR) of the chicken was investigated using retrograde transport of cholera toxin subunit B and immunohistochemistry with anti-enkephalin serum. After injection of cholera toxin into the base or body of the caecum, labelled neurones were mainly observed in the cranial part of the rectal INR. Enkephalin-immunoreactive neuronal cell bodies were found in the caudal part of the rectal INR and their fibres closely surrounded caecum-projecting neurones in the cranial part of the rectal INR. Diameters of caecum-projecting neurones surrounded with enkephalin-containing terminals were significantly larger than those of caecum- projecting neurones without enkephalin-terminals (P < 0.01). From these results, it is suggested that enkephalin-containing neurones are able to affect large-sized caecum-projecting neurones. This pathway may be involved with unique motility of the rectum and caeca that uric acid is retrogradely carried from the cloaca to the caeca.

The widespread effect of beta 1,4-galactosyltransferase on N-glycan processing.

We investigated beta 1,4-GalT (UDP-galactose: beta-d-N-acetylglucosaminide beta 1,4-galactosyltransferase) in terms of intracellular competition with GnT-IV (UDP-N-acetylglucosamine: alpha1,3-d-mannoside beta1,4-N-acetylglucosaminyltransferase) and GnT-V (UDP-N-acetylglucosamine: alpha1,6-d-mannoside beta 1,6-N-acetylglucosaminyltransferase). The beta 1,4-GalT-I gene was introduced into Chinese hamster ovary (CHO) cells producing human interferon (hIFN)-gamma (IM4/V/IV cells) and five clones expressing various levels of beta 1,4-GalT were isolated. As we previously reported, parental IM4/V/IV cells express high levels of GnT-IVa and -V and produce hIFN-gamma having primarily tetraantennary sugar chains. The branching of sugar chains on hIFN-gamma was suppressed in the beta 1,4-GalT-enhanced clones to a level corresponding to the intracellular activity of beta 1,4-GalT relative to GnTs. Moreover, the contents of hybrid-type and high-mannose-type sugar chains increased in these clones. The results showed that beta 1,4-GalT widely affects N-glycan processing by competing with GnT-IV, GnT-V, and alpha-mannosidase II in cells and also by some other mechanisms that suppress the conversion of high-mannose-type sugar chains to the hybrid type.

Effect of Helicobacter pylori eradication on gastric mucosal phospholipid content and its fatty acid composition.

BACKGROUND AND AIMS: Whether Helicobacter pylori eradication alters gastric mucosal phospholipid contents and their fatty acid composition remains unclear. The aim of the present study was to clarify the effect of H. pylori eradication on gastric mucosal phosphatidylcholine (PC) content and its fatty acid composition. METHODS: Endoscopic biopsy specimens were taken from the antrum and body of each of 19 asymtomatic male volunteers for detection of H. pylori, histopathological assessment of gastritis, phospholipid determination and fatty acid analysis. All the subjects with H. pylori infection were treated with eradication therapy. Endoscopy and tissue sampling were repeated again 1 and 6 months after all treatment. RESULTS: In eight subjects, H. pylori infection was evident and was successfully eradicated. Pretreatment degrees of lymphocytes and plasma cells (inflammation) and polymorphonuclear neutrophils (activity) were greater in H. pylori-positive subjects compared with H. pylori-negative subjects (P<0.001), whereas the degree of inflammation decreased (P<0.001), and neutrophils had completely disappeared at 6 months after eradication. Moreover, the gastric mucosal PC contents at the antrum and body were unchanged within 1 month after cessation of treatment, but increased at 6 months after eradication (P<0.05). At 6 months after cessation of treatment, H. pylori-eradicated subjects had an increase (+30% at antrum, +18% at body) in linoleic acid composition and a decrease (-37%, -43%) in arachidonic acid composition of PC at the antrum and body, respectively. CONCLUSIONS: These findings suggest that H. pylori eradication reduces the production of various eicosanoids, resulting in the normalization of gastric mucosal PC content and its fatty acid composition, which may consequently cause the gastric mucosal hydrophobicity to be normalized.

Helicobacter pylori alters n-6 fatty acid metabolism and prostaglandin E2 synthesis in rat gastric mucosal cells.

BACKGROUND AND AIMS: Little is known about whether Helicobacter pylori infection alters fatty acid metabolism in gastric mucosal cells. By using cultured rat gastric mucosal cells (RGM-1), we investigated the effect of H. pylori broth culture filtrates on this point. Furthermore, our study aimed to find out whether n-6 long chain polyunsaturated fatty acids from linoleic acid are formed in RGM-1 cells. METHODS: Rat gastric mucosal cells were incubated with 10, 20 and 40 microg/mL of linoleic acid or medium alone. Phosphatidylcholine content extracted from whole RGM-1 cells was quantitated by using a densitometer, and its fatty acid composition was analyzed by using gas chromatography. Prostaglandin E2 concentration in the culture medium was measured by using radioimmunoassay. The expression of cyclooxygenase (COX)-1 and COX-2 was examined by using reverse transcription-polymerase chain reaction. In addition, after incubation with [1-14C] linoleic acid, radioactivities of both linoleic acid and arachidonic acid components of the PC fraction were counted. The effects of H. pylori broth culture filtrates on PC content, its fatty acid composition and prostaglandin (PG)E2 synthesis were also assessed. RESULTS: Linoleic acid addition caused an increase in the composition of arachidonic acid, as well as linoleic acid, and also in PGE2 concentration. Cyclo-oxygenase-2 expression was induced in RGM-1 cells by the addition of linoleic acid. In addition, [1-14C] linoleic acid added to the culture medium was converted to [1-14C] arachidonic acid in RGM-1 cells. Helicobacter pylori broth culture filtrates decreased linoleic acid composition and increased arachidonic acid composition. Moreover, after incubation with H. pylori broth culture filtrates, PGE2 concentrations were higher than that of the controls. CONCLUSIONS: These findings suggest the presence of fatty acid elongase and Delta5- and Delta6-desaturases synthesize arachidonic acid from linoleic acid in RGM-1 cells. Thus, H. pylori infection may enhance PGE2 synthesis and accelerate n-6 fatty acid metabolism in gastric mucosal cells, which could make the gastric mucosal barrier more fragile.

Surgical treatment of a massive chondrosarcoma in the skull base associated with Maffucci's syndrome: a case report.

BACKGROUND: A successfully treated massive chondrosarcoma in the skull base associated with Maffucci's syndrome is presented. The purpose of this report is to discuss the surgical approach to the tumor and reconstruction of the skull base. CASE DESCRIPTION: A 36-year-old woman who had a history of multiple enchondromas and subcutaneous hemangiomas presented with decreased right visual acuity and left papilledema. Computed tomography (CT) and magnetic resonance imaging (MRI) demonstrated a mass in the skull base. The tumor occupied the nasal and paranasal cavities, and extended to the anterior, middle, and posterior intracranial spaces. The midline skull base structures and the left middle cranial base were destroyed. Using a combined anterior craniofacial and left orbitozygomatic approach, the tumor was totally resected. The large skull base defect was reconstructed with a vascularized outer table parietal bone graft attached to a bipedicled temporoparietal galeal flap. The postoperative course was uneventful except for decreased left visual acuity, and temporary diplopia and facial hypesthesia. In 40 months of follow-up there was no recurrence. CONCLUSIONSA skull base approach should be selected to perform total resection of an extensive skull base tumor. The bipedicled temporoparietal galeal flap and vascularized calvarial bone was useful for simultaneous reconstruction.

Comparative study of the N-glycans of human monoclonal immunoglobulins M produced by hybridoma and parental cells.

Cell-cell hybridization is one method of establishing cell lines capable of producing an abundance of antibodies. In order to clearly characterize antibodies produced by hybridomas, the influence of cell-cell hybridization on the glycosylation of produced antibodies should be studied. In this report, we describe structural changes of the N-glycans in immunoglobulin M (IgM) produced by a hybridoma cell line termed 3-4, which was established through hybridization of an IgM-producing Epstein-Barr virus transformed human B-cell line termed No. 12, and a human myeloma cell line termed P109. We analyzed the structures of sugar chains on the constant region of the mu-chain of IgMs produced by parental No. 12 cells and hybridoma 3-4 cells. In both parental cells and hybridoma cells, the predominant structures at Asn171, Asn332, and N395 were fully galactosylated biantennary complex types, with or without core fucose and/or bisecting GlcNAc. However, the amount of bisecting GlcNAc was markedly decreased in the hybridoma cells. Therefore, the activity of UDP-N-acetylglucosamine:beta-D-mannoside beta-1,4-N-acetylglucosaminyltransferase (GnT-III) responsible for the formation of bisecting GlcNAc was measured in parental cells and hybridoma cells. No. 12 cells showed some GnT-III activity, whereas P109 cells showed no such activity. The corresponding level of activity observed in hybridoma 3-4 cells was much lower than that in No. 12 cells. The above results demonstrated a reduction in the intracellular activity of GnT-III in the hybridoma cells, which was largely due to the influence of P109 cells. Moreover, the sugar chain structures of IgMs produced by the cells reflected the level of GnT-III activity.

Control of bisecting GlcNAc addition to N-linked sugar chains.

In the present study, experimental control of the formation of bisecting GlcNAc was investigated, and the competition between beta-1,4-GalT (UDP-galactose:N-acetylglucosamine beta-1, 4-galactosyltransferase) and GnT-III (UDP-N-acetylglucosamine:beta-d-mannoside beta-1, 4-N-acetylglucosaminyltransferase) was examined. We isolated a beta-1,4-GalT-I single knockout human B cell clone producing monoclonal IgM and several transfectant clones that overexpressed beta-1,4-GalT-I or GnT-III. In the beta-1,4-GalT-I-single knockout cells, the extent of bisecting GlcNAc addition to the sugar chains of IgM was increased, where beta-1,4-GalT activity was reduced to about half that in the parental cells, and GnT-III activity was unaltered. In the beta-1,4-GalT-I transfectants, the extent of bisecting GlcNAc addition was reduced although GnT-III activity was not altered significantly. In the GnT-III transfectants, the extent of bisecting GlcNAc addition increased along with the increase in levels of GnT-III activity. The extent of bisecting GlcNAc addition to the sugar chains of IgM was significantly correlated with the level of intracellular beta-1,4-GalT activity relative to that of GnT-III. These results were interpreted as indicating that beta-1, 4-GalT competes with GnT-III for substrate in the cells.