Elevated vascular endothelial growth factor levels in sera of patients with lung cancer

BACKGROUND

Vascular endothelial growth factor (VEGF) overexpression has been observed in several malignant tumors, and VEGF level in serum appears to be correlated with tumor burden in cancer patients.

PATIENTS AND METHODS

Serum VEGF levels were measured in 70 patients with lung cancer including 23 with adenocarcinoma, 19 with squamous cell carcinoma, 3 with large cell carcinoma, and 25 with small cell carcinoma, and in 30 patients with benign lung disease and 13 healthy subjects with an enzyme immunoassay.

RESULTS

VEGF levels (mean +/- SD; pg/ml) were 834 +/- 699 and 732 +/- 529 in patients with lung cancer and benign lung disease, respectively, and were significantly higher than those in healthy subjects (264 +/- 129) (P < 0.01). There were no differences between VEGF levels categorized by histology, disease stage, or distant metastasis for lung cancer patients.

CONCLUSIONS

Although serum VEGF levels were increased in lung cancer patients, this increase might not have been related to tumor burden.

[Characteristics of retinal detachment in eyes with choroidal colobomas]

We reviewed 6 eyes of 6 patients (1 male and 5 females) with retinal detachment associated with choroidal coloboma. Three of these 6 eyes had visible retinal breaks within or at the margin of the coloboma. In one eye, no retinal breaks were noted before or during vitreous surgery, and shallow retinal detachment was localized in the posterior fundus. One eye with bullous retinal detachment with retinal breaks within the coloboma had been having serous retinal detachment localized in the nasal area close to the optic nerve head. In all of these five eyes; vitrectomy, relaxing retinotomy inside the coloboma close to its edges, and cyanoacrylate retinopexy resulted in successful reattachment of the retina. Schisis-like separation similar to that in pit-macular syndrome was noted in the posterior retinal in one eye which had no visible retinal break. Non-rhegmatogenous retinal detachment may exist in association with choroidal colobomas.

Effects of histamine on mucin biosynthesis in rat gastric mucosa

Mucin biosynthesis is stimulated by gastrin during the process of glycosylation in the corpus mucosa of the rat stomach. The purpose of this study was to clarify, using an organ culture technique, whether biosynthetic responses to histamine in the rat gastric mucin are the same as that to gastrin. Radiolabeled mucin was obtained from the corpus and antral mucosa of the rat stomach after in vitro incubation for 5 h with [3H]glucosamine (GlcN), [14C]threonine (Thr), and [35S]sulfate. Addition of histamine (10(-7)-10(-5) M) to the culture medium increased [3H]GlcN-labeled mucin in the corpus tissue in a concentration-dependent manner. In the antrum, there was no significant change in the biosynthetic activity of mucin in response to histamine. Histamine at 10(-5) M also increased the incorporation of both [35S]sulfate and [14C]Thr into the corpus mucin. These results indicate that histamine stimulates the biosynthesis of the mucin peptide, as well as the glycosylation step in the corpus, and suggest that the effect of histamine on mucin synthesis is distinct from that of gastrin.

Isolation and characterization of a novel actin filament-binding protein from Saccharomyces cerevisiae

We purified a novel actin filament (F-actin)-binding protein from the soluble fraction of Saccharomyces cerevisiae by successive column chromatographies by use of the 125I-labeled F-actin blot overlay method. The purified protein showed a minimum Mr of about 140 kDa on SDS-polyacrylamide gel electrophoresis and we named it ABP140. A search with the partial amino acid sequences of ABP140 against the Saccharomyces Genome Database revealed that the open reading frame of the ABP140 gene (ABP140) corresponded to YOR239W fused with YOR240W by the +1 translational frame shift. The encoded protein consisted of 628 amino acids with a calculated Mr of 71,484. The recombinant protein interacted with F-actin and showed the activity to crosslink F-actin into a bundle. Indirect immunofluorescence study demonstrated that ABP140 was colocalized with both cortical actin patches and cytoplasmic actin cables in intact cells. However, elimination of ABP140 by gene disruption did not show a deleterious effect on cell growth or affect the organization of F-actin. These results indicate that ABP140 is not required for cell growth but may be involved in the reorganization of F-actin in the budding yeast.

Distinct effects of tetragastrin, histamine, and CCh on rat gastric mucin synthesis and contribution of NO

Although gastrin, histamine, and carbachol (CCh) accelerate gastric mucin metabolism, information about their target cells of mucin production is lacking. To clarify this, we examined the effects of these stimulants, including the possible participation of nitric oxide (NO), on mucin biosynthesis in distinct sites and layers of rat gastric mucosa. Pieces of tissue obtained from the corpus and antrum were incubated in a medium containing radioactive precursors and each stimulant, with or without NO synthase (NOS) inhibitor. Distribution of NOS was compared with that of the specific mucins by immunostaining using specific antiserum and monoclonal antibodies. In the full-thickness corpus mucosa, tetragastrin enhanced [3H]glucosamine incorporation into mucin but had no effect on [14C]threonine incorporation. Both histamine and CCh dose dependently increased3H- and14C-labeled corpus mucin. Only CCh stimulated antral mucin biosynthesis. CCh stimulation was noted in the corpus mucosa after removal of surface mucous cells, but stimulation by tetragastrin or histamine disappeared as a result of this pretreatment. Only tetragastrin-induced activation was completely blocked by the NOS inhibitor. NOS immunoreactivity was limited to surface mucous cells. Mucus-producing cells present in the different sites and layers of the gastric mucosa have distinct mechanisms for regulation of mucin biosynthesis. Gastrin-stimulated mucin biosynthesis mediated by NO is limited to surface mucous cells of rat gastric oxyntic mucosa.

Structural requirements for roxatidine in the stimulant effect of rat gastric mucin synthesis and the participation of nitric oxide in this mechanism

1. The structural requirements of the histamine H2-receptor antagonist, roxatidine (2-acetoxy-N-(3-[m-(1-piperidinylmethyl)phenoxy]-propyl)acetamide hydrochloride), for the stimulant effect on mucin biosynthesis and their relation to histamine H2-receptor antagonism were identified by considering the structural analogues of this drug using an organ culture system of the rat stomach and competition studies with [125I]iodoaminopotentidine ([125I]-APT) binding to membranes of the guinea pig striatum. 2. [3H]Glucosamine incorporation into mucin during 5 h incubation period was stimulated by roxatidine and its structural analogues A (2-hydroxy-N-(3-[m-(1-piperidinylmethyl)phenoxy]-propyl)acetamide) and B (N-(3-[m-(1-piperidinylmethyl)phenoxy]-propyl)acetamide). This effect was seen in mucosal cultures of the corpus, but not antrum, region. 3. Structural analogues, in which the length of the flexible chain between the benzene ring and the amide structure differs from that of roxatidine, failed to activate mucin synthesis. No significant change in mucus synthesis occurred with the addition of analogues in which the piperidine ring attached to the benzene ring via a methylene bridge was changed. 4. Specific [125I]-APT binding to the histamine H2 receptor of guinea pig brain membranes was inhibited by roxatidine and all structural analogues used in this study, except F (N-(3-[m-(N, N-dimethyl-aminomethyl)phenoxy]-propyl)acetamide). 5. Ranitidine at 10(-4) M did not suppress the roxatidine-induced increase in [3H]glucosamine incorporation into mucin. 6. Roxatidine-induced stimulation of [3H]glucosamine incorporation into mucin was completely blocked by the addition of either NG-nitro-L-arginine (10(-5) M) or 2-(4-carboxyphenyl)-4,4,5,5,-tetramethylimidazoline-1-oxyl-3-oxide sodium salt (10(-5) M). The inhibitory action of NG-nitro-L-arginine was totally reversed by L-arginine (5 x 10(-3) M). 7. These results suggest that the cardinal chemical features of roxatidine for the activation of mucin biosynthesis in the corpus region of the rat stomach are the appropriate length of the flexible chain between the amide structure and the aromatic ring system bearing the methylpiperidinyl group at the meta position. The activity of roxatidine and its analogues to stimulate mucin synthesis is not related to their histamine H2 receptor antagonistic activity. Roxatidine-induced activation of mucin biosynthesis in the corpus tissue is mediated by nitric oxide.

Identification of SH2-Bbeta as a substrate of the tyrosine kinase JAK2 involved in growth hormone signaling

Activation of the tyrosine kinase JAK2 is an essential step in cellular signaling by growth hormone (GH) and multiple other hormones and cytokines. Murine JAK2 has a total of 49 tyrosines which, if phosphorylated, could serve as docking sites for Src homology 2 (SH2) or phosphotyrosine binding domain-containing signaling molecules. Using a yeast two-hybrid screen of a rat adipocyte cDNA library, we identified a splicing variant of the SH2 domain-containing protein SH2-B, designated SH2-Bbeta, as a JAK2-interacting protein. The carboxyl terminus of SH2-Bbeta (SH2-Bbetac), which contains the SH2 domain, specifically interacts with kinase-active, tyrosyl-phosphorylated JAK2 but not kinase-inactive, unphosphorylated JAK2 in the yeast two-hybrid system. In COS cells coexpressing SH2-Bbeta or SH2-Bbetac and murine JAK2, both SH2-Bbetac and SH2-Bbeta coimmunoprecipitate to a significantly greater extent with wild-type, tyrosyl-phosphorylated JAK2 than with kinase-inactive, unphosphorylated JAK2. SH2-Bbetac also binds to immunoprecipitated wild-type but not kinase-inactive JAK2 in a far Western blot. In 3T3-F442A cells, GH stimulates the interaction of SH2-Bbeta with tyrosyl-phosphorylated JAK2 both in vitro, as assessed by binding of JAK2 in cell lysates to glutathione S-transferase (GST)-SH2-Bbetac or GST-SH2-Bbeta fusion proteins, and in vivo, as assessed by coimmunoprecipitation of JAK2 with SH2-Bbeta. GH promoted a transient and dose-dependent tyrosyl phosphorylation of SH2-Bbeta in 3T3-F442A cells, further suggesting the involvement of SH2-Bbeta in GH signaling. Consistent with SH2-Bbeta being a substrate of JAK2, SH2-Bbetac is tyrosyl phosphorylated when coexpressed with wild-type but not kinase-inactive JAK2 in both yeast and COS cells. SH2-Bbeta was also tyrosyl phosphorylated in response to gamma interferon, a cytokine that activates JAK2 and JAK1. These data suggest that GH-induced activation and phosphorylation of JAK2 recruits SH2-Bbeta and its associated signaling molecules into a GHR-JAK2 complex, thereby initiating some as yet unidentified signal transduction pathways. These pathways are likely to be shared by other cytokines that activate JAK2.

[Posterior segment complications after macular hole surgery]

Fifty-three patients with stage III or stage IV idiopathic macular holes who underwent vitrectomy were reviewed. Posterior segment complications were noted in 20 (38%) of patients. These included peripheral retinal breaks (21%), peripheral visual field loss of unknown etiology (8%), rhegmatogenous retinal detachment caused by peripheral retinal break (6%), late reopening of the hole (4%), and retinal pigment epithelium loss under the hole (4%). The final visual acuity was two lines or more worse than preoperative visual acuity in 10% of these complicated eyes and in 9% of eyes without posterior segment complications. Patients with peripheral retinal breaks or retinal detachment had significantly shorter duration of macular hole symptoms (p < 0.01) than those without these complications. Posterior segment complications after vitrectomy for macular hole appear to be more common than expected, but the effect of such complications on final visual outcome was not significant.

Structural determination of the O-linked sialyl oligosaccharides liberated from fetuin with endo-alpha-N-acetylgalactosaminidase-S by HPLC analysis and 600-MHz 1H-NMR spectroscopy

The endo-alpha-N-acetylgalactosaminidase from the culture medium of Streptomyces sp. OH-11242 (endo-GalNAc-ase-S) hydrolyzed the O-glycosidic linkage between GalNAc and Ser (Thr) in fetuin, liberating oligosaccharides. The O-linked oligosaccharides liberated from the fetuin with endo-GalNAc-ase-S were pyridylaminated following fractionation on a Bio-Gel P-4 column. The structure of the pyridylaminated O-linked oligosaccharides from fetuin has been determined by reverse-phase HPLC and 600-MHz 1H-NMR spectroscopy. The chemical shifts and the coupling constants of pyridylaminated (PA) NeuAc alpha2-3Gal beta1-3GalNAc were refined by computer simulation of the spectrum. The structures of NeuAc alpha2-3Gal beta1-3(NeuAc alpha2-6)GalNAc-PA and NeuAc alpha2-3Gal beta1-3(NeuAc alpha2-3Gal beta1-4GlcNAc beta1-6)GalNAc-PA were determined by their structural reporter groups.

Immortalized gastric epithelial cell line GSM06 synthesizes hyaluronan under the influence of simian virus 40 large T-antigen expression

GSM06 is a cell line established from the stomach of transgenic mouse harboring a temperature-sensitive simian virus 40 (SV40) large T-antigen gene. 3H-labeled macromolecules produced by the cells incubated with [3H] glucosamine were characterized to examine whether or not GSM06 cells synthesize mucin (mucus glycoprotein). The GSM06 cells grew until a confluent monolayer formed at 33 degrees C (the permissive temperature for SV40 large T-antigen expression), and the 3H-labeled macromolecules appeared in both cell extract and medium during culture for at least 1 week. Unexpectedly, almost all 3H-labeled macromolecules, which were excluded from a column of Sepharose CL-4B, were identified as hyaluronan by analyses using Sepharose CL-2B chromatography, cesium trifluoroacetate equilibrium centrifugation, treatment with dithiothreitol, and trypsin, hyaluronidase, and chondroitinase ABC digestion. At a nonpermissive temperature (39 degrees C), GSM06 cells grew only slightly, but produced much more hyaluronan than at 33 degrees C. The results indicate that GSM06 cells produce not mucin, but hyaluronan, and that the expression of large T-antigen may influence hyaluronan synthesis in GSM06 cells.

Stimulation of mucin metabolism in rat gastric mucosa by histamine

We examined the effects of histamine on mucin localized in the different regions and layers of rat gastric mucosa by determining the changes in the content as well as the biosynthetic activity of the mucin. In vivo administration of 0.8 mg/kg of histamine, which could not induce a concomitant gastric acid secretion, caused a significant increase in the mucin content in the corpus mucosa, but not in the antral mucosa. This increase was due to a significant accumulation of the mucin in the mucus gel and surface mucosa of the corpus region, whereas that in the deep mucosa did not significantly change. In the in vitro incubation system of rat gastric mucosa, histamine and dibutyryl cyclic AMP significantly increased [3H]-labeled mucin in the corpus. The histamine-induced acceleration of mucin biosynthesis was suppressed by ranitidine, but not pyrilamine. In the antrum, the biosynthetic activity showed no significant change by histamine. These results suggest that histamine promotes mucin metabolism via histamine H2 receptors in the surface mucosal layer of the corpus.

Evidence for involvement of IgA1 hinge glycopeptide in the IgA1-IgA1 interaction in IgA nephropathy

The study was performed to investigate the role of the IgA1 hinge region in the IgA1-IgA1 interaction, which was observed previously in IgA nephropathy. The competitive inhibition assays of the IgA1-IgA1 binding were performed using the following candidates for inhibitors: native IgA1 hinge glycopeptide (nHGP), IgA1, IgA2, and IgG. The IgA1-IgA1 binding was definitely inhibited by the nHGP and the IgA1 (maximum of percent inhibition: 66.1 and 60.5%, respectively). There was no obvious inhibition in the IgA2 and the IgG. The inhibition curves of the nHGP and the IgA1 were significantly different from that of the IgG (P < 0.01, respectively). Furthermore, to reveal the detailed binding sites in the interaction, the same inhibition assays were performed using the following substances composing the IgA1 hinge glycopeptide: galactose (Gal), N-acetyl-galactosamine (GalNAc), Gal beta 1-3GalNAc, sialic acid, tetrapeptide PTPS, and synthesized hinge proline-rich peptide PVPSTPPTPSPSTPPTPSPS (sHP). sHP, Gal beta 1-3GalNAc, Gal, and GalNAc inhibited the binding (69.3, 34.1, 14.9, 14.6%, respectively). No obvious inhibition was observed in sialic acid and tetrapeptide PTPS. The inhibition curve of sHP was significantly different from that of the PTPS (P < 0.05). Those of Gal beta 1-3GalNAc, Gal, and GalNAc were also significantly different from that of sialic acid (P < 0.05, respectively). These results suggested that the IgA1-IgA1 interaction could be mediated by the core structure including the peptide and the sugars, except for sialic acid in the hinge region, resulting in the formation of the circulating macromolecular IgA1 in IgA nephropathy.

[Biochemical and genetic mechanisms for bacteria to acquire aminoglycoside antibiotic resistance]

Aminoglycoside (AG)-modifying enzymes are the major biochemical basis for the AG resistance of clinically-occurring bacteria. Recent AG resistance profiles can be characterized by the involvement of AAC(6') in combination with other modifying enzymes in Gram negative bacteria. AAC(6')/APH(2") in Staphylococcus aureus is also remarkable. Genetic basis for the emergence or alteration of AG resistance profiles includes point mutations in the regulatory region or specific sites of the coding region of AG-modifying enzyme genes, and rearrangement of the genes caused by transposon and/or integron. In addition, semisynthetic AG antibiotics such as amikacin, arbekacin (ABK) and isepamicin were also reviewed for their stability to AG-modifying enzymes. ABK that has been widely used as an anti-MRSA drug in Japan is distinct from the other AGs because its monoacetylated derivatives (3"-N-acetylABK and 2'-N-acetylABK) by AG acetyltransferases, AAC(3) and AAC(2'), respectively, retain clear antibiotic activities. Based on this novel aspect and the lack of modification sites for APH(3') and ANT(4'), ABK should be regarded as the most refractory AG for bacteria to acquire resistance.

Recovery of mucin content in surface layer of rat gastric mucosa after HCl-aspirin-induced mucosal damage

Quantitative changes in mucin (mucus glycoprotein) in different layers of rat gastric mucosa after mucosal damage induced by acidified acetylsalicylic acid (HCl-aspirin; 0.15N HCl, 20-200 mg acetylsalicylic acid/kg body weight) were studied. More than 50 mg/kg HCl-aspirin led to a significant increase in macroscopic gastric injury (expressed as ulcer index) at 3 h, compared with control (no aspirin) and there was a significant recovery at 7 h. Three h after dosing with 50 mg/kg acidified aspirin, there was superficial mucosal damage and decreased mucin content in the surface mucosal layer. Mucin production recovered 7 h after the administration of 50 mg/kg acidified aspirin. Doses of acidified aspirin higher than 100 mg/kg decreased mucin content in the surface and deep corpus mucosal layers and no recovery was seen 7 h after the administration. Physiological damage after the administration of 50 mg/kg HCl-aspirin was limited mainly to surface epithelial mucus cells. An experimental model in which superficial erosion was induced in rat gastric mucosa was established with low-dose HCl-aspirin.

Comparative study of carbohydrate portion of gastrointestinal mucins using enzyme-linked lectin-binding assay (ELLA)

We improved the enzyme-linked lectin-binding assay (ELLA) to determine the differences in the carbohydrate chains of corpus, antral, duodenal ant colonic rat mucins. First we have improved the optimal conditions of this assay for mucins; ELLA makes possible the detection of 1.5 ng of hexose in rat gastrointestinal mucins (5-7 ng of mucins). Salt concentrations of several dozens mM are required for mucin coating on the plate. Non-ionic detergents diminish the adsorption of mucins onto the plate. Secondly we tested a set of 8 lectins to compare their binding to the gastrointestinal mucin samples. It is possible to detect crude mucins as well as purified mucins using ELLA. Gastric mucins have less Tn-antigen than duodenal and colonic mucins. Corpus and duodenal mucins have more of the H-type 2 chain than antral and colonic mucins.

[Prostagrandin E1-induced hypotension well maintains cerebral circulation and carbon dioxide reactivity in non-neurosurgical patients under sevoflurane-anesthesia]

To evaluate the effect of prostagrandin E1 (PGE1)-induced hypotension on cerebral blood flow (CBF) and carbon dioxide (CO2) reactivity of CBF, regional cerebral hemoglobin oxygen saturation (rSo2) was measured in non-neurosurgical patients (n = 10) under sevoflurane-anesthesia using near infrared spectroscopy. PGE1 was infused intravenously to maintain arterial pressure at a level of about 75% of the MAP (hypotensive group) under sevoflurane-anesthesia alone (normotensive group). Ventilation was controlled to adjust PaCO2 to hypocapnia (25-30 mmHg), normocapnia (35-40 mmHg) and hypercapnia (45-50 mmHg) in both normotensive and hypotensive groups. rSo2 during hypotension did not change by hypocapnia and normocapnia, but significantly increased by hypercapnia, compared with rSo2 during normotension. Significant correlations between rSo2 and PaCO2 during both normotensive and hypotensive groups were observed. Slope of the regression line of rSo2 and PaCO2 did not differ between the normotensive and hypotensive groups. When arterial oxygen content and cerebral metabolic rate of oxygen are constant, changes in rSo2 correlate with those of CBF. Therefore, CBF and CO2 reactivity of CBF that indicates autoregulation in response to changes in CO2 during hypotension were maintained as those during normotension. The results show that PGE2-induced hypotension maintains CBF and CO2 reactivity well in non-neurosurgical patients under sevoflurane anesthesia.

Construction of pRES18 and pRES19, Streptomyces-Escherichia coli shuttle vectors carrying multiple cloning sites

We developed two Streptomyces-Escherichia coli shuttle vectors. The plasmid pRES102, consisting of the essential region of pRES1 and the thiostrepton resistance gene (tsr) fragment of pIJ702, was combined with the E. coli plasmid vector pUC18 or pUC19. The resulting shuttle vectors, designated pRES18 and pRES19, respectively, have relatively compact size (6.25 kb), low copy number, multiple cloning sites reciprocally arranged in opposite directions, and selection markers for both Streptomyces (tsr) and E. coli (beta-lactamase (bla) and beta-galactosidase (lacZ). These shuttle vectors are capable of carrying DNA fragments as long as 10 kb, of being maintained in S. griseus, S. lavendulae and S. lividans, and are compatible with pIJ702.

Bni1p implicated in cytoskeletal control is a putative target of Rho1p small GTP binding protein in Saccharomyces cerevisiae

The RHO1 gene encodes a homolog of mammalian RhoA small GTP binding protein in the yeast Saccharomyces cerevisiae. Rho1p is localized at the growth sites, including the bud tip and the cytokinesis site, and is required for bud formation. We have recently shown that Pkc1p, a yeast homolog of mammalian protein kinase C, and glucan synthase are targets of Rho1p. Using the two-hybrid screening system, we cloned a gene encoding a protein which interacted with the GTP-bound form of Rho1p. This gene was identified as BNI1, known to be implicated in cytokinesis or establishment of cell polarity in S.cerevisiae. Bni1p shares homologous domains (FH1 and FH2 domains) with proteins involved in cytokinesis or establishment of cell polarity, including formin of mouse, capu and dia of Drosophila and FigA of Aspergillus. A temperature-sensitive mutation in which the RHO1 gene was replaced by the mammalian RhoA gene showed a synthetically lethal interaction with the bni1 mutation and the RhoA bni1 mutant accumulated cells with a deficiency in cytokinesis. Furthermore, this synthetic lethality was caused by the incapability of RhoA to activate Pkc1p, but not glucan synthase. These results suggest that Rho1p regulates cytoskeletal reorganization at least through Bni1p and Pkc1p.

Regulation of obese (ob) mRNA and plasma leptin levels in rhesus monkeys. Effects of insulin, body weight, and non-insulin-dependent diabetes mellitus

We have cloned the rhesus monkey obese cDNA and have analyzed its expression in monkeys with a wide range of body weights (lean to very obese) and with or without non-insulin-dependent diabetes mellitus to examine the relationship of ob gene expression to obesity and non-insulin-dependent diabetes mellitus. The sequence of monkey ob protein, excluding the signal peptide, showed 91% identity with the human protein. We observed a significant correlation between the level of ob mRNA and body weight. We also found a significant relationship between ob mRNA and fasting plasma insulin concentration; however, insulin stimulation during a 100-140-min euglycemic/hyperinsulinemic clamp did not result in any changes in ob mRNA levels. Circulating levels of the ob gene product leptin were also significantly correlated with body weight. These results show that ob gene expression is related to body weight and is not acutely regulated by insulin.

Establishment of monoclonal antibodies against carbohydrate moiety of gastric mucins distributed in the different sites and layers of rat gastric mucosa

Eight monoclonal antibodies (MAbs), designated RGM21 approximately RGM42, were generated against mucin purified from the rat gastric mucosa. By applying ELISA, all of these MAbs were proved to react not only with the purified mucin, but also with the oligosaccharide mixture obtained from the antigenic mucin by alkaline borohydride treatment. Treatment of the mucin-attached ELISA well with trypsin, sodium periodate or galactose oxidase prior to the addition of the MAb was applied to characterize these MAbs. Histochemical observation indicated that all these MAbs were able to stain the formalin fixed-paraffin embedded sections of the rat gastroduodenal mucosa. Although each of these MAbs reacted with distinct mucus-producing cells localized in particular regions of the gastroduodenal mucosa, their staining specificity could generally be classified into four groups. These MAbs might be useful for estimating the physiological and pathological changes of mucins in the gastric mucosa.

Interaction of a GRB-IR splice variant (a human GRB10 homolog) with the insulin and insulin-like growth factor I receptors. Evidence for a role in mitogenic signaling

We have utilized the yeast two-hybrid system to identify proteins that interact with the cytoplasmic domain of the insulin receptor. We identified a human cDNA that is a splice variant of the human GRB10 homolog GRB-IR, which we term GRB10/IR-SV1 (for GRB10/GRB-IR splice variant 1). The protein encoded by the GRB10/IR-SV1 cDNA contains an SH2 domain and a pleckstrin homology domain. Cloning of a full-length human cDNA revealed a predicted coding sequence that was similar to the mouse GRB10 protein, although GRB10/IR-SV1 contained an 80-amino acid deletion. The GRB10/IR-SV1 cDNA is a splice variant of the GRB-IR cDNA such that GRB10/IR-SV1 contains an intact pleckstrin homology domain and a distinct amino terminus. The interaction of GRB10/IR-SV1 with the insulin receptor and the insulin-like growth factor I (IGF-I) receptor is mediated by the SH2 domain, and we show that glutathione S-transferase-SH2 domain fusion proteins interact specifically in vitro with the insulin receptor derived from mammalian cells. The GRB10/IR-SV1 SH2 domain also interacted with an approximately 135-kDa phosphoprotein from unstimulated cell lysates, an interaction that decreased after insulin stimulation. We present evidence that the GRB10/IR-SV1 protein plays a functional role in insulin and IGF-I signaling by showing that microinjection of an SH2 domain fusion protein inhibited insulin- and IGF-I-stimulated mitogenesis in fibroblasts, yet had no effect on mitogenesis induced by epidermal growth factor. Our findings suggest that GRB10/IR-SV1 may serve to positively link the insulin and IGF-I receptors to an uncharacterized mitogenic signaling pathway.