[Autoradiographic study of myocardial fatty acid metabolism in diabetic mouse using 125I-BMIPP]

The existence of diabetic cardiomyopathy has been substantiated in patients with diabetes mellitus. In this study we evaluated two mice with diabetes mellites (DM) and two control mice to determine whether the fatty acid metabolism of the myocardium is abnormal when 125I-BMIPP is used. 125I-BMIPP of 0.74 MBq (20 microCi) was injected, and 30 min later, the mice were slaughtered. Heart, lungs, liver, spleen and kidneys were removed. After freezing the heart, myocardium was sliced into 20 micron sections using a cryostat. Each slice was placed in contact with an imaging plate for autoradiography. A bioimaging analyzer was used to analyze the data. The percent injected dose/g of heart was lower in the DM group than in the control group (11.6 +/- 0.49 vs 18.3 +/- 1.27). Each slice of the DM group also had fewer counts than slices in the control group (p < 0.05 or p < 0.01). These results indicated that fatty acid metabolism in the myocardium was less in the DM group than in the control group.

Effects of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine on intestinal polyp development in Apc delta 716 knockout mice

Damage to the human adenomatous polyposis coli (APC) gene is responsible for not only familial adenomatous polyposis but also many sporadic cancers of the entire digestive tract. Using homologous recombination in embryonic stem cells, we recently constructed gene knockout mice with a truncation mutation in the Apc gene. These heterozygous mice developed intestinal polyps. We found that all microadenomas dissected from the earliest polyps had already lost the wild-type allele, indicating loss of heterozygosity (LOH) (Oshima et al., Proc. Natl. Acad. Sci. USA 92:4482-4486, 1995). Using these knockout mice, we investigated the effects of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhlP), one of the most abundant heterocyclic amines found in cooked meat and fish. When PhIP was fed to these mice at 400 ppm for 8 wk, the polyp distribution shifted to a larger size range, although the total polyp number did not change significantly. Similar, but weaker, effects were observed with the other heterocyclic amines 2-amino-3-methylimidazo[4,5-f]quinoline and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline. On the other hand, intraperitoneal injections of 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-OH-PhlP) at a higher dose (50 mg/kg) for five consecutive days increased the polyp number significantly. This increment was not associated with mutations in the Apc gene; however, most polyps showed loss of the full-length Apc allele (LOH). These results suggest that PhIP affects intestinal polyp development by accelerating the growth rate of microadenomas. It is also possible that high doses of N-OH-PhIP increase the frequency of Apc gene LOH.

Dolichyl phosphate, a potent inducer of apoptosis in rat glioma C6 cells

Exposure of rat glioma C6 cells to dolichyl phosphate resulted in cell shrinkage followed by nuclear fragmentation and internucleosomal cleavage of genomic DNA, yielding ladder patterns of oligonucleosomal fragments, all characteristics of apoptosis. This phenomenon occurred in a dose and time dependent manner. Dolichol and prenol failed to induce apoptosis. The inhibitors of N-glycosylation, tunicamycin and swainsonine had no apparent effect on dolichyl phosphate-induced apoptosis. Apoptotic changes were also observed in HL-60 cells, SIRC cells and HeLa cells. Thus, dolichyl phosphate functions as a potential apoptosis inducer as well as an essential carrier lipid in the biosynthesis of N-linked glycoprotein.

Effects of docosahexaenoic acid (DHA) on intestinal polyp development in Apc delta 716 knockout mice

Epidemiological studies and animal experiments show an association of dietary intake of fish oils and low incidence of several types of cancers. The active ingredients of fish oils appear to be polyunsaturated fatty acids of omega-3 type such as eicosapentaenoic acid and docosahexaenoic acid (DHA). We have investigated chemopreventive effects of DHA on mouse intestinal polyposis using adenomatous polyposis coli (Apc) gene knockout mice. Damage to the human APC gene is responsible for not only familial adenomatous polyposis but also many sporadic cancers of the entire digestive tract. Using homologous recombination in embryonic stem cells, we recently constructed gene knockout mice containing a truncation mutation in the Apc gene at codon 716 (Apc delta 716). The heterozygous mice developed numerous intestinal polyps, and all microadenomas dissected from the earliest polyps had already lost the wild-type allele, indicating the loss of heterozygosity [Oshima et al. (1995), Proc. Natl Acad. Sci. USA, 92, 4482-4486]. We fed Apc delta 716 heterozygotes with AIN-76A purified diet containing 3% DHA for 7 weeks, and scored the number and size of intestinal polyps. Average DHA intakes per day were 4.1 and 4.3 g/kg body wt for males and females, respectively. DHA-fed females had only 31% of polyps compared with the control females that developed about 220 polyps, whereas DHA-fed females showed no significant decrease in the polyp number. As for the polyp size, the proportion of larger polyps decreased more significantly in females than in males. This is the first demonstration that DHA inhibits intestinal polyposis induced by an Apc mutation at both its formation and growth.

[Falls among the elderly living in a rural community--prevalence and circumstances of falls by season]

The purpose of the study is to assess the prevalence and circumstances of falls by season among the elderly living in a rural community. From 1992 to 1993 four interview surveys on falls were conducted every three months. Out of the total 1,321 subjects aged 65 and over (male: 532, mean age: 73.2 yr, female: 789, mean age: 74.5 yr), 1,317 responded to the survey in summer, 1,306 in autumn, 1,236 in winter and 1,248 in spring. The prevalence of falls (the rate of subjects with falls) were 7.4% in summer, 5.9% in autumn, 6.5% in winter and 6.7% in spring. The seasonal variation was not statistically significant. In each season, there was no significant difference between genders. The prevalence in the older group aged 75 and over is higher than that in younger group aged 65-74 except in spring. As to the circumstances of falls, there were seasonal differences in the distribution of place, footwear and cause of falls. These differences may be due to the climate of the area.

Down-regulation of c-neu receptors by nerve growth factor in PC12 cells

A small number of p185c-neu receptors have been found on PC12 cells. These receptors show some basal phosphorylation in quiescent cells. When the cells are treated with nerve growth factor (NGF) for a short time, some increase in phosphorylation is seen, mainly on serine and threonine residues, and this is accompanied by a slight shift in the apparent molecular weight. Epidermal growth factor (EGF) also increases the phosphorylation of p185c-neu, in this case on tyrosine residues. Neither heregulin-beta 1 nor gp30 stimulates the tyrosine phosphorylation of p185c-neu, and neither has a proliferative effect on the cells. Treatment of the cells with NGF for 5 days produces a 70-80% reduction in the number of p185c-neu receptors. This down-regulation does not occur when PC12nnr5 cells, which lack the high-affinity NGF receptor, p140trk, are treated with NGF. The level of p185c-neu mRNA is not altered by NGF treatment, suggesting that the down-regulation is due to either a translational or a posttranslational alteration.

Evidence against dominant negative mechanisms of intestinal polyp formation by Apc gene mutations

Mutations in the adenomatous polyposis coli (APC) gene are responsible for not only familial adenomatous polyposis but also many sporadic cancers of the digestive tract. Most mutations found in familial adenomatous polyposis patients are of the truncation type, and the phenotype is affected by the mutation sites in the gene. Truncated APC proteins can associate with the wild-type protein. Accordingly, it has been proposed that the polyposis is caused by a dominant negative mechanism. To test this possibility, we constructed transgenic mice that contained mutant minigenes. They expressed the APC protein truncated either at codon 716 (Apc delta 716) or 1287 (Apc delta 1287) at high levels in the intestinal epithelium. Contrary to our expectation, no intestinal polyps or tumors were found in any of such mice, even after 7 months. These results rule out any dominant negative mechanisms in which the truncated APC protein is directly involved in the formation of intestinal polyps in the mouse.

Effect of amino acid substitutions within the region 62-76 of I-A beta b on binding with and antigen presentation of Torpedo acetylcholine receptor alpha-chain peptide 146-162

Previous study has shown that reduced T cell response to peptide alpha 146-162 of Torpedo californica acetylcholine receptor (tAChR) in B6.C-H-2bm12 (bm12) mice, a mutant of C57BL/6 (B6) mice, correlated with its nonsusceptiblity to experimental autoimmune myasthenia gravis. There are three amino acid differences between the I-A beta b of the two strains (positions 67, 70, and 71). We synthesized peptides I-A beta b62-76 (peptide b6), I-A beta bm1262-76 (peptide bm), and three additional peptides, b6(67F), b6(70Q), and b6(71K), and determined their ability to bind peptide alpha 146-162 and the dissociation constants (Kd) of the binding. Peptide alpha 146-162 bound with a significantly higher affinity to peptide b6 than to peptides bm or b6(71K), suggesting that the lower affinity of peptide alpha 146-162 to I-Abm12 is a factor in the reduced response to this peptide by bm12 T cells. This was confirmed by measurement of the Kd values of the binding of peptide alpha 146-162 to the I-A molecules of B6 and bm12. Furthermore, APC of bm12 presented the peptide, or tAChR, poorly to peptide-specific or to tAChR-specific B6 T cells. The major effect is caused by the change of Thr-71 in I-A beta b to lysine in I-A beta bm12. However, APC of B6 also presented peptide alpha 146-162 much less efficiently to peptide-specific T cells of bm12. This demonstrated that these three amino acid changes also influence the T cell receptor recognition of peptide-MHC complex and that both B6 and bm12 T cells recognizing peptide alpha 146-162 or tAChR are under a high H-2 restriction.

Effect of amino acid substitutions within the region 62-76 of I-A beta b on binding with and antigen presentation of Torpedo acetylcholine receptor alpha-chain peptide 146-162

Previous study has shown that reduced T cell response to peptide alpha 146-162 of Torpedo californica acetylcholine receptor (tAChR) in B6.C-H-2bm12 (bm12) mice, a mutant of C57BL/6 (B6) mice, correlated with its nonsusceptiblity to experimental autoimmune myasthenia gravis. There are three amino acid differences between the I-A beta b of the two strains (positions 67, 70, and 71). We synthesized peptides I-A beta b62-76 (peptide b6), I-A beta bm1262-76 (peptide bm), and three additional peptides, b6(67F), b6(70Q), and b6(71K), and determined their ability to bind peptide alpha 146-162 and the dissociation constants (Kd) of the binding. Peptide alpha 146-162 bound with a significantly higher affinity to peptide b6 than to peptides bm or b6(71K), suggesting that the lower affinity of peptide alpha 146-162 to I-Abm12 is a factor in the reduced response to this peptide by bm12 T cells. This was confirmed by measurement of the Kd values of the binding of peptide alpha 146-162 to the I-A molecules of B6 and bm12. Furthermore, APC of bm12 presented the peptide, or tAChR, poorly to peptide-specific or to tAChR-specific B6 T cells. The major effect is caused by the change of Thr-71 in I-A beta b to lysine in I-A beta bm12. However, APC of B6 also presented peptide alpha 146-162 much less efficiently to peptide-specific T cells of bm12. This demonstrated that these three amino acid changes also influence the T cell receptor recognition of peptide-MHC complex and that both B6 and bm12 T cells recognizing peptide alpha 146-162 or tAChR are under a high H-2 restriction.

Loss of Apc heterozygosity and abnormal tissue building in nascent intestinal polyps in mice carrying a truncated Apc gene

Mutations in the APC (adenomatous polyposis coli) gene appear to be responsible for not only familial adenomatous polyposis but also many sporadic cases of gastrointestinal cancers. Using homologous recombination in mouse embryonic stem cells, we constructed mice that contained a mutant gene encoding a product truncated at a 716 (Apc delta 716). Mendelian transmission of the gene caused most homozygous mice to die in utero before day 8 of gestation. The heterozygotes developed multiple polyps throughout the intestinal tract, mostly in the small intestine. The earliest polyps arose multifocally during the third week after birth, and new polyps continued to appear thereafter. Surprisingly, every nascent polyp consisted of a microadenoma covered with a layer of the normal villous epithelium. These microadenomas originated from single crypts by forming abnormal outpockets into the inner (lacteal) side of the neighboring villi. We carefully dissected such microadenomas from nascent polyps by peeling off the normal epithelium and determined their genotype by PCR: all microadenomas had already lost the wild-type Apc allele, whereas the mutant allele remained unchanged. These results indicate that loss of heterozygosity followed by formation of intravillous microadenomas is responsible for polyposis in Apc delta 716 intestinal mucosa. It is therefore unlikely that the truncated product interacts directly with the wild-type protein and causes the microadenomas by a dominant negative mechanism.

Enhanced expression of GM2/GD2 synthase mRNA in human gastrointestinal cancer

BACKGROUND

The content of the GM2 ganglioside and the activity of UDP-GalNAc: GM3 beta-1,4N-acetylgalactosaminyltransferase (beta-1,4GalNAcT), which synthesizes GM2, increased in gastric cancer tissues and gastric cancer cell lines as compared with that in normal gastric mucosa.

METHODS

Expression of beta-1,4GalNAcT mRNA and a concentration of GM2 in the human gastrointestinal tissues were examined. Beta-1,4GalNAcT mRNA in human surgical specimens, which was not detectable with Northern blotting because of the paucity of absolute amounts expressed, was detected with competitive reverse transcription-polymerase chain reaction (PCR) method using an internal standard cRNA that could be amplified by the same primers as target mRNA in PCR. The quantification of GM2 was examined using immunostaining of thin-layer chromatography.

RESULTS

In 10 of 10 gastric carcinomas and 6 of 13 colonic carcinomas, mRNA expression was more enhanced than that in the normal mucosa of each patient. The alteration of GM2 content in carcinoma from normal tissue generally was correlated to the change in the expression of beta-1,4GalNAcT mRNA with a few exceptions. One gastric cancer sample had a higher level of mRNA with a lower GM2 content than the corresponding normal tissue, and two colonic carcinoma tissue specimens had a lower level of mRNA with a higher GM2 content.

CONCLUSIONS

These results suggest that expression of the beta-1,4GalNAcT gene is a key step in the molecular mechanisms underlying the regulation of cancer-associated GM2 expression in the stomach and the colon.

Reactivity of a mouse/human chimeric anti-GM2 antibody KM966 with brain tumors

With the aim of investigating the passive immunotherapy of brain tumors, we examined the binding of a mouse/human chimeric anti-ganglioside GM2 antibody KM966 to various organs and brain tumors. Frozen sections of 51 surgically resected brain tumors were stained with antibody KM966. Fourteen gliomas out of 16 were stained positively with antibody KM966. Eleven positive sections demonstrated homogenous staining. No specific binding to normal gray matter and white matter was observed. Some cases of meningiomas, neurinomas and metastatic brain tumors were stained with KM966 but with less frequency and intensity than gliomas. In addition, KM966 demonstrated strong antibody-dependent cellular cytotoxicity against human malignant glioma cells. These results showed that antibody KM966 will be useful for passive immunotherapy of malignant gliomas.

Profile of the regions of acetylcholine receptor alpha chain recognized by T-lymphocytes and by antibodies in EAMG-susceptible and non-susceptible mouse strains after different periods of immunization with the receptor

C57BL/6 (B6) mice develop a neuromuscular disease, experimental autoimmune myasthenia gravis (EAMG), after two or more immunizations with Torpedo californica acetylcholine receptor (AChR). To determine whether EAMG is related to recognition of particular region(s) on the main extracellular domain of the alpha chain (residues alpha 1-210) in prolonged immunization, we have examined the differences in the antibody and T cell recognition profiles of B6 and SJL (a strain that does not develop EAMG) mice after different periods and a number of immunizations with Torpedo AChR. In a given strain, antibodies and T cells recognized immunodominant regions, which may coincide or may be uniquely B cell or T cell determinants. Both B6 and SJL exhibited similar antibody recognition profiles after the second and through the fourth immunizations with AChR. Major differences between the two strains were found in their T cell recognition of regions in the second part (residues 100-210) of the main extracellular domain of the alpha chain. T cells of SJL recognized consistently only one region (111-126) within this part of the alpha chain, whereas in B6, T cell recognition of three peptides (111-126, 146-162 and 182-198) and next neighbor regions to them persisted throughout the period. Of these three peptides, 146-162 was an immunodominant peptide unique to B6, as the other two peptides (111-126 and 182-198) were also recognized by either T cells or antibodies in SJL. To study the role of the T cells recognizing region 146-162 in EAMG, a T cell line was generated against this region and the cells transferred into B6 mice followed by one Torpedo AChR injection. Enhancement of antibody production toward alpha chain peptides was observed as an influence of T cell transfer compared to profiles at 1 week. In addition, one out of three mice examined showed signs of EAMG. These results suggest the importance of T cells recognizing residues 146-162 in EAMG. It is concluded that the presence of persistent T cell responses to the second half (residues (100-210) of the main extracellular domain of the alpha chain is associated with the development of EAMG in B6 mice, while absence of these responses in SJL mice may enable them to escape the disease. The preservation of the immunodominance of peptide 146-162 in the T cell recognition of B6 is probably most important for the pathogenesis of EAMG in this strain.

Plasmenylethanolamine in human intestinal mucosa detected by an improved method for analysis of phospholipid

Analysis of phospholipid and their fatty acid composition of human intestinal mucosa was performed by an method elaborated to analyze the limited amount of sample with 2-dimensional TLC followed by lipid-phosphorus determination. Using this method, plasmenylethanolamine was detected in human intestinal mucosa and accounted for about 7% of phospholipid in small and large intestinal mucosa. The amounts of polyunsaturated fatty acids of phosphatidylethanolamine were higher than those of other phosphoglycerides in intestinal mucosa, hence, inflammation-related eicosanoids may originate from ethanolamine containing phospholipid.

Major defect of carbohydrate-deficient-glycoprotein syndrome is not found in the synthesis of dolichyl phosphate or N-acetylglucosaminyl-pyrophosphoryl-dolichol

The contents of dolichyl phosphate and UDP-N-acetylglucosamine:dolichyl phosphate N-acetylglucosamine 1-phosphate transferase (GlcNAc-1-P transferase) activity in fibroblasts from patients with carbohydrate-deficient-glycoprotein (CDG) syndrome were analyzed. The amount of dolichyl phosphate and GlcNAc-1-P transferase activity in CDG syndrome fibroblasts were similar to those in normal fibroblasts, suggesting that CDG syndrome may not be due to a deficiency of a biosynthetic enzyme for dolichol-oligosaccharide intermediates, but to a metabolic error in assembly of asparagine-linked oligosaccharide.

Churg-Strauss syndrome (allergic granulomatous angiitis) with multiple perforating ulcers of the small intestine, multiple ulcers of the colon, and mononeuritis multiplex

A case of Churg-Strauss syndrome with multiple perforations of the small intestine is described. A 31-year-old woman was admitted with a complaint of epigastric pain. She had a history of bronchial asthma. One week before admission, white blood cell count was 20,800/mm3 with 59% eosinophils. Neurological examination on admission disclosed mononeuritis multiplex with paresthesia in both the lower and upper extremities. At colonoscopy, there were scattered aphthous ulcers in the colon. Ophthalmological examination revealed allergic conjunctivitis. After admission, hypereosinophilia increased to as high as 36,000/mm3. Oral administration of prednisolone (60 mg/day) was begun. On the 3rd day of the treatment, the eosinophil count decreased dramatically, to 400/mm3, while severe abdominal pain developed. Since abdominal X-ray film revealed free air in the abdominal cavity, emergency laparotomy was performed and multiple intestinal ulcers with perforations were found. Partial ileectomy was performed. Pathological findings of the resected specimen were interpreted as a necrotizing angiitis with extravascular granuloma. Since the operation, the patient has been asymptomatic, except for neurological symptoms. Hypereosinophilia has decreased without treatment to counts averaging 270/mm3, within 3 months. On the basis of the clinical features and histopathological findings, a diagnosis of Churg-Strauss syndrome was established.

Fucosyltransferase-producing sialyl Le(a) and sialyl Le(x) carbohydrate antigen in benign and malignant gastrointestinal mucosa

BACKGROUND

Sialyl Le(a) antigen and sialyl Le(x) antigen are cancer-associated carbohydrate antigens. Previous immunohistologic and immunochemical studies have shown that these antigens are preferentially expressed in gastric cancer and colonic cancer and that they possibly are related to the metastatic potential of the cancer cells. The biosynthesis of these antigens is completed by fucosyltransferases, but it has not been reported how fucosyltransferases control the expression of these carbohydrate antigens concerning the invasive potential of the cancer.

METHODS

The authors established an assay system for measuring the activity of alpha 1-->4 fucosyltransferase (sialyl Le(a) synthase) and alpha 1-->3 fucosyltransferase (sialyl Le(x) synthase) with a high-pressure liquid chromatography system (HPLC). The activity was measured in various parts of normal and cancerous gastric and colonic tissue and compared with the expression of sialyl Le(a), sialyl Le(x), Le(a), and Le(x) antigens determined in a solid-phase enzyme-linked immunosolvent assay (EIA).

RESULTS

Sialyl Le(a) synthase was detected in most normal or malignant mucosa of gastric and colonic tissues, regardless of anatomic locations. Sialyl Le(x) synthase activity generally was low in the normal gastric mucosa, whereas the activity was higher in 77% (7 of 9) of gastric cancer tissues than in corresponding normal tissues with enhanced expression of sialyl Le(x) antigen in most patients (5 of 7). In the large intestine, the activity of sialyl Le(a) synthase and sialyl Le(x) synthase was correlated. Although enhanced expression of sialyl Le(x) in colonic cancer was observed in 86% (12 of 14) of all patients, concomitant higher sialyl Le(x) synthase activity than that in normal tissue was observed in only 58% (7 of 12) of patients.

CONCLUSIONS

The expression of sialyl Le(a) and sialyl Le(x) antigens in the stomach and the colon was not controlled solely by fucosyltransferases but by a more complicated system involving other glycosyltransferases.

Sequential microanalyses of free dolichol, dolichyl fatty acid ester and dolichyl phosphate levels in human serum

Sequential microanalyses of free dolichol, dolichyl fatty acid ester and dolichyl phosphate in human serum were made. To determine the level of each dolichol, samples were pretreated using three different methods prior to fluorescent derivatization. To estimate the concentrations of free dolichol, samples were added to alkaline methanol and kept at room temperature for 1 h. In case of dolichyl fatty acid ester, samples were saponified at 100 degrees C for 1 h. To estimate dolichyl phosphate, saponified lipid extracts were treated with acid phosphatase. Each pretreated dolichol was reacted with anthracene-9-carboxylic acid and amounts of 9-anthroyl derivatives were determined fluorometrically by HPLC. This method is simple and three types of dolichols can be estimated using the same HPLC system. This analysis is also sufficiently sensitive for measurement of serum dolichol levels. The contents of free dolichol, dolichyl fatty acid ester and dolichyl phosphate in human serum were found to be 44.9 +/- 10.5 ng/ml (n = 32), 76.4 +/- 24.2 ng/ml (n = 32) and 43.5 +/- 15.1 ng/ml (n = 13), respectively. These levels had apparently no correlation to age or serum total cholesterols. A linear correlation between dolichols and high-density lipoprotein cholesterols reflects the fact that the dolichols are associated with the high-density lipoprotein fraction.