Cell type-specific changes of the membrane properties of peripherally-axotomized dorsal root ganglion neurons in a rat model of neuropathic pain

Recent evidence indicates that neuropathic pain from partial peripheral nerve injury is maintained by electrophysiologically abnormal signals from injured sensory neurons. To gain an insight into the mechanisms underlying this electrophysiological abnormality, we examined the effects of S1 spinal nerve transection on the membrane properties of S1 dorsal root ganglion neurons one to two weeks after injury. This injury produced significant action potential broadening [40% (1 ms) in C-, 149% (1.5 ms) in A delta- and 84% (0.5 ms) in A alpha/beta-cells], which was primarily due to the enhancement of the "shoulder" appearing on the falling phase of the action potential in C- and A delta-cells and the emergence of a shoulder in A alpha/beta-cells, and significant cell-type specific changes in the time-course of the rising phase of the action potential; i.e. an increase in rise time (A delta: 35%, 0.15 ms; A alpha/beta: 13%, 0.04 ms) and a decrease in the maximal rate of rise (A delta: 17%, 77 V/s; A alpha/beta: 13%, 79 V/s). In addition, the nerve injury led to a significant reduction of the rheobase, an index of neuronal excitability, in all types of cells (by 41% in C-, 71% in A delta- and 59% in A alpha/beta-cells). The reduction of rheobase in A-cells was associated with a concomitant increase in apparent input resistance (by 269% in A delta- and 192% in A alpha/beta-cells), which was measured near the resting membrane potential. By contrast, the rheobase reduction in C-cells was associated with a concurrent depolarizing shift (approximately 4 mV) of the resting membrane potential. The nerve injury-induced reduction of rheobase was not accompanied by related change in input resistance or threshold potential in any of the cell populations. The present results indicate that chronic peripheral axotomy of dorsal root ganglion neurons, which gives rise to neuropathic pain, produces profound changes in the action potential waveform of dorsal root ganglion neurons in a cell type-specific fashion. Furthermore, the results suggest that the axotomy increases the excitability of dorsal root ganglion neurons not by altering input resistance (i.e. leak conductance) or threshold potential, but by increasing apparent input resistance near the resting membrane potential in A-cells and decreasing the resting membrane potential in C-cells.

Diet, lifestyle, and colorectal cancer: is hyperinsulinemia the missing link?

Several dietary and other lifestyle factors have been implicated in the development of colorectal cancer. However, the precise nature and actual magnitude of the relationship between individual nutrient intakes and other lifestyle factors and colorectal cancer risk are not clear. A unifying hypothesis has recently been proposed that explains why obesity, physical inactivity, alcohol, and consumption of a typical Western diet increase colorectal cancer risk. This hypothesis suggests that these dietary and other lifestyle factors are associated with insulin resistance and hyperinsulinemia and that hyperinsulinemia, in turn, may stimulate growth of colorectal tumors. Two recently published large prospective epidemiologic studies indicate a significant increase in colorectal cancer risk in subjects with diabetes mellitus, thereby supporting this hypothesis.

Characterization of bovine and human cDNAs encoding NAP-22 (22 kDa neuronal tissue-enriched acidic protein) homologs

We have characterized the bovine and the human cDNAs encoding the NAP-22 (22 kDa neuronal tissue-enriched acidic protein) homologs. Both bovine and human cDNAs encode proteins of 227 amino acids. The deduced amino acid sequences of the bovine and the human proteins are 63% and 65% identical, respectively, to that of rat NAP-22 protein, strongly suggesting that both the cDNAs characterized encode NAP-22 proteins. They also share 45% and 41% amino acid sequence identities with chicken CAP-23 (23 kDa cytoskeleton associated protein). Several important protein motifs, including myristoylation and phosphorylation sites, are well conserved in sequences and positions in all three mammalian NAP-22 proteins and chicken CAP-23 proteins. The bovine cDNA was characterized further. Southern analysis of the bovine genomic DNA suggests that the bovine NAP-22 protein is encoded by a single-copy gene. RNA blot analysis revealed that the bovine gene for NAP-22 protein encodes a 1.7 kb transcript that is present only in the brain. Our data suggest that the four proteins, bovine and human NAP-22 homologs, rat NAP-22, and chicken CAP-23, have homologous functions in different organisms.

Na+/H+ exchange inhibition improves long-term myocardial preservation

BACKGROUND

Na+/H+ exchange plays an important role in the ionic changes observed during myocardial ischemia and reperfusion. We investigated the cardioprotective efficacy of a selective Na+/H+ exchange inhibitor, 4-isopropyl-3-methylsulfonyl-benzoylguanidin-methanesulfonate (HOE642), in a canine model of long-term heart preservation.

METHODS

Canine donor hearts were stored for 24 hours in hyperkalemic crystalloid cardioplegic solution; in cardioplegic solution enriched with HOE642; in cardioplegic solution enriched with HOE642, with donor and recipient treated with HOE642; in standard cardioplegic solution, with donor and recipient treated with HOE642; or in standard cardioplegic solution, with only the recipient treated. After orthotopic transplantation, pressure-volume relationships were obtained and dogs were weaned from bypass. Morphology was studied.

RESULTS

Myocardial compliance was well preserved when donor and recipient were treated. These groups had the lowest myocardial water content, and no morphologic signs of irreversible damage. In these groups, weaning from cardiopulmonary bypass was successful in 10 of 10 animals, with a cardiac index around 2 L x min(-1) x m(-2). Only 3 of 5 animals in each of the other three groups could be weaned, with significantly lower cardiac indices.

CONCLUSIONS

Treatment with HOE642 in both donor and recipient improves myocardial compliance, postweaning cardiac index, and ultrastructure of donor hearts preserved for 24 hours and orthotopically transplanted.

Prevalence estimation of dementia in a rural area of Korea

OBJECTIVES

A cross-sectional survey was conducted to estimate prevalence of dementia and to determine factors related to dementia among residents in a rural area, Yonchon county, Korea, in 1993.

PARTICIPANTS

Of the study population more than 65 years of age (n = 2171), 1674 persons participated in the cross-sectional survey using the Korean version of the Mini-Mental State Examination (MMSE-K).

DESIGN

Subjects were defined as having dementia according to NINCDS-ADRDA criteria through direct interview by psychiatrists. A total of 436 subjects were selected randomly according to MMSE-K scores, and cases were confirmed as having either Alzheimer's or vascular dementia.

RESULTS

The adjusted prevalence of dementia was estimated at 9.5%. The prevalence of total dementia was 8.8% for men and 9.9% for women. The prevalence of Alzheimer's disease was 3.2% for men and 5.3% for women and that of vascular dementia 3.1% and 2.1%, respectively. Age-standardized prevalence of Alzheimer's disease was 4.5%, whereas that of vascular dementia was 2.5%. Using DSM-III-R criteria to stratify dementia patients according to severity showed the prevalence of mild, moderate, and severe Alzheimer's disease was 3.4%, 0.7%, and 0.5%, respectively.

CONCLUSION

These results showed that the prevalence of dementia in Korea was similar to its presence in Western countries but different from that previously reported in other Asian countries, e.g., China and Japan.

Microsatellite instability in young patients with colorectal cancer

Genetic instability is closely correlated to the pathogenesis of hereditary non-polyposis colon cancer (HNPCC), which is clinically characterized by a family history and early onset. To investigate the role of genetic instability in young patients with colorectal cancer (CRC), 22 CRC patients, who were aged younger than 30 at the time of diagnosis, were studied. Patients with familial adenomatous polyposis were excluded. Among the 22 cases, seven were identified as microsatellite instability positive (MI+), and more than five microsatellite markers among the 15 tested markers showed an additional band pattern in the tumor tissue. None of the remaining 15 cases showed instability in any microsatellite marker. Two of seven MI+ cases were classic HNPCC. While all MI+ cases had one or no metastatic lymph node, 53.3% of MI- cases showed metastasis in two or more regional lymph nodes. Allelic deletion of the 17p12-13 chromosome around the p53 locus occurred in 16.7% of MI+ cases, and 80.0% of MI- cases showed loss of heterozygosity at that locus. hMSH2 Protein expression, assessed by immunohistochemistry, was absent in two cases, both of which were MI+. When we tested two to four sites of MI+ tumors, transforming growth factor beta receptor type II was mutated in a homogeneous pattern in five MI+ cases. In addition, frame-shift mutations of BAX, insulin-like growth factor II receptor, hMSH3 and hMSH6 were found in three cases, five cases, five cases and one case, respectively. In contrast to the consistent mutation of the transforming growth factor-beta receptor type II gene, mutations of other genes varied in different portions of the tumors.

Folate depletion impairs DNA excision repair in the colon of the rat

BACKGROUND/AIMS

Diminished folate status appears to promote colonic carcinogenesis by, as of yet, undefined mechanisms. Impaired DNA repair plays a significant role in the evolution of many colon cancers. Since folate is essential for the de novo synthesis of nucleotides and since folate depletion has previously been associated with excessive DNA strand breaks, it was hypothesised that folate depletion may impair DNA repair. Studies were therefore performed to examine whether folate depletion affects the two major categories of DNA repair.

METHODS

Study 1: eight weanling male Sprague-Dawley rats were fed on diets containing either 0 or 8 mg folate/kg diet with 1% succinylsulphathiazole for four weeks. After viable colonocytes had been harvested, DNA excision repair was evaluated by a single cell gel electrophoresis assay. Study 2: eighteen animals were fed on similar diets for five weeks. Also in study 2, 18 additional rats were fed on the same defined diet without succinylsulphathiazole for 15 weeks. Weekly injections with the procarcinogen, 1,2-dimethylhydrazine (20 mg base/kg), were administered to the latter group of animals. Five microsatellite loci from different chromosomes were investigated for instability in hepatic and colonic DNA.

RESULTS

In study 1, a significantly retarded rate of DNA excision repair was observed in the folate deficient colonocytes compared with controls (p < 0.05). In study 2, there was no evidence of instability at the five microsatellite loci associated with either short or long term folate depletion.

CONCLUSIONS

Folate deficiency impairs DNA excision repair in rat colonic mucosa; a similar degree of deficiency, even when administered in conjunction with a colonic carcinogen, did not produce evidence of a widespread defect in mismatch repair.

Small intestinal stromal tumors: a clinicopathologic study of 31 tumors

The biologic behavior of gastrointestinal stromal tumors is difficult to predict, and they can be best studied in a site-specific fashion. The aims of this study are to analyze the clinicopathologic parameters and assess the prognostic value of p53 (DO-7) and Ki-67 (MIB-1) immunoreactivities in small intestinal stromal tumors (SIST). The histopathologic features of 31 SIST were assessed and categorized into two groups as follows. Group A (clinically aggressive) in which death due to tumor, metastasis, recurrence or relapsed melena were seen (n = 15) and group B (clinically benign; n = 16). For both groups, the period of follow-up was 30-144 months. p53 overexpression was observed in four tumors (31%) in group A, and in none in group B. For groups A and B, the mean Ki-67 index was 16.8 +/- 12.5 and 8.4 +/- 12.6, respectively. Statistical analysis revealed that the significant predictors of malignancy were high cellularity (odds ratio (OR) = 999; 95% confidence interval (CI) = 0-999); p53 overexpression (OR = 999; CI = 0-999); size of tumor > or = 5 cm (OR = 18.0; CI = 1.9-171.9); > or = 5 mitoses/50 high-power fields (HPF) (OR = 17.1; CI = 1.8-165.9); pleomorphism (OR = 17.1; CI = 1.8-165.9); and necrosis (OR = 11.9; CI = 2.2-65.1; P < 0.05). High Ki-67 index (> or = 8.4) had a marginal impact on risk (OR = 4.1; CI = 0.8-20.2; P = 0.08). In conclusion, high cellularity, p53 overexpression, size of tumor > or = 5 cm, > or = 5 mitoses/50 HPF, pleomorphism and necrosis are important parameters for the prediction of malignancy in SIST.

Supraspinal involvement in the production of mechanical allodynia by spinal nerve injury in rats

This study examined whether or not the production of mechanical allodynia in a rat model of neuropathic pain required an involvement of supraspinal site(s). To this aim, we assessed the effect of spinal cord section at the L1 segment level on the mechanical allodynia sign (i.e. tail flick/twitch response), which was elicited by innocuous von Frey hair stimulation of the tail after unilateral transection of the tail-innervating nerve superior caudal trunk (SCT) at the level between the S3 and S4 spinal nerves. Cord transection or hemisection of the cord ipsilateral to the injured SCT drastically (though not completely) blocked the behavioral sign of mechanical allodynia (leaving noxious pinprick-elicited tail withdrawal reflex intact), whereas sham section or contralateral hemisection of the cord was without effect. These results suggest that the generation of mechanical allodynia following partial peripheral nerve injury involves transmission of the triggering sensory signal to a site(s) rostral to the L1 segment via an ipsilateral pathway(s).

Lambert-Eaton syndrome antibodies inhibit acetylcholine release and P/Q-type Ca2+ channels in electric ray nerve endings

1. The types of voltage-dependent calcium channels (VDCCs) present in the cholinergic terminals isolated from the electric organ of the ray, Narke japonica, were characterized on the basis of their pharmacological sensitivity to specific antagonists. Inhibition of these channel types by autoantibodies from patients with the Lambert-Eaton syndrome (LES) was then studied to determine the specificity of the pathogenic IgG. 2. In normal untreated synaptosomal preparations, maximal doses of N- and P and/or Q-type Ca2+ channel antagonists, omega-conotoxin GVIA and omega-agatoxin IVA, inhibited depolarization-evoked ACh release by 47 % and 43 %, respectively. Calciseptine, an L-type VDCC antagonist, caused a 20 % reduction in the release. This indicates that the exocytotic release process is predominantly mediated by N- and P/Q-type VDCCs. 3. LES IgG or sera caused an inhibition of ACh release by 39-45 % in comparison with the control antibody-treated preparations. The ionomycin-induced ACh release, however, was not altered by the antibodies. Additionally, the same LES antibodies inhibited whole-cell calcium currents (ICa) in bovine adrenal chromaffin cells. Thus, the pathogenic antibodies exert their action on VDCCs present in the synaptosomes. 4. The efficacy of three Ca2+ channel antagonists in blocking ACh release was determined in preparations pretreated with LES IgG. omega-Agatoxin IVA produced only an additional 3-5 % reduction in release beyond that obtained with LES antibodies. Despite the pretreatment with LES IgG, omega-conotoxin GVIA and calciseptine inhibited the release to nearly their control levels. 5. These results indicate that LES antibodies mainly downregulate P/Q-type Ca2+ channels which contribute to presynaptic transmitter release from the cholinergic nerve terminals of electric organ. 6. The present findings are consistent with the hypothesis that P/Q-type VDCCs at the neuromuscular junction are the target of LES antibodies and that their inhibition by the antibodies produces the characteristic neuromuscular defect in this disease.

[Laparoscopic surgery for early gastric cancer--its advantages and pitfalls]

We have successfully established two different laparoscopic procedures for early gastric cancer since March 1992, which are laparoscopic wedge resection of the stomach using a lesion-lifting method and laparoscopic intragastric mucosal resection. The indication is as follows; (A) mucosal cancer, (B) < 25 mm, if the lesion is elevated type, (C) < 15 mm and Ul (-), if the lesion is depressive type. The advantages of these methods are; 1) minimally invasiveness, 2) sufficient surgical margin, 3) feasibility of detailed histology, 4) feasivility of perigastric lymph node dissection. In contrast, there are several problems to be solved, which are; 1) preoperative diagnostic accuracy of the depth of cancer invasion, 2) possibility of reoperation because of sm invasion or lymphatic or venous invasion in final histology, 3) possibility of postoperative stenosis after laparoscopic intragastric mucosal resection for the lesion near the cardia, 4) incidence of metachronous multiple gastric cancer. In conclusion, if the indication is properly selected, these laparoscopic procedures are curative and minimally invasive treatment for early gastric cancer.

Na+/H+ exchange inhibition improves post-transplant myocardial compliance in 4-hour stored donor hearts

Na+/H+ exchange inhibitors have cardioprotective properties. The effects of the new Na+/H+ exchange inhibitor, HOE642 on myocardial function were assessed after transplantation of canine brain-dead and non-brain-dead donor hearts preserved for 4 h. Four groups were studied: brain-dead donors; non-brain-dead donors; brain-dead donors and recipients treated with HOE642 (2 mg/kg); and treated non brain-dead donors and recipients. Donor hearts were stored in NIH2. At the end of 60 min reperfusion after transplantation, pressure-volume curves were constructed. Biopsies were analysed histologically and ultrastructurally. Afterwards, weaning from cardiopulmonary bypass was accomplished. HOE642 improved compliance in hearts from both brain-dead and non-brain-dead donors. No differences in myocardial water content nor in myocardial performance were detected. No irreversible damage was seen ultrastructurally. It is concluded that myocardial compliance after transplantation was improved by administration of HOE642. The use of this inhibitor might improve the current myocardial preservation technique for transplantation.

Amyotrophic lateral sclerosis: serum factors enhance spontaneous and evoked transmitter release at the neuromuscular junction

Sera from 30 patients with sporadic amyotrophic lateral sclerosis (ALS) were tested to determine their effects at the neuromuscular junction. Spontaneous transmitter release was significantly increased, as evidenced by a 151% increase in MEPP frequency, by sera from 16 ALS patients. In addition, 16 patients' sera elevated EEP quantal content by an average of 89%. Eleven sera produced both effects. There was no consistent change in MEPP amplitude or time course, indicating the absence of a humoral effect on postjunctional ACh receptors or endplate membrane function. These results suggest that a portion of the sporadic ALS patient population possess serum factors that can alter presynaptic function of the motor nerve terminal. Evidence from the present experiments indicates that alterations at the neuromuscular junction are a result of a combination of increased Ca2+ influx into the cell and an independent increase in intracellular calcium concentration.

p53 mutation and overexpression in hepatocellular carcinoma and dysplastic nodules in the liver

In hepatocarcinogenesis, both de novo and multistep pathways have been suggested and in the latter a dysplastic nodule is the proposed precancerous lesion. In this study, we tried to ascertain whether or not the p53 gene is altered in low-grade/high-grade dysplastic nodules (LDN/HDN) and to determine the role of p53 alteration in multistep hepatocarcinogenesis. Eight hepatocellular carcinomas (HCCs), 9 HDNs, 17 LDNs and 25 cirrhotic nodules (LCs) were examined by polymerase chain reaction-single strand conformation polymorphism/direct sequencing and immunohistochemical staining for p53. Four of the 8 HCCs (50%) revealed p53 overexpression and 2 (25%) had missense mutations. Four of the 9 HDNs (44%) showed weak and/or focal p53 overexpression but none had mutation in the exons examined. Neither p53 overexpression nor mutation was found in 17 LDNs and 25 LCs. These results suggest that p53 mutation might be an unusual event in precancerous lesions of multistep hepatocarcinogenesis (DN-HCC sequence) and may play a less crucial part than in colorectal carcinogenesis.

Alpha-fetoprotein-producing gastric carcinoma presenting focal hepatoid differentiation in metastatic lymph nodes

Hepatoid adenocarcinoma (HA) is a rare variant of adenocarcinoma of the stomach, which is clinically characterized by increased level of serum alpha-fetoprotein (AFP) and poor prognosis. Microscopic findings include both adenocarcinomatous and hepatoid elements. A case of gastric adenocarcinoma with focal hepatoid differentiation confined within the metastatic lymph nodes occurred in a 55-year-old woman, who developed an advanced gastric carcinoma composed entirely of a typical papillo-tubular adenocarcinoma. Metastatic tumors were present in 8 of 13 perigastric lymph nodes, and 3 of these showed medullary and trabecular tumour growth reminiscent of hepatocellular carcinoma with immunohistochemical positivity for AFP. Preoperative serum AFP was 630 ng/ml and dropped to 76 ng/ml 2 weeks after the operation. Microscopic and immunohistochemical studies on the entire primary tumour tissue failed to demonstrate a focus of hepatoid or an AFP-positive area. This suggests that elevation of serum AFP may be reflected by focal hepatoid differentiation only in the metastatic lymph nodes, requiring extensive evaluation of the metastatic tumour in regional lymph nodes in the case of AFP-producing gastric carcinoma.

Short-chain fatty acids in ulcerative colitis

Short-chain fatty acids (SCFA), a by-product of anaerobic fermentation of undigested carbohydrates within the colon, are an important energy source for colonic epithelial cells. It has been proposed that ulcerative colitis, a chronic inflammatory condition of the colon, may result from a metabolic defect in SCFA oxidation in the colon and that this defect may be corrected by supraphysiologic luminal levels of SCFA in the colon. Clinical trials published to date suggest that topical SCFA provide an effective primary and/or adjunctive treatment in patients with mild to moderate distal ulcerative colitis at substantial cost savings and without significant side effects.

Promoter region of the Drosophila melanogaster norpA gene

We have sequenced the 5'-flanking region of the Drosophila melanogaster norpA gene and characterized its promoter. The potential promoter region, which was deduced from the determination of the transcription start point (tsp), lacks a distinct TATA box sequence. Deletion analysis of the promoter region suggests that the minimal promoter necessary for efficient expression of the gene is located between -138 (PstI) and +278 relative to the tsp. Within this minimal promoter region, at least two downstream regulatory elements responsible for the stimulation of gene expression seem to exist in the DNA fragments between +44 and +121 and between +214 and +278. Among these, the DNA fragment between +44 and +121 affects promoter activity more dramatically (about 6-7 fold). This DNA fragment contains the consensus promoter element previously reported to be important for photoreceptor cell-specific expression, and this promoter element seems to be working in the norpA gene expression.

Risk factors for the development of NIDDM in Yonchon County, Korea

OBJECTIVE

To determine the risk factors for the development of NIDDM in Yonchon County of Korea.

RESEARCH DESIGN AND METHODS

We studied 1,193 Korean nondiabetic subjects at baseline who participated in a 2-year follow-up study on diabetes in Yonchon County. A 75-g oral glucose tolerance test was performed 2 years after the baseline examination. Age, sex, and anthropometric and metabolic characteristics at baseline were analyzed simultaneously as potential predictors of conversion to NIDDM. We also designed a nested case-control study to determine the role of hyperinsulinemia and/or hyperproinsulinemia in the conversion to NIDDM in patients with newly developed diabetes and control subjects matched for age, sex, BMI, and waist-to-hip-ratio.

RESULTS

At 2 years, 67 subjects developed diabetes, as defined by World Health Organization criteria. The age-adjusted incidence was significantly higher in men (6.4%) than in women (3.0%), and the incidence increased as age increased in both sexes. Multiple logistic regression analysis revealed age, male sex, and fasting and 2-h glucose levels to be significant risk factors for the development of NIDDM, whereas waist-to-hip ratio and BMI were not. In a nested case-control study, baseline proinsulin but not insulin levels were significantly higher in subjects who progressed to NIDDM than in those who did not.

CONCLUSIONS

In the Korean population, beta-cell dysfunction, as measured by high proinsulin levels, seems to be associated with subsequent development of NIDDM, whereas regional and general obesity and fasting insulin levels, which may be a surrogate for insulin resistance, were not.

Conservative management of superior mesenteric and portal vein thrombosis associated with protein C and S deficiency. Case report

Protein C and S, vitamin K-dependent proteins, are blood coagulation inhibitors. Their deficiency causes systemic thrombosis. A 35-year-old man who developed superior mesenteric venous thrombosis and portal vein thrombosis showed markedly decreased protein C and S levels. The therapeutic modality of this thrombosis associated with protein C and S deficiency is still debated. We treated this patient with systemic anticoagulation and long term total parenteral nutrition without surgical intervention.

Activity-dependent conduction velocity changes of A(delta) fibers in a rat model of neuropathy

Activity-dependent changes of conduction velocity (CV) and conduction block in single A(delta) fibers of primary afferent neurons were characterized in a rat model of neuropathy (NP). Injured dorsal root (DR) fiber in NP rats exhibited profoundly greater decreases of CV following impulse activity than did DR fiber in normal rats. Activity-dependent conduction block was absent up to 100 Hz of activity rate in DR fiber of NP rats, but was present above 25 Hz in normal rats. Profiles of activity dependence in sciatic fibers were similar in both NP and normal rats. These results suggest that nerve injury may alter activity-dependent hypoexcitability of A(delta) DR fibers. Furthermore, this excitability change may be responsible for the elevated pain perception in neuropathy.

Effect of suramin on differentiation of human stomach cancer cell lines

This study was designed to demonstrate that differentiation of stomach cancer cells can be modified by microenvironmental change and to look for a method inducing or promoting tumor cell differentiation. To evaluate the biomorphological characterization of tumor cell differentiation in suramin-containing in vitro culture of human stomach cancer cell lines, inverted phase-contrast microscopic examination, analysis of growth curves and BrdU-positive S-phase fraction, immunocytochemical study, radioimmunoassay for CEA, transmission electron microscopic examination, DNA flow cytometry, and heterotransplantation in SCID mice were performed. Suramin inhibited tumor cell growth. Development of intracytoplasmic lumina and intercellular lumina was noted in suramin-containing culture with formation of numerous microvilli and frequent desmosomes. The amount of CEA released by a cell was increased in suramin-containing culture. Suramin inhibited heterotransplantation, and a transplant from suramin-containing culture revealed a much higher degree of differentiation than that from suramin-absent culture. Suramin induced no change in DNA ploidy pattern. Elimination of suramin from the culture medium did not reverse the tumor cell differentiation. Each stomach cancer cell line showed a different degree of responsiveness to suramin. In conclusion, this study shows that suramin inhibits growth of SNU-5 and SNU-16 cells and that suramin induces differentiation of SNU-16 cells.