Transforming growth factor beta type II receptor gene mutations in adenomas from hereditary nonpolyposis colorectal cancer

BACKGROUND & AIMS

Germline mutations of DNA mismatch repair genes are responsible for cancer susceptibility in hereditary nonpolyposis colorectal cancer (HNPCC) kindreds. Transforming growth factor beta type II receptor (TGF-beta RII) has been found to be somatically altered in HNPCC. The aim of this study was to clarify further the role of TGF-beta RII alterations in HNPCC tumorigenesis, particularly in adenomas.

METHODS

Fourteen adenoma specimens and 13 cancer specimens from 10 patients with HNPCC were screened for mutations in the short repeated sequences of the TGF-beta RII gene by polymerase chain reaction-single-strand conformation polymorphism. Mismatch repair genes, replication errors, and c-K-ras 2 were also analyzed in HNPCC tumors.

RESULTS

Alterations of the TGF-beta RII gene at the short poly(A) repeat were found in 8 (57%) adenoma specimens and 11 (85%) cancer specimens. They were found at an earlier stage of adenomas. Two adenoma specimens showed two-hit inactivation of mismatch repair genes. Replication errors were detectable in 13 (93%) adenoma specimens. Mutations in c-K-ras 2 codon 12 were detected at a 50% frequency in adenoma specimens.

CONCLUSIONS

These data indicate a strong association between TGF-beta RII gene alterations and adenoma-carcinoma progression in HNPCC.

Predictability of extracranial/intracranial bypass function: a retrospective study of patients with occlusive cerebrovascular disease

OBJECTIVE

When the efficacy of extracranial/intracranial bypass surgery is discussed, can we include the patients with extensive collateral circulation through the bypass and those with poor collateral circulation in the same group? The bypass function should be determined not by the patency of the bypass but by the extent of collateral circulation through the bypass. We retrospectively analyzed our patients to determine whether the extent of bypass flow can be predicted from the results of preoperative studies.

METHODS

In 51 hemispheres of 44 consecutive patients who underwent extracranial/intracranial bypass surgery, correlation between the extent of bypass flow and the preoperative results of angiographic and stimulated cerebral blood flow studies were investigated.

RESULTS

The bypass function is highly predictable with the aid of preoperative studies. In 11 hemispheres that showed both retrograde spontaneous circulation via leptomeningeal anastomoses and decreased reactivity to acetazolamide of cerebral blood flow in an area distal to the arterial lesion, collateral circulation through the bypass developed well and reactivity to acetazolamide improved. In all of 13 hemispheres that showed normal reactivity to acetazolamide, the bypass was patent but the collateral circulation did not develop well. In only 4 of 24 hemispheres with spontaneous antegrade circulation distal to the lesion was there satisfactory collateral circulation through the bypass.

CONCLUSION

Our results indicate that improvement of the hemodynamic status by bypass surgery should be expected only in patients with both spontaneously developed leptomeningeal anastomoses and decreased reactivity to acetazolamide.

Preventive effect of 1-(2-tetrahydrofuryl)-5-fluorouracil in combination with uracil on colonic carcinogenesis induced by 1,2-dimethylhydrazine in rats

Thymidylate synthetase (TS) and thymidine kinase (TK) are key enzymes in de novo and salvage pathways for pyrimidine nucleotide synthesis, respectively. A high incidence of colorectal adenocarcinomas with varied grades of cell differentiation can be induced by 1,2-dimethylhydrazine (DMH) in rats. The marked increases of TS and TK activities were found in the poorly and well-differentiated adenocarcinomas of the colon, respectively. Oral administration of 1-(2-tetrahydrofuryl)-5-fluorouracil in combination with uracil (UFT) markedly reduced the number and accumulated area of colonic carcinomas, and TS activity in the poorly differentiated adenocarcinomas. A potential balance between the de novo and the salvage pathways for pyrimidine nucleotide synthesis was suggested to be related with the histopathological grades of cell differentiation. Suppression of colonic TS activity by UFT administration reduced the colonic carcinogenesis and the potency of the poorly differentiated adenocarcinomas of the colon.

Mutations of the transforming growth factor-beta type II receptor gene are strongly related to sporadic proximal colon carcinomas with microsatellite instability

BACKGROUND

Mutations of the transforming growth factor-beta type II receptor gene (TGF-beta RII) have been found in several replication error-positive sporadic colorectal carcinomas and hereditary nonpolyposis colorectal carcinoma cell lines. The aim of this study was to clarify the role of TGF-beta RII in sporadic colorectal carcinogenesis.

METHODS

The authors screened for mutations at simple repeated sequences in the TGF-beta RII gene by polymerase chain reaction-single strand conformation polymorphism. They also examined genomic instability, using five microsatellite DNA markers in 69 sporadic colorectal carcinomas. When the carcinomas exhibited the TGF-beta RII mutations, the authors screened further for mutations in two DNA mismatch repair genes, hMSH2 and hMLH1.

RESULTS

Seven of the 69 cancers (10%) showed one or two A deletions in TGF-beta RII and resultant frameshift mutations in nucleotide positions 709-718 containing a (A) 10 repeated sequence; but none of these appeared in the corresponding normal DNA, indicating a somatic mutation. All of the seven cancers were located in the proximal colon; there were none in the distal colon (P < 0.01). On the other hand, 22 of the 69 carcinomas (32%) showed the replication error-positive phenotype. The frequency of replication errors in proximal colon carcinomas was higher than that in distal colon carcinomas (P < 0.05). All 7 cancers with TGF-beta RII mutations showed replication errors. One of them revealed a nonsense mutation at codon 413, and 1 revealed a loss of heterozygosity in hMSH2.

CONCLUSIONS

These data indicate that mutations of TGF-beta RII are strongly related to proximal colon carcinomas with microsatellite instability and that the mechanism of carcinogenesis in some proximal colon carcinomas is similar to that in hereditary nonpolyposis colorectal carcinoma.

Vasoreactive effect of acetazolamide as a function of time with sequential PET 15O-water measurement

The accurate assessment of vascular flow reserve is crucial for the evaluation of risk among patients with cerebrovascular disease. In six patients with unilateral occlusion of the internal carotid artery and one patient with unilateral occlusion of the middle cerebral artery (mean +/- S.D. age = 68 +/- 3 years), we measured cerebral blood flow (CBF) after the administration of 940 MBq 15O-water using a remotely controlled power injector. Studies were performed at rest, after 10 min, and then 10, 20 and 30 min after the administration of 1 mg acetazolamide to evaluate the vasoreactive effect, as reflected by an increase in CBF. Sixteen regions of interest (ROIs) were drawn over the CBF images. These ROIs were as follows in each hemisphere: Area I, four areas in the cortical middle cerebral arterial territory (superior frontal, frontal, temporal and parietal areas); Area II, four areas of the deep middle cerebral and vertebral arterial territory (occipital area, basal ganglia, thalamus and cerebellum). Taking normalized resting CBF to be 100%, the mean CBF measured 10, 20 and 30 min post-injection using sequential positron emission tomography was as follows: Area I, 141.4 +/- 16.3, 127.7 +/- 15.3 and 128.2 +/- 17.4% for non-occluded sites and 116.3 +/- 22.8, 112.7 +/- 16.4 and 114.9 +/- 17.1% for occluded sites; Area II, 143.4 +/- 14.5, 126.2 +/- 10.4 and 125.0 +/- 12.9% for non-occluded sites and 141.9 +/- 28.9, 126.0 +/- 20.5 and 124.1 +/- 17.1% for occluded sites. A significant difference in mean CBF was noted between the non-occluded and occluded sites in Area I, the most marked difference of 25.1% being observed 10 min after the administration of the acetazolamide. We conclude that for an accurate assessment of vascular reserve in patients with cerebrovascular disease, CBF should be measured 10 min post-administration of the acetazolamide.

Repeat coronary angioplasty as the treatment of choice for restenosis

A prospective study was performed to determine whether multiple repeat coronary angioplasty can achieve final lesion patency after restenosis. Between 1983 and 1992, 1455 lesions (excluding acute myocardial infarction or total occlusion) were successfully dilated for the first time. Only 941 (68%) of the 1385 lesions followed up showed improved coronary flow (< or = 70% stenosis) after the first procedure. However, 1248 (93%) of 1345 lesions showed improved coronary flow after angioplasty had been repeated as many as three times, and 1268 (94%) of 1345 did so after as many as six procedures. Only 23 (1.6%) lesions required four or more procedures, and 20 of them showed final patency. These findings indicate that repeat angioplasty can be used as a reasonable treatment strategy for restenosis.

Airway hyperresponsiveness to acetylcholine induced by aerosolized arachidonic acid metabolites in guinea-pigs

BACKGROUND AND OBJECTIVE

To investigate the role of arachidonic acid (AA) metabolites in airway hypersensitivity.

METHOD

We studied the change in airway responsiveness to acetylcholine (ACh) after inhalation of some AA metabolites in guinea-pigs.

RESULTS

Exposure to prostaglandin (PG) D2, thromboxane (TX) A2 mimetic U-46619, leukotriene (LT) D4 or LTE4 at concentrations which did not influence bronchial tone and blood pressure dose-dependently caused airway hyperresponsiveness. However, the change was not observed after challenge with a high concentration of PGF2 alpha. Furthermore, PGD2 and U-46619 induced an acute and short-lived increase in responsiveness, while LTD4 and LTE4 induced a slow-onset and longer-lived increase. In the tachyphylaxis study, although the tachyphylaxis for airway hyperresponsiveness provoked by PGD2 and U-46619 was not observed, airway hyperresponsiveness induced by the second LTD4 tended to decrease, and the second LTE4-induced airway hyperresponsiveness obviously diminished. In the study using antagonists and inhibitors, TX-receptor antagonist BM-13177 inhibited PGD2- and U-46619-, but not LTD4- and LTE4-induced airway hyperresponsiveness. TX synthase inhibitor OKY-046 had no effect on PGD2-, U-46619- and LTD4-induced airway hyperresponsiveness, while LTE4-induced airway hyperresponsiveness tended to be inhibited by these inhibitors. However, the LT-receptor antagonist ONO-1078 inhibited both LTD4- and LTE4-, but not PGD2- or U-46619-induced airway hyperresponsiveness. 5-lipoxygenase inhibitor AA-861 tended to prevent LTE4-induced airway hyperresponsiveness, but had no effect on PGD2-, U-46619- and LTD4-induced enhanced responses.

CONCLUSION

These findings indicate that the local existence of PGD2, TXA2, LTD4 and LTE4 in the guinea-pig airway may act as an airway hyperresponsiveness-inducing factor rather than as a bronchoconstrictor. In addition, PGD2/U-46619 may stimulate the TX receptor to induce an acute and short-lived airway hyperresponsiveness, and LTD4 and LTE4, which may involve secondary mediator release, may act at the LT receptor to induce a slow-onset and longer-lived airway hyperresponsiveness, which may be associated with the induction, the development and the long duration of airway hyperreactivity.

Molecular nature of colon tumors in hereditary nonpolyposis colon cancer, familial polyposis, and sporadic colon cancer

BACKGROUND & AIMS

Microsatellite instability (replication error [RER]) is a characteristic of tumors in hereditary nonpolyposis colon cancer (HNPCC), but the mechanism of HNPCC carcinogenesis is not yet understood. To clarify the nature of HNPCC tumors, RER and genetic changes were compared between HNPCC and non-HNPCC tumors.

METHODS

RER and genetic changes were analyzed in 21 HNPCC, 389 familial adenomatous polyposis, and 206 sporadic tumors using polymerase chain reaction, single-strand conformation polymorphism, sequencing, and Southern hybridization. RESULTS. in HNPCC, 95% tumors at all stages showed RER positivity (altered loci, 4.3 of 5). In familial adenomatous polyposis and sporadic tumors, RER positivity (1.7 of 5) was 3% in adenoma and intramucosal carcinoma, 13%-24% in invasive carcinoma, and 35% in carcinoma metastasized to liver. Fifty percent of RER-positive HNPCC tumors had both germline and somatic mutations of hMSH2 or hMLH1 gene, whereas 6% of RER-positive non-HNPCC had somatic mutation. APC, p53, and K-ras-2 mutations and loss of heterozygosity of tumor-suppressor genes were significantly less frequent (P = 0.03 to 0.0006) but transforming growth factor beta type II receptor mutation was significantly more frequent (P = 0.000001) in HNPCC than in non-HNPCC.

CONCLUSIONS

RER positivity occurs from an early stage of carcinogenesis in HNPCC but in later stages in non-HNPCC. Most HNPCC tumors may develop through different genetic changes from those in the adenoma-carcinoma sequence, although a certain percentage develops through APC mutation.

Ampullary carcinoma in familial adenomatous polyposis: report of a case

We report the case of a 48-year-old man with familial adenomatous polyposis (FAP) who was found to have ampullary carcinoma 6 years after undergoing total colectomy. The patient was examined periodically after colorectal surgery except for duodenoendoscopy because he had also previously undergone distal gastrectomy with gastrojejunal anastomosis for a duodenal ulcer at 27 years of age. An ampullary lesion was suspected on blood chemistry and detected by computed tomography scan and ultrasonography although the patient showed no clinical symptoms. A pancreatoduodenectomy was performed and the histological examination revealed well-differentiated adenocarcinoma with no metastasis to the regional lymphnodes. Long-term periodic surveillance of the upper gastrointestinal tract including the papilla of Vater is therefore important for FAP patients who have undergone prophylactic colectomy.

The relevance of hemodynamic factors to perioperative ischemic complications in childhood moyamoya disease

Of 124 children younger than 15 years who underwent surgery for moyamoya disease, 21 (16.9%) experienced perioperative ischemic complications that could not be unequivocally attributed to the surgery. Eleven of the 21 patients experienced infarctions, and 10 experienced reversible ischemic neurological deficits without new lesions, as revealed by computed tomographic scans. An examination of the patients' perioperative clinical and laboratory data revealed that the mean values of intra- and postoperative minimum arterial carbon dioxide pressure, maximum arterial carbon dioxide pressure, and mean arterial pressure were similar in patients with and without ischemic complications. However, in patients with perioperative complications, the incidence of preoperative transient ischemic attacks (TIAs) and intra- and postoperative hypercapnia (maximum arterial carbon dioxide pressure > 45 mm Hg) was significantly higher. In addition, 7 of the 11 perioperative infarctions occurred in patients with frequent preoperative TIAs and intra- and postoperative hypercapnia. Cerebral blood flow studies with preoperative acetazolamide loading showed that the new infarctions were located in areas in which the cerebral blood flow had been compromised. Our results suggest that the occurrence of frequent preoperative TIA is an important indicator of the instability of the cerebral hemodynamics and of the risk of perioperative ischemic complications. To prevent these complications, preoperative management aimed at stabilizing the hemodynamic status is very important. Children who have moyamoya disease and who experience frequent preoperative TIAs are at risk for ischemic brain damage caused by hypercapnia as well as hypocapnia and hypotension. The establishment and maintenance of normocapnia with normotension are highly desirable for the perioperative management of moyamoya disease in children.

Frequent microsatellite instabilities and analyses of the related genes in familial gastric cancers

Microsatellite instability or replication error seems to be related to defective DNA mismatch repair genes, such as hMSH2, hMLH1, hPMS1 and hPMS2, which have been identified as causative genes of hereditary nonpolyposis colorectal cancers (HNPCC). Recently, it was reported that mutations at the simple repeated sequences in the transforming growth factor-beta type II receptor (TGF-beta RII) gene occurred in replication error-positive colorectal cancers. To determine genetic alterations in familial gastric cancers (FGC, we examined replication error using eight microsatellite DNA markers, and screened mutations in the hMSH2, hMLH1 and TGF-beta RII genes in six cases from four FGC kindreds. Moreover, hMTH1, a human homolog of the bacterial mutT gene, was also screened. Four of six (67%) cancers showed the replication error-positive phenotype, indicating that microsatellite instability is highly associated with not only HNPCC, but also FGC. No germline mutation was found in the whole coding sequences of hMSH2 and hMTH1, or in the conservative regions of hMLH1 in any patient, while one cancer DNA showed a somatic mutation at codon 682 (threonine to alanine) in hMSH2. No alteration was found at the small repeated sequences in TGF-beta RII in FGC tumor DNA. These results indicate that the carcinogenetic process of FGC may be different from that of HNPCC.

p300 gene alterations in colorectal and gastric carcinomas

Colorectal tumors frequently have loss of heterozygosity on chromosome 22q, suggesting that inactivation of tumor suppressor gene(s) on 22q participates in the tumor development. Neurofibromatosis 2 (NF2) gene and E1A binding protein p300 gene, recently identified on 22q, are thought to be candidates for tumor suppressor genes. In this study, mutation of the NF2 gene in 59 colorectal carcinomas, and mutation of the p300 gene in 27 colorectal and two gastric carcinomas, were analysed using PCR-SSCP, RT-PCR-SSCP and direct sequencing methods. Missense mutations of p300 gene were detected in a colorectal carcinoma, and in a gastric carcinoma, though no mutation of NF2 gene was detected. Both p300 mutations were somatic and coupled to deletion of the second allele of the gene, which suggests inactivation of the p300 gene, in these carcinomas. The mutations are located within the Cys/His-rich regions, which are assumed to play important roles in the function of p300. These are the first cases in which p300 gene has been found to be altered in both alleles, suggesting that inactivation of the p300 gene may be involved in the development of carcinomas, and that this gene may be the target of loss of 22q in carcinomas of the digestive tract.

Loss or somatic mutations of hMSH2 occur in hereditary nonpolyposis colorectal cancers with hMSH2 germline mutations

Hereditary nonpolyposis colorectal cancer (HNPCC) is a major cancer susceptibility syndrome known to be caused by the inheritance of mutations in DNA mismatch repair genes, such as hMSH2, hMLH1, hPMS1 and hPMS2. To investigate the role of genetic alterations of hMSH2 in HNPCC tumorigenesis, we analyzed 36 Japanese HNPCC kindreds as to hMSH2 germline mutations. Moreover, we also examined somatic mutations of hMSH2 or loss of heterozygosity at or near the hMSH2 locus in the tumors from the hMSH2-related kindreds. Germline mutations were detected in five HNPCC kindreds (5/36, 14%). Among them, three were nonsense mutations, one was a frameshift mutation and the other was a mutation in an intron where the mutation affected splicing. Loss of heterozygosity in four and somatic mutations in one were detected among the eight tumors with hMSH2 germline mutations. All these alterations were only detected in genomic instability(+) tumors, i.e., not in genomic instability(-) ones, indicating that mutations of hMSH2 were responsible for at least some of the tumors with genomic instability. These data establish a basis for the presymptomatic diagnosis of HNPCC patients, and constitute further evidence that both DNA mismatch repair genes and tumor suppressor genes may share the same requirement, i.e., two hits are necessary to inactivate the gene function.

Tricuspid valve endocarditis with large vegetations in a non-drug addict without underlying cardiac disease

We report a case of gamma-streptococcal tricuspid valve endocarditis in a patient with no history of intravenous drug abuse. Echocardiography revealed large vegetations on the anterior and septal cusps. The patient had persistent fever and recurrent septic pulmonary embolism despite prolonged antibiotic therapy. However tricuspid valve replacement was successful.

Germ line mutations of hMSH2 and hMLH1 genes in Japanese families with hereditary nonpolyposis colorectal cancer (HNPCC): usefulness of DNA analysis for screening and diagnosis of HNPCC patients

Mutations in hMSH2 and hMLH1 genes were analyzed in patients from 11 Japanese families that had been diagnosed as carrying hereditary nonpolyposis colorectal cancer (HNPCC) by clinical examination. Germ line mutations of hMSH2 gene were identified in 5 independent families in which colorectal (87% of patients), endometrial (30%), ovarian (17%), gastric (14%), and other cancers existed. Five mutations detected between codons 136 and 811 included single-base substitutions (C-->T and T-->G), a T deletion, and an A insertion, all of which produced stop codons resulting in truncated proteins, and an A-->T substitution at splice donor site of exon 5 which resulted in deletion of this exon. Moreover, one HNPCC family was presumed to have germ line mutation of hMSH2 gene because a somatic mutation of hMSH2 gene was detected in a cancer from a patient in this family. In addition to these 11 families already diagnosed with HNPCC, 3 new families with germ line mutations of hMSH2 gene and hMLH1 gene were found through analysis of DNA from patients who had multiple cancers with alteration in microsatellite DNA. These mutations included an AG deletion at codons 877-878 of hMSH2 gene, an AAG deletion at codons 616-618 of hMLH1 gene, and a C-->T single-base substitution at codon 217 of hMLH1 gene. Seven of eight germ line mutations found in this study are new mutations that have not been reported previously. In families in which germ line mutations were identified presymptomatic examination was then carried out using polymerase chain reaction single-strand conformation polymorphism analysis of DNA from peripheral blood, and the result was the detection of family members predisposed to HNPCC who did not yet show signs of cancer. These results indicate the value of DNA analysis in the screening and diagnosis of HNPCC patients and families.

Somatic mutations of the adenomatous polyposis coli gene in gastroduodenal tumors from patients with familial adenomatous polyposis

We analyzed somatic mutations of the adenomatous polyposis coli (APC), p53, and K-ras genes in gastroduodenal polyps and normal gastroduodenal mucosa from 21 familial adenomatous polyposis patients, using PCR-single-strand conformation polymorphism and direct sequencing methods. Seventy-five polyps were obtained from these patients endoscopically or surgically, and they were histopathologically diagnosed as mild adenoma, moderate adenoma, severe adenoma, adenocarcinoma, and fundic gland polyp. Examining the APC-coding region where somatic mutations in colorectal tumors are known to be clustered, we detected 47 somatic mutations. The frequency of mutation detected was 6 of 9 (67%) in ampullary adenomas, 1 of 2 (50%) in ampullary adenocarcinoma, 11 of 24 (46%) in non-ampullary adenomas, 26 of 29 (90%) in gastric adenomas, and 3 of 11 (27%) in gastric fundic gland polyps. These mutations frequently occurred at codons 1450, 1462-1465, and 1554-1556, the third being a newly found hot spot. All mutations formed stop codons that resulted in truncated APC proteins. K-ras mutation was detected only in an ampullary adenocarcinoma, and p53 mutation was not detected in any of the tumors analyzed. There was no somatic mutation detected in samples of flat mucosa that were diagnosed as normal mucosa both endoscopically and histopathologically. Frequent APC mutations in mild and small adenomas, similar to the findings in severe and large adenomas, suggested that the genetic change in the APC gene occurs in an early stage of forming gastroduodenal adenomas. Moreover, the presence of somatic APC mutations in fundic gland polyps suggests that inactivation of the APC gene plays a role not only in forming adenomas but also in forming hyperplastic polyps in fundic gland mucosa, and there may be some additional steps to the adenoma-carcinoma sequence.

Effects of NIP-502 on antigen-induced bronchial responses and allergic reactions in animal models

We examined the effect of a newly synthesized pyridazinone derivative, NIP-502 [4-chloro-5-(3-ethoxy)-4-phenoxybenzamine)-3(2H)-pyridazinone], on antigen-induced bronchial responses and allergic reactions in several animal models. NIP-502 (10 mg/kg, p.o.) inhibited the antigen-induced immediate asthmatic response in passively sensitized guinea pigs. The inhibitory effect was also observed in metyrapone (an inhibitor of 11 beta-hydroxylase)-pretreated guinea pigs. NIP-502 improved ovalbumin (OA)-induced airway hyperresponsiveness to acetylcholine and inhibited the OA-induced increase in the number of inflammatory leukocytes in the bronchoalveolar lavage fluid. These inhibitory effects on OA-induced responses were similar to those of prednisolone. NIP-502 also showed an inhibitory effect on the passive cutaneous anaphylactic reaction in rats but did not inhibit the reversed cutaneous anaphylactic reaction, reversed Arthus reaction or delayed type hypersensitivity reaction. On the other hand, prednisolone showed broad inhibitory effects except for the reversed cutaneous anaphylactic reaction. In the in vitro study, NIP-502 (30 microM) significantly inhibited Formyl-Met-Leu-Phe-induced superoxide anion production by the guinea pig alveolar macrophages. These results indicate that the inhibitory effects of NIP-502 on bronchial responses are similar to those of prednisolone, but this compound seemed to act more selectively on the respiratory tract than prednisolone. Because of its effectiveness against a variety of bronchial responses, NIP-502 may be useful in the treatment of bronchial asthma.

In vivo sulfhydryl modification of the ligand-binding site of Tsr, the Escherichia coli serine chemoreceptor

The Escherichia coli chemoreceptor Tsr mediates an attractant response to serine. We substituted Cys for Thr-156, one of the residues involved in serine sensing. The mutant receptor Tsr-T156C retained serine- and repellent-sensing abilities. However, it lost serine-sensing ability when it was treated in vivo with sulfhydryl-modifying reagents such as N-ethylmaleimide (NEM). Serine protected Tsr-T156C from these reagents. We showed that [3H]NEM bound to Tsr-T156C and that binding decreased in the presence of serine. By pretreating cells with serine and cold NEM, Tsr-T156C was selectively labeled with radioactive NEM. These results are consistent with the location of Thr-156 in the serine-binding site. Chemical modification of the Tsr ligand-binding site provides a basis for simple purification and should assist further in vivo and in vitro investigations of this chemoreceptor protein.

Peri-operative complications in adult moyamoya disease

The incidence and causes of peri-operative haemodynamic complications in adult Moyamoya disease were examined by reviewing 55 surgically treated adult patients. Ninety-nine craniotomies were performed in these patients, and eight peri-operative complications (four infarctions, two haemorrhagic infarctions and two reversible ischaemic neurological deficits without a new lesion) were seen. All of the eight haemodynamic complications arose in the initially affected hemispheres regardless of the side of operation. Some nonsurgical haemodynamic risk factors, i.e., hypercapnia, hypocapnia and hypotension/hypovolaemia, were noted in all of the eight cases, although the statistical analysis could not clarify the relevance of such factors to peri-operative complications. Surgical factors which might be responsible for the complications were noted in three cases. Sparing vital collateral vessels and minimum brain retraction as well as avoidance of non-surgical haemodynamic risk factors are considered to be essential to prevent peri-operative haemodynamic brain damage in adult Moyamoya disease.

Long-term angiographic follow-up of lesions patent 6 months after percutaneous coronary angioplasty

To determine long-term angiographic prognosis after successful angioplasty (< 50% residual stenosis, > or = 20% reduction of stenosis, and no major complications), coronary angiography was performed 2 to 4 years after angioplasty in patients who were < or = 70 years old at the time of treatment and who showed patency (< or = 50% stenosis) 6 months after the initial procedure. Among 407 lesions that were dilated in 333 patients between 1983 and 1989, 298 (73.2%) lesions were reviewed by long-term angiography after 177 +/- 34 weeks. At long-term follow-up, 4 (1.3%) lesions were totally occluded, 3 (1.0%) had severe stenosis (> or = 75% stenosis), 9 (3.0%) had mild stenosis (> 50% to < 75% stenosis), and 282 (94.6%) were patent (< or = 50% stenosis). The percentage of stenosis of patent lesions decreased from 24% +/- 14% at 6 months to 21% +/- 13% at long-term follow-up (p < 0.0001). No specific clinical or angiographic characteristics were identified in patients with severe stenosis at long-term follow-up. These findings indicate that when patency is obtained 6 months after angioplasty, a 95% long-term patency rate with regression of stenosis can be expected.

The Ca2+ influx induced by beta-amyloid peptide 25-35 in cultured hippocampal neurons results from network excitation

Although a neurotoxic role has been postulated for the beta-amyloid protein (beta AP), which accumulates in brain tissues in Alzheimer's disease, a precise mechanism underlying this toxicity has not been identified. The peptide fragment consisting of amino acid residues 25 through 35 (beta AP25-35), in particular, has been reported to be toxic in cultured neurons. We report that beta AP25-35, applied to rat hippocampal neurons in culture, caused reversible and repeatable increases in the intracellular Ca2+ concentration ([Ca2+]i), as measured by fura 2 fluorimetry. Furthermore, beta AP25-35 induced bursts of excitatory potentials and action potential firing in individual neurons studied with whole cell current clamp recordings. The beta AP25-35-induced [Ca2+]i elevations and electrical activity were enhanced by removal of extracellular Mg2+, and they could be blocked by tetrodotoxin, by non-N-methyl-D-aspartate (NMDA) and NMDA glutamate receptor antagonists, and by the L-type Ca2+ channel antagonist nimodipine. Similar responses of bursts of action potentials and [Ca2+]i increases were evoked by beta AP1-40. Responses to beta AP25-35 were not prevented by pretreatment with pertussis toxin. Excitatory responses and [Ca2+]i elevations were not observed in cerebellar neuron cultures in which inhibitory synapses predominate. Although the effects of beta AP25-35 depended on the activation of glutamatergic synapses, there was no enhancement of kainate- or NMDA-induced currents by beta AP25-35 in voltage-clamp studies. We conclude that beta AP25-35 enhances excitatory activity in glutamatergic synaptic networks, causing excitatory potentials and Ca2+ influx. This property may explain the toxicity of beta AP25-35.