Extended trans-sternal thymectomy for myasthenia gravis.

Otto reported thymectomy under transverse sternotomy. It currently is not a widely used procedure, however. Jaretzki graded the completeness of removal of thymic tissue as follows: maximal thymectomy 98% to 100%, extended thymectomy 85% to 95%, modified transcervical thymectomy (Cooper) 75% to 80%, VATS thymectomy 80% to 85%, simple trans-sternal thymectomy 70% to 75%, and simple transcervical thymectomy 40% to 50%. The results of each procedure do not always reflect the completeness of removal. The tables show that the most widely accepted procedure is the extended thymectomy, and the results of it are prominent and stable. Why do the results of the maximal thymectomy, however, not exceed those of the extended thymectomy? It is supposed that quantitative increase of removed thymic tissues in the maximal thymectomy might be minimal.

Oxidation of thymine to 5-formyluracil in DNA promotes misincorporation of dGMP and subsequent elongation of a mismatched primer terminus by DNA polymerase.

5-Formyluracil (fU) is a major oxidative thymine lesion generated by ionizing radiation and reactive oxygen species. In the present study, we have assessed the influence of fU on DNA replication to elucidate its genotoxic potential. Oligonucleotide templates containing fU at defined sites were replicated in vitro by Escherichia coli DNA polymerase I Klenow fragment deficient in 3'-5'-exonuclease. Gel electrophoretic analysis of the reaction products showed that fU constituted very weak replication blocks to DNA synthesis, suggesting a weak to negligible cytotoxic effect of this lesion. However, primer extension assays with a single dNTP revealed that fU directed incorporation of not only correct dAMP but also incorrect dGMP, although much less efficiently. No incorporation of dCMP and dTMP was observed. When fU was substituted for T in templates, the incorporation efficiency of dAMP (f(A) = V(max)/K(m)) decreased to (1/4) to (1/2), depending on the nearest neighbor base pair, and that of dGMP (f(G)) increased 1.1-5.6-fold. Thus, the increase in the replication error frequency (f(G)/f(A) for fU versus T) was 3.1-14.3-fold. The misincorporation rate of dGMP opposite fU (pK(a) = 8.6) but not T (pK(a) = 10.0) increased with pH (7.2-8.6) of the reaction mixture, indicating the participation of the ionized (or enolate) form of fU in the mispairing with G. The resulting mismatched fU:G primer terminus was more efficiently extended than the T:G terminus (8.2-11.3-fold). These results show that when T is oxidized to fU in DNA, fU promotes both misincorporation of dGMP at this site and subsequent elongation of the mismatched primer, hence potentially mutagenic.

Development of a tracheal stapling device.

OBJECTIVE: Recent years have witnessed a multitude of technical advances regarding gastrointestinal and vascular anastomosis. However, difficulties still hamper tracheal and bronchial anastomosis. We have therefore developed a novel set of instruments and performed end-to-end anastomosis of the transected canine cervical trachea to establish the operative procedures. METHODS: A novel set of instruments was developed for tracheal anastomosis including two pairs of forceps for grasping the free tracheal ends, a metal connecting device, and clamping forceps for staple insertion. Briefly, the operative procedure involves fixation of forceps circumferentially to hold the cut trachea. End-to-end anastomosis is completed by joining the forceps with a clamp and stapling the tracheal ends everted outward. End-to-end anastomosis of the cervical trachea was performed on 23 dogs. Animals were monitored on a daily basis, and bronchofiberscopy was performed periodically. Deaths from all causes were evaluated by immediate necropsy. Sixteen dogs were sequentially sacrificed at 1, 2, 3 and at 6 months after surgery. RESULTS: In our dog model, stenosis at the anastomosis of the cervical trachea was found as a complication in 8 of 23 cases. Tracheal rupture occurred in a further 3 cases, slight granulation in another 4, and the remaining 8 showed no complication. Histological findings of anastomotic healing were similar to those reported for hand suture.

Quantitation of DNA damage by an aldehyde reactive probe (ARP).

DNA is constantly damaged by endogenous and environmental agents. Abasic sites representing a major class of DNA damage can be quantitated by an ELISA-like assay using an aldehyde reactive probe (ARP). It is shown that oxidative pyrimidine lesions can be also quantitated by the ARP assay in combination with the treatment with endonuclease III.

Preparation and enzymatic recognition of guanine lesions induced by nitrogen oxides.

Xanthine (Xan) and oxanine (Oxa) are the major deamination products of guanine formed by the treatment with nitrogen oxides (e.g., NO and HNO2). In this study, 2'-deoxyribonucleoside 5'-triphosphates of Xan and Oxa were prepared by the NaNO2 treatment of dGTP. These modified nucleotides were incorporated into oligonucleotides by DNA polymerase reactions. The repair activities of various DNA N-glycosylases for Xan and Oxa were examined using these substrates.

Enzymatic repair of 5-formyluracil. I. Excision of 5-formyluracil site-specifically incorporated into oligonucleotide substrates by alka protein (Escherichia coli 3-methyladenine DNA glycosylase II).

5-Formyluracil (fU) is a major thymine lesion produced by reactive oxygen radicals and photosensitized oxidation. We have previously shown that fU is a potentially mutagenic lesion due to its elevated frequency to mispair with guanine. Therefore, fU can exist in DNA as a correctly paired fU:A form or an incorrectly paired fU:G form. In this work, fU was site-specifically incorporated opposite A in oligonucleotide substrates to delineate the cellular repair mechanism of fU paired with A. The repair activity for fU was induced in Escherichia coli upon exposure to N-methyl-N'-nitro-N-nitrosoguanidine, and the induction was dependent on the alkA gene, suggesting that AlkA (3-methyladenine DNA glycosylase II) was responsible for the observed activity. Activity assay and determination of kinetic parameters using purified AlkA and defined oligonucleotide substrates containing fU, 5-hydroxymethyluracil (hU), or 7-methylguanine (7mG) revealed that fU was recognized by AlkA with an efficiency comparable to that of 7mG, a good substrate for AlkA, whereas hU, another major thymine methyl oxidation products, was not a substrate. (1)H and (13)C NMR chemical shifts of 5-formyl-2'-deoxyuridine indicated that the 5-formyl group caused base C-6 and sugar C-1' to be electron deficient, which was shown to result in destabilization of the N-glycosidic bond. These features are common in other good substrates for AlkA and are suggested to play key roles in the differential recognition of fU, hU, and intact thymine. Three mammalian repair enzymes for alkylated and oxidized bases cloned so far (MPG, Nth1, and OGG1) did not recognize fU, implying that the mammalian repair activity for fU resided on a yet unidentified protein. In the accompanying paper (Terato, H., Masaoka, A., Kobayashi, M., Fukushima, S., Ohyama, Y., Yoshida, M., and Ide, H., J. Biol. Chem. 274, 25144-25150), possible repair mechanisms for fU mispaired with G are reported.

Enzymatic repair of 5-formyluracil. II. Mismatch formation between 5-formyluracil and guanine during dna replication and its recognition by two proteins involved in base excision repair (AlkA) and mismatch repair (MutS).

5-Formyluracil (fU), a major methyl oxidation product of thymine, forms correct (fU:A) and incorrect (fU:G) base pairs during DNA replication. In the accompanying paper (Masaoka, A., Terato, H., Kobayashi, M., Honsho, A., Ohyama, Y., and Ide, H. (1999) J. Biol. Chem. 274, 25136-25143), it has been shown that fU correctly paired with A is recognized by AlkA protein (Escherichia coli 3-methyladenine DNA glycosylase II). In the present work, mispairing frequency of fU with G and cellular repair protein that specifically recognized fU:G mispairs were studied using defined oligonucleotide substrates. Mispairing frequency of fU was determined by incorporation of 2'-deoxyribonucleoside 5'-triphosphate of fU opposite template G using DNA polymerase I Klenow fragment deficient in 3'-5' exonuclease. Mispairing frequency of fU was dependent on the nearest neighbor base pair in the primer terminus and 2-12 times higher than that of thymine at pH 7.8 and 2.6-6.7 times higher at pH 9.0 with an exception of the nearest neighbor T(template):A(primer). AlkA catalyzed the excision of fU placed opposite G, as well as A, and the excision efficiencies of fU for fU:G and fU:A pairs were comparable. In addition, MutS protein involved in methyl-directed mismatch repair also recognized fU:G mispairs and bound them with an efficiency comparable to T:G mispairs, but it did not recognize fU:A pairs. Prior complex formation between MutS and a heteroduplex containing an fU:G mispair inhibited the activity of AlkA to fU. These results suggest that fU present in DNA can be restored by two independent repair pathways, i.e. the base excision repair pathway initiated by AlkA and the methyl-directed mismatch repair pathway initiated by MutS. Biological relevance of the present results is discussed in light of DNA replication and repair in cells.

Thymic neuroendocrine tumor (thymic carcinoid): a clinicopathologic study in 15 patients.

BACKGROUND: Thymic neuroendocrine tumor (carcinoid tumor) is rare, and prognosis for patients with this tumor has been difficult to predict. METHODS: The medical records of 15 patients were reviewed, and the patients were classified according to tentative TNM classification and histologic grade. RESULTS: Ten (66.7%) of 15 patients were male. Lymph node metastases were identified in 9 (60%) of 15 patients at the time of resection. There were one grade 1, nine grade 2, and five grade 3 tumors. Total resection was possible in 13 patients. Distant metastases developed in 10 (76.9%) of these 13 patients, although no local recurrence developed. Of these 10 patients, 6 died of distant metastases 5 to 25 months after the recurrence. Three patients are still alive, with metastases to the bone, spleen, and pleura 1 to 24 months after the diagnosis of recurrence. Two patients are presently tumor free (T1N0, grade 3 and T3N2, grade 2), but only 1 has survived beyond 5 years. CONCLUSIONS: Thymic neuroendocrine tumor must be regarded as a malignant neoplasm that is prone to metastasize to mediastinal lymph nodes and to distant sites, even after total excision. Neither T and N classification nor histologic grade has been successful in predicting the outcome of a patient with this tumor. More aggressive management, including adjuvant therapies and reexcision of subsequent tumors, may result in increased survival.

Cellular repair mechanism of 5-formyluracil.

5-Formyluracil (fU) is an oxidative DNA base damage. This damage has been suggested to be mutagenic and but enzymatic repair of the damage is little known. In this study, repair enzymes that recognize fU have been studied. Kinetic analysis of the repair activity of E. coli 3-methyladenine DNA glycosylase II (AlkA) showed that fU was removed by AlkA with the efficiency comparable to 7-methylguanine. We also examined the participation of the methyl-directed mismatch repair system. The affinity of MutS to the fU:G mispair was essentially similar to that of the T:G mispair that was most efficiently recognized by the MutSLH system. These results suggest two distinct repair pathways of fU in E. coli.

Experimental reconstruction of the mediastinal trachea with a wing-shaped reversed esophageal flap.

BACKGROUND: In cases of extensive tracheal resection in which direct end-to-end anastomosis is impossible there is a need for reconstruction. Nevertheless, with the present lack of reliable artificial trachea, no reconstruction method is available to assure safe replacement of the mediastinal trachea. METHODS: After tubular resection of the mediastinal trachea in mongrel dogs, the trachea was reconstructed using a wing-shaped reversed esophageal flap. A silicone tube was used as an internal stent. RESULTS: In group I (16 animals), three tracheal rings were resected; in group II (4 animals), six tracheal rings; in group III (6 animals), eight tracheal rings; and in group IV (5 animals), eight tracheal rings and the lining of the greater omentum. Safe reconstruction was accomplished in all cases in groups I and II, 2 of 6 cases in group III, and 2 of 5 cases in group IV. The omentopexy failed to prevent incomplete closure, yet served to minimize inflammation in the mediastinum. CONCLUSIONS: A reversed esophageal autograft can be considered as a tracheal replacement.

Chondrosarcoma originating from the trachea.

We report a tracheal chondrosarcoma in a 54-year-old man, treated with neodymium:yttrium-aluminum garnet laser vaporization via fiberoptic bronchoscopy followed by surgical resection. Chondrosarcomas of the trachea are extremely rare tumors. To our knowledge, there are 9 cases of chondrosarcoma of the trachea reported in the English-language literature, to which we add the tenth.

[TNM classification of thymic epithelial tumors].

The five-stage classification system of thymoma (I, II, III, IVa, IVb) is now adopted widely. As the cases with lymphogenous or hematogenous metastasis are included in IVb, it is suggested that IV b includes various groups with different prognostic factors. This facilitates establishment of TNM classification of thymic epithelial tumours (thymoma, thymic cancer and thymic carcinoid). T factors correspond with the stages, I: T1N0M0, II: T2N0M0, III: T3N0M0, and IV a : T4 N0M0. N and M factors are as follows: N1 : restricted to the anterior mediastinal nodes; N2 : intrathoracic nodes; N3 : supraclavicular nodes; and M1 : hematogenous metastasis and/or extrathoracic nodes excluding supraclavicular nodes. Such criteria were used to classify IVb into any T N(1,2,3) M0, and any T any NM1. N criteria could divide the cases into the groups with proper populations in IV b thymoma, thymic carcinoma, and thymic carcinoid, respectively. The possible relationships between survival and TNM were investigated in thymic carcinoma cases. T, N, and M have a relationship with survival, respectively. This TNM classification is not yet authorized, but it is used in many clinics in Japan to determine the selection of therapy and estimate the therapeutic effect.

[Intrapulmonary laceration revealed by computed tomography in a patient with pneumomediastinum].

An 18-year-old man had bronchial asthma and a pneumomediastinum. A computed tomographic scan of the chest revealed the pneumomediastinum, intrapulmonary laceration of the S1b, and a small amount of air in the perivascular space from V1a to V1. Increased pressure in intrapulmonary airways may have resulted in ruptured S1b alveoli and air leakage into the interstitium between the surrounding secondary lobules. The air may have moved along the perivascular space (pulmonary vein) toward the hilum, and eventually into the mediastinum. We know of no previous report of pneumomediastinum in which images of intrapulmonary lesions are presented. In this case computed tomography revealed the mechanism by which the pneumomediastinum probably developed.

Clinical significance of bcl-2 gene expression in human breast cancer tissues.

The expression of estrogen receptor (ER) and bcl-2 (Bcl-2), an apoptosis protective oncogene, in normal and cancerous breast duct epithelia was immunohistochemically examined in fresh frozen tumor tissues from 142 Japanese breast cancer patients. The clinico-pathological characteristics and the disease free survival of the patients were analyzed. The expression of both the proteins was also observed in intraductal components of breast cancer. Although less than 1% of normal duct epithelia expressed ER, Bcl-2 was diffusely expressed. The expression of both these proteins in breast cancer significantly correlated with each other. Their expression significantly correlated negatively with tumor size but not with lymph node status. The papillo-tubular sub-type of invasive ductal carcinoma expressed Bcl-2 significantly more frequently than the solid-tubular sub-type. Patients with Bcl-2 expressing tumors survived without recurrence significantly more than those with tumors exhibiting reduced expression. Papillary-cribriform type intraductal components expressed both those proteins more often than the solid-comedo type.

Thymic follicular hyperplasia manifested as an anterior mediastinal mass.

A rare case of thymic follicular hyperplasia manifested as an asymptomatic anterior mediastinal mass in a 44-year-old man is herein reported. The resected thymus showed prominent medullary lymphoid follicles, an increased number of Hassall's corpuscles, and cysts of varying sizes. This paper discusses the histopathological condition of this lesion.

Mechanisms of the genotoxic effects associated with 5-formyluracil: effect of exogenous 5'-formyl-2'-deoxyuridine.

E. coli HB101 harboring plasmid pUC19 was grown in the presence of 5-formyl-2'-deoxyuridine (fdU) to evaluate the genotoxic and cytotoxic potentials associated with this DNA lesion. Cell growth was inhibited by fdU in a concentration-dependent manner, but increased mutation was not observed in the lacZ(alpha) gene of pUC19. The lack of the mutagenic effect was attributed to poor utilization of fdU as a substrate by thymidine kinase, which converts exogenous thymidine analogs to the corresponding 5'-monophosphates in the salvage pathway.

Elevated plasma thymosin-alpha1 levels in lung cancer patients.

OBJECTIVE: Prothymosin-alpha, the precursor of thymosin-alpha1, may play a role in cell proliferation, and the plasma level of thymosin-alpha1 may reflect the degree of proliferation of the tumor cells. METHODS: Recently, a new sandwich immunoradiometric assay for thymosin-alpha1 was developed using monoclonal and polyclonal antibodies. In this investigation, we used this assay to measure plasma and tissue level of thymosin-alpha1 in 131 lung cancer patients. RESULTS: We found that the mean plasma thymosin-alpha1 levels in lung cancer patients were higher than in normal individuals (P < 0.001). However, half of the patients showed normal levels. Thymosin-alpha1 levels correlated neither with the stage nor pathological subtype of the lung cancer, and did not decrease significantly in the 4 weeks after the resection of the tumor. Thymosin-alpha1 levels of lung cancer patients with another cancer were higher than those without evidence of other cancers (P = 0.03). Survival of patients with normal levels of plasma thymosin-alpha1 was significantly better than that with higher levels (P = 0.04). CONCLUSIONS: The plasma level of thymosin-alpha1 may be used as a marker for the prognosis of lung cancer patients. Further investigations are warranted to determine its role in the lung cancer.

Endothelial prostanoids involved in the relaxation produced by acetylcholine in the human pulmonary artery.

In ring preparations of human pulmonary artery contracted with noradrenaline (NA), the application of acetylcholine (ACh) enhanced the tension, and withdrawal produced a large relaxation which was sustained for about 10 min and required over 20 min for recovery; the latter relaxation appeared only in the endothelium-intact preparation. Indomethacin increased the amplitude of NA contractions, changed the ACh-induced contraction to relaxation, and inhibited the ACh-induced sustained relaxation. Nitroarginine increased the amplitude of NA and ACh-induced contractions, with no significant change in the ACh-induced sustained relaxation. These effects of indomethacin and nitroarginine were observed only in the endothelium-intact preparations. In NA-contracted preparations, exogenously applied prostaglandin I2 (PGI2) produced relaxation. Thus, in human pulmonary arteries, NA and ACh activities release vasodilator prostanoids and nitroarginine-sensitive EDRF from the endothelium, and initiate direct contractile actions to smooth muscle. The prostanoid-induced relaxation is sustained for a long time after the withdrawal of ACh stimulation and can be mimicked by exogenously-applied PGI2.

Extended thymectomy for myasthenia gravis patients: a 20-year review.

BACKGROUND: Since 1973 we have performed extended thymectomy for myasthenia gravis because of the presence of thymic tissue in the anterior mediastinal fatty tissue. Follow-up results were reviewed and influencing factors were investigated. METHODS: Three hundred seventy-five patients with myasthenia gravis (286 nonthymomatous and 89 thymomatous) who have undergone extended thymectomies were reviewed. The status of the patients was evaluated as follows: A (remission), B (improvement), C (no change), D (deterioration), E (death due to myasthenia gravis). Evaluation was performed at 3 and 6 months, and at 1, 3, 5, 10, 15, and 20 years. The effectiveness of the operation was estimated by the remission rate (RR = A/Total number of patients evaluated) and the palliation rate (PR = A + B/Total number of patients evaluated) at each point. RESULTS: Remission rates of the nonthymomatous patients were 15.2% (3 months), 15.9% (6 months), 22.4% (1 year), 36.9% (3 years), 45.8% (5 years), 55.7% (10 years), 67.2% (15 years), and 50.0% (20 years). Remission rates in the thymomatous patients were 13.6% (3 months), 17.5% (6 months), 27.5% (1 year), 32.4% (3 years), 23.0% (5 years), 30.0% (10 years), 31.8% (15 years), and 37.5% (20 years). Absence of thymoma, younger age, and short duration of the disease were favorable prognostic factors. Thymectomy was effective also in patients with ocular myasthenia gravis. Preoperative steroid administration did not improve the outcome. CONCLUSIONS: Extended thymectomy is an excellent operative procedure for myasthenia gravis in both nonthymomatous and thymomatous patients.