Involvement of C-terminal amino acids of a hyperthermophilic serine racemase in its thermostability.

Pyrobaculum islandicum is a hyperthermophilic archaeon that grows optimally at 95-100 °C. In the previous study, we extensively purified a serine racemase from this organism and cloned the gene for overexpression in Escherichia coli (Ohnishi et al. 2008). This enzyme also exhibits highly thermostable L-serine/L-threonine dehydratase activity. In the present study, we aimed to elucidate the molecular mechanisms underlying the high thermostability of this enzyme. A recombinant variant of this enzyme, PiSRvt, constructed by truncating the C-terminal 72 amino acids, was compared with the native enzyme, PiSR. The dehydratase activity of PiSR and PiSRvt was found to owe to a homotrimer and a monomer, respectively, that demonstrated high and moderate thermostability, respectively. These observations reveal that the C-terminal region contributes to monomer trimerization that provides the extreme thermostability.

[RISK OF TUBERCULOSIS INFECTION AND DISEASE AMONG JAPANESE FEMALE NURSES AND MALE DOCTORS IN RECENT YEARS].

[Objectives and Materials] Based on the tuber- culosis (TB) surveillance database, the incidence rates of TB infection and active disease among healthcare workers were observed for female nurses and male doctors in 2010 in comparison with those of the general population. [Results] The relative risk (RR) of active TB among female nurses aged 20-69 years was 4.86 (95% confidence interval: 4.31-5.45) for 2010, which has increased from 2.30 observed in 1987-1997. The RR was highest for nurses aged 20-29 years at 8.84 and declined with age until 3.60 for those aged 50-59 years that was still significantly higher than 1. For male doctors the RR was significantly higher than 1 only for those aged 39 years or younger. The rates of those who were -indicated for treatment of latent TB infection (LTBI) were clearly higher among healthcare workers; for female nurses the RR was 32.7 (95% CI: 30.5-35.0), ranging from the highest level of 62.8 among those aged 20-29 years down to 11.6 for those aged 60-69 years. For male doctors also, the RR was high at 9.7 (7.9- 11.7) for 20-69 years, ranging from 14.5 for those aged 20- 29 years down to 5.3 for those aged 60-69 years. [Discussion] TB cases of nurses and doctors were more likely to be detected by the active case finding measures such as periodic screening and contact investigations than cases in the general population, which indicates the current effort of addressing the occupational exposure in the healthcare set- tings. The high level of risk of TB disease as Iwell as LTBI among healthcare professions and its possibly increasing trend as. seen in female nurses warrants further strengthening of monitoring of the problem and overall countermeasures in their workplaces.

[Analysis on workload for hospital DOTS service].

BACKGROUND AND OBJECTIVE: A directly observed treatment short course (DOTS) trial was launched in Japan in the late 1990s and targeted patients with social depression at urban areas. Based on these findings, the Ministry of Health, Labour and Welfare established the Japanese DOTS Strategy in 2003, which is a comprehensive support service ensuring the adherence of tuberculosis patients to drug administration. DOTS services are initially provided at the hospital to patients with infectious tuberculosis who are hospitalized according to the Infectious Diseases Control Law. After being discharged from the hospital, the patients are referred to a public health center. However, a survey conducted in 2008 indicated that all the patients do not receive appropriate DOTS services at some hospitals. In the present study, we aimed to evaluate the protocols and workload of DOTS at hospitals that are actively involved in tuberculosis medical practice, including DOTS, to assess whether the hospital DOTS services were adequate. METHOD: We reviewed a series of articles on hospital DOTS from a Japanese journal on nursing for tuberculosis patients and identified 25 activities regarding the hospital DOTS service. These 25 items were then classified into 3 categories: health education to patients, support for adherence, and coordination with the health center. In total, 20 hospitals that had > 20 authorized tuberculosis beds were selected--while considering the geographical balance, schedule of this survey, etc.--from 33 hospitals where an ex-trainee of the tuberculosis control expert training program in the Research Institute of Tuberculosis (RIT) was working and 20 hospitals that had collaborated with our previous survey on tuberculosis medical facilities. All the staff associated with the DOTS service were asked to record the total working time as well as the time spent for each activity. The data were collected and analyzed at the RIT. RESULT: The working times for each activity of the DOTS service for nurses, pharmacists, ward clerks, head nurses, and doctors were 100, 90, 87, 86, and 63 min, respectively. For other professions, including medical social workers, nursing aids, nutritionists, and physical therapists, the working times for each activity of the DOTS service were 31, 18, 10, and 8 min, respectively. The professionals who spent a longer time on health education, support for patient adherence, and coordination with the health center were pharmacists, doctors, and head nurses; nurses, pharmacists, and doctors; and head nurses, doctors, and ward clerks, respectively. DISCUSSION: Aging of tuberculosis patients was associated with problems on adherence in many patients, including patients who were not suited for a standard regimen, patients whose activity of daily life had deteriorated due to senile dementia, patients with diabetes mellitus, etc. Smoking cessation and mental care for cases of multi-drug resistant disease are new challenges in tuberculosis patient care. The present study clearly indicated that activities including patient education, support for patient adherence, and coordination with the health center--essential components of the hospital DOTS service according to the Japanese DOTS Strategy--were performed by a team of professionals including doctors, nurses, pharmacists, medical social workers, etc., depending on the features and roles that they serve and the needs of each patient. For good practice of hospital DOTS, it is essential to not only provide DOTS, but also effectively provide individual or group health education and coordinate with health centers, thus aiming towards a better community DOTS service after patient discharge.

MEG measures of covert orienting and gaze processing in children.

We investigated developmental differences in the cortical attention processing network using magnetoencephalography (MEG) and a spatial cueing task in 7-8 and 12-13 year old children. The cueing paradigm consisted of a centrally presented face with left or right averted eye-gaze in the gaze cue condition, and a central face with straight gaze presented with a cue stimulus to the left or right of the face in the peripheral cue condition. Cue congruency was 50 %. MEG was recorded during the two conditions and event-related beamforming was used to determine the timing and location of the brain activity related to target detection with the two types of cueing. The MEG data showed no age differences in the eye-gaze condition, but a developmental difference characterised by slower and more diffuse activations for peripheral cues in the younger versus the older age group. In the 7-8 year olds activation peaked around 300 ms, and was localised to left inferior frontal gyrus as well as posterior areas related to visuo-spatial processing. The 12-13 year olds showed a temporoparietal pattern of activation characteristic of spatial reorientation which resembled that seen for adult participants using the same paradigm (Nagata et al. 2012). The activation peaked around 200 ms and was localised to the left superior frontal gyrus, middle frontal gyrus but bilaterally near the temporoparietal junction. The data indicate maturational changes in brain activity for peripheral cueing.

[Expanding the role of the nursing profession in tuberculosis medical services].

Implications of changes in the law regarding the payment system for medical services in 2012 for TB medicine and care include mandatory hospital DOTS, planning and implementing adherence support for patients, patient education, and close cooperation with public-health centers. Nurses are expected to contribute to early diagnosis of TB and treatment completion among high-risk populations by coordinating with the community and relevant organizations. It is also important to clarify roles and establish a network through which necessary information and advice may be sought from specialists. Expanding the role of nursing professions in TB care and medicine is hoped to improve the level of awareness and knowledge among persons involved in TB prevention, care, and medicine.

[Nationwide survey of suitability of tuberculosis wards for in-hospital care of tuberculosis patients].

PURPOSE: To clarify the situation and suitability of tuberculosis wards for in-hospital tuberculosis care, with a view toward establishing a national standard for tuberculosis wards. METHODS: Data were obtained by sending questionnaires to all 321 tuberculosis wards in Japan. RESULTS: Of the hospitals to which questionnaires were sent, 69.3% returned their responses. In most of these hospitals, the total number of beds in one tuberculosis ward was either less than 20 or more than 40. In approximately two-thirds of the hospitals, tuberculosis wards were incorporated into another (non-tuberculosis) ward. In more than 70% of the hospitals, the mean hospital stay of tuberculosis patients exceeded 40 days. This relatively long hospital stay implies that amenities are a very important issue in tuberculosis wards; however, amenities were generally far from sufficient in most of the hospitals. Of all the tuberculosis beds, 18.2% were in single-occupant rooms and 19.4% had a sufficient floor area (more than 15 m2). Beds in single-occupant rooms with sufficient floor area, equipped with a toilet, bath or shower, washstand, negative-pressure control, and HEPA filter in an air exhaust duct, comprised 2.4% of all tuberculosis beds. CONCLUSION: In spite of the relatively long hospital stays, amenities were generally less than adequate. The conditions in most tuberculosis wards were far below the presumptive recommended standards. When national standards for tuberculosis wards are established, these findings should be taken into consideration.

Multidrug-Resistant Tuberculosis Outbreak among Immigrants in Tokyo, Japan, 2019-2021.

In mid-September 2019, a teenage Chinese male student and part-time waiter in Tokyo was diagnosed with multidrug-resistant (MDR) sputum smear-positive pulmonary tuberculosis (TB). This study describes the outbreak investigation of his friends and colleagues at the restaurant. We investigated 6 friends and 15 colleagues; 5 friends and 13 colleagues underwent interferon-γ release assay (IGRA). Of these, 3 friends (60.0%) and 4 colleagues (30.8%) were IGRA-positive. Each of the friends and colleagues was found to have MDR-TB (20% and 7.7%, respectively). Challenges during the investigation were the unavailability of regimens for latent TB infection (LTBI) for contacts with MDR-TB, budgetary constraints concerning implementing computed tomography (CT) scans for the contacts, frequent address changes of foreign-born patients and contacts, investigation during the coronavirus disease pandemic, and variations of alphabetical expression of the names of the patients and contacts, particularly for those from China. It is recommended that the national government officially adopt prophylaxis regimens for LTBI with MDR-TB, address the budgetary constraints regarding CT scans, and deploy liaison officers for coordinating investigations involving many foreign-born patients and contacts scattered in multiple municipalities. The names of foreign-born persons could more accurately be identified using both the alphabet and Chinese characters.

Aqueous Extract from Leaves of Citrus unshiu Attenuates Lipopolysaccharide-Induced Inflammatory Responses in a Mouse Model of Systemic Inflammation.

Inflammation is related to various life-threatening diseases including cancer, neurodegenerative diseases, and metabolic syndrome. Because macrophages are prominent inflammatory cells, regulation of macrophage activation is a key issue to control the onset of inflammation-associated diseases. In this study, we aimed to evaluate the potential anti-inflammatory activity of Citrus unshiu leaf extract (CLE) and to elucidate the mechanism underlying its anti-inflammatory effect. We found the inhibitory activity of CLE on the secretion of proinflammatory cytokines and a chemokine from mouse macrophage-like RAW 264.7 cells and mouse peritoneal macrophages. The inhibitory activity of CLE was attributed to downregulated JNK, p38 MAPK, and NF-κB signaling pathways, leading to suppressed gene expression of inflammation-associated proteins. Oral administration of CLE significantly decreased the serum level of proinflammatory cytokines IL-6 and TNFα and increased that of anti-inflammatory cytokine IL-10 in lipopolysaccharide-induced systemic inflammation mice. In addition, oral administration of CLE decreased secretion and gene expression of several proinflammatory proteins in the liver and spleen of the model mice. Overall results revealed that C. unshiu leaf is effective to attenuate inflammatory responses in vitro and in vivo.

A multidrug-resistant tuberculosis outbreak in a language school: Tokyo, Japan, 2019-2020.

Background: Japan has successfully reduced the burden of tuberculosis (TB) in the past seven decades; however, there are still some issues in eliminating TB. Its presence in immigrants, particularly multidrug-resistant (MDR) TB, is one of them. In mid-September 2019, a teenage Chinese male student in a morning class of a Japanese language school in Tokyo, Japan, was diagnosed with sputum smear-positive pulmonary MDR-TB. Method: The outbreak cases were analyzed in a cohort study. Results: We investigated 138 students and 18 teachers, of whom 81 (51.9%) were male, 115 (73.7%) were aged from 20 to 29 years, and 124 (76.9%) were from China. Four other students in the same classroom and another in a different classroom from the index patient in the morning classes were also diagnosed with MDR-TB disease by the end of November 2020. In addition, 31 cases of latent TB infection (LTBI) were detected among the students and teachers. Students in the same classroom had the highest risk of TB infection (78.9%, 95% confidence interval [CI]: 54.4%-93.9%) with a relative risk of 8.6 (95% CI: 3.9-19.0), followed by students in the other classrooms of the morning classes (25.9%, 95% CI: 15.0%-39.7%) with a relative risk of 2.8 (95% CI: 1.2-6.8), compared with the afternoon class students (9.2%, 95% CI: 3.5-19.0) who had minimal contact with the index patient. Conclusion: National TB programs should adopt prophylaxis regimens for MDR-TB LTBI cases and provide prophylaxis to them, particularly if related to an outbreak. The Japanese government should screen immigrants for TB, particularly those from TB-endemic areas.

Purification of Helicobacter pylori NCTC 11637 cytochrome bc1 and respiration with D-proline as a substrate.

Helicobacter pylori is a microaerophilic bacterium associated with gastric inflammation and peptic ulcers. Knowledge of how pathogenic organisms produce energy is important from a therapeutic point of view. We found d-amino acid dehydrogenase-mediated electron transport from d-proline or d-alanine to oxygen via the respiratory chain in H. pylori. Coupling of the electron transport to ATP synthesis was confirmed by using uncoupler reagents. We reconstituted the electron transport chain to demonstrate the electron flow from the d-amino acids to oxygen using the recombinant cytochrome bc(1) complex, cytochrome c-553, and the terminal oxidase cytochrome cbb(3) complex. Upon addition of the recombinant d-amino acid dehydrogenase and d-proline or d-alanine to the reconstituted electron transport system, reduction of cytochrome cbb(3) and oxygen consumption was revealed spectrophotometrically and polarographically, respectively. Among the constituents of H. pylori's electron transport chain, only the cytochrome bc(1) complex had been remained unpurified. Therefore, we cloned and sequenced the H. pylori NCTC 11637 cytochrome bc(1) gene clusters encoding Rieske Fe-S protein, cytochrome b, and cytochrome c(1), with calculated molecular masses of 18 kDa, 47 kDa, and 32 kDa, respectively, and purified the recombinant monomeric protein complex with a molecular mass of 110 kDa by gel filtration. The absorption spectrum of the recombinant cytochrome bc(1) complex showed an alpha peak at 561 nm with a shoulder at 552 nm.

D-Amino acid dehydrogenase from Helicobacter pylori NCTC 11637.

Helicobacter pylori is a microaerophilic bacterium, associated with gastric inflammation and peptic ulcers. D-Amino acid dehydrogenase is a flavoenzyme that digests free neutral D-amino acids yielding corresponding 2-oxo acids and hydrogen. We sequenced the H. pylori NCTC 11637 D-amino acid dehydrogenase gene, dadA. The primary structure deduced from the gene showed low similarity with other bacterial D-amino acid dehydrogenases. We purified the enzyme to homogeneity from recombinant Escherichia coli cells by cloning dadA. The recombinant protein, DadA, with 44 kDa molecular mass, possessed FAD as cofactor, and showed the highest activity to D-proline. The enzyme mediated electron transport from D-proline to coenzyme Q(1), thus distinguishing it from D-amino acid oxidase. The apparent K(m) and V(max) values were 40.2 mM and 25.0 micromol min(-1) mg(-1), respectively, for dehydrogenation of D-proline, and were 8.2 microM and 12.3 micromol min(-1) mg(-1), respectively, for reduction of Q(1). The respective pH and temperature optima were 8.0 and 37 degrees C. Enzyme activity was inhibited markedly by benzoate, and moderately by SH reagents. DadA showed more similarity with mammalian D-amino acid oxidase than other bacterial D-amino acid dehydrogenases in some enzymatic characteristics. Electron transport from D-proline to a c-type cytochrome was suggested spectrophotometrically.

Proliferation of the hyperthermophilic archaeon Pyrobaculum islandicum by cell fission.

Pyrobaculum islandicum is a hyperthermophilic archaeon. P. islandicum cells have been suggested to multiply by constriction, budding and branching, as no septa were observed in cells by phase-contrast light microscopy. In this study, we observed the cells using transmission electron microscopy, scanning electron microscopy, and light microscopy with dark-field image analyses, and we report binary fission via septum formation to be the main mode of P. islandicum's proliferation. "Long cells" reported previously were found to comprise several cylindrical cells that align in tandem.

Breast metastasis from rectal cancer with BRAF V600E mutation: a case report with a review of the literature.

Metastasis of rectal cancer to the breast is an extremely rare clinical event. We report the case of a 67-year-old woman with a metastatic breast tumor derived from a BRAF V600E mutant rectal carcinoma that was diagnosed and resected curatively 1 year previously. Computed tomography showed a left breast mass and multiple lung nodules suspected to be indicative of recurrent rectal cancer. The ultrasonography examination demonstrated a 10 × 10-mm hypoechoic solid lesion in the left breast with an elevation in the serum carcinoembryonic antigen level and serum carbohydrate antigen 19-9 level. Core needle biopsy was performed, and histopathologic examination showed Cytokeratin 20 and CDX-2 positivity, compatible with rectal cancer. To our knowledge, this is the first case of a metastatic breast tumor arising from rectal carcinoma with BRAF mutation. Although breast metastasis is very rare event, the possibility of breast metastasis from extra mammary sites should be considered when the breast tumor is found in cancer treatment.

Purification and characterization of serine racemase from a hyperthermophilic archaeon, Pyrobaculum islandicum.

Pyrobaculum islandicum is an anaerobic hyperthermophilic archaeon that is most active at 100 degrees C. A pyridoxal 5'-phosphate-dependent serine racemase called Srr was purified from the organism. The corresponding srr gene was cloned, and recombinant Srr was purified from Escherichia coli. It showed the highest racemase activity toward L-serine, followed by L-threonine, D-serine, and D-threonine. Like rodent and plant serine racemases, Srr is bifunctional, showing high L-serine/L-threonine dehydratase activity. The sequence of Srr is 87% similar to that of Pyrobaculum aerophilum IlvA (a putative threonine dehydratase) but less than 32% similar to any other serine racemases and threonine dehydratases. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration analyses revealed that Srr is a homotrimer of a 44,000-molecular-weight subunit. Both racemase and dehydratase activities were highest at 95 degrees C, while racemization and dehydration were maximum at pH 8.2 and 7.8, respectively. Unlike other, related Ilv enzymes, Srr showed no allosteric properties: neither of these enzymatic activities was affected by either L-amino acids (isoleucine and valine) or most of the metal ions. Only Fe2+ and Cu2+ caused 20 to 30% inhibition and 30 to 40% stimulation of both enzyme activities, respectively. ATP inhibited racemase activity by 10 to 20%. The Km and Vmax values of the racemase activity of Srr for L-serine were 185 mM and 20.1 micromol/min/mg, respectively, while the corresponding values of the dehydratase activity of L-serine were 2.2 mM and 80.4 micromol/min/mg, respectively.

Effective enhancement of X-ray-induced apoptosis in human cancer cells with mutated p53 by siRNA targeting XIAP.

The X-chromosome-linked inhibitor of the apoptosis protein (XIAP) is known to be an inhibitory factor for caspase-3. The aim of our study was to see whether radiation-induced apoptosis is enhanced by RNA interference targeting the XIAP through an elevation of caspase-3 activity, and whether the effect of XIAP depression depends on the p53 status of cancer cells. Two types of transformed human cultured non-small cell lung cancer cells (H1299) were used: wild-type p53-transfected cells (H1299/wtp53) and mutated p53-transfected cells (H1299/mp53). When 21-mer siRNA targeting XIAP (XIAP-siRNA) was transfected into these cells using liposomes, a suppression of the constitutive XIAP protein expression was observed. XIAP-siRNA enhanced radiation sensitivity in H1299/wtp53 and in H1299/mp53 cells and was very effective in H1299/mp53 cells. Radiation-induced apoptosis and the activation of caspase-3 were more elevated by XIAP-siRNA in the H1299/mp53 cells than in H1299/ wtp53. These results suggest that XIAP-siRNA is a possible candidate for a radiation sensitizer in cancer radiotherapy, especially in cells with mutated p53.

Citrus kawachiensis Peel Powder Reduces Intestinal Barrier Defects and Inflammation in Colitic Mice.

The anti-inflammatory effect of Citrus kawachiensis peel powder was examined in a murine model of dextran sodium sulfate (DSS)-induced colitic mice. In addition to the whole powder, its ethanol extract rich in polyphenolic compounds and ethanol extraction residue rich in dietary fibers were used. The whole powder ameliorated the DSS-induced body weight loss (body weight changes on day 9, Control 108 ± 2, DSS 91 ± 4, DSS+whole peel powder 106 ± 1%, p < 0.05), colon shortening (colon length, Control 5.0 ± 0.1, DSS 3.9 ± 0.1, DSS+whole peel powder 4.7 ± 0.1 cm, p < 0.05), increased expression of pro-inflammatory cytokines (e.g., TNF-α, Control 1.0 ± 0.1, DSS 22.2 ± 5.8, DSS+whole peel powder 4.3 ± 1.5 arbitrary unit, p < 0.05), and decreased expression of colonic tight junctions (TJs) (e.g., occludin, Control 1.00 ± 0.07, DSS 0.21 ± 0.07, DSS+whole peel powder 0.70 ± 0.06 arbitrary unit, p < 0.05). The resolution of abnormalities barring the decreased expression of zonula occludens-2, junctional adhesion molecule-A, and claudin-7 by the extraction residue was comparable to that achieved using the powder (body weight change 107 ± 1%; colon length 4.7 ± 0.1 cm; TNF-α 4.1 ± 0.7; occludin 0.58 ± 0.06 arbitrary unit, p < 0.05). The ethanol extract alone did not have any influence on these abnormalities (body weight change 94 ± 2%; colon length 4.1 ± 0.1 cm; TNF-α 40.5 ± 9.0 arbitrary unit; occludin 0.18 ± 0.02 arbitrary unit, p < 0.05). The powder and ethanol extraction residue, but not ethanol extract, increased fecal acetic acid concentration (Control 4.9 ± 0.6, DSS 5.0 ± 0.9, DSS+whole peel powder 8.8 ± 1.8, DSS+ethanol extract 5.3 ± 0.8, DSS+ethanol extraction residue 12.5 ± 1.1 mmol/L, p < 0.05). Taken together, DFs in the ethanol extraction residue largely contributed to the peel powder-mediated reduction of TJ barrier defect and inflammation in colitic mice.

Alanine racemase from Helicobacter pylori NCTC 11637: purification, characterization and gene cloning.

The Helicobacter pylori NCTC 11637 alanine racemase gene, alr1, was cloned based on a putative alanine racemase gene, alr, of H. pylori 26695. The protein, Alr1, was purified to homogeneity from Escherichia coli MB2795 cells harboring the alr1 gene. The protein exclusively catalyzes the conversion of l-alanine to the d-isomer with K(m) and V(max) values of 100 mM and 909 mumol min(-1) mg(-1), respectively. The values are 16-fold higher than those for the reaction in the reverse direction. The molecular weight of Alr1 is 42,000 by SDS-PAGE, and 68,000 by gel-filtration analysis. The optimal pH and temperature are pH 8.3 and 37 degrees C, respectively, in good accordance with the characteristics shown by the alanine racemase purified from H. pylori NCTC 11637 cells. Pyridoxal 5'-phosphate was suggested to be the cofactor. The physiological function of Alr1 is discussed regarding energy production in the microbial cells.

The presence of high concentrations of free D-amino acids in human saliva.

Free neutral D-amino acids have previously been detected in human plasma, usually accounting for less than 2% of the total free amino acid concentration (D-amino acid ratio) [Nagata, Y., Masui, R., Akino, T., 1992a. The presence of free D-serine, D-alanine and D-proline in human plasma. Experientia 48, 986-988. Nagata, Y., Yamamoto, K., Shimojo, T., 1992b. Determination of D- and L-amino acids in mouse kidney by high-performance liquid chromatography. Journal of Chromatography 575, 147-152. Nagata, Y., Yamamoto, K., Shimojo, T., Konno, R., Yasumura, Y., Akino, T., 1992c. The presence of free D-alanine, D-proline and D-serine in mice. Biochimca et Biiophysica Acta 1115, 208-211]. In the present study to search for the source of free D-amino acids, D- and L-enantiomers of the major non-essential amino acids, i.e., the free form of serine, alanine, proline, aspartate and glutamate were analyzed by HPLC in human saliva, submandibular glands and oral epithelial cells. The D-enantiomer ratios to total of free alanine or proline were 35% and 20%, respectively, in saliva. The ratios of the other D-amino acids were less than 11%. The effect of ingested food and oral bacteria on the saliva amino acid levels was suggested to be insignificant. D-Alanine and d-aspartate were also detected in the submandibular gland in ratios up to 5%, and D-alanine and d-proline were found in oral epithelial cells in ratios of 18% and 5%, respectively. The submandibular gland and oral epithelial cells are suggested to be possible sources of the saliva D-alanine and D-aspartate.

Large cell neuroendocrine thymic carcinoma coexisting within large WHO type AB thymoma.

Large cell neuroendocrine carcinoma (LCNEC) is a rare type of thymic epithelial tumor. It is recognized as a different entity from other thymic tumors on account of it having a more aggressive biologic behavior and poor prognosis. We report an extremely rare case of a very small, "large cell neuroendocrine thymic carcinoma" coexisting within a large thymoma that could not be detected by usual biopsy. Surgery as the initial treatment has the significance of definitive diagnosis and curative treatment for LCNEC of the thymus. To make a successful differential diagnosis, application of detailed immunohistochemical stains may be of aid, since thymic epithelial tumor is not always morphologically homogenous.