Second-site mutation of Ala-220 to Glu or Asp suppresses the mutation of Asp-285 to Asn in the transposon Tn10-encoded metal-tetracycline/H+ antiporter of Escherichia coli

A carboxyl group of Asp-285 is essential for tetracycline/H+ antiport mediated by the transposon Tn10-encoded metal-tetracycline/H+ antiporter (TetA) of Escherichia coli (Yamaguchi, A., Akasaka, T., Ono, N., Someya, Y., Nakatani, M., and Sawai, T. (1992) J. Biol. Chem. 267, 7490-7498). Spontaneous tetracycline resistance revertants were isolated from E. coli cells carrying the Asn-285 mutant tetA gene. All of the revertants were due to the second-site mutation at codon 220 of GCG (Ala) to GAG (Glu). The Km value of the tetracycline transport mediated by the revertant TetA protein was about 4-fold higher than that of the wild-type, indicating that the revertant is a low affinity mutant. A Glu-220 and Asn-285 double mutant constructed by site-directed mutagenesis showed the same properties as the revertants, confirming that the mutation of Ala-220 is solely responsible for the suppression. The Asp-220 mutation of the Asn-285 mutant resulted in a lower level of restoration of the tetracycline resistance and the transport activity than in the case of the Glu-220 mutation. A single mutation replacing Ala-220 with Glu or Asp caused about a 2-4-fold decrease in the tetracycline resistance, but no crucial change in the transport activity. It is not likely that Glu-220 is required for a charge-neutralizing salt bridge because an unpaired negative charge in a Glu-220 or Asp-220 single mutant did not cause a serious change in the activity. An alternative explanation is reasonable; Asp-285 directly contributes to the binding of a cationic substrate, metal-tetracycline chelation complex, or proton, and an acidic residue at position 220 can take over the role of Asp-285.     

Appearance of fosfomycin resistant Rahnella aquatilis clinically isolated in Japan

Among recent clinical isolates in Japan, strain CU264 was discovered which formed unusual colonies. This strain was identified as Rahnella aquatilis which is usually found in water. The antibiotic susceptibilities against tetracycline, carbenicillin, chloramphenicol, streptomycin, kanamycin, gentamicin, sulphonamide, neomycin, fosfomycin, rifampicin, norfloxacin and nalidixic acid, were investigated. The result demonstrated that the strain was highly resistant to fosfomycin only. It was further shown that this resistance was transmissible with low frequency to Serratia marcescens whereas it was not transmissible to Escherichia coli.     

Resistance to macrolide antibiotics found in methicillin-resistant Japanese clinical isolates of Staphylococcus aureus in 1996

OBJECTIVE: To study the effect of sufficient energy intake, by means of the protocolized administration of naso-gastric tube feeding, on the nutritional status of a child with cancer. DESIGN: A comparative experimental study. SETTING: Tertiary care at the Centre for Pediatric Oncology, South East Netherlands, University Hospital, Nijmegen. SUBJECTS: Seven children, newly diagnosed with cancer, were included in the experimental study and all completed the trial period. Fourteen patients were included in the retrospective study. They were randomly chosen from a group of patients previously treated for a malignancy at our department and who had received naso-gastric tube feeding for at least 16 weeks. INTERVENTION: Protocolized (experimental group) vs non-protocolized (retrospective group) administration of naso-gastric tube feeding over a period of 16 weeks. The main difference was the amount of tube feeding administered. In addition to energy from other foods, children in the experimental group received 106+/-13% of their total daily energy requirements (TDER) by means of tube feeding, whereas children in the retrospective group had received 75+/-24%. MAIN OUTCOME MEASURES: Weight as a percentage of weight for height according to the 50th percentile of a healthy reference population=ideal weight. RESULTS: Weight, expressed as a percentage of the ideal weight, increased significantly in the experimental group (18.2 8.4; P=0.01) and the retrospective study group (5.2 7.3; P=0.001). However, the increase was statistically significant in favour of the experimental group (P=0.003), in which all the children reached their ideal weight, compared to 21% in the retrospective group. CONCLUSION: Aggressive protocolized nutritional intervention during the intensive phase of anti-cancer treatment, in the form of naso-gastric tube feeding that provides the child's total daily energy requirements, results in considerable improvement in the nutritional status.     

Comparison in survival between hepatic metastases of gastric and colorectal cancers

BACKGROUND/AIM: The outcome after hepatectomy and non-surgical treatment of liver metastases from gastric and colorectal malignancies are reported. METHODOLOGY: Between April 1988 and March 1994, 176 patients with metastatic liver cancer were treated at the First Department of Surgery, Kyoto Prefectural University of Medicine Hospital. RESULTS: All patients received multi-disciplinary treatment, and 51 underwent hepatectomy. The survival after hepatectomy for metastatic liver cancer from a colorectal primary was better than that for gastric cancer. The survival after hepatic arterial infusion (HAI) therapy for metastases from gastric cancer was better than that for colorectal cancer. CONCLUSION: Surgical resection may be the best treatment for liver metastases from colorectal cancer. HAI may be a better option for liver metastases from gastric cancer.     

Clinical outcome of surgical treatment for invasive early colorectal cancer in Japan

BACKGROUND/AIMS: Despite the high frequency of early colorectal cancer, little is known about the clinicopathologic features of invasive early colorectal cancer for which endoscopic polypectomy is not indicated. We wanted to determine the clinicopathologic features of these early colorectal cancers. MATERIALS AND METHODS: From 1973 to 1994, a total of 728 patients with colorectal cancer were reviewed retrospectively from hospital records. The clinicopathologic features of the 90 invasive early colorectal cancer patients who underwent major surgeries were compared with those of 626 patients with advanced colorectal cancer. RESULTS: The frequency of early colorectal cancer increased significantly from the periods 1973-1979 to 1990-1994: 0% in the former period and 18.3% in the later period. Minimally invasive surgery was chosen more frequently for the treatment of early colorectal cancers than for the treatment of advanced cancers (p < 0.005). Lymph node metastasis, lymph vessel invasion, and vascular invasion were more prevalent in advanced cancer cases than in early cancer cases (p < 0.005). Lymph node metastasis was found in 7 patients with early colorectal cancer (7.8%). There was no difference in histologic type between the early and advanced colorectal cancers. The 5-year survival rates of early colorectal cancer patients were higher than those of advanced cancer patients: 97.5% in early colon cancer patients; 93.5% in early rectal cancer patients; 59.8% in advanced colon cancer patients; 55.4% in advanced rectal cancer patients. Three early colorectal cancer patients died of recurrence. CONCLUSION: Minimally invasive surgery such as laparoscopic colectomy should be performed on patients with invasive early colorectal cancer when it is impossible for the cancer to be removed by endoscopic polypectomy.     

A survey of a functional amino acid of class C beta-lactamase corresponding to Glu166 of class A beta-lactamases

The class C beta-lactamase of Citrobacter freundii GN346 is a typical cephalosporinase comprising 361 amino acids. The aspartic acid at position 217 and glutamic acid at position 219 in this beta-lactamase were, respectively, previously shown not to be the counterpart of Glu166 (ABL166) in class A beta-lactamases, even though sequence alignment of class A and C enzymes strongly suggested this possibility [(1990) FEBS Lett. 264, 211-214; (1990) J. Bacteriol. 172, 4348-4351]. We tried again to assign candidates for the counterpart of Glu166 through sequence alignment based on other criteria, the glutamic acids at positions 195 and 205 in the class C beta-lactamase being selected. To investigate this possibility, these two glutamic acids were changed to glutamine, lysine or alanine, respectively. All the mutant enzymes showed more than 50% of the activity of the wild-type enzyme, indicating that the possibility was ruled out. These results strongly suggested the possibility that the class C beta-lactamase lacks a functional acidic residue corresponding to Glu166 in class A enzymes.     

Clinical and pathological significance of numerical aberrations of chromosomes 11 and 17 in colorectal neoplasms

Numerical chromosome aberrations by interphase cytogenetic analysis have been reported in a few samples of colorectal neoplasms. No studies have defined a distinct relationship between these aberrations and clinicopathological features. To investigate the chromosome aberrations as a marker of invasiveness or prognosis, we conducted an interphase cytogenetic study using fluorescence in situ hybridization and examined 142 colorectal neoplasms consisting of 15 adenomas and 127 cancers. The target chromosomes were chromosomes 11 and 17. We also evaluated the nuclear DNA content as detected by flow cytometry, analyzed the relationship between the frequency of aneusomy and clinicopathological features, and examined the survival rate in these patients. The loss of chromosome 11 was observed in 31% of adenomas, whereas in cancers DNA aneuploidy was observed in 63% of cases, a gain of chromosome 17 was observed in 63% of cases, and a gain of chromosome 11 was observed in 42% of cases. Numerical chromosome aberrations in diploid DNA were also observed. Increased depth of invasion (>/=T3) and advanced Dukes' stage (>/=B) of malignant tumors were associated with a higher frequency of a gain of chromosome 11 (P < 0.01 and P < 0.05, respectively). Increased depth of invasion (>/=T2) in cancers was associated with a higher frequency of a gain of chromosome 17 (P < 0.05). Multivariate analysis of postoperative survival showed that a loss or gain of chromosome 11 was independently associated with a poor prognosis (P < 0.05). Numerical chromosome aberrations appear prior to the alteration of nuclear DNA content as detected by flow cytometry and influence the progression of colorectal cancers. Aneusomy of chromosome 11 is associated with poor postoperative prognosis of primary colorectal cancers.     

Anomalies of the tracheobronchial tree in patients with esophageal atresia

Bone marrow examination revealed a lipid-laden histiocytosis in seven patients undergoing long-term total parenteral nutrition necessitated by extensive short-bowel surgical resection. Clinical abnormalities occurred during this treatment which required bone marrow examination. These included hepatosplenomegaly and peripheral blood cytopenia; the median time to the detection of these abnormalities was 64 months. The most striking change within the bone marrow was the presence of many pigment-laden histiocytes which had the typical morphology of sea-blue histiocytes seen in the so-called idiopathic sea-blue histiocyte syndrome. The occurrence of sea-blue histiocytosis in the bone marrow in association with long-term parenteral nutrition for short-bowel syndrome has not, to our knowledge, been reported previously and should now be considered in the differential diagnosis of bone marrow sea-blue histiocytosis.     

Void formation in 10Cr-2Mo ferritic steel irradiated in HFIR

Microstructural evolution of a 10Cr-2Mo ferritic steel was investigated after irradiation in the High Flux Isotope Reactor (HFIR) at 500°C and doses up to 57 dpa. About 300 appm of helium was also produced after 57 dpa because the steel contained 1 wt% Ni. Many tiny helium bubbles were observed in a specimen irradiated to 34 dpa, either inside of or adjacent to particles of radiation-produced x- and Laves-phase precipitates. By contrast, after 57 dpa many of the tiny bubbles had developed into larger voids. Most of the voids were associated with radiation-induced x-phase particles.