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Biomedical subjects

H Niki

Publications and source records attributed to H Niki.

At least 19 recordsLinked to original sources
PubMed1992

E.coli MukB protein involved in chromosome partition forms a homodimer with a rod-and-hinge structure having DNA binding and ATP/GTP binding activities.

mukB mutants of Escherichia coli are defective in the correct partitioning of replicated chromosomes. This results in the appearance of normal-sized anucleate (chromosome-less) cells during cell proliferation. Based on the nucleotide sequence of the mukB gene, the MukB protein of 177 kDa was predicted to be a filamentous protein with globular domains at the ends, and also having DNA binding and nucleotide binding abilities. Here we present evidence that the purified MukB protein possesses these characteristics. MukB forms a homodimer with a rod-and-hinge structure having a pair of large, C-terminal globular domains at one end and a pair of small, N-terminal globular domains at the opposite end; it tends to bend at a middle hinge site of the rod section. Chromatography in a DNA-cellulose column and the gel retardation assay revealed that MukB possesses DNA binding activity. Photoaffinity cross-linking experiments showed that MukB binds to ATP and GTP in the presence of Zn2+. Throughout the purification steps, acyl carrier protein was co-purified with MukB.

Acyl Carrier Protein↗
PubMed1992

Characterization of high molecular weights of complexes and polymers of cytoplasmic proteins in Escherichia coli.

To search for filamentous polymers of cytoplasmic proteins of Escherichia coli, high molecular weights (> 670 kDa) of protein complexes of cell extracts were fractionated by gel filtration and ion-exchange column chromatography. Proteins of 100, 77 and 52 kDa were co-purified. The 100- and 52-kDa proteins were identified to be pyruvate dehydrogenase and lipoamide dehydrogenase, respectively, by determining the N-terminal amino acid sequences. Experimental results indicate that the 77-kDa protein is identical to dihydrolipoamide acyltransferase. The 100-kDa protein was found to be identical to the 100-kDa protein described by Tomioka (1991), and was related to the formation of filaments and sheets in the presence of 100 mM KCl. However, neither long filaments nor sheets were observed in our sample containing these enzymes, which was not consistent with Tomioka's conclusion. Another 100-kDa protein which forms spirosome-like particles was purified and identified to be alcohol dehydrogenase based on the N-terminal sequence.

Acyltransferases↗
PubMed1992

Identification and characterization of the smbA gene, a suppressor of the mukB null mutant of Escherichia coli.

The mukB gene encodes a protein involved in chromosome partitioning in Escherichia coli. To study the function of this protein, we isolated from the temperature-sensitive mukB null mutant and characterized 56 suppressor mutants which could grow at 42 degrees C. Ten of the mutants also showed cold-sensitive growth at 22 degrees C. Using one of the cold-sensitive mutants as host, the wild type of the suppressor gene was cloned. The cloned suppressor gene complemented all of the 56 suppressor mutations. DNA sequencing revealed the presence of an open reading frame of 723 bp which could encode a protein of 25,953 Da. The gene product was indeed detected. The previously undiscovered gene, named smbA (suppressor of mukB), is located at 4 min on the E. coli chromosome, between the tsf and frr genes. The smbA gene is essential for cell proliferation in the range from 22 to 42 degrees C. Cells which lacked the SmbA protein ceased macromolecular synthesis. The smbA mutants are sensitive to a detergent, sodium dodecyl sulfate, and they show a novel morphological phenotype under nonpermissive conditions, suggesting a defect in specific membrane sites.

Amino Acid Sequence↗
PubMed1992

Lupus nephritis associated with bacterial panperitonitis and lung alveolar hemorrhage.

A 36-year-old woman was admitted to the hospital with the diagnosis of nephrotic syndrome due to lupus nephritis. The patient had panperitonitis caused by Staphylococcus aureus as a complication, and an emergency laparotomy was performed. After the operation, the patient developed a massive lung alveolar hemorrhage. Methylprednisolone pulse therapy showed a marked effect on the lung hemorrhage. It is known that lung alveolar hemorrhages associated with systemic lupus erythematosus have a very high mortality; the present case is relatively rare because of the good response to steroid pulse therapy.

Adult↗
PubMed1991

Eosinophilic peritonitis responding to treatment with glycyrrhizin.

A 63-year-old man with diabetes mellitus for 15 years was admitted to our hospital in 1990 because of end-stage renal failure. Five days after beginning continuous ambulatory peritoneal dialysis (CAPD) he developed an eosinophilic peritonitis (EP). With protein loss in the dialysate and a decreased serum albumin level, the patient developed ankle edema. The patient was treated with glycyrrhizin, and his EP resolved. It is suggested that an allergic background may play an important role in the development of EP in patients on CAPD.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1979

Prefrontal and cingulate unit activity during timing behavior in the monkey.

Single unit activity was recorded from the dorsolateral prefrontal cortex and the anterior cingulate cortex while monkeys were performing a modified differential reinforcement of long latencies (DRLL) task. A total of 252 prefrontal units and 218 anterior cingulate units showed an obvious change in discharge rate (increase or decrease) in association with one or more of the events of a DRLL task. Related units were classified into 3 main groups: S--R event units, reward-error units, and timing units. S--R event units consisted of three subtypes: stimulus-related, response-related, and stimulus--response-related units. Reward-error units contained reward-related units and error-recognition units. Error-recognition units showed a vigorous increase in firing only after incorrect responses. These units were also responsive to omission of reinforcement on correct trials. Three types of timing units were distinguishable. The first one showed an anticipatory change prior to stimulus onset, and the second one exhibited a gradual anticipatory change preceding the time of responding. The third one manifested a sustained change during delay and an abrupt cessation of change in firing at the time of response initiation.

Animals↗
PubMed1978

Effect of alpha-D-mannose and equilibrated D-mannose of insulin release.

The effects on insulin release of alpha-D-mannose and equilibrated D-mannose were studied in the isolated perfused rat pancreas. Although phosphomannose isomerase, in contrast to phosphoglucose isomerase, is stereospecific for beta-D-mannose-6-phosphate, the alpha anomer of D-mannose (2 mg/ml) was significantly more effective than equilibrated D-mannose in stimulating insulin release. The finding does not seem to accord with the view that the signal for hexose-induced insulin release arises from the glycolytic pathway, and suggests the existence of the stereospecific glucoreceptor(s) on the pancreatic B-cell membrane.

Animals↗
PubMed1977

Tritiated thymidine autoradiographic study on the origin and renewal of argentaffin cells in the pyloric gland of hamsters.

The origin and renewal of the argentaffin cells in the pyloric glands of hamsters were studied by flash, cumulative and pulse labelling autoradiography with 3H-thymidine. The argentaffin cells were identified by the Diazo Method using Fast Red B Salt. By flash labelling autoradiography, it was shown that the argentaffin cells located from the middle to the lower level of the pyloric mucosa were not labelled with 3H-thymidine, indicating that this cell type has no proliferative activity. On the 10th and the 20th day of cumulative labelling, 31% and 63% of the argentaffin cells in the gland were found to be labelled, respectively. The labelled argentaffin cells were concentrated in the upper part of the gland (around the region of the isthmus), and no label was found over nuclei of the cells at the lowermost level of the gland. These labelled cells were shown to undergo a downward migration in the days following pulse labelling. They were replaced by unlabelled (and weakly or very weakly labelled) cells which arose at the region of the isthmus. The argentaffin cells in the pyloric gland are thought to arise from epithelial precursor cells at the region of the isthmus. The labelled argentaffin cells in the gland were found to decrease in number almost exponentially after pulse labelling. This indicates that the life span of argentaffin cells is not fixed, but their renewal conforms to the "random loss system". The half time of turnover of this cell population was 15 days on average.

Animals↗
PubMed1977

Enzymatic oxidation of isethionate to sulfoacetaldehyde in bacterial extract.

Isethionate degradation in a bacterial extract was shown by the isolation of enzymes and by identification of an intermediate to take place in two steps; dehydrogenation to sulfoacetaldehyde and desulfonation leading to the formation of sulfite and acetate. The enzyme responsible for isethionate oxidation in the presence of FAD was particulate in nature and a solubilized preparation obtained by extraction with buffer of low ionic strength had oxidizing activities against only isethionate and n-butanol among compounds tested. The enzyme was inhibited by thiol and carbonyl reagents.

Acetaldehyde↗
PubMed1976

Prefrontal unit activity and delayed response: relation to cue location versus direction of response.

Two monkeys were trained to perform 3 kinds of spatial tasks (right-left DR, up-down DR, and conditional position discrimination with delay). In the conditional position task, the animal was required to respond to the right (left) choice key when the cue had been presented on the upper (lower) position. Single unit activity was recorded from the principalis area of the dorsolateral prefrontal cortex while the animal was performing the tasks. Once a differential delay unit (i.e., unit showing specificity during the delay period for two kinds of trials) was found in right-left DR (or up-down DR), the same unit was tested in the other tasks. A total of 32 differential delay units were investigated sufficiently to allow comparison of all 3 conditions. The results indicate that there are two types of differential delay units. The first type showed a clear dependence on the cue location, while the second type was related to the direction of the impending response. Activity of the second type of differential delay unit during the delay period served to predict the occurrence of errors, whereas this relation between unit discharge and correct or incorrect responses was not seen for the first type of differential delay unit.

Animals↗