An important new model universal oscillator proposed by Seelig which depends on substrate inhibition is considered. In a finite spatial domain with zero flux boundary conditions and in which the substrates can diffuse it is shown that diffusion-driven instability is possible and can result in finite amplitude spatial structures. Illustrative numerical results are presented which exhibit this behaviour.

Catalysis↗

PubMedDate not supplied

Experimental study on chemonucleolysis. With special reference to the change of intradiscal pressure.

The purpose of this study is to investigate mechanical change in the intervertebral disc after chemonucleolysis. Thirteen monkeys were used. After transperitoneal approach to the lumbar spine, 400 units of Discase was injected into each disc. The animals were killed 1 day; 1, 2, 3, 4, 6, and 12 weeks; and 1 year after chymopapain injection. Compression load was applied to the segment composed of a disc and adjacent vertebral bodies. Intradiscal pressure was measured simultaneously. A linear relationship was noticed between compression load and intradiscal pressure. In chymopapain-injected discs, the pre-existing pressure decreased or disappeared, and the increase of pressure for a given load was lower than that of the control. Our biomechanical study suggested that the decrease of intradiscal pressure as a possible mechanism of symptom relief in chemonucleolysis.

Animals↗

PubMedDate not supplied

Characterization of cytochrome P-450 2B6 in human liver microsomes.

A cytochrome P-450 (P-450) enzyme of the CYP2B subfamily was partially purified from human liver microsomes and characterized with respect to immunochemical properties, N-terminal amino acid sequence, and catalytic activities toward typical P-450 substrates. P-450 enzymes were monitored in chromatographic fractions by immunoblotting analysis using antibodies raised against a monkey P-450 2B, as well as several purified human P-450 enzymes. The final P-450 2B preparation thus obtained was contaminated with P-450 3A4, but an N-terminal amino acid sequence matching the sequence predicted from the CYP2B6 cDNA was obtained. The apparent M(r) of this protein was 48 kDa, and the migration on sodium dodecyl sulfate-polyacrylamide gel electrophoresis was the same as that of the P-450 2B6 protein expressed in a human lymphoblast cell line. Immunoblotting analysis of 50 human liver samples revealed that the protein band considered to be P-450 2B6 was detected in only 12 samples, with four of these having relatively high levels. Several activities toward typical P-450 substrates were determined in a reconstituted monooxygenase system containing partially purified P-450 2B6 and compared with those obtained using a highly purified preparation of P-450 3A4 enzyme; we found that most of the activities were similar in these preparations, except that the partially purified P-450 2B6 showed high rates of activation of the mutagens 6-aminochrysene and 3-methoxy-4-aminoazobenzene to genotoxic metabolites in Salmonella typhimurium NM2009 strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMedDate not supplied

Germinoma arising in the basal ganglia in early stage: CT and MR findings.

We report a patient with a germinoma originating in the left basal ganglia. Unenhanced computed tomography (CT) revealed a relatively well-defined high-density lesion, which was slightly enhanced with contrast medium. No tumor stain was noted on angiography. The mass showed hypointensity on T1-weighted magnetic resonance imaging (MRI), and heterogeneous hyperintensity on T2-weighted imaging. The lesion was homogeneously enhanced after the administration of Gd-DTPA. To our knowledge, the MR findings of basal ganglia germinoma have been retrospectively reviewed in just four reported cases, only two of which were examined with Gd-DTPA enhancement. The two cases revealed relatively large masses with cysts and peritumoral edema, and were slightly enhanced after the intravenous injection of Gd-DTPA. Our case was thought to be in the early stage, and its CT and MR findings were slightly different from those of previously reported cases.

Basal Ganglia Diseases↗