Cardiovascular response to lower body negative pressure before and after 20 days horizontal bed rest

To evaluate the effects of 20 days bed rest (BR) on cardiovascular system in normal subjects, left ventricular (LV) echocardiography and vascular ultrasound of the common carotid artery and abdominal aorta were performed during rest and a supine lower body negative pressure (LBNP) test in 14 healthy volunteers (mean age: 22 years) before and after BR. After BR, heart rates (HR) at rest and during LBNP (-40 mmHg) increased. In contrast, LV dimensions, stroke volume, and blood pressures decreased both at rest and during LBNP. Also LBNP tolerance time decreased after BR. Although resting cardiac output (CO) and abdominal aortic flow decreased after bed rest, CO and abdominal aortic flow were unchanged during LBNP comparing before and after BR. Common carotid artery flows both at rest and during LBNP showed no change after BR. LBNP did not increase HR before BR, but increased HR prominently after BR. In conclusion, LBNP tolerance time and LV size during LBNP decreased after BR, suggesting orthostatic intolerance due to a decreased blood volume. However, CO and flow in the abdominal aorta and common carotid artery during LBNP were similar before and after BR due to a compensatory increase after BR.     

Effects of 20 days horizontal bed rest on mechanical efficiency during steady state exercise at mild-moderate work intensities in young subjects

Delta efficiency(DE) at mild-moderate (31%-56% of maximum oxygen uptake) bicycle exercise in the upright sitting and in the supine position was measured in 10 young males and 5 females before and after 20 days bed rest (BR). Total muscle mass in the both legs(TMML) were measured by dual-energy x-ray absorptiometry. After BR, oxygen uptake decreased at all intensities during upright exercise and at 100 W during supine exercise (p<0.05) in the males but cardiac output (acetylene rebreathing) was almost unchanged. As defined as increase in work over the corresponding increase in energy liberation, DE significantly increased by 20.1% during upright exercise and 18.4% during supine exercise in males, but unchanged in females. TMML was decreased in both males and females. The differences in DE between males and females could not be explained in the present study. One possibility might be that the decreased DE was due to a simultaneous decrease in slow twitch muscle fiber content which might be responsible for the decreased TMML induced by BR in the males.     

Effects of 20 days bed rest on mechanical efficiency during upright cycling and leg muscle mass in young males

Delta efficiency defined as increase in work over the corresponding increase in energy liberation (delta work/delta energy) may be used to express the efficiency of working muscles under standard conditions where work is performed with similar changes in muscle length, identical pedal revolution frequencies, and contraction-to-relaxation ratios. The Delta efficiency is probably the most valid measure of the efficiency of muscular work, so it may be influenced by the difference in distribution and/or density of muscle fiber types in exercising muscles. It has been reported that after bed rest of 7-14 days, not only maximum oxygen uptake (VO2 max) but also oxygen uptake (VO2) at 3-min submaximal upright exercise decreased. However, the decrease might be apparent, and the mechanical efficiency might be unchanged. On the other hand, muscle mass of bicycling legs was decreased after continuous horizontal bed rest of 10 days and 20 days. Because the decreased muscle mass is probably related to decrease in the density of the slow twitch muscle fibers (ST-fiber), the decrease in submaximal VO2 during bicycle exercises after bed rest may result from a decrease in ST-fiber mass. Therefore, it could be hypothesized that the mechanical efficiency should increase during upright exercise because of the relative increase in amount of more efficient fast twitch muscle fibers (FT-fiber) than ST fibers in exercising muscles. The purpose of the present study was to investigate whether delta efficiency in working muscle is influenced by the decrease in muscle mass after 20 days horizontal bed rest in young males.     

Elevation of hepatic levels of metallothionein during experimental carcinogenesis

From the early stage of pancreatic adenocarcinoma in hamsters and also of hepatocellular carcinoma in rats, induced by treatment withN-nitrosobis (2-oxopropyl)amine and 3′-methyl-dimethylaminoazobenzene, respectively, hepatic levels of metallothionein (MT) were found to be continuously elevated. In the hepatoma-induced rats, this elevation preceded that of serum γ-glutamyl transpeptidase activity, a marker enzyme for hepatocellular carcinoma. These results indicate that, in the course of chemical carcinogenesis, the elevation of hepatic MT level occurred and continued from the early stage of carcinogenesis. This type of elevation of hepatic MT level was also observed in lung metastasis-induced mice. On the other hand, in rats with pancreatitis caused by the administration of deoxycholate, the hepatic level of MT rose only transiently.     

A novel FAD-protein that allows effective reduction of methyl viologen by NADH (NADH-methyl viologen reductase) from photosynthetic bacterium, Rhodospirillum rubrum: purification and characterization

It was found that the cytoplasm of light-grown cells of Rhodospirillum rubrum could catalyze the reduction of methyl viologen (MV) (Em, 7 = -0.44 V) by NADH and NADPH. In the present study, the enzyme capable of catalyzing MV reduction by NADH (NADH-MV reductase) was purified 1,500-fold from an extract of cells with a yield of 4.4%. The purification procedure comprised (NH4)2SO4 fractionation, and chromatographies on Sepharose CL-6B, DEAE-Sepharose CL-6B, phenyl-Sepharose CL-4B, Blue-Cellulofine, and TSK-Gel G3000SW. Two NADPH-MV reductases were separated during the purification. The NADH-MV reductase obtained was nearly homogeneous, as judged on polyacrylamide gel electrophoresis both in the presence and absence of sodium dodecyl sulfate. The enzyme has a molecular weight of 220,000 and an isoelectric point of 4.8; it is composed of four subunits with a molecular weight of 57,000, and is bound with about 1 mol FAD/mol subunit. The activity is optimum at pH 8. The Km values for NADH and MV are 115 microM and 1.3 mM, respectively, with a molecular activity of 13,000 min-1. The activity was stimulated 2.4-fold in the presence of 20-100 mM ammonium ions. The enzyme also catalyzed the reduction of benzyl viologen, methylene blue and 2,6-dichlorophenol-indophenol (Em, 7 = -0.36, +0.011, and +0.217 V, respectively) at comparable rates. The ratios of the activity with NADH to that with NADPH were 80, 133, 41, and 5.5 with MV, benzyl viologen, methylene blue and 2,6-dichlorophenolindophenol, respectively. The enzyme was significantly stable in the presence of both 5mM 2-mercaptoethanol and 20% (w/v) glycerol. The activity was not appreciably influenced by the presence of 2 M urea, although the reagent caused dissociation to the subunits.     

The C-terminal Domain of the Long Form of Cellular FLICE-inhibitory Protein (c-FLIPL) Inhibits the Interaction of the Caspase 8 Prodomain with the Receptor-interacting Protein 1 (RIP1) Death Domain and Regulates Caspase 8-dependent Nuclear Factor κB (NF-κB) Activation

Caspase 8 plays an essential role in the regulation of apoptotic and non-apoptotic signaling pathways. The long form of cellular FLICE-inhibitory protein (c-FLIP_L) has been shown previously to regulate caspase 8-dependent nuclear factor κB (NF-κB) activation by receptor-interacting protein 1 (RIP1) and TNF receptor-associated factor 2 (TRAF2). In this study, the molecular mechanism by which c-FLIP_L regulates caspase 8-dependent NF-κB activation was further explored in the human embryonic kidney cell line HEK 293 and variant cells barely expressing caspase 8. The caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone greatly diminished caspase 8-dependent NF-κB activation induced by Fas ligand (FasL) when c-FLIP_L, but not its N-terminal fragment c-FLIP(p43), was expressed. The prodomain of caspase 8 was found to interact with the RIP1 death domain and to be sufficient to mediate NF-κB activation induced by FasL or c-FLIP(p43). The interaction of the RIP1 death domain with caspase 8 was inhibited by c-FLIP_L but not c-FLIP(p43). Thus, these results reveal that the C-terminal domain of c-FLIP_L specifically inhibits the interaction of the caspase 8 prodomain with the RIP1 death domain and, thereby, regulates caspase 8-dependent NF-κB activation.     

Identification of a novel fatty acid elongase with a wide substrate specificity from arachidonic acid-producing fungus <Emphasis Type="Italic">Mortierella alpina</Emphasis> 1S-4

The isolation and characterization of a gene (MALCE1) that encodes a fatty acid elongase from arachidonic acid-producing fungus Mortierella alpina 1S-4 are described. MALCE1 was confirmed to encode a fatty acid elongase by its expression in yeast Saccharomyces cerevisiae, resulting in the accumulation of 18-, 19-, and 20-carbon monounsaturated fatty acids and eicosanoic acid. Furthermore, the MALCE1 yeast transformant efficiently elongated exogenous 9-hexadecenoic acid, 9,12-octadecadienoic acid, and 9,12,15-octadecatrienoic acid. The MALCE1 gene-silenced strain obtained from M. alpina 1S-4 exhibited a low content of octadecanoic acid and a high content of hexadecanoic acid, compared with those in the wild strain. The enzyme encoded by MALCE1 was demonstrated to be involved in the conversion of hexadecanoic acid to octadecanoic acid, its main role in M. alpina 1S-4.