Variations in the light-induced suppression of nocturnal melatonin with special reference to variations in the pupillary light reflex in humans

The purpose of the present study was to elucidate the existence of individual differences of pupil response to light stimulation, and to confirm the reproducibility of this phenomenon. Furthermore, the relationship between the individual differences in nocturnal melatonin suppression induced by lighting and the individual differences of pupillary light response (PLR) was examined. The pupil diameter and salivary melatonin content of 20 male students were measured at the same period of time (00:00-02:30 hr) on different days, accordingly. Illumination (530 nm) produced by a monochromatic light-emitting diode (LED) was employed as the light stimulation: pupil diameter was measured with 4 different levels of illuminance of 1, 3, 30 and 600 lux and melatonin levels were measured at 30 and 600 lux (respective controls were taken at 0 lux). Oral temperature, blood pressure and subjective index of sleepiness were taken in experiments where melatonin levels were measured. Changes of the pupil diameter in response to light were expressed as PLR and light-induced melatonin suppression was expressed as a control-adjusted melatonin suppression score (control-adjusted MSS), which was compared to the melatonin level measured at 0 lux. In the PLR, the coefficients of variation obtained at 30 lux or less were large (51.5, 45.0, 28.4 and 6.2% at 1, 3, 30 and 600 lux, respectively). Correlations of illuminance of any combination at 30 lux or less were statistically significant at less than 1% level (1 vs. 3 lux: r=0.68; 1 vs. 30 lux: r=0.64; 3 vs. 30 lux: r=0.73), which showed the reproducibility of individual differences. The control-adjusted MSS at 600 lux (-1.14+/-1.16) was significantly (p<0.05) lower than that registered at 30 lux (-0.22+/-2.12). PLR values measured at 30 and 600 lux were then correlated with control-adjusted MSS; neither indicated a significant linear relationship. However, the control-adjusted MSS showed around 0 under any of the illuminance conditions in subjects with high PLR. In control-adjusted MSS of low values (i.e., melatonin secretions were easily suppressed), subjects indicated typically low PLR. In subjects with low control-adjusted MSS (n=3), characteristic changes in the autonomic nervous system, such as body temperature and blood pressure, were noted in subjects exposed to low illuminance of 30 lux. The fact that the relationship between PLR and control-adjusted MSS portray a similar pattern even under different luminance conditions suggests that MSS may not be affected in those with high PLR at low illuminance, regardless of the illuminance condition.     

Role of AKT in cyclic strain-induced endothelial cell proliferation and survival

Endothelial cells (ECs) are exposed to repetitive cyclic strain (CS) in vivo by the beating heart. The aim of this study was to assess the influence of CS amplitude and/or frequency on EC proliferation and survival and to determine the role of AKT in CS-induced EC proliferation and survival. Cultured bovine aortic ECs were exposed to 10% strain at a frequency of 60 (60 cpm-10%) or 100 (100 cpm-10%) cycles/min or 15.6% strain at a frequency of 60 cycles/min (60 cpm-15.6%). AKT, glycogen synthase kinase (GSK)-3, BAD, and cleaved caspase-3 were activated by CS in ECs. Increasing the magnitude or frequency of strain resulted in an earlier phosphorylation of GSK-3, although the magnitude of phosphorylation was similar. After CS at 60 cpm-10% for 24 h, the number of nontransfected ECs was significantly increased by 8.5% (P < 0.05). We found that the number of apoptotic ECs was slightly decreased with exposure to CS. ECs transfected with kinase-dead AKT (KA179) as well as plasmids containing a point mutation in the pleckstrin homology domain of AKT (RC25) not only prevented AKT, GSK-3, and BAD phosphorylation but also inhibited the CS-induced increase in cell number as well as the CS-induced protection against apoptosis (both P < 0.05). The ratio of 5'-bromo-2'-deoxyuridine-positive cells was increased when ECs transfected with RC25 and KA179 as well as nontransfected ECs and ECs transfected with Lipofectamine 2000 were exposed to CS. We conclude that AKT is important in enhancing the survival of ECs exposed to CS but is not involved in EC proliferation. apoptosis; glycogen synthase kinase     

N-glycan structures of murine hippocampus serine protease, neuropsin, produced in Trichoplusia ni cells

N-glycans of neuropsin (serine protease in the murine hippocampus) expressed in Trichoplusia ni cells were released from the glycopeptides by digestion with glycoamidase A (from sweet almond), and the reducing ends of the oligosaccharides were reductively aminated with 2-aminopyridine. The derivatized N-glycans were separated and structurally identified by a two dimensional high-performance liquid chromatography (HPLC) mapping technique on two kinds of HPLC columns. Fourteen different major N-glycan structures were identified, of which 6 were high-mannose type (9.1%), and the remaining 8 were paucimannosidic type. The presence of insect specific N-glycan structures containing both 1,3- and 1,6- di-fucosylated innermost N-acetylglucosamine residue (23.3%), as below, was also confirmed by 600 MHz ¹H-NMR spectroscopy.     

Gene-expression profiling reveals down-regulation of equilibrative nucleoside transporter 1 (ENT1) in Ara-C-resistant CCRF-CEM-derived cells

We have investigated the mechanism of resistance of leukemia cells to Ara-C using an in-house cDNA microarray designed for the analysis of leukemia cells. We produced Ara-C-resistant cells from the CCRF-CEM (acute lymphoblastic leukemia) cell line and compared their gene-expression profile with that of wild-type cells. The adenosine deaminase (ADA) gene was highly up-regulated in Ara-C-resistant cells, while equilibrative nucleoside transporter 1 (ENT1) and several cell-cycle-related genes were down-regulated. Of all these genes, ENT1 seemed the most likely to be relevant to Ara-C resistance. To investigate the role of ENT1 in Ara-C-resistant cells, we transfected the cells with the gene. ENT1-transfected Ara-C-resistant cells resembled wild-type CCRF-CEM cells more closely than untransfected Ara-C-resistant cells in terms of growth rate, Ara-C-uptake characteristics, and ADA expression levels. The down-regulation of the ENT1 gene is expected to result in nucleotide deficiency in addition to blockage of Ara-C influx. Accordingly, Ara-C-resistant cells showed low growth rates, which were restored by transfection with ENT1. These low growth rates were also correlated with the phosphorylation level of cell-cycle checkpoint kinase 2. In this study we identified down-regulation of ENT1 as the factor responsible for Ara-C resistance, and this knowledge may be used to devise a clinical regimen that will overcome the resistance.     

Pathophysiology of orthostatic hypotension after bed rest: paradoxical sympathetic withdrawal

Although orthostatic hypotension is a common clinical syndrome after spaceflight and its ground-based simulation model, 6 degrees head-down bed rest (HDBR), the pathophysiology remains unclear. The authors' hypothesis that a decrease in sympathetic nerve activity is the major pathophysiology underlying orthostatic hypotension after HDBR was tested in a study involving 14-day HDBR in 22 healthy subjects who showed no orthostatic hypotension during 15-min 60 degrees head-up tilt test (HUT) at baseline. After HDBR, 10 of 22 subjects demonstrated orthostatic hypotension during 60 degrees HUT. In subjects with orthostatic hypotension, total activity of muscle sympathetic nerve activity (MSNA) increased less during the first minute of 60 degrees HUT after HDBR (314% of resting supine activity) than before HDBR (523% of resting supine activity, P < 0.05) despite HDBR-induced reduction in plasma volume (13% of plasma volume before HDBR). The postural increase in total MSNA continued during several more minutes of 60 degrees HUT while arterial pressure was maintained. Thereafter, however, total MSNA was paradoxically suppressed by 104% of the resting supine level at the last minute of HUT (P < 0.05 vs. earlier 60 degrees HUT periods). The suppression of total MSNA was accompanied by a 22 +/- 4-mmHg decrease in mean blood pressure (systolic blood pressure <80 mmHg). In contrast, orthostatic activation of total MSNA was preserved throughout 60 degrees HUT in subjects who did not develop orthostatic hypotension. These data support the hypothesis that a decrease in sympathetic nerve activity is the major pathophysiological factor underlying orthostatic hypotension after HDBR. It appears that the diminished sympathetic activity, in combination with other factors associated with HDBR (e.g., hypovolemia), may predispose some individuals to postural hypotension.     

The YUMIKO catheter: a useful tool for angiography of the right internal mammary artery via a right brachial approach

The YUMIKO catheter (Goodman, Nagoya, Japan) was recently developed for a left internal mammary artery (IMA) angiography with a right radial or brachial approach. The present authors experienced an interesting case where the YUMIKO catheter was useful for a right IMA angiography via a right brachial artery. A 53-year-old man with bilateral IMA grafts underwent follow-up coronary angiography via a right brachial artery. Native coronary artery and left IMA angiography were performed without difficulty using the Judkins Right and Left and YUMIKO catheters. Angiography of the right IMA was attempted with the Judkins Right catheter and IMA catheter, resulting in a nonselective angiogram with poor imaging. The YUMIKO catheter, however, enabled smooth cannulation to the right IMA and provided good images of the selective right IMA angiography.     

Molecular cloning and sequencing of the banded dogfish (Triakis scyllia) interleukin-8 cDNA

The dogfish (Triakis scyllia) interleukin-8 (IL-8) cDNA was isolated from mitogen-stimulated peripheral white blood cells (WBCs) utilising the polymerase chain reaction (PCR). The cDNA sequence showed that the dogfish IL-8 clones contained an open reading frame encoding 101 amino acids. A short 5' untranslated region (UTR) of 70 nucleotides and a long 3' UTR of 893 nucleotides were also present in this 1.2-kb cDNA. Furthermore, the 3' UTR of the mRNA contained the AUUUA sequence that has been implicated in shortening of the half-life of several cytokines and growth factors. The predicted IL-8 peptide had one potential N-linked glycosylation site (Asn-72-Thr-74) that is not conserved in other vertebrates. It also contained four cysteine residues (Cys-34, 36, 61 and 77), which are characteristic of CXC subfamily cytokines and found in all vertebrates, to date. The dogfish IL-8 lacked an ELR motif as found in the lamprey and trout. Comparison of the deduced amino acids showed that the dogfish IL-8 sequence shared 50.5, 41.2, 37.1 and 40.4-45.5% identity with the chicken, lamprey, trout and mammalian IL-8 sequences, respectively.     

Reduced Permeability to K+ and Na+ Ions of K+ Channels in the Plasma Membrane of Tobacco Cells in Suspension after Adaptation to 50 mM NaCl

The whole-cell patch-clamp technique was used to study and comparethe characteristics of K⁺-and Na⁺-transport processes acrossthe plasma membrane in two types of protoplast isolated fromNaCl-adapted and -unadapted cells of tobacco (Nicotiana tabacumL. cv. Bright Yellow-2) in suspension culture. In both typesof protoplast, with 100 mM KCl in the bathing solution and inthe pipette solution, depolarization of the plasma membranefrom the holding potential of 0 mV to a positive potential resultedin a relatively large outward current which increased with increasingpositive potential, whereas hyperpolarization to negative potentialsup to –100 mV resulted in only a small inward current.The outward current activated by depolarization was predominantlycarried by K⁺ ions through K⁺ channels. Na⁺ ions also had afinite ability to pass through these K⁺ channels. The outwardK⁺ and Na⁺ currents of the NaCl-adapted cells were considerablysmaller than those of the NaCl-unadapted cells. These resultssuggest that adaptation to salinity results in reduced permeabilityof the plasma membrane to both K⁺ and Na⁺ ions. ¹Present address: Research Laboratory of Applied Biochemistry,Tanabe Seiyaku Co., Ltd., 16-89, Kashima 3-chome, Yodogawa-ku,Osaka, 532 Japan