Determining divergence times of the major kingdoms of living organisms with a protein clock

Amino acid sequence data from 57 different enzymes were used to determine the divergence times of the major biological groupings. Deuterostomes and protostomes split about 670 million years ago and plants, animals, and fungi last shared a common ancestor about a billion years ago. With regard to these protein sequences, plants are slightly more similar to animals than are the fungi. In contrast, phylogenetic analysis of the same sequences indicates that fungi and animals shared a common ancestor more recently than either did with plants, the greater difference resulting from the fungal lineage changing faster than the animal and plant lines over the last 965 million years. The major protist lineages have been changing at a somewhat faster rate than other eukaryotes and split off about 1230 million years ago. If the rate of change has been approximately constant, then prokaryotes and eukaryotes last shared a common ancestor about 2 billion years ago, archaebacterial sequences being measurably more similar to eukaryotic ones than are eubacterial ones.

Determining divergence times with a protein clock: update and reevaluation

A recent study of the divergence times of the major groups of organisms as gauged by amino acid sequence comparison has been expanded and the data have been reanalyzed with a distance measure that corrects for both constraints on amino acid interchange and variation in substitution rate at different sites. Beyond that, the availability of complete genome sequences for several eubacteria and an archaebacterium has had a great impact on the interpretation of certain aspects of the data. Thus, the majority of the archaebacterial sequences are not consistent with currently accepted views of the Tree of Life which cluster the archaebacteria with eukaryotes. Instead, they are either outliers or mixed in with eubacterial orthologs. The simplest resolution of the problem is to postulate that many of these sequences were carried into eukaryotes by early eubacterial endosymbionts about 2 billion years ago, only very shortly after or even coincident with the divergence of eukaryotes and archaebacteria. The strong resemblances of these same enzymes among the major eubacterial groups suggest that the cyanobacteria and Gram-positive and Gram-negative eubacteria also diverged at about this same time, whereas the much greater differences between archaebacterial and eubacterial sequences indicate these two groups may have diverged between 3 and 4 billion years ago.

Collection and transfusion of blood and blood components in the United States, 1992

BACKGROUND

Studies were conducted to measure the state of the United States' national blood resource in 1992 and changes therein from 1989.

STUDY DESIGN AND METHODS

With data supplied by the American Red Cross and the American Association of Blood Banks, as well as data from a stratified random-sample survey of 3350 non-American Association of Blood Banks hospitals, statistical methods were applied to estimate national blood activities in 1992.

RESULTS

The total US blood supply in 1992 was 13,794,000 units, a decrease of 3.1 percent from 1989. Some 11,307,000 red cell units were transfused to 3,772,000 patients, an average of 3.0 units per transfused patient. Preoperative autologous blood deposits totaled 1,117,000 units, a 70-percent increase over 1989. Of this number, 566,000 units (50.7%) were transfused, 5,000 (4.4%) transferred to the allogeneic supply, and 546,000 (48.9%) discarded. Of 436,000 directed-donation units, 136,000 (31.2%) were transfused, 57,000 (13.1%) transferred to allogeneic supply, and 243,000 (55.7%) discarded. The total allogeneic blood supply, including imports, decreased by 7.4 percent from 1989, and allogeneic blood transfusions, including those to children, decreased by 8.6 percent. Over 8,300,000 platelet units were transfused; of these, some 3,600,000 were apheresis platelets. In addition, 2,255,000 units of plasma and 939,000 units of cryoprecipitate were transfused.

CONCLUSION

While the US blood supply was adequate for transfusion needs in 1992, blood collections and red cell transfusions had decreased substantially since 1989.

Constructing high complexity synthetic libraries of long ORFs using in vitro selection

We present a method that can significantly increase the complexity of protein libraries used for in vitro or in vivo protein selection experiments. Protein libraries are often encoded by chemically synthesized DNA, in which part of the open reading frame is randomized. There are, however, major obstacles associated with the chemical synthesis of long open reading frames, especially those containing random segments. Insertions and deletions that occur during chemical synthesis cause frameshifts, and stop codons in the random region will cause premature termination. These problems can together greatly reduce the number of full-length synthetic genes in the library. We describe a strategy in which smaller segments of the synthetic open reading frame are selected in vitro using mRNA display for the absence of frameshifts and stop codons. These smaller segments are then ligated together to form combinatorial libraries of long uninterrupted open reading frames. This process can increase the number of full-length open reading frames in libraries by up to two orders of magnitude, resulting in protein libraries with complexities of greater than 10(13). We have used this methodology to generate three types of displayed protein library: a completely random sequence library, a library of concatemerized oligopeptide cassettes with a propensity for forming amphipathic alpha-helical or beta-strand structures, and a library based on one of the most common enzymatic scaffolds, the alpha/beta (TIM) barrel.

Identification and cDNA cloning of a novel human mosaic protein, LGN, based on interaction with G alpha i2

We have used the yeast two-hybrid system to identify proteins that interact with the alpha-subunit of the heterotrimeric GTP-binding protein, Gi2. We screened a human B cell cDNA library with full-length G alpha i2 and isolated four positive colonies, one of which expressed the 44-kDa COOH terminus of a previously unrecognized 677-amino acid (aa) protein. A full-length clone was isolated from a HeLa cell cDNA library. The deduced protein contains 10 Leu-Gly-Asn repeats, and thus we named it LGN. Computer analysis indicates that LGN is a mosaic protein with seven repeated sequences of about 40 aa in length at its N-terminal end, and four repeated sequences of about 34 aa at its C-terminal end. Each of the two repeat regions shows substantial similarity to proteins found in other organisms. RT-PCR analysis of human tissues showed that the mRNA of LGN was ubiquitously expressed. The specificity of interaction between G alpha i2 and LGN was confirmed by an in vitro binding assay using recombinant proteins. These data indicate that the yeast two-hybrid system can identify novel proteins, such as LGN, that interact with G alpha proteins. As a mosaic protein, LGN shows similarity with portions of proteins from many species and thus may define a new protein family.

GW190521: A Binary Black Hole Merger with a Total Mass of 150 M_{⊙}

On May 21, 2019 at 03:02:29 UTC Advanced LIGO and Advanced Virgo observed a short duration gravitational-wave signal, GW190521, with a three-detector network signal-to-noise ratio of 14.7, and an estimated false-alarm rate of 1 in 4900 yr using a search sensitive to generic transients. If GW190521 is from a quasicircular binary inspiral, then the detected signal is consistent with the merger of two black holes with masses of 85_{-14}^{+21}  M_{⊙} and 66_{-18}^{+17}  M_{⊙} (90% credible intervals). We infer that the primary black hole mass lies within the gap produced by (pulsational) pair-instability supernova processes, with only a 0.32% probability of being below 65  M_{⊙}. We calculate the mass of the remnant to be 142_{-16}^{+28}  M_{⊙}, which can be considered an intermediate mass black hole (IMBH). The luminosity distance of the source is 5.3_{-2.6}^{+2.4}  Gpc, corresponding to a redshift of 0.82_{-0.34}^{+0.28}. The inferred rate of mergers similar to GW190521 is 0.13_{-0.11}^{+0.30}  Gpc^{-3} yr^{-1}.

Intron distribution in ancient paralogs supports random insertion and not random loss

The intron positions of ten different protein families were examined to determine (the statistical likelihood of) whether spliceosomal introns are the result of random insertion events into previously intronless genes, on the one hand, or the result of random loss from common ancestral introns, on the other. The number of expected matches for the alternative scenarios was calculated for a binomial distribution by considering currently observed introns relative to all possible locations for insertion or loss. Introns occurring at approximately the same location (hereafter called a "match") were tallied for each of the paired proteins. Matches were identified by their positions in the multiple alignment and were defined as any two introns occurring within a window of 11 possible nucleotide positions, thereby allowing for possible alignment errors and "intron sliding." Matches were tallied from the raw data and compared with the expected number of matches for the two different scenarios. The results suggest that the distribution of introns in genes encoding proteins is due to random insertion and not random loss.

High-affinity uptake of 67Cu into a veratridine-releasable pool in brain tissue

We have previously characterized two saturable, ligand-dependent processes for 67Cu uptake by hypothalamic slices: a high- and low-affinity process (22). In this study, we wished to ascertain if veratridine, a secretagogue that mimics a physiological release process, stimulates the release of newly taken up 67Cu and whether uptake of 67Cu into the releasable pool of copper is dependent on the process of 67Cu uptake. Hypothalamic or caudate slices from male rats were loaded for 30 min with 67Cu complexed to histidine (His) under conditions favoring high- or low-affinity uptake. First, we assessed the stability of the newly taken up 67Cu and found that, regardless of the mode of 67Cu entry into the tissue, greater than or equal to 85% of the 67Cu is retained in tissues incubated for 3 h in 67Cu-free buffer. Moreover, the 67Cu taken up by the high-affinity process was not displaced by 15-fold molar excess of nonradiolabeled Cu2+, histidine, albumin, or Zn2+, and only 20-30% of the 67Cu taken up by the low-affinity process was displaced by 10-fold excess Cu2+ or albumin. Next, we assessed veratridine stimulation of 67Cu release and found that 67Cu release occurred only from tissues loaded with the high- but not with the low-affinity process. This effect of veratridine was calcium dependent and was blocked by Tetrodotoxin, a specific blocker of the voltage-sensitive Na+ channel. In addition, we confirmed our earlier observation that a depolarizing concentration of K+ stimulates 67Cu release.(ABSTRACT TRUNCATED AT 250 WORDS)

Semirigid ureteroscopy: a new genre

The semirigid ureteroscope has a diameter of 7.2F for the distal 11 cm. and gradually enlarges to 11.9F at the proximal portion. We inserted the device in the ureter of 50 consecutive patients without the need for ureteral dilation. The instrument has 2, 0.025-inch channels (2.1F) for wires (0.025), irrigation or 250 mu. laser fibers. Flexible optical fibers and a metal sheath allow for handling as with a rigid instrument, with 2 inches of flexure at the tip without loss of vision. The instrument was inserted successfully in 26 of 27 female patients (lower ureter in 13 of 13, mid ureter in 4 of 4 and upper ureter in 9 of 10), and 14 of 23 male patients (lower ureter in 8 of 10, mid ureter in 4 of 8 and upper ureter in 2 of 5). The semirigid ureteroscope may be used for laser fragmentation of ureteral calculi in almost all female patients and in some male patients. It may be used in strictured and otherwise impassable ureters, for placement of guide wires in the intramural tunnel and to examine the entire ureter atraumatically in most female and some male patients. The device has been designed specifically for laser lithotripsy, and its development expands the indications and facility with which this technology may be used.

Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA

We present our current best estimate of the plausible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next several years, with the intention of providing information to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals for the third (O3), fourth (O4) and fifth observing (O5) runs, including the planned upgrades of the Advanced LIGO and Advanced Virgo detectors. We study the capability of the network to determine the sky location of the source for gravitational-wave signals from the inspiral of binary systems of compact objects, that is binary neutron star, neutron star-black hole, and binary black hole systems. The ability to localize the sources is given as a sky-area probability, luminosity distance, and comoving volume. The median sky localization area (90% credible region) is expected to be a few hundreds of square degrees for all types of binary systems during O3 with the Advanced LIGO and Virgo (HLV) network. The median sky localization area will improve to a few tens of square degrees during O4 with the Advanced LIGO, Virgo, and KAGRA (HLVK) network. During O3, the median localization volume (90% credible region) is expected to be on the order of 10 5 , 10 6 , 10 7 Mpc 3 for binary neutron star, neutron star-black hole, and binary black hole systems, respectively. The localization volume in O4 is expected to be about a factor two smaller than in O3. We predict a detection count of 1 - 1 + 12 ( 10 - 10 + 52 ) for binary neutron star mergers, of 0 - 0 + 19 ( 1 - 1 + 91 ) for neutron star-black hole mergers, and 17 - 11 + 22 ( 79 - 44 + 89 ) for binary black hole mergers in a one-calendar-year observing run of the HLV network during O3 (HLVK network during O4). We evaluate sensitivity and localization expectations for unmodeled signal searches, including the search for intermediate mass black hole binary mergers.

Sp1 and C/EBP-related factor regulate the transcription of human Cu/Zn SOD gene

The Cu/Zn superoxide dismutase (SOD1) is one of the key enzymes that protect cells against oxidative stress. It catalyzes the dismutation of superoxide radicals (O2-) to oxygen and hydrogen peroxide. To study the transcriptional regulation of the human Cu/Zn SOD gene, we began by analyzing the 1.5-kb upstream region of the gene (see Kim et al., 1994). The element from nucleotides (nt) -116 to -45 increased the transcriptional activity of Cu/Zn SOD. Analyses by DNase I footprinting and electrophoretic mobility shift assay (EMSA) showed that Sp1 binds to the region from nt -104 to -89 and C/EBP-related factors to the region from nt -64 to -55. Studies using two mutant versions of this promoter, in which the Sp1 and C/EBP-related factor binding sites were deleted, respectively, revealed that Sp1 and C/EBP-related factors activate the transcription of SOD1 gene. An Sp1 expression plasmid, pPacSp1, stimulated the SOD1-linked CAT expression. Cotransfection of the element from nt -116 to -45 with the C/EBP alpha expression vector, pMSV-C/EBP, increased the transcriptional activity of the Cu/Zn SOD in HepG2 cells, but barely in HeLa cells. Because Sp1 is a ubiquitously expressed transcriptional factor, the binding of Sp1 to the proximal upstream region of the Cu/Zn SOD might explain the expression of Cu/Zn SOD in a wide variety of cells.

Brain-derived neurotrophic factor induces functional expression and phenotypic differentiation of cultured fetal neuropeptide Y-producing neurons

A series of studies from our laboratory has established an aggregate culture system of fetal rat brain cells that can serve as a model for studying regulatory processes of the developing neuropeptide Y (NPY)-producing neurons. Using aggregate cultures derived from 17-day-old fetal rat cortex, we addressed these questions: 1) Does brain-derived neurotrophic factor (BDNF) stimulate NPY production, and if so, is stimulation a function of the developmental state of the cultured NPY neuron? 2) Does BDNF induce phenotypic differentiation of NPY neurons? BDNF led to an increase in NPY production and the accumulation of NPY-mRNA in a dose dependent manner. BDNF did not alter the stability of NPY-mRNA, judged by the disappearance rate of NPY-mRNA after blockade of RNA synthesis (estimated t1/2 was 6-8 hr). BDNF stimulation of NPY production was dependent on length of exposure to BDNF and on culture-age. A continuous 8-day exposure to BDNF resulted in a significantly higher level of NPY production than a pulse of 2 days (comparing BDNF exposure on days 0-8 vs. 6-8, or days 8-17 vs. 15-17). Moreover, older neurons (age 17 days) produced twice as much NPY as younger (age 8 days) neurons in response to a 2-day pulse of BDNF (50 ng/ml). BDNF was significantly more effective than NT-3 in inducing NPY production, and NGF was ineffective. Immunocytochemical analysis of 8-day NPY neurons revealed that a 2-day pulse of BDNF induced the appearance of an abundance of morphologically well-defined neurons bearing an elaborate network of neurites. This was in contrast to the control-treated NPY neurons, which were morphologically undefined. In summary, the age-dependent effect of BDNF on NPY production is consistent with induction of functional expression, rather than promotion of survival, of cultured NPY neurons. The neurotrophin specificity for stimulation of NPY production, and the lack of effect of BDNF on the stability of NPY-mRNA, implicate the TrkB receptor in mediating transcriptional activation of the NPY gene. Thus, BDNF exerts a dual effect on developing cultured NPY neurons: induction of functional expression, and phenotypic differentiation of immature neurons into mature neurite-bearing neurons.

A reduction in the concentration of immunoreactive corticotropin, melanotropin and lipotropin in the brain of the aging rat

We have previously shown that the hypothalamic concentration of immunoreactive alpha-melanotropin (alpha-MSHi) is markedly lower in the aging female rat than in the young rat. The current view is that alpha-MSH is derived from corticotropin (ACTH), and ACTH, in turn, is derived from a large molecular-weight precursor (pro-opiocortin); pro-opiocortin also serves as the precursor to beta- and gamma-lipotropin (LPH). To ascertain if the age-related reduction in the concentration of alpha-MSHi may be a result of a decline in the production of pro-opiocortin, we determined the content of immunoreactive ACTH (ACTHi), alpha-MSH (alpha-MSHi), gamma-LPH (gamma-LPHi), and protein, in 3 regions of the brain of young (4 months) and old (26-28 months) female rats: the medial basal hypothalamus (MBH, the region containing the perikarya of the ACTH/MSH/LPH neurons), the preoptic anterior hypothalamus (POA), and the thalamus (regions containing axons of these neurons). The concentration of ACTHi, alpha-MSHi (mol/mg protein), or gamma-LPHi (U/mg protein) in the MBH of old rats was 30-50% of that in the MBH of young rats. Moreover, the concentration of ACTHi, alpha-MSHi or gamma-LPHi in the POA and thalamus of old rats was also lower than that in the POA and thalamus of young rats. Based on these findings, we propose that aging causes a reduction in the production of pro-opiocortin in the brain of the female rat and that such a change may be related to the altered function of the brain of the aged.

Localization of HSP90 binding sites in the human hepatitis B virus polymerase

The fact that HSP90 proteins and their chaperonin partners play an important role in epsilon RNA binding of duck HBV Pol protein during duck HBV replication has been reported. To elucidate the molecular basis of HBV Pol/HSP90 interaction, we have characterized the HSP90 interaction to HBV Pol. We found that human HBV Pol protein upon synthesis in rabbit reticulocyte lysate formed a complex with HSP90 in vitro as duck HBV Pol did. In addition, HSP90 protein was copurified with MBP/POL protein expressed in HepG2 cells, suggesting that human HBV Pol protein is associated with HSP90 in vivo. To localize the HSP90 interaction site region, several deletion mutants of HBV Pol translated in vitro were immunoprecipitated with anti-HSP90 antibody. The result indicates that C-terminal regions of the TP and RT domains interact with HSP90 independently.

Dexamethasone-induced accumulation of neuropeptide-Y by aggregating fetal brain cells in culture: a process dependent on the developmental age of the aggregates

Neuropeptide-Y (NPY) and glucocorticoid receptors are coexpressed in many neurons in the brain. We addressed the question: Do glucocorticoids regulate the accumulation and/or secretion of immunoreactive (IR) NPY by fetal rat brain cells in culture, and if so, is the effect developmental stage dependent? Aggregates, formed from dissociated cells obtained from the hypothalamus-olfactory tubercle of 17-day-old fetuses, were cultured in serum-free medium for 23 days. On day 23, the aggregate NPY content was 6 ng/flask, and secretion (last 2 days) was approximately 12 ng/24 h. Exposure to dexamethasone (Dex; 20 nM) between days 0-23 led to a 1.9-fold increase in the aggregate content of NPY, whereas NPY secretion was not altered. When Dex exposure was limited to days 12-23, 16-23, 19-23, or 21-23, only a 12- to 23-day exposure induced NPY accumulation, and it was as effective as a 0- to 23-day exposure. The Dex-induced increase in NPY content was evident after a lag period of 4 days or more. When Dex exposure occurred on days 0-12, the aggregate NPY content on day 12 or 23 was not altered. None of these treatments altered the aggregate/medium content of immunoreactive somatostatin (SRIF) or the response to a 48-h exposure to forskolin (10 microM). Dex induction of NPY accumulation was a saturable function of the Dex concentration (maximal at 20 nM), and it was completely inhibited by RU486, a glucocorticoid/progesterone receptor antagonist; neither progesterone, 17 beta-estradiol, nor testosterone altered aggregate/medium NPY contents. Protein/DNA contents of the aggregates were either unaffected or slightly reduced by Dex. Thus, 1) Dex stimulates the accumulation of immunoreactive NPY, but not SRIF, by cultured fetal brain cells; 2) this effect requires a continuous 8-12 days of exposure to Dex during a late developmental stage in culture; 3) Dex does not potentiate or attenuate forskolin action on the NPY neuron; and 4) Dex action appears to be mediated by the glucocorticoid receptor. These results are consistent with glucocorticoid induction of production and/or decreased intracellular degradation of NPY, and with glucocorticoids regulating the NPY neuron in the perinatal brain in a developmental age-dependent manner.

Structure-function analysis of the DNA binding domain of Saccharomyces cerevisiae ABF1

To localize the DNA binding domain of the Saccharomyces cerevisiae Ars binding factor 1 (ABF1), a multifunctional DNA binding protein, plasmid constructs carrying point mutations and internal deletions in the ABF1 gene were generated and expressed in Escherichia coli. Normal and mutant ABF1 proteins were purified by affinity chromatography and their DNA binding activities were analyzed. The substitution of His61, Cys66 and His67 respectively, located in the zinc finger motif in the N-terminal region (amino acids 40-91), eliminated the DNA binding activity of ABF1 protein. Point mutations in the middle region of ABF1, specifically at Leu353, Leu399, Tyr403, Gly404, Phe410 and Lys434, also eliminated or reduced DNA binding activity. However, the DNA binding activity of point mutants of Ser307, Ser496 and Glu649 was the same as that of wild-type ABF1 protein and deletion mutants of amino acids 200-265, between the zinc finger region and the middle region (residues 323-496) retained DNA binding activity. As a result, we confirmed that the DNA binding domain of ABF1 appears to be bipartite and another DNA binding motif, other than the zinc finger motif, is situated between amino acid residues 323 and 496.

A putative role for extracellular ATP: facilitation of 67copper uptake and of copper stimulation of the release of luteinizing hormone-releasing hormone from median eminence explants

We have previously shown that extracellular copper stimulates the release of the luteinizing hormone-releasing hormone (LH-RH) from explants of the median eminence area (MEA), that chelated copper (Cu) but not ionic Cu is the active form of the metal, and that there is a direct correlation between the ligand specificity for 67Cu uptake and Cu action. In this study, we examined the possibility that extracellular ATP can serve as a ligand facilitating Cu action on the LH-RH neuron. Hypothalamic slices or MEA explants of adult male rats were used. It was found that ATP facilitates 67Cu uptake by hypothalamic slices when Cu:ATP molar ratio was 1:2000 but not 1:2. Keeping the [Cu] constant (150 microM) and varying [ATP], ATP facilitation of Cu stimulation of LH-RH release from MEA explants was found to be a saturable function of [ATP]; maximal facilitation occurred with 2.5 mM ATP. When the nucleotide phosphate specificity for facilitation of Cu action was assessed, ADP, ATP, alpha, beta-methylene-ATP (the non-hydrolyzable analogue of ATP) and GTP were equally effective, whereas AMP and adenosine were ineffective. These results indicate that extracellular ATP can facilitate Cu action on the LH-RH neuron and they are consistent with two mechanisms: (1) ATP facilitating Cu uptake and hence, Cu action and (2) ATP facilitating Cu action via an interaction with a purinergic receptor.

Electrical and Electrochemical Sensors Based on Carbon Nanotubes for the Monitoring of Chemicals in Water-A Review

Carbon nanotubes (CNTs) combine high electrical conductivity with high surface area and chemical stability, which makes them very promising for chemical sensing. While water quality monitoring has particularly strong societal and environmental impacts, a lot of critical sensing needs remain unmet by commercial technologies. In the present review, we show across 20 water monitoring analytes and 90 references that carbon nanotube-based electrochemical sensors, chemistors and field-effect transistors (chemFET) can meet these needs. A set of 126 additional references provide context and supporting information. After introducing water quality monitoring challenges, the general operation and fabrication principles of CNT water quality sensors are summarized. They are sorted by target analytes (pH, micronutrients and metal ions, nitrogen, hardness, dissolved oxygen, disinfectants, sulfur and miscellaneous) and compared in terms of performances (limit of detection, sensitivity and detection range) and functionalization strategies. For each analyte, the references with best performances are discussed. Overall, the most frequently investigated analytes are H+ (pH) and lead (with 18% of references each), then cadmium (14%) and nitrite (11%). Micronutrients and toxic metals cover 40% of all references. Electrochemical sensors (73%) have been more investigated than chemistors (14%) or FETs (12%). Limits of detection in the ppt range have been reached, for instance Cu(II) detection with a liquid-gated chemFET using SWCNT functionalized with peptide-enhanced polyaniline or Pb(II) detection with stripping voltammetry using MWCNT functionalized with ionic liquid-dithizone based bucky-gel. The large majority of reports address functionalized CNTs (82%) instead of pristine or carboxyl-functionalized CNTs. For analytes where comparison is possible, FET-based and electrochemical transduction yield better performances than chemistors (Cu(II), Hg(II), Ca(II), H2O2); non-functionalized CNTs may yield better performances than functionalized ones (Zn(II), pH and chlorine).

The Application of Thick Hydrogenated Amorphous Silicon Layers to Charged Particle and X-Ray Detection

We outline the characteristics of thick hydrogdenated amorphous silicon layers which are optimized for the detection of charged particles, x-rays and γ-rays. Signal amplitude as a function of the linear energy transfer of various particles are given. Noise sources generated by the detector material and by the thin film electronics - a-Si:H or polysilicon proposed for pixel position sensitive detectors readout are described, and their relative amplitudes are calculated. Temperature and neutron radiation effects on leakage currents and the corresponding noise changes are presented.

C/EBP alpha and C/EBPbeta play similar roles in the transcription of the human Cu/Zn SOD gene

Copper/zinc-containing superoxide dismutase (Cu/Zn SOD) is one of the essential enzymes that protects cells in aerobic conditions. To understand the mechanism of transcriptional regulation of the human Cu/Zn SOD gene, the proximal promoter region of Cu/Zn SOD has been investigated. In a previous study, it was found that transcription factors of the Sp1 and C/EBP family are associated with the expression of human Cu/Zn SOD [Seo et al. (1996). Gene, 178, 177-180]. Of the four known C/EBP activators, the effects of C/EBP alpha and C/EBPbeta on the transcription of Cu/Zn SOD were examined. Usually, one of the two C/EBP factors, C/EBP alpha or C/EBPbeta, exclusively stimulates the target gene, but, unexpectedly, C/EBP alpha and C/EBPbeta stimulated the expression of Cu/Zn SOD to a similar extent in our experiments. LIP, a dominant negative regulator of the C/EBP family, inhibited the transcriptional activation of Cu/Zn SOD stimulated by C/EBP alpha and C/EBPbeta. These results suggest that C/EBP alpha and C/EBPbeta can substitute each other and play similar roles on the transcription of Cu/Zn SOD.