Development of advanced photon calibrator for Kamioka gravitational wave detector (KAGRA)

The Kamioka Gravitational wave detector (KAGRA) cryogenic gravitational-wave observatory has commenced joint observations with the worldwide gravitational wave detector network. Precise calibration of the detector response is essential for accurately estimating parameters of gravitational wave sources. A photon calibrator is a crucial calibration tool used in laser interferometer gravitational-wave observatory, Virgo, and KAGRA, and it was utilized in joint observation 3 with GEO600 in Germany in April 2020. In this paper, KAGRA implemented three key enhancements: a high-power laser, a power stabilization system, and remote beam position control. KAGRA employs a 20 W laser divided into two beams that are injected onto the mirror surface. By utilizing a high-power laser, the response of the detector at kHz frequencies can be calibrated. To independently control the power of each laser beam, an optical follower servo was installed for power stabilization. The optical path of the photon calibrator's beam positions was controlled using pico-motors, allowing for the characterization of the detector's rotation response. Additionally, a telephoto camera and quadrant photodetectors were installed to monitor beam positions, and beam position control was implemented to optimize the mirror response. In this paper, we discuss the statistical errors associated with the measurement of relative power noise. We also address systematic errors related to the power calibration model of the photon calibrator and the simulation of elastic deformation effects using finite element analysis. Ultimately, we have successfully reduced the total systematic error from the photon calibrator to 2.0%.

Constraints on Sub-GeV Dark Matter-Electron Scattering from the CDEX-10 Experiment

We present improved germanium-based constraints on sub-GeV dark matter via dark matter-electron (χ-e) scattering using the 205.4  kg·day dataset from the CDEX-10 experiment. Using a novel calculation technique, we attain predicted χ-e scattering spectra observable in high-purity germanium detectors. In the heavy mediator scenario, our results achieve 3 orders of magnitude of improvement for m_{χ} larger than 80  MeV/c^{2} compared to previous germanium-based χ-e results. We also present the most stringent χ-e cross-section limit to date among experiments using solid-state detectors for m_{χ} larger than 90  MeV/c^{2} with heavy mediators and m_{χ} larger than 100  MeV/c^{2} with electric dipole coupling. The result proves the feasibility and demonstrates the vast potential of a new χ-e detection method with high-purity germanium detectors in ultralow radioactive background.

Exotic Dark Matter Search with the CDEX-10 Experiment at China's Jinping Underground Laboratory

A search for exotic dark matter (DM) in the sub-GeV mass range has been conducted using 205 kg day data taken from a p-type point contact germanium detector of the CDEX-10 experiment at China's Jinping underground laboratory. New low-mass dark matter searching channels, neutral current fermionic DM absorption (χ+A→ν+A) and DM-nucleus 3→2 scattering (χ+χ+A→ϕ+A), have been analyzed with an energy threshold of 160 eVee. No significant signal was found; thus new limits on the DM-nucleon interaction cross section are set for both models at the sub-GeV DM mass region. A cross section limit for the fermionic DM absorption is set to be 2.5×10^{-46}  cm^{2} (90% C.L.) at DM mass of 10  MeV/c^{2}. For the DM-nucleus 3→2 scattering scenario, limits are extended to DM mass of 5 and 14  MeV/c^{2} for the massless dark photon and bound DM final state, respectively.

Constraints on Cosmic Strings Using Data from the Third Advanced LIGO-Virgo Observing Run

We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset. Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions. A template-based search for short-duration transient signals does not yield a detection. We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models. Additionally, we develop and test a third model that interpolates between these two models. Our results improve upon the previous LIGO-Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested. In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ≲4×10^{-15}. In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models.

Constraints on Cosmic Strings Using Data from the Third Advanced LIGO-Virgo Observing Run

We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset. Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions. A template-based search for short-duration transient signals does not yield a detection. We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models. Additionally, we develop and test a third model that interpolates between these two models. Our results improve upon the previous LIGO-Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested. In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ≲4×10^{-15}. In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models.

Direct Detection Constraints on Dark Photons with the CDEX-10 Experiment at the China Jinping Underground Laboratory

We report constraints on the dark photon effective kinetic mixing parameter (κ) with data taken from two p-type point-contact germanium detectors of the CDEX-10 experiment at the China Jinping Underground Laboratory. The 90% confidence level upper limits on κ of solar dark photon from 205.4 kg-day exposure are derived, probing new parameter space with masses (m_{V}) from 10 to 300  eV/c^{2} in direct detection experiments. Considering dark photon as the cosmological dark matter, limits at 90% confidence level with m_{V} from 0.1 to 4.0  keV/c^{2} are set from 449.6 kg-day data, with a minimum of κ=1.3×10^{-15} at m_{V}=200  eV/c^{2}.

Search for Light Weakly-Interacting-Massive-Particle Dark Matter by Annual Modulation Analysis with a Point-Contact Germanium Detector at the China Jinping Underground Laboratory

We present results on light weakly interacting massive particle (WIMP) searches with annual modulation (AM) analysis on data from a 1-kg mass p-type point-contact germanium detector of the CDEX-1B experiment at the China Jinping Underground Laboratory. Datasets with a total live time of 3.2 yr within a 4.2-yr span are analyzed with analysis threshold of 250 eVee. Limits on WIMP-nucleus (χ-N) spin-independent cross sections as function of WIMP mass (m_{χ}) at 90% confidence level (C.L.) are derived using the dark matter halo model. Within the context of the standard halo model, the 90% C.L. allowed regions implied by the DAMA/LIBRA and CoGeNT AM-based analysis are excluded at >99.99% and 98% C.L., respectively. These results correspond to the best sensitivity at m_{χ}<6  GeV/c^{2} among WIMP AM measurements to date.

Constraints on Spin-Independent Nucleus Scattering with sub-GeV Weakly Interacting Massive Particle Dark Matter from the CDEX-1B Experiment at the China Jinping Underground Laboratory

We report results on the searches of weakly interacting massive particles (WIMPs) with sub-GeV masses (m_{χ}) via WIMP-nucleus spin-independent scattering with Migdal effect incorporated. Analysis on time-integrated (TI) and annual modulation (AM) effects on CDEX-1B data are performed, with 737.1 kg day exposure and 160 eVee threshold for TI analysis, and 1107.5 kg day exposure and 250 eVee threshold for AM analysis. The sensitive windows in m_{χ} are expanded by an order of magnitude to lower DM masses with Migdal effect incorporated. New limits on σ_{χN}^{SI} at 90% confidence level are derived as 2×10^{-32}∼7×10^{-35}  cm^{2} for TI analysis at m_{χ}∼50-180  MeV/c^{2}, and 3×10^{-32}∼9×10^{-38}  cm^{2} for AM analysis at m_{χ}∼75  MeV/c^{2}-3.0  GeV/c^{2}.

Limits on Light Weakly Interacting Massive Particles from the First 102.8 kg×day Data of the CDEX-10 Experiment

We report the first results of a light weakly interacting massive particles (WIMPs) search from the CDEX-10 experiment with a 10 kg germanium detector array immersed in liquid nitrogen at the China Jinping Underground Laboratory with a physics data size of 102.8 kg day. At an analysis threshold of 160 eVee, improved limits of 8×10^{-42} and 3×10^{-36}  cm^{2} at a 90% confidence level on spin-independent and spin-dependent WIMP-nucleon cross sections, respectively, at a WIMP mass (m_{χ}) of 5  GeV/c^{2} are achieved. The lower reach of m_{χ} is extended to 2  GeV/c^{2}.

Orbital-dependent charge dynamics in MnP revealed by optical study

Unconventional superconductivity often emerges at the border of long-range magnetic orders. Understanding the low-energy charge dynamics may provide crucial information on the formation of superconductivity. Here we report the unpolarized/polarized optical conductivity study of high quality MnP single crystals at ambient pressure. Our data reveal two types of charge carriers with very different lifetimes. In combination with the first-principles calculations, we show that the short-lifetime carriers have flat Fermi sheets which become gapped in the helimagnetic phase, causing a dramatic change in the low-frequency optical spectra, while the long-lifetime carriers are anisotropic three-dimensional like which are little affected by the magnetic transitions and provide major contributions to the transport properties. This orbital-dependent charge dynamics originates from the special crystal structure of MnP and may have an influence on the unconventional superconductivity and its interplay with helimagnetism at high pressures.

Pressure induced superconductivity on the border of magnetic order in MnP

We report the discovery of superconductivity on the border of long-range magnetic order in the itinerant-electron helimagnet MnP via the application of high pressure. Superconductivity with T(sc)≈1  K emerges and exists merely near the critical pressure P(c)≈8  GPa, where the long-range magnetic order just vanishes. The present finding makes MnP the first Mn-based superconductor. The close proximity of superconductivity to a magnetic instability suggests an unconventional pairing mechanism. Moreover, the detailed analysis of the normal-state transport properties evidenced non-Fermi-liquid behavior and the dramatic enhancement of the quasiparticle effective mass near P(c) associated with the magnetic quantum fluctuations.

Limits on spin-independent couplings of WIMP dark matter with a p-type point-contact germanium detector

We report new limits on a spin-independent weakly interacting massive particle (WIMP)-nucleon interaction cross section using 39.5 kg days of data taken with a p-type point-contact germanium detector of 840 g fiducial mass at the Kuo-Sheng Reactor Neutrino Laboratory. Crucial to this study is the understanding of the selection procedures and, in particular, the bulk-surface events differentiation at the sub-keV range. The signal-retaining and background-rejecting efficiencies were measured with calibration gamma sources and a novel n-type point-contact germanium detector. Part of the parameter space in the cross section versus WIMP-mass implied by various experiments is probed and excluded.

Observation of fluorescence emissions from single-bubble sonoluminescence in water doped with quinine

Sonoluminescence is a phenomenon involving the transduction of sound into light. The detailed mechanism as well as the energy-focusing potentials are not yet fully explored and understood. So far only optical photons are observed, while emissions in the ultra-violet range are only inferred. By doping the fluorescent dye quinine into water with dilute sulphuric acid, the high energy photons can be converted into the optical photons with slower decay constants. These sonoluminescence and fluorescent emissions were observed in coincidence, and the emitted signals of the two modes can be differentiated by their respective timing profiles. Plans for using this technique as a diagnostic tool to quantitatively study ultra-violet and other high energy emissions in sonoluminescence are discussed.

Isolation and characterization of human tissue kallikrein produced in Escherichia coli: biochemical comparison to the enzymatically inactive prokallikrein and methionyl kallikrein

This report describes bacterial expression, isolation, and characterization of human tissue kallikrein recombinantly produced in Escherichia coli. Successful production of enzymatically active recombinant human kallikrein requires the following processes: expression, solubilization and refolding of prokallikrein, thermolysin activation, and chromatographic separation. All experimental data confirmed that bacterially derived human kallikrein is properly folded and exhibits expected biochemical functions. As confirmed by SDS-PAGE and reverse-phase HPLC, recombinant kallikrein is apparently pure and is devoid of reduced or other partially folded kallikrein forms. Recombinant kallikrein behaves as a monomeric molecule in solution and exhibits full enzymatic activity in hydrolyzing peptide substrates. The molecule can bind to aprotinin to form kallikrein-inhibitor complex at a 1:1 molar ratio. Peptide mapping analysis derived from pepsin digestion of recombinant kallikrein assigned five disulfide bonds which match those of porcine kallikrein predicted from X-ray structure. Peptides containing unpaired cysteines or mispaired disulfide bonds were not detected. Both properly folded prokallikrein and methionyl kallikrein, containing a propeptide and an initiator methionine at their N-termini, respectively, were also produced and isolated. These two molecules are structurally similar to recombinant kallikrein, but are not enzymatically active.

Purification and characterization of human tissue prokallikrein and kallikrein isoforms expressed in Chinese hamster ovary cells

We report here the expression of recombinant human prokallikrein and kallikrein in engineered Chinese hamster ovary cells transfected with a human genomic gene encoding preprokallikrein. At high expression levels, recombinant prokallikrein, an inactive proenzyme form, is predominantly secreted into the culture medium. Upon chromatographic separations, the inactive prokallikrein as well as the mature kallikrein after thermolysin activation of the proenzyme can be prepared to apparent purity. Both prokallikrein and kallikrein can be further separated into two distinct high- and low-molecular-weight isoforms. Kallikrein preparations are fully active in standard kallikrein activity assays such as esterase activity and kinin release from kininogen. Both kallikrein and prokallikrein display multiple molecular forms with differences in both molecular sizes and charges. The structural differences in high- and low-molecular-weight kallikreins or prokallikreins were found to be due to glycosylation, with the high-molecular-weight species glycosylated at three Asn-linked sites and the low-molecular-weight species at two of the three Asn-linked sites. The multiply charged kallikrein isoforms are derived from different numbers of sialic acids attached at the detected Asn-linked carbohydrates. In comparison with kallikrein, prokallikrein appears to show a significant decrease in the magnitude of near uv-circular dichroism bands, suggesting a change in local conformation. This conformational change correlates with the loss of activity in proenzyme due to the presence of propeptide.

Brachial plexus neuropathy secondary to septic arthritis and osteomyelitis: report of two cases

Two infants, delivered uneventfully, later developed right brachial plexus palsy secondary to pyogenic osteomyelitis and arthritis of the right shoulder joint. Weakness of right arms occurred at the sixth and tenth days of age respectively. Both had right arm tenderness on palpation and passive movement. Roentgenograms of their right shoulder joints showed irregular radiolucency of the proximal margin of right humerus head. In both cases, electromyography revealed various degrees of significant denervation pattern for the C5-C7 innervated muscles. Pus culture from right shoulder joints grew Streptococcus viridans and Staphylococcus aureus, respectively. After antibiotic therapy and arthrotomy with drainage, weakness improved gradually following continuous rehabilitation. Follow-up at six months of age showed almost complete recovery of right upper extremity function in one patient, but mild residual weakness in the other. Follow-up electromyography studies showed continued improvement. The possible mechanism of this rare occurrence is discussed.

Comparison of N-linked oligosaccharides of recombinant human tissue kallikrein produced by Chinese hamster ovary cells on microcarrier beads and in serum-free suspension culture

Glycosylation heterogeneity in recombinant human tissue kallikrein (r-HuTK) produced by Chinese hamster ovary (CHO) cells from microcarrier culture and from a serum-free suspension cell recycle process has been compared. Significant differences in the degree of sialylation were observed in glycoform distribution and oligosaccharide heterogeneity. High-performance liquid chromatography with a pellicular anion-exchange column under low pH eluant conditions was used to characterize the number and types of N-linked complex type oligosaccharides present. The oligosaccharides were released by N-glycanase and, after reduction, were resolved into a number of peaks containing one, two, three, and four sialic acids with an additional subfractionation based on the nature of the antennary structure. The microcarrier process resulted in a reduced amount of sialylated oligosaccharide species as compared to the suspension cell process. Removal of sialic acid followed by chromatography of the asialooligosaccharides under high pH anion-exchange conditions indicated that the same antennary structures were present but in slightly different relative amounts. The oligosaccharide profiles are indicative of a highly complex array of microheterogeneity present, encompassing mono-, di-, tri-, and tetrasialylated complex type oligosaccharides.

Molecular cloning and sequence analysis of the monkey and human tissue kallikrein genes

Cynomolgus monkey renal kallikrein cDNA and genomic human tissue kallikrein gene were cloned. The monkey gene encodes a 257 amino acid (aa) preprokallikrein and exhibits 95% and 92% homology to the human at nucleotide (nt) and aa level, respectively. The monkey gene encodes a 233-aa mature kallikrein versus a 238-aa in human. The human kallikrein gene and urinary kallikrein both contain a Lys-162 instead of the reported Glu-162. Human, monkey and rat renal/pancreatic kallikrein genes evolve with a N-glycosylation containing domain (aa 81-87) which is absent in porcine and is non-glycosylable in mice. Only human kallikrein evolves with an additional Thr-108 and with a N-glycosylation site at aa-141.

High-performance anion-exchange chromatography of asparagine-linked oligosaccharides

Oligosaccharides released enzymatically by N-glycanase from fetuin, alpha-acid glycoprotein, human chorionic gonadotropin, platelet-derived growth factor, and kallikrein were chromatographed on a polymeric pellicular anion-exchange column at pH values of 5 and 13. Separations occurred into groups of peaks containing the same number of sialic acids with an additional separation dependent upon the nature of the antennary structure present. High pH conditions were required for the optimum separation of fetuin oligosaccharides, while low pH conditions significantly improved resolution of oligosaccharides obtained from the other glycoproteins. The analytical separation of oligosaccharides under conditions of low pH has important implications in the development of chromatographic mapping and identification techniques for N-linked oligosaccharides present on recombinant proteins.

The N-terminal sequence of the major erythropoietic factor of an anephric patient is identical to insulin-like growth factor I

The erythropoietic factors present in an anephric patient with nearly normal hematocrit were isolated from plasma by reversed-phase and gel permeation HPLC. The most active fraction was purified and the analysis of its N-terminal sequence was identical to the published sequence of the human insulin-like growth factor I (IGF I). Recombinant human IGF I had identical elution positions as the isolated erythropoietic factor on reversed-phase HPLC and the same molecular weight on gel permeation HPLC. Furthermore, hrIGF I stimulated erythroid colony formation in human bone marrow cultures as was previously shown for the isolated human erythropoietic factor. These results suggest that IGF I may replace erythropoietin as a stimulator of erythropoiesis in some patients with anemia and renal failure.

The evaluation of cerebral blood flow velocities in normal newborns and infants

The cerebral blood flow velocities of 80 normal newborn babies and 117 normal infants were evaluated by pulsed-Doppler investigation of anterior cerebral arteries through the open anterior fontanel. Peak systolic blood flow velocity (PSFV), end-diastolic blood flow velocity (EDFV), mean blood flow velocity (MFV), and the pulsatility index (PI) values were measured for all subjects. In the neonate group, all flow velocities increased in the first 20 days after birth, with rapid increase from one to two months of age. After that, velocities increased steadily within the first year of age. The increasing flow velocities probably reflect the changes in cerebral blood flow and arterial blood pressure during the first year of life. On the contrary, the pulsatility indices (PI) slightly decreased during this first year. The result supports the hypothesis of a decrease in cerebrovascular resistance during infancy. This study may have value as reference for normal cerebral blood flow velocities and pulsatility indices as determined during infancy for different age groups.

Cerebral blood flow velocity in newborn infants with asphyxia

A pulsed-Doppler real-time technique was used to assess the anterior cerebral artery (ACA) flow velocity in 30 asphyxiated infants during the first 5 days after birth. Thirty healthy term infants were also studied as controls. Peak systolic flow velocity (PSFV), end diastolic flow velocity (EDFV), mean flow velocity (MFV), and pulsatility index (PI) were measured. Mean PI values of the ACA of the asphyxiated and control groups were 0.63 +/- 0.05 vs 0.71 +/- 0.04 (p less than 0.001) on the first day; 0.64 +/- 0.03 vs 0.70 +/- 0.05 (p less than 0.001) on the third day and 0.69 +/- 0.04 vs 0.70 +/- 0.04 (p greater than 0.05) on the fifth day of life. The asphyxiated group also had significantly higher EDFV and MFV than those of control group until the 5th day of life. The low PI values of asphyxiated infants were mainly due to an increase in EDFV. These results suggest that the cerebrovascular resistance of asphyxiated infants, as reflected by the PI, is low during the first 3 days of life, indicating an increase in cerebral blood flow. With this technique, we can repeatedly and safely evaluate the cerebral hemodynamic changes in asphyxiated newborn infants.

Subunit structure of the erythropoietin receptor

Chemical cross-linking of the red blood cell hormone, erythropoietin (Epo), to its receptor on erythroid cells has revealed the presence of two proteins closely associated with Epo, but the relationship between these two proteins is controversial. Using the cross-linking reagents disuccinimidyl suberate and dithiobissuccinimidyl propionate, we show that 125I-Epo can be specifically conjugated in a complex of 224kDa using mouse fetal liver cells, bone marrow cells, and Friend virus-induced splenic erythroblasts as demonstrated by electrophoresis on sodium dodecyl sulfate-polyacrylamide gels under nonreducing conditions. Under reducing conditions, the 224-kDa complex appeared as two Epo conjugates of 136 kDa and 119 kDa, and these bands were also observed to a variable extent in some nonreducing gels. Disulfide linking of the 136-kDa and 119-kDa bands was confirmed by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis run under nonreducing followed by reducing conditions. With increasing time of 125I-Epo binding to Friend virus erythroblasts in the presence of sodium azide to inhibit receptor internalization, the 136-kDa and 119-kDa bands seen under reducing conditions increased markedly in intensity, whereas the 224-kDa band seen under nonreducing conditions declined. These results suggest that the 224-kDa Epo conjugate is inefficiently solubilized under nonreducing conditions following prolonged periods of Epo binding. A single class of saturable, high affinity receptors for Epo on each of the cell types tested is demonstrated. It is concluded that the two disulfide-linked Epo-binding proteins which can be independently cross-linked to Epo form a single ligand binding site.

Human urinary kallikrein. Complete amino acid sequence and sites of glycosylation

Human glandular kallikrein was purified from urine and subjected to detailed structural characterization. The protein was carboxymethylated with iodoacetic acid and digested with TPCK-trypsin, Staphylococcal aureus V-8 protease and endo LysC peptidase. The resulting peptide fragments were separated by reverse-phase HPLC using C-4 columns and acetonitrile-trifluoroacetic acid gradient elution. The complete amino acid sequence of the carboxymethylated derivative was elucidated by sequence analysis and alignment of peptides derived from different proteolytic cleavages. A procedure using in situ CNBr cleavage of a large endo LysC peptidase-derived peptide followed by direct sequencing was carried out to provide overlap for two glycosylation sites at residues 78 and 84. Three Asn-linked glycosylation sites were confirmed by the direct sequence analysis of the isolated glycopeptides. However, the third glycosylation at Asn-144 occurs only in 60% of kallikrein molecules. Reverse-phase HPLC effectively separates two species of HUK which correspond to molecules glycosylated and non-glycosylated at Asn-144, respectively. The human urinary kallikrein contains 238 amino acid residues with Ile and Ser as N- and C-terminal amino acids, respectively. The primary structure is completely identical to that deduced from a human genomic DNA sequence (F.K. Lin et al., manuscript in preparation) and is different in one amino acid (Lys-162 vs. Glu-162) from that deduced from pancreatic or kidney cDNA sequence.

Expression of specific high-affinity binding sites for erythropoietin on rat and mouse megakaryocytes

Considerable experimental and clinical evidence suggests a relationship between erythropoiesis and thrombopoiesis. This is supported by observations that erythropoietin (Epo), the primary regulator of erythropoiesis, can affect platelet production when injected into animals. In this study we provide experimental evidence for a direct effect of Epo on thrombopoiesis by demonstrating that 125I-labeled recombinant human Epo binds to rat and mouse bone marrow megakaryocytes. Thus, autoradiographic analysis using cold competition to measure specific binding has been used to demonstrate that Epo binding to megakaryocytes increases with megakaryocyte maturation. When corrected for cell size, Epo binding sites per unit surface area increase from Stage I megakaryoblasts to Stage II megakaryocytes, and then remain approximately constant throughout further megakaryocyte maturation. Receptor density on megakaryocytes is similar to that on pronormoblasts in the rat, and in mice is 60% that on pronormoblasts. No binding of Epo to platelets or to naked megakaryocyte nuclei was detected. Equilibrium binding studies with partially purified rat megakaryocytes (20%-40% pure), where megakaryocytes are the only significant Epo binding cell population, showed a single class of saturable, high-affinity binding sites present on average at 6500 binding sites per megakaryocyte with a KD of 287 pM. Binding of [125I]Epo to rat megakaryocytes was inhibited with an antiserum against murine erythroblasts. These results suggest that the effects of Epo on thrombopoiesis may be directly mediated through specific, high-affinity binding sites for Epo on the surface of maturing megakaryocytes.

Expression of high affinity receptors for erythropoietin on human bone marrow cells and on the human erythroleukemic cell line, HEL

The principal growth factor involved in the regulation of erythropoiesis, erythropoietin (Epo), is currently under clinical trial for the treatment of anemia. Despite the advanced state of these trials, little is known about the nature and distribution of the receptor for Epo on human hemopoietic cells or about the cellular mechanisms of signal transduction. In the present study 125I-labeled recombinant human Epo has been used to demonstrate expression of saturable, high affinity binding sites for Epo on density-fractionated human bone marrow cells and on the human erythroleukemic cell line, HEL. Binding was reversible and proportional to cell number, and HEL cells were shown to express on average 34 receptors per cell (range 30-35) with an affinity of 293 pM (range 275-300 pM) at 37 degrees C in the presence of sodium azide to block receptor internalization. Autoradiographic analysis of Epo binding to human bone marrow cells showed that specific binding, measured as the difference in grain counts between total binding and binding in the presence of excess unlabeled Epo, was greatest to pronormoblasts and declined during erythroid cell maturation to undetectable levels on nucleated red cells. Autoradiography also revealed significant Epo binding to marrow megakaryocytes, which comprise less than 1% of nonerythroid cells. In contrast to erythroid cells, Epo binding to megakaryocytes increased with cell maturation, with stage IV megakaryocytes exhibiting the highest specific binding. Grain density per surface area however, remained constant during megakaryocyte maturation and was approximately 25% that on pronormoblasts.

Down-modulation of high-affinity receptors for erythropoietin on murine erythroblasts by interleukin 3

Erythropoiesis is regulated by the glycoprotein hormone erythropoietin (Epo) and by several other factors including interleukin 3 (IL-3) and granulocyte-macrophage colony-stimulating factor. The possibility that IL-3 and GM-CSF may act by modulating Epo receptor expression was investigated using erythroblasts purified from the spleens of phenylhydrazine-treated mice. AT 37 degrees C, in the presence of sodium azide to inhibit receptor internalization. 125I-labeled human recombinant Epo bound to a single class of high-affinity receptors on splenic erythroblasts (450 sites/cell, Kd = 700 pM). Autoradiographic studies indicated that 94% of specifically bound Epo was associated with erythroblasts, decreased Epo binding being observed with increasing erythroid cell maturation. Whereas recombinant mouse IL-3 and GM-CSF did not compete with 125I-Epo for binding to the Epo receptor, preincubation of cells with IL-3 resulted in a concentration-dependent loss of 125I-Epo binding without altering the affinity of residual receptors for Epo. Complete loss of Epo receptors was effected within 2 h at IL-3 concentrations above 2500 U/ml. Preincubation with recombinant mouse GM-CSF had no effect on binding, even at 100,000 U/ml. In comparison, preincubation of cells with Epo (50 U/ml) caused complete loss of 125I-Epo binding within 30-60 min, an effect not explained by receptor saturation with unlabeled Epo. Thus, in addition to trans-down-modulating growth factor receptors of the granulocyte-macrophage series, IL-3 also trans-down-modulates a growth factor receptor of the erythroid lineage.

Effects of recombinant human erythropoietin on megakaryocytes and on platelet production in the rat

The contention that erythropoietin (Epo) affects platelet production was investigated in the rat with recombinant human Epo (rHuEpo). In normal rats, Epo caused a dose-dependent increase in both reticulocyte and platelet numbers, the reticulocyte response preceding that of platelets. Withdrawal of Epo resulted in reticulocytes and platelets returning to control levels. [75Se]-selenomethionine incorporation into platelets was also enhanced in response to Epo. Chronic daily administration of rHuEpo resulted in steady state erythrocyte levels after 12 to 14 days, which were elevated 20% above controls. Attainment of this steady state was associated with both reticulocytes and platelets returning to control levels despite continued administration of Epo, an effect not associated with a change in the half-life of circulating Epo. In polycythemic rats a platelet response was observed before an effect on reticulocytes. Erythropoietin caused a 2.4-fold increase in the frequency of small acetylcholinesterase-positive cells within 24 hours, and increased the mean megakaryocyte diameter within 48 hours. Furthermore, the [3H]-thymidine labeling index of megakaryocytes from rats treated for 24 hours with rHuEpo was increased for all stages of megakaryocyte maturation. These results support the proposal of an effect of Epo on rat megakaryocytes causing increased platelet production.

Expression and modulation of specific, high affinity binding sites for erythropoietin on the human erythroleukemic cell line K562

Erythroid differentiation is mediated by several interacting factors which include the glycoprotein hormone erythropoietin (Epo), interleukin-3 (IL-3) in the mouse, and erythroid-potentiating activity (EPA) in humans. Each of these factors binds to specific cell surface receptors on responsive target cells, but the way in which these factors interact to modulate erythropoiesis is unknown. In the present study, we used the human erythroleukemic cell line K562 to examine expression and regulation of the receptor for Epo using 125I-labeled, bioactive recombinant human Epo. K562 cells expressed low numbers of a single class of high-affinity Epo receptors corresponding to 4 to 6 receptors per K562 cell (KD = 270 to 290 pmol/L). Treatment of K562 cell cultures with medium conditioned by the EPA-secreting cell line U937 (U937CM) increased receptor expression 2.6 to 3.5-fold to 13 to 17 receptors/cell (KD = 260 to 300 pmol/L). That all of the Epo receptor-potentiating activity in U937CM was accounted for by EPA was shown by a similar increase in Epo receptor expression on K562 cells with recombinant EPA. The effect of U937CM on Epo receptors was reversed by culturing cells in inducer-free medium for 3 days. Medium conditioned by the 5637 cell line had no effect on Epo receptors on K562 cells. In methylcellulose culture, U937CM and Epo acted synergistically to increase erythroid differentiation of K562. Similarly, U937CM stimulated human cord blood CFU-E growth under conditions in which Epo was limiting or in excess. Increases in Epo receptor expression on K562 cells and on CFU-E in response to EPA may mediate the effects of Epo on these cells.

High doses of recombinant erythropoietin stimulate platelet production in mice

Previously, recombinant erythropoietin (rEpo) was shown to increase the number and size of megakaryocytic colonies in vitro, and in vivo it elevates the number of megakaryocytes in mouse spleens. To test the hypothesis that rEpo would stimulate platelet production in mice, both normal mice and mice in rebound-thrombocytosis were injected with rEpo and the %35S incorporation into platelets was measured. A thrombocytopoiesis-stimulating factor (TSF or thrombopoietin) was used as a positive control. rEpo increased isotopic incorporation into platelets of both normal mice and mice in rebound-thrombocytosis, as did TSF, but required large doses (15 U rEpo/mouse). In other mice, hematocrits, platelet counts, platelet sizes, and 24-hr %35S incorporation into platelets were measured 2 days after injection of two equally divided doses of either rEpo or TSF. Significant increases in both platelet sizes and %35S incorporation into platelets were found after injections of 15 U rEpo/mouse or 2.3 U TSF/mouse. These data indicate that rEpo, at high doses, will stimulate platelet production in mice, and may suggest molecular similarities between rEpo and TSF and their ability to compete for common receptor sites on megakaryocytes and their progenitor cells.

Chromosomal assignment of the human erythropoietin gene and its DNA polymorphism

Erythropoietin (EPO), a glycoprotein hormone, is the major physiological regulator of erythrocyte production in mammals. A cDNA clone containing the entire human EPO-coding region was used for Southern blot analysis of a series of human-Chinese hamster somatic cell hybrids containing different combinations of human chromosomes. Synteny analysis revealed 100% concordance between the EPO gene and human chromosome 7. Further localization to the region q11-q22 was accomplished by in situ hybridization of 3H-labeled human EPO cDNA to metaphase chromosomes prepared from both human lymphocytes and the cell hybrid 879-2a that contained human chromosomes 5, 7, 9, 12, and 21. In addition, restriction fragment length polymorphisms were detected at a frequency of approximately 20% in a Chinese population using restriction enzymes either HindIII or HinfI. These polymorphisms were inherited in a Mendelian fashion. Thus, the EPO marker is reasonably polymorphic and should be useful in linkage analysis with other genetic markers on chromosome 7, including the locus for cystic fibrosis.

Characterization and biological effects of recombinant human erythropoietin

Human recombinant erythropoietin (rHuEPO) has been purified to apparent homogeneity and compared to purified human urinary erythropoietin (EPO). Both the purified natural and recombinant EPO preparations were characterized in a competition radioimmunoassay (RIA), the exhypoxic polycythemic mouse bioassay, in vitro tissue culture bioassays using bone marrow cells, and by Western analysis. In the immunological and biological activity assays, the rHuEPO shows a dose response which parallels that of the natural hormone. By Western analysis, the recombinant and human urinary EPO migrate identically. Administration of rHuEPO increases the hematocrit of normal mice in a dose-dependent manner. Additionally, the rHuEPO is able to increase the hematocrit of rats made uremic as a result of subtotal nephrectomy. In summary, by all criteria examined, the rHuEPO is biologically active and equivalent to the natural hormone.

Cloning, sequencing, and evolutionary analysis of the mouse erythropoietin gene

The gene for mouse erythropoietin was cloned and sequenced. We present here a preliminary analysis of the overall genomic organization of the coding portions and the two flanking regions of the gene. This is the third mammalian erythropoietin for which the sequence is available, but it represents the first from a nonprimate species. We investigated the evolutionary divergence of sequence and structure of the three erythropoietins and identified specific regions of the molecules that are apparently under various degrees, and perhaps different types, of functional constraint.

Monkey erythropoietin gene: cloning, expression and comparison with the human erythropoietin gene

The erythropoietin (Epo) gene from Cynomolgus monkeys has been isolated from a kidney cDNA library using mixed 20-mer oligodeoxynucleotide probes. The gene encodes a 168 amino acid (aa) mature protein with a calculated Mr of 18,490 and a presumptive signal peptide of 24 aa. The Epo gene, when transfected into Chinese hamster ovary (CHO) cells, produces a glycosylated protein with an apparent Mr of 34,000. The expressed product is biologically active in vivo. The monkey gene exhibits 92% and 94% homology to the human gene at the aa and nucleotide sequence levels, respectively. When compared with the human Epo, monkey Epo has an additional 3-aa residue at the N terminus of the mature protein and a deletion of an internal lysine residue.

Cloning and expression of the human erythropoietin gene

The human erythropoietin gene has been isolated from a genomic phage library by using mixed 20-mer and 17-mer oligonucleotide probes. The entire coding region of the gene is contained in a 5.4-kilobase HindIII-BamHI fragment. The gene contains four intervening sequences (1562 base pairs) and five exons (582 base pairs). It encodes a 27-amino acid signal peptide and a 166-amino acid mature protein with a calculated Mr of 18,399. The erythropoietin gene, when introduced into Chinese hamster ovary cells, produces erythropoietin that is biologically active in vitro and in vivo.

Characterization of duck genome fragments containing beta and epsilon globin genes

We have isolated two allelic duck-genomic DNA fragments containing beta-type globin genes. The beta- and epsilon-globin genes are 1800 bp apart in both fragments, have second introns of 1100 and 1200 bp, respectively, and small first introns. We have also determined approx. 550 nucleotides of the sequence on the 5' side of the beta-globin gene. Comparison with the chicken beta-globin gene suggests sequences of possible significance to gene expression.

The nucleotide sequence of blue-green algae phenylalanine-tRNA and the evolutionary origin of chloroplasts

Phenylalanine tRNA from the blue-green alga, Agmenellum quadruplicatum, has been purified to homogeneity. The nucleotide sequence of this tRNA was determined to be: (see tests) Comparisons of the sequence and the modified nucleosides of this tRNA with those of other tRNAPhes thus far sequenced, indicate that this blue green algal tRNAPhe is typically prokaryotic and closely resembles the chloroplast tRNAPhes of higher plants and Euglena. The significance of this observation to the evolutionary origin of chloroplasts is discussed.

The nucleotide sequence of two bovine lens phenylalanine tRNAs. Possible activation of a new phenylalanine tRNA gene during differentiation of lens cells

Bovine lens fiber cells contain two major isoacceptors of phenylalanine tRNA, tRNA1Phe and tRNA2Phe whereas lens epithelial cells contain mainly tRNA2Phe (Ortwerth, B.J,, Yonuschot, G.R., Heidlege, J.F., Chu-Der, O.M.Y., Juarez, D., and Hedgcoth, C. (1975) Exp. Eye Res. 20, 417-426). Thus, the induction of a new species of tRNAPhe accompanies the differentiation of lens cells in vivo. These two species of tRNAPhe have been purified and their sequences have been analyzed. The results of the analyses show that the sequence of tRNA2Phe is identical with beef liver tRNAPhe while tRNA1Phe differs from tRNA2Phe by a guanosine to adenosine substitution at position 57. Therefore, the T psi CG sequence in the ribosylthymine loop of tRNA2Phe is replaced by T psi CA in tRNA1Phe, This observation demonstrates a case in which a change in sequence of tRNA isoacceptors accompanies cell development rather than changes in the level of post-transcriptional modification as noted in other systems (reviewed by Osterman L.A. (1979) Biochimie (Paris) 61, 323-342). The conversion of guanosine to adenosine in the ribosylthymine loop of lens tRNA1Phe suggests a possible activation of a new tRNAPhe gene during the differentiation of lens cells, although the possibility that this replacement may be catalyzed by a transglycosylase type enzyme has not been ruled out.

Differences between transfer RNA methylase activity in human diploid fibroblasts during in vitro and in vivo aging

The change of the specific activity of S-adenosylmethionine: tRNA methyltransferase in cultures of human diploid fibroblasts at different passages has been measured and compared with that in the same type of cells derived from donors of different ages. Whereas the specific activity of tRNA methylase in the in vitro aged cells was found to decline gradually with increasing passage number of the culture, a different activity--age relationship was observed for this enzyme in cells derived from donors of different ages. The activity of tRNA methylase is high in the fetal cells and drops drastically in the "newborn" cells. After a further 10% decline, the activity of this enzyme reaches a steady low level in the postnatal cells from donors ranging in age from 3 months to 94 years. These findings cast doubt on the validity of the assumption that the results obtained from in vitro aging experiments reflect the biochemistry of aging in vivo. The "fetal" enzyme can methylate the "aged" tRNA but the "aged" enzyme cannot methylate the "fetal" tRNA. The fetal cells contain enzyme activities specific for the formation of m1A, m5C and m1G. These activities are low or deficient in "aged" cells. Control experiments showed that all of these results are due neither to the presence of inhibitor or stimulator in the extract nor to effects related to the population density, sex or growth rate of the culture.

Cell cycle-related hormone carcinogen interaction during chemical carcinogen induction of nodule-like mammary lesions in organ culture

The immature mammary glands of BALB/c female mice were treated with 7,12-dimethylbenz[a]anthracene (DMBA), 2 micrograms/ml, or 3-methylcholanthrene (10 micrograms/ml) for a 24-hr period at different times during the inital six days of lobuloalveolar growth in hormone-supplemented organ culture. Nodule-like alveolar lesions (NLAL) were detectable in 80% of the glands treated with DMBA (40% in 3-methylcholanthrene-treated glands) in the presence of insulin + prolactin + aldosterone + cortisol in the medium. No NLAL were present in dimethyl sulfoxide-treated control glands cultivated with the same hormones. The hormone combination insulin + prolactin + cortisol was unfavorable for NLAL induction by DMBA, and the combination of aldosterone + insulin + prolactin was only moderately conducive. Thus, the presence of cortisol with insulin + prolactin + aldosterone enhances NLAL incidence of mammary cells by DMBA. The highest incidence was found in glands that were treated with DMBA for 24 hr between the third and fourth day of culture, the period corresponding to the onset of the second wave of DNA synthesis in the gland. Cytotoxicity of DMBA was pronounced between 24 and 48 hr, when a high frequency of cells were in DNA synthesis, and survival of the cells after the cytotoxic effect of DMBA appeared to play a role in NLAL incidence. This suggests that DMBA-induction of NLAL in mammary glands in organ culture involves a complex carcinogen-hormone-cell cycle interaction. We emphasize that, although NLAL morphologically resembles the hyperplastic alveolar nodules of mouse mammary gland in vivo, the abilitity of NLAL to produce typical hyperactive alveolar outgrowth and mammary tumor after transplantation iv vivo remains to be determined.