Discovery of New Isotopes

Using the fusion-evaporation reaction ^{106}Cd(^{58}Ni,4n)^{160}Os and the gas-filled recoil separator SHANS, two new isotopes _{76}^{160}Os and _{74}^{156}W have been identified. The α decay of ^{160}Os, measured with an α-particle energy of 7080(26) keV and a half-life of 201_{-37}^{+58} µs, is assigned to originate from the ground state. The daughter nucleus ^{156}W is a ß^{+} emitter with a half-life of 291_{-61}^{+86} ms. The newly measured α-decay data allow us to derive α-decay reduced widths (δ^{2}) for the N=84 isotones up to osmium (Z=76), which are found to decrease with increasing atomic number above Z=68. The reduction of δ^{2} is interpreted as evidence for the strengthening of the N=82 shell closure toward the proton drip line, supported by the increase of the neutron-shell gaps predicted in theoretical models.

[Diagnosis and treatment of Chlamydia psittaci pneumonia: experiences of 8 cases].

Objective: In order to improve the understanding and clinical treatment of Chlamydia psittaci pneumonia, we analyzed the clinical manifestations, laboratory test results and imaging features of 8 patients. Methods: We collected the clinical data of 8 patients with Chlamydia psittaci pneumonia diagnosed by metagenomic next-generation-sequencing (mNGS) from November 2018 to February 2020, including clinical features, chest CT scan, pathological features and antibiotic use. Results: A total of one male and 7 females, aged from 45 to 85 years(median 62 years), were included in this study. All the patients had high fever, cough and most had expectoration (6/8). The leukocyte count and PCT level were mostly normal (7/8). However, we observed decreased lymphocyte count(5/8), elevated C-reactive protein in all patients, and increased ESR in most patients (7/8). The chest CT of all the patients showed large patchy consolidation, with one case having pleural effusion. The pathological manifestations were nonspecific, showing infiltration of inflammatory cells and exudation. Moxifloxacin and/or doxycycline were administered after diagnosis, and the course of treatment lasted from 14 to 21 days.Chest CT showed absorption of lesions following treatment Conclusions: Chlamydia psittaci pneumonia showed certain characteristics, including high fever with pulmonary patchy consolidation, and normal white blood cell count. Molecular diagnostic methods such as mNGS could lead to rapid diagnosis and treatment which can shorten the course of hospitalization and thus improve prognosis.

New α-Emitting Isotope

A new α-emitting isotope ^{214}U, produced by the fusion-evaporation reaction ^{182}W(^{36}Ar,4n)^{214}U, was identified by employing the gas-filled recoil separator SHANS and the recoil-α correlation technique. More precise α-decay properties of even-even nuclei ^{216,218}U were also measured in the reactions of ^{40}Ar, ^{40}Ca beams with ^{180,182,184}W targets. By combining the experimental data, improved α-decay reduced widths δ^{2} for the even-even Po-Pu nuclei in the vicinity of the magic neutron number N=126 are deduced. Their systematic trends are discussed in terms of the N_{p}N_{n} scheme in order to study the influence of proton-neutron interaction on α decay in this region of nuclei. It is strikingly found that the reduced widths of ^{214,216}U are significantly enhanced by a factor of two as compared with the N_{p}N_{n} systematics for the 84≤Z≤90 and N<126 even-even nuclei. The abnormal enhancement is interpreted by the strong monopole interaction between the valence protons and neutrons occupying the π1f_{7/2} and ν1f_{5/2} spin-orbit partner orbits, which is supported by the large-scale shell model calculation.

High-Density Genetic Map Construction and Identification of QTLs Controlling Oleic and Linoleic Acid in Peanut using SLAF-seq and SSRs.

The cultivated peanut, A. hypogaea L., is an important oil and food crop globally.High-density genetic linkage mapping is a valuable and effective method for exploring complex quantitative traits. In this context, a recombinant inbred line (RIL) of 146 lines was developed by crossing Huayu28 and P76. We developed 433,679 high-quality SLAFs, of which 29,075 were polymorphic. 4,817 SLAFs were encoded and grouped into different segregation patterns. A high-resolution genetic map containing 2,334 markers (68 SSRs and 2,266 SNPs) on 20 linkage groups (LGs) spanning 2586.37 cM was constructed for peanut. The average distance between adjacent markers was 2.25 cM. Based on phenotyping in seven environments, QTLs for oleic acid (C18:1), linoleic acid (C18:2) and the ratio of oleic acid to linoleic acid (O/L) were identified and positioned on linkage groups A03, A04, A09, B09 and B10. Marker2575339 and Marker2379598 in B09 were associated with C18:1, C18:2 and O/L in seven environments, Marker4391589 and Marker4463600 in A09 were associated with C18:1, C18:2 and O/L in six environments. This map exhibits high resolution and accuracy, which will facilitate QTL discovery for essential agronomic traits in peanut.

[Metabolomics study of tris(2-chloroethyl) phosphate induced hepaotoxicity and nephrotoxicity in Sprague-Dawley rats].

Objective: To discuss the potential toxic target organ and the toxic effects and mechanisms of tris (2-chloroethyl) phosphate (TCEP) on SD rats. Methods: 40 female SD rats weaning from milk for 21 days, weighted (50±2.3)g were selected as subjects and marked by the weight. They were randomly divided into 4 groups, namely control group, 50 (L), 100 (M) and 250 (H) mg·kg(-1)·d(-1) dose of TCEP group. Each group has 10 rats, and administrated the corresponding dose of drug or vehicle by mouth, quaque die for 60 days. All rats were sacrificed after the last administration. The livers and kidneys were dyed by HE for pathological observation; and the blood samples were collected to analyze the biochemical index. H(1)-Nuclear Magnetic Resonance ((1)H-NMR)-based metabolomics methods coupling with histopathogy examination were used to investigate the toxic effects of TCEP. Results: Inflammatory cell infiltration and hepatic necrosis were observed in the liver of TCEP-treated rats. Inflammatory cells invaded and calcification/ossification foci were also found in renal of TCEP-treated rats and tumor hyperplasia were existed in renal tubule in H group. The level of HDL-C in the L, M and H group were separately (1.7±0.09) , (1.5±0.07) and (1.3±0.1) µmol/L, which were all significantly lower than that of control group ( (1.9±0.2) µmol/L) (P<0.05) . The activity of cholinesterase (CHE) in the L, M and H group were separately (918±14.8) , (828±28.6) and (674±36.5) U/L, which were all significantly lower than that of control group ((1056±28.8) µmol/L) (P<0.05). Moreover, The level of creatinine (CRE) in the L, M and H group were separately (29.8±4.6) , (28.9±5.3) and (25.8±6.2) µmol/L, which were all significantly lower than that of control group ((30.2±3.9) µmol/L) (P<0.05). In the H group, the enzyme activities of alanine aminotransferase (ALT), lactate dehydrogenase (LDH), creatine kinase (CK), alkaline phosphatase (ALP) and the contents of total bilirubin (TBIL), glucose (GLU) and uric acid (UA) were all significantly higher than the results in control group. The results of (1)H-NMR metabolomics showed that the contents of lactate, glycine, high-density lipoprotein, low-density lipoprotein and phosphatidylcholine in blood of rats would decrease by TCEP exposure, while N-acetylglycoprotein, acetate, alanine, glucose, lipids, lipoproteins and fatty acids would increase. Conclusion: TCEP caused disorders in endogenous energy metabolism, leading to the pathological changes of inflammatory cells infiltration and necrosis in liver and kidney, caused enzyme activity changes of ALT, ALP and the content changes of other liver and kidney injury-related markers.

[Epidemiological characteristics of diarrheagenic Escherichia coli among diarrhea outpatients in China, 2012-2015].

Objective: To understand the epidemiological characteristics of diarrheagenic Escherichia (E.) coli (DEC) among diarrhea outpatients in China. Methods: Diarrhea surveillance program was conducted in outpatient and emergency departments from 170 hospitals that under the sentinel programs in 27 provinces, from 2012-2015. Clinical and epidemiological data regarding diarrhea patients were collected, with fecal specimens sampled and tested for DEC in 92 network-connected laboratories. Results: Among all the 46 721 diarrhea cases, 7.7% of them appeared DEC positive in those with geographic heterogeneity. In 2 982 cases (6.4%) with available data on PCR subtypes of DEC, enteroaggregative E. coli (EAEC, 1 205 cases, 40.4%) appeared the most commonly seen pathogens, followed by enteropathogenic E. coli (EPEC, 815 cases, 27.3%), and enterotoxigenic E.coli (ETEC, 653 cases, 21.9%). The highest positive rate of DEC was observed in outpatients of 25-34 years old (10.1%), living in the warm temperate zones (11.1%), and with mucous-like stool (9.4%). The positive rate of DEC showed a strong seasonal pattern, with peaks in summer, for all the subtypes. Conclusions: DEC seemed easy to be detected among diarrhea outpatients in China, with EAEC, EPEC and ETEC the most commonly identified subtypes. Epidemiological characteristics regarding the heterogeneities of DEC appeared different, in regions, age groups and seasons. Long-term surveillance programs should be strengthened to better understand the epidemiology of DEC, in China.

[Drug resistance and influencing factors in adult AIDS patients receiving antiretroviral treatment in Dehong, Yunnan province].

OBJECTIVE: To investigate the incidence of drug resistance in adult AIDS patients receiving antiretroviral treatment(ART)and influencing factors in Dehong prefecture, Yunnan province during 2012-2014. METHODS: For this cohort study, all the AIDS patients aged over 15 and receiving ART in Dehong were screened for HIV drug resistance in 2012, and 3 715 patients who had received ART for more than 6 months were enrolled for 12 months and 24 months follow up. RESULTS: Among the 3 715 patients, 56.6% were males, 72.6% were aged 26-45 years and 76.0% were married. The main treatment regimen was nevirapine(NVP)+ lamivudine(3TC)+ zidovudine(AZT)(38.2%). A total of 3 556 patients(95.7%)received at least one viral load testing during the two years follow-up, among them 253(7.1%)patients had VL≥1 000 copies/ml, in which 211(83.4%)received drug resistance related gene mutation testing, the results indicated that the drug resistance developed in 52 and 39 patients in 2013 and 2014(1.43 per 100 person years and 0.88 per 100 person years)respectively. The overall HIV drug incidence was 1.13 per 100 person years. Multivariate regression analysis indicated that age ≤25 years, to be infected through drug use, treatment regimen as D4T+ 3TC +NVP and baseline CD4(+) T cells ≤200 cells/µl were the risk factor of HIV drug resistance. Eleven HIV gene subtypes were detected in the 82 patients with newly developed drug resistance, CRF_BC was predominant(31.7%), followed by CRF01_AE(22.0%)and C(19.5%). Ten patients were infected with mixed subtypes of CRF_BC/B', CRF_BC/CRF_01B and CRF_BC/C. Most of the 82 patients were resistant to NRTIs and NNRTIs, the main mutation loci were M184V and K103N. CONCLUSIONS: The incidence of drug resistance in adult AIDS patients receiving ART was relatively low in Dehong. However, it is necessary to conduct the health education in young people and drug users to improve the treatment compliance and strengthen the surveillance for HIV drug resistance.

Study of the relationship between IL-10 polymorphism and serum lipoprotein levels in Han Chinese individuals.

Previous studies have shown that cytokines can affect serum lipoprotein concentrations. The aim of this study was to examine the association between IL-10 gene polymorphisms and serum lipoprotein levels of Han Chinese individuals. A total of 359 Han Chinese people were enrolled in this investigation. IL-10 -592, -819, and -1082 genotypes were established using polymerase chain reaction-restriction fragment length polymorphism analysis. An automatic biochemistry analyzer was used to determine serum concentrations of total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), and very low-density lipoprotein (VLDL) in each individual. We observed that the three IL-10 polymorphisms did not significantly differ in terms of age or age of carrier (P > 0.05), and the -592 and -819 variants did not significantly affect serum lipoprotein levels (P > 0.05). HDL concentrations were higher and TG levels were lower in carriers of the -1082 GA genotype compared to those with the AA genotype, and these differences were statistically significant (P < 0.05). However, TC, VLDL, and LDL levels were unaffected by this sequence variation (P > 0.05). Our results suggest that the polymorphism at position -1082 in the promoter region of IL-10 may affect serum HDL and TG concentrations, while other variants of this gene appear to have no relationship with serum lipoprotein levels.

Breeding of a target genotype variety based on identified chalkiness marker-QTL associations in rice (Oryza sativa L.).

The aim of this study was to breed a target genotype variety based on the identified chalkiness marker-QTL (quantitative trait locus) associations in rice. First, a permanent mapping population of rice that consisted of 525 recombinant inbred lines (RILs), which were derived from Zhenshan 97/Minghui 63, was used to identify QTLs with additive effects for rice quantitative traits and percentage of grain chalkiness (PGC). Subsequently, based on the identified QTLs in rice, the molecular marker 68923-PGC was selected to screen the low chalkiness rice line. Then, using the integration of molecular marker breeding and traditional breeding, we analyzed the genotype and phenotype of inbred lines from 525 RILs; we identified one rice variety with particularly high yields, good taste, and broad adaptability. The new variety was temporarily named RIL10, which was a high quality, high yield, and broadly adaptable variety, and it is predominantly a feature that has contributed to its geographical adaptability, which would be planted from 35°E to 18°E in Chinain China, where 2/3 of rice production occurs. RIL10 was a marker-assisted selection breeding achievement for producing a high quality, high yield, and broadly adaptable rice variety.

Marking Drosophila suzukii (Diptera: Drosophilidae) With Rubidium or 15N.

Drosophila suzukii Matsumura (Diptera: Drosophilidae) has caused significant economic damage to berry and stone fruit production regions. Markers that are systemic in plants and easily transferred to target organisms are needed to track D. suzukii exploitation of host resources and trophic interactions. High and low concentrations of the trace element, rubidium (Rb), and the stable isotope, 15N, were tested to mark D. suzukii larvae feeding on fruits of enriched strawberry plants grown in containers under greenhouse conditions. Fly marker content and proportion of flies marked 1, 7, and 14 d after emergence from enriched fruits and fly dry mass were analyzed. Nearly 100% of the flies analyzed 14 d after emerging from 15N-enriched plants were marked, whereas only 30-75% and 0-3% were marked 14 d after emerging from high and low Rb concentration plants, respectively. Rapid Rb decay, strong 15N persistence, and the economics of using these markers in the field to elucidate D. suzukii pest ecology are discussed.

The dissemination mode of drug-resistant genes in Enterobacter cloacae.

BACKGROUND: Enterobacter cloacae (E. cloacae) infection has the highest mortality rate among Enterobacter infections. This study aimed to determine the prevalence and the transmission route of the class I integron, qnr genes, and CTX-M ESBLs genes in clinical isolates and to analyse the association between the prevalence of MDR genes and the antibiotic resistance of E. cloacae. MATERIALS AND METHODS: The antibiotic susceptibility was tested the agar dilution method. The class I integron, qnr genes, and CTX-M ESBLs genes were detected by polymerase chain reaction (PCR). The prevalence data were analysed with the Chi-square test. RESULTS: In the 100 clinical isolates, the class I integron-positive rate was 65%, with 12% on chromosome, 15% on plasmids and 38% on both. The positive rate of qnr genes was 37% with plasmid location. The positive rates for qnrA, qnrB and qnrS were 6%, 23% and 8%, respectively. The CTX-M ESBLs-positive rate was 34%. For CTX-M-1 ESBLs, 15% were on chromosome, 6% on plasmids and 4% on both; for CTX-M-9 ESBLs, 1% was on chromosome and 7% on plasmid; for CTX-M-25 ESBLs, 3% were on chromosome and 1% on plasmid. CONCLUSION: Antibiotic resistance genes may be horizontally and vertically disseminated among E. cloacae, which helps multidrug-resistant (MDR) strains of E. cloacae to be successful nosocomial agents.

Regulation of autophagy by miR-30d impacts sensitivity of anaplastic thyroid carcinoma to cisplatin.

miR-30d has been observed to be significantly down-regulated in human anaplastic thyroid carcinoma (ATC), and is believed to be an important event in thyroid cell transformation. In this study, we found that miR-30d has a critical role in modulating sensitivity of ATC cells to cisplatin, a commonly used chemotherapeutic drug for treatment of this neoplasm. Using a mimic of miR-30d, we demonstrated that miR-30d could negatively regulate the expression of beclin 1, a key autophagy gene, leading to suppression of the cisplatin-activated autophagic response that protects ATC cells from apoptosis. A reporter gene assay demonstrated that the binding sequences of miR-30d in the beclin 1-3' UTR was the region required for the inhibition of beclin 1 expression by this miRNA. We further showed that inhibition of the beclin 1-mediated autophagy by the miR-30d mimic sensitized ATC cells to cisplatin both in vitro (cell culture) and in vivo (animal xenograft model). These results suggest that dysregulation of miR-30d in ATC cells is responsible for the insensitivity to cisplatin by promoting autophagic survival. Thus, miR-30d may be exploited as a potential target for therapeutic intervention in the treatment of ATC.

Pentamethylquercetin generates beneficial effects in monosodium glutamate-induced obese mice and C2C12 myotubes by activating AMP-activated protein kinase.

AIMS/HYPOTHESIS: Pentamethylquercetin (PMQ) has recently been shown to have glucose-lowering properties. Here, we aimed to characterise the effectiveness and underlying mechanisms of PMQ for ameliorating metabolic disorders in vivo and vitro. METHODS: We generated a mouse model of obesity by neonatal administration of monosodium glutamate (MSG) and used it to assess the properties of PMQ as a treatment for metabolic disorders. We also investigated the possible underlying mechanisms of PMQ in the prevention of metabolic disorders. RESULTS: Compared with normal mice, MSG mice had metabolic disorders, including central obesity, hyperinsulinaemia, insulin resistance, hyperglycaemia, hyperlipidaemia, decreased phosphorylation of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC), and downregulated levels of GLUT4 in gastrocnemius muscles. In MSG mice, PMQ treatment (5, 10, 20 mg/kg daily) reduced body weight gain, waist circumference, adipose tissue mass, serum glucose, triacylglycerol and total cholesterol, while improving insulin resistance, activating AMPK and increasing ACC phosphorylation and GLUT4 abundance. In C2C12 myotubes, PMQ (10 µmol/l) increased glucose consumption by ∼65%. PMQ treatment (1-10 µmol/l) also activated AMPK, increased ACC phosphorylation and GLUT4 abundance, and upregulated the expression of some key genes involved in fatty acid oxidation. CONCLUSIONS/INTERPRETATION: These findings suggest that PMQ can ameliorate metabolic disorders at least in part via stimulation of AMPK activity.

Design of two-dimensional tunable photonic crystals with multiple functionalities.

Negative refraction is an interesting phenomenon which can provide sub-wavelength imaging and a novel way to control the propagation path of photons. Photonic crystals have been intensively researched to achieve negative refraction. In this article, we present design and simulations of a new two-dimensional tunable photonic crystal obtained using the plane wave expansion method. The newly designed photonic crystals exhibit tunability among positive, zero, and negative refractions, when liquid crystals infiltrated in the structures are electrically tuned. The equifrequency surface diagrams of the designed photonic crystal unveil the refraction direction of photons in the structures. The tunability is further confirmed using the finite-difference time-domain simulation.

Comparison of three current sources for single-electrode capacitance measurement.

The capacitance of a single electrode is usually measured by injecting a current to the electrode and measuring the resultant voltage on the electrode. In this case, a voltage-controlled current source with a high bandwidth is needed because the impedance is inversely proportional to the excitation frequency. In this design note, three different current sources are discussed: (1) the Howland current source, (2) a modified Howland current source, and (3) a dual op-amp current source. The principle and dynamic performances are presented and compared. Simulation and experimental results show that although the Howland current source has the lowest (i.e., worst) output impedance, its output is the most stable among the three current sources when the frequency changes. Therefore, it is suitable for single-electrode capacitance measurement. Initial tests have proven the feasibility of single-electrode capacitance sensor with the Howland current source.

Self-aligned growth of single-walled carbon nanotubes using optical near-field effects.

Self-aligned growth of ultra-short single-walled carbon nanotubes (SWNTs) was realized by utilizing optical near-field effects in a laser-assisted chemical vapor deposition (LCVD) process. By introducing the optical near-field effects, bridge structures containing single suspended SWNT channels were successfully fabricated through the LCVD process at a relatively low substrate temperature. Raman spectroscopy and I-V analyses have been carried out to characterize the SWNT-bridge structures. Numerical simulations using a high-frequency structure simulator revealed that significant enhancement of local heating occurs at metallic electrode tips under laser irradiation; it is about one order of magnitude higher than that in the rest of the electrodes. This technique suggests a novel approach to in situ low-temperature fabrication of SWNT-based devices in a precisely controlled manner, based on the nanoscale heating enhancement induced by the optical near-field effects.

Catalyst-free synthesis of well-aligned ZnO nanowires on In0.2Ga0.8N, GaN, and Al0.25Ga0.75N substrates.

Well-aligned ZnO nanowires have been synthesized vertically on In0.2Ga0.8N, GaN, and Al0.25Ga0.75N substrates, using a catalyst-free carbon thermal-reduction vapor phase deposition method for the first time. The as-synthesized nanowires are single crystalline wurtzite structure, and have a growth direction of [0001]. Each nanowire has a smooth surface, and uniform diameter along the growth direction. The average diameter and length of these nanowires are 120-150 nm, and 3-10 )m, respectively. We suggest that the growth mechanism follow a self-catalyzing growth model. Excitonic emission peaked around 385 nm dominates the room-temperature photoluminescence spectra of these nanowires. The room-temperature photoluminescence and Raman scattering spectra show that these nanowires have good optical quality with very less structural defects.

Reovirus as an experimental therapeutic for brain and leptomeningeal metastases from breast cancer.

Brain and leptomeningeal metastases are common in breast cancer patients and our current treatments are ineffective. Reovirus type 3 is a replication competent, naturally occurring virus that usurps the activated Ras-signaling pathway (or an element thereof) of tumor cells and lyses them but leaves normal cells relatively unaffected. In this study we evaluated reovirus as an experimental therapeutic in models of central nervous system (CNS) metastasis from breast cancer. We found all breast cancer cell lines tested were susceptible to reovirus, with > 50% of these cells lysed within 72 h of infection. In vivo neurotoxicity studies showed only mild local inflammation at the injection site and mild communicating hydrocephalus with neither diffuse encephalitis nor behavioral abnormalities at the therapeutically effective dose of reovirus (intracranial) (ie 10(7) plaque-forming units) or one dose level higher. In vivo, a single intratumoral administration of reovirus significantly reduced the size of tumors established from two human breast cancer cell lines and significantly prolonged survival. Intrathecal administration of reovirus also remarkably prolonged survival in an immunocompetent racine model of leptomeningeal metastases. These data suggest that the evaluation of reovirus as an experimental therapeutic for CNS metastases from breast cancer is warranted.

Diurnal changes in gas exchange and carbon partitioning in needles of fast- and slow-growing families of loblolly pine (Pinus taeda).

We investigated diurnal and seasonal changes in carbon acquisition and partitioning of recently assimilated carbon in fast- and slow-growing families of loblolly pine (Pinus taeda L.) to determine whether fast-growing families exhibited greater carbon gain at the leaf level. Since planting on a xeric infertile site in Scotland County, NC, USA in 1993, five Atlantic Coastal Plain (ACP) and five "Lost Pines" Texas (TX) families have been grown with either optimal nutrition or without fertilization (control). In 1998 and 1999, gas exchange parameters were monitored bimonthly in four families and needles were analyzed bimonthly for starch and soluble sugar concentrations. Although diurnal and seasonal effects on net photosynthesis (A(net)) and maximum rate of light-saturated photosynthesis (A(max)) were significant, few family or treatment differences in gas exchange characteristics were observed. The A(net) peaked at different times during the day over the season, and A(max) was generally highest in May. Instantaneous water-use efficiency (WUE(i)), derived from gas exchange parameters, did not differ among families, whereas foliage stable isotope composition (delta(13)C) values suggested that TX families exhibited lower WUE than more mesic ACP families. Although there were no diurnal effects on foliar starch concentrations, needles exhibited pronounced seasonal changes in absolute concentrations of total nonstructural carbohydrates (TNC), starch and soluble sugars, and in partitioning of TNC to starch and sugars, mirroring seasonal changes in photosynthesis and shoot and root growth. In all families, foliar starch concentrations peaked in May and decreased to a minimum in winter, whereas reducing sugar concentrations were highest in winter. Some family and treatment differences in partitioning of recently assimilated carbon in needles were observed, with the two TX families exhibiting higher concentrations of TNC and starch and enhanced starch partitioning compared with the ACP families. We conclude that growth differences among the four families are not a function of differences in carbon acquisition or partitioning at the leaf level.

Chemosensory signal transduction in paramecium.

Paramecia are ciliated single-cell eukaryotic organisms that can respond to chemical cues in their environment. Glutamate is among those cues, which attract cells. We describe briefly here the following attributes of glutamate chemoresponse: 1) Cells are attracted to L-glutamate relative to KCl at high concentrations of glutamate. 2) There are at least two specific, relatively low affinity glutamate binding sites on the cell surface. Glutamate can be displaced from only one of the binding sites by inosine monophosphate (IMP), and quisqualate displaces glutamate from the second site, which is likely to be the glutamate receptor involved in attraction to glutamate. 3) IMP is a repellent and does not act synergistically with glutamate, whereas guanosine monophosphate (GMP) does. 4) Similarly, glutathione is an attractant, but glutamate and glutathione appear to use different transduction pathways. 5) Glutamate hyperpolarizes the cell. The ionic mechanism is not yet verified, but is likely to involve a K conductance. 6) Glutamate induces a rapid and robust increase in cAMP in the cell. Protein kinase A (PKA) is possibly involved in the transduction pathway because kinase inhibitors such as H7 and H8 inhibit glutamate response, but do not affect responses to other attractants, such as acetate and ammonium. Activation of PKA by the rapid rise in cAMP may sustain the hyperpolarization phosphorylation and activation of the plasma membrane calcium pump. 7) Candidate glutamate binding proteins are being identified among the cell surface proteins with the use of affinity chromatography.