Rational Design of 2D Metal Halide Perovskites with Low Congruent Melting Temperature and Large Melt-Processable Window

Metal halide perovskites (MHPs) have garnered significant attention due to their distinctive optical and electronic properties, coupled with excellent processability. However, the thermal characteristics of these materials are often overlooked, which can be harnessed to cater to diverse application scenarios. We showcase the efficacy of lowering the congruent melting temperature (Tm) of layered 2D MHPs by employing a strategy that involves the modification of flexible alkylammonium through N-methylation and I-substitution. Structural-property analysis reveals that the N-methylation and I-substitution play pivotal roles in reducing hydrogen bond interactions between the organic components and inorganic parts, lowering the rotational symmetry number of the cation and restricting the residual motion of the cations. Additional I···I interactions enhance intermolecular interactions and lead to improved molten stability, as evidenced by a higher viscosity. The 2D MHPs discussed in this study exhibit low Tm and wide melt-processable windows, e.g., (DMIPA)2PbI4 showcasing a low Tm of 98 °C and large melt-processable window of 145 °C. The efficacy of the strategy was further validated when applied to bromine-substituted 2D MHPs. Lowering the Tm and enhancing the molten stability of the MHPs hold great promise for various applications, including glass formation, preparation of high-quality films for photodetection, and fabrication of flexible devices.

Abundant pleiotropy across neuroimaging modalities identified through a multivariate genome-wide association study

Genetic pleiotropy is abundant across spatially distributed brain characteristics derived from one neuroimaging modality (e.g. structural, functional or diffusion magnetic resonance imaging [MRI]). A better understanding of pleiotropy across modalities could inform us on the integration of brain function, micro- and macrostructure. Here we show extensive genetic overlap across neuroimaging modalities at a locus and gene level in the UK Biobank (N = 34,029) and ABCD Study (N = 8607). When jointly analysing phenotypes derived from structural, functional and diffusion MRI in a genome-wide association study (GWAS) with the Multivariate Omnibus Statistical Test (MOSTest), we boost the discovery of loci and genes beyond previously identified effects for each modality individually. Cross-modality genes are involved in fundamental biological processes and predominantly expressed during prenatal brain development. We additionally boost prediction of psychiatric disorders by conditioning independent GWAS on our multimodal multivariate GWAS. These findings shed light on the shared genetic mechanisms underlying variation in brain morphology, functional connectivity, and tissue composition.

Room-Temperature Anisotropic Actuation Driven by a Synergistic Order-Disorder and Displacive Phase Transition in a Ferroelectric Crystal

Actuating materials convert different forms of energy into mechanical responses. To satisfy various application scenarios, they are desired to have rich categories, novel functionalities, clear structure-property relationships, fast responses, and, in particular, giant and reversible shape changes. Herein, we report a phase transition-driven ferroelectric crystal, (rac-3-HOPD)PbI3 (3-HOPD = 3-hydroxypiperidine cation), showing intriguingly large and anisotropic room-temperature actuating behaviors. The crystal consists of rigid one-dimensional [PbI3] anionic chains running along the a-axis and discrete disk-like cations loosely wrapping around the chains, leaving room for anisotropic shape changes in both the b- and c-axes. The shape change is switched by a ferroelectric phase transition occurring at around room temperature (294 K), driven by the exceptionally synergistic order-disorder and displacive phase transition. The rotation of the cations exerts internal pressure on the stacking structure to trigger an exceptionally large displacement of the inorganic chains, corresponding to a crystal lattice transformation with length changes of +24.6% and -17.5% along the b- and c-axis, respectively. Single crystal-based prototype devices of circuit switches and elevators have been fabricated by exploiting the unconventional negative temperature-dependent actuating behaviors. This work provides a new model for the development of multifunctional mechanically responsive materials.

Tuning ferroelectric phase transition temperature by enantiomer fraction

Tuning phase transition temperature is one of the central issues in phase transition materials. Herein, we report a case study of using enantiomer fraction engineering as a promising strategy to tune the Curie temperature (TC) and related properties of ferroelectrics. A series of metal-halide perovskite ferroelectrics (S-3AMP)x(R-3AMP)1-xPbBr4 was synthesized where 3AMP is the 3-(aminomethyl)piperidine divalent cation and enantiomer fraction x varies between 0 and 1 (0 and 1 = enantiomers; 0.5 = racemate). With the change of the enantiomer fraction, the TC, second-harmonic generation intensity, degree of circular polarization of photoluminescence, and photoluminescence intensity of the materials have been tuned. Particularly, when x = 0.70 - 1, a continuously linear tuning of the TC is achieved, showing a tunable temperature range of about 73 K. This strategy provides an effective means and insights for regulating the phase transition temperature and chiroptical properties of functional materials.

Halogen Substitution Regulates High Temperature Dielectric Switch in Lead-Free Chiral Hybrid Perovskites

Hybrid metal halides (HMHs) based phase transition materials have received widespread attention due to their excellent performance and potential applications in energy harvesting, optoelectronics, ferroics, and actuators. Nevertheless, effectively regulating the properties of phase transitions is still a thorny problem. In this work, two chiral lead-free HMHs (R-3FP)2 SbCl5 (1; 3FP=3-fluoropyrrolidinium) and (R-3FP)2 SbBr5 (2) were synthesized. By replacing the halide ions in the inorganic skeleton, the phase transition temperature of 2 changes with an increase of about 20 K, compared with 1. Meanwhile, both compounds display reversible dielectric switching properties. Through crystal structure analysis and Hirshfeld surface analysis, their phase transitions are ascribed to the disorder of the cations and deformation of the inorganic chains.

A Two-Dimensional Hybrid Lead Bromide Ferroelectric Semiconductor with an Out-of-Plane Polarization

A two-dimensional (2D) organic-inorganic hybrid perovskite (OIHP) material with out-of-plane ferroelectricity is the key to the miniaturization of vertical-sandwich-type ferroelectric optoelectronic devices. However, 2D OIHP ferroelectrics with out-of-plane polarization are still scarce, and effective design strategies are lacking. Herein, we report a novel 2D Dion-Jacobson perovskite ferroelectric semiconductor synthesized by a rigid-to-flexible cationic tailoring strategy, achieving an out-of-plane polarization of 1.7 μC/cm2 and high photoresponse. Integrating out-of-plane ferroelectricity with excellent photoelectric properties affords a promising platform to investigate ferroelectricity-related effects in vertical optoelectronic devices.

Circularly Polarized Luminescence in Zero-Dimensional Antimony Halides: Structural Distortion Controlled Luminescence Thermometer

Materials emitting circularly polarized luminescence (CPL) have been intensively studied for their promising applications in various fields. However, developing tunable and responsive CPL materials in a wide wavelength range remains a great challenge. Here, a pair of chiral (R,R/S,S-DCDA)₃Sb₂Cl₁₂ (DCDA = dimethyl-1,2-cyclohexanediamine divalent cation) shows efficient broadband yellow emission with a photoluminescence (PL) quantum yield of 27.6% with a CPL asymmetry factor of 3 × 10^-3. The associated chiroptical activity is attributed to the efficient chiral transfer as well as the self-trapped exciton emission originating from the large distortion of the inorganic blocks. Notably, (R,R/S,S-DCDA)₃Sb₂Cl₁₂ exhibits a large red-shift emission exceeding 100 nm upon lowering temperature. An excellent linear correlation of the PL wavelength on temperature indicates that the compounds can be used as PL thermometers, which originates from a temperature-dependent linear structural distortion of the [SbCl₆] emitter. This work inspires the potential utilization of CPL-emitting materials as responsive light sources.

Chiral Rashba Ferroelectrics for Circularly Polarized Light Detection

Direct detection of circularly polarized light (CPL) is a challenging task due to limited materials and ambiguous structure-property relationships that lead to low distinguishability of the light helicities. Perovskite ferroelectric semiconductors incorporating chirality provide new opportunities in dealing with this issue. Herein, a pair of 2D chiral perovskite ferroelectrics is reported, which have enhanced CPL detection performance due to interplays among lattice, photon, charge, spin, and orbit. The chirality-transfer-induced chiral&polar ferroelectric phase enhances the asymmetric nature of the photoactive sublattice and achieves a switchable self-powered detection via the bulk photovoltaic effect. The single-crystal-based device exhibits a CPL-sensitive detection performance under 430 nm with an asymmetric factor of 0.20 for left- and right-CPL differentiation, about two times that of the pure chiral counterparts. The enhanced CPL detection performance is ascribed to the Rashba-Dresselhaus effect that originates from the bulk inversion asymmetry and strong spin-orbit coupling, shown with a large Rashba coefficient, which is demonstrated by density functional theory calculation and circularly polarized light excited photoluminescence measurement. These results provide new perspectives on chiral Rashba ferroelectric semiconductors for direct CPL detection and ferroelectrics-based chiroptics and spintronics.

cis/trans-Isomeric Cation Tuning Photoluminescence and Photodetection in 2D Perovskites

Cationic components in the organic-inorganic hybrid perovskites (OIHPs) play an important role in the arrangement and tilting of the inorganic part that is responsible for semiconducting, luminescent, and photoelectronic properties. Herein, we report two 2D OIHP compounds, (cis-4ACHO)₂(H₃OBr)PbBr₄ (1) and (trans-4ACHO)₂(H₃OCl)PbBr₄ (2) (4ACHO = 4-aminocyclohexanol), showing both photoluminescence (PL) and photodetection (PD) that are tuned by the cis- and trans configurational isomerism of 4ACHO. Crystals of 1 and 2 exhibit similar packing structures but with different crystallographic symmetries. Compound 2 displays a broadband white-light emission with a higher PL efficiency (6.6%) than 1 (2.1%) that emits narrowband blue light while the PD property of 1 is better than 2 with a higher on/off ratio under the same conditions. The PL and PD of the two compounds show a seesaw relationship, which provides a new perspective for understanding the PL and PD properties in OIHPs.

Ferroic phase transition molecular crystals

Ferroic phase transition molecular crystals (FPTMCs), i.e., ferroelectrics and ferroelastics, are an important family of functional molecular materials, having merits of easy synthesis, structural tunability and flexibility, and biocompatibility. Both...

Baseline brain function in the preadolescents of the ABCD Study

The Adolescent Brain Cognitive Development (ABCD) Study® is a 10-year longitudinal study of children recruited at ages 9 and 10. A battery of neuroimaging tasks are administered biennially to track neurodevelopment and identify individual differences in brain function. This study reports activation patterns from functional MRI (fMRI) tasks completed at baseline, which were designed to measure cognitive impulse control with a stop signal task (SST; N = 5,547), reward anticipation and receipt with a monetary incentive delay (MID) task (N = 6,657) and working memory and emotion reactivity with an emotional N-back (EN-back) task (N = 6,009). Further, we report the spatial reproducibility of activation patterns by assessing between-group vertex/voxelwise correlations of blood oxygen level-dependent (BOLD) activation. Analyses reveal robust brain activations that are consistent with the published literature, vary across fMRI tasks/contrasts and slightly correlate with individual behavioral performance on the tasks. These results establish the preadolescent brain function baseline, guide interpretation of cross-sectional analyses and will enable the investigation of longitudinal changes during adolescent development.

Distinct Regionalization Patterns of Cortical Morphology are Associated with Cognitive Performance Across Different Domains

Cognitive performance in children is predictive of academic and social outcomes; therefore, understanding neurobiological mechanisms underlying individual differences in cognition during development may be important for improving quality of life. The belief that a single, psychological construct underlies many cognitive processes is pervasive throughout society. However, it is unclear if there is a consistent neural substrate underlying many cognitive processes. Here, we show that a distributed configuration of cortical surface area and apparent thickness, when controlling for global imaging measures, is differentially associated with cognitive performance on different types of tasks in a large sample (N = 10 145) of 9-11-year-old children from the Adolescent Brain and Cognitive DevelopmentSM (ABCD) study. The minimal overlap in these regionalization patterns of association has implications for competing theories about developing intellectual functions. Surprisingly, not controlling for sociodemographic factors increased the similarity between these regionalization patterns. This highlights the importance of understanding the shared variance between sociodemographic factors, cognition and brain structure, particularly with a population-based sample such as ABCD.

A ferroelastic molecular rotor crystal showing inverse temperature symmetry breaking

A molecular rotor crystal shows a ferroelastic phase transition with unique inverse temperature symmetry breaking which is a result of concerted molecular movement triggered by anisotropic steric repulsion among adjacent molecules.

The Impact of the Shallow-Trench Isolation Effect on Flicker Noise of Source Follower MOSFETs in a CMOS Image Sensor

The flicker noise of source follower transistors is the dominant noise source in image sensors. This paper reports a systematic study of the shallow trench isolation effect in transistors with different sizes under high temperature conditions that correspond to the quantity of empty defect sites. The effects of shallow trench isolation sidewall defects on flicker noise characteristics are investigated. In addition, the low-frequency noise and subthreshold swing degrade simultaneously in accordance to the device gate width scaling. Both serious subthreshold leakage and considerable noise can be attributed to the high trap density near the STI edge. Consequently, we propose a coincidental relationship between the noise level and the subthreshold characteristic; its trend is identical to the experiments and simulation results.

Association between the FAS rs2234767G/A polymorphism and cancer risk: a systematic review and meta-analysis

Abnormal regulation of apoptosis can lead to carcinogenesis. Single nucleotide polymorphisms in apoptotic genes have been associated with cancer risk, such as the FAS rs2234767G/A polymorphism, which alters transcription of the FAS promoter. Downregulation of FAS, with resultant cellular resistance to death signals, has been found in many cancers. However, the association between the FAS rs2234767G/A polymorphism and cancer risk is still controversial. Here, we performed a meta-analysis including 41 articles (44 case-control studies, 17,814 cases and 24,307 controls) identified from PubMed and Chinese language (CNKI and WanFang) databases related to cancer susceptibility and the FAS rs2234767G/A polymorphism. We used odds ratios (ORs) and 95% confidence intervals (CIs) to assess the strength of the associations. We found that the rs2234767 G-allele was a protective factor for cancer risk (GG vs. AA: OR=0.88, 95% CI=0.79-0.98; GG+GA vs. AA: OR=0.87, 95% CI=0.79-0.96). Similar associations were detected in the "source of control", ethnicity, and cancer type subgroups. Further studies on a larger sample size and considering gene-environment interactions should be conducted to confirm the role of FAS polymorphisms, especially rs2234767G/A, in cancer risk.

The main effects, epistatic effects and environmental interactions of QTLs on the cooking and eating quality of rice in a doubled-haploid line population

Amylose content (AC), gel consistency (GC) and gelatinazation temperature (GT) are three important traits that influence the cooking and eating quality of rice. The objective of this study was to characterize the genetic components, including main-effect quantitative trait loci (QTLs), epistatic QTLs and QTL-by-environment interactions (QEs), that are involved in the control of these three traits. A population of doubled haploid (DH) lines derived from a cross between two indica varieties Zhenshan 97 and H94 was used, and data were collected from a field experiment conducted in two different environments. A genetic linkage map consisting of 218 simple sequence repeat (SSR) loci was constructed, and QTL analysis performed using QTLMAPPER 1.6: resolved the genetic components into main-effect QTLs, epistatic QTLs and QEs. The analysis detected a total of 12 main-effect QTLs for the three traits, with a QTL corresponding to the Wx locus showing a major effect on AC and GC, and a QTL corresponding to the Alk locus having a major effect on GT. Ten digenic interactions involving 19 loci were detected for the three traits, and six main-effect QTLs and two pairs of epistatic QTLs were involved in QEs. While the main-effect QTLs, especially the ones corresponding to known major loci, apparently played predominant roles in the genetic basis of the traits, under certain conditions epistatic effects and QEs also played important roles in controlling the traits. The implications of the findings for rice quality improvement are discussed.

Migration in a socialist transitional economy: heterogeneity, socioeconomic and spatial characteristics of migrants in China and Guangdong province

The peculiar features of China's socialist transitional economy, including the coexistence of "plan" and "nonplan" mechanisms, the hukou institution, uneven spatial development, and gendered constraints and opportunities, have brought about a high degree of heterogeneity among population movements. Using the 1990 Census data on reasons for migration, and an empirical analysis of both national patterns and migration in Guangdong, the author documents the socioeconomic characteristics and spatial patterns of major types of migration, focusing on migration for employment in industry and business, male migration due to job transfer, and female marriage migration. The author argues that the multitude of migration types, and the contrasts among them, are products of the combination of state-planning and market mechanisms. The findings highlight institutional explanations for migration, and show that the "plan"/"nonplan" dichotomy is more meaningful that the economic-social dichotomy for understanding population movements in China.

A statistical approach to estimate O3 uptake of ponderosa pine in a mediterranean climate

In highly polluted sites, stomatal behavior is sluggish with respect to light, vapor pressure deficit, and internal CO2 concentration (Ci) and poorly described by existing models. Statistical models were developed to estimate stomatal conductance (gs) of 40-year-old ponderosa pine at three sites differing in pollutant exposure for the purpose of calculating O3 uptake. Gs was estimated using julian day, hour of day, pre-dawn xylem potential and photosynthetic photon flux density (PPFD). The median difference between estimated and observed field gs did not exceed 10 mmol H2O m(-2) s(-1), and estimated gs within 95% confidence intervals. 03 uptake was calculated from hourly estimated gs, hourly O3 concentration, and a constant to correct for the difference in diffusivity between water vapor and 03. The simulation model TREGRO was also used to calculate the cumulative 03 uptake at all three sites. 03 uptake estimated by the statistical model was higher than that simulated by TREGRO because gas exchange rates were proportionally higher. O3 exposure and uptake were significantly correlated (r2>0.92), because O3 exposure and gs were highly correlated in both statistical and simulation models.

Cloning and characterization of hMAP126, a new member of mitotic spindle-associated proteins

One novel gene product, hMAP126, was demonstrated to interact with p29 in the yeast two-hybrid assay. The full-length cDNA of hMAP126 has been obtained and encodes a protein of 1120 amino acids. Multiple tissue Northern blot analysis showed that hMAP126 was abundantly expressed in the testis. Polyclonal antiserum against hMAP126 was raised and affinity-purification of anti-hMAP126 antibodies was performed. The subcellular distribution of hMAP126 was localized to the mitotic spindle. Furthermore, hMAP126 was identified to be post-translationally modified and phosphorylated by p34(cdc2) kinase in vitro. Taken together, we have isolated a novel protein, hMAP126, which may be involved in the functional and dynamic regulation of mitotic spindles.

[Identification of synthetic adhesives by simultaneous pyrolysis methylation gas chromatography]

At present, pyrolysis gas chromatography (Py-GC) is an effective analytical method for trace synthetic adhesives. Synthetic adhesives are usually composed of polar components. Thus, the polar pyrolysis products are normally difficult to measure by Py-GC due to their partial or complete adsorption in the pyrolysis zone, injection system or capillary column and the accuracy of results is seriously affected. Simultaneous pyrolysis methylation gas chromatography (Py-Me-GC) is a fast analytical method which was developed in recent years for polar compounds. The five synthetic adhesives have been identified by using Py-Me-GC in our study. Analytical conditions were: filament pyrolysis apparatus, flame ionization detector (FID), gas chromatograph, FFAP capillary column (30 m x 0.25 mm i.d.) and a quaternary ammonium salt as methylating agent. Major peaks of the products of pyrolysis were analysed qualitatively by GC/MS and comparisons were also made between the results by Py-Me-GC and those by Py-GC. The information gained from the components of substances by Py-Me-GC is more than that by Py-GC. The method is suitable for identifying synthetic adhesives of trace evidence in forensic science.

Age estimation using a modified HPLC determination of ratio of aspartic acid in dentin

Diastereomeric dipeptides were derived from the amino acid enantiomers in dentin by O-phthalaldehyde-N-acetyl-L-cysteine. The products were separated using high performance liquid chromatography (HPLC) and detected by fluorescence detector. A short analysis time (total analysis time was 15 min, including retention time, sample derivatization time and column regeneration time) was used. The sensitivity of detection was 1 pmol and high resolution (Rs = 1.5) was reached. We determined the D/L ratio of aspartic acid in dentin of 28 first premolars. The correlation value between the D/L ratio of aspartic acid and actual age was 0.9887; errors of +/- 1 year accounted for 46.4%, and no error exceeded 5 years.

Isolated myocardial abscess causing coronary artery rupture and fatal hemopericardium

We report a rare case of cardiac tamponade caused by hemopericardium secondary to erosion and rupture of a coronary artery by an adjacent solitary myocardial abscess. The resulting tamponade led to the sudden death of this 46-year-old man. Antemortem blood culture and the postmortem microscopic examination of the myocardial abscess revealed the causative agent to be Staphylococcus aureus. Hemopericardium due to ventricular wall rupture secondary to a myocardial abscess has been infrequently reported, but, to our knowledge, only one other report of hemopericardium due to coronary artery rupture related to myocardial abscess has been published.

Mixed pulmonary blastoma and carcinosarcoma

Pulmonary blastomas and carcinosarcomas are uncommon tumours, accounting for less than 1% of all lung neoplasms. Three previously described mixed epithelial and mesenchymal tumours having both adult and embryonal elements were termed 'transitional'. We report a similar case and evaluate the application of the term 'transitional tumour'.

The temporal and spatial dynamics of income and population growth in Ohio, 1950-1990

"This paper focuses on spatial variation of growth within a state. Using Ohio as a case study, two hypotheses are extracted from the literature. First, the theories of polarization and polarization reversal suggest that in the old industrial core the leading sector role of manufacturing has diminished in old manufacturing poles, and that income growth trends differ substantially between these old poles and new centres of development. Second, the theories of suburbanization and migration reversals suggest that population growth is contingent upon level of urbanization, and that the relationship has changed drastically between the pre-1970s, 1970s, and post-1970s periods." (SUMMARY IN FRE AND GER)

Polyamines mediate androgenic stimulation of calcium fluxes and membrane transport in rat heart myocytes

The androgenic steroid hormone testosterone induced an early (less than 30-60 seconds) stimulation of endocytosis, hexose transport, and amino acid transport, monitored by the temperature-sensitive uptake of horseradish peroxidase, 2-deoxyglucose, and alpha-aminoisobutyrate, respectively, in rat ventricle cubes and acutely isolated ventricular myocytes. This stimulation was time- and concentration-dependent and was maximal at 10(-9) to 10(-8) M testosterone, consistent with androgen-receptor mediation. EGTA (2.5 mM), La3+ (1 mM), and verapamil (100 microM) ablated the hormonal response. The calcium ionophore A23187 (10 microM) induced an acute stimulation of endocytosis, amino acid transport, and hexose transport which was not further increased by testosterone (10(-8) M), suggesting a common effector pathway. Testosterone (10(-8) M) also evoked a rapid (less than 30 seconds) stimulation of 45Ca influx and efflux. Testosterone (10(-8) M) induced a rapid (less than 5 seconds) transient increase in ornithine decarboxylase (ODC) activity peaking (twofold to threefold) at 60 seconds, and an early (15 seconds) transient accumulation of polyamines peaking at 60 seconds in isolated myocytes. The specific, irreversible ODC inhibitor alpha-difluoromethylornithine (DFMO, 5-10 mM) blocked the testosterone-evoked increase in ODC activity and polyamine levels and the stimulation of Ca2+ fluxes, endocytosis, hexose transport, and amino acid transport. Putrescine (0.5-1 mM), the ODC product, reversed DFMO inhibition and restored the increase in polyamines, 45Ca fluxes, and Ca2+-dependent membrane transport processes. These results demonstrate that rapid, transient ODC-regulated polyamine synthesis is essential for androgenic stimulation of Ca2+ fluxes and membrane transport processes in ventricular myocytes. These findings support a model for signal transduction in which newly synthesized polyamines serve as intracellular messengers to regulate transmembrane Ca2+ movements, Ca2+-dependent membrane transport functions, and other Ca2+- and polyamine-sensitive processes in cardiac myocytes.

The role of polyamines in beta-adrenergic stimulation of calcium influx and membrane transport in rat heart

The beta-adrenergic agonist 1-isoproterenol induced an early (less than 1 min) stimulation of endocytosis, amino acid transport and hexose transport, monitored by the temperature-sensitive uptake of horseradish peroxidase, alpha-aminoisobutyrate and 2-deoxyglucose, respectively, in rat ventricle cubes. This stimulation was time- and concentration-dependent and was maximum at 10(-8) M isoproterenol. The beta-adrenergic antagonist propranolol blocked isoproterenol stimulation of membrane transport, thereby confirming beta-adrenoceptor mediation; 2.5 mM EGTA, 1 mM LaCl2 and 100 microM verapamil blocked the hormonal response without affecting basal transport. The calcium ionophore A23187 caused an acute stimulation of endocytosis, hexose and amino acid transport. Isoproterenol rapidly (less than 30 s) stimulated 45Ca2+ influx. These data suggest that stimulus-response (stimulus-"transport") coupling is mediated by a rise in cytosolic Ca2+ concentration. A rapid (less than 30 to 60 s) increase in ornithine decarboxylase (ODC) activity, followed by an early (less than 1 to 2 min), sustained increase in putrescine, spermidine and spermine concentrations was evoked by 10(-7) M isoproterenol. The ODC inhibitor alpha-difluoromethylornithine (DFMO, 5 mM) suppressed the isoproterenol-induced increase in ODC and polyamine levels and the stimulation of 45Ca influx, endocytosis, hexose transport, and amino acid transport. Putrescine (0.5 mM) negated DFMO inhibition and restored the increase in polyamines, 45Ca influx, endocytosis, and transport of hexose and amino acid. These data suggest that polyamine synthesis is involved in isoproterenol stimulation of Ca2+ influx and membrane transport functions in ventricular myocardium. These findings are consistent with a model for signal transduction and stimulus-response coupling in which polyamines function as intracellular messengers to generate cytosolic Ca2+ signals by stimulating Ca2+ influx.

Calcium/calmodulin inhibition of coupled NaCl transport in membrane vesicles from rabbit ileal brush border

The role of Ca2+ and calmodulin in regulating coupled NaCl transport has been investigated in membrane vesicles from rabbit ileal brush border. Uptake of 22Na+ and 36Cl- was determined by a rapid filtration technique in vesicles isolated with a sucrose density gradient ultracentrifugation method. Ca2+ on the inside of the vesicle inhibited Na+ uptake when Cl- was the anion and Cl- uptake when Na+ was the cation by approximately equal to 30%. Ca2+ on the outside had no effect. When gluconate was the anion or when choline was the cation, Na+ or Cl- uptake was reduced by only 9-12%. A similar inhibition of D-[3H]mannitol uptake (10-17%) suggests this was due to a nonspecific decrease in the membrane permeability. Other cations such as Ba2+ and Mg2+ had no effect, but La3+ inhibited Na+ and Cl- uptake to the same degree as Ca2+. Calmodulin (2 microM) in combination with Ca2+ (1 microM, free concentration) significantly inhibited Na+ uptake when Cl- was the anion by 21-32% and Cl- uptake when Na+ was the cation by 20-27%. This effect was completely reversed by 10 microM trifluoperazine. When gluconate was the anion or when choline was the cation, Na+ or Cl- uptake was unaffected by Ca2+/calmodulin and trifluoperazine. The Ki for Ca2+ inhibition of Cl- -coupled Na+ uptake was reduced from 200 microM to 0.2 microM by incubation with 20 microM calmodulin. The Ki for exogenously added calmodulin studied at 1 microM Ca2+ was 0.2 microM. The Ki for trifluoperazine inhibition of the Ca2+/calmodulin response was 3 microM. These results represent compelling evidence for intracellular Ca2+/calmodulin regulation of coupled NaCl transport across the intestinal microvillus membrane. The exact mechanism of this regulation remains to be delineated.

Coupled sodium-chloride transport by rabbit ileal brush-border membrane vesicles

Uptake of Na and Cl into brush-border membrane vesicles isolated from rabbit ileal epithelial cells was investigated with a rapid filtration technique using 22Na and 36Cl as tracers. The rank order of anion dependence for Na uptake in the absence of anion gradients was SCN greater than NO3 greater than gluconate. The sequence of cation specificity for Cl uptake was Na congruent to Li greater than K greater than choline. The transport of Na and Cl were both inhibited by harmaline, furosemide, 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid, and 4,4'-diisothiocyano-2,2'-stilbene disulfonic acid. Carrier mediation of Cl-stimulated Na transport was suggested by the competition for 22Na uptake with increasing concentrations of unlabeled Na in the presence of Cl but not when gluconate was the counterion. Chloride-dependent Na uptake had an apparent Km of 4.5 mM and a Vmax of 20 nmol . mg prot-1 . 15 s-1. Na-H exchange and Cl-OH (or HCO3) exchange were also demonstrated in these vesicles. These findings confirm the presence of an electrically neutral carrier-mediated, Na-Cl-coupled transport process in the apical cell membrane of rabbit ileal epithelial cells. The nature of the coupling of Na to Cl transport, i.e., NaCl symport or a process that combines Na-H antiport with Cl-OH (or HCO3) antiport, remains to be determined.

Effect of phenolphthalein on monkey intestinal water and electrolyte transport

To assess Na-K-ATPase inhibiton and prostaglandin synthesis stimulation as the mechanism of the secretory (cathartic) action of phenolphthalein in the primate, we investigated water and electrolyte transport and Na-K-ATPase levels in monkey intestine. Both jejunum and colon were studied with in vivo perfusion and in vitro Ussing chamber techniques. Water, Na, and Cl absorption was inhibited or secretion was induced by phenolphthalein (10(-3) M) in the jejunum and colon when the drug was present in the mucosal bathing (perfusion) solution. Serosal addition of phenolphthalein (10(-4) or 10(-3) M) induced Na and anion absorption in the jejunum but not in the colon. Phenolphthalein inhibited Na-K-ATPase activity in the test tube, but assays of intestine previously perfused or bathed in the drug showed no inhibiton. Indomethacin, in doses sufficient to inhibit prostaglandin synthesis in the intestine, inhibited the secretion induced by phenolphthalein in the jejunum but not in the colon. These inconsistencies cast doubt on the role of Na-K-ATPase inhibition or the role of prostaglandin synthesis stimulation in the mechanism of action of phenolphthalein.

Response of white adipocyte of mouse and rabbit to catecholamines and ACTH. 2. Stability and restoration of activity of hormone-sensitive adenylate cyclase of adipocyte plasma membrane

The isolated intact white adipocyte of the Swiss mouse responds to both ACTH and catecholamines by an elevation of cAMP levels and an increase in lipolysis. However, in the isolated plasma membrane of the mouse adipocyte, adenylate cyclase loses its responsiveness to ACTH but retains its ability to respond to catecholamines. This lack of responsiveness to ACTH by adenylate cyclase of mouse adipocyte plasma membrane can be overcome, at least partially, by addition of GPP (NH)p, an analog of GTP, to the assay medium. The data on mouse adipocyte membrane suggests that the coupling of ACTH receptor to adenylate cyclase is dependent on GTP and that catecholamine-activation of adenylate cyclase is less dependent on this nucleotide. The isolated intact white adipocyte of adult New Zealand rabbit responds to ACTH, but does not (or only weakly) respond to catecholamines. In contrast to the mouse plasma membrane preparation, adenylate cyclase of adipocyte membrane of the rabbit responds to ACTH. And the addition of GPP(NH)P is not required to demonstrate the CTH: sensitive adenylate cyclase activity. The difference between mouse and rabbit adipocyte membrane in the requirement for GPP(NH)P in ACTH action is not readily explained. The lack of catecholamine sensitivity of rabbit membrane enzyme cannot be reversed by addition of GPP(NH)P or adenosine deaminase. These two adenylate cyclase model systems using mouse and rabbit adipocyte plasma membrane may be useful tools for the study of the specificity and mechanism of action of lipolytic hormones such as ACTH and catecholamines.

Response of white adipocyte of mouse and rabbit to catecholamines and ACTH. 3. Modified binding properties of beta-adrenoreceptor and its decreased coupling efficiency for adenylate cyclase

Using (-)-[3H]-dihydroalprenolol ([3H]-DHA) and [3H]-norepinephrine ([3H]-NE) as probes, adrenoreceptors in mouse and rabbit adipocyte plasma membranes were studied and compared. The binding of either radioligand can be displaced by propranolol, alprenolol, isoproterenol or norepinephrine. [3H]-Norepinephrine bound to rabbit plasma membrane can be displaced by phentolamine. Based on displacement of radioligand by unlabelled stereoisomers, the binding is stereospecific for the (-) stereoisomer. Quantitative binding determinations of catecholamine radioligand as well as competitive inhibitory and displacement studies with Scatchard plots where appropriate, allowed calculation of binding parameters including Bmax and Kd for both radioligands and for the compounds listed above. Kinetics of displacement were also followed. Based on these binding parameters and kinetics, together with the activity of hormone and NaF sensitive adenylate cyclase, we conclude that both the population of beta-adrenoreceptor and its coupling efficiency for adenylate cyclase of the rabbit plasma membrane appear to be low as compared to that of mouse and rat.

Response of white adipocyte of mouse and rabbit to catecholamines and ACTH. 1. Correlation of cyclic AMP levels and initial rates of lipolysis

Hormone stimulated lipolysis of mouse and rabbit adipocytes as measured by both free fatty acid and glycerol release, is proportionally elevated with increase in the adipocyte cAMP level up to 1 nmol/g. The correlation coefficients are 0.94 and 0.97 for FFA/cAMP and glycerol/cAMP respectively. Increments in cAMP greater than 1 nmol/g show no correlation with increase in lipolysis. The release of lipolytic products, glycerol and free fatty acids, from white adipocytes in response to ACTH, epinephrine or norepinephrine was measured using radiochemical assays in short term incubation systems, with cAMP levels measured at the same time and from the same cell sample. Under the conditions studied, epinephrine is a more effective lipolytic hormone than ACTh in mouse adipocyte, and ACTH is more effective than epinephrine in rabbit adipocyte. The effect of catecholamines on the rabbit adipocyte is not modified by phentolamine (10 microM), but it is potentiated by 1-methyl-3-isobutyl xanthine (0.1 mM). The results suggest that cAMP mediates the action of these lipolytic hormones in white adipocytes of mouse and rabbit.

Activity of free and carrier-bound methotrexate against transport-deficient and high dihydrofolate dehydrogenase-containing methotrexate-resistant L1210 cells

A difference in the mechanism of transmembrane transport was demonstrated for methotrexate (MTX) and MTX bound to the high molecular weight carrier bovine serum albumin (MTX-BSA) when the drug dose needed to reduce growth of cells to 50% of that of untreated cells (ID50) was compared in the sensitive L1210 leukemia and 3 L1210 sublines resistant to MTX by virtue of either deficient MTX transport or high levels of dihydrofolate dehydrogenase (DHFD). The loss of transport increased the ID50 for inhibition of growth rate by free MTX tenfold to twentyfold, whereas the elevation of DHFD levels increased the ID50 by tenfold. In contrast, deficiency of transport resulted in only a twofold increase in the ID50 for MTX-BSA, and elevation of DHFD caused a tenfold increase similar to that for free MTX. This difference was confirmed in studies of inhibition of DHFD activity by free and BSA-bound MTX. MTX-BSA but not MTX had antitumor activity against the transport-deficient L1210 line in (C57BL/6 x DBA/2)F1. These studies confirm a separate mode of cell entry for MTX-BSA and suggest a role for these complexes in overcoming resistance.

Fluorimetric and spectrophotometric studies of DPN-linked isocitrate dehydrogenase from bovine heart. Properties of tyrosyl and tryptophyl residues

The emission maximum of DPN-linked isocitrate dehydrogenase in pH 7.07 buffer is shifted from 317 to 324 nm and fluorescence intensity is decreased when the excitation wave-length is varied from 270 to 290 nm; in 0.2 M KOH, where the fluorescence of tyrosyl residues is almost completely quenched, a further substantial decline in quantum yield of protein fluorescence and a red shift of the emission peak to 339 nm occur. The latter should be due mainly to tryptophyl residues. The enzyme contains 9.4 tyrosyl residues per subunit of molecular weight 42,000 determined spectrophotometrically (295 nm) at pH 13, in good agreement with a tyrosine content of 9.7 by amino acid analysis. No more than 1.1 tyrosyl residues per subunit can be detected up to pH 10.6 at 7 degrees upon prolonged incubation. The increase in absorption at 295 nm with increasing pH is related to loss of enzyme activity and results in a red shift of the emission maximum, and decreased fluorescence intensity. Treatment of the enzyme in a Li+-containing buffer at pH 7.5 with an excess of N-acetylimidazole results in (a) modification of 1.1 tyrosyl residues per subunit, (b) a 30% decrease in enzyme activity, (c) a 6-nm red shift in emission maximum, and (d) a decrease in fluorescence intensity. Manganous DL-isocitrate (1.06 mM) prevents the acetylation of the enzyme. Deacetylation of the O-acetylated enzyme by hydroxylamine completely restores the enzyme activity and reverses the spectral changes. The acetylation studies indicate that the reactive tyrosyl residue does not participate directly in catalysis but may be involved in maintaining the proper conformation of the active enzyme center. A net of 1 of the 2 tryptophyl residues per subunit is perturbed immediately by a number of solvents. This perturbation is not affected by manganous isocitrate, whereas exposure of tyrosyl residues occurs only with time and is prevented by the substrate. The perturbation of the tryptophyl residue is accompanied by a red shift of the fluorescence emission maximum. The more exposed tryptophyl residue may contribute to the energy transfer from protein to nucleotides since the quenching of protein fluorescence upon binding of DPN+, DPNH, or ADP by enzyme results in a blue shift of the emission maximum. Manganous DL-isocitrate (1.06 mM) quenches protein fluorescence by 16% without a shift in emission peak and does not affect the relative extent of fluorescence quenching induced by the nucleotides.

Effects of temperature on diphosphopyridine nucleotide-linked isocitrate dehydrogenase from bovine heart. Aspects of the kinetics, stability, and quarternary structure of the enzyme

A temperature-dependent conformational change of the active DPN-linked isocitrate dehydrogenase was observed. When initial reaction kinetic data were examined between 35 and 5 degrees, the Hill number (n) varied from 2 at higher to n approaching unity at lower temperatures, with an inflection point at 17 degrees. The presence of manganous isocitrate in the incubation media shifted the transition temperature for enzyme inactivation by 5,5'-dithiobis(2-nitrobenzoate) from 8-16 degrees. These temperature-dependent transitions were paralleled by progressive changes in sedimentation velocities from s20, w of 10.4 at 25 degrees to 7.3 at 10 degrees as measured by active band centrifugation. The linear Arrhenius plot for apparent V max and the constancy of S0.5 for the substrate manganous isocitrate between 35 and 5 degrees suggest that this temperature-dependent conformational change may not be solely related to manganous isocitrate. Further indications of equilibria between different species of enzyme in solution and effects of substrates and cofactors on conformation came from studies of specific activity of enzyme diluted into buffers at 3 and 25 degrees. Dilution to concentrations between 10 and 25 mum enzyme resulted in relatively rapid protein concentration-dependent inactivation which could be prevented and fully reversed by manganous isocitrate. No further substantial inactivation was found subsequent to this phase at 25 degrees. Lowering the temperature of the dilution buffer to 3 degrees favored formation of enzyme species exhibiting a further time and pH-dependent loss of activity which became independent of protein concentration below 7 mum enzyme. The rate of cold inactivation was reduced by raising the ionic strength of the buffer and its progress could be arrested by manganous isocitrate; however, the substrate did not restore the original activity.