Kinetic quantification of protein polymer nanoparticles using non-invasive imaging

Protein polymers are repetitive amino acid sequences that can assemble monodisperse nanoparticles with potential applications as cancer nanomedicines. Of the currently available molecular imaging methods, positron emission tomography (PET) is the most sensitive and quantitative; therefore, this work explores microPET imaging to track protein polymer nanoparticles over several days. To achieve reliable imaging, the polypeptides were modified by site-specific conjugation using a heterobifunctional sarcophagine chelator, AmBaSar, which was subsequently complexed with (64)Cu. AmBaSar/(64)Cu was selected because it can label particles in vivo over periods of days, which is consistent with the timescales required to follow long-circulating nanotherapeutics. Using an orthotopic model of breast cancer, we observed four elastin-like polypeptides (ELPs)-based protein polymers of varying molecular weight, amino acid sequence, and nanostructure. To analyze this data, we developed a six-compartment image-driven pharmacokinetic model capable of describing their distribution within individual subjects. Surprisingly, the assembly of an ELP block copolymer (78 kD) into nanoparticles (R(h) = 37.5 nm) minimally influences pharmacokinetics or tumor accumulation compared to a free ELP of similar length (74 kD). Instead, ELP molecular weight is the most important factor controlling the fate of these polymers, whereby long ELPs (74 kD) have a heart activity half-life of 8.7 hours and short ELPs (37 kD) have a half-life of 2.1 hours. These results suggest that ELP-based protein polymers may be a viable platform for the development of multifunctional therapeutic nanoparticles that can be imaged using clinical PET scanners.

Effect of Hot Water and Water-carrying Agent on the Properties of Silane-water Crosslinked Linear Low Density Polyethylene

The influence of hot water and the water-carrying agent aluminum potassium sulfate dodecahydrate (alum) on the mechanical and thermal properties of the silane-water crosslinked linear low density polyethylene (LLDPE) was investigated. LLDPE was melt-grafted with various content of vinyl trimethoxysilane (VTMS) using dicumyl peroxide (DCP) as initiator. The results show that the contribution of hot water to gel content is poor, about 2 to 16%, compared with that of the silane grafted LLDPE. Is feasible to achieve silane-water crosslinking reaction with alum for self-crosslinked LLDPE; furthermore, the self-crosslinked LLDPE has lower crosslink density (ν). It was found that alum could not only conduct silane-water crosslinking reaction effectively, but also improve the mechanical properties, especially the elongation behavior. The heat of fusion (ΔHm), the melting temperature (Tm), and the degree of crystallinity (Xc) of the hot water crosslinked LLDPE decreased with the advancement of VTMS. The Avrami exponent n of self-crosslinked sample was larger than that of hot water crosslinked sample. This means that the alum could contribute to the growth of crystallization.

Comparison of morphological and molecular genetic quantification of relative abundance of arbuscular mycorrhizal fungi within roots

Nested PCR amplicons of ribosomal RNA genes have been used to identify individuals within assemblages of arbuscular mycorrhizal (AM) fungi in roots and to estimate their relative abundance. Microscopy has also been used to identify their relative abundance in roots, but only at low resolution, usually the genus level. We evaluated the robustness of using nested PCR amplicons of ribosomal RNA genes to estimate the relative abundance of undefined AM fungi in uniformly aged roots in comparison to visual estimates. The relative abundance of AM fungi was assessed as per cent root length colonised by morphotypes and relative sequence type abundance in clone libraries. Plants were grown in coastal soil to obtain assemblages of unknown AM fungi at two times (spring and autumn). Relative abundance of dominant genera of AM fungi in roots (Archaeospora and Glomus) based on an analysis of ribosomal RNA genes did not consistently correspond with relative abundance of morphotypes. This microscopic vs. molecular genetic comparison supports previous conclusions that there can be limitations in using nested PCR amplicons for quantifying the relative abundance of AM fungi in roots, with a sampling bias likely to be of significance. Both molecular genetic and morphological methods are used to estimate relative abundance of AM fungi as a precursor to understanding mycorrhizal function in field soils, but they are rarely verified using alternative approaches although this may be necessary.

An effect comparison between Furlow double opposing Z-plasty and two-flap palatoplasty on velopharyngeal closure

The aim of this study was to compare velopharyngeal closure between patients who underwent Furlow palatoplasty and two-flap palatoplasty. A retrospective review of 88 patients with incomplete palate cleft was performed. 48 patients (17 males; 31 females) aged 2-28 years received Furlow palatoplasty. 40 patients (17 males; 23 females) aged 2-21 years received two-flap palatoplasty. Velopharyngeal function was categorized as adequate, marginal or inadequate. Complications associated with the operation were documented. Statistically significant differences were not found amongst sex distribution, age at operation, follow-up time, and preoperative speech intelligibility. After primary repairs using Furlow and two-flap palatoplasty, the surgeon's incidence of postoperative palatal fistula was 0%. The complications were not significantly different between the two groups. The authors achieved the lowest reported incidence of postoperative palatal fistulas in primary Furlow palatoplasty. The outcomes of the velopharyngeal closure were better in patients who received Furlow palatoplasty (P<0.05). Furlow palatoplasty was more effective than two-flap palatoplasty in obtaining perfect velopharyngeal closure. A probable explanation may be that Furlow palatoplasty can reposition and overlap the divergent palatal muscle and lengthen the soft palate.

Inter-model consistency and complementarity: learning from ex-vivo imaging and electrophysiological data towards an integrated understanding of cardiac physiology

Computational models of the heart at various scales and levels of complexity have been independently developed, parameterised and validated using a wide range of experimental data for over four decades. However, despite remarkable progress, the lack of coordinated efforts to compare and combine these computational models has limited their impact on the numerous open questions in cardiac physiology. To address this issue, a comprehensive dataset has previously been made available to the community that contains the cardiac anatomy and fibre orientations from magnetic resonance imaging as well as epicardial transmembrane potentials from optical mapping measured on a perfused ex-vivo porcine heart. This data was used to develop and customize four models of cardiac electrophysiology with different level of details, including a personalized fast conduction Purkinje system, a maximum a posteriori estimation of the 3D distribution of transmembrane potential, the personalization of a simplified reaction-diffusion model, and a detailed biophysical model with generic conduction parameters. This study proposes the integration of these four models into a single modelling and simulation pipeline, after analyzing their common features and discrepancies. The proposed integrated pipeline demonstrates an increase prediction power of depolarization isochrones in different pacing conditions.

High-resolution extracellular stimulation of dispersed hippocampal culture with high-density CMOS multielectrode array based on non-Faradaic electrodes

We introduce a method to electrically stimulate individual neurons at single-cell resolution in arbitrary spatiotemporal patterns with precise control over stimulation thresholds. By exploiting a custom microelectronic chip, up to 65,000 non-Faradaic electrodes can be uniquely addressed with electrode density exceeding 6500 electrodes mm(-2). We demonstrate extracellular stimulation of dispersed primary hippocampal neuronal cultures using the chip at single-cell resolution.

A robust state-space kinetics-guided framework for dynamic PET image reconstruction

Dynamic PET image reconstruction is a challenging issue due to the low SNR and the large quantity of spatio-temporal data. We propose a robust state-space image reconstruction (SSIR) framework for activity reconstruction in dynamic PET. Unlike statistically-based frame-by-frame methods, tracer kinetic modeling is incorporated to provide physiological guidance for the reconstruction, harnessing the temporal information of the dynamic data. Dynamic reconstruction is formulated in a state-space representation, where a compartmental model describes the kinetic processes in a continuous-time system equation, and the imaging data are expressed in a discrete measurement equation. Tracer activity concentrations are treated as the state variables, and are estimated from the dynamic data. Sampled-data H(∞) filtering is adopted for robust estimation. H(∞) filtering makes no assumptions on the system and measurement statistics, and guarantees bounded estimation error for finite-energy disturbances, leading to robust performance for dynamic data with low SNR and/or errors. This alternative reconstruction approach could help us to deal with unpredictable situations in imaging (e.g. data corruption from failed detector blocks) or inaccurate noise models. Experiments on synthetic phantom and patient PET data are performed to demonstrate feasibility of the SSIR framework, and to explore its potential advantages over frame-by-frame statistical reconstruction approaches.

Efficacy of 3,5-dibromo-L-phenylalanine in rat models of stroke, seizures and sensorimotor gating deficit

BACKGROUND AND PURPOSE

Abnormal glutamatergic activity is implicated in neurologic and neuropsychiatric disorders. Selective glutamate receptor antagonists were highly effective in animal models of stroke and seizures but failed in further clinical development because of serious side effects, including an almost complete set of symptoms of schizophrenia. Therefore, the novel polyvalent glutamatergic agent 3,5-dibromo-L-phenylalanine (3,5-DBr-L-Phe) was studied in rat models of stroke, seizures and sensorimotor gating deficit.

EXPERIMENTAL APPROACH

3,5-DBr-L-Phe was administered intraperitoneally as three boluses after intracerebral injection of endothelin-1 (ET-1) adjacent to the middle cerebral artery to cause brain injury (a model of stroke). 3,5-DBr-L-Phe was also given as a single bolus prior to pentylenetetrazole (PTZ) injection to induce seizures or prior to the administration of the N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (MK-801) to cause disruption of prepulse inhibition (PPI) of startle (sensorimotor gating deficit).

KEY RESULTS

Brain damage caused by ET-1 was reduced by 52%, which is comparable with the effects of MK-801 in this model as reported by others. 3,5-DBr-L-Phe significantly reduced seizures induced by PTZ without the significant effects on arterial blood pressure and heart rate normally caused by NMDA antagonists. 3,5-DBr-L-Phe prevented the disruption of PPI measured 3 days after the administration of ET-1. 3,5-DBr-L-Phe also eliminated sensorimotor gating deficit caused by MK-801.

CONCLUSION AND IMPLICATIONS

The pharmacological profile of 3,5-DBr-L-Phe might be beneficial not only for developing a therapy for the neurological and cognitive symptoms of stroke and seizures but also for some neuropsychiatric disorders.

Insight into the dicrotic notch in photoplethysmographic pulses from the finger tip of young adults

This study aims to investigate arterial stiffness in selected young adults by non-invasively determining the characteristics of the photoplethysmographic dicrotic notch. A total of 15 volunteers participated in this study, divided into four groups by age and gender. Contour analysis was applied to analyse the photoplethysmographic dicrotic notch, including time-related and height-related parameters. The height of reflected wave, mirrored by the notch relative amplitude (NRA), was found to be significantly larger in the older group compared to the younger group (p = 0.016). The timing of the reflected wave, measured by three parameters, i.e. notch index (NI), notch latency (NL) and peak-to-notch latency (PTNL), significantly increased in the female group compared to the male group (all p < 0.02). The results confirm that arterial stiffness occurs in young adults, and demonstrate that a difference of arterial stiffness exists between young male and female. This study indicates that examining the characteristic notch of the PPG pulse could help in identifying differences of vascular activities.

Delirium accelerates cognitive decline in Alzheimer disease

OBJECTIVE

To examine the impact of delirium on the trajectory of cognitive function in a cohort of patients with Alzheimer disease (AD).

METHODS

A secondary analysis of data collected from a large prospective cohort, the Massachusetts Alzheimer's Disease Research Center's patient registry, examined cognitive performance over time in patients who developed (n = 72) or did not develop (n = 336) delirium during the course of their illnesses. Cognitive performance was measured by change in score on the Information-Memory-Concentration (IMC) subtest of the Blessed Dementia Rating Scale. Delirium was identified using a previously validated chart review method. Using linear mixed regression models, rates of cognitive change were calculated, controlling for age, sex, education, comorbid medical diagnoses, family history of dementia, dementia severity score, and duration of symptoms before diagnosis.

RESULTS

A significant acceleration in the slope of cognitive decline occurs following an episode of delirium. Among patients who developed delirium, the average decline at baseline for performance on the IMC was 2.5 points per year, but after an episode of delirium there was further decline to an average of 4.9 points per year (p = 0.001). Across groups, the rate of change in IMC score occurred about three times faster in those who had delirium compared to those who did not.

CONCLUSIONS

Delirium can accelerate the trajectory of cognitive decline in patients with Alzheimer disease (AD). The information from this study provides the foundation for future randomized intervention studies to determine whether prevention of delirium might ameliorate or delay cognitive decline in patients with AD.

Extraordinary diversity of chemosensory receptor gene repertoires among vertebrates

Chemosensation (smell and taste) is important to the survival and reproduction of vertebrates and is mediated by specific bindings of odorants, pheromones, and tastants by chemoreceptors that are encoded by several large gene families. This review summarizes recent comparative genomic and evolutionary studies of vertebrate chemoreceptor genes. It focuses on the remarkable diversity of chemoreceptor gene repertoires in terms of gene number and gene sequence across vertebrates and the evolutionary mechanisms that are responsible for generating this diversity. We argue that the great among-species variation of chemoreceptor gene repertoires is a result of adaptations of individual species to their environments and diets.

Lipid-rich carcinoma of the breast: a case report

Lipid-rich carcinoma is a rare variant and accounts for < or = 2% of all breast cancer diagnoses. We report a case occurring in a 53-year-old female. The patient presented with a painless, right breast mass. Clinical examination and mammography suggested malignancy. Subsequent modified radical mastectomy revealed the diagnosis of lipid-rich carcinoma. The morphological features, differential diagnosis and treatment along with a brief review of the literature are discussed in this article. Lipid-rich carcinoma (L-RC) is a very rare variant of breast carcinomas with an aggressive clinical course and poor prognosis. It presents only 1% to 2% of all breast cases. It is classified as a specific variety of mammary carcinoma because the tumour cells possess abundant vacuolated cytoplasm which is strongly positive when stained for neutral fat. Aboumrad first described it in 1963 as lipid-secreting carcinoma. However, Ramos and Taylor renamed it as lipid-rich breast carcinoma. In China, the first case was reported in 1984. Herein, we report a case of lipid-rich carcinoma occurring in a 53-year-old female patient, and the literature is reviewed.

Recombinant adenoviruses expressing TRAIL demonstrate antitumor effects on non-small cell lung cancer (NSCLC)

INTRODUCTION

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in a variety of malignant cells, but not in normal cells. This preferential toxicity to the abnormal cells renders TRAIL potentially a very powerful therapeutic weapon against cancer. However, a requirement for large quantities of TRAIL to suppress tumor growth in vivo is one of the major factors that has hindered it from being widely applied clinically. To overcome this, we constructed a replication-deficient adenovirus that carries a human full-length TRAIL gene (Ad-TRAIL) and tested its efficacy against a lung cancer model system in comparison to that of the recombinant soluble TRAIL protein.

METHODS

To investigate the antitumor activity and therapeutic value of the Ad-TRAIL on the non-small cell lung cancer (NSCLC), four NSCLC cell lines, namely, YTMLC, GLC, A549, and H460 cells, were used. TRAIL protein expression was determined by Western blotting and flow cytometry. Cell viability was analyzed by proliferation assay, and DNA ladder and cell-cycle analysis were used to identify apoptosis. To further evaluate the effect of Ad-TRAIL in vivo, YTMLC cells were inoculated to the subcutis of nude mice. The Ad-TRAIL was subsequently administered into the established tumors. Tumor growth and the TRAIL toxicity were evaluated after treatment.

RESULTS

YTMLC cells infected with Ad-TRAIL showed decreased cell viability and a higher percentage of apoptosis. Similar, Ad-TRAIL treatment also significantly suppressed tumor growth in vivo.

CONCLUSIONS

TRAIL gene therapy provides a promising therapy for the treatment of NSCLC.

Topology optimization and fabrication of photonic crystal structures

Topology optimization is used to design a planar photonic crystal waveguide component resulting in significantly enhanced functionality. Exceptional transmission through a photonic crystal waveguide Z-bend is obtained using this inverse design strategy. The design has been realized in a silicon-on-insulator based photonic crystal waveguide. A large low loss bandwidth of more than 200 nm for the bandgap polarization is experimentally confirmed.

Development of a fragment constant method for estimating the mixture toxicity

Based on Group Contribution Theory, a fragment constant model to estimate mixture toxicity is proposed in this paper. The toxicity (EC50M) of 58 mixtures is determined using Photobacterium phosphoreum. Analysis of these EC50M and the mole fraction of the individual chemical fragments (Br, Cl, NO2, OH, NH2) helps work out the fragment toxicity contribution (deltaTi) to EC50M. Thus, a linear regression equation is established between the toxicity contribution deltaTi and the fragment constants of Hansch f(i), and this equation is so significant that it helps provide an approach for calculating EC50M.

Tunable optical properties of colloidal quantum dots in electrolytic environments

The absorption spectra of colloidal cadmium sulfide quantum dots in electrolytic solutions are found to manifest a shift in the absorption threshold as the concentration of the electrolyte is varied. These results are consistent with a shift in the absorption threshold that would be caused by electrolytic screening of the field caused by the intrinsic spontaneous polarisation of these würtzite structured quantum dots. These electrolyte-dependent absorption properties provide a potential means of gaining insights on the variable extracellular and intracellular electrolytic concentrations that are present in biological systems.

Quantification of 3-D regional myocardial deformation: shape-based analysis of magnetic resonance images

A comprehensive three-dimensional (3-D) shape-based approach for quantification of regional myocardial deformations was evaluated in a canine model (n = 8 dogs) with the use of cine magnetic resonance imaging. The shape of the endocardial and epicardial surfaces was used to track the 3-D trajectories of a dense field of points over the cardiac cycle. The shape-based surface displacements are integrated with a continuum biomechanics model incorporating myofiber architecture to estimate both cardiac- and fiber-specific endocardial and epicardial strains and shears for 24 left ventricular regions. Whereas radial and circumferential end-systolic strains were fairly uniform, there was a significant apex-to-base gradient in longitudinal strain and radial-longitudinal shear. We also observed transmural epicardial-to-endocardial gradients in both cardiac- and fiber-specific strains. The increase in endocardial strain was accompanied by increases in radial-longitudinal shear and radial-fiber shears in the endocardium, supporting previous theories of regional myocardial deformation that predict considerable sliding between myocardial fibers.

Chaoslike behavior in nonchaotic systems at finite computation precision

The dynamical behavior of a two-dimensional map is investigated numerically. A chaoslike behavior, i.e., a nonsmooth distribution of the attractor and seemly sensitive dependence of the motion on initial condition is found as the system state is nonchaotic (both Lyapunov exponents are nonpositive). The key point for this strange behavior is that the mode corresponding to the second negative Lyapunov exponent contains positive local Lyapunov exponent segments. It is argued that this kind of behavior may be typical and easily observed in practical numerical computations and experiments where small noise is inevitable.

[A quantum chemical study of pi-back-donation bond and Raman intensity of 1 sigma + electronic state of Pt-CO molecule]

The Raman spectroscopic properties of Pt-CO molecule have been investigated based on the electronic state 1 sigma + determined by the HF and B3LYP methods. The result shows that the calculated stretching vibrational frequencies of the Pt-C and C-O bonds depend on the method and the basis sets used. It indicates that it is important to adopt an appropriate method to describe pi-donation and pi-back-donation bond. The result of the differential Raman scattering cross section for the stretching vibrations of the Pt-C and C-O bond shows that the latter is significantly larger value compared to the former.

[Fuzzy space based segmentation algorithm on periosteum medical image processing]

Object description in medical image often has the property of fuzziness, and with the development of computing, fuzzy logical theories are progressively used in medical image processing. Color medical images differ in spacial presentation and fuzzy description from grey-scale images and must be analyzed by special methods. In this paper, a new method of bone cell segmentation based on fuzzy logical theories is presented. With the utilization of fuzzy set theories in the steps of color enhancing, feature extraction and automatical segmentation, bone cells are detected from the background. The method has the advantages of high accuracy and flexibility to many situations. Experiments of bone cell images have proved that it is a fast and effective method.

Point-tracked quantitative analysis of left ventricular surface motion from 3-D image sequences

We propose and validate the hypothesis that we can use differential shape properties of the myocardial surfaces to recover dense field motion from standard three-dimensional (3-D) image sequences (MRI and CT). Quantitative measures of left ventricular regional function can be further inferred from the point correspondence maps. The noninvasive, algorithm-derived results are validated on two levels. First, the motion trajectories are compared to those of implanted imaging-opaque markers of a canine model in two imaging modalities, where subpixel accuracy is achieved. Second, the validity of using motion parameters (path length and thickness changes) for detecting myocardial injury area is tested by comparing algorithms derived results to postmortem analysis TTC staining of myocardial tissue, where the achieved Pearson product-moment correlation value is 0.968.

Effect of lanthanum on ion absorption in cucumber seedling leaves

Scanning electron microscope and energy-dispersive X-ray analysis were used to study the tissular distributions of elements Na, Mg, Cl, K, Ca, Mn, and Fe in leaves of cucumber seedlings in the absence or presence of La3+. The results showed that the atomic percentages of Na, Mg, Cl, K, and Ca were basically reduced and those of Mn and Fe were increased in the presence of La3+; in addition, at 0.02 mM La3+, the reduced or increased degrees were higher than those at 2.0 mM La3+. The effects of La3+ on ion absorption were similar to those of Ca2+, suggesting that the rare earth element lanthanum affects the plant physiological mechanism by regulating the Ca2+ level in plant cell.

[Computer-assisted identification of fundus lesions and a study of its reliability]

This study aimed at the use of computer for identifying fundus lesions quickly and reliably. We adopted the 'area filling' method to program in Visula C++, used the program to mesure the retina cotton-wool patches in diabetics (15 eyes), and then calculated the coefficient of variation to evaluate its reproducibility. The results showed that the coefficient of variation of the measurements ranged from 3.22% to 9.46%. In conclusion, this method is convient, quick and reliable.

Physical and geometrical modeling for image-based recovery of left ventricular deformation

Information about left ventricular (LV) mechanical performance is of critical importance in understanding the etiology of ischemic heart disease. Regional measurements derived from non-invasive imaging to assist in assessing this performance have been in use for decades, and certain parameters derived from these measurements often are useful clinically, as they correlate to some extent with gross physiological hypotheses. However, relatively little work has been done to date to carefully understand the relationship of regional myocardial injury to the local mechanical performance of the heart as derived from image data acquired non-invasively for a particular patient in 3 spatial dimensions over time. This paper describes efforts to take advantage of recent developments in 3D non-invasive imaging and biomechanical modeling to design an integrated computational platform capable of assembling a variety of displacement and velocity data derived from each image frame to deform a volumetric model representation of a portion of the myocardium. A brief description of the reasoning behind this strategy an overview of the approach and some initial results are described.

The COOH-terminal tyrosine phosphorylation sites on IRS-1 bind SHP-2 and negatively regulate insulin signaling

Activation of tyrosine kinases by numerous growth factor and cytokine receptors leads to tyrosine phosphorylation of the insulin receptor substrate (IRS)-proteins. Tyrosine-phosphorylated motifs on the IRS proteins bind to the SH2 domains in proteins that mediate downstream signals, including phosphatidylinositol 3'-kinase, GRB-2, and SHP-2. We investigated the function of the two SHP-2 binding COOH-terminal tyrosines of IRS-1 by replacing them with phenylalanine (IRS-1(FCT)). IRS-1(FCT) failed to bind SHP-2 or mediate its tyrosine phosphorylation during insulin stimulation. Although several reports suggest a critical role for SHP-2 in insulin stimulated mitogen-activated protein kinase activation and cell proliferation, IRS-1(FCT) mediated these effects normally in 32D cells. Indeed, IRS-1(FCT) exhibited increased tyrosine phosphorylation, phosphatidylinositol 3'-kinase binding and activation of protein synthesis in response to insulin. These results suggest that SHP-2 attentuates the phosphorylation and downstream signal transmission of IRS-1 and that the interaction of IRS-1 and SHP-2 is an important regulatory event which attenuates insulin metabolic responses.

[Effects of opium peptide system on the temperature regulation of mice under dry-hot environment with different temperature]

The Kunming mice were selected as subjects. Animals were allowed to move and drink freely. The Naloxone(0.02 mg/g) was injected by abdominal cavity. The ability to body temperature stable by mice under the environment with high temperature (41 degrees C, 43 degrees C) was observed. The results showed that after obstructing opium receptor by Naloxone, the ability mentioned above was reduced obviously.

Nitric oxide affects LTP in area CA1 and CA3 of hippocampus in low-level lead-exposed rat

Neonatal Wistar rats were exposed to lead from parturition to weaning via the milk of dams drinking 0.2% lead acetate solution. The alterations in EPSPs in areas CA1 and CA3 of hippocampal slices of 60-day-old adult rats following developmental lead exposure were studied. The results demonstrate that lead exposure in neonatal rats causes a decrease in LTP in area CA1 and an increase in LTP in area CA3. The effects of exposure to NO-generating compound sodium nitroprusside (SNP) on LTP in areas CA1 and CA3 of control and lead-exposed rats were also tested. The data demonstrate that NO causes an increase in LTP in area CA1 and no different alterations in area CA3 of lead-exposed rats. The results also demonstrate that NO may be a messenger molecule in areas CA1 and CA3. It suggests that lead might selectively interfere with specific neurochemical pathways in the hippocampus.

Expression cloning of an AVP-activated, calcium-mobilizing receptor from rabbit kidney medulla

Arginine vasopressin (AVP) is a nonapeptide that regulates body fluid and blood pressure homeostasis. We have used expression cloning in the Xenopus laevis oocyte system to identify cDNA clones from a rabbit renal medullary expression library encoding an AVP receptor linked to Ca2+ mobilization. cRNA generated from positive clones conferred upon oocytes the capacity to mobilize intracellular Ca2+ in response to AVP. A cDNA clone encoding a protein of 780 amino acids was isolated, sequenced, and subcloned into an SV40-based expression vector. Expression of the cloned protein [designated the vasopressin-activated, calcium-mobilizing (VACM-1) protein] in COS-1 cells, resulted in increased 125I-labeled AVP binding [dissociation constant (Kd) of approximately 2 nM] and increased AVP-induced mobilization of Ca2+. Importantly, 125I-AVP could be immunoprecipitated both from detergent-solubilized membranes from COS-1 cells expressing VACM-1 protein and from an in vitro translation system, in which VACM-1 protein was synthesized, using antibodies prepared against a synthetic peptide derived from the NH2-terminal sequence of VACM-1. Interestingly, immunohistochemical staining of rabbit kidney sections with this antibody showed specific staining of collecting tubule epithelia. The deduced amino acid sequence is not homologous with any nucleic acid or amino acid sequences reported to date, including those of the V1 and V2 AVP receptors. The VACM-1 protein may represent a novel AVP receptor.