A review of the pharmacological action and mechanism of natural plant polysaccharides in depression

Depression is a prevalent mental disorder. However, clinical treatment options primarily based on chemical drugs have demonstrated varying degrees of adverse reactions and drug resistance, including somnolence, nausea, and cognitive impairment. Therefore, the development of novel antidepressant medications that effectively reduce suffering and side effects has become a prominent area of research. Polysaccharides are bioactive compounds extracted from natural plants that possess diverse pharmacological activities and medicinal values. It has been discovered that polysaccharides can effectively mitigate depression symptoms. This paper provides an overview of the pharmacological action and mechanisms, intervention approaches, and experimental models regarding the antidepressant effects of polysaccharides derived from various natural sources. Additionally, we summarize the roles and potential mechanisms through which these polysaccharides prevent depression by regulating neurotransmitters, HPA axis, neurotrophic factors, neuroinflammation, oxidative stress, tryptophan metabolism, and gut microbiota. Natural plant polysaccharides hold promise as adjunctive antidepressants for prevention, reduction, and treatment of depression by exerting their therapeutic effects through multiple pathways and targets. Therefore, this review aims to provide scientific evidence for developing polysaccharide resources as effective antidepressant drugs.

Whole-transcriptome sequencing with ceRNA regulation network construction and verification in glioblastoma

OBJECTIVES

To explore the key genes involved in the occurrence and development of glioblastoma (GBM) by analyzing whole-transcriptome sequencing and biologic data from GBM and normal cerebral cortex tissues and to search for important noncoding RNA (ncRNA) molecular markers based on the competitive endogenous RNA (ceRNA) network.

METHODS

Ten GBM and normal cerebral cortex tissues were collected for full transcriptome sequencing, screened for differentially expressed (DE) mRNAs, miRNAs, lncRNAs, and circRNAs, and subjected to bioinformatic analysis. We constructed a Protein-Protein Interaction (PPI) network and a circRNA/lncRNA-miRNA-mRNA regulatory network and identified them using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Finally, The Cancer Genome Atlas (TCGA) and Chinese Glioma Genome Atlas (CGGA) databases were used to validate and conduct a survival analysis of the target genes.

RESULTS

A total of 5341 DEmRNAs, 259 DEmiRNAs, 3122 DElncRNAs, and 2135 DEcircRNAs were identified. Enrichment analysis showed that target genes regulated by DEmiRNA, DElncRNA, and DEcircRNA were closely related to chemical synaptic transmission and ion transmembrane transport. A PPI network analysis screened 10 hub genes that directly participate in tumor cell mitosis regulation. In addition, the ceRNA composite network showed that hsa-miR-296-5p and hsa-miR-874-5p were the central nodes of the network, and the reliability of relevant key molecules was successfully verified through RT-qPCR identification and the TCGA database. The CGGA database survival analysis produced 8 DEmRNAs closely related to GBM patient survival prognosis.

CONCLUSIONS

This study revealed the important regulatory functions and molecular mechanisms of ncRNA molecules and identified hsa-miR-296-5p and hsa-miR-874-5p as key molecules in the ceRNA network. They may play an important role in GBM pathogenesis, treatment, and prognosis.

Icariin exhibits protective effects on cisplatin-induced cardiotoxicity via ROS-mediated oxidative stress injury in vivo and in vitro

BACKGROUND

Cisplatin-induced cardiotoxicity severely limits its clinical application as an antitumor drug and increases the risk of cardiovascular disease. Icariin (ICA), the main flavonoid isolated from Epimedii Folium, has been demonstrated to have various beneficial effects on cardiovascular disease. However, the protective effect of ICA against cisplatin-induced cardiotoxicity remains unclear.

PURPOSE

In present study, we explored the protective action of ICA against cisplatin-induced cardiotoxicity and its possible molecular mechanisms in vitro and in vivo.

METHODS

Mice were intraperitoneally injected with cisplatin 4 mg/kg every other day for 7 times to establish myocardial injury model. ICA (15, 30 mg/kg) was administered to mice by gavage for 21 days. H9c2 cells were treated with ICA (3, 6, 12 µM) in the presence or absence of cisplatin (40 µM), and then cell viability, oxidative stress, apoptosis, and mitochondrial function were evaluated.

RESULTS

Biochemical index detection and histopathological staining analysis showed that ICA had a good protective effect on cisplatin-induced cardiotoxicity. Cellular experiments showed that ICA inhibited cisplatin-induced oxidative stress in a dose-dependent manner by regulating the levels of glutathione peroxidase (GSH-Px), catalase (CAT), superoxide dismutase (SOD) and malondialdehyde (MDA). ICA could inhibit the expression of NF-κB and the secretion of inflammatory factors, thereby alleviating the inflammatory injury caused by cisplatin. In addition, ICA could alleviate cisplatin-induced myocardial injury by activating SIRT1 and PI3K/Akt signaling pathways and inhibiting MAPKs signaling pathway.

CONCLUSION

These results suggest that ICA could attenuate cisplatin-induced cardiac injury by inhibiting oxidative stress, inflammation and apoptosis, laying a foundation for ICA to reduce chemotherapy-induced cardiotoxicity in clinical practice.

Supplementation of Saponins from Leaves of Panax quinquefolius Mitigates Cisplatin-Evoked Cardiotoxicity via Inhibiting Oxidative Stress-Associated Inflammation and Apoptosis in Mice

Background: Although kidney injury caused by cisplatin has attracted much attention, cisplatin-induced cardiotoxicity is elusive. Our previous studies have confirmed that saponins (ginsenosides) from Panax quinquefolius can effectively reduce acute renal injuries. Our current study aimed to identify the potential effects of saponins from leaves of P. quinquefolius (PQS) on cisplatin-evoked cardiotoxicity. Methods: Mice were intragastrically with PQS at the doses of 125 and 250 mg/kg daily for 15 days. The mice in cisplatin group and PQS + cisplatin groups received four times intraperitoneal injections of cisplatin (3 mg/kg) two days at a time from the 7th day, respectively. All mice were killed at 48 h following final cisplatin injection. Body weights, blood and organic samples were collected immediately. Results: Our results showed that cisplatin-challenged mice experienced a remarkable cardiac damage with obvious histopathological changes and elevation of lactate dehydrogenase (LDH), creatine kinase (CK), creatine kinase isoenzyme MB (CK-MB) and cardiac troponin T (cTnT) concentrations and viabilities in serum. Cisplatin also impaired antioxidative defense system in heart tissues manifested by a remarkable reduction in reduced glutathione (GSH) content and superoxide dismutase (SOD) activity, demonstrating the overproduction of reactive oxygen species (ROS) and oxidative stress. Interestingly, PQS (125 and 250 mg/kg) can attenuate cisplatin-evoked changes in the above-mentioned parameters. Additionally, PQS administration significantly alleviated the oxidation resulted from inflammatory responses and apoptosis in cardiac tissues via inhibition of overexpressions of TNF-α, IL-1β, Bax, and Bad as well as the caspase family members like caspase-3, and 8, respectively. Conclusion: Findings from our present research clearly indicated that PQS exerted significant effects on cisplatin-induced cardiotoxicity in part by inhibition of the NF-κB activity and regulation of PI3K/Akt/apoptosis mediated signaling pathways.

[Simulation of Multimedia Transfer and Fate of Perfluorooctane Sulfonate (PFOS) in Shenzhen Region]

To study the transfer and fate of perfluorooctane sulfonate (PFOS) in Shenzhen region, a level Ⅲ fugacity model was used to simulate and calculate the concentrations of PFOS in local air, water, soil and sediment. Physical and chemical parameters of PFOS and environmental parameters of Shenzhen were entered into the model. The simulated concentrations were compared with actual measurements to validate the model, and then analyzed based on the transfer flux of PFOS between media to identify the main transfer route. The input parameters and output results of the model underwent sensitivity analysis and uncertainty analysis, respectively. The simulated concentrations of PFOS in air, water, soil and sediment were 1.4 pg·m^-3, 7.0 ng·L^-1, 0.39 μg·kg^-1 and 0.11 μg·kg^-1, in good agreement with the actual measurements. The transfer from air to soil, soil to water and air to water were the main PFOS transfer routes between media, accounting for 32%, 32%, 5.8% of total transfer, respectively. The transfer through water was the major PFOS outlet from a region. The advective input of air and water, temperature, PFOS solubility, precipitation and density of soil and sediment were the key parameters affecting the model output. Uncertainty analysis showed that the coefficient of variation of PFOS concentrations reached the minimum in water and the maximum in soil, which may be caused by the highly changeable content of organic carbon in soil.

[Performance evaluation of two N95 filtering-facepiece respirators on decomposition products of sulfur hexafluoride]

OBJECTIVE

To assess the filtration efficiency of two N95 filtering-facepiece respirators (FFRs) for the decomposition products of sulfur hexafluoride (SF6).

METHODS

Two types of N95 FFRs (the particulate and the acid-proof respirators) were selected in this study. The decomposition products of SF6, including particles, hydrogen fluoride (HF) and sulfur dioxide (SO2) , were measured under experimental condition by using TSI PortaCount Plus, fluorine ion-selective electrodes and spectrophotometer separately. The filtration efficiency was then calculated and compared.

RESULTS

Both two models of N95 respirators had lowest filtration efficiency larger than 95% for particles under airflow ranged from 10 to 95 L/min. When exposed to different concentrations of HF (low: 0.00~1.99 mg/m(3), middle: 2.00~3.99 mg/m(3), high: >4 mg/m(3)) , the acid-proof N95 respirator was more effective than the particulate respirator (P<0.05) with a filtration efficiency of 98.83%, 99.08%, and 99.03% versus 48.44%, 45.71%, and 47.31%. For four SO2 concentration ranges (0.00~2.49 mg/m(3), 2.50~4.99 mg/m(3), 5.00~9.99 mg/m(3), and >10.00 mg/m(3)) , the acid-proof respirator showed a high filtration efficiency within exposure to 1.5 hours: 95.73%, 98.67%, 98.14%, and 97.78%, respectively, when exposure duration extended to 4 hours, the filtration efficiency of the acid-proof respirator decreased to 91.97%, 82.28%, 70.12%, and 58.56%, respectively.

CONCLUSION

Both the particulate and the acid-proof N95 FFRs met national standards on the particulate filtration efficiency. The acid-proof N95 respirator demonstrates to be more effective in filtering HF and SO2 than the particulate respirator. The filtration efficiency could decrease to an unsafe condition under longer exposure duration, timely replacement of respirator is recommended at the workplace.

[Spectral analysis of polyphenol oxidase (PPO) and lipoxygenase (LOX) treated by pulsed electric field]

Inactivation effect of pulsed electric field (PEF) on polyphenol oxidase (PPO) and lipoxygenase (LOX) was investigated using a laboratory PEF system with a coaxial treatment chamber. Circular dichroism (CD) and fluorescence analysis were used to study the conformation change of the protein. The experimental results show that PPO and LOX can be effectively inactivated by the PEF treatment. Inactivation effect of PPO and LOX increases with the increase in the applied electric strength and the treatment time. Activity of PPO and LOX can be reduced by 60.3% and 21.7% at 20 kV x cm(-1) after being treated for 320 micros respectively. The decrease of the negative peaks (208 and 215 nm in PPO spectra, 208 nm and 218 nm in LOX spectra) in CD spectra of PPO and LOX shows that PEF treatment caused a loss of alpha-helix and increase in beta-sheet content, indicating that conformation changes occur in the secondary structure of PPO and LOX enzyme. This effect was strengthened as the applied electric field increased: alpha-helical content of PPO and LOX was 56% and 29% after being treated at 8 kV x cm(-1), however, when the electric field was increased up to 20 kV x cm(-1), alpha-helical content of PPO and LOX decreased to 21% and 16% respectively. The decrease rate of alpha-helix and increase rate of beta-sheet in PPO are higher than LOX, indicating that the second conformation of PPO is less resistant to PEF treatment than LOX. The fluorescence intensity of LOX increases after PEF treatment. At the same time, increasing the applied pulsed electric field increases the fluorescence intensity emitted. Fluorescence measurements confirm that tertiary conformation changes occur in the local structure of LOX. However the possible mechanism of the conformation change induced by the PEF treatment is beyond the scope of the present investigation.

Electromagnetic pulses induce fluctuations in blood pressure in rats

PURPOSE

To investigate the effects of exposure to electromagnetic pulses (EMP) on functional indices of the cardiovascular system in male Sprague-Dawley rats.

MATERIALS AND METHODS

A tapered parallel plate Gigahertz Transverse Electromagnetic cell (GTEM cell) with a flared rectangular coaxial transmission line was used to expose the rats to EMP (0.5 pps, total 200 pulses and whole-body averaged specific absorption rate 50 mW/kg at 200 kV/m or 75 mW/kg at 400 kV/m). Concurrent sham-exposed animals were used as controls. Cardiovascular functions, namely, heart rate, and systolic, mean and diastolic blood pressures were measured immediately and up to 4 weeks post-exposure using a non-invasive tail-cuff photoelectric sensor sphygmomanometer.

RESULTS

The heart rates in sham- and EMP-exposed rats were not significantly changed. In the exposed rats, increased systolic blood pressure (SBP) occurred at 0 h and decreased SBP occurred at 1 day and 3 days after exposure. Significantly higher diastolic blood pressure (DBP) was found at 0 h and significantly lower DBP was found at 12 h, 1 day, and 1 month after exposure. Significantly higher mean arterial pressure (MAP) was noted at 0 h and significantly lower MAP was noted at 1 day.

CONCLUSIONS

Significant alterations in arterial blood pressure were observed in rats exposed to EMP exposure while heart rate was not altered.

Plasma induced degradation of Indigo Carmine by bipolar pulsed dielectric barrier discharge(DBD) in the water-air mixture

Degradation of the Indigo Carmine (IC) by the bipolar pulsed DBD in water-air mixture was studied. Effects of various parameters such as gas flow rate, solution conductivity, pulse repetitive rate and ect., on color removal efficiency of dying wastewater were investigated. Concentrations of gas phase o3 and aqueous phase H2O2 under various conditions were measured. Experimental results showed that air bubbling facilitates the breakdown of water and promotes generation of chemically active species. Color removal efficiency of IC solution can be greatly improved by the air aeration under various solution conductivities. Decolorization efficiency increases with the increase of the gas flow rate, and decreases with the increase of the initial solution conductivity. A higher pulse repetitive rate and a larger pulse capacitor C(p) are favorable for the decolorization process. Ozone and hydrogen peroxide formed decreases with the increase of initial solution conductivity. In addition, preliminary analysis of the decolorization mechanisms is given.

Analytical expressions of quadratic and cubic phases in a three-element resonator for kerr-lens mode locking

We present analytical expressions of quadratic and cubic phases in a three-element resonator for Kerr-lens mode locking. Variation of quadratic and cubic phases with wedge angles of Ti:sapphire and apex angles of a prismatic output coupler are calculated. The results provide a theoretical basis for the design of a three-element cavity.

Gene expression networks underlying retinoic acid-induced differentiation of acute promyelocytic leukemia cells

To elucidate the molecular mechanism of all-trans-retinoic acid (ATRA)-induced differentiation of acute promyelocytic leukemia (APL) cells, the gene expression patterns in the APL cell line NB(4) before and after ATRA treatment were analyzed using complementary DNA array, suppression-subtractive hybridization, and differential-display-polymerase chain reaction. A total of 169 genes, including 8 novel ones, were modulated by ATRA. The ATRA-induced gene expression profiles were in high accord with the differentiation and proliferation status of the NB(4) cells. The time courses of their modulation were interesting. Among the 100 up-regulated genes, the induction of expression occurred most frequently 12-48 hours after ATRA treatment, while 59 of 69 down-regulated genes found their expression suppressed within 8 hours. The transcriptional regulation of 8 induced and 24 repressed genes was not blocked by cycloheximide, which suggests that these genes may be direct targets of the ATRA signaling pathway. A balanced functional network seemed to emerge, and it formed the foundation of decreased cellular proliferation, maintenance of cell viability, increased protein modulation, and promotion of granulocytic maturation. Several cytosolic signaling pathways, including JAKs/STAT and MAPK, may also be implicated in the symphony of differentiation. (Blood. 2000;96:1496-1504)

Primary structure, tissue distribution, and expression of mouse phosphoinositide-dependent protein kinase-1, a protein kinase that phosphorylates and activates protein kinase Czeta

Phosphoinositide-dependent protein kinase-1 (PDK1) is a recently identified serine/threonine kinase that phosphorylates and activates Akt and p70(S6K), two downstream kinases of phosphatidylinositol 3-kinase. To further study the potential role of PDK1, we have screened a mouse liver cDNA library and identified a cDNA encoding the enzyme. The predicted mouse PDK1 (mPDK1) protein contained 559 amino acids and a COOH-terminal pleckstrin homology domain. A 7-kilobase mPDK1 mRNA was broadly expressed in mouse tissues and in embryonic cells. In the testis, a high level expression of a tissue-specific 2-kilobase transcript was also detected. Anti-mPDK1 antibody recognized multiple proteins in mouse tissues with molecular masses ranging from 60 to 180 kDa. mPDK1 phosphorylated the conserved threonine residue (Thr402) in the activation loop of protein kinase C-zeta and activated the enzyme in vitro and in cells. Our findings suggest that there may be different isoforms of mPDK1 and that the protein is an upstream kinase that activates divergent pathways downstream of phosphatidylinositol 3-kinase.

[The role of accumbens nucleus in the inhibitory effect of somatic afferent inputs on the defence cardiovascular response and its mechanism]

After Accumbens Nucleus (AC) lesion, the inhibitory effect of deep peroneal nerve (DPN) on the pressor response and ECG-ST changes induced by excitation of dorsomedial nucleus of hypothalamus (DMH) was decreased as compared with that of before lesion (P < 0.05, P < 0.01). Electrical stimulation of AC could elicit prominent depressor response, which could be effectively lessened by microinjection of naloxone into ventral periaqueductal gray (vPAG). Lesion of vPAG could reverse the depressor response to AC stimulation to a slight pressor response (P < 0.01). After lesion of arcuate nucleus of hypothalamus (ARC), the depressor response to AC stimulation almost disappeared, which, again, could be largely mimicked by microinjection of naloxone into ARC.

[Spinal mechanism of the inhibitory effect of somatic input on the cardiac ischemia induced by hypothalamus stimulation]

Experiments were carried out on 58 urethane-chloralose anaesthetized, gallamine triethiodide immobilized and vagotomized rabbits under artificial ventilation. Median nerve (MN) or deep peroneal nerve(DPN) stimulation could inhibit completely or partially the deflection of ischemic ECG ST segment due to stimulation of dorsomedial hypothalamic nucleus (DMH). The inhibitory effect of MN stimulation was more marked than that of DPN stimulation. Intrathecal injection (ith) of morphine (40 micrograms) could also inhibit these ischemic ECG ST segment changes. After ith naloxone (20 micrograms), the inhibitory effect of MN stimulation on DMH stimulation-induced ischemic ECG ST segment changes was abolished. In intact rabbits, it was demonstrated that L-enkephalin (LENK) immunoreactive material was increased in the left or right intermediolateral cell column (IML) of T2-5 spinal cord after stimulation of left MN or DPN for five minutes. In the Cl transected rabbits, stimulation of MN only increased ipsilateral LENK immunoreactive material content in the thoracic IML, while stimulation of DPN produced no such an effect. These results indicate that stimulation of MN or DPN can inhibit cardiac ischemia induced by DMH stimulation and that the effect of MN stimulation is more potent. The inhibitory effects may be mediated by an increase of LENK immunoreactive material in the bilateral IML produced through some supraspinal mechanisms; whereas the effect of MN stimulation may also be mediated by an increase of ipsilateral spinal LENK immunoreactive material in the thoracic IML through segmental mechanism to inhibit the sympathetic activity.

High channel-mediated water permeability in rabbit erythrocytes: characterization in native cells and expression in Xenopus oocytes

Erythrocytes from several mammalian species contain mercurial-sensitive water transporters. By a stopped-flow light scattering technique, osmotic water permeability (Pf) was exceptionally high in rabbit erythrocytes (0.053 +/- 0.002 cm/s) and reversibly inhibited by 98% by p-(chloromercuri)benzenesulfonate (pCMBS). The activation energy (Ea) was 4.6 kcal/mol (15-37 degrees C). pCMBS inhibition was half-maximal at 0.1 mM (60-min incubation); at 1 mM pCMBS, half-maximal inhibition occurred in 8 min. Pf was also inhibited by HgCl2 and pCMB with greater than 90% inhibition in 5 min. There was no inhibition by high concentrations of phloretin, DNDS, cytochalasin B, amiloride, ouabain, furosemide, and several proteases. In defolliculated Xenopus oocytes microinjected with 50 nL of water or unfractionated mRNA (1 mg/mL) from rabbit reticulocytes, oocyte Pf assayed at 10 degrees C after 72-h incubation increased from (4 +/- 1) X 10(-4) cm/s (water injected) to (18 +/- 2) X 10(-4) cm/s (mRNA injected). Pf increased linearly with [mRNA] (0-75 ng/oocyte) and was inhibited slowly and reversibly by pCMBS and immediately by HgCl2 but not by cytochalasin B, phloretin, or DNDS. Ea was 9.6 kcal/mol (water injected) and 2.6 kcal/mol (mRNA injected). These results demonstrate that rabbit erythrocytes have the highest Pf and the greatest percentage inhibition of Pf by mercurials of any mammalian erythrocyte studied. The characteristics of the expressed and native water channels were similar, suggesting that the erythrocyte water channel is a membrane protein suitable for expression cloning.

[Effect of hypothalamic stimulation on RMBF and SP content in IML of spinal cord in rabbits]

Experiments were performed on 48 urethane-chloralose anaesthetized, gallamine triethiodide immobilized and vagotomized rabbits under artificial ventilation. Radiolabeled microspheres were injected into the left atrium during stimulation of the left or right dorsomedial hypothalamic nucleus (LDMH or RDMH) to measure regional myocardial blood flow (RMBF). RDMH stimulation produced relatively little flow reduction of the left ventricle, whereas LDMH stimulation produced an obvious flow reduction. No significant change occurred in the right ventricle. Meanwhile, LDMH or RDMH stimulation caused increases of mean arterial blood pressure (MABP) and changes of epicardial electrogram (EECG) ST segment, but no significant changes in heart rate. EECG ST segment was elevated in relation to the reduction of RMBF in left ventricle (r = -0.825, P less than 0.001). Linear regression analysis of MABP change in relation to left ventricle RMBF showed no significant correlation. In intact rabbits, it was demonstrated that DMH stimulation caused an decrease of substance P (SP) immunoreactive material in bilateral intermediolateral cell columns (IML) of T2-5 spinal cord concomitantly with an elevation in MABP and EECG ST changes. The results suggest that electrical stimulation of DMH can elicit coronary constriction, decrease in RMBF, elevation of EECG ST segment and increase in MABP, which may be mediated by the release of SP immunoreactive material in the IML of the spinal cord.

Water and urea permeability properties of Xenopus oocytes: expression of mRNA from toad urinary bladder

The Xenopus oocyte was evaluated as an mRNA expression system for water and urea transporters. Osmotic water permeability (Pf) was measured from the time course of oocyte volume in response to osmotic gradients using a real-time imaging method. Diffusional water permeability (Pd) was measured by 3H2O efflux. In mature oocytes treated with collagenase to remove the follicular cell layer, Pf was 8.6 +/- 0.6 x 10(-4) (SD) cm/s (n = 32) at 25 degrees C and independent of the time after oocyte removal (0-8 days). The activation energy (Ea) for Pf was 10.2 kcal/mol (10-32 degrees C). Pf was independent of osmotic gradient size (50-200 mosmol) in swelling experiments but decreased in an unpredictable manner in shrinking experiments. Pf was not altered by removal of the vitelline membrane but was decreased by 75% when the follicular cell layer was intact. In collagenase-treated oocytes, amphotericin (0-500 micrograms/ml) increased Pf from 8 x 10(-4) to 84 x 10(-4) cm/s in a dose-dependent manner. Pd was 3.4 +/- 0.2 x 10(-4) (SE) cm/s at 25 degrees C, 1.5 +/- 0.2 x 10(-4) cm/s at 4 degrees C, and 5.1 +/- 0.5 x 10(-4) cm/s at 25 degrees C in the presence of 500 micrograms/ml amphotericin; Ea was 6.5 kcal/mol. Thus Pd, but not Pf, is unstirred layer limited.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of mRNA coding for kidney and red cell water channels in Xenopus oocytes

The existence and identity of protein water transporters in biological membranes has been uncertain. Osmotic water permeability (Pf) was measured in defolliculated Xenopus oocytes microinjected with water or mRNA from kidney cortex, kidney papilla, reticulocyte, brain, and muscle. Pf was measured by quantitative image analysis from the time course of oocyte swelling in response to an osmotic gradient. When assayed at 10 degrees C, Pf in water-injected oocytes increased from (3.6 +/- 0.9) x 10(-4) cm/s (S.D., n = 16) to 74 x 10(-4) cm/s with addition of amphotericin B, showing absence of unstirred layers. At 48-72 h after injection of 50 ng of unfractionated mRNA, Pf (in cm/s x 10(-4] was: 4.0 +/- 1.5 (rabbit brain, n = 15), 4.2 +/- 1.8 (rabbit muscle, n = 10), 18.4 +/- 6.3 (rabbit reticulocyte, n = 20), 16.1 +/- 5.6 (rat renal papilla, n = 24), 12.9 +/- 6.3 (rat renal cortex, n = 20), 14.4 +/- 6.1 (rabbit renal papilla, n = 15), and 11.8 +/- 3.4 (rabbit renal cortex, n = 8). In oocytes injected with mRNA from rat renal papilla, Pf was inhibited reversibly by 0.3 mM HgCl2 (4.1 +/- 1.6, n = 10); expressed water channels from kidney and red cell had activation energies of less than 4 kcal/mol. These results show functional oocyte expression of water channels from red cell, kidney proximal tubule (cortex), and the vasopressin-sensitive kidney collecting tubule (papilla), indicating that water channels are proteins, and providing an approach for the expression cloning of water channels.

Urea transport in freshly isolated and cultured cells from rat inner medullary collecting duct

Regulation of urea transport by vasopressin in inner medullary collecting duct (IMCD) cells is thought to be important for the urinary concentrating mechanism. Isolated tubule perfusion studies suggest the existence of a saturable urea carrier. We have measured 14C-urea efflux in IMCD cells which were freshly isolated and grown in primary culture. Cells were isolated from rat papilla by collagenase digestion and hypotonic shock. In suspended cells, 14C-urea efflux (Jurea) from loaded cells was exponential with time constant 59 +/- 3 sec (SEM, n = 6, 23 degrees C). Jurea had an activation energy of 4.1 kcal/mole and was inhibited 42 +/- 7% by 0.25 mM phloretin and 30-40% by the high affinity urea analogues dimethylurea and phenylurea. Jurea was increased 40-60% by addition of vasopressin (10(-8) M) or 8-bromo-cAMP (1 mM); stimulated Jurea was inhibited 55 +/- 8% by the kinase A inhibitor H-8. Phorbol esters and epidermal growth factor did not alter Jurea. IMCD cells grown in primary culture were homogeneous in appearance with greater than fivefold stimulation of cAMP by vasopressin. The exponential time constant for urea efflux was 610 +/- 20 sec (n = 3). Jurea was not altered by vasopressin, cAMP or phloretin. Another function of in vivo IMCD cells, vasopressin-dependent formation of endosomes containing water channels, was absent in the cultured cells. These results demonstrate presence of a urea transporter on suspended IMCD cells which is activated by cAMP and inhibited by phloretin and urea analogues. The urea transporter and its regulation by cAMP, and cAMP-dependent apical membrane endocytosis, are lost after growth in primary culture.

Isolation and partial characterization of two biologically active peptides from porcine spinal cord

Two biologically active peptides designated SCP-1 and SCP-2 have been isolated and partially characterized from porcine spinal cord. The results of amino acid analysis, electrophoresis, isoelectric focusing and the chromatographic analysis of the dansylated derivatives indicate that these two peptides are homogeneous. The amino acid composition and apparent untriakontapeptide and SCP-2 is a pentacospeptide. The N-terminal amino acids of SCP-1 and SCP-2 are Arginine and Tryptophan respectively. SCP-1 can stimulate the contraction of isolated guinea pig ileum and SCP-2 induces hypotension in anesthetized rat. Both SCP-1 and SCP-2 show no morphine-like activity. The chemical composition and biological properties of SCP-1 and SCP-2 distinguish them from any known peptide.