Novel thermotropic behavior of (diphenyl/phenyl-o-tolyl)phosphazene random copolymer

[(Ph₂PN)_0,76(Ph(o-tolyl)PN)_0,24] random copolymer (Ph: phenyl) was synthesized by the reaction of Ph₂POCH₂CF₃ and Ph(o-tolyl)POCH₂CF₃ with trimethylsilyl azide. Differential scanning calorimetry (DSC) measurements showed that this copolymer has a single glass transition at ≈ 80°C and transforms into a mesophase at 162 ～ 189°C depending upon the thermal history of the specimens. Lath shaped crystals with unit cell dimensions a = 1,30 nm, b = 1,13 nm and y = 87° (Form-I) were obtained from mixed dilute monochlorobenzene and p-xylene solution of the copolymer. Upon heating the specimens to 140°C, the “a” parameter of Form-I changes to a = 2,21 nm and the “b”, “y” remain unaltered (Form-II). When the specimens are cooled (10°C/min) from above T(1), the mesophase (δ-form) is “frozen in” and the δ-form specimens transform into Form-II by heating to 140°C. Another structure change (Form-III) occurs after the δ-form specimens were heated to 180°C followed by cooling below the glass transition temperature T_g. However, upon cooling the specimens slowly (0,2°C/min) from above T(1), Form-III results.     

The crystal structure of polylauryllactam (nylon 12)

The crystal structure of nylon 12 was determined from the X-ray diffraction patterns of uniaxially oriented specimens. The unit cell is monoclinic (pseudo-hexagonal) with the following dimensions: a = 4,79 Å, b = 31,9 Å (fiber axis), c = 9,58 Å, β = 120°. There are four monomeric units in the unit cell and the space group is P2₁/c. The structure presents a distortion of the amide group from the planar chain conformation and it is rather similar to γ-nylon 6. The hydrogen bond length is about 2,80 Å and the molecular packing is characterized by alternate, “up and down”, highly disordered sheets of parallel chains, linked by hydrogen bonds. The agreement between observed and calculated intensities has been improved by introducing a statistical disorder.     

The crystal structure of polycapryllactam (nylon 8) and of polycapriclactam (nylon 10)

From X-ray diffraction patterns of uniaxially oriented fibers, the structures of Nylon 8 and Nylon 10 were determined. They crystallize in the monoclinic system (pseudohexagonal), space group P2₁/b, with four monomeric units in the unit cell. The crystallographic parameters of Nylon 8 are: a=4,77; b=9,54; c=21,9 Å; γ=120°, and those of Nylon 10: a=4,78; b=9,56; c=26,9 Å; γ=120° (c fiber axis). Both structures show a γ-type molecular packing, characterized by a shortening of the fiber repeat distances and by a twisting of the amide groups. Therefore, pleated sheets of parallel chains joined by hydrogen bonds are formed and the direction of the chains in adjacent sheets is alternately “up and down”. These structures result very similar to those of Nylon 6 and Nylon 12 in γ-form, demonstrating once more that, in this series, by increasing the number of methylene groups, the usual crystal structure becomes the γ-form.     

Morphology of (methoxyethoxy/trifluoroethoxy)phosphazene copolymers

Block copolymers were synthesized by the anionically initiated copolymerization of (CH₃OCH₂CH₂O)(CF₃CH₂O)₂P? NSi(CH₃)₃, followed by the addition of (CF₃CH₂O)₃P? NSi(CH₃)₃. Random copolymers were made by simultaneous polymerization of these monomers. These copolymers exhibit a linear dependency on the mole fraction “m” of the repeating units bearing a methoxyethoxy pendant side group as well as on molecular weights. The thermal and morphological characteristics of the block copolymers are different from those of the random copolymers of analogous “m” and molecular weight. All copolymers undergo a mesophase T(1) transition for a range of temperatures depending upon “m” and molecular weights of the copolymers. Morphological and structural features essentially resemble those of the low molecular weight (trifluoroethoxy)phosphazene homopolymer. Upon heating and cooling the solution cast copolymer specimens through T(1), most of them transform into an orthorhombic form with the unit cell dimensions a = 2,060 nm, b = 0,940 nm and c = 0,486 nm from their initial monoclinic form with a = 1,003 nm, b = 0,937 nm, c = 0,486 nm and γ γ 91°. These unit cell dimensions agree completely with those of the low molecular weight PBFP. Complicated morphologies comprised of square and globular shapes that depend upon the copolymer composition were obtained from dilute tetrahydrofuran/p-xylene copolymer solutions. Electron microscopy directly reveals that chain extension occurs for the meltcrystallized copolymer specimen. The non-crystallizable minor component in the block copolymers is rejected from the crystal lattice. In the random copolymers, the methoxyethoxy pendant side group enters into the crystal lattice and influences their morphological and structural features.     

Effects of ADH on the apical and basolateral membranes of toad urinary bladder epithelial cells

Short-circuited urinary bladders from Bufo marinus were supported on their apical surface by an agar mounting method and impaled with microelectrodes via their basolateral membrane. This arrangement provided stable and long-lasting impalements of epithelial cells and yielded reliable membrane potentials and voltage divider ratios (R _a/R _b), where R _a and R _b are apical and basolateral membrane resistances respectively. The membrane potential under short-circuit conditions (V _sc) was –51.4±2.2 mV (n=59), while under open-circuit conditions apical membrane potential (V _a) and basolateral membrane potential (V _b) were –31.0±2.4 and 59.5±2.4 mV, respectively. This yields a well-shaped potential profile across the toad urinary bladder, where V _a is inversely related to the rate of transport, I _sc. Antidiuretic hormone (ADH) produced a hyperpolarisation of V _sc and V _b but had no significant effect on V _a. In addition, R _a/R _b was significantly increased by ADH (4.6±0.5 to 10.2±3.6). Calculation of individual membrane resistances following the addition of amiloride showed that ADH produced a parallel decrease in R _a and R _b membrane resistance, with the observed increase in R _a/R _b being due to a greater percentage decrease in R _b than in R _a. The ability of ADH to effect parallel changes in apical and basolateral membrane conductance helps to maintain a constant cellular volume despite an increase in transepithelial transport.     

Solution properties of poly(octadecyl methacrylate) in butyl acetate, 2. Semidilute solution

Semidilute solutions of a fraction of poly(octadecyl methacrylate) (PODMA) obtained by radical-initiated polymerization were investigated in the theta-solvent butyl acetate (BuAc) with static and dynamic light scattering (SLS, DLS, resp.) at four different temperatures between 13°C (near theta-temperature Θ) and 70°C. The molar mass of the investigated sample (PODMA 4) was 3,2 · 10⁶ g · mol^?1. A concentration region from dilute to 8 c^* was covered, where c^* = 1/[η] was taken as the coil overlap concentration, [η] denoting intrinsic viscosity. Above c = 3c^* the DLS correlation function exhibited bimodal behaviour at all temperatures. At these concentrations one finds two “apparent” molar masses, radii of gyration and diffusion coefficients for each concentration. The smaller apparent molar masses, smaller radii of gyration and larger diffusion coefficients correspond to characteristics of the transient network. The larger apparent molar masses, larger radii of gyration and smaller diffusion coefficients may be attributed to the formation of inhomogeneities in the semidilute solution.     

Influence of mepacrine,indomethacin, and nordihydroguaiaretic acid on the electrical properties of frog renal proximal tubules

In proximal renal tubules of the frog kidney, stimulation of sodium-coupled transport leads to a depolarization of the peritubular cell membrane, followed by partial repolarization. These alterations of the potential difference across the peritubular cell membrane (PD_pt,) are in part the result of altered peritubular potassium conductance. The repolarization has been blunted by the phospholipase A₂ inhibitor mepacrine, but not by the cyclooxygenase inhibitor indomethacin. In the present study the effect of mepacrine, indomethacin and the lipoxygenase inhibitor nordihydroguaiaretic acid on the electrical properties of proximal renal tubules has been tested in the presence and absence of stimulated sodium-coupled transport. In the absence of inhibitors, addition of 10 mmol/l phenylalanine to the luminal perfusate leads to a rapid depolarization and partial repolarization of the peritubular cell membrane, a decrease of the luminal cell membrane resistance (R _a) and a small increase of the cellular core resistance (R _c). Removal of phenylalanine leads to rapid hyperpolarization, increase of R _a and decline R _c. Mepacrine (100 ol/l) depolarizes the cell membrane and increases the peritubular cell membrane resistance (R _b), R _c and the intracellular pH. In the presence of mepacrine, phenylalanine leads to a sustained depolarization and a transient decrease of R _a. Indomethacin (10 mol/l) does not significantly modify PD_pt, the lumped resistance of both cell membranes (R _m) or R _c in the presence or absence of phenylalanine. Nordihydroguaiaretic acid (50 mol/l) does not alter significantly PD_pt, R _a, R _b or R _c prior to phenylalanine. However, in the presence of nordihydroguaiaretic acid, the repolarization upon phenylalanine is significantly more rapid, and the removal of phenylalanine in the presence of nordihydroguaiaretic acid is followed by a significant decrease of both, R _a and R _b. The observations point to an involvement of eicosanoids in the regulation of ion conductances during stimulation of sodium-coupled transport.     

The crystal structure and drawing-induced polymorphism in poly(aryl ether ketone)s, 2. Poly(ether ether ketone ketone), PEEKK

The crystal structure, morphology and polymorphism induced by uniaxial drawing of poly(ether ether ketone ketone) [PEEKK] have been studied by transmission electron microscopy (TEM), electron diffraction (ED) and wide angle X-ray diffraction (WAXD). On the basis of WAXD and ED patterns, the crystal structure of unoriented PEEKK is determined to have two-chain orthorhombic packing with unit cell parameters of a = 0.772 nm, b = 0.600 nm, c = 1.004 nm (form I). A stress-induced crystal modification (form II) is identified and found to possess a two-chain orthorhombic lattice with unit cell dimensions of a = 0.461 nm, b = 1.074 nm, c = 1.080 nm. The 7.5% increase in c-axis dimension for form II is attributed to an overextended chain conformation, arising from extensional deformation during uniaxial drawing and fixed “in-situ” through strain-induced crystallization. The average ether-ketone bridge bond angles in form II crystal are determined to be 148.9° by using standard bond lengths. The crystal morphology of PEEKK bears a great similarity to that of PEEK. The crystals grow in the form of spherulites and have the b-axis of unit cell radial. The effects of draw rate on strain-induced crystallization and induction of form II structure are also discussed.     

Associations with age at natural menopause in Blackfeet women

This study seeks to determine the age at natural menopause and factors that may predict that age for Blackfeet women living on the reservation in Montana. Data were obtained from a probability sample of 150 women. Rates of surgical menopause among women who had experienced menopause were similar to those found in NHANES I for U.S. women. Median age at natural menopause by the status quo method (51.2 years) was comparable to that determined for other populations. Within the group of women who already had experienced natural menopause, age at menopause was associated in bivariate models with age at menarche (b = ?0.83 ± 0.44 years, P = 0.07), household income (b = 1.85 ± 0.71 years, P = 0.01), “ever use” of birth control (b = 4.52 ± 1.58 years, P = 0.008), “ever use” of oral contraceptives (b = 5.48 ± 1.91 years, P = 0.007), current or recent unemployment (b = 4.75 ± 1.97 years, P = 0.02), having been breastfed (b = ?6.93 ± 2.67 years), and educational attainment (ANOVA by tertiles of menopause age, mean 10.0 ± 3.6 years of education for earliest, 13.0 ± 2.2 years for latest, P = 0.04). In multivariate models, “ever use” of oral contraceptives, household income, and age at menarche remained significant predictors of age at menopause (R² = 0.33–0.35, P = 0.002–0.004), with household income modifying the effect of age at menarche (analysis of joint effects). The findings are discussed in the context of cohort experiences, examining implications for both early and later‐life influences on menopause age. Am. J. Hum. Biol. 13:512–520, 2001. © 2001 Wiley‐Liss, Inc.     

Reproducibility of the exponential rise technique of CO2 rebreathing for measuring P vCO2 and C vCO2 to non-invasively estimate cardiac output during incremental, maximal treadmill exercise

The purpose of this study was to determine the reproducibility of the indirect Fick method for the measurement of mixed venous carbon dioxide partial pressure (P _vCO₂) and venous carbon dioxide content (C _vCO₂) for estimation of cardiac output (Q _c), using the exponential rise method of carbon dioxide rebreathing, during non-steady-state treadmill exercise. Ten healthy participants (eight female and two male) performed three incremental, maximal exercise treadmill tests to exhaustion within 1 week. Non-invasive Q _c measurements were evaluated at rest, during each 3-min stage, and at peak exercise, across three identical treadmill tests, using the exponential rise technique for measuring mixed venous PCO₂ and CCO₂ and estimating venous-arterio carbon dioxide content difference (C _v–aCO₂). Measurements were divided into measured or estimated variables [heart rate (HR), oxygen consumption (V̇O₂), volume of expired carbon dioxide (V̇CO₂), end-tidal carbon dioxide (P _ETCO₂), arterial carbon dioxide partial pressure (P _aCO₂), venous carbon dioxide partial pressure (P _vCO₂), and C _v–aCO₂] and cardiorespiratory variables derived from the measured variables [Q _c, stroke volume (V _s), and arteriovenous oxygen difference (C _a–vO₂)]. In general, the derived cardiorespiratory variables demonstrated acceptable (R=0.61) to high (R>0.80) reproducibility, especially at higher intensities and peak exercise. Measured variables, excluding P _aCO₂ and C _v–aCO₂, also demonstrated acceptable (R=0.6 to 0.79) to high reliability. The current study demonstrated acceptable to high reproducibility of the exponential rise indirect Fick method in measurement of mixed venous PCO₂ and CCO₂ for estimation of Q _c during incremental treadmill exercise testing, especially at high-intensity and peak exercise.     

Polymorphism of poly[bis(p-methoxyphenoxy)phosphazene]

Well characterized poly[bis(p-methoxyphenoxy)phosphazene] (PB(4-MeO)PP) has been investigated employing X-ray diffraction and differential scanning calorimetry (DSC). The DSC heating scan of the original PB(4-MeO)PP specimen exhibits one exotherm at 110°C and two endotherms at 106°C and 126°C, respectively. Only a single endotherm at 131°C appears on the second heating. X-ray diffraction measurements at elevated temperature reveal that PB(4-MeO)PP crystal is monoclinic (β-form) with unit cell dimensions a = 2,47 nm, b = 1,98 nm, c = 0,983 nm and y = 102° in the range of 106–126°C. Initially PB(4-MeO)PP specimens are observed to be orthorhombic (α-form) with a = 2,39 nm, b = 1,79 nm and c = 0,983 nm. The crystal transforms at 106°C and then changes into the β-form at 110°C according to DSC measurements. At 126°C the β-form crystal changes into a mesophase with an intermolecular distance of 1,44 nm at 150°C. The 3-dimensional orthorhombic γ-form with a = 2,21 nm, b = 2,01 nm and c = 0,963 nm is found at room temperature after specimens are cooled through T(1) = 126°C from the mesophase.     

Blood oxygenation level-dependent (BOLD) total and extravascular signal changes and ΔR2* in human visual cortex at 1.5, 3.0 and 7.0 T

The characterisation of the extravascular (EV) contribution to the blood oxygenation level‐dependent (BOLD) effect is important for understanding the spatial specificity of BOLD contrast and for modelling approaches that aim to extract quantitative metabolic parameters from the BOLD signal. Using bipolar crusher gradients, total (b = 0 s/mm²) and predominantly EV (b = 100 s/mm²) gradient echo BOLD ΔR₂* and signal changes (ΔS/S) in response to visual stimulation (flashing checkerboard; f = 8 Hz) were investigated sequentially (within < 3 h) at 1.5, 3.0 and 7.0 T in the same subgroup of healthy volunteers (n = 7) and at identical spatial resolutions (3.5 × 3.5 × 3.5 mm³). Total ΔR₂* (z‐score analysis) values were ?0.61 ± 0.10 s^?1 (1.5 T), ?0.74 ± 0.05 s^?1 (3.0 T) and ?1.37 ± 0.12 s^?1 (7.0 T), whereas EV ΔR₂* values were ?0.28 ± 0.07 s^?1 (1.5 T), ?0.52 ± 0.07 s^?1 (3.0 T) and ?1.25 ± 0.11 s^?1 (7.0 T). Although EV ΔR₂* increased linearly with field, as expected, it was found that EV ΔS/S increased less than linearly with field in a manner that varied with TE choice. Furthermore, unlike ΔR₂*, total and EV ΔS/S did not converge at 7.0 T. These trends were similar whether a z‐score analysis or occipital lobe‐based region‐of‐interest approach was used for voxel selection. These findings suggest that calibrated BOLD approaches may benefit from an EV ΔR₂* measurement as opposed to a ΔS/S measurement at a single TE. Copyright © 2010 John Wiley & Sons, Ltd.     

Estimation of inbreeding,kinship, genetic distances,and population structure from surnames: The island of Hvar,Croatia

The aim of this study was to estimate inbreeding, kinship, genetic distances, and population structure of the island of Hvar using surnames of the population from 10 villages. Total inbreeding on the island, estimated from the frequency of isonymous marriages, amounted to 0.0228. Total kinship (unreduced variance) of the entire island amounted to 0.0411, a value indicative of very isolated populations with accumulated kinship over time. The analysis of genetic relationships based on surnames among the villages did not reveal the division of the island's villages into two clusters, “eastern” and “western”, as was the case in previous studies when clustering was based on biological, biocultural, and sociocultural traits. In addition, kinship and genetic distances determined from surnames revealed a poor fit to an isolation by distance model (for kinship, R² = 14.6%, a = 0.1101, b = 0.3573; for genetic distances, R² = 0.0%, a = 0.5686, b = 121.52), which is in contrast to the results of previous analyses based on other traits. In order to estimate how closely parameters obtained from surnames represented real interpopulational distances, matrices of kinship and genetic distances between 10 villages (determined from surnames) were correlated to corresponding distance matrices based on migrational, sociocultural, anthropometric, physiological, dermatoglyphic, and genetic traits that were previously reported in the literature on the very same samples. The kinship matrix correlated poorly with other distance matrices, while the genetic distance matrix determined from surnames was in a good correlation with distance matrices based on linguistics (r = 0.65 for basic and r = 0.63 for cultural vocabulary), metacarpal bone dimensions (r = 0.54) and genetics (determined from systems of erythrocyte antigens and isoenzymes, r = 0.45). Am. J. Hum. Biol. 9:595–607, 1997. © 1997 Wiley-Liss, Inc.     

Structural study of compounds modelling elementary polymer units, 5. Molecular and crystal structures of C,C′-disubstituted o-carboranes

With the aim to determine the main structural characteristics of amorphous (branched and different-unit) polymers of the polyphenylene type, prepared by polycyclocondensation of carborane-containing mono- and diacetylaromatic compounds, an X-ray structural study of four model compounds was carried out, viz. of 1,2-bis[4-(4-acetylphenoxy)phenyl]-1,2-dicarba-closo-dodecaborane(12) ( 1 ) (triclinic crystals, a = 8,205 Å, b = 13,505 Å, c = 14,019 Å, α = 90,44°, β = 97,08°, γ = 97,24°, space group P1 , Z = 2, R = 0,045 for 2663 reflections), 1,2-bis(4-phenoxyphenyl)-1,2-dicarba-closo-dodecaborane(12) ( 2 ) (monoclinic crystals, a = 14,813 Å, b = 17,133 Å, c = 11,211 Å, β = 112,43°, space group P2₁/c, Z = 4, R = 0,066 for 3 286 reflections), 1,2-bis(4′-acetylbiphenyl-4-yl)-1,2-dicarba-closo-dodecaborane(12) ( 3 ) (orthorhombic crystals, at ?120°C a = 13,405 Å, b = 9,276 Å, c = 22,86 Å, space group Pnam, Z = 4 molecules on the m plane, R = 0,039 for 1 147 reflections), and 1,2-bis(4-acetylbenzyl)-1,2-dicarba-closo-dodecaborane(12) ( 4 ) (orthorhombic crystals, at ?120°C a = 22,03 Å, b = 26,23 Å, c = 8,026 Å, space group Fdd2, Z = 8 molecules lie on the two-fold axis, R = 0,051 for 577 reflections). The strained structure of the C,C′-o-diphenyl-substituted carboranyl fragment is established, the high conformational flexibility of 4-phenoxyphenyl linkages is confirmed and a tendency toward separate autoassociation of acetyl-containing polar groups and carborane nuclei is shown, with the autoassociation of polar groups completely suppressing that of carborane nuclei in case of conformational rigidity and shortness of the arylene linkages. These and other structural characteristics of the investigated model compounds and their crystals, in case they turn out to be characteristic also for the corresponding polymers and their precursors, should largely determine the structure and physico-chemical properties of their corresponding polymers.     

The molecular structures of 1,1-diphenylethyl methacrylate and triphenylmethyl methacrylate

The molecular structures of 1,1-diphenylethyl methacrylate (1,1-DPEMA) and triphenylmethyl methacrylate (TrMA) were determined by means of X-ray diffraction. 1,1-DPEMA: monoclinic, space group P2₁/a,a = 9,666(6), b = 19,94(2), c = 8,132(6) Å, β = 104,49(7)°, and Z = 4; TrMA: monoclinic, space group P2₁/n, a = 17,349(3), b = 9,487(2), c = 11,254(2) Å, β = 102,30(2)°, and Z = 4. Both structures were solved by the direct method and refined by the block-diagonal least-squares procedure to R = 0,175 and 0,056 for non-zero reflections, respectively. In both molecules, conformations about the C(1)? C(2) and C(1)? O(1) bonds are all synperiplanar and one of the two or three phenyl groups attached to the C(5) atom is in trans to the O(2).     

Comorbidity in Migraine with Functional Somatic Syndromes,Psychiatric Disorders and Inflammatory Diseases: A Matter of Central Sensitization?

To approach the questions as to why migraine appears to be associated with functional somatic syndromes (FSSs) and whether central sensitization may be an underlying mechanism, the present study investigated (a) comorbidity with diagnoses of three FSSs, three psychiatric disorders, and three inflammatory diseases, (b) degree of mental health problems (stress, burnout, anxiety, depression and somatization), and (c) prevalence of ten cognitive/affective and nine airway symptoms in persons with migraine in the general population. From a randomized and stratified Swedish adult sample, questionnaire data were analyzed from 151 individuals with a diagnosis of migraine and 3,255 without migraine. The results showed (a) significant comorbidity in migraine with all FSSs, psychiatric disorders and inflammatory diseases, (b) significantly elevated scores on stress, burnout, anxiety, depression, and somatization, and (c) relatively high prevalence rates on almost all symptoms. Taken together, the results motivate future study of central sensitization as a mechanism underlying migraine.     

The molecular structure of diphenylmethyl methacrylate

The molecular structure of diphenylmethyl methacrylate has been determined by means of X-ray diffraction. Crystals are monoclinic, space group C2/c, a = 29, 177 (2), b = 6,017(1), c = 16,110(1) Å, β = 96,840(5)°, and Z = 8. The structure was solved by the direct method and refined by the block-diagonal least-squares procedure to R = 0,071 (R_w = 0,091) for 1768 measured reflections. The molecule has an antiperiplanar conformation as to the C?C and C?O double bonds about the C(1)? C(2) bond and a synperiplanar conformation as to the C?O and C? O bonds about C(1)? O(1).     

Novel structural and thermotropic behavior of poly(diphenylphosphazene)

Poly(diphenylphosphazene) (PDPhP) was synthesized by a reaction of 2,2,2-trifluoroethyl diphenylphosphinite with trimethylsilyl azide. Characteristics of the polymer exhibit a marked molecular weight dependency. DSC measurements showed that the PDPhP undergoes a mesophase T(1) type transition in the range 180 ～ 190°C and another at 240 ～ 255°C depending upon the molecular weights of the polymers. Upon heating and cooling through T(1) the higher molecular weight PDPhP transforms to a 3D orthorhombic (γ-form) with a = 1,99 nm, b = 1,05 nm and c = 0,995 nm from its original form (α-form) in which a = 1,01 nm, b = 1,01 nm and γ = 101° after passing through the disordered mesophase (δ-form). Another 3D form (β-form) with c = 1,25 nm is formed from the lower molecular weight PDPhP after heat treatment of the 2D phase (δ-form) that is obtained by quenching the specimens into ice-water (4°C) from above T(1). The conditions for the formation of the β-form depend strongly on the polymer molecular weight and its history. Lath-shaped crystals were grown from dilute dichlorobenzene solution by adding p-xylene (a non-solvent). Electron diffraction patterns of solution grown PDPhP specimens exhibit unusual hexatic triple reflections associated with the mesophase. (100) twinning due to the thermal history of the specimens has been established. A complex (multistep) heat treatment process was required to elucidate the transformation behavior in PDPhP.     

Cerebral sodium/angiotensin interaction studied by RIA-determination of urinary arginine vasopressin in the hydrated goat

Radioimmunoassay determination of urinary arginine vasopressin (AVP) was employed to study quantitatively cerebral Na⁺/angiotensin II (A II) interaction in the hydrated goat. The solutions infused for 30 min at 0.02 ml/min into the lateral cerebral ventricle were: a) Hypertonic (0.25 M) NaCl, b) A II (0.3 ng/kg min) in isotonic (0.15 M) NaCl, and c) A II (dose as in b) in 0.25 M NaCl. The mean amounts of AVP detected in the urine in response to the various infusions were: a) 2.8 ng, b) 3.6 ng, and c) 13.3 ng. Thus, the A II/NaCl stimulation induced a detected renal excretion of AVP that was two times as large as the sum of the effects recorded in response to the separate stimuli. Infusion c) invariably induced a pronounced, long-lasting inhibition of the water diuresis, intense thirst, and natriuresis. The corresponding effects of infusions a) and b) were much weaker and, as regards thirst and natriuresis, inconsistent. The determinations of renal AVP excretion provide additional, and rather direct evidence for the concept of a synergistic action of elevated cerebrospinal fluid [Na⁺] and A II as concerns cerebral control of fluid balance. With regard to this kind of interaction, the observed dipsogenic and natriuretic effects mainly confirm earlier observations.