I1 I2 Research Articles

The Cohomological Dimension of a Resultant Variety in Prime Characteristicp

Ž . 2 2 Ž . Let F s, t s X s q 2 X st q X t 1 F i F 3 be a collection of bii i0 i1 i2 nary quadratic forms with indeterminate coefficients over a field k and let w x R s k X . The aim of this paper is to compute the cohomoi, j 1F iF 3, 0 F jF 2 logical dimension of the ideal I ; R generated by the following Sylvester Ž . Ž . Ž . Ž . resultants: Res F , F , Res F , F , Res F , F , and Res F q F , F . 1 2 1 3 2 3 1 2 3 The closed points of the affine variety defined by I correspond to coefficients of the three forms having a common zero. Thus, in the w x Ž terminology of L1 , I is a resultant system for F , F , and F compare 1 2 3 w x. with Theorem 1.b in L1 . In general, if F , . . . , F are binary forms of 1 s degrees d G d G ??? G d , one can show that a resultant system is 1 2 s s Ž . Ž w x. generated by at least 1 q Ý 1 q d elements Theorem 1 in L1 and ts3 t one would like to know if this lower bound is sharp. In our case, where s s 3 and d s d s d s 2, the question is whether 1 2 3 4Ž . I can be generated by three elements. This would imply that H R s 0 I and this is the motivation behind the main result of this paper. 4Ž . It turns out that it is possible to show that H R s 0 working in the I Ž . subring of joint invariants of G s GL 2, k acting on R via change of Ž . variables in s, t . This calculation is based on some recent results by Lyubeznik on F-modules, which include an algorithm for deciding whether local cohomology modules over regular rings of prime characteristic p vanish. To the best of the author’s knowledge, Theorem 9 in this paper is the first application of this algorithm. Yan has recently produced a 4Ž . w x topological argument showing that H R vanishes in characteristic 0 Y . I

Asymmetrical distribution of G proteins in syncytiotrophoblastic brush-border and basal-plasma membranes of human term placenta

In human placental syncytiotrophoblast brush-border (BBM, facing the mother) and basal-plasma membranes (BPM, facing to fetus) we have recently demonstrated the presence of calcaemic hormone-specific receptors for parathyroid hormone and calcitonin, which could be implicated in calcium transport from the mother to the fetus. It is well recognized that signal transducing G proteins (guanosine nucleotide-binding proteins) can associate with various transmembrane receptors and effector proteins, and regulate a variety of second-messenger systems and ion channels. In this present paper, we investigated the presence of a variety of α and β subunits of G proteins in both syncytiotrophoblast, BBM and BPM by Western blot technique. For the first time, we were able to demonstrate the presence of G proteins in the bipolar syncytiotrophoblast membranes, which were evaluated by immunoblotting using affinity purified antiserum raised against the α subunits of G i1, G i1 i2 , G i3, G o, G q, G s, G z and against the β subunits. In BBM, we identified the α subunits of G i1, G i3, G o, G q, G s (42, 46 kDa), G z and β subunits. The same α subunits of G proteins were found in BPM, although α subunits of G i3, G q, G s (46 kDa) were located predominantly in the BBM, and the α subunit of G o was found preferentially in BPM. Moreover, in BBM and BPM, a purified antisera raised against the α subunits of G i1 and G s, detected a 105 kDa protein and a 67 kDa protein, respectively. Interestingly, the 67 kDa protein was preferentially located in BBM, and none of these proteins were detectable in membranes prepared from brain (control). The asymmetrical distribution of the α subunits of G proteins among the two different placental bipolar membranes might reflect the very specialized function of these syncytiotrophoblast membranes in ions and nutrients transport from the mother to the fetus.

Potassium Dibenzo-18-crown-6 Triiodide

In (1,4,7,10,13,16-hexaoxa-2,3: 11,12-dibenzocyclooctadeca-2,11-diene)potassium triiodide, [K(C20H24O6)]I3, the K+ ion is coordinated to the six ether O donors of the macrocycle [K—O 2.716 (4)–2.779 (4) A] and to atom I3 at a distance of 3.6002 (13) A; I1–I2 is 2.8741 (7) and I2–I3 2.9838 (7) A. Pairs of symmetry-related [K(dibenzo-18-crown-6)]I3 molecules aggregate, with an unusually short distance of 3.184 (3) A between the K+ ion and the centroid of one of the benzo groups.

A proof of the Benjamin-Feir instability

The existence and linear stability problem for the Stokes periodic wavetrain on fluids of finite depth is formulated in terms of the spatial and temporal Hamiltonian structure of the water-wave problem. A proof, within the Hamiltonian framework, of instability of the Stokes periodic wavetrain is presented. A Hamiltonian center-manifold analysis reduces the linear stability problem to an ordinary differential eigenvalue problem on ℝ4. A projection of the reduced stability problem onto the tangent space of the 2-manifold of periodic Stokes waves is used to prove the existence of a dispersion relation Λ(λ,σ, I 1, I 2)=0 where λ e ℂ is the stability exponent for the Stokes wave with amplitude I 1 and mass flux I 2 and σ is the “sideband’ or spatial exponent. A rigorous analysis of the dispersion relation proves the result, first discovered in the 1960's, that the Stokes gravity wavetrain of sufficiently small amplitude is unstable for F e (0,F0) where F 0 ≈ 0.8 and F is the Froude number.

Increased concentrations of proteins Gi1 and Gi2 in adipocytes from aged rats alter the sensitivity of adenylyl cyclase to inhibitory and stimulatory agonists

We used a series of antipeptide antisera to estimate the relative amounts of G proteins in adipocytes from young lean versus aged obese Sprague-Dawley rats. Western blots were analyzed using antisera that recognize (1) the alpha-subunits of Gi1 and Gi2 (serum SG1), (2) the alpha-subunit of Gi3 (serum I3B) (3) two forms of the alpha-subunit of Gs (serum CS1), and (4) forms of the beta-subunits common to all the G proteins (serum BN2). Adipocyte membranes from aged rats contained approximately fivefold to sixfold more alpha i1 and alpha i2 than those from young rats, but almost equal amounts of alpha i3. Membranes from aged rats had a modestly higher (50%) amount of a 43-kd and normal amounts of a 47-kd form of alpha s. Membranes from old rats also had approximately a threefold higher amount of beta-subunits, consistent with increased concentrations of some of the G proteins but not others. Finally, the functional consequences of these differences in G proteins was investigated by measuring the effect of N6-phenylisopropyl adenosine ([PIA] an A1-adenosine receptor agonist) and isoproterenol on adenylyl cyclase activity. Adenylyl cyclase was more sensitive to inhibition by PIA in membranes from old rats than from young rats, but was less sensitive to stimulation by isoproterenol, suggesting that the differences we observed are functionally active G proteins. These findings may account for the altered sensitivity of adipocytes from old rats to antilipolytic and lipolytic hormones.

Stimulatory and inhibitory guanine‐nucleotide‐binding regulatory protein involvement in stimulation of arachidonic‐acid release by N‐formyl‐methionyl‐leucyl‐phenylalanine and platelet‐activating factor from guinea‐pig alveolar macrophages

The involvement of guanine-nucleotide-binding regulatory proteins (G proteins) in the regulation of arachidonic-acid release induced by N-formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe) or platelet-activating factor (PAF) was examined in guinea-pig alveolar macrophages. We report that maximal release of arachidonic acid in permeabilized cells requires the simultaneous addition of the agonist (fMet-Leu-Phe or PAF) and of GTP (or GTP[S]). Prior treatment of cells with increasing concentrations of pertussis toxin induces a parallel decrease of arachidonic-acid release and of the labeling of a 40-kDa protein in membranes incubated with [32P]NAD and pertussis toxin. fMet-Leu-Phe, but not PAF, allows the ADP-ribosylation of a 40-KDa protein by cholera toxin in the presence of Mg2+. This effect is prevented by guanyl nucleotides and by prior treatment with pertussis toxin. The 40-kDa protein ADP-ribosylated seems to be alpha i1 and/or alpha i2. Stimulation of GTPase activity by fMet-Leu-Phe and PAF has the same amplitude and is completely inhibited by pertussis toxin, but only in part by cholera toxin. Prior treatment of alveolar macrophages with cholera toxin, which ADP-ribosylates Gs, inhibits PAF-stimulated and fMet-Leu-Phe-stimulated arachidonic-acid release to the same extent, via a cAMP-protein-kinase-A cascade. The decreased responsiveness of alveolar macrophages previously treated with cholera toxin to fMet-Leu-Phe and PAF is associated with a strong increase of in-vitro [32P]NAD labeling of Gi proteins either by pertussis or by cholera toxin. This effect is mimicked by prior treatment of the cells with dibutyryl cAMP and okadaic acid, a protein-phosphatase inhibitor, suggesting the involvement of protein-kinase A in this process. In conclusion, our results demonstrate that fMet-Leu-Phe and PAF receptors interact differently with Gi1/2 proteins in guinea-pig alveolar macrophages. Gi1/2 proteins are a possible target of the cross-regulation of arachidonic-acid release by a Gs-mediated pathway.

Gi down-regulation as a mechanism for heterologous desensitization in adipocytes.

Prolonged incubation of rat adipocytes with (-)N6-phenylisopropyl adenosine (PIA) (an A1 adenosine receptor agonist) leads to down-regulation of each of the three subtypes of Gi (Green, A., Johnson, J. L., and Milligan, G. (1990) J. Biol. Chem. 265, 5206-5210). To determine whether other inhibitors of adenylylcyclase would have similar actions, we incubated adipocytes in primary culture with PIA, prostaglandin E1 (PGE1), or nicotinic acid. After various times cells were homogenized, and crude membrane fractions were analyzed on Western blots using antipeptide antisera to alpha- and beta-subunits of G-proteins (SG1 (which binds to alpha i1 and alpha i2), I3B (which binds to alpha i3), BN2 (binds to beta-subunits) and CS1 (recognizes forms of alpha s)). PIA and PGE1 caused approximately 90% down-regulation of alpha i1 and alpha i3, and about 50% loss of alpha i2 and beta-subunits. In contrast, nicotinic acid at concentrations up to 1 mM had no effect on levels of any of these Gi subtypes. None of the compounds altered levels of either a 43- or 47-kDa form of alpha s. PIA caused about a 50% decrease in binding of [3H]DPCPX (an A1 adenosine receptor antagonist), indicating adenosine receptor down-regulation; however, neither PGE1 nor nicotinic acid treatment altered [3H]DPCPX binding. None of the treatments affected the activity of adenylylcyclase when measured in the presence of 100 microM forskolin and 10 mM Mn2+, indicating that the catalytic subunit of adenylylcyclase is not altered. To determine whether Gi down-regulation results in heterologous desensitization, we incubated adipocytes with maximally effective concentrations of PIA (300 nM), PGE1 (3 microM), or nicotinic acid (1 mM) for 4 days. The cells were then washed and incubated for an additional 30 min with various concentrations of these compounds to determine their ability to inhibit lipolysis. PIA caused a (marked) decrease in the sensitivity of the cells to both PIA and PGE1, thus indicating heterologous desensitization. Similarly, PGE1 decreased the sensitivity of the cells to both PGE1 and PIA, again demonstrating heterologous desensitization. In contrast, prolonged incubation with nicotinic acid decreased the sensitivity of the cells to nicotinic acid but had no effect on the sensitivity of the cells to PIA. Adenylylcyclase in membranes from PGE1-treated cells showed decreased sensitivity to inhibition by PIA. In contrast, adenylylcyclase showed normal sensitivity to PIA in membranes from nicotinic acid-treated cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Anisotropic pitch-based carbon fibers—carbonization and graphitization (radial-with-wedge i1 and radial i2 types)

Anisotropie pitch-based fibers (radial-with-wedge I1 and radial types I2) were carbonized and graphitized. The initial pitch B was a mixture of a gel 2.3 (edge-to-edge type) and of an isotropic phase-1 rich in Brooks and Taylor mesophase spheres. The continuous part 2 of the gel is a network of edge-toedge associated carbon BSU (micelles) including microdroplets 3 of the finely divided part. The latter has an orthogonal orientation of its carbon layers, relative to the former. During heat treatment, the nanotexture changes follow those of other carbons, whereas the texture undergoes minor changes. The fibrils 1 yield a microporous non-graphitizing carbon. The gel 2.3 yields zig-zag continuous layers. The fibers of the radial-with-wedge and the radial types have the same ability to graphitize.

Regulation of guanine nucleotide binding regulatory proteins in cultured adrenal cells by adrenocorticotropin and angiotensin-II.

In addition to their steroidogenic effect on cultured bovine adrenal fasciculata cells ACTH and angiotensin-II (A-II) have a long term effect on the ability of these cells to respond to subsequent hormonal stimulation. The present work explores the effects of a 72-h pretreatment of adrenal cells with both hormones on the first steps of the mechanism of action of ACTH and A-II and on the amounts of the alpha-subunits of guanine nucleotide binding proteins Gs and Gi. ACTH but not A-II increased acute ACTH or cholera toxin-induced cAMP production. Moreover, ACTH but not A-II enhanced the amount of alpha S protein evaluated by cholera toxin ADP ribosylation, whereas both hormones elevated immunoblotted alpha S. Both hormones increased A-II induced phosphoinositide breakdown and Ca2+ uptake without modification of the A-II potentiating effect on ACTH-induced cAMP production. Treatment of cells with pertussis toxin (PT, 0.5 micrograms/ml) for the last 24 h reduced by 27% the A-II induced phosphoinositide breakdown in A-II pretreated cells but had no significant effect in ACTH-pretreated cells. No effect of PT was observed on A-II induced Ca2+ uptake or on its potentiating action on ACTH-induced cAMP production in ACTH as well as A-II-pretreated cells. Moreover, both hormones increased Gi proteins (40-41 kDa) evaluated by PT ADP ribosylation. Immunoblot analysis revealed that ACTH preferentially enhanced alpha i3, whereas the stimulatory effect of A-II was more marked on alpha i1 and alpha i2. These results indicate that in bovine adrenal fasciculata cells, peptide hormones settle target cell responsiveness not only by regulating the membrane-bound receptors, but also by modulating the level of G proteins coupling these receptors to the intracellular signals.

Clonal variation of adenylyl cyclase activity in a rat tumor cell line caused by change in G protein‐catalytic unit interaction

Two subclones of the rat XC cell line characterized by different morphology exhibited quite different adenylyl cyclase responses upon various stimulations. Upon treatment with cholera toxin, clone RK1 accumulated a high level of intracellular cAMP thereby changing its polygonal morphology to an elongated morphology, while the other clone, LK1, with a fibroblastic morphology, failed to increase the intracellular cAMP and remained morphologically unchanged. When membrane fractions derived from these two clones were stimulated with 10 microM forskolin, 10 microM GTP gamma S, or 10 mM NaF, five- to 20-fold more cAMP was accumulated in RK1-derived membranes than in LK1-derived membranes. With the same membrane fractions, upon treatment with Mn(+)+, which directly stimulates the catalytic unit, a high level of cAMP was accumulated both in RK1 and LK1, indicating that the catalytic function inducible by Mn(+)+ was similar in both clones. There was no significant difference in the level of expression of G protein alpha 2, alpha i (at least alpha i1 and alpha i2), and beta subunits between LK1 and RK1. Cholate extracts of the membrane proteins of LK1 and RK1 reconstituted the adenylyl cyclase activity of the cyc- variant of S49 lymphoma cells to the same level. Therefore, it is inferred that the defect in LK1 resides in the interaction of stimulatory G proteins and the actual catalyst.

Rearrangements of chromatin structure during spermatogenesis of squid.

A stepwise replacement of somatic histones on sperm-specific proteins (we have termed them illexines I1 and I2) is found to occur during spermatogenesis of squid Illex argentinus [Kadura, S.N. and Khrapunov, S.N. (1988) Eur. J. Biochem. 175, 603-607]. The chromatin from nuclei of squid immature testes has a nucleosomal DNA repeat which corresponds to the nucleosomal repeat of calf thymus chromatin (195 +/- 5 bp). As spermatozoa become mature and illexine I2 accumulates in the chromatin, the nucleosomal structure of the latter disappears and chromatin compacting takes place. The chromatin DNA from squid spermatozoa is highly resistant to micrococcal nuclease action. Spectrophotometry and spectrofluorimetry were to establish that neither illexine I1 nor illexine I2 forms a globular structure in solution under any conditions studied. Illexine I2 (approx. 7 kDa) shows a high affinity to DNA and remains bound to it under conditions when complexes of illexine I1 (approx. 9 kDa) and salmine (approx. 4.5 kDa) with DNA completely dissociate. This fact, allowing for a similar content (about 75%) of arginine in illexine I2 and salmine, suggests high clustering of arginine residues in the composition of illexine I2. It is suggested that the initial stage of histone substitution with illexine I1, which has a more moderate affinity to DNA than illexine I2, prepares chromatin for the formation of a highly packed structure by illexine I2 during squid spermatogenesis.

Polymorphisms in eruption sequence of permanent teeth in American children

This study provides basic descriptive data on the frequency of pairwise eruption sequences ascertained in cross-sectional examination of 6,000 black and white American children in the Ten State Nutritional Survey of 1968-1970. All sex and race groups share a distinct pattern of sequence polymorphisms in terms of location, number, and level. Teeth in eruption phase I (M1, I1, I2) rarely reverse in sequence with those in phase II (C, P1, P2, and M2). Five sequences have variants that appear at greater than or equal to 20% in all groups, with M1I1 vs. I1M1 approaching maximum polymorphic values of 50%/50%. The traditional notation for eruption sequences can be modified to reflect these important variants, giving the sequence M1 I1 I2 [P1 C P2] M2 for the maxilla and [M1 I1] I2 [C P1] [P2 M2] for the mandible. The location of major polymorphisms is explicable by close timing of teeth within phase I and, separately, teeth within phase II eruption. However, strong integration of development of physically adjacent teeth apparently acts to reduce substantially the number of sequence reversals. The Ten State Survey data provide a sound descriptive basis for two populations, yet precise comparative data are available for few other human groups or primate species.

Discrimination of the isozymes of human placental hexosaminidase by kinetic parameter estimation.

Human placental beta-N-acetylhexosaminidase (EC 3.2.1.52) (HEX) is a lysosomal glycosyl hydrolase with an acidic pH optimum. Four isozymes (HEX B, HEX I1, HEX I2, and HEX A) have been isolated from human placenta. HEX BA derived from the subunit rearrangement of HEX A was also prepared. To determine if the isozymes of hexosaminidase differ in their kinetic parameters, the conditions for 4-methylumbelliferyl-beta-D-N-acetylglucosaminide hydrolysis were optimized for each isozyme. The Km values were essentially similar and varied from 0.64 +/- 0.06 for HEX BA to 0.85 +/- 0.13 for HEX I1. The Vmax values were similar only for HEX I1 (3.90 +/- 0.28 kat kg-1) and HEX I2 (4.40 +/- 0.17). Vmax values varied significantly between HEX A (9.68 +/- 0.52), HEX B (8.00 +/- 0.75), HEX BA (4.81 +/- 0.17), and the HEX I values.

Single Na channels in mouse neuroblastoma cell membrane. Indications for two open states.

Single sodium channel currents were studied in mouse neuroblastoma cells. Channel conductance (gamma) was 11.6 +/- 3.4 pS at 6-8 degrees C. Unitary current amplitudes and channel activity increased with increasing temperature. The Arrhenius plot of the conductance was linear between 5 and 35 degrees C with an activation enthalpy of 27.1 kJ/mole (Q10 = 1.28). Amplitude distributions were fitted by the sum of two Gaussian functions indicating the presence of two different single channel amplitudes: smaller i1 and larger i2. The relative probability of appearance of i1, which has a shorter mean open time, was higher during the early phase of depolarization (t less than 16 ms). The open time histograms, inactivating phase of macroscopic currents and delay time histograms were fitted by the sum of two exponentials. The distinct kinetic and steady-state parameters reflect two open states of sodium channels.

Ionisation of He atoms by H+, He2+and Li3+nuclei

The cross sections, sigma i1 and sigma i2, of single and double ionisation of He atoms by H+, He2+, and Li3+ nuclei with energies ranging from 0.01 to 5 MeV amu-1 are calculated in the independent-electron approximation. The calculations are made for three versions of the probabilities of one-electron transitions to the continuum. The double ionisation of He by nuclei with energies E/A approximately 0.1-Z2 meV amu-1 is mainly due to the independent interaction of each atomic electron with the bombarding nucleus. The values of sigma i1 for all nuclei with E/A>or=0.2MeV amu-1 and of sigma i2 for He2+ and Li3+ nuclei with E/A=0.2-0.5 MeV amu-1 calculated in one of the versions are found to agree with the experimental values. The calculated values of sigma i2 for protons with E=0.2-0.7 MeV and 1.5-4 MeV are respectively higher and lower than the experimental values because the authors calculations were made neglecting the electron correlations.

On the Space of Stress Invariants

The representation of stress through its three invariants I1,I2, and I3 has been examined. It has been shown that all possible states of stress are mapped into a connected region of the space of stress invariants that is bounded by two surfaces which meet in a cusp on a curve which corresponds to states of isotropic stress. All other states of stress for which two principal stresses are equal, lie on this surface. The I1 axis corresponds to one-dimensional states of stress. Two-dimensional stresses are represented by a connected region of the I1–I2 plane. The negative half of the I2 axis corresponds to pure shear. The positive half of the I2 axis, and the I3 axis, do not correspond to any states of stress. The representation of yield surfaces in this space has also been considered.

Ages of eruption of the permanent teeth in Kenyan African and asian children.

Mean ages of eruption of the permanent teeth (except 3rd molars) in African and Asian children were derived from a cross-sectional study of 2847 children aged 4-14 years, in selected nursery and primary schools in Nairobi, Kenya. Except for the premolars, the mandibular teeth erupted earlier than the maxillary ones in both races. The mandibular incisors and canines erupted earlier by 0.9-1.1 yr in Africans and 0.6-0.8 yr in Asians, and the molar by 0.2-0.4 yr in both races. The maxillary premolars were ahead of mandibular premolars by 0.1-0.2 yr in both races. The females were ahead of males in both races. Compared with the Asians, the African permanent teeth erupted earlier by 0.2-0.7 yr. The most frequent order of eruption in Africans is Mand I1, Mand M1, Max M1, Mand I2, and Max I1 between 5-7 years, while in the Asians the most frequent order is Mand M1, Mand I1, or Max M1, Max I1 and Mand I2 between 6-8 years. The incidence of Cusp of Carabelli in Africans and Asians is about 19-25%.

Polymerization of acrylamide with persulfate–thiomalic acid initiator

AbstractThe redox system of potassium persulfate–thiomalic acid (I1–I2) was used to initiate the polymerization of acrylamide (M) in aqueous medium. For 20–30% conversion the rate equation is where Rp is the rate of polymerization. Activation energy is 8.34 kcal deg−1 mole−1 in the investigated range of temperature 25–45°C. Mn is directly proportional to [M] and inversely to [I1]. The range of concentrations for which these observations hold at 35°C and pH 4.2 are [I1] = (1.0–3.0) × 10−3, [I2] = (3.0–7.5) × 10−3, and [M] = 5.0 × 10−2–3.0 × 10−1 mole/liter.

Tooth Eruption Sequence in Fossil and Recent Man

THE sequence of eruption of the permanent teeth has been used as a measure of the biological distance between early and recent man. Schultz1 gives the order M1 I1 I2 M2 (P P) (C M3) for fossil man, as contrasted with (I1 M1) I2 (P C P) M2 M3 for recent whites, a distinction in which Osman-Hill2 concurs. Broom and Robinson3 have further used the sequence I1 M1 I2 (C P1) M2 P2 M3 as a taxonomic criterion for Paranthropus, holding that this sequence “agrees closely with that of modern man”.

Internal and External Bisectors, and an Example of Continuity

I. To draw quickly a good figure of A, B, C, I, I1, I2, I3, etc. Draw a circle, and a chord BC. Mark L the middle point of the arc below BC by the “engineer's method,” viz., with B as centre and a radius as near BL as can be judged by the eye, make a mark on the arc, with C as centre and the same radius make another mark on the arc, judge by the eye the middle point of the arc between these marks; this is L. With centre L, radius LB or LC, describe a circle: I and I1 lie on this circle. Mark M the middle point of the arc above BC. With centre M, radius MB or MC, describe a circle: I2 and I3 lie on this circle. Now I and I1 lie on AL; I2 and I3 on AM. Mark A on the first circle, so that MA lies conveniently on the paper. The various collinearities and perpendicularities justify the figure to the eye; the properties of the mid-points of II1 etc., I2T3, etc., and the loci of I, I1 I2 I3 as A varies, are emphasised.