Defined chemically cross-linked oligomers of human C-reactive protein: characterization and reactivity with the complement system

Chemically cross-linked C-reactive protein (CRP) oligomers were prepared and characterized, and C1q binding and C activation were investigated. Purified human CRP was polymerized in the presence of both non-cleavable and cleavable cross-linking agents and further separated by Superose 12 analytical FPLC column chromatography into fractions of 110 KDa (pentameric monomers), 220 KDa (dimers) and 330 KDa (trimers); virtually no larger oligomers were formed under a variety of experimental conditions. CRP subunits were cross-linked both within and between CRP pentamers. CRP trimers retained native CRP antigenicity without expression of neo-CRP epitopes. CRP trimers showed maximal binding and CRP dimers showed partial binding of solid phase C1q while CRP monomers bound virtually no C1q at all; CRP trimers also bound to fluid phase C1q. Binding was Ca++ independent and increased as the ionic strength or pH were lowered, characteristics comparable to binding of aggregated IgG to C1q; it was not inhibited by phosphorylcholine. CRP trimers consumed total C, C1 and C2 haemolytic activities upon incubation in fresh human serum, but much less efficiently than did CRP-protamine complexes or Agg-IgG. CRP trimers failed to deplete alternative C pathway haemolytic activity at all. The stable, chemically defined CRP oligomers described in this report, which bind C1q efficiently but display poor ability to activate the classical C pathway in the absence of an appropriate ligand, should be valuable in further studies of the interactions between CRP and the C system.

Inhibitory regulation of serum factor(s)-caused ornithine decarboxylase induction by the protein kinase C system in A431 human epidermoid carcinoma cells

Replacement of the culture medium with fresh medium containing 10% fetal calf serum caused ornithine decarboxylase (ODC) induction in A431 human epidermoid carcinoma cells. Two peaks of ODC activity were observed at 5 and 14 hr after the medium replacement. The peak activity observed at 5 hr was more prominent than that at 14 hr. The first peak of ODC induction was suppressed by a potent protein kinase C activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), in a concentration-dependent manner. The second peak, however, was not suppressed by TPA. Other potent protein kinase C activators, such as mezerein and 12-O-retinoylphorbol-13-acetate, also suppressed the first peak of ODC induction. Synthetic diacylglycerols, 1,2-dioctanoyl-sn-glycerol and 1-oleoyl-2-acetylglycerol, did not inhibit the serum factor(s)-caused ODC induction. Phorbol-13-acetate, an inactive phorbol ester, also failed to inhibit the ODC induction. The growth of A431 cells was slightly suppressed by TPA. In protein kinase C down-regulated cells, TPA failed to inhibit the serum factor(s)-caused ODC induction. These results suggest that the serum factor(s)-caused ODC induction in A431 cells is negatively regulated by the protein kinase C system, which may not be activated by exogenous diacylglycerols.

Normalization of force generated by canine airway smooth muscles

A variety of normalizations have been employed to compare maximal isometric force (Po) produced by smooth muscles at different locations and stages of maturation. Because these procedures have not always been based on rigorous principles, confusion has resulted. To obtain a less ambiguous index of force production, we measured in vitro Po from mongrel canine tracheal (TSM) and bronchial (BSM) smooth muscle with an electromagnetic lever and normalized it to force per unit cross-sectional area of whole tissue (tissue stress), to force per unit cross-sectional area of muscle in the cross section of total tissue (muscle stress), and to force per fractional unit of myosin in the tissue cross section (myosin stress). Proportion of myosin in cross-sectional area of tissue was deduced from data obtained by sodium dodecyl sulfate gel electrophoresis of crude muscle extracts. For TSM, tissue stress was 1.499 X 10(5) N/m2 +/- 0.1 (SE), whereas it was only 0.351 X 10(5) N/m2 +/- 0.05 (SE) for BSM, representing a 4.27-fold difference (P less than 0.01). There was a 1.60-fold difference (P less than 0.05) in muscle stress, which was correlated to the morphometric finding that 79 +/- 1.4% (SE) of the tracheal strip cross section was muscle, whereas only 30 +/- 1.0% (SE) of bronchial tissue was occupied by muscle. Average myosin content was the same in smooth muscle cells of TSM and BSM, indicating that total amount of myosin in tissue cross sections was essentially a function of proportional area of muscle cells in total tissue cross sections.(ABSTRACT TRUNCATED AT 250 WORDS)

Involvement of prostaglandin E2 in the tumor promoter phorbol ester-caused increase in epidermal cholesterol sulfotransferase activity

A single topical application of 10 nmol TPA to mouse skin caused an increase in epidermal cholesterol sulfotransferase activity, a squamous differentiation associated enzyme. A topical application of indomethacin (1.2 mumol), a cyclooxygenase inhibitor, 10 min before TPA application markedly inhibited the above TPA action. Concurrent application of prostaglandin E2 (PGE2) with indomethacin reversed the inhibitory effect of indomethacin. PGF2 alpha, however, failed to reverse the inhibition caused by indomethacin. Both indomethacin and PGE2 alone did not change epidermal cholesterol sulfotransferase activity significantly. These results indicate that PGE2 plays a significant role in the mechanism of TPA-caused increase in cholesterol sulfotransferase activity in mouse epidermis.

Survival of cardiac allograft in highly sensitized and nonsensitized rats treated with FK506

The effect of FK506 was studied in sensitized and nonsensitized recipients using a rat cardiac allograft model. Heart grafts from Male ACI rats were heterotopically transplanted to Male LEW rats. The sensitized rat models were established by using donor type blood, admixed with immunoadjuvant (Adjuvant Complete Freund), seven days prior to transplantation. FK506 was administrated from day 0 to day 14 posttransplantation. The results showed that FK506 could prolong allograft survival in both sensitized and nonsensitized rat recipients in a dose-dependent manner, although, the dose required in sensitized recipients was higher than in nonsensitized recipients. The minimal effective dose of FK506 was 0.32 mg/kg/day in sensitized recipients and 0.1 mg/kg/day in nonsensitized recipients.

In vitro kinetic study of the immunosuppressive effect of deoxymethylspergualin on human peripheral blood mononuclear cells

The immunosuppressive mechanism of Deoxymethylspergualin (MeDSG) was investigated in human subjects by in vitro assay. In an allogeneic mixed lymphocyte reaction (MLR), MeDSG was added at different times. A moderate immunosuppressive activity against allogeneic blastogenesis was seen even when MeDSG was added on the 4th day from the initiation of culture. In the cell-mediated lymphocytolysis (CML) assay, MeDSG was added to bulk MLR in CML in the same manner. For the strong suppression of CML, however, MeDSG should be added to bulk MLR within 2 days from the initiation of culture. There was a difference in immunosuppressive kinetic pattern of MLR and CML induced by MeDSG. In the study of the effect of MeDSG on the interleukin-2 (IL-2) production of allogeneic blast cells, MeDSG showed only a slight suppression. In the MeDSG induced regulator cell assay, these cells induced no suppression of fresh CML, even when they were adoptively transferred to fresh bulk MLR in CML at different times. In the subset analysis of surface phenotypes of allogeneic blast cells in MLR, IL-2R+ cells and CD8+ LFA1+ cells treated with MeDSG, were significantly decreased. These results indicate that MeDSG acts on a comparatively early stage of the afferent phase in allogeneic stimulation and suppresses development of cytotoxic lymphocytes strongly, without inhibition of IL-2 production or suppressive regulator cell induction.

Endocytosis and dissociation of class I MHC molecules labeled with fluorescent beta-2 microglobulin

Membrane class I MHC molecules of Con-A activated and lymphoma murine cells have been labeled by exchange of the cell's beta 2m with soluble fl-beta 2m. It has previously been shown that this method of labeling is specific and does not affect the biologic properties of class I MHC Ag. With this labeling it has been possible to demonstrate the constitutive endocytosis of class I MHC by fluorescence microscopy and by measuring the resistance to quenching by crystal violet of the internalized fl-beta 2m molecules. We could also follow the kinetics of beta 2m dissociation from the class I molecules at different pH. At pH 5.5, that is the average pH of endosomes, there is considerable dissociation within 15 to 20 min, that is the average recycling half time of class I MHC containing endosomes in activated T cells. Inasmuch as the process is reversible it is likely that, in the recycling endosomes of T cells, class I MHC molecules undergo conformational changes with beta 2m going off and on and with consequent changes of the peptide binding site. This process might be involved in Ag presentation, but, because it is apparently limited to T cells, it would play a role in the presentation of the cell's own TCR in idiotypic interactions between T cells.

Endocytosis and dissociation of class I MHC molecules labeled with fluorescent beta-2 microglobulin

Membrane class I MHC molecules of Con-A activated and lymphoma murine cells have been labeled by exchange of the cell's beta 2m with soluble fl-beta 2m. It has previously been shown that this method of labeling is specific and does not affect the biologic properties of class I MHC Ag. With this labeling it has been possible to demonstrate the constitutive endocytosis of class I MHC by fluorescence microscopy and by measuring the resistance to quenching by crystal violet of the internalized fl-beta 2m molecules. We could also follow the kinetics of beta 2m dissociation from the class I molecules at different pH. At pH 5.5, that is the average pH of endosomes, there is considerable dissociation within 15 to 20 min, that is the average recycling half time of class I MHC containing endosomes in activated T cells. Inasmuch as the process is reversible it is likely that, in the recycling endosomes of T cells, class I MHC molecules undergo conformational changes with beta 2m going off and on and with consequent changes of the peptide binding site. This process might be involved in Ag presentation, but, because it is apparently limited to T cells, it would play a role in the presentation of the cell's own TCR in idiotypic interactions between T cells.

Effect of epinephrine or cAMP on cAMP-bound protein kinase holoenzymes in rat heart

Nonperfused or epinephrine-perfused rat hearts were used to examine the relative amounts of adenosine 3',5'-cyclic monophosphate (cAMP)-free and cAMP-bound holoenzymes of type II cAMP-dependent protein kinase (cAK). Crude tissue extracts of nonperfused hearts were chromatographed in the absence or presence of [3H]cAMP using DEAE-high-performance liquid chromatography. A partially resolved cAMP-free peak of cAK eluted at 0.17 M NaCl, and an asymmetric peak containing bound [3H]cAMP eluted at a slightly higher NaCl concentration. The first peak contained a tetrameric holoenzyme [2 regulatory (R) subunits and 2 catalytic (C) subunits]. From analysis of R-to-C ratios, the [3H]cAMP-bound peak contained a mixture of tetrameric and trimeric (R2C) forms. Both cAMP-free and cAMP-bound holoenzyme forms were virtually inactive without added cAMP under the conditions used. [3H]cAMP dissociation rate studies revealed that the bound cAMP in the peak fraction was equally distributed in the two different binding sites of the enzyme. Compared with the cAMP-free form, the cAMP-bound enzyme in the peak fraction exhibited enhanced binding in nonequilibrium [3H]cAMP binding assays. The cAMP-bound holoenzymes were estimated to represent at least 64% of the total type II cAK in control extracts, and the cAMP-free form was largely converted to the cAMP-bound forms by perfusing hearts with epinephrine.

The potent anti-tumor-promoting agent isoliquiritigenin

A topical application of a chalcone derivative, 4,2',4'-trihydroxychalcone (isoliquiritigenin) inhibited epidermal ornithine decarboxylase (ODC) induction and ear edema formation, i.e. inflammation, caused by a topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA) in CD-1 mice. In addition, isoliquiritigenin potently inhibited 7,12-dimethylbenz[alpha]anthracene (DMBA)-initiated and TPA-promoted skin papilloma formation. This inhibitory effect of isoliquiritigenin was not due to any damage inflicted on the initiated cells but due to its anti-tumor-promoting action. Isoliquiritigenin also inhibited epidermal ODC induction and skin tumor promotion caused by 7-bromomethylbenz[alpha]anthracene (BrMBA), a non-TPA type of tumor-promoting agent, in DMBA-initiated mice. Isoliquiritigenin inhibits neither 12-lipoxygenase nor cyclooxygenase in epidermal subcellular fractions. This compound, however, inhibited TPA-stimulated prostaglandin E2 (PGE2) production in intact epidermal cells. ODC induction caused by TPA was inhibited by a topical application of cyclooxygenase inhibitor, indomethacin. Inhibition of ODC induction by indomethacin was counteracted by a topical application of PGE2, while inhibition caused by isoliquiritigenin was not overcome by PGE2. The results suggest that a mechanism other than the inhibition of PGE2 production is involved in the anti-tumor-promoting action of isoliquiritigenin. Isoliquiritigenin failed to inhibit phospholipase A2 activity of platelet sonicates, but inhibited platelet 12-lipoxygenase and 5-lipoxygenase in polymorphonuclear leukocytes. Therefore, it might be possible that isoliquiritigenin exerts its anti-tumor-promoting action through the lipoxygenase inhibition by acting on cells other than the target epidermal cells. Our present results, in combination with our previous data, demonstrate that some chalcone derivatives and flavonoids which show a potent lipoxygenase inhibitory action act on a common step in the skin tumor promotion caused by two different types of tumor-promoting agents, i.e. TPA and BrMBA, and suggest that these compounds show promise as drugs to prevent tumor promotion.

[Effect of endothelin on rat mesenteric microvessels]

By video microscope, it was observed that endothelin (ET) caused constriction of the mesenteric microvessels of pentobarbital-anesthetized Wistar rats in a dose-dependent manner. With the consequence of causing a decrease of rate of blood flow and even some microcirculation disorder, the action was long lasting. The constrictive effect of ET on microvessel was much stronger than norepinephrine. The results suggest that ET is a potent vasoconstrictor for microvessel and may play an important role in causing microcirculatory disorder.

Effect of FK-506 on heart allograft survival in the highly sensitized recipient rats as compared with ciclosporin and 15-deoxyspergualin

The effect of FK-506 on allograft survival in unsensitized recipients has been established in several animal experimental models. In this present study, we investigated the immunosuppressive capacity of FK-506, in comparison with ciclosporin (Cs) and 15-deoxyspergualin (DSG), on heart allograft in presensitized rats. Heart grafts from male ACI rats were heterotopically transplanted to male LEW rats. All recipient rats were sensitized with donor-type whole blood admixed with immunoadjuvant (adjuvant complete Freund) 7 days prior to transplantation. FK-506, Cs and DSG were administered from day 0 to day 14 posttransplantation. The results showed that both FK-506 and Cs significantly prolonged heart allograft survival of presensitized recipients in a dose-dependent manner. The minimum effective dose in the treatment was less for FK-506 than for Cs. However, DSG showed almost no effect of prolongation in this experiment.

In vitro immunosuppressive effect: a comparative study between deoxymethylspergualin and cyclosporin A, on human lymphocyte responses

The immunosuppressive mechanism of Deoxymethylspergualin (MeDSG) on human lymphocyte responses in vitro was assessed in comparison with Cyclosporin A (CyA). Peripheral blood mononuclear cells from normal human volunteers were used for assay of mixed lymphocyte reaction (MLR), cell-mediated lympholysis (CML) and blastogenesis by PHA and OKT3. MeDSG suppressed only allogenic stimulation (MLR and CML), however, CyA showed a suppressive effect for all assays. Kinetic study of MLR showed that the suppressive activity did not decrease even when MeDSG was added at day 3 or day 4. CyA, however, showed a weak suppressive effect when added at a later phase of MLR. The results suggest that MeDSG is a useful immunosuppressive agent and, in vitro, its immunosuppressive mechanism on human lymphocyte responses is quite different from CyA.

The carriage of Escherichia coli resistant to antimicrobial agents by healthy children in Boston, in Caracas, Venezuela, and in Qin Pu, China

BACKGROUND AND METHODS

The healthy members of a community represent its largest reservoir of bacteria resistant to antimicrobial agents. We compared the resistance to eight agents of Escherichia coli in stool samples from untreated, healthy children in cities on three continents.

RESULTS

When screened by a selective method that detected 1 resistant colony in 10,000 colonies, nearly half the children in Boston (18 of 39) had no resistant colonies--a finding consistent with the findings of other surveys performed in developed countries. However, all but 1 of 41 children screened in Caracas, Venezuela, and all but 2 of 53 in Qin Pu, China, carried resistant strains. Only 1 child in Boston but 25 in Caracas and 34 in Qin Pu carried strains resistant to trimethoprim. None of the children in Boston or Caracas but 17 in Qin Pu carried strains resistant to gentamicin. Among 10 colonies selected randomly from each stool sample, the average frequency of resistance in Caracas was 3.6 times greater than in Boston, and that in Qin Pu was 5.3 times greater. There was resistance to five or more antimicrobial agents in 20 percent of the Qin Pu strains and in 6 percent of the Caracas strains but in none of the Boston strains.

CONCLUSIONS

In addition to clinical isolates, as reported previously, the bacteria that colonize health children in the community may be resistant far more often in some regions than in others. A low rate of carriage of antimicrobial resistance in the community should become a public health goal.

Contractile properties of bronchial smooth muscle with and without cartilage

The majority of in vitro studies on airway smooth muscle have used the trachealis (TSM) as a convenient substitute for muscle from airways that constitute the flow-limiting segment. The latter are technically difficult to work with. However, because the site of maximum resistance to airflow is at the third to seventh generations of the bronchial tree, the trachealis preparation is of limited value. Length-tension and force-velocity properties were therefore studied at optimal length (lo) of canine bronchial smooth muscle (BSM) from which cartilage had been carefully removed. Normalized maximum isometric tension or stress (Po x 10(4) N/m2) for BSM was 7.1 +/- 0.19 (SE), which was similar to that of BSM with cartilage (BSM+C, 6.8 +/- 0.21) but lower than for TSM (18.2 +/- 0.81). At length greater than lo, the BSM+C was stiffer than the BSM. The values of maximum shortening capacity (delta Lmax), obtained directly from isotonic shortening at a load equal to the resting tension at lo, were 0.76 lo +/- 0.03, 0.41 lo +/- 0.02, and 0.24 +/- 0.02 lo for TSM, BSM, and BSM+C, respectively. The BSM and BSM+C delta Lmaxs were different (P less than 0.05). Maximal shortening velocities (Vo) for BSM, elicited at 2, 4, and 8 s by quick release in the course of an isometric contraction were significantly higher than for the BSM+C. Vos showed gradual decreases in all three groups in the later phase of contraction, suggesting the operation of latch bridges.(ABSTRACT TRUNCATED AT 250 WORDS)

Possible mechanism in rat with surviving heart allograft after short course of 15-deoxyspergualin treatment

15-Deoxyspergualin has been reported to be a useful immunosuppressive agent, that is already used to inhibit acute rejection, in clinical transplantation. In the present study, the survival of heart allograft in rats after a short course of DSG treatment and the mechanism underlying induction of DSG-induced heart allograft survival, in the early phase, were studied. Male LEW rats were used as recipients. Male ACI and Wistar rats were used as donors and third party donors, respectively. Survival of ACI heart grafts in LEW recipients, treated with a short course of DSG, beginning from day 4 of grafting, were markedly prolonged, with a mean survival time of 16.6 +/- 5.8 days and 29.8 +/- 3.0 days at the dose of 2.5 mg/kg/day and 5 mg/kg/day, respectively. The mechanism of inducing allograft survival in the early phase, after a short course of DSG treatment, was further analyzed by testing the ability of splenic lymphocytes or serum in MLR assays and transfer experiments. The addition of various concentrations of splenic lymphocytes or serum from DSG treated LEW rat with surviving ACI heart allograft to MLR showed a strong suppression in a cell-dose-dependent manner and serum-dose-dependent manner, both in donor strain and third party MLR. An interesting finding was that there was a constant differential suppressive rate between donor strain party MLR and third party MLR. Moreover, transfer of 2.0 x 10(8) splenic lymphocytes or 2 ml serum from DSG-treated LEW rat with surviving ACI heart allograft, to sublethally irradiated grafted host, did not prolong survival both in ACI heart grafts and third party Wistar grafts. These results suggest that the strong suppresser cells and the suppressor humoral factor(s) play, at least, a partial role in the early phase of rats bearing allograft after a short course of DSG treatment.

[Clinical electrophysiologic effects of lorcainide in patients and its effect on the conduction of accessory pathway in Wolff-Parkinson-White syndrome]

The electrophysiologic effects of the intravenous administration of a new antiarrhythmic drug, lorcainide, were evaluated by programmed electrical stimulation of the heart in 20 patients with and without Wolff-Parkinson-White (WPW) syndromes. Lorcainide shortened the sinus cycle length from 721.0 +/- 125.9 to 649.5 +/- 100.1 ms (P less than 0.001), but did not influence sinus node function and AV node conduction and refractoriness, slightly increased atrial effective period (ERP) (P less than 0.02) and did not change ventricular ERP (P less than 0.2), obviously lengthened atrial conduction time, H, H-V interval and the width of V wave. Lorcainide caused complete antegrade block of the accessory pathway (AP) in six of 9 WPW patients and resulted in exclusive conduction over the AV nodal. His conduction in two patients with atrial flutter. It also prolonged the retrograde conduction time and refractoriness of AP, and prevented initiation of orthodromic atrioventricular tachycardia (O-AVRT) in six of 12 patients by blocking of the retrograde conduction of the AP, increased the cycle length of tachycardia from 321.7 +/- 43.6 to 361.7 +/- 54.9 ms (P less than 0.005) by marked prolongation of retrograde AP conduction time in 6 patients in whom O-AVRT could still be induced. It is concluded that intravenous lorcainide does not affect sinus node and AV node function, slightly influences atrial and ventricular refractoriness, obviously suppresses atrial, His bundle and intraventricular conduction, and is an effective antiarrhythmic drug for patients with WPW by blocking both the antegrade and retrograde conduction of the AP.

A New Synthesis of Xanthones. 2,4,7-Trichloronorlichexanthone and 4,5,7-Trichloronorlichexanthone, Two New Lichen Xanthones

A new synthetic route to norlichexanthone (1,3,6-trihydroxy-8-methyl- 9H-xanthen-9-one) derivatives has been developed by using a Smiles rearrangement of an appropriately substituted depside in the key step. 2,4,7-Trichloronorlichexanthone (22) and 4,5,7- trichloronorlichexanthone (29) have been prepared by this method. The former xanthone (22) was shown to be a constituent of the lichens Lecanora sulphurata and L. flavo-pallescens and the latter (29) a constituent of Micarea austroternaria var. isabellina.

Structure and Synthesis of the Lichen Xanthone Isoarthothelin (2,5,7-Trichloronorlichexanthone)

The structure of isoarthothelin (2,5,7-trichloro-1,3,6-trihydroxy-8-methyl-9H-xanthen-9-one or 2,5,7-trichloronorlichexanthone)(2), a metabolite of an Australian Buellia species and Lecanora broccha, was confirmed by total synthesis. Previous reports of the natural occurrence of (2) refer for the most part to an isomeric compound.

5,7-Dichloro-3-O-methylnorliche-xanthone, a New Xanthone From the Lichen Lecanora broccha

5,7-Dichloro-1,6-dihydroxy-3-methoxy-8-methyl-9H-xanthen-9-one (7) (5,7-dichloro-3-O-methylnorlichexanthone) has been synthesized and shown to cooccur with 2,5,7-trichloro-3-O-methylnorlichexanthone (6) in the lichen Lecanora broccha.

[Influence of finger pressing massage on cAMP and cGMP in the cerebrospinal fluid in prolapsed intervertebral disc]

This paper used RIA method to observe 11 cases of prolapsed intervertebral disc patients, detect the change of cAMP and cGMP in the cerebrospinal fluid before and after finger pressing massage in acupuncture point Weizhong and Chengshan in order to discuss the mechanism of analgesia of finger pressing massage. The results showed that the pain was relieved after finger pressing massage. cAMP of the cerebrospinal fluid increased from 0.51 +/- 0.19 to 0.63 +/- 0.13 pm/ml, in average 32% higher than that before the therapy (P less than 0.05). Since cGMP decreased from 30.52 +/- 26.42 to 23.20 +/- 16.91 pm/ml, it showed that the mechanism of analgesia of finger pressing massage might be due to the fact that the therapy excited selectively endogenous analgesia system, caused the increase of endorphin releasing, and was accompanied by the regulation of cAMP and cGMP.

Elucidation of a protease-sensitive site involved in the binding of calcium to C-reactive protein

C-reactive protein (CRP) is a Ca2+-binding protein composed of five identical 23-kDa subunits arranged as a cyclic pentamer, present in greatly elevated concentration in the blood during the acute phase of processes involving tissue injury and necrosis. In the present work, it was found that treatment of human CRP with Pronase or Nagarse protease produces two major fragments which remain associated in physiological buffers but are separable under denaturing conditions. To localize the cleavage site(s), the fragments were characterized according to molecular mass, amino acid composition, partial amino acid sequence, and reactivity with monoclonal antibodies specific for the fragments and for defined CRP epitopes including residues 147-152 and 199-206. Nagarse protease cleaves the CRP subunit between residues 145 and 146, producing two fragments, 16 and 6.5 kDa (calculated molecular mass). Pronase cleaves the CRP subunit between residues 146 and 147, producing a 16-kDa fragment (A1) and a 6.5-kDa fragment (B); an additional fragment (A2) approximately 1 kDa smaller than fragment A1 is also apparently produced due to a secondary cleavage site in fragment A1. Cleavage appears to be completely inhibited in the presence of 1 mM CaCl2. Ca2+ does not protect cleaved CRP from heat-induced aggregation (i.e., precipitation) as it does the intact protein. Protease-cleaved CRP loses the ability to bind to the Ca2+-dependent ligand phosphorylcholine but remains the ability to bind to the Ca2+-independent ligand arginine-rich histone. Equilibrium dialysis indicates that intact CRP binds 2 mol of Ca2+/mol of subunit with a Kd of 6 X 10(-5) M.(ABSTRACT TRUNCATED AT 250 WORDS)

[Preservation of cytomegalovirus by lyophilization]

The preservation of cytomegalovirus (CMV) by lyophilization was first developed in China. In 4 to 10 days the typical CPE was up to + in the HEL cell line which was inoculated only 0.2 ml suspension of lyophilized strain AD169 or CMV isolated from milk breast. After preserved for 1 year the lyophilized cytomegalovirus strain still contained 1.5-2.0 lgTCID50/0.1 ml in titer of viral infection. The lyophilized strains have been used in the preparation of diagnostic antigen of cytomegalovirus in our department, also the strains were supplied to the whole country.

The discrete dynamics of symmetric competition in the plane

We consider the generalized Lotka-Volterra two-species system xn + 1 = xn exp(r1(1 - xn) - s1yn) yn + 1 = yn exp(r2(1 - yn) - s2xn) originally proposed by R. M. May as a model for competitive interaction. In the symmetric case that r1 = r2 and s1 = s2, a region of ultimate confinement is found and the dynamics therein are described in some detail. The bifurcations of periodic points of low period are studied, and a cascade of period-doubling bifurcations is indicated. Within the confinement region, a parameter region is determined for the stable Hopf bifurcation of a pair of symmetrically placed period-two points, which imposes a second component of oscillation near the stable cycles. It is suggested that the symmetric competitive model contains much of the dynamical complexity to be expected in any discrete two-dimensional competitive model.

Hormone-stimulated polyphosphoinositide breakdown in rat liver plasma membranes. Roles of guanine nucleotides and calcium

Calcium-sensitive inositide release in a purified rat liver plasma membrane preparation is increased by calcium-mobilizing hormones in the presence of guanine nucleotides. Vasopressin-stimulated inositide release is evident in the presence of GTP or its nonhydrolyzable analogs guanyl-5'-yl imidodiphosphate and guanosine 5'-(3-O-thio)triphosphate (GTP gamma S). The stimulation of inositide release by (-)-epinephrine (alpha 1), angiotensin II, or vasopressin in the presence of either 1 microM or 10 microM GTP gamma S correlates with the number of receptors present for each hormone. The guanine nucleotide and hormonal stimulation is evident on both inositol trisphosphate production and phosphatidylinositol bisphosphate degradation. Ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (1 mM) completely abolishes stimulation by guanine nucleotides and hormone. Prior treatment of plasma membranes with cholera toxin or islet activating protein or prior injection of animals with islet activating protein does not affect stimulation of inositide release by GTP gamma S or GTP gamma S plus vasopressin. Stimulation by GTP gamma S is dependent upon magnesium and is inhibitable by guanosine 5'-(2-O-thio) diphosphate. Inositide release from the plasma membrane exhibits half-maximal stimulation by calcium at approximately 100 nM free calcium in the presence of 1.5 mM MgCl2 and at approximately 10 microM free calcium in the presence of 10 mM MgCl2. Addition of guanine nucleotides decreases the requirement for calcium and also increases the activity at saturating calcium. The results presented suggest that calcium-mobilizing hormones stimulate polyphosphoinositide breakdown in rat liver plasma membranes through a novel guanine nucleotide binding protein.

Regulation of a liver plasma membrane phosphoinositide phosphodiesterase by guanine nucleotides and calcium

Rat liver plasma membranes are enriched in a Ca2+-dependent phosphodiesterase active on phosphatidylinositol 4,5-P2 and phosphatidylinositol 4-P, but not phosphatidylinositol. Inositol-P3 is the first product of the reaction, but is rapidly degraded. Micromolar concentrations of GTP and its nonhydrolyzable analogues stimulate the reaction, whereas GDP, GMP and other nucleoside triphosphates are inactive. GTP and its analogues decrease the requirement of the reaction for Ca2+ and also increase its activity at saturating Ca2+. These results support the hypothesis that guanine nucleotides and a guanine nucleotide binding regulatory protein are involved in coupling the receptors for Ca2+-mediated agonists to the breakdown of plasma membrane phosphatidylinositol 4,5-P2.