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PubMed1988

The chemical and enzymatic interaction of glutathione with the fungal metabolite, fusarin C.

Glutathione (GSH) interacts both chemically and enzymatically with fusarin C, a mutagenic metabolite produced by Fusarium moniliforme. The chemical reaction, which is pH-dependent, results in the formation of both fusarin A and a compound that lacks the 2-pyrrolidone moiety thereby suggesting an interaction at the C-13-C-14 epoxide. Enzymatic interaction of fusarin C with GSH also appears to occur at this site as fusarins A and D, which lack the epoxide, do not serve as substrates for GSH-S-transferases. The interaction of GSH with fusarin C appears to be an important deactivation step which could explain the lack of carcinogenicity observed for fusarin C in rats.

Chemical Phenomena↗
PubMed1990

Effect of irreversible loss of muscarinic receptors on (3H)-acetylcholine release from the hippocampus.

The role of muscarinic receptors in the regulation of (3H)-acetylcholine (3H-Ach) release from the hippocampus was investigated with the irreversible cholinergic agonist BM-123 (N-[4(2-chloroethylmethylamino)-2-butynyl]2-pyrrolidone). Pretreatment with BM-123 had no significant effect on spontaneous (3H)-Ach release at 12, 24, 72, and 144 hr. However, this treatment significantly reduced the inhibitory effect of oxotremorine (10 microM) on (3H)-Ach release at 12, 24, and 72 hr (p less than 0.02). At these time intervals, there was a significant loss in muscarinic receptors as determined by (3H)-oxotremorine-M binding. The maximum loss of both oxotremorine-induced inhibition of (3H)-Ach release and muscarinic receptors occurred at 12 hr. Both parameters returned to normal by 144 hr. There was a linear relationship between the recovery of (3H)-Ach release and (3H)-oxotremorine-M binding sites. These results indicate that muscarinic receptors play a significant role in the regulation of (3H)-Ach release in hippocampus, and that this receptor system may lack spare receptors.

Acetylcholine↗
PubMed1986

Comparison of fast (one-step) and interrupted slow cooling methods using a range of intracellular and extracellular cryoprotectants for the freeze-preservation of Plasmodium yoelii-infected mouse erythrocytes.

Several cryoprotectants were compared using two different cooling procedures for the cryopreservation of both normal and Plasmodium yoelii-infected mouse erythrocytes. Fast cooling to -196 degrees C by direct plunge into liquid nitrogen followed by rapid thawing in a 37 degree C water bath protected uninfected and parasitized erythrocytes against freeze-thaw damage significantly better than an interrupted slow cooling procedure in which cells were frozen to -70 degrees C at a rate of -1 degree C/min followed by storage in liquid nitrogen. Using the former procedure, the highest percentage erythrocyte recoveries (over 85%) and shortest pre-2% parasitaemia times (equivalent to unfrozen cells) in mice challenged with thawed parasitized blood were observed with the intracellular (penetrating) cryoprotectants glycerol or dimethylsulphoxide (Me2SO). At the concentrations used in this study, the extracellular (non-penetrating) cryoprotectants, hydroxyethylstarch, dextran or polyvinyl pyrrolidone were significantly less effective at protecting against freeze-thaw damage. Some evidence of freeze-thaw damage was obtained in cells fast frozen at low cell density (less than or equal to 10(4)/ml) in glycerol or Me2SO. This effect was masked when higher cell densities (10(7) to 10(8)/ml) were used. Addition of the anti-oxidant and membrane stabilizing molecules, vitamin E, sodium selenite or selenomethionine to infected erythrocytes just before and during cryopreservation, did not improve, and in one case inhibited, subsequent development in challenged mice.

Animals↗
PubMed1983

The relationship between the age and density of circulating 51-Cr labelled platelets in the sub-human primate.

Change in the density of circulating platelets in monkeys was studied by using a method that removed greater than 90% of the platelet population from whole blood. These were labelled with 51-Cr and reinjected, having been protected by prostacyclin while in vitro. Platelets were separated into density subpopulations the following day by continuous linear gradients of polyvinyl pyrrolidone coated silica (Percoll) under conditions that approximated well to equilibrium centrifugation. The 51-Cr labelled platelets were then found to be distributed equally throughout all density subpopulations. When the same procedure was repeated at 5 days after re-injection an average of 5% of the density range increase in platelet density had occurred in the reinjected platelets compared to the circulating population (p less than 0.001). Lighter platelets may have a slightly shorter survival time than dense ones. Monkey platelet volume is log normally distributed.

Animals↗
PubMed1982

Brain cyclic AMP and memory in mice.

A phosphodiesterase inhibitor 4-(3-cyclopentyloxy-4-methoxyphenyl)-2-pyrrolidone (Rolipram, 10 mg/kg IP) administered immediately, but not 3 hr post-training, reversed an amnesia for an inhibitory avoidance response induced by the protein synthesis inhibitor anisomycin. Immediate post-training administration of Rolipram also enhanced retention for a weakly learned avoidance response. Unshocked animals did not show increased test latencies thus ruling out conditioned aversion as an explanation for the enhanced avoidance. Mice treated with Rolipram (10 mg/kg after training showed elevated cyclic AMP but not cyclic GMP in frontal cortex, thalamus, and hypothalamus. These results support the suggestion that cyclic AMP may play a role in memory processes.

Animals↗
PubMed1985

Prolongation of latencies for passive avoidance responses in rats treated with aniracetam or piracetam.

Effects of aniracetam (1-anysoyl-2-pyrrolodone) and piracetam (1-acetamido-2-pyrrolidone) on passive avoidance behavior were studied in 2 and 18 months old rats using a step-down passive avoidance task. Repeated administration of aniracetam (30 and 50 mg/kg, IP X 5 days) or piracetam (100 mg/kg, IP X 5 days) significantly prolonged step-down latencies for a passive avoidance task in 2 months old rats. Administration of aniracetam (50 mg/kg, IP) or piracetam (100 mg/kg, IP), however, did not affect locomotor activity. This prolongation of latencies was also seen with oral administration of aniracetam (50 mg/kg X 5 days). Similar prolongation of latencies also occurred in 18 months old rat treated with aniracetam (50 mg/kg, IP X 5 days). The results imply that aniracetam may improve learning and/or memory in 2 and 18 months old rats.

Animals↗
PubMed1988

Effects of an irreversible muscarinic agonist (BM123) on avoidance and spontaneous alternation performance.

The present study sought to assess whether the compound N-[4-(2-chloro-ethylmethylamine)-2-butynyl]-2-pyrrolidone (BM123), a potent muscarinic agonist that binds irreversibly to the muscarinic receptor (mAChR), has long-lasting functional effects which may be related to a reduction in functional mAChRs. Passive (inhibitory) avoidance performance, one-way active avoidance learning, and spontaneous alternation behavior were studied in rats. The results confirmed the acute muscarinic stimulating effects of BM123, including tremor, salivation, chromodacryorrhea and hypothermia. In addition, when measured 3-4 days after administration, rats treated with BM123 had disrupted spontaneous alternation performance and tended to have impaired performance for the inhibitory avoidance task with facilitated acquisition of active avoidance. This spectrum of effects is consistent with previous reports showing a 20-40% reduction in mAChRs at these times after BM123. The reversible muscarinic agonist, oxotremorine, was without significant effect. In a further experiment, it was found that pretreatment with methyl atropine did not prevent the disruption of spontaneous alternation behavior by BM123, whereas pretreatment with atropine did. Thus, these long-lasting behavioral effects of BM123 are related to its alkylation of and subsequent reduction in central mAChRs.

Animals↗
PubMed1990

Pretreatment with an irreversible muscarinic agonist affects responses to apomorphine.

The main aim of the present study was to investigate if responses to the direct dopamine agonist, apomorphine, could be modified by changes in the activity of cholinergic neurones. A novel approach was adopted in which these responses were assessed following reduction of muscarinic receptor concentration (mAChR) in the brain (assessed from [3H] QNB binding) by the alkylating derivative of oxotremorine, N-[4-(2-chloroethylmethylamino)]-2-pyrrolidone (BM 123). Stereotyped responses elicited by apomorphine were significantly reduced when QNB binding was 12% and 50% of control values. No changes in [3H] spiperone binding were found. There was significant hypothermia in the group with 12% QNB binding sites which was significantly increased by apomorphine. Body temperature returned to normal when QNB binding was 50% of control values. There was a significant decrease in activity when QNB sites were reduced to 12% of normal and vertical activity was still significantly reduced at 50% QNB binding, though horizontal activity was not then different from controls. These data are consistent with the hypothesis that changes in the function of mAChR modify responses elicited by dopamine receptor stimulation in both the striatum and other brain regions.

Animals↗
PubMed1992

Effects of piracetam on retention and biogenic amine turnover in albino rats.

The chronic effects of orally administered 2-pyrrolidone acetamide (piracetam) on one-trial, passive avoidance task were studied in albino rats. The effects on the contents of norepinephrine (NE), dopamine (DA), and serotonin (5-HT) in the brain and on the levels of their metabolites both in the brain and urine were also assessed. Significant improvement was observed in the retention ability compared with saline-administered controls. The contents of NE, DA, and 5-HT and their metabolites in the brain were significantly decreased after piracetam administration. The urinary metabolite levels were also significantly decreased except total 3-methoxy-4-hydroxyphenyl glycol (MHPG). These data indicate that piracetam causes an overall decrease in the turnover of central monoamines. Thus, the results of this study implicate the involvement of NE, DA, and 5-HT systems in learning and memory processes. Piracetam did not exert any GABAergic effect as shown by the absence of change in the brain GABA levels.

Animals↗
PubMed1992

Fertilization of bovine oocytes after microsurgical injection of spermatozoa.

The objective of this study was to compare the fertilization rate of bovine oocytes matured in vitro (22, 25 or 28 hours) and in vivo (30 to 35 hours after standing estrus) following the microinjection of a single spermatozoon. A single motile spermatozoon was injected into the perivitelline space (Experiments 1 to 9), and a single immotile spermatozoon was injected into the ooplasm (Experiments 10 to 15). A single ejaculate of frozen-thawed semen was used throughout. The spermatozoa were injected either without treatment or after treatment with heparin (100 microg/ml), or Ca ionophore A23187 (0.1 microM), or co-cultured for 5 hours with bovine oviduct epithelial cells (BOEC), or they were co-cultured for 5 hours with BOEC and immobilized by freezing and thawing twice without cryoprotectant, or they remained untreated. Oocytes were placed in a droplet of hyperosmotic solution of 0.1 M sucrose in PBS to enlarge the perivitelline space (Experiments 1 to 9) or in PBS (Experiments 10 to 15). Small amounts of polyvinyl pyrrolidone (PVP) without spermatozoa were injected as a control for parthenogenetic activation. After injection, oocytes were incubated in Medium 199 for 22 hours at 39 degrees C, and they were stained with 1% aceto-orcein and examined for evidence of fertilization or parthenogenetic activation. Low rates (9 to 11%) of fertilization resulted from injection into the perivitelline space of oocytes matured for 22 hours in vitro irrespective of spermatozoa treatment. Fertilization rates were higher in oocytes matured in vivo after injection into either perivitelline space (66%) or ooplasm (74%) than in oocytes matured in vitro (9 to 44% fertilization). Surprisingly, in oocytes matured in vivo, there was no difference in the proportions fertilized by spermatozoa injection into ooplasm and parthenogenetically activated by injection of medium alone (74 and 66%, respectively).

Journal Article↗
PubMed1993

In vitro survival of murine morulae after quick freezing in the presence of chemically defined macromolecules and different cryoprotectants.

We studied the ability of frozen-thawed mouse morulae to develop in vitro when the cryoprotectant proteins were substituted with one of the following nonorganic macromolecules: polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), and ficoll. We also determined how these agents interacted with 3 different cryoprotectants: glycerol (GLY), propylene glycol (PG), and ethylene glycol (EG). The influence of both of the above factors was measured on the basis of post-thaw morphological appearance, the percentage of development to the expanded blastocyst stage and the total cell count. Morulae (n=950) were collected from superovulated mice. Those classified as good or excellent were distributed among the 12 different freezing solutions, obtained by combining the 3 cryoprotectants with the 4 macromolecules (the 3 mentioned above, plus a control of 5% fetal calf serum) in phosphate buffered saline (PBS). Embryos frozen in PVA, PVP and ficoll tended to be a little difficult to recover from the straws. Development to the expanded blastocyst stage was significantly lower (P<0.05) in propylene glycol (43.6%) than in ethylene glycol (79.5%) or in glycerol (76.1%). Polyvinyl alcohol provided a higher survival rate when combined with glycerol (90.3) or ethylene glycol (95.0), but when it was combined with propylene glycol, only 56.5% of embryos survived after thawing. A positive interaction was observed between glycerol and PVA and between ethylene glycol and PVA or ficoll. The results indicate that fetal serum could be successfully substituted for any of the 3 chemically defined macromolecules. However, our findings also suggest that the use of PG as a cryoprotectant should be avoided when mouse morulae are frozen using the quick freezing method.

Journal Article↗
PubMed1989

Inhibition of pepsin by polyions and c.d. studies.

The effects of poly(vinyl sulphate) (PVS), poly(vinyl pyrrolidone) (PVP) and protamine sulphate with the enzyme pepsin (EC 3.4.23.1) have been investigated. PVS, PVP and protamine acted as inhibitors of the enzyme pepsin at low concentrations, but at high concentrations of the polyions (with the exception of PVS) the inhibition was less pronounced. The catalytic effectiveness of several polyions has been shown experimentally; when used at pH 2.1 with haemoglobin and at pH 5.0 with azocasein thus acted as a weak proteolytic catalyst. The order of effectiveness was: polybrene greater than poly(L-lysine) (PLL) greater than spermine greater than spermidine greater than protamine greater than and PVP relative to pepsin. The hydrolysis of the substrates by the enzyme decreases in the presence of high concentrations of monovalent and/or divalent salts. The purity of the enzyme was assessed by determination of the molecular weight using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), phosphorus and nitrogen content. The circular dichroism (c.d.) spectrum of the enzyme in the wavelength range 240-310 nm, where the polycations did not have a c.d. spectrum has also been studied. Each of the polyions had a definite effect on the c.d. spectrum, showing strong binding to the enzyme. The neutral polymer PVP was also found to modify the c.d. spectrum, showing strong binding to the enzyme. The strengths of the interactions as indicated by the magnitudes of the changes in the c.d. spectrum of pepsin at 270 nm were: polybrene greater than protamine greater than PLL greater than PVP greater than spermidine greater than spermine.

Caseins↗
PubMed1989

Chitin gels.

Chitin dissolved in N,N-dimethylacetamide, N-methyl-2-pyrrolidone and their mixed solvents in the presence of 5% LiCl was treated with acetic anhydride-pyridine, and the mixture solution was heated at 100 degrees C for 6 h to give a partially O-acetylated chitin gel. Chitin dissolved in these solvents in the presence of 5% LiCl was mixed with pyridine, and the mixture solution was heated at 60 degrees C for 5 h to give a chitin gel. Both the gels were rigid and transparent, and their properties and the rate of the hydrolysis of the chitin xerogel by hen-egg white lysozyme were essentially similar to those of N-acetylchitosan gel prepared by chemical N-acetylation of chitosan.

Acetylation↗
PubMed1981

Synthesis and characterization of PVNO and PVNO-PVP hydrogels.

Hydrogels of crosslinked poly(2-vinylpyridine-1-oxide), PVNO, and poly(2-vinylpyridine-1-oxide)-poly(N-vinyl-pyrrolidone), PNVO-PVP, were synthesized. PVNO hydrogels were found to be degradable in a pseudo-biological medium and their stability could be increased by increasing the relative concentration of the crosslinking agent. PVNO-PVP hydrogels were also degradable and their stability could be increased by increasing the relative concentration of crosslinking agent and/or poly(N-vinylpyrrolidone). Swelling ratio and percent solvent content for both types of gels were determined. In addition, for PVNO-PVP gels, swelling properties in solvents with different dielectric constants, at different temperatures and ionic strengths were determined. Antibiotic releasing and water vapour behaviour were also investigated. From the data obtained, the free energy change involved in water vapour adsorption was calculated.

Adsorption↗
PubMed1986

Bulk characterization and scanning electron microscopy of hydrogels of P(VA-co-NVP).

The bulk properties of uncrosslinked and crosslinked random copolymers of vinyl alcohol and N-vinyl-2-pyrrolidone [P(VA-co-NVP)] are reported. Analytical studies were performed by infrared and nuclear magnetic resonance spectroscopy, gel permeation chromatography, potentiometric titration, elemental analysis and scanning electron microscopy. The microscopic studies elucidated the effect of freeze-drying on the network surface topology. The results indicate macrosyneresis of the copolymer hydrogels upon freeze-drying even at -23 degrees C. Rapid collapse of the hydrogel structure is seen upon removal of the bulk and interfacial water in the frozen state.

Biocompatible Materials↗
PubMed1990

Dynamic and equilibrium swelling behaviour of pH-sensitive hydrogels containing 2-hydroxyethyl methacrylate.

The equilibrium and dynamic swelling behaviour of hydrogels containing methacrylic acid or various acrylamides was studied as a function of copolymer composition. In all cases, the comonomer was 2-hydroxyethyl methacrylate, methyl methacrylate or N-vinyl-2-pyrrolidone. It is shown that pH-sensitive behaviour with a wide range of swelling ratios could be obtained using a range of compositional changes. The dynamic swelling behaviour was a function of the acidity of the buffered solution.

Buffers↗
PubMed1995

Biocompatibility and in vivo morphine diffusion into a placebo morphine-triggered naltrexone delivery device in rabbits.

Two key factors in developing a clinically useful triggered naltrexone delivery system are device biocompatibility and ability of morphine to diffuse from the blood into the device in concentrations useful to trigger delivery. Two types of devices were implanted subcutaneously into rabbits and their biocompatibility was investigated. One device consisted of the outer semipermeable regenerated cellulose acetate tubing, closed at both ends with double knots and filled with poly(N-vinyl pyrrolidone) as osmotic filler. The other device was a placebo device that contained within the regenerated cellulose acetate tubing, also closed at both ends with double knots, all device components except naltrexone. Both devices were biocompatible. When the regenerated cellulose acetate device filled with osmotic filler was implanted in rabbits which were subsequently dosed at day 7 and day 14 post-implant with 150 mg kg(-1) morphine sulphate, the concentration of morphine in the device was only about 10-fold less than that measured in rabbit blood. Thus, enough morphine diffuses into the device to make triggering in a real-life situation feasible.

Animals↗
PubMed1996

In vitro degradation of a poly(propylene fumarate)-based composite material.

We investigated the in vitro degradation of a novel degradable polymeric composite material being developed to function as a temporary replacement for trabecular bone. This material is based on a mixture of poly(propylene fumarate) cross-linked by N-vinyl-pyrrolidone and includes sodium chloride and beta-tricalcium phosphate. Using an in vitro test in simulated body fluids, the compressive strengths and compressive moduli of two composite materials increased with degradation time and remained above the minimum values acceptable for trabecular bone substitutes. A compressive strength of 21.3 (+/- 0.4) MPa and a compressive modulus of 696 (+/- 53) MPa were measured after twelve weeks for a composite material with initial strength of 18.0 (+/- 4.6) MPa and initial modulus of 113 (+/- 40) MPa. This unexpected phenomenon may prove to be useful for orthopaedic applications.

Biocompatible Materials↗