Mono-, di-, and trimethacrylates (monomers) are widely used in dentistry as restorative materials, adhesives, prosthetic devices, etc. It is known that the residual monomers released from the cured resin have been implicated in toxicological effects. In order to monitor the biological actions at the membrane level induced by monomers, we studied the changes in the phase transition temperature (T) and enthalpy (delta H) of dipalmitoyl-phosphatidylcholine liposomes induced by 37 different monomers using differential scanning calorimetry (DSC). The monomers that caused large changes in the T and delta H were vinyl monomers; acrylates; monomethacrylates that contain hydroxy, carbonyl, amino and phenyl groups; dimethacrylates with short-chain substituents; and aliphatic trimethacrylates. It is suggested that the changes in the T and delta H values may be due not only to hydrophobic interactions, but also to interactions induced by the double bonds or the functional groups in the monomers. On the other hand, methacrylates with simple alkyl ester linkage and dimethacrylates with bisphenol A groups exhibited the smallest changes. The changes in the T and delta H induced by highly hydrophobic methacrylates were small due to their slower interaction. These changes in transition properties of liposomes seem to be related to biological activities.

Acrylates↗

PubMedDate not supplied

Effect of continuous intravenous infusion of carteolol chloride on tissue blood flow in rabbit optic nerve head.

PURPOSE: To investigate the effect of an intravenous infusion of carteolol on tissue blood flow in the optic nerve head (ONH) of rabbits. METHODS: Rabbits received either a 3-week topical instillation, or a single intravenous injection (10, 20, 30 microg/kg) or a continuous intravenous injection (2.5, 5, 20, 40, 80 microg/kg per hour) of carteolol. The plasma carteolol level was determined by the gas chromatography negative-ion chemical ionization mass spectrometric method. The ONH blood flow was determined by the hydrogen clearance method. RESULTS: The plasma level of carteolol after a 3-week instillation was 5.55 ng/mL, and a continuous intravenous injection (5 microg/kg per hour) led to approximately the same plasma level. The continuous intravenous infusion of 5 microg/kg per hour of carteolol significantly increased the ONH blood flow compared to the controls from 30 minutes to 2 hours after the beginning of the infusion (n = 10). The mean blood pressure and intraocular pressure (n = 6) were not significantly changed during the continuous intravenous infusion of carteolol. CONCLUSIONS: These results suggest that the plasma carteolol level in rabbits after long-term instillation can increase the ONH blood flow. We conclude that the increase resulted from a reduction in the vascular resistance in the ONH.

Adrenergic beta-Antagonists↗

PubMedDate not supplied

Selective pericyte degeneration in the retinal capillaries of galactose-fed dogs results from apoptosis linked to aldose reductase-catalyzed galactitol accumulation.

Galactose-fed dogs develop retinal capillary changes similar to diabetic retinopathy with pericyte degeneration as the initial lesion. This is followed by the formation of microaneurysms, hemorrhages, and some areas of acellularity. To investigate the mechanisms for selective pericyte degeneration, retinal capillary pericytes and endothelial cells isolated from beagle dog retina were cultured for 2 weeks in Dulbecco's modified Eagle's medium (DMEM) containing 50 mM D-galactose. Apoptosis was detected in pericytes but not endothelial cells by in situ terminal deoxynucleotidyl transferase (TdT)-mediated biotin-dUTP nick end labelling (TUNEL) staining and the DNA fragmentation assay on agarose gel electrophoresis. This apoptosis was prevented by the addition of the aldose reductase inhibitor AL 1576 to the culture medium containing galactose. Apoptosis was not observed when pericytes were similarly cultured in control DMEM medium. These data support the premise that the selective degeneration of retinal capillary pericytes observed in galactose-fed dogs is linked to increased aldose reductase activity in these cells.

Aldehyde Reductase↗

PubMedDate not supplied

Radical intensity and cytotoxicity of butylated hydroxyanisole and its orthobisphenol dimer.

The radical intensity of BHA (4-Hydroxy-3-t-butylanisole) and its dimer (3,3'-Di-t-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diol, Bis-BHA) were compared with their cytotoxic activity. ESR spectroscopy showed that BHA produced characteristic five peaks of radicals under alkaline conditions (pH > 9.5). At higher pH, BHA radical rapidly disappeared, and progressively transformed into new radical species, as detected by the splitting of the ESR signal. BHA showed higher cytotoxic activity against salivary gland tumor cell line than against normal human gingival fibroblast. On the other hand, Bis-BHA did not produce any detectable amounts of radicals at wide ranges of pH, corresponding with its weaker cytotoxic activity as compared with BHA. BHA scavenged DPPH (1,1-Diphenyl-2-picrylhydrazyl) radical and superoxide anion, more efficiently than Bis-BHA. The present study demonstrated that BHA is more cytotoxic, produces higher amounts of radicals and more efficiently scavenges various radical species, as compared with Bis-BHA. This suggests the possible link between the cytotoxic activity and radical generation/scavenging activity in BHA-derived compounds.

Antioxidants↗

PubMedDate not supplied

Interaction between antioxidants and hydroquinone/bisphenol.

We have investigated the stability of semiquinone radical (SQ .) produced from the mixture of hydroquinone (HQ) and bisphenol A (BPA) in the presence of various antioxidants, some of which induce apoptosis in tumor cell lines. BPA produced no detectable amount of ESR signal. The acceleration of HQ oxidation by BPA results in the production of SQ .. The BPA-enhanced SQ . production may occur through either SQ. regeneration by electron transfer from BPA working as an antioxidant or the O2- scavenging activity of BPA. SQ . intensity of HQ/BPA was reduced by lower concentrations of sodium ascorbate, epigallocatechin, gallate and quercetin, but significantly enhanced by gallic acid. The initial SQ . was replaced by the radicals of antioxidants except lignin and salicylic acid, at higher concentrations, due to their radical-radical coupling or dismutation process. Among these compounds, gallic acid enhanced the radical intensity of SQ . to the greatest extent. The results suggest that antioxidants from foods suppress the activity of xenobiotics such as HQ, however, they produce their own radical at higher concentrations, suggesting their bimodal actions. The present study demonstrates the usefulness of ESR spectroscopy for the interaction between HQ/BPA and antioxidants.

Antioxidants↗

PubMedDate not supplied

Induction of apoptosis by dopamine in human oral tumor cell lines.

Dopamine dose-dependently reduced the viable cell number of both human salivary gland tumor HSG and oral squamous cell carcinoma HSC-2, HSC-4, and NA cells. CoCl2 significantly reduced both the cytotoxic activity and radical intensity of dopamine (determined by ESR spectroscopy). Dopamine produced DNA fragments (demonstrated by TUNEL method) and induced degradation of cytokeratin by activated caspase in HSG cells (detected by an immunocytochemical method, using a specific M30 monoclonal antibody). FACS analysis demonstrated that dopamine induced DNA fragmentation, a biochemical hallmark of apoptosis, in human promyelocytic leukemia HL-60 cells. The addition of catalase did not prevent the apoptosis-inducing activity of dopamine, reducing the possibility of the involvement of H2O2 for dopamine-induced apoptosis. Dopamine transiently induced p38 mitogen-activated protein kinase (MAP kinase) phosphorylation. However, an inhibitor of p38 MAP kinase phosphorylation, SB203680, failed to inhibit the dopamine-induced apoptosis. These data suggest that p38 phosphorylation at an early stage may not be a causative event for apoptosis.

Apoptosis↗