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Biomedical subjects

G J Liu

Publications and source records attributed to G J Liu.

At least 37 records · Page 2Linked to original sources
PubMed1996

Enhancing effect of essential oils on the penetration of 5-fluorouracil through rat skin.

Three essential oils as penetration enhancers for 5-fluorouracil (5-FU) were studied using excised rat skin. The oils used were eucalyptus, peppermint and turpentine. Azone was used for comparison. The enhancing effect of the oils was found to be less than that of azone, but all the oils used enhanced the permeation of 5-FU. Eucalyptus oil was found to be the most active, causing about 60 fold increase, while peppermint and turpentine caused 46 and 28 fold increase, respectively. Eucalyptus oil was further studied by grading it into 5 fractions according to difference in boiling points. It was found that their activities increased as their boiling point increased. With all enhancers increased partition coefficients were observed but the diffusion coefficient values obtained were comparatively higher. The mode of action of these accelerants may be described by combined processes of partition and diffusion, the diffusion process being dominant.

Administration, Cutaneous↗
PubMed1995

Effects of dopamine on snail neurones.

The pharmacological features of dopamine receptors in identifiable giant neurone types of a snail (Achatina fulica Férussac) were studied. Under voltage clamp, two neurone types, LVMN (left ventral multiple spike neurone) and d-RPeAN (dorsal-right pedal anterior neurone), produced an inward current (Iin) in response to dopamine, (-)-noradrenaline and epinine, whereas v-LCDN (ventral-left cerebral distinct neurone) produced an outward current (Iout) in response to dopamine and epinine. Mammalian dopamine receptor agonists, fenoldopam (dopamine D1-like receptor agonist), (+/-)-SKF 38393 (1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine-7,8- diol) (D1-like), apomorphine (D2-like), (-)-quinpirole (D3 and D4) and methylergometrine showed slight or no effect. (+/-)-SKF 83566 ((+/-)-7-bromo-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benza zepine) (dopamine D1-like receptor antagonist) and (+)-UH 232 (cis-(+)-5-methoxy-1-methyl-2-(di-n-propylamino)tetralin) (D3 and D2) non-competitively inhibited the Iin of LVMN and d-RPeAN, but (+/-)-sulpiride (D2-like) was without effect. In contrast, (+/-)-sulpiride competitively inhibited Iout of v-LCDN, (+)-UH 232 non-competitively inhibited Iout of v-LCDN but (+/-)-SKF 83566 was without effect. H-7 (1-(5-isoquinolinesulfonyl)-2-methylpiperazine) (non-selective protein kinase inhibitor) inhibited Iin of LVMN and d-RPeAN, but did not affect Iout of v-LCDN. Dopamine-induced Iin was Na(+)-dependent; Iout was K(+)-dependent. Ouabain did not affect these currents. We propose that the pharmacological features of Achatina neuronal dopamine receptors are not fully comparable to those of mammals, although intracellular signal transduction systems linked with dopamine receptors may similarly exist in different animal species.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1995

Blockers for excitatory effects of achatin-I, a tetrapeptide having a D-phenylalanine residue, on a snail neurone.

Some histamine H1 receptor antagonists suppressed the inward current (Iin) of an Achatina identifiable neurone type, PON (periodically oscillating neurone), caused by an Achatina endogenous tetrapeptide having a D-phenylalanine residue, achatin-I (Gly-D-Phe-Ala-Asp), under voltage clamp. Achatin-I was applied locally to the neurone by brief pneumatic pressure ejection and antagonists were administered by perfusion. The dose-response curves of the effective histamine H1 antagonists indicated their potency order to suppress the Iin as follows: chlorcyclizine, promethazine, triprolidine and homochlorcyclizine > trimeprazine and clemastine > diphenylpyraline. The potent drugs were mostly piperazine and phenothiazine types. The effects of chlorcyclizine, promethazine and triprolidine on the dose (the duration of the pressure ejection)-response curve of achatin-I indicated that these drugs affected the Iin caused by achatin-I in a non-competitive manner. The antagonists for the receptors of the small-molecule neurotransmitters other than histamine H1, such as histamine H2, acetylcholine, gamma-aminobutyric acid (GABA), L-glutamic acid, dopamine, alpha- and beta-adrenalin and 5-hydroxytryptamine, had no effect on the Iin caused by achatin-I.

Amino Acid Sequence↗
PubMed1995

Suppressing effects of neuroactive peptides on the inward current caused by achatin-I, an Achatina endogenous peptide.

1. Modulatory effects of the four molluscan neuroactive peptides. FMRFamide (Phe-Met-Arg-Phe-NH2), APGW-amide (Ala-Pro-Gly-Trp-NH2), oxytocin and [SER2]-Mytilus inhibitory peptide ([SER2]-MIP) (Gly-Ser-Pro-Met-Phe-Val-NH2) were examined on the inward current (Iin) caused by achatin-I (Gly-D-Phe-Ala-Asp), which has been isolated from the Achatina ganglia. 2. Two Achatina giant neurone types, v-RCDN (ventral-right cerebral distinct neurone) and PON (periodically oscillating neurone), were used. Achatin-I was applied locally to the neurone tested by brief pneumatic pressure ejection, and the other molluscan neuroactive peptides were perfused around the ganglia. 3. FMRFamide, perfused at 3 microM, suppressed markedly the Iin elicited by the achatin-I of both v-RCDN and PON. APGW-amide at 3 microM also suppressed the Iin of v-RCDN, but did not affect that of PON. Oxytocin at 1 microM suppressed the Iin of PON, but did not affect that of v-RCDN. [Ser2]-MIP at 3 microM did not affect the Iin of v-RCDN. 4. The dose-response curves of FMRFamide, APGW-amide and oxytocin, indicated that their respective suppressive effects on the Iin of achatin-I were dose-dependent, and that APGW-amide was slightly more potent than the other peptides. The dose (pressure duration)-response curves of achatin-I (1 kg/cm2, 10(-3) M, 5 min interval), obtained by varying the duration of the achatin-I pressure ejection, were measured in the presence and absence of each of the three peptides.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Further mapping of the Achatina giant neurone types sensitive to the neuroactive peptides isolated from invertebrates.

1. The effects of the 10 synthetic neuroactive peptides originally isolated from invertebrates, applied locally to the neurone tested by the brief pneumatic pressure ejection on the identifiable neurone types of Achatina fulica Ferussac were examined. 2. Achatin-1 (Gly-D-Phe-Ala-Asp), an Achatina endogenous tetrapeptide having a D-phenylalanine residue, ejected locally, showed the depolarizing effects on nearly half of the number of neurone types tested. 3. ACEP-1 (Ser-Gly-Gln-Ser-Trp-Arg-Pro-Gln-Gly-Arg-Phe-NH2), isolated originally from Achatina atria, and pedal peptide (Pro-Leu-Asp-Ser-Val-Tyr-Gly-Thr-His-Gly-Met-Ser-Gly-Phe-Ala) and buccalin (Gly-Met-Asp-Ser-Leu-Ala-Phe-Ser-Gly-Gly-Leu-NH2), found in Aplysia neurones, showed excitatory effects on some Achatina neurone types. 4. Myomodulin (Pro-Met-Ser-Met-Leu-Arg-Leu-NH2), found in Aplysia neurones, produced a hyperpolarization on nearly half of the number of Achatina neurone types tested. The two FMRFamide-like peptides, <EDPFLRFamide (<Glu-Asp-Pro-Phe-Leu-Arg-Phe-NH2), isolated from Helix heart, and AF1 (Lys-Asn-Glu-Phe-Ile-Arg-Phe-NH2), from Ascaris head, also showed hyperpolarizing effects on more than half of the number of Achatina neurone types. 5. SALMFamide 1 (Gly-Phe-Asn-Ser-Ala-Leu-Met-Phe-NH2), isolated from Asterias nervous system, CCAP (Pro-Phe-Cys-Asn-Ala-Phe-Thr-Gly-Cys-NH2), from Carcinus pericardial organ, and corazonin (<Glu-Thr-Phe-Gln-Tyr-Ser-Arg-Gly-Trp-Thr-Asn-NH2), from Periplaneta cardiac corpus, had no effect on Achatina neurones.

Amino Acid Sequence↗
PubMed1994

Mechanism of intraocular pressure decrease after contact transscleral continuous-wave Nd:YAG laser cyclophotocoagulation.

Twenty-two eyes of 11 cynomolgus monkeys were subjected to contact transscleral cyclophotocoagulation with a continuous-wave Nd:YAG laser. The right eye of each monkey was coagulated at the pars plicata region by the contact probe placed 1.0 mm from the limbus, while the left eye of each monkey was coagulated at the pars plana region by the contact probe placed 3.0 mm from the limbus. Physiological and morphological studies were carried out up to 6 months after the treatment. The postoperative intraocular pressure showed a significant decrease within 1 week, corresponding to the inflammation of the anterior chamber. A gradual increase of the intraocular pressure occurred from the 2nd week on and returned to the preoperative value 8 weeks after pars plicata coagulation. The pars plana coagulation group maintained the intraocular pressure lower than the preoperative value until the end of the observation period. Histopathological examinations were carried out by the use of tracer particle perfusion into the anterior chamber. The pathologic features of pars plicata coagulation were necrosis, followed by atrophy of the ciliary process. The tracer particles accumulated at the anterior portion of the space between the bundles of ciliary muscle. The pathologic features of pars plana coagulation were necrosis followed by extension of proliferative tissue into the vitreous. The surrounding extracellular space of the stroma was enlarged, and the ciliary muscles were separated from the sclera. The tracer particles accumulated at the enlarged extracellular space of the stroma and the opened suprachoroidal space. These results suggest that the decrease of the intraocular pressure after pars plicata cyclocoagulation resulted from the reduction of aqueous secretion, whereas that after pars plana cyclocoagulation resulted from enhancement of the uveoscleral outflow through the enlarged extracellular space from the anterior chamber into the suprachoroidal space.

Animals↗
PubMed1993

Modulation of neuropeptide effects by achatin-I, an Achatina endogenous tetrapeptide.

Achatin-I (Gly-D-Phe-L-Ala-L-Asp), an endogenous tetrapeptide in the ganglia of Achatina fulica Férussac, at 3 x 10(-6) M suppressed both the inward current (Iin) of an Achatina giant neurone, PON (periodically oscillating neurone), caused by locally ejected oxytocin, and the outward current (Iout) of v-RCDN (ventral-right cerebral distinct neurone) induced by APGW-amide. Dose (pressure duration)-response studies with oxytocin and APGW-amide showed that their ED50 values were not affected by achatin-I, whereas the Emax values were suppressed. The v-RCDN Iout caused by FMRF-amide was enhanced by achatin-I, but the same current induced by [Ser2]Mytilus inhibitory peptide ([Ser2]MIP) was not affected. Achatin-I suppressed the Iout of TAN (tonically autoactive neurone) caused by acetylcholine, but did not affect the Iin of v-RCDN elicited by acetylcholine. The Iout caused by gamma-aminobutyric acid, threo-beta-hydroxy-L-glutamic acid and dopamine was not affected by achatin-I. It is considered that achatin-I acts as a neuromodulator and has both suppressing and enhancing actions on the effects of various neurotransmitters, including peptides, in Achatina giant neurones.

Acetylcholine↗
PubMed1993

Modulatory effects of achatin-I, an Achatina endogenous neuroactive peptide, on responses to 5-hydroxytryptamine.

Achatin-I (Gly-D-Phe-L-Ala-L-Asp) was found in the ganglia of an African giant snail (Achatina fulica Férussac), and proposed as an excitatory neurotransmitter of Achatina neurones. At 3 x 10(-6) the peptide markedly enhanced the fast inward current (Iin) of an Achatina neurone type, TAN (tonically autoactive neurone), produced by the pneumatic pressure ejection of 5-HT. This Iin was facilitated immediately by the achatin-I perfusion, and the facilitation decreased gradually even with the peptide present. The dose (duration)-response curves of the TAN fast Iin on pressure ejection in the absence (control) and presence of achatin-I at 3 x 10(-6) M (n = 8) were analyzed as follows. The ED50 (95% confidence limit) were 59.3 ms (13.9-95.3 ms) for the control, and 36.5 ms (19.5-52.6 ms) for achatin-I. The Emax were 1.06 +/- 0.11 nA for the control, and 1.74 +/- 0.26 nA for achatin-I (P < 0.01 for paired data). Among achatin-I derivatives, achatin-II (Gly-L-Phe-L-Ala-L-Asp) enhanced the TAN fast response to 5-HT, but was ten times weaker than achatin-I. [L-Glu4]achatin-I (Gly-D-Phe-L-Ala-L-Glu) and achatin-I amide (Gly-D-Phe-Ala-L-Asp-NH2) had no facilitatory effect. We propose that achatin-I is a neuromodulator as well as a neurotransmitter for Achatina giant neurones.

Amino Acid Sequence↗
PubMed1993

AJ-2615, a long-acting Ca2+ channel antagonist with a novel structure.

AJ-2615, a dihydrodibenzothiepin derivative, at 10(-4) M inhibited the peak ICa amplitude of an identifiable Achatina neurone, PON (periodically oscillating neurone), by nearly a half of the control response 30 min after the start of perfusion (ED50: 0.96 x 10(-4) M). The ICa inhibition was still sustained 30 min after washout, indicating that AJ-2615 has long-lasting activity. The compound inhibited the ICa over a wide range of membrane potentials depolarized by the voltage pulse (Vd), but did not change the membrane potential required to produce the maximal ICa (Vd = 0 mV). The additional decrease in ICa amplitude caused by changing from low-frequency (1/5 min) depolarizing pulses to high-frequency (3/min) depolarizing pulses in the presence of AJ-2615 at 10(-4) M was 39.2 +/- 4.5% (mean+S.E.M.; n = 5), indicating use dependence. The steady state inactivation curves were measured in the presence or absence of AJ-2615 at 10(-4) M with a depolarizing prepulse (Vd = varied, duration = 30 s) followed by a depolarizing test pulse (Vd = +10 mV, duration 80 ms), with 2 ms intervals (n = 3): the ratio of AJ-2615 dissociation constant in the resting Ca2+ channel (Kr) and in the inactivated Ca2+ channel (Ki), Kr/Ki, was calculated to be 9.6:1, indicating voltage dependence.

Animals↗
PubMed1993

Anoxia/reoxygenation induces hydroxyl free radical formation in brain microvessels.

Isolated rat brain microvessels have been utilized to examine whether they produce hydroxyl free radicals if they are subjected to a 10- to 20-min anoxia period followed by a 40-min reoxygenation period. Hydroxyl free radical flux was assessed utilizing salicylate as a trap. The 2,3- and 2,5-dihydroxybenzoic acids (DHBA) products as well as salicylate in the microvessels were quantitated utilizing high-pressure liquid chromatography (HPLC) with electrochemical and fluorescence detection. The results show that a period of anoxia followed by reoxygenation resulted in an enhanced formation of DHBA compared to the normoxic control microvessels. Addition of superoxide dismutase (SOD) and catalase to the microvessels undergoing anoxia decreased the amount of hydroxyl free radicals trapped, suggesting that superoxide and hydrogen peroxide were produced and excreted from the endothelial cell surfaces and then unless quenched reentered the cells to form hydroxyl free radicals within. The amount of 2,5-DHBA formed closely correlated with the amount of 2,3-DHBA formed, indicating that either product can be used to assess hydroxyl free radical flux in brain microvessels.

Animals↗
PubMed1993

[Role of stratum corneum and its lipids in permeability of 5-fluorouracil through human skin].

The role of stratum corneum (SC) and its lipid constituents in skin permeability was assessed in vitro in diffusion system combined with the determination of partition coefficients (PC) and DSC technique. 5-Fu and 1,8-CN were used as the hydrophilic drug and penetration enhancer, respectively. The results showed that the PCs of 5-Fu were the same in SC, delipid SC, full skin and SC-stripped full skin, but the diffusion coefficients (D) of 5-Fu were different from each other. They were 1.32 +/- 0.37 x 10(-7), 13.71 +/- 5.12 x 10(-7), 1.01 +/- 0.31 x 10(-7) and 540.85 +/- 50.99 x 10(-7) cm2/h, respectively. When the skin membranes were pretreated with 1,8-CN for 12 h, the PCs were reduced to similar extent. However, the D was increased significantly in SC and in full skin, there was a small increase for delipid SC. No change was found in the D of stripped skin. DSC analysis indicated that 1,8-CN might change the thermal behaviour of SC lipid and the influence disappeared when SC was extracted with organic solvent. These results suggest that SC was the main barrier for 5-Fu diffusion through human skin, and the intercellular lipids played an important role for the hydrophilic drug penetration regardless of the presence of the enhancer in SC.

Calorimetry, Differential Scanning↗
PubMed1993

Sensitivities of Achatina giant neurones to peptides isolated from mollusca.

Sensitivities of the Achatina giant neurones to the peptides isolated from Mollusca were examined by their local application of the pneumatic pressure ejection under current clamp. The peptides tested and their effects were as follows: Ser2-MIP (inhibitory). CARP (inhibitory), oxytocin (excitatory), SPCB (excitatory), alpha-BCP (no effect). ELH (no effect). APGW-amide (inhibitory) and FMRFamide (inhibitory). Membrane conductance (g) of a neurone, d-RPeAN, measured under voltage clamp, was unexpectedly decreased by SCPB during inward current (Iin) caused by the peptide.

Animals↗
PubMed1993

Histopathological study of pseudophakic bullous keratopathy developing after anterior chamber of iris-supported intraocular lens implantation.

Sixty corneal buttons excised from patients who developed pseudophakic bullous keratopathy after anterior chamber or iris-supported intraocular lens implantation were studied morphologically and statistically. The mean age of patients was 72.5 +/- 11.6 years. The mean interval between intraocular lens implantation and keratoplasty was 5.1 +/- 2.2 years. Degeneration and conversion of endothelial cells, abnormal proliferation of posterior collagenous layer, and edema of stroma and epithelium were noticed morphologically. Twenty-nine of the 60 specimens showed a surviving endothelial cell area of less than 50%. In these specimens a significant increase in the thickness of the central stroma was recognized compared with the other 31 specimens. The number of keratocytes in the 29 specimens had decreased significantly compared with the control. A linear regression study showed a significant relationship between the thickness of the stroma and the number of keratocytes. The keratocyte density decreased predominantly in the posterior part of the stroma.

Adult↗
PubMed1993

[The bioavailability of transdermal therapeutic system of timolol].

A matrix-type transdermal therapeutic system of timolol (TTS-timolol) was well prepared. The patch consisted of backing membrane layer, timolol reservoir layer, pressure sensitive adhesive layer and protective layer. A sensitive and reliable HPLC-UV method for the determination of plasma level of timolol in healthy volunteers was developed. Effective therapeutic plasma level of timolol (4 ng/ml) was attained 4 h after application of the timolol patches and was maintained within 32 h while the patch was removed at 24 h. The pharmacokinetic behavior of this transdermal therapeutic system (TTS)-timolol in human showed zero order absorption and well fitted to a one compartment model. The pharmacokinetic parameters are: Tmax = 18.8 h; Cmax = 11.2 ng/ml; AUC = 265.7 ng/ml.h; Vss = 120.0 L; K = 0.084 h-1. In comparison with the results of oral administration of timolol tablets, TTS-timolol possesses some advantages: stable plasma level, long effective time and convenient administration.

Administration, Cutaneous↗
PubMed1992

Achatin-I, an excitatory neurotransmitter having a D-phenylalanine residue of Achatina giant neurones.

The neuroexcitatory peptide isolated from Achatina ganglia was identical to the synthetic Gly-D-Phe-L-Ala-L-Asp with respect to either the bioassay experiments using the Achatina neurones or the instrumental analysis (1H-NMR, SIMS, CD and HPLC). We termed it achatin-I (yield: 50 micrograms from 30,000 animals). Its stereoisomer, Gly-L-Phe-L-Ala-L-Asp, termed achatin-II, was also isolated from the ganglia (yield: 17 micrograms), but this was ineffective on the Achatina neurones. Of the eight possible stereoisomers, only achatin-I markedly showed excitatory effects on the two Achatina neurones, PON and TAN, and [D-Ala3] achatin-I (Gly-D-Phe-D-Ala-L-Asp) had the slight effects. Among the fourteen neurones tested, seven, including the two mentioned above, were excited by achatin-I, whereas no neurone was inhibited. Achatin-I produced an inward current (Iin) with an increase in the membrane conductance (g) under voltage clamp. ED50 of achatin-I for exciting the neurones were 0.20-1.47 x 10(-5) M, and its Emax were 6.33-5.02 nA. Of the achatin-I analogues examined, only the three, Gly-Gly-D-Phe-L-Ala-L-Asp, D-Phe-L-Ala-L-Asp and Gly-D-Phe-L-Ala-L-Asn, produced Iin, but much smaller than that of achatin-I. The equiactive molar ratios (EMRs) of the four effective related peptides (three analogues and a stereoisomer) vs. achatin-I were: 8-60 for Gly-Gly-D-Phe-L-Ala-L-Asp, 200 - > 250 for D-Phe-L-Ala-L-Asp and > 200 for Gly-D-Phe-L-Ala-L-Asn and Gly-D-Phe-D-Ala-L-Asp. The Iin induced by achatin-I was blocked under the /Na+/0-free state, but unaffected under the [Ca2+]-free (replaced with Co2+), [Cl-]0-free or [K+]-enriched (3.0 x) medium, indicating that the Iin is produced by the gNa increase of neuromembrane. We propose that achatin-I having a D-phenylalanine residue is an excitatory neurotransmitter of the Achatina neurones.

Action Potentials↗
PubMed1991

APGW-amide as an inhibitory neurotransmitter of Achatina fulica Ferussac.

APGWamide (L-Ala-L-Pro-Gly-L-Trp-NH2) was purified from the ganglia of an African giant snail (Achatina fulica Ferussac). This peptide inhibited (hyperpolarized) more than half of the Achatina neurone types tested. This produced an outward current with the membrane conductance increase of RAPN (right anterior pallial neurone) under voltage clamp. The ED50 of the peptide was 6.2 x 10(-6) M (95% confidence limit: 5.0-7.8 x 10(-6) M) and the Emax was 3.9 +/- 0.2 nA. The effects were due to a membrane permeability increase to K+. The peptide is proposed as an inhibitory neurotransmitter of the Achatina neurones.

Animals↗
PubMed1991

Comparative histopathological study of free-running mode and continuous wave Nd:YAG laser photocoagulation of monkey retina and choroid.

The effects of free-running mode (FRM) or continuous wave (CW) Nd:YAG laser application on the retina and choroid of 12 monkeys were examined periodically up to 24 months by light and electron microscopes. FRM Nd:YAG laser produced severe choroidal hemorrhage even in mild burns, because of the extensive coagulation of melanocytes at the center of the burned lesion. The rupture of Bruch's membrane did not depend on the power of the laser. On the other hand, CW Nd:YAG laser rarely produced subretinal hemorrhage through the rupture of Bruch's membrane in the medium-grade and severe burns. However, choroidal hemorrhage was seen histologically even in mild CW burned lesions. In the healing stage of mild FRM burned lesions the retinal pigment epithelium (RPE) and choroidal fibroblasts showed different repair processes. FRM medium-grade burned lesions showed the proliferation of Müller cells, while CW burns showed the regeneration and proliferation of RPE, Müller cells and fibroblasts. Because of the difference in the repair processes evoked by these two modes of laser application, these findings suggest that CW Nd:YAG laser is preferable for the treatment of subretinal and choroidal disorders.

Animals↗